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Number 2260
Application Note Burn-in Testing Techniques for
Series Switching Power Supplies
would be connected in parallel with the load resistance to mea-
Introduction sure the power supply voltage. The load resistance is chosen to
One of the consequences of the rapid growth of the telecommu- emulate the load resistances found in the final application, but
nications, desktop computing, and network server markets is a may be chosen to reach full output capacity to perform
burgeoning demand for switching power supplies and DC-to-DC stress testing.
converters. While these power supplies are typically inexpensive,
a high level of quality must be maintained through careful
production testing. Monitor
110V or Power Supply Load
220V AC Input Voltage
Highly accelerated stress screening (HASS) or "burn-in" Under Test R (3.3V - 48V)
is a common production step for switching power supplies
designed for computers and servers. Extended environmental
testing is performed to ensure the product will continue to func-
Figure 1. Monitoring the output of a switching power supply.
tion properly over its entire service life. It is not uncommon to
age and monitor thousands of power supplies at once. When
designing this type of test system, the biggest challenge is deal- Output Cycling
ing with the high number of channels the system must monitor To stress the power supplies being tested further, the output is
and the test system surroundings. Large numbers of switching repeatedly turned on and off. If a device is destined to fail, the
power supplies can produce tremendous amounts of electrical failure will generally occur when the output is cycled. To capture
noise, which can reduce the test system's measurement perform- failure data, the output voltage of each power supply is measured
ance significantly. during each time the output is turned on, as shown in Figure 2.
After the output is cycled 15 to 20 times, the output is left on
and the power supply is left to continue aging. While the output
Test Description is left on, the voltage is measured only occasionally.
High-end power supplies and DC-to-DC converters with outputs
from 400W to 2000W are commonly found in many telecom and 15