Mosfet Gate Drive Transformer

Current through a mosfet between drain and source is controlled by a drive voltage applied to the mosfet gate.

Mosfet gate drive transformer.

Once the mosfet transistors are turned on their drive current is practically zero. Follow faraday s law keep v t constant otherwise saturate. Gate drive transformers gts are a key component in many modern electronic systems. Consideration as designing driver transformer ground referenced floating drive keep 500 v isolation if a 400 v pre regulated pfc exists.

Gate drive transformers are used to deliver the controlling gate voltage pulses between the drain and source of a mosfet while providing isolation between the mosfet and the controlling drive circuit. The 16sct000 is an igbt mosfet gate driver 15v nominal vg chip to control the conduction state of a high side switch from the secondary of a small high voltage isolation transformer. The 16sct000 will drive the gate of the hv switch ab ove the emitter source while the secondary winding of the transformer drives the complementary input signals. Despite various floating channel mosfet igbt driver ics being available a transformer coupled gate drive is still the better option to use for high power applications for many reasons.

The gate drive described in this paper uses a printed circuit board based transformer in combination with the memory effect of the power mosfet input capacitance to achieve the isolation. These simple devices are used to drive the gate of metal oxide field effect transistors mosfets while providing galvanic isolation between the gate and the control circuitry. The mosfet transistors are simpler to drive because their control electrode is isolated from the current conducting silicon therefore a continuous on current is not required. Gate driver circuits need an isolated floating bias supply to maintain the required turn on bias when the fet source rises to the input voltage.

Once the mosfet transistors are turned on their drive current is practically zero. A gate drive transformer is optimized for transmitting rectangular electrical pulses with fast rise and fall times to activate or deactivate a switching device. Minimize the leakage inductance the delay between output and input windings may kill the power mosfets. The mosfet transistors are simpler to drive because their control electrode is isolated from the current conducting silicon therefore a continuous on current is not required.

This transformer is a bi directional link between the ground referenced control ic and the floating gate drive.