# A motor controller schematic diagram



## Dennis (Feb 25, 2008)

I found a full schematic diagram of a motor controller that is 12 volts, 60 amps, designed by Leeson. It can be found in this PDF: http://www.leeson.com/TechnicalInformation/pdf/manual_speedmaster_dcadjspeed.pdf on page 8. I would not directly copy this controller as it has features such as IR compensation which means the motor is held constant speed regardless of load applied to the shaft which is not really useful for traction applications. So some redesign should be done. What I like about this design is the use of synchronous rectification using MOSFETS instead of high speed switching diodes for the free wheeling.


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## Tesseract (Sep 27, 2008)

Dennis said:


> ...What I like about this design is the use of synchronous rectification using MOSFETS instead of high speed switching diodes for the free wheeling.


The MOSFETs shunting the motor in that schematic are being used strictly for their built-in anti-parallel diodes. Notice how the gates are shorted to the sources? Synchronous rectification requires that those MOSFETs be turned on whenever the buck MOSFETs are turned off.


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## Dennis (Feb 25, 2008)

Indeed their gates are tied to their sources. Good eye....


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