Scr Gate Drive Transformer

The 1 1 1 pulse transformer is used to generate pulse for back to back scr.

Scr gate drive transformer. Typical gate drive transformers are designed using ferrite cores to reduce cost. Choice of the gate current polarity triggering in the 2 nd and 3 rd quadrants for s nubberless triacs. The use of pulse transformers in triac triggering circuits offers many advantages. Typical gate drive circuit usually triggering is inhibited when the anode voltage of the thyristor is negative.

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. With the use of pulse transformers as shown in figure 1. The firing circuit of gate pulse by 1 1 pulse transformer is given in the figure b. 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.

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. The basic gate drive transformer has several design variations each of which is determined by the specific application. 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. Figure 6 shows a gate trigger pulse transformer with properly insulated multiple secondary windings.

Some common schematics and their corresponding turns ratios are listed in fig. The function of the series resistor r is to limit the holding current of the scr. Galvanic insulation between the power and gate drive circuit a few kv. The scr is tyn612 with a igm peak gate.

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. Some of the common core packages are ee eer etd and efd. A special section deals with the gate drive requirements of the mosfets in synchronous rectifier applications. Gate drive circuit with a few components.

It is a pair of antiparallel scrs being driven by a 1 1 1 pulse transformer. The function of diode d is to prevent reversing gate current. Coilcraft s off the shelf gate drive transformers simplify the design of your gate drive circuit and shorten design cycle time. An on board power supply accepts 120vac input and generates all power needed for the logic control fiber optic interface and gate drive.

Procedure for ground referenced and high side gate drive circuits ac coupled and transformer isolated solutions are described in great details.