Sorensen DCS Series 3kW Supplies
Theory of Operation
regulate the output under no load or lightly loaded conditions. The down programming circuit is
also used to discharge the output capacitors whenever the control circuit signal goes negative
or when any of the shutdown circuits are activated.
5.2.6
Control, Programming, OVP, Shutdown, Monitoring, and
Auxiliary Supply Circuits (A2 PCB)
The A2 Control PCB consists of the following circuits:
1. Auxiliary supply circuit
2. Voltage and current control circuits
3. Thermal sense, fan control, and thermal shutdown circuits
4. Over Voltage Protection (OVP) circuit
5. Remote shutdown circuit
6. Remote programming, monitoring, and sense protection circuits
The
auxiliary supply circuit
uses the high voltage DC supply from the A6 Rectifier PCB in a
multiple output flyback-type switching supply to generate the +28V, +15V, -15V, +5V, -6.2V, and
+5V
REFERENCE
voltages required by the various control circuits.
The
voltage and current control circuits
monitor the output voltage and current feedback
signals, compare them to a reference signal from the front panel controls or remote
programming circuit, and provide a control signal for the A3 PCB PWM circuit.
Thermal sensors
monitor the temperature of the input rectifier heatsink, the main switching
transistor heatsink and the output rectifier heatsink to provide an input signal for the fan speed
controller circuit and thermal shut down circuit.
An
Over Voltage Protection (OVP) circuit
monitors the output voltage and shuts down the
supply whenever a user selected voltage is exceeded.
An optically-isolated
remote shutdown circuit
allows the use of remote AC, DC, or TTL
compatible signals to disable the supply's output. The remote shutdown circuit activates an
internal shutdown/soft start circuit which:
•
pulls the voltage control circuit reference to zero,
•
activates the PWM shutdown, and
•
activates the down programming circuit.
This internal shutdown circuit is also used by the thermal shutdown, OVP, sense line protection,
and PWM sync circuits, and the front panel standby switch to disable the output of the supply
whenever any of these circuits are activated.
The A2 PCB also provides access to
remote programming, monitoring, and sense circuits
via a rear panel DSUB connector J3. Remote programming circuits are provided for:
•
Output
voltage
•
Output current limit
•
OVP trip point
Operation Manual
5-3