KEPCO MBT Series - Manual (Page 119)

MBTSVC111609
4-13
4.3.1 ANALOG CONTROL BOARD A1 (See Schematic Diagram, Figure 6-18)
The main function of Analog Control Board A1 is to compare Reference Voltages derived from
Digital Control Board A3 with the voltage and current feedback signals from the power section.
This board also contains the detection portion of the protection circuits incorporated into the
MBT Series Power Supply.
This board is identical for all options of a particular model, however it differs between models
due to a few components — such as voltage and current channel feedback resistors, scaling
resistors, feedback capacitors — and the position of the jumpers used to establish Model (see
PAR. 2.8). The principal circuits of the board are:
• Voltage and current reference amplifiers (U2A and U2B)
• Voltage and current comparison amplifiers (U7 and U6)
• Voltage and current monitor amplifiers (U3A and U3B)
• Overvoltage and overcurrent tracking circuits (U9C/D and U9A/B)
• Overvoltage and overcurrent comparators (U8B and U8C)
• Voltage and current over-range comparators(U1B and U1A)
• Operating mode comparator (U8A)
• Current sensing and scaling circuit (U5 and U4)
• Analog gate and predriver circuit (CR7, CR8, Q1)
• Constant current return supply circuit (Q2)
• Output capacitor discharge circuit (Q3)
• Path fault detector circuit (U10A)
The A1 Board is connected to Mother Board A5 via A1P1, and to the sensing resistor A10R1 via
two twisted wires connected to A1J6.
The path fault detector detects when the voltage drop between the power and sense terminals
exceeds 0.5V; this condition can be caused by an interruption of continuity between power and
sense terminals, or when the power leads are too long. The /PATH FAULT signal is applied to
Digital Control Board A3, where it is monitored by the software for 10 program cycles (maximum
20 milliseconds). If the path fault condition still exists at the end of this delay, Digital Board A3
programs the output voltage and current to zero.
(MR, MGR MODELS) For "R" option units, Digital Control Board A3 programs the output to DIS-
ABLED, causing the output relays to open and isolate the power supply from the load upon
detection of a path fault condition.
(M, MG MODELS) Units without the “R” option relays are configured with jumper A1J7 installed.
This allows U10B to act on the /Overvoltage/Overcurrent line applied to Flags/Relays Board A2
via Mother Board A5. If the path fault condition persists longer than 6 milliseconds, this activates