A P RESENTATION O N A T RIGGER S YSTEM WITH H IGH V OLTAGE I SOLATION FOR M ULTIPLE S WITCHING D EVICES by S K Rai Assistant Professor Electronics Engineering Department B K Birla Institute of Engineering & Technology (BKBIET) Pilani (Raj.) Authors: S K Rai, P Tandon, S Jangid & Rahul Varma

Defining Problem: 2/15 The semiconductor switches are the main elements of all kind of power converters or pulse power supply design. So, the trigger pulses to control these switches play most important role in these designs. There are a number of research papers related to these designs based on different topologies. But, the trigger pulse generators i.e. trigger systems has not been explained completely. In this paper, a trigger system with high voltage isolation is described in detail.

Conclusions: 3/15 1. The proposed trigger system is an open loop design. 2. The design of a simple pulse generator has been presented with two different types of pulses: Pulse-1: 80 μs (Fixed) Pulse-2: Variable up to 5 μs Delay between Pulses: 10 μs (Fixed) 3. Optical isolation has been used. 4. High frequency inverter and induced voltage is used to isolate driver Circuit. 5. The trigger system has been tested successfully with a Marx Generator. This work has been carried out at IEG, CSIR-CEERI, Pilani. Frequency: Variable up to 10kHz

Trigger System: Provides trigger pulses to Semiconductor Switches to turn ON or OFF. 4/15 Trigger System Pulse Generator ( With Controller ) Pulse Generator ( With Controller ) Driver Circuit Driver Circuit =+ High Low

Trigger System & Isolation Issue: 5/15 Reference of Power Circuit Common Reference of Trigger System A Basic Switching Circuit Trigger Pulse No issue of Isolation……..

A Basic Switching Circuit When & Why Isolation Required ??? 6/15 Trigger System Floating or Series Connected Devices In Power Circuit Q1Q1 Q2Q2 Q3Q3 Reference of Trigger System So, Isolation is required among individual trigger pulses (i.e. Pulses generated by Pulse Generator and driver circuits both should be isolated)

7/15 Proposed Design: Two types of synchronized pulses have been generated with high voltage isolation. Pulse Generator Specifications: Frequency of the pulses (f s )= up to 10 kHz Pulse width of Pulse-1 = 80 µs (Fix) Pulse width of Pulse-2 = up to5 µs Delay = 10 µs (From trailing edge of Pulse-1) Master Pulse to get Frequency Variation Max up to 10 kHz Pulse-1: 80 µs Delay: 10 µs Pulse-2: Variable up to 5 µs

8/15 Pulse Generator Design: Pulse Generator Variable Resistors to change Pulse width & Frequency

9/15 Pulse Generator Testing : Output PulsesSingle Output Pulses Pulse-1 (80µ s) Pulse-2 (up to 5µ s) Conclusion-1: It is an open loop design.

10/15 Multiple Pulse Generation with Isolation : To get a number of similar pulses, a buffer IC ULN 2003 is used and since, pulses should be isolated to optical transmitters are used to transmit the pulses. Requirement is multiple isolated pulses. ULN 2003 Optical Transmitter HFBR1521 Optical Transmitter HFBR1521 Variable Resistors to change Pulse width of Pulse-2 & Frequency of the pulses

Isolated Driver Circuit : Since pulses are transmitted via optical way so driver circuit includes to sub-circuit-(i) Optical Receiver and (ii) Gate Driver Circuit. Again, the driver circuit must be isolated. Driver Circuit = Optical Receiver + Gate Driver Circuit It must be isolated i.e. its DC Supply must be isolated. Inverter (Operating Frequency = 20 kHz) Induced Voltage in the Coil Regulated DC Power Supply 11/15

Isolated Gate Driver & Receiver Supply: +15 V for the driver from the induced voltage in the inductor Conclusion-3: Optical isolation has been used. Conclusion-4: High frequency inverter and induced voltage is used to isolate driver Circuit. Receiver: HFBR2521 Driver: IXDD414CI 12/15

Testing With Marx Generator: 13/15

Top View of the PCB Prototype Testing Arrangement Input dc Voltage Output Pulse Conclusion-5 The trigger system has been tested successfully with Marx Generator. 14/15

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