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Control ICs for Switched-Mode Power Supplies TDA 4601 Bipolar IC Features q q q q q Direct control of the switching transistor Low start-up current Reversing linear overload characteristic Base current drive proportional to collector current Protective circuit in case of disturbance P-SIP-9-1 Type TDA 4601 Ordering Code Q67000-A2379 Package P-SIP-9-1 The integrated circuit TDA 4601/D is designed for driving, controlling and protecting the switching transistor in self-oscillating flyback converter power supplies as well as for protecting the overall power supply unit. In case of disturbance, the rise of the secondary voltage is prevented. In addition to the ICs application range including TV-receivers video tape recorders, hifi devices and active loudspeakers, it can also be used in power supply units for professional applications due to its wide control range and high voltage stability during increased load changes. Semiconductor Group 7 06.94 TDA 4601 Pin Definitions and Functions Pin No. 1 2 3 4 5 6 7 8 9 Function VREF output Zero passage identification Input control amplifier, overload amplifier Collector current simulation Connection for additional protective circuit Ground (rigidly connected to substrate mounting plate) DC-output for charging coupling capacitor Pulse output - driving of switching transistor Supply voltage Block Diagram Semiconductor Group 8 TDA 4601 Circuit Description The TDA 4601 is designed for driving, controlling and protecting the switching transistor in flyback converter power supplies during start-up, normal and overload operations as well as during disturbed operation. In case of disturbance the drive of the switching transistor is inhibited and a secondary voltage rise is prevented. Start-Up The start-up procedures (on-mode) include three consecutive operating phases as follows: 1. Build-Up of Internal Reference Voltage The internal reference voltage supplies the voltage regulator and effects charging of the coupling electrolytic capacitor connected to the switching transistor. Current consumption will remain at I9 < 3.2 mA with a supply voltage up to V9 approx. 12 V. 2. Enabling of Internal Voltage - Reference Voltage V1 = 4 V Simultaneously with V9 reaching approx. 12 V, an internal voltage becomes available, providing all component elements, with the exception of the control logic, with a thermally stable and overload-resistant current supply. 3. Enabling of Control Logic In conjunction with the generation of the reference voltage, the current supply for the control logic is activated by means of an additional stabilization circuit. The integrated circuit is then ready for operation. The start-up phase above described are necessary for ensuring the charging of the coupling electrolytic capacitor, which in turn supplies the switching transistor. Only then is it possible to ensure that the transistor switches accurately. Normal Operating Mode / Control Operating Mode At the input of pin 2 the ze