February 16, 2009
QSW025A0B Series Power Modules; DC-DC Converters
36 – 75Vdc Input; 12Vdc Output; 25A Output Current
Note: Measure input reflected-ripple current with a simulated
source inductance (LTEST) of 12 µH. Capacitor CS offsets
possible battery impedance. Measure current as shown above.
Figure 9. Input Reflected Ripple Current Test Setup.
Note: Use a 1.0 µF ceramic capacitor and a 10 µF aluminum or
tantalum capacitor. Scope measurement should be made
using a BNC socket. Position the load between
51 mm and 76 mm (2 in. and 3 in.) from the module.
Figure 10. Output Ripple and Noise Test Setup.
Note: All measurements are taken at the module terminals.
When socketing, place Kelvin connections at module terminals
to avoid measurement errors due to socket contact resistance.
Figure 11. Output Voltage and Efficiency Test Setup.
Input Source Impedance
The power module should be connected to a low
ac-impedance source. A highly inductive source
impedance can affect the stability of the power module.
For the test configuration in Figure 9, a 330μF
electrolytic capacitor, Cin, (ESR<0.7Ω at 100kHz),
mounted close to the power module helps ensure the
stability of the unit. Consult the factory for further
For safety-agency approval of the system in which the
power module is used, the power module must be
installed in compliance with the spacing and separation
requirements of the end-use safety agency standard,
i.e., UL60950-1, CSA C22.2 No. 60950-1, and VDE
If the input source is non-SELV (ELV or a hazardous
voltage greater than 60 Vdc and less than or equal to
75Vdc), for the module’s output to be considered as
meeting the requirements for safety extra-low voltage
(SELV), all of the following must be true:
The input source is to be provided with reinforced
insulation from any other hazardous voltages,
including the ac mains.
One VIN pin and one VOUT pin are to be grounded, or
both the input and output pins are to be kept
The input pins of the module are not operator
Another SELV reliability test is conducted on the
whole system (combination of supply source and
subject module), as required by the safety agencies,
to verify that under a single fault, hazardous
voltages do not appear at the module’s output.
Do not ground either of the input pins of the
module without grounding one of the output pins.
This may allow a non-SELV voltage to appear
between the output pins and ground.
The power module has safety extra-low voltage (SELV)
outputs when all inputs are SELV.
The input to these units is to be provided with a
maximum 30 A fast-acting (or time-delay) fuse in the