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TOP242-250
®
TOPSwitch-GX Family
Product Highlights
Lower System Cost, High Design Flexibility · Extended power range for higher power applications · No heatsink required up to 34 W using P/G packages · Features eliminate or reduce cost of external components · Fully integrated soft-start for minimum stress/overshoot · Externally programmable accurate current limit · Wider duty cycle for more power, smaller input capacitor · Separate line sense and current limit pins on Y/R/F packages · Line under-voltage (UV) detection: no turn off glitches · Line overvoltage (OV) shutdown extends line surge limit · Line feed-forward with maximum duty cycle (DCMAX) reduction rejects line ripple and limits DCMAX at high line · Frequency jittering reduces EMI and EMI filtering costs · Regulates to zero load without dummy loading · 132 kHz frequency reduces transformer/power supply size · Half frequency option in Y/R/F packages for video applications · Hysteretic thermal shutdown for automatic fault recovery · Large thermal hysteresis prevents PC board overheating EcoSmart Energy Efficient · Extremely low consumption in remote off mode (80 mW at 110 VAC, 160 mW at 230 VAC) · Frequency lowered with load for high standby efficiency · Allows shutdown/wake-up via LAN/input port
Extended Power, Design Flexible, ® EcoSmart, Integrated Off-line Switcher
AC IN
+ DC OUT -
D
L
CONTROL
TOPSwitch-GX
S
C
X
F
PI-2632-060200
Figure 1. Typical Flyback Application.
OUTPUT POWER TABLE
PRODUCT3 230 VAC ±15%4 Adapter1
85-265 VAC
Description
TOPSwitch-GX uses the same proven topology as TOPSwitch, cost effectively integrating the high voltage power MOSFET, PWM control, fault protection and other control circuitry onto a single CMOS chip. Many new functions are integrated to reduce system cost and improve design flexibility, performance and energy efficiency. Depending on package type, either 1 or 3 additional pins over the TOPSwitch standard DRAIN, SOURCE and CONTROL terminals allow the following functions: line sensing (OV/UV, line feed-forward/DCMAX reduction), accurate externally set current limit, remote ON/OFF, synchronization to an external lower frequency, and frequency selection (132 kHz/66 kHz). All package types provide the following transparent features: Soft-start, 132 kHz switching frequency (automatically reduced at light load), frequency jittering for lower EMI, wider DCMAX, hysteretic thermal shutdown, and larger creepage packages. In addition, all critical parameters (i.e. current limit, frequency, PWM gain) have tighter temperature and absolute tolerances to simplify design and optimize system cost.
TOP242 P or G 9 W TOP242 R 15 W TOP242 Y or F 10 W TOP243 P or G 13 W TOP243 R 29 W TOP243 Y or F 20 W TOP244 P or G 16 W TOP244 R 34 W TOP244 Y or F 30 W TOP245 P or G 19 W TOP245 R 37 W TOP245 Y or F 40 W TOP246 P or G 21 W TOP246 R 40 W TOP246 Y or F 60 W 42 W TOP247 R TOP247 Y or F 85 W 43 W TOP248 R TOP248 Y or F 105 W 44 W TOP249 R TOP249 Y or F 120 W 45 W TOP250 R TOP250 Y or F 135 W
Open Open Adapter1 Frame2 Frame2 15 W 6.5 W 10 W 22 W 11 W 14 W 22 W 7W 14 W 25 W 9W 15 W 45 W 17 W 23 W 45 W 15 W 30 W 28 W 20 W 11 W 50 W 20 W 28 W 65 W 20 W 45 W 30 W 13 W 22 W 57 W 23 W 33 W 85 W 26 W 60 W 34 W 15 W 26 W 64 W 26 W 38 W 125 W 40 W 90 W 70 W 28 W 43 W 165 W 55 W 125 W 75 W 30 W 48 W 205 W 70 W 155 W 79 W 31 W 53 W 250 W 80 W 180 W 82 W 32 W 55 W 290 W 90 W 210 W
Table 1. Notes: 1. Typical continuous power in a non-ventilated enclosed adapter measured at 50 °C ambient. 2. Maximum practical continuous power in an open frame design at 50 °C ambient. See Key Applications for detailed conditions. 3. For lead-free package options, see Part Ordering Information. 4. 230 VAC or 100/115 VAC with doubler.
November 2005
TOP242-250
Section List
Functional Block Diagram ....................................................................................................................................... 3 Pin Functional Description ...................................................................................................................................... 4 TOPSwitch-GX Family Functional Description ....................................................................................................... 5 CONTROL (C) Pin Operation.................................................................................................................................. 6 Oscillator and Switching Frequency ........................................................................................................................ 6 Pulse Width Modulator and Maximum Duty Cycle .................................................................................................. 7 Light Load Frequency Reduction ............................................................................................................................ 7 Error Amplifier ......................................................................................................................................................... 7 On-Chip Current Limit with External Programmability ............................................................................................ 7 Line Under-Voltage Detection (UV)......................................................................................................................... 8 Line Overvoltage Shutdown (OV) ........................................................................................................................... 8 Line Feed-Forward with DCMAX Reduction .............................................................................................................. 8 Remote ON/OFF and Synchronization ................................................................................................................... 9 Soft-Start ................................................................................................................................................................. 9 Shutdown/Auto-Restart ........................................................................................................................................... 9 Hysteretic Over-Temperature Protection ................................................................................................................. 9 Bandgap Reference .............................................................................................................................................. 10 High-Voltage Bias Current Source ........................................................................................................................ 10 Using Feature Pins ................................................................................................................................................... 10 FREQUENCY (F) Pin Operation ........................................................................................................................... 10 LINE-SENSE (L) Pin Operation ............................................................................................................................ 10 EXTERNAL CURRENT LIMIT (X) Pin Operation .................................................................................................. 11 MULTI-FUNCTION (M) Pin Operation .................................................................................................................. 11 Typical Uses of FREQUENCY (F) Pin ...................................................................................................................... 14 Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins ...................................................... 15 Typical Uses of MULTI-FUNCTION (M) Pin ........................................................................................................... 17 Application Examples .............................................................................................................................................. 20 A High Efficiency, 30 W, Universal Input Power Supply ........................................................................................ 20 A High Efficiency, Enclosed, 70 W, Universal Adapter Supply .............................................................................. 20 A High Efficiency, 250 W, 250-380 VDC Input Power Supply ............................................................................... 22 Multiple Output, 60 W, 185-265 VAC Input Power Supply .................................................................................... 23 Processor Controlled Supply Turn On/Off ............................................................................................................. 24 Key Application Considerations ............................................................................................................................. 26 TOPSwitch-II vs. TOPSwitch-GX .......................................................................................................................... 26 TOPSwitch-FX vs. TOPSwitch-GX ....................................................................................................................... 28 TOPSwitch-GX Design Considerations ............................................................................................................... 28 TOPSwitch-GX Layout Considerations ................................................................................................................. 30 Quick Design Checklist ......................................................................................................................................... 32 Design Tools ......................................................................................................................................................... 32 Product Specifications and Test Conditions ......................................................................................................... 33 Typical Performance Characteristics .................................................................................................................... 40 Part Ordering Information ....................................................................................................................................... 46 Package Outlines ..................................................................................................................................................... 47
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TOP242-250
VC
CONTROL (C)
0
DRAIN (D)
INTERNAL SUPPLY
ZC
1
SHUNT REGULATOR/ ERROR AMPLIFIER
+
+
5.8 V 4.8 V
-
SOFT START
5.8 V
IFB
INTERNAL UV COMPARATOR
CURRENT LIMIT ADJUST
VI (LIMIT)
SOFT START ON/OFF
÷8
SHUTDOWN/ AUTO-RESTART
+
VBG + VT
EXTERNAL CURRENT LIMIT (X)
STOP LOGIC
CURRENT LIMIT COMPARATOR
LINE-SENSE (L)
1V
HYSTERETIC THERMAL SHUTDOWN
VBG
OV/UV
LINE SENSE
DCMAX
STOP SOFTSTART DMAX DCMAX CLOCK
HALF FREQ. SAW
+
S R Q
CONTROLLED TURN-ON GATE DRIVER
FREQUENCY (F)
OSCILLATOR WITH JITTER
LEADING EDGE BLANKING
PWM COMPARATOR
RE
LIGHT LOAD FREQUENCY REDUCTION
SOURCE (S)
PI-2639-060600
Figure 2a. Functional Block Diagram (Y, R or F Package).
VC
CONTROL (C)
0
ZC
1
DRAIN (D)
INTERNAL SUPPLY
SHUNT REGULATOR/ ERROR AMPLIFIER
+
5.8 V 4.8 V
+
-
SOFT START
5.8 V
IFB
VI (LIMIT)
INTERNAL UV COMPARATOR
CURRENT LIMIT ADJUST
SOFT START ON/OFF
÷8
SHUTDOWN/ AUTO-RESTART
STOP LOGIC
+
VBG + VT
CURRENT LIMIT COMPARATOR
MULTIFUNCTION (M)
VBG
OV/UV
HYSTERETIC THERMAL SHUTDOWN
LINE SENSE
DCMAX
STOP SOFTSTART DMAX DCMAX CLOCK
CONTROLLED TURN-ON GATE DRIVER
SAW
+
S R
Q
OSCILLATOR WITH JITTER
LEADING EDGE BLANKING
PWM COMPARATOR
RE
LIGHT LOAD FREQUENCY REDUCTION
SOURCE (S)
PI-2641-061200
Figure 2b. Functional Block Diagram (P or G Package).
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TOP242-250
Pin Functional Description
DRAIN (D) Pin: High voltage power MOSFET drain output. The internal start-up bias current is drawn from this pin through a switched high-voltage current source. Internal current limit sense point for drain current. CONTROL (C) Pin: Error amplifier and feedback current input pin for duty cycle control. Internal shunt regulator connection to provide internal bias current during normal operation. It is also used as the connection point for the supply bypass and auto-restart/ compensation capacitor. LINE-SENSE (L) Pin: (Y, R or F package only) Input pin for OV, UV, line feed forward with DCMAX reduction, remote ON/OFF and synchronization. A connection to SOURCE pin disables all functions on this pin. EXTERNAL CURRENT LIMIT (X) Pin: (Y, R or F package only) Input pin for external current limit adjustment, remote ON/OFF, and synchronization. A connection to SOURCE pin disables all functions on this pin. MULTI-FUNCTION (M) Pin: (P or G package only) This pin combines the functions of the LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) pins of the Y package into one pin. Input pin for OV, UV, line feed forward with DCMAX reduction, external current limit adjustment, remote ON/OFF and synchronization. A connection to SOURCE pin disables all functions on this pin and makes TOPSwitch-GX operate in simple three terminal mode (like TOPSwitch-II). Y Package (TO-220-7C)
Tab Internally Connected to SOURCE Pin 7D 5F 4S 3X 2L 1C
FREQUENCY (F) Pin: (Y, R or F package only) Input pin for selecting switching frequency: 132 kHz if connected to SOURCE pin and 66 kHz if connected to CONTROL pin. The switching frequency is internally set for fixed 132 kHz operation in P and G packages. SOURCE (S) Pin: Output MOSFET source connection for high voltage power return. Primary side control circuit common and reference point. +
RLS 2 M
VUV = IUV x RLS VOV = IOV x RLS For RLS = 2 M VUV = 100 VDC VOV = 450 VDC DCMAX@100 VDC = 78% DCMAX@375 VDC = 38%
C
DC Input Voltage
D
L
CONTROL
S
X RIL 12 k
For RIL = 12 k ILIMIT = 69% See Figure 54b for other resistor values (RIL) to select different ILIMIT values
-
Figure 4. Y/R/F Pkg Line Sense and Externally Set Current Limit.
+
VUV = IUV x RLS VOV = IOV x RLS
RLS 2 M
DC Input Voltage
For RLS = 2 M VUV = 100 VDC VOV = 450 VDC DCMAX@100 VDC = 78% DCMAX@375 VDC = 38%
C
D
M
CONTROL
-
S
PI-2509-040501
Figure 5. P/G Package Line Sense.
P Package (DIP-8B) G Package (SMD-8B)
M S S C
R Package (TO-263-7C) F Package (TO-262-7C)
+
For RIL = 12 k ILIMIT = 69% For RIL = 25 k ILIMIT = 43% See Figures 54b, 55b and 56b for other resistor values (RIL) to select different ILIMIT values.
C
1 2 3 4
8 7
S S
DC Input Voltage
RIL
D
M
CONTROL
5
D
123 4 5 CL X S F
7 D
PI-2724-010802
-
S
PI-2517-022604
Figure 3. Pin Configuration (top view). Figure 6. P/G Package Externally Set Current Limit.
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PI-2629-092203
TOP242-250
TOPSwitch-GX Family Functional Description
Frequency (kHz)
Auto-restart ICD1 132
IB
IL = 125 µA
Like TOPSwitch, TOPSwitch-GX is an integrated switched mode power supply chip that converts a current at the control input to a duty cycle at the open drain output of a high voltage power MOSFET. During normal operation the duty cycle of the power MOSFET decreases linearly with increasing CONTROL pin current as shown in Figure 7. In addition to the three terminal TOPSwitch features, such as the high voltage start-up, the cycle-by-cycle current limiting, loop compensation circuitry, auto-restart, thermal shutdown, the TOPSwitch-GX incorporates many additional functions that reduce system cost, increase power supply performance and design flexibility. A patented high voltage CMOS technology allows both the high voltage power MOSFET and all the low voltage control circuitry to be cost effectively integrated onto a single monolithic chip. Three terminals, FREQUENCY, LINE-SENSE, and EXTERNAL CURRENT LIMIT (available in Y, R or F package) or one terminal MULTI-FUNCTION (available in P or G package) have been added to implement some of the new functions. These terminals can be connected to the SOURCE pin to operate the TOPSwitch-GX in a TOPSwitch-like three terminal mode. However, even in this three terminal mode, the TOPSwitch-GX offers many new transparent features that do not require any external components: 1. A fully integrated 10 ms soft-start limits peak currents and voltages during start-up and dramatically reduces or eliminates output overshoot in most applications. 2. DCMAX of 78% allows smaller input storage capacitor, lower input voltage requirement and/or higher power capability. 3. Frequency reduction at light loads lowers the switching losses and maintains good cross regulation in multiple output supplies. 4. Higher switching frequency of 132 kHz reduces the transformer size with no noticeable impact on EMI. 5. Frequency jittering reduces EMI. 6. Hysteretic over-temperature shutdown ensures automatic recovery from thermal fault. Large hysteresis prevents circuit board overheating. 7. Packages with omitted pins and lead forming provide large drain creepage distance. 8. Tighter absolute tolerances and smaller temperature variations on switching frequency, current limit and PWM gain. The LINE-SENSE (L) pin is usually used for line sensing by connecting a resistor from this pin to the rectified DC high voltage bus to implement line overvoltage (OV), under-voltage (UV) and line feed-forward with DCMAX reduction. In this mode, the value of the resistor determines the OV/UV thresholds and the DCMAX is reduced linearly starting from a line voltage above the under-voltage threshold. See Table 2 and Figure 11.
IL = 190 µA
IL < IL(DC)
30
IC (mA) Auto-restart ICD1 78 Duty Cycle (%)
IB
Slope = PWM Gain
38
IL = 125 µA IL < IL(DC)
10
IL = 190 µA
TOP242-5 1.6 2.0 TOP246-9 2.2 2.6 TOP250 2.4 2.7
IC (mA)
5.2 5.8 6.5
6.0 6.6 7.3
Note: For P and G packages IL is replaced with IM.
PI-2633-011502
Figure 7. Relationship of Duty Cycle and Frequency to CONTROL Pin Current.
The pin can also be used as a remote ON/OFF and a synchronization input. The EXTERNAL CURRENT LIMIT (X) pin is usually used to reduce the current limit externally to a value close to the operating peak current, by connecting the pin to SOURCE through a resistor. This pin can also be used as a remote ON/OFF and a synchronization input in both modes. See Table 2 and Figure 11. For the P or G packages the LINE-SENSE and EXTERNAL CURRENT LIMIT pin functions are combined on one MULTIFUNCTION (M) pin. However, some of the functions become mutually exclusive as shown in Table 3. The FREQUENCY (F) pin in the Y, R or F package sets the switching frequency to the default value of 132 kHz when connected to SOURCE pin. A half frequency option of 66 kHz can be chosen by connecting this pin to CONTROL pin instead. Leaving this pin open is not recommended.
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CONTROL (C) Pin Operation The CONTROL pin is a low impedance node that is capable of receiving a combined supply and feedback current. During normal operation, a shunt regulator is used to separate the feedback signal from the supply current. CONTROL pin voltage VC is the supply voltage for the control circuitry including the MOSFET gate driver. An external bypass capacitor closely connected between the CONTROL and SOURCE pins is required to supply the instantaneous gate drive current. The total amount of capacitance connected to this pin also sets the auto-restart timing as well as control loop compensation. When rectified DC high voltage is applied to the DRAIN pin during start-up, the MOSFET is initially off, and the CONTROL pin capacitor is charged through a switched high voltage current source connected internally between the DRAIN and CONTROL pins. When the CONTROL pin voltage VC reaches approximately 5.8 V, the control circuitry is activated and the soft-start begins. The soft-start circuit gradually increases the duty cycle of the MOSFET from zero to the maximum value over approximately 10 ms. If no external feedback/supply current is fed into the CONTROL pin by the end of the soft-start, the high voltage current source is turned off and the CONTROL pin will start discharging in response to the supply current drawn by the control circuitry. If the power supply is designed properly, and no fault condition such as open loop or shorted output exists, the feedback loop will close, providing external CONTROL pin current, before the CONTROL pin voltage has had a chance to discharge to the lower threshold voltage of approximately 4.8 V (internal supply under-voltage lockout threshold). When the externally fed current charges the CONTROL pin to the shunt regulator voltage of 5.8 V, current in excess of the consumption of the chip is shunted to SOURCE through resistor RE as shown in Figure 2. This current flowing through RE controls the duty cycle of the power MOSFET to provide closed loop regulation. The shunt regulator has a finite low output impedance ZC that sets the gain of the error amplifier when used in a primary feedback configuration. The dynamic impedance ZC of the CONTROL pin together with the external CONTROL pin capacitance sets the dominant pole for the control loop. When a fault condition such as an open loop or shorted output prevents the flow of an external current into the CONTROL pin, the capacitor on the CONTROL pin discharges towards 4.8 V. At 4.8 V, auto-restart is activated which turns the output MOSFET off and puts the control circuitry in a low current standby mode. The high-voltage current source turns on and charges the external capacitance again. A hysteretic internal supply under-voltage comparator keeps VC within a window of typically 4.8 V to 5.8 V by turning the high-voltage current source on and off as shown in Figure 8. The auto-restart circuit has a divide-by-eight counter which prevents the output MOSFET from turning on again until eight discharge/charge cycles have elapsed. This is accomplished by enabling the output MOSFET only when the divide-by-eight counter reaches full count (S7). The counter effectively limits TOPSwitch-GX power dissipation by reducing the auto-restart duty cycle to typically 4%. Auto-restart mode continues until output voltage regulation is again achieved through closure of the feedback loop. Oscillator and Switching Frequency The internal oscillator linearly charges and discharges an
~ ~
~ ~
VUV VLINE
0V
S7 S0 S1 S2 S6 S7 S0 S1 S2 S6 S7 S0 S1 S2 S6 S7 S7
~ ~
~ ~
~ ~ ~ ~
VC
0V
5.8 V 4.8 V
~ ~
~ ~
~ ~
~ ~
VDRAIN
0V
~ ~
VOUT
0V
~ ~
~ ~
~ ~
1
2
3
2
4
PI-2545-082299
Note: S0 through S7 are the output states of the auto-restart counter
Figure 8. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-Restart (4) Power Down.
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TOP242-250
internal capacitance between two voltage levels to create a sawtooth waveform for the pulse width modulator. This oscillator sets the pulse width modulator/current limit latch at the beginning of each cycle. The nominal switching frequency of 132 kHz was chosen to minimize transformer size while keeping the fundamental EMI frequency below 150 kHz. The FREQUENCY pin (available only in Y, R or F package), when shorted to the CONTROL pin, lowers the switching frequency to 66 kHz (half frequency) which may be preferable in some cases such as noise sensitive video applications or a high efficiency standby mode. Otherwise, the FREQUENCY pin should be connected to the SOURCE pin for the default 132 kHz. To further reduce the EMI level, the switching frequency is jittered (frequency modulated) by approximately ±4 kHz at 250 Hz (typical) rate as shown in Figure 9. Figure 46 shows the typical improvement of EMI measurements with frequency jitter. Pulse Width Modulator and Maximum Duty Cycle The pulse width modulator implements voltage mode control by driving the output MOSFET with a duty cycle inversely proportional to the current into the CONTROL pin that is in excess of the internal supply current of the chip (see Figure 7). The excess current is the feedback error signal that appears across RE (see Figure 2). This signal is filtered by an RC network with a typical corner frequency of 7 kHz to reduce the effect of switching noise in the chip supply current generated by the MOSFET gate driver. The filtered error signal is compared with the internal oscillator sawtooth waveform to generate the duty cycle waveform. As the control current increases, the duty cycle decreases. A clock signal from the oscillator sets a latch which turns on the output MOSFET. The pulse width modulator resets the latch, turning off the output MOSFET. Note that a minimum current must be driven into the CONTROL pin before the duty cycle begins to change. The maximum duty cycle, DCMAX, is set at a default maximum value of 78% (typical). However, by connecting the LINESENSE or MULTI-FUNCTION pin (depending on the package) to the rectified DC high voltage bus through a resistor with appropriate value, the maximum duty cycle can be made to decrease from 78% to 38% (typical) as shown in Figure 11 when input line voltage increases (see line feed forward with DCMAX reduction). Light Load Frequency Reduction The pulse width modulator duty cycle reduces as the load at the power supply output decreases. This reduction in duty cycle is proportional to the current flowing into the CONTROL pin. As the CONTROL pin current increases, the duty cycle decreases linearly towards a duty cycle of 10%. Below 10% duty cycle, to maintain high efficiency at light loads, the
136 kHz
Switching Frequency
PI-2550-092499
128 kHz 4 ms
VDRAIN
Time
Figure 9. Switching Frequency Jitter (Idealized VDRAIN Waveforms).
frequency is also reduced linearly until a minimum frequency is reached at a duty cycle of 0% (refer to Figure 7). The minimum frequency is typically 30 kHz and 15 kHz for 132 kHz and 66 kHz operation, respectively. This feature allows a power supply to operate at lower frequency at light loads thus lowering the switching losses while maintaining good cross regulation performance and low output ripple. Error Amplifier The shunt regulator can also perform the function of an error amplifier in primary side feedback applications. The shunt regulator voltage is accurately derived from a temperaturecompensated bandgap reference. The gain of the error amplifier is set by the CONTROL pin dynamic impedance. The CONTROL pin clamps external circuit signals to the VC voltage level. The CONTROL pin current in excess of the supply current is separated by the shunt regulator and flows through RE as a voltage error signal. On-Chip Current Limit with External Programmability The cycle-by-cycle peak drain current limit circuit uses the output MOSFET ON-resistance as a sense resistor. A current limit comparator compares the output MOSFET on-state drain to source voltage, VDS(ON) with a threshold voltage. High drain current causes VDS(ON) to exceed the threshold voltage and turns the output MOSFET off until the start of the next clock cycle. The current limit comparator threshold voltage is temperature compensated to minimize the variation of the current limit due to temperature related changes in RDS(ON)of the output MOSFET. The default current limit of TOPSwitch-GX is preset internally. However, with a resistor connected between EXTERNAL CURRENT LIMIT (X) pin (Y, R or F package) or MULTIFUNCTION (M) pin (P or G package) and SOURCE pin, current limit can be programmed externally to a lower level between 30% and 100% of the default current limit. Please refer to the graphs in the typical performance characteristics section for the selection of the resistor value. By setting current limit low, a larger TOPSwitch-GX than necessary for the power
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TOP242-250
required can be used to take advantage of the lower RDS(ON) for higher efficiency/smaller heat sinking requirements. With a second resistor connected between the EXTERNAL CURRENT LIMIT (X) pin (Y, R or F package) or MULTIFUNCTION (M) pin (P or G package) and the rectified DC high voltage bus, the current limit is reduced with increasing line voltage, allowing a true power limiting operation against line variation to be implemented. When using an RCD clamp, this power limiting technique reduces maximum clamp voltage at high line. This allows for higher reflected voltage designs as well as reducing clamp dissipation. The leading edge blanking circuit inhibits the current limit comparator for a short time after the output MOSFET is turned on. The leading edge blanking time has been set so that, if a power supply is designed properly, current spikes caused by primary-side capacitances and secondary-side rectifier reverse recovery time should not cause premature termination of the switching pulse. The current limit is lower for a short period after the leading edge blanking time as shown in Figure 52. This is due to dynamic characteristics of the MOSFET. To avoid triggering the current limit in normal operation, the drain current waveform should stay within the envelope shown. Line Under-Voltage Detection (UV) At power up, UV keeps TOPSwitch-GX off until the input line voltage reaches the under-voltage threshold. At power down, UV prevents auto-restart attempts after the output goes out of regulation. This eliminates power down glitches caused by slow discharge of the large input storage capacitor present in applications such as standby supplies. A single resistor connected from the LINE-SENSE pin (Y, R or F package) or MULTI-FUNCTION pin (P or G package) to the rectified DC high voltage bus sets UV threshold during power up. Once the power supply is successfully turned on, the UV threshold is lowered to 40% of the initial UV threshold to allow extended input voltage operating range (UV low threshold). If the UV low threshold is reached during operation without the power supply losing regulation, the device will turn off and stay off until UV (high threshold) has been reached again. If the power supply loses regulation before reaching the UV low threshold, the device will enter auto-restart. At the end of each autorestart cycle (S7), the UV comparator is enabled. If the UV high threshold is not exceeded the MOSFET will be disabled during the next cycle (see Figure 8). The UV feature can be disabled independent of the OV feature as shown in Figures 19 and 23. Line Overvoltage Shutdown (OV) The same resistor used for UV also sets an overvoltage threshold which, once exceeded, will force TOPSwitch-GX output into off-state. The ratio of OV and UV thresholds is preset at 4.5 as can be seen in Figure 11. When the MOSFET is off, the rectified DC high voltage surge capability is increased to the voltage rating of the MOSFET (700 V), due to the absence of the reflected voltage and leakage spikes on the drain. A small amount of hysteresis is provided on the OV threshold to prevent noise triggering. The OV feature can be disabled independent of the UV feature as shown in Figures 18 and 32. Line Feed-Forward with DCMAX Reduction The same resistor used for UV and OV also implements line voltage feed-forward, which minimizes output line ripple and reduces power supply output sensitivity to line transients. This feed-forward operation is illustrated in Figure 7 by the different values of IL (Y, R or F package) or IM (P or G package). Note that for the same CONTROL pin current, higher line voltage results in smaller operating duty cycle. As an added
Oscillator (SAW)
DMAX
Enable from X, L or M Pin (STOP) Time
PI-2637-060600
Figure 10. Synchronization Timing Diagram.
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TOP242-250
feature, the maximum duty cycle DCMAX is also reduced from 78% (typical) at a voltage slightly higher than the UV threshold to 30% (typical) at the OV threshold (see Figure 11). Limiting DCMAX at higher line voltages helps prevent transformer saturation due to large load transients in TOP248, TOP249 and TOP250 forward converter applications. DCMAX of 38% at high line was chosen to ensure that the power capability of the TOPSwitch-GX is not restricted by this feature under normal operation. Remote ON/OFF and Synchronization TOPSwitch-GX can be turned on or off by controlling the current into the LINE-SENSE pin or out from the EXTERNAL CURRENT LIMIT pin (Y, R or F package) and into or out from the MULTI-FUNCTION pin (P or G package) (see Figure 11). In addition, the LINE-SENSE pin has a 1 V threshold comparator connected at its input. This voltage threshold can also be used to perform remote ON/OFF control. This allows easy implementation of remote ON/OFF control of TOPSwitch-GX in several different ways. A transistor or an optocoupler output connected between the EXTERNAL CURRENT LIMIT or LINE-SENSE pins (Y, R or F package) or the MULTI-FUNCTION pin (P or G package) and the SOURCE pin implements this function with "active-on" (Figures 22, 29 and 36) while a transistor or an optocoupler output connected between the LINE-SENSE pin (Y, R or F package) or the MULTI-FUNCTION (P or G package) pin and the CONTROL pin implements the function with "active-off" (Figures 23 and 37). When a signal is received at the LINE-SENSE pin or the EXTERNAL CURRENT LIMIT pin (Y, R or F package) or the MULTI-FUNCTION pin (P or G package) to disable the output through any of the pin functions such as OV, UV and remote ON/OFF, TOPSwitch-GX always completes its current switching cycle, as illustrated in Figure 10, before the output is forced off. The internal oscillator is stopped slightly before the end of the current cycle and stays there as long as the disable signal exists. When the signal at the above pins changes state from disable to enable, the internal oscillator starts the next switching cycle. This approach allows the use of these pins to synchronize TOPSwitch-GX to any external signal with a frequency between its internal switching frequency and 20 kHz. As seen above, the remote ON/OFF feature allows the TOPSwitch-GX to be turned on and off instantly, on a cycleby-cycle basis, with very little delay. However, remote ON/OFF can also be used as a standby or power switch to turn off the TOPSwitch-GX and keep it in a very low power consumption state for indefinitely long periods. If the TOPSwitch-GX is held in remote off state for long enough time to allow the CONTROL pin to discharge to the internal supply under-voltage threshold of 4.8 V (approximately 32 ms for a 47 µF CONTROL pin capacitance), the CONTROL pin goes into the hysteretic mode of regulation. In this mode, the CONTROL pin goes through alternate charge and discharge cycles between 4.8 V and 5.8 V (see CONTROL pin operation section above) and runs entirely off the high voltage DC input, but with very low power consumption (160 mW typical at 230 VAC with M or X pins open). When the TOPSwitch-GX is remotely turned on after entering this mode, it will initiate a normal start-up sequence with soft-start the next time the CONTROL pin reaches 5.8 V. In the worst case, the delay from remote on to start-up can be equal to the full discharge/charge cycle time of the CONTROL pin, which is approximately 125 ms for a 47 µF CONTROL pin capacitor. This reduced consumption remote off mode can eliminate expensive and unreliable in-line mechanical switches. It also allows for microprocessor controlled turn-on and turn-off sequences that may be required in certain applications such as inkjet and laser printers. Soft-Start Two on-chip soft-start functions are activated at start-up with a duration of 10 ms (typical). Maximum duty cycle starts from 0% and linearly increases to the default maximum of 78% at the end of the 10 ms duration and the current limit starts from about 85% and linearly increases to 100% at the end of the 10 ms duration. In addition to start-up, soft-start is also activated at each restart attempt during auto-restart and when restarting after being in hysteretic regulation of CONTROL pin voltage (VC), due to remote OFF or thermal shutdown conditions. This effectively minimizes current and voltage stresses on the output MOSFET, the clamp circuit and the output rectifier during start-up. This feature also helps minimize output overshoot and prevents saturation of the transformer during start-up. Shutdown/Auto-Restart To minimize TOPSwitch-GX power dissipation under fault conditions, the shutdown/auto-restart circuit turns the power supply on and off at an auto-restart duty cycle of typically 4% if an out of regulation condition persists. Loss of regulation interrupts the external current into the CONTROL pin. VC regulation changes from shunt mode to the hysteretic autorestart mode as described in CONTROL pin operation section. When the fault condition is removed, the power supply output becomes regulated, VC regulation returns to shunt mode, and normal operation of the power supply resumes. Hysteretic Over-Temperature Protection Temperature protection is provided by a precision analog circuit that turns the output MOSFET off when the junction temperature exceeds the thermal shutdown temperature (140 °C typical). When the junction temperature cools to below the hysteretic temperature, normal operation resumes providing automatic recovery. A large hysteresis of 70 °C (typical) is provided to prevent overheating of the PC board due to a continuous fault condition. VC is regulated in hysteretic mode and a 4.8 V to 5.8 V (typical) sawtooth waveform is present on the CONTROL pin while in thermal shutdown.
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Bandgap Reference All critical TOPSwitch-GX internal voltages are derived from a temperature-compensated bandgap reference. This reference is also used to generate a temperature-compensated current reference, which is trimmed to accurately set the switching frequency, MOSFET gate drive current, current limit, and the line OV/UV thresholds. TOPSwitch-GX has improved circuitry to maintain all of the above critical parameters within very tight absolute and temperature tolerances. High-Voltage Bias Current Source This current source biases TOPSwitch-GX from the DRAIN pin and charges the CONTROL pin external capacitance during start-up or hysteretic operation. Hysteretic operation occurs during auto-restart, remote OFF and over-temperature shutdown. In this mode of operation, the current source is switched on and off with an effective duty cycle of approximately 35%. This duty cycle is determined by the ratio of CONTROL pin charge (IC) and discharge currents (ICD1 and ICD2). This current source is turned off during normal operation when the output MOSFET is switching. The effect of the current source switching will be seen on the DRAIN voltage waveform as small disturbances and is normal. may be used to lower the switching frequency from 132 kHz in normal operation to 66 kHz in standby mode for very low standby power consumption. LINE-SENSE (L) Pin Operation (Y, R and F Packages) When current is fed into the LINE-SENSE pin, it works as a voltage source of approximately 2.6 V up to a maximum current of +400 µA (typical). At +400 µA, this pin turns into a constant current sink. Refer to Figure 12a. In addition, a comparator with a threshold of 1 V is connected at the pin and is used to detect when the pin is shorted to the SOURCE pin. There are a total of four functions available through the use of the LINE-SENSE pin: OV, UV, line feed-forward with DCMAX reduction, and remote ON/OFF. Connecting the LINE-SENSE pin to the SOURCE pin disables all four functions. The LINESENSE pin is typically used for line sensing by connecting a resistor from this pin to the rectified DC high voltage bus to implement OV, UV and DCMAX reduction with line voltage. In this mode, the value of the resistor determines the line OV/UV thresholds, and the DCMAX is reduced linearly with rectified DC high voltage starting from just above the UV threshold. The pin can also be used as a remote ON/OFF and a synchronization input. Refer to Table 2 for possible combinations of the functions with example circuits shown in Figure 16 through Figure 40. A description of specific functions in terms of the LINE-SENSE pin I/V characteristic is shown in Figure 11 (right hand side). The horizontal axis represents LINE-SENSE pin current with positive polarity indicating currents flowing into the pin. The meaning of the vertical axes varies with functions. For those that control the ON/OFF states of the output such as UV, OV and remote ON/OFF, the vertical axis represents the enable/ disable states of the output. UV triggers at IUV (+50 µA typical with 30 µA hysteresis) and OV triggers at IOV (+225 µA typical with 8 µA hysteresis). Between the UV and OV thresholds, the output is enabled. For line feed-forward with
Using Feature Pins
FREQUENCY (F) Pin Operation The FREQUENCY pin is a digital input pin available in the Y, R or F package only. Shorting the FREQUENCY pin to SOURCE pin selects the nominal switching frequency of 132 kHz (Figure 13), which is suited for most applications. For other cases that may benefit from lower switching frequency such as noise sensitive video applications, a 66 kHz switching frequency (half frequency) can be selected by shorting the FREQUENCY pin to the CONTROL pin (Figure 14). In addition, an example circuit shown in Figure 15
LINE-SENSE AND EXTERNAL CURRENT LIMIT PIN TABLE*
Figure Number Under-Voltage Overvoltage Line Feed-Forward (DCMAX) Overload Power Limiting External Current Limit Remote ON/OFF 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Three Terminal Operation
*This table is only a partial list of many LINE-SENSE and EXTERNAL CURRENT LIMIT pin configurations that are possible.
Table 2. Typical LINE-SENSE and EXTERNAL CURRENT LIMIT Pin Configurations.
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DCMAX reduction, the vertical axis represents the magnitude of the DCMAX. Line feed-forward with DCMAX reduction lowers maximum duty cycle from 78% at IL(DC) (+60 µA typical) to 38% at IOV (+225 µA). EXTERNAL CURRENT LIMIT (X) Pin Operation (Y, R and F Packages) When current is drawn out of the EXTERNAL CURRENT LIMIT pin, it works as a voltage source of approximately 1.3 V up to a maximum current of -240 µA (typical). At -240 µA, it turns into a constant current source (refer to Figure 12a). There are two functions available through the use of the EXTERNAL CURRENT LIMIT pin: external current limit and remote ON/OFF. Connecting the EXTERNAL CURRENT LIMIT pin to the SOURCE pin disables the two functions. In high efficiency applications, this pin can be used to reduce the current limit externally to a value close to the operating peak current by connecting the pin to the SOURCE pin through a resistor. The pin can also be used for remote ON/OFF. Table 2 shows several possible combinations using this pin. See Figure 11 for a description of the functions where the horizontal axis (left hand side) represents the EXTERNAL CURRENT LIMIT pin current. The meaning of the vertical axes varies with function. For those that control the ON/OFF states of the output such as remote ON/OFF, the vertical axis represents the enable/disable states of the output. For external current limit, the vertical axis represents the magnitude of the ILIMIT. Please see graphs in the Typical Performance Characteristics section for the current limit programming range and the selection of appropriate resistor value. MULTI-FUNCTION (M) Pin Operation (P and G Packages) The LINE-SENSE and EXTERNAL CURRENT LIMIT pin functions are combined to a single MULTI-FUNCTION pin for P and G packages. The comparator with a 1 V threshold at the LINE-SENSE pin is removed in this case as shown in Figure 2b. All of the other functions are kept intact. However, since some of the functions require opposite polarity of input current (MULTI-FUNCTION pin), they are mutually exclusive. For example, line sensing features cannot be used simultaneously with external current limit setting. When current is fed into the MULTI-FUNCTION pin, it works as a voltage source of approximately 2.6 V up to a maximum current of +400 µA (typical). At +400 µA, this pin turns into a constant current sink. When current is drawn out of the MULTI-FUNCTION pin, it works as a voltage source of approximately 1.3 V up to a maximum current of -240 µA (typical). At -240 µA, it turns into a constant current source. Refer to Figure 12b. There are a total of five functions available through the use of the MULTI-FUNCTION pin: OV, UV, line feed-forward with DCMAX reduction, external current limit and remote ON/OFF. A short circuit between the MULTI-FUNCTION pin and SOURCE pin disables all five functions and forces TOPSwitch-GX to operate in a simple three terminal mode like TOPSwitch-II. The MULTI-FUNCTION pin is typically used for line sensing by connecting a resistor from this pin to the rectified DC high voltage bus to implement OV, UV and DCMAX reduction with line voltage. In this mode, the value of the resistor determines the line OV/UV thresholds, and the DCMAX is reduced linearly with increasing rectified DC high voltage starting from just above the UV threshold. External current limit programming is implemented by connecting the MULTI-FUNCTION pin to the SOURCE pin through a resistor. However, this function is not necessary in most applications since the internal current limit of the P and G package devices has been reduced, compared to the Y, R and F package devices, to match the thermal dissipation capability of the P and G packages. It is therefore recommended that the MULTIFUNCTION pin is used for line sensing as described above and not for external current limit reduction. The same pin can also
MULTI-FUNCTION PIN TABLE*
Figure Number Under-Voltage Overvoltage Line Feed-Forward (DCMAX) Overload Power Limiting External Current Limit Remote ON/OFF
*This table is only a partial list of many MULTI-FUNCTION pin configurations that are possible.
30
31
32
33
34
35
36
37
38
39
40
Three Terminal Operation
Table 3. Typcial MULTI-FUNCTION Pin Configurations.
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M Pin X Pin IREM(N) (Enabled) Output MOSFET Switching IUV L Pin IOV
(Disabled) Disabled when supply output goes out of regulation ILIMIT (Default) I
Current Limit I DCMAX (78.5%) Maximum Duty Cycle I VBG + VTP
-22 µA -27 µA
VBG Pin Voltage -250 -200 -150 -100 -50 0 50 100 150 200 250 300 350 400 I
X and L Pins (Y, R or F Package) and M Pin (P or G Package) Current (µA)
Note: This figure provides idealized functional characteristics with typical performance values. Please refer to the parametric table and typical performance characteristics sections of the data sheet for measured data.
PI-2636-010802
Figure 11. MULTI-FUNCTION (P or G package), LINSE-SENSE, and EXTERNAL CURRENT LIMIT (Y, R or F package) Pin Characteristics.
be used as a remote ON/OFF and a synchronization input in both modes. Please refer to Table 3 for possible combinations of the functions with example circuits shown in Figure 30 through Figure 40. A description of specific functions in terms of the MULTI-FUNCTION pin I/V characteristic is shown in Figure 11. The horizontal axis represents MULTI-FUNCTION pin current with positive polarity indicating currents flowing into the pin. The meaning of the vertical axes varies with functions. For those that control the ON/OFF states of the output such as UV, OV and remote ON/OFF, the vertical axis represents the enable/disable states of the output. UV triggers at IUV
(+50 µA typical) and OV triggers at IOV (+225 µA typical with 30 µA hysteresis). Between the UV and OV thresholds, the output is enabled. For external current limit and line feedforward with DCMAX reduction, the vertical axis represents the magnitude of the ILIMIT and DCMAX. Line feed-forward with DCMAX reduction lowers maximum duty cycle from 78% at IM(DC) (+60 µA typical) to 38% at IOV (+225 µA). External current limit is available only with negative MULTI-FUNCTION pin current. Please see graphs in the Typical Performance Characteristics section for the current limit programming range and the selection of appropriate resistor value.
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Y, R and F Package
240 µA
CONTROL (C)
TOPSwitch-GX
EXTERNAL CURRENT LIMIT (X)
VBG + VT
(Negative Current Sense - ON/OFF, Current Limit Adjustment)
(Voltage Sense) LINE-SENSE (L) VBG 1V (Positive Current Sense - Under-Voltage, Overvoltage, ON/OFF Maximum Duty Cycle Reduction)
400 µA
PI-2634-022604
Figure 12a. LINE-SENSE (L), and EXTERNAL CURRENT LIMIT (X) Pin Input Simplified Schematic.
P and G Package
CONTROL (C) 240 µA
TOPSwitch-GX
VBG + VT MULTI-FUNCTION (M)
(Negative Current Sense - ON/OFF, Current Limit Adjustment)
VBG (Positive Current Sense - Under-Voltage, Overvoltage, Maximum Duty Cycle Reduction) 400 µA
PI-2548-022604
Figure 12b. MULTI-FUNCTION (M) Pin Input Simplified Schematic.
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Typical Uses of FREQUENCY (F) PIN
+
+
DC Input Voltage
D
CONTROL
C
DC Input Voltage
D
CONTROL
C
S
F
S
F
PI-2654-071700
PI-2655-071700
Figure 13. Full Frequency Operation (132 kHz).
Figure 14. Half Frequency Operation (66 kHz).
+
QS can be an optocoupler output.
DC Input Voltage
D
CONTROL
C STANDBY
S
F RHF 20 k
QS 1 nF
47 k
-
PI-2656-040501
Figure 15. Half Frequency Standby Mode (For High Standby Efficiency).
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Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins
+ +
VUV = IUV x RLS VOV = IOV x RLS
RLS 2 M
CL XS F
D
DC Input Voltage
D
L
CONTROL
DC Input Voltage
C S C D
For RLS = 2 M VUV = 100 VDC VOV = 450 VDC DCMAX@100 VDC = 78% DCMAX@375 VDC = 38%
C
D
L
CONTROL
-
S
X
F
PI-2617-050100
-
S
PI-2618-081403
Figure 16. Three Terminal Operation (LINE-SENSE and EXTERNAL CURRENT LIMIT Features Disabled. FREQUENCY Pin Tied to SOURCE or CONTROL Pin).
Figure 17. Line-Sensing for Under-Voltage, Overvoltage and Line Feed-Forward.
+
2 M RLS
+
VUV = RLS x IUV For Value Shown VUV = 100 VDC
RLS 2 M
VOV = IOV x RLS For Values Shown VOV = 450 VDC
DC Input Voltage
22 k D M
CONTROL
DC Input Voltage
30 k D L
CONTROL
1N4148 C
6.2 V
C
-
S
PI-2510-040501
-
S
PI-2620-040501
Figure 18. Line-Sensing for Under-Voltage Only (Overvoltage Disabled).
Figure 19. Linse-Sensing for Overvoltage Only (Under-Voltage Disabled). Maximum Duty Cycle Reduced at Low Line and Further Reduction with Increasing Line Voltage.
+
For RIL = 12 k ILIMIT = 69% For RIL = 25 k ILIMIT = 43%
+
RLS 2.5 M
ILIMIT = 100% @ 100 VDC ILIMIT = 63% @ 300 VDC
DC Input Voltage
D
CONTROL
C
See Figure 54b for other resistor values (RIL)
DC Input Voltage
D
CONTROL
C
S
X RIL
S
X RIL 6 k
PI-2624-040501
-
PI-2623-092303
Figure 20. Externally Set Current Limit.
Figure 21. Current Limit Reduction with Line Voltage.
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Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins (cont.)
+ +
QR ON/OFF
QR can be an optocoupler output or can be replaced by a manual switch.
QR can be an optocoupler output or can be replaced by a manual switch.
RMC 45 k
DC Input Voltage
D
CONTROL
C
DC Input Voltage
47 k
D
L
CONTROL
S
X QR ON/OFF 47 K
PI-2625-040501
C
-
-
S
PI-2621-040501
Figure 22. Active-on (Fail Safe) Remove ON/OFF.
Figure 23. Active-off Remote ON/OFF. Maximum Duty Cycle Reduced.
+
QR can be an optocoupler output or can be replaced by a manual switch. For RIL = 12 k ILIMIT = 69%
D
CONTROL
+
ON/OFF 47 k
QR RMC 45 k
QR can be an optocoupler output or can be replaced by a manual switch.
DC Input Voltage
C
For RIL = 25 k ILIMIT = 43%
DC Input Voltage
D
L
CONTROL
C
S
X RIL QR ON/OFF 47 k
PI-2626-040501
S
X RIL
PI-2627-040501
-
-
Figure 24. Active-on Remote ON/OFF with Externally Set Current Limit.
Figure 25. Active-off Remote ON/OFF with Externally Set Current Limit.
+
RLS QR ON/OFF 47 k 2 M
QR can be an optocoupler output or can be replaced by a manual switch. For RLS = 2 M VUV = 100 VDC VOV = 450 VDC
+
RLS 2 M
VUV = IUV x RLS VOV = IOV x RLS DCMAX@100 VDC = 78% DCMAX@375 VDC = 38% QR can be an optocoupler output or can be replaced by a manual switch.
C
DC Input Voltage
D
L
CONTROL
DC Input Voltage
D
L
CONTROL
C
S
X RIL QR
For RIL = 12 k ILIMIT = 69%
ON/OFF
PI-2628-040501
-
S
PI-2622-040501
-
47 k
Figure 26. Active-off Remote ON/OFF with LINE-SENSE.
Figure 27. Active-on Remote ON/OFF with LINE-SENSE and EXTERNAL CURRENT LIMIT.
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Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins (cont.)
PI-2629-092203
+
RLS 2 M
VUV = IUV x RLS VOV = IOV x RLS For RLS = 2 M VUV = 100 VDC VOV = 450 VDC DCMAX@100 VDC = 78% DCMAX@375 VDC = 38%
C
+
QR can be an optocoupler output or can be replaced by a manual switch.
DC Input Voltage
D
L
CONTROL
DC Input Voltage
D
L
300 k C
CONTROL
S
X RIL 12 k
For RIL = 12 k ILIMIT = 69% See Figure 54b for other resistor values (RIL) to select different ILIMIT values
S
-
Figure 29. Active-on Remote ON/OFF.
QR
47 k
ON/OFF
PI-2640-040501
Figure 28. Line-Sensing and Externally Set Current Limit.
Typical Uses of MULTI-FUNCTION (M) Pin
+
C S S M S
+
VUV = IUV x RLS VOV = IOV x RLS
RLS 2 M
DC Input Voltage
D
S
D
M
CONTROL
DC Input Voltage
S
For RLS = 2 M VUV = 100 VDC VOV = 450 VDC DCMAX@100 VDC = 78% DCMAX@375 VDC = 38%
C
C
D
D
M
CONTROL
C
-
S
PI-2508-081199
-
S
PI-2509-040501
Figure 30. Three Terminal Operation (MULIT-FUNCTION Features Disabled).
Figure 31. Line-Sensing for Undervoltage, Over-Voltage and Line Feed-Forward.
+
2 M RLS
+
VUV = RLS x IUV For Value Shown VUV = 100 VDC
RLS 2 M
VOV = IOV x RLS For Values Shown VOV = 450 VDC
DC Input Voltage
22 k D M
CONTROL
DC Input Voltage
C
30 k D M
CONTROL
1N4148
6.2 V
C
-
S
PI-2510-040501
-
S
PI-2516-040501
Figure 32. Line-Sensing for Under-Voltage Only (Overvoltage Disabled).
Figure 33. Line-Sensing for Overvoltage Only (Under-Voltage Disabled). Maximum Duty Cycle Reduced at Low Line and Further Reduction with Increasing Line Voltage.
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Typical Uses of MULTI-FUNCTION (M) Pin (cont.)
+ +
RLS 2.5 M ILIMIT = 100% @ 100 VDC ILIMIT = 63% @ 300 VDC
For RIL = 12 k ILIMIT = 69% For RIL = 25 k ILIMIT = 43% See Figures 54b, 55b and 56b for other resistor values (RIL) to select different ILIMIT values.
C
DC Input Voltage
RIL
D
M
CONTROL
DC Input Voltage
RIL 6 k
D
M
CONTROL
C
-
S
PI-2517-022604
-
S
PI-2518-040501
Figure 34. Externally Set Current Limit (Not Normally Required-See M Pin Operation Description).
Figure 35. Current Limit Reduction with Line Voltage (Not Normally Required-See M Pin Operation Description).
+
QR can be an optocoupler output or can be replaced by a manual switch.
+
QR can be an optocoupler output or can be replaced by a manual switch.
DC Input Voltage
QR ON/OFF 47 k
D
M
CONTROL
DC ON/OFF Input 47 k Voltage
D C S
QR RMC M 45 k C
CONTROL
-
S
PI-2519-040501
-
PI-2522-040501
Figure 36. Active-on (Fail Safe) Remote ON/OFF.
Figure 37. Active-off Remote ON/OFF. Maximum Duty Cycle Reduced.
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Typical Uses of MULTI-FUNCTION (M) Pin (cont.)
+ +
QR can be an optocoupler output or can be replaced by a manual switch. For RIL = 12 k ILIMIT = 69% For RIL = 25 k
RIL QR D M
CONTROL
QR can be an optocoupler output or can be replaced by a manual switch.
QR
DC Input Voltage
ILIMIT = 43%
C
DC Input Voltage
ON/OFF 47 k RMC 24 k
D RIL 12 k S
M
CONTROL
RMC = 2RIL
C
ON/OFF 47 k
-
S
PI-2520-040501
-
PI-2521-040501
Figure 38. Active-on Remote ON/OFF with Externally Set Current Limit (See M Pin Operation Description).
Figure 39. Active-off Remote ON/OFF with Externally Set Current Limit (See M Pin Operation Description).
+
RLS 2 M
QR can be an optocoupler output or can be replaced by a manual switch.
DC ON/OFF Input 47 k Voltage
D
QR
M
CONTROL
For RLS = 2 M
C
VUV = 100 VDC VOV = 450 VDC
-
S
PI-2523-040501
Figure 40. Active-off Remote ON/OFF with LINE-SENSE.
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TOP242-250
Application Examples
A High Efficiency, 30 W, Universal Input Power Supply The circuit shown in Figure 41 takes advantage of several of the TOPSwitch-GX features to reduce system cost and power supply size and to improve efficiency. This design delivers 30 W at 12 V, from an 85 VAC to 265 VAC input, at an ambient of 50 °C, in an open frame configuration. A nominal efficiency of 80% at full load is achieved using TOP244Y. The current limit is externally set by resistors R1 and R2 to a value just above the low line operating peak DRAIN current of approximately 70% of the default current limit. This allows use of a smaller transformer core size and/or higher transformer primary inductance for a given output power, reducing TOPSwitch-GX power dissipation, while at the same time avoiding transformer core saturation during startup and output transient conditions. The resistors R1 & R2 provide a signal that reduces the current limit with increasing line voltage, which in turn limits the maximum overload power at high input line voltage. This function in combination with the built-in soft-start feature of TOPSwitch-GX, allows the use of a low cost RCD clamp (R3, C3 and D1) with a higher reflected voltage, by safely limiting the TOPSwitch-GX drain voltage, with adequate margin under worst case conditions. Resistor R4 provides line sensing, setting UV at 100 VDC and OV at 450 VDC. The extended maximum duty cycle feature of
PERFORMANCE SUMMARY Output Power: Regulation: Efficiency: Ripple: 30 W ± 4% 79% 50 mV pk-pk CY1 2.2 nF
TOPSwitch-GX (guaranteed minimum value of 75% vs. 64% for TOPSwitch-II) allows the use of a smaller input capacitor (C1). The extended maximum duty cycle and the higher reflected voltage possible with the RCD clamp also permit the use of a higher primary to secondary turns ratio for T1, which reduces the peak reverse voltage experienced by the secondary rectifier D8. As a result a 60 V Schottky rectifier can be used for up to 15 V outputs, which greatly improves power supply efficiency. The frequency reduction feature of the TOPSwitch-GX eliminates the need for any dummy loading for regulation at no load and reduces the no-load/standby consumption of the power supply. Frequency jitter provides improved margin for conducted EMI, meeting the CISPR 22 (FCC B) specification. Output regulation is achieved by using a simple Zener sense circuit for low cost. The output voltage is determined by the Zener diode (VR2) voltage and the voltage drops across the optocoupler (U2) LED and resistor R6. Resistor R8 provides bias current to Zener VR2 for typical regulation of ±5% at the 12 V output level, over line and load and component variations. A High Efficiency, Enclosed, 70 W, Universal Adapter Supply The circuit shown in Figure 42 takes advantage of several of the TOPSwitch-GX features to reduce cost, power supply size and
C14 R15 1 nF 150 L3 3.3 µH C3 4.7 nF 1 kV R3 68 k 2W D8 MBR1060 C10 560 µF 35 V C11 560 µF 35 V 12 V @ 2.5 A C12 220 µF 35 V RTN
BR1 600 V 2A
D1 UF4005 R4 2 M 1/2 W C1 68 µF 400 V R1 4.7 M 1/2 W
D
L1 20 mH
D2 1N4148
R6 150 C6 0.1 µF
T1
TOPSwitch-GX U1 TOP244Y CONTROL C
L X F
R8 150 U2 LTV817A
CX1 100 nF 250 VAC
J1 L N
F1 3.15 A R2 9.09 k
S
R5 6.8 C5 47 µF 10 V
VR2 1N5240C 10 V, 2%
PI-2657-081204
Figure 41. 30 W Power Supply using External Current Limit Programming and Line Sensing for UV and OV.
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increase efficiency. This design delivers 70 W at 19 V, from an 85 VAC to 265 VAC input, at an ambient of 40 °C, in a small sealed adapter case (4" x 2.15" x 1"). Full load efficiency is 85% at 85 VAC rising to 90% at 230 VAC input. Due to the thermal environment of a sealed adapter, a TOP249Y is used to minimize device dissipation. Resistors R9 and R10 externally program the current limit level to just above the operating peak DRAIN current at full load and low line. This allows the use of a smaller transformer core size without saturation during startup or output load transients. Resistors R9 and R10 also reduce the current limit with increasing line voltage, limiting the maximum overload power at high input line voltage, removing the need for any protection circuitry on the secondary. Resistor R11 implements an under-voltage and overvoltage sense as well as providing line feed-forward for reduced output line frequency ripple. With resistor R11 set at 2 M, the power supply does not start operating until the DC rail voltage reaches 100 VDC. On removal of the AC input, the UV sense prevents the output glitching as C1 discharges, turning off the TOPSwitch-GX when the output regulation is lost or when the input voltage falls to below 40 V, whichever occurs first. This same value of R11 sets the OV threshold to 450 V. If exceeded, for example during a line surge, TOPSwitch-GX stops switching for the duration of the surge, extending the high voltage withstand to 700 V without device damage. Capacitor C11 has been added in parallel with VR1 to reduce Zener clamp dissipation. With a switching frequency of 132 kHz, a PQ26/20 core can be used to provide 70 W. To maximize efficiency, by reducing winding losses, two output windings are used each with their own dual 100 V Schottky rectifier (D2 and D3). The frequency reduction feature of the TOPSwitch-GX eliminates any dummy loading to maintain regulation at no load and reduces the no-load consumption of the power supply to only 520 mW at 230 VAC input. Frequency jittering provides conducted EMI meeting the CISPR 22 (FCC B) / EN55022B specification, using simple filter components (C7, L2, L3 and C6), even with the output earth grounded. To regulate the output, an optocoupler (U2) is used with a secondary reference sensing the output voltage via a resistor divider (U3, R4, R5, R6). Diode D4 and C15 filter and smooth the output of the bias winding. Capacitor C15 (1 µF) prevents the bias voltage from falling during zero to full load transients. Resistor R8 provides filtering of leakage inductance spikes, keeping the bias voltage constant even at high output loads. Resistor R7, C9 and C10 together with C5 and R3 provide loop compensation. Due to the large primary currents, all the small signal control components are connected to a separate source node that is Kelvin connected to the SOURCE pin of the TOPSwitch-GX. For improved common-mode surge immunity, the bias winding common returns directly to the DC bulk capacitor (C1).
PERFORMANCE SUMMARY Output Power: 70 W Regulation: ± 4% Efficiency: 84% Ripple: 120 mV pk-pk No Load Consumption: < 0.52 W @ 230 VAC C3 820 µF 25 V L1 200 µH C14 0.1 µF 50 V 19 V @ 3.6 A
C13 C12 C11 0.33 µF 0.022 µF 0.01 µF 400 V 400 V 400 V
C7 2.2 nF Y1 Safety
D2 MBR20100
VR1 P6KE200 BR1 RS805 8A 600 V D1 UF4006
D3 MBR20100
L2 820 µH 2A C6 0.1 µF X2
C1 150 µF 400 V
D
R11 2 M 1/2 W T1
L
D4 1N4148 R8 4.7
C2 820 µF 25 V U2 PC817A C15 1 µF 50 V
R1 270
TOPSwitch-GX
C
R2 1 k
C4 820 µF 25 V R4 31.6 k 1%
RTN
85-265 VAC
J1 L N
RT1 10 1.7 A F1 3.15 A
t°
L3 75 µH 2A
R9 13 M
S
CONTROL
TOP249Y U1 R3 6.8 C5 47 µF 16 V
R5 562 C9 1% 4.7 nF 50 V C10 0.1 µF 50 V R6 4.75 k 1%
PI-2691-042203
X
F
R10 20.5 k
C8 0.1 µF 50 V
U3 TL431
R7 56 k
All resistors 1/8 W 5% unless otherwise stated.
Figure 42. 70 W Power Supply using Current Limit Reduction with Line and Line Sensing for UV and OV.
O 11/05
21
TOP242-250
A High Efficiency, 250 W, 250-380 VDC Input Power Supply The circuit shown in Figure 43 delivers 250 W (48 V @ 5.2 A) at 84% efficiency using a TOP249 from a 250 VDC to 380 VDC input. DC input is shown, as typically at this power level a p.f.c. boost stage would preceed this supply, providing the DC input (C1 is included to provide local decoupling). Flyback topology is still usable at this power level due to the high output voltage, keeping the secondary peak currents low enough so that the output diode and capacitors are reasonably sized. In this example, the TOP249 is at the upper limit of its power capability and the current limit is set to the internal maximum by connecting the X pin to SOURCE. However, line sensing is implemented by connecting a 2 M resistor from the L pin to the DC rail. If the DC input rail rises above 450 VDC, then TOPSwitch-GX will stop switching until the voltage returns to normal, preventing device damage. Due to the high primary current, a low leakage inductance transformer is essential. Therefore, a sandwich winding with a copper foil secondary was used. Even with this technique, the leakage inductance energy is beyond the power capability of a simple Zener clamp. Therefore, R2, R3 and C6 are added in parallel to VR1. These have been sized such that during normal operation, very little power is dissipated by VR1, the leakage energy instead being dissipated by R2 and R3.
C7 2.2 nF Y1 +250-380 VDC VR1 P6KE200 R2 68 k 2W R3 68 k 2W C6 4.7 nF 1 kV
However, VR1 is essential to limit the peak drain voltage during start-up and/or overload conditions to below the 700 V rating of the TOPSwitch-GX MOSFET. The secondary is rectifed and smoothed by D2 and C9, C10 and C11. Three capacitors are used to meet the secondary ripple current requirement. Inductor L2 and C12 provide switching noise filtering. A simple Zener sensing chain regulates the output voltage. The sum of the voltage drop of VR2, VR3 and VR4 plus the LED drop of U2 gives the desired output voltage. Resistor R6 limits LED current and sets overall control loop DC gain. Diode D4 and C14 provide secondary soft-finish, feeding current into the CONTROL pin prior to output regulation and thus ensuring that the output voltage reaches regulation at startup under low line, full load con