Ametek Sorensen DCS-E Series, Руководство по эксплуатации

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Sorensen DCS Series 1kW and 1.2kW Supplies Theory of Operation
M362500-01 Rev K 3-3
3.1.2 Simplified Full Bridge Converter Theory
See Figure 3-1 .
The input AC line voltage is rectified and filtered by CR35, C32(A,B,C), and C72(A,B,C) to a raw
DC voltage which is supplied to the power FETs, Q13-Q16, on the primary of power transformer
T1. Resistor R116, R116A and relay K1 form an input surge current limiter which reduces the
inrush current to the filter capacitors C32(A,B,C), and C72(A,B,C) during power-up. The power
FETs and the primary winding of T1 form a bridge which is driven at 70 kHz by pulse width
modulator (PWM) U6 through FETs Q7-Q12, Q18 and Q19 and drive transformer T2. A current
sense transformer, T3, in the primary of the power transformer provides a feedback signal to the
PWM which is compared to a limited error signal derived from the output current and voltage
control circuits. The output of the comparator controls the on-time of the PWM output drive
waveforms on a cycle by cycle basis thereby controlling the primary current and the output of
the power transformer. Diodes CR301 and CR302 on 8V thru 20V models (D1and D2 on 33-
100V models, CR301-CR304 on the 150V and 300V models and CR300-CR307 on the 600V
model) rectify the output of power transformer T1 and inductor L3 and capacitors C51, C52 and
C53 (C153 with series connected C106, C107 on the 600V model) filter the rectified signal to
provide the DC output.
A current shunt (R91) in the output return line develops a voltage proportional to the output
current. This current information is amplified by U15 and compared to the setting of the current
limit control in the current control error amplifier U4-1. The output voltage is also monitored and
compared to the voltage control setting in the voltage error amplifier U5. The outputs of the
voltage and current error amps are OR’d through CR18 and R26 and this signal is fed into the
PWM error amplifier inverting input providing the negative feedback required to produce a
regulated output. The output voltage and current information from the current and voltage
control circuits is also fed to the front panel A1 assembly where it is displayed on the digital
voltage and current readouts.
Transformer T4, rectifier CR42 and regulators U9-U13 provide the necessary auxiliary supply
voltages for the PWM circuit, voltage and current control circuits, the A1 display board and the
raw DC supply for drive transformer T2. A 6.2V reference is also derived from the 12V supply
for use in display circuits by temperature compensated reference diode CR1 and resistor R2.
Transformers T1, T2, T3 and T4 provide output isolation from the line potentials in the primary
circuit, the PWM circuit and the auxiliary supply circuits respectively.
3.1.3 Detailed Circuit Description
This section provides further detail for troubleshooting purposes. Please read the previous
section as an overview and then refer to the detailed assembly schematic in
Section 6 .
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.