I will not bore you with all the possible combination (check the datasheet for your part for the exact details) but one example could be the following: PWMĪs you can see the enable signal is active low in this example, and the PWM non-inverted.Īnother control method is when the driver exposes only a single, three-state control input. Again, these can be active low or active high. Some however have an ‘enable’ and a ‘PWM’ pin for example. Some simply expose two control signals (active low or high) each for the two controlled transistors. With half-bridge drivers, which control one low and one high-side FET, the options are more complicated. In active high control, the sates are the opposite: control In active low control, the FET is closed, when the control signal is low, or 0: control For both low- and high-side drivers, the two basic schemes are active low or active high control.
#H BRIDGE GATE DRIVER CIRCUIT DRIVERS#
I will use the following h-bridge element notations during the article:Īs we’ve seen before there are many drivers and there are many ways those drivers need to be controlled as well.
#H BRIDGE GATE DRIVER CIRCUIT HOW TO#
The discussion will concentrate on how to generate the various control signals and how to implement the different drive modes we’ve discussed before.įor the most part, the detailed implementation of the driver and the bridge itself (PMOS or NMOS devices, etc.) are not a concern here, though occasionally we’ll have to take the special requirements of those parts of the design into consideration. In this article we will step further back from the ‘bare metal’ of the H-bridge and concentrate on the digital control of the bridge. These circuits range from trivial to complex, and have some interesting properties, like turn-on and –off delay or limits on duty cycle that will have implications for our current discussion.
In the previous part of the series we went through the various circuits that can take logic level digital signals and make them suitable for driving the gates of the bridge power FETs.
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