BAP-1289 SCR Gate Driver Board

Isolated High Voltage SCR Gate Driver Board


• Drive Mutiple Devices in Series Stack or Parallel Configuration
• Complete Electrical Isolation
• Fiber-Optic Customer Interface
• User-Definable Fiber-Optic Output
• 15 A Peak Gate Current
• 10 A/uS dI/dT Gate Current
• Pulse Transformer Isolation
• High Voltage Corona Resistant > 15Kv
• High Open Circuit Gate Voltage
• On-Board Power Supply Included

• Series SCR Stacks
• Parallel SCR Arrays
• AC Transfer Switches
• Medium to High Voltage Power Supply
• Rectifiers for High Energy Physics
• Pulsed Power Systems

The AP-1289 provides a complete, reliable, turnkey solution to control single or multiple High Voltage SCR devices.

High current FET amplifiers drive individual pulse transformers that provide direct drive to each SCR gate. These encapsulated, corona resistant, high voltage pulse transformers are easily linked with supplied high voltage silicon wire to allow series stacking of multiple SCRs in order to obtain higher voltage operation.

Standard Hewlett-Packard™ fiber-optic couplers provide an intrinsically safe interface and virtually infinite noise immunity between the SCR being driven and the customers’ control electronics.

An on-board microcontroller provides timing and control of the SCR gating signals with crystal controlled accuracy, allowing precision phase control of the SCR being driven.

An on-board power supply accepts 120VAC input and generates all power needed for the logic control, fiber-optic interface and gate drive.


click images and diagrams to enlarge

Test Points
ETP3 White CONTROL Input (Active High when Fiber-optic signal on)
TP7 White SCR TRIGGER #1 (Buffered Trigger Drive)
TP9 White CONTROL Output (Active Low when Fiber-optic signal on)
TP10 White SCR TRIGGER #2 (Buffered Trigger Drive)
Led Status Indicators
D1 +5V P.S. ON = Power Supply OK / OFF = FAULT
TD4 +15V P.S. ON = Power Supply OK / OFF = FAULT
TD13 CPU RUN Normal Operation = Flashing LED (after 4 second Power-on delay).
D14 SCR ON ON = CONTROL input signal active / OFF = CONTROL signal off.

After an initial 4 second Power-On delay, LED D13 (CPU Run) will flash to indicate control logic is functioning. When an optical input signal is applied to the RCV input, the AP-1289 generates a firing pulse into the primary of the pulse transformer. The pulse transformers isolated secondary drives the SCR gate input.

120 VAC Input Power should be applied to the Control board for 4 seconds minimum, prior to energizing the SCR being controlled. AC power to the board must be maintained during the entire operating period.

Electrical / Optical Characteristics, Ta = 25°C unless otherwise specified
Parameter Typical Max Min
VIN – Supply Voltage (Volts AC) 115 - -
PIN – Supply Power (Watts)   50  
di/dt – Gate Pulse (Amps/uSec) 10    
VOM – Maximum Open Circuit Gate Voltage (Volts) 80    
PT Transmitter Output Optical Power (dBm)   -5.1 -15.5
PR(L) Receiver Optical Input Power Level Logic 0 (dBm)     -20
PR(H) Receiver Optical Input Power Level Logic 1 (dBm)   -43  
λPK Peak Emission Wavelength (nm) 660    
DT Effective Diameter (mm) 1    
tPLH – Propagation Time (μS) 0.5 1.2  
tPHL – Propagation Time (μS) 0.5 1.2  
tR – Rise Time (μS) 0.3 0.6  
tF – Fall Time (μS) 0.3 0.6  
Control Interface Definitions
Conn No. Signal Name Function
U5 RCV SCR CTL IN - Fiber-Optic SCR On/Off Control Input (LED On = SCR On)
U7 XMT SCR CTL OUT - Fiber-Optic Buffered Control Output (Optional use - Consult Factory for details)
J1-1 AC HOT 120VAC Input - L1
J1-2 AC CHASSIS GND 120VAC Chassis Ground Input - G
J1-3 AC NEUTRAL 120VAC Input - L2 2


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