H-bridge schematic with speed control.
Figure 1

More Power MOSFET H-Bridge Circuit Examples

by Lewis Loflin

Here we look at some variations for my power MOSFET H-bridge.

In the variation above we have an enable pin to turn the H-bridge on/off and a separate direction pin. A 'HIGH' turns on Q7 driving its collector 'LOW' and through CD4011b being used as an inverter produces a 'HIGH' on the gate of Q5 turning the MOSFET on, thus the motor will run. Note the power connections for the CD4011 not shown.

With a 'LOW' or zero volts on the Direction pin the collector of Q6 is 'HIGH' Q1 and via CD4011a Q4 are turned on (Q2 and Q3 are turned off) creating a current path through Q1, the motor, and Q4. When the Direction pin goes 'HIGH' (5-volts) Q6 switches on driving its collector to 'LOW' switching off Q1 and Q4 and turning on Q2 and Q3 creating a reverse current path through Q2, the motor, and Q3.

There are few calculations to be done with this circuit. The ratings of Q1-Q5 depends on the motor and the operating voltage is limited to 15 volts due to the CD4011. This was designed to connect to a 5-volt microprocessor.

Parts list:
Q1, Q2, Q5, N-channel MOSFET IRF630
Q3, Q4, P-channel MOSFET IRF9630

Note that if using the above listed MOSFETs Vcc is limited to20-volts due to Vgs. For more on that see the following:

CD4011 pin connections
Figure 2. Cd4011 pin connections.

using MOSFETs for H-bridge
Figure 3.

Another variation of the above circuit. Note that the run enable in both circuits can be pulse-width modulated to control motor speed.

P-channel Power MOSFET Switch
Figure 4

This circuit can be used to cut Vcc on/off and also be pulse-width modulated to control motor speed.

See the following spec sheets:

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