Reference Manual

Power Supply Unit PSU DC

4 (6) EN/LZT 720 0248 R1B

4 FunctionDescription

DC/DC

Output

Filter

Input

Filter

Control and Supervision

Indi-

cators

Opto

Interface

Input

Output

P007805A

Control Alarm

Figure 1 PSU –DC block diagram

The PSU DC consists of the following main units:

• Input filter (EMC filter)

• DC/DC Converter

• Output filter (EMC filter)

• Control and supervision circuits

4.1 Input filter

The incoming voltage passes through the input filter first, where it is filtered to

prevent unwanted signals from being radiated from the PSU.

4.2 DC/DC Converter

The DC/DC converter is a phase-shifted, full-bridge converter that converts

the DC into a square wave. This is then fed into the primary side of the

transformer. The converter limits the current in case of overload.

In the transformer, the voltage is converted to a 24 V AC square wave, and

this wave is rectified to DC through a diode rectifier.

The output provides constant power regulation, rather than the more common

current limited, and delivers 1200 W over the whole output voltage range from

22 to 29 V DC.