How much do you know about the transformer-isolated MOSFET drive circuit?

How much do you know about the transformer-isolated MOSFET drive circuit?

Some partners have privately messaged to write an article about the transformer-isolated MOSFET drive circuit. Today, the YFW editor will talk about the principle of the transformer-isolated MOS drive circuit.

The transformer isolation drive circuit is mainly based on the laws of electromagnetic induction and electrical insulation isolation.

Specifically, when an alternating voltage is to the primary winding of the transformer, an alternating current will be generated in the primary winding, and the current will induce a changing magnetic field in the iron core.According to the law of electromagnetic induction, the alternating magnetic field will induce an electromotive force in the secondary winding, thus realizing the transmission of voltage from the primary the secondary, and the voltage relationship satisfies V1/V2 = N1/N2. (Where V1 and V2 are the voltage amplitudes of the and secondary respectively, and N1 and N2 are the number of turns of the primary and secondary windings respectively)

Below we will look at the isolation drive circuit (as shown in the figure)

A PWM duty cycle signal is sent from the IC (control module) to control one of the primary coils of the transformer, thus generating self-induction and then mutual induction to the secondary coil.

When the same name end of the primary coil is positive, the same end of the secondary coil is positive.

At this time, the secondary coil (above) of the transformer drives the MOSFET through the positive pole and R2 Because R2 is at a high potential here, the high voltage flows through the MOSFET at this time, and the MOSFET is on.

When the secondary (below) connected to one end of R3 is negative, the voltage at R3 is low, and the MOSFET discharges through R7, and theFET is cut off at this time.

When the duty cycle signal is low, the same name end of the primary coil is negative. The same name end of secondary coil is also negative, at this time the secondary coil (connected to one end of R3) is positive, and the MOSFET is driven through R7 and the MOSFET (below) is on, and the MOSFET (above) is off when the same name end of the secondary coil is negative.

Therefore when the IC sends a duty cycle signal that is high, the MOSFET above is on and the one below is off. When it is low, the MOSFET is off and the one below is on.

The duty cycle signal is isolated by the transformer so that the twoMOSFET are alternately turned on, thusating the high and low voltages and preventing high and low voltage interference.