AMETEK DCS-E 1KW Series - Manual (Page 47)

M362500-01 Rev H 3-1
SECTION 3
THEORY OF OPERATION
3.1 Power Circuit (A2 Assembly)
This section describes the operation of the A2 assembly switching regulator power circuit.
Three subsections cover basic switching regulator theory, a simplified description of the
Sorensen full bridge converter, and a more detailed circuit description intended for
troubleshooting purposes.
3.1.1 Basic Off-Line Switching Regulator Theory
An off-line switching power supply first converts the AC input line voltage to high voltage DC by
diode rectification and then chops the DC at a high frequency. This high frequency waveform is
applied to the primary of a power transformer that provides a step-up or step-down in voltage
and electrical isolation on its secondary. The secondary waveform is rectified and filtered,
giving a smooth DC output voltage. Feedback from the secondary circuit is applied to a pulse
width modulator (PWM) control circuit which controls the on-time of the primary circuit switching
waveform. This increases or decreases the voltage on the secondary of the power transformer
so that output regulation is obtained.
The use of high frequency transformers in switching power supplies has the advantage of
requiring less volume, less weight, and dissipating less heat than the lower frequency
transformers in conventional linear power supplies.
CAUTION
Potentially LETHAL VOLTAGES exist on the A2 circuit board on the primary side
of the isolation barrier. Troubleshoot with care, preferably with power off and
recognizing that filter capacitors store potentially LETHAL and DESTRUCTIVE
ENERGY even for some time AFTER POWER is REMOVED. Always use an
isolation transformer connected ONLY to the power supply input when making
test measurements on the primary side circuits.