Scr Gate Drive Transformer

A gate drive transformer isolates the controlling gate drive circuit from the switch node when driving the mosfet gate and may also scale the output voltage via an appropriate primary to secondary turns ratio.

Scr gate drive transformer.

Typical gate drive circuit usually triggering is inhibited when the anode voltage of the thyristor is negative. The firing circuit of gate pulse by 1 1 pulse transformer is given in the figure b. This can be achieved by using a relatively high gate trigger voltage that tires the scr faster resulting in a uniform tum on time a pulse transformer is used to ensure that all gates are triggered simultaneously. This is because in this mode the thyristor acts like a low gain transistor and amplifies the gate current which is seen as an increase in anode leakage current.

Gate drive circuit with a few components. Procedure for ground referenced and high side gate drive circuits ac coupled and transformer isolated solutions are described in great details. 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. Coilcraft s off the shelf gate drive transformers simplify the design of your gate drive circuit and shorten design cycle time.

Typical gate drive transformers are designed using ferrite cores to reduce cost. Some common schematics and their corresponding turns ratios are listed in fig. The function of diode d is to prevent reversing gate current. The use of pulse transformers in triac triggering circuits offers many advantages.

For more information see the overview for mosfet and igbt gate drivers product page. A special section deals with the gate drive requirements of the mosfets in synchronous rectifier applications. I have been searching for this everywhere including the books i have but i just can t find the design procedure for the circuit used to drive an scr using a pulse transformer. The scr is tyn612 with a igm peak gate.

The function of the series resistor r is to limit the holding current of the scr. It is a pair of antiparallel scrs being driven by a 1 1 1 pulse transformer. The 1 1 1 pulse transformer is used to generate pulse for back to back scr. It has three external terminals anode gate and cathode and uses the alternative symbols of figure 1 a and has the transistor equivalent circuit of figure 1 b figure 2 shows the basic way of using the scr as a dc switch with the anode positive relative to the cathode and the scr controlled via its gate.

An on board power supply accepts 120vac input and generates all power needed for the logic control fiber optic interface and gate drive. With the use of pulse transformers as shown in figure 1. Galvanic insulation between the power and gate drive circuit a few kv. Some of the common core packages are ee eer etd and efd.

The basic gate drive transformer has several design variations each of which is determined by the specific application.