Data Sheet

February 16, 2009

QSW025A0B Series Power Modules; DC-DC Converters

36 – 75Vdc Input; 12Vdc Output; 25A Output Current

7

Test Configurations

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.

LOAD

CONTACT AND

SUPPLY

CONTACT

DISTRIBUTION LOSSES

RESISTANCE

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.

Design Considerations

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

mounted close to the power module helps ensure the

stability of the unit. Consult the factory for further

application guidelines.

Safety Considerations

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

EN60950-1.

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.

both the input and output pins are to be kept

floating.

The input pins of the module are not operator

accessible.

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.

Note:

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

unearthed lead.