# How to regen a DC motor from the high-side of a boost converter?

I am planning to drive a 24v motor from a 12v battery, using a DC-DC boost circuit to generate the 24v and an H-bridge to PWM drive the motor.

A problem arises when the motor goes into the regen quadrant. The motor will just dump energy into the high-side capacitors of the boost circuit, overcharging them since there is no way to send current back out to the battery.

So here is my idea: Place a P-channel mosfet between the high and low sides of the boost circuit, with a voltage comparator and reference connected to the gate. This way, the mosfet would be programmed to dump from the high-side capacitors to the low-side whenever the output is above 25v.

Obviously this would put a lot of stress on the caps and mosfet, so I'm looking for any advice on how to achieve this more elegantly. Maybe if I threw an inductor in there somewhere it wouldn't be such a harsh dump of current?

• If you do not need to charge the battery from braking the motor, you may get some inspiration from the HERIC architecture used for inverters. – jippie Aug 22 '14 at 20:06
• @jippie what is this HERIC architecture of which you speak? – Adam Head Aug 22 '14 at 20:08
• I was looking for the a reference electronicproducts.com/Power_Products/Invertors/… – jippie Aug 22 '14 at 20:08
• That is interesting. The problem is I don't necessarily just want braking, but the ability to regen normally by controlling the voltage applied to the motor. – Chriszuma Aug 22 '14 at 20:47
• If you want to "regen" I guess this means regenerate therefore in my mind this means a battery to store the excess energy and whatever you call it, it will apply some amount of braking to the motor. – Andy aka Aug 22 '14 at 21:34