Six types of MOSFET gate drive circuits, how many have you seen?

How many types of gate drive circuits are there for MOS tubes? Have you seen the following six types of drive circuits?

1. This is a basic drive circuit . Each component is clearly visible.

It needs to consider the ability of the gate to apply a voltage higher than Vth, the G-pole voltage higher than Vth turns the MOS tube on, and the G-pole voltage lower than Vth turns the MOS tube off. There is also the driving ability to fully charge the input capacitor.

( R1: affects switching speed/loss; R2: pulls the gate-source voltage down to 0V when the input signal is open)

 2. Use a logic circuit or microcontroller to drive the MOS tube. The MOS tube provides a conductive path, which can effectively reduce the power consumption of electronic equipment.

 When the MOS tube cannot be driven at 5V , a digital logic drive circuit can be used to convert the drive voltage into 15V.

It should be noted here that the driving voltage should be greater than 12V, but not more than 20V.

When R2 and R3 are connected in series to increase the gate drive resistance, the MOS tube cannot be driven in saturation mode, resulting in slower switching speed and increased switching loss.

On the contrary, if R2 is reduced, a larger leakage current will flow to the drive circuit when the MOS tube is turned off, increasing power consumption. This is its disadvantage, but it can be solved by a push-pull circuit.

3. The figure below is a push-pull circuit : it is also applicable when the driving current is insufficient.

 4. The fourth is the half-bridge/full-bridge high-end drive , which applies a high voltage to the gate to turn on the upper tube Q1. However, since the source voltage of Q1 will change with the switching of the lower tube Q2, the driving power supplies of Q1 and Q2 cannot share the same ground.

 5. The fifth is pulse transformer drive, which does not require the use of a separate drive voltage.

Here, the Zener diode (2.6) is used to quickly reset the pulse transformer, and the other circuit (2.7) adds an additional PNP tube to improve the switching performance.

 This circuit uses a capacitor and a pulse transformer in series to allow the MOS tube to apply reverse bias to the MOS tube when the device is turned off , thereby increasing the switching speed. In addition, the capacitor here also blocks the DC bias and prevents the pulse transformer from reaching the saturation point.

 However, sometimes in order to protect the circuit, it is necessary to isolate the MOS tube from the driver.

6. Finally, use optocouplers and floating power supplies. However, the optocoupler output requires a separate power supply . If you want to use an optocoupler to drive the high side of a half-bridge or full-bridge, you will need a floating power supply.

 The above are the six types of MOS tube gate drive circuits we talked about in this issue. There are other circuits in actual applications. Let’s discuss them together when we have the chance!