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H-Bridge Motor Control

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H-Bridge Motor Controller

This arrangement uses MOSFETs as switches.
It's called an H Bridge because of the H layout of the circuit.
It's possible to buy H Bridge controller chips.
These make motor control easier and fool proof.
If P1 and N2 are on, the motor runs forwards.
If P2 and N1 are on, the motor runs backwards.
If P1 and N1 are on, both MOSFETs are destroyed by the short circuit. A control chip prevents this situation.

H-Bridge Motor Driver with four MOSFETs

The MOSFETs are connected as switches.

Push Pull Source Follower Motor Driver

The MOSFETs are connected as Source Followers.

This motor driver is less commonly used but quite suitable for small motors.

The push pull circuit suffers from the usual problem of cross-over distortion. It can be fixed in the usual way with biasing of the MOSFETs and including the MOSFETs in the negative feedback path.

For the Falstad Circuit Simulation, CTRL+Click H Bridge Circuit
In options, check European Resistors and uncheck Conventional Current.
Click the diagonally opposite pairs of switches to reverse the current.

Alternatively view H_Bridge.txt.
Save or copy the text on the web page. Import the saved or copied text into the Falstad simulator.

Here is the new HTML5 Simulator Site.

Exercise

Fill in the truth table for this controller circuit. The arrows show the electron flow for forward and reverse movement.

H Bridge Controller Task

3	2	1	0	Forward	Reverse	Brake	Coast	Catch Fire
0	0	0	0
0	0	0	1
0	0	1	0
0	0	1	1
0	1	0	0
0	1	0	1
0	1	1	0
0	1	1	1
1	0	0	0
1	0	0	1
1	0	1	0
1	0	1	1
1	1	0	0
1	1	0	1
1	1	1	0
1	1	1	1

H-Bridge Motor Control