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Power MOSFET H-bridge (MEC124E)

This article was taken from my book Robotics, Mechatronics and Artificial Intelligence (sold out) published in the United States and also from previous articles in other publications, with minor updates. It shows an H-bridge using Power MOSFETs, ideal for controlling DC motors and can be used as a shield.

The low Rds(on) (see note) characteristic of power MOSFETs makes these devices especially appropriate for power control, as in the case of H-bridges. The circuit shown by Figure 1 is the basic configuration using N-channel power MOSFETs.

* Resistance between drain and source pins when turned on.

 

Figure 1  full bridge with power MOSFETs
Figure 1 full bridge with power MOSFETs

 

 

Power MOSFETs with Rds(on) below 1? are common. These transistors can control currents in the range between 1 A and 20 A in circuits like this one.

The transistors for a specific application are selected according to the current in the motor. They must be mounted on heat sink, especially if you’re controlling high power motors (above 2 A).

This circuit operates in exactly the same way as Block 62. The following table gives the logic of the control.

 


 

 

Be careful to avoid the forbidden condition, which shorts out the power supply. Using a fuse in series is a good way to keep your circuit from becoming a smoke factory.