Full-bridge drivers obviously have two low-side and two high-side drivers so they can drive all four FETs.Īs we’ve discussed in the previous article, low-side MOSFETs are always N-channel ones, while on the high-side we can you either P-channel or N-channel devices.Half-bridge drivers combine one low- and one high-side driver, so they can drive Q1 and Q2 (or Q3 and Q4) together.

High-side drivers in turn are designed to drive Q1 or Q3.

There are low-side drivers, that are designed to drive Q2 or Q4 on our bridge.

Control the turn-on and turn-off times of the FETsĭrive circuits can come in many shape or form.

Provide additional safety functions, like over-current protection.

Generate voltages for the high-side gate-drive circuitry (for N-channel drivers).

Translate the input command into gate-drive signals according to the drive mode.

On top of that, many drive circuits include additional functionality:

Provide enough current to charge and discharge the gates fast enough.

Translate the input voltages to suitable levels to drive the gates.

The drive circuitry for an H-Bridge is basically the electronics that sits between the PWM (and potentially other) digital control inputs and the MOSFET gates. To make referencing easier, let’s review the H-Bridge circuit: Understanding of the various drive-modes will also be useful, so reading the sign-magnitude drive, the lock anti-phase drive and the asynchronous sign-magnitude drive articles isn’t a waste of time either, though those pieces go into quite a bit of more detail than what is needed to follow this text.

You will take the most out of this write-up if you are already fairly familiar with H-Bridge basics, so if you aren’t, I suggest you read the introductory piece of the series first. We will discuss the trade-offs between them and what influences the various parameters of the drive circuits. In this article I will go through the available options for drive circuits. In the previous installment of the series we’ve gone through the high-level design decisions that you have to make when designing an H-Bridge, and we’ve discussed the considerations for selecting the MOSFETs and the catch diodes that will make up the bridge.

H bridge with mosfet