Sorensen DCS Series 3kW Supplies
Theory of Operation
Selection of IEEE-488 programming occurs when the IEEE card pulls pin 13 of U5-D and pin 2
of U5-A low through connector P2, pin 4. This causes the output of both U5-D and U5-A to go
high and switch OFF both U4-C and U4-B. The IEEE programming signal is then input to the
voltage control op amp through resistor R78.
Operation of the current control circuit is the same as the voltage control circuit with CMOS
switches U4-D and U4-A and NAND gates U5-B and U5-C providing the required functions.
The operation of the front panel remote indicator LED and the J3 remote programming indicator
signal is controlled by transistor Q2. Whenever either remote analog or IEEE-488 programming
is selected, the output of U5-D and/or U5-C is high. This high signal is input to the base of
transistor Q2 through diodes CR13 and/or CR14, turning ON the transistor, and activating the
LED and the monitor signal.
Remote Analog Programming Input Circuits
These circuits are used to buffer, scale, and calibrate the remote analog programming signals
before they are input to the voltage and current control circuits. Op amp U10 and its related
components condition the signal to the voltage control circuit. Input to the circuit is through pin 9
of the rear panel J3 connector. Diodes CR26 and CR27 clamp any out-of-range or reverse
polarity inputs. Trimpot R93 is used to null any offset voltage from U10. Trimpot R60 is used to
calibrate the signal. For programming with remote voltage sources, jumper JMP1 is used to
select either 0-5V or 0-10V input scales. For remote programming with 0-1 mA current sources,
resistor R41 generates the required 0-5V signal from the programming source. For remote
programming with 0-5k ohm resistances, the 1 mA current source provide by op amp U13-B
generates the required 0-5V signal. U13-B and its related parts produce a regulated 1 mA
output by maintaining a fixed 2.5V drop across resistor R97 through transistor Q5.
Operation of the current programming input circuit is the same as the voltage circuit, with op
amps U11 and U13-A and their related components performing the required functions.
Remote Sense Line Protection Circuit
The remote sense line protection circuit shuts down the power supply output in the event that:
•
the sense line connections are reversed.
OR
•
the positive or negative output load lines become disconnected, with the remote sense
lines connected.
The circuits consists of relays K1 (positive sense) and K2 (negative sense) and diodes CR1 and
CR2. When either of the fault conditions occur, current flows through the relay coils and
activates the relay contacts. This co15V to the internal shutdown circuit to disable the
output of the supply. Diodes CR1 and CR2 limit the voltage across the relay coils for reverse
polarity conditions.
Operation Manual
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