AMETEK DCS-E 3kW Series - Manual (Page 84)

Theory of Operation Sorensen DCS-E Series 3kW Supplies
5-14 M362295-01 Rev C
5.3.6 Front Panel Displays and Controls (A1 PCB)
The A1 front panel PCB consists of:
•
Output voltage and current displays
• Local controls for output voltage and current limit
•
Local control potentiometer for the OVP set point
• Switches for:
• previewing local voltage and current limit control settings (SW3 V & I CHECK)
•
previewing local OVP set point (SW4 OVP CHECK)
• selecting remote or local control (SW1 REM/LOC)
•
activating output standby circuit (SW2 STANDBY)
• LED indicators for operating mode, over-temperature, remote programming
operation, shutdown, and OVP
•
IEEE-488 Option connector P2 and LED indicators for ADDRESSED , SERVICE
REQUEST , SYSTEM FAULT , FOLD , ERROR , FAULT , POLARITY , and ISOLATION
O UTPUT V OLTAGE AND C URRENT D ISPLAYS
The voltage and current displays are made up of three or four (depending on the model)
seven-segment LED displays (DS1-DS8) driven by 3 1/2-digit analog to digital (A/D) converters
(U1 and U2). In both the voltage and current display circuits, an analog signal from the A2 PCB
voltage and current control circuits is compared to a reference voltage on the A/D to generate
the digital output for the seven-segment displays. The A/D conversions are done and the
displays updated approximately three times per second.
In the voltage display circuit, the 5V reference from the A2 PCB is divided down by resistors
R15, R16, and calibration potentiometer R17 to provide a 1V reference for U2 at pin 36. The
analog input from the voltage control circuit (via connector P1, pin 6) is filtered by resistor R9
and capacitor C15 before being input to pin 31 of U2. Resistor R7 and capacitor C13 set the
conversion frequency. Capacitors C14, C16, and C17 with resistor R10 are used by the A/D in
its reference integration, auto zero, and input signal integration circuits. Resistors R8, R18, and
R19 are used to select the appropriate decimal point position for displays DS6-DS8.
The current display circuit operates similarly to the voltage circuit. Resistors R11-R14 form
the reference divider. The analog input from the current control circuit via P1-8 is filtered by R3
and C5. R2 and C2 set the conversion frequency. Capacitors C4, C6, C7, and R4 are the
integration and auto zero components. R1, R5, and R6 select the appropriate decimal point.
L OCAL O UTPUT V OLTAGE AND C URRENT L IMIT C ONTROLS
The local controls for voltage and current limit are ten-turn potentiometers (R27 and R20
respectively) which provide a 0-5V reference to the voltage and current control circuits on the
A2 PCB.