Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: ErikY on January 13, 2013, 09:05:21 AM
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I am trying to understand how H-bridges work and have been looking at a lot of different designs.
Most designs use p-ch MOSFETS for the high side and n-ch for the low side.
From what I understand, n-ch current flows from D to S when switched on, and p-ch current flows from S to D when switched on.
I get how each one is switched on, makes sense.
What I am struggling to understand is, when I look at H-bridge schematics, the motor terminals are connected between the D of the p and n mosfets.
That makes sense to me on the p-ch side, where current flows from S to D, but not on the n-ch side where current flows from D to S.
I would think that the motor would be between the D on the p ch and the S on the n ch.
Can anyone tell me what I am missing?
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When switched on, current can flow *both ways* in a MOSFET. When switched off, the MOSFET has a body diode that prevents flow one way.
For the MOSFET to block current when not switched on, the Drain should point towards the load when a P-channel is a high-end switch and an N-channel is a low-end switch. This means that the diode is reversed (not conducting) for each of the devices.
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When switched on, current can flow *both ways* in a MOSFET. When switched off, the MOSFET has a body diode that prevents flow one way.
For the MOSFET to block current when not switched on, the Drain should point towards the load when a P-channel is a high-end switch and an N-channel is a low-end switch. This means that the diode is reversed (not conducting) for each of the devices.
Got it! Thanks! Very helpful.