Back EMF

My controller is connected to a DC power supply and fed by 24 V. To suppress the regenaration/back EMF, I tried to implement the circuit given in AN90727. I chose a resistor having 2 mega ohm resistance, chose a battery of 12 Volt DC. When I energized the circuit, the zener diode burned.
What is the issue with it? Wrong selection of battery or resistor or both? If yes, kindly suggest me the battery voltage and resistor resistance to implement the ciruit in AN90727.
I have to use the DC power supply to run the motors, so the AN90727 is mandatory for me. Thanks

With a 12V battery, you will need a zener that is a little over 12V. This in turn will cause excessive power to be generated into the zener. For example, assuming 13V zener and 5A of regen current, there will be 13V * 5A = 65W. That will definitely fry the zener.

You are better off using a 24V battery connected in parallel directly to the 24V power supply without diode or any other component. The only thing to be careful is to have your battrey fully charged when you connect it to the power supply.

Alternatively, you can implement an active circuit with a MOSFET and a power resistor (an not battery). We are publishing such a circuit in the updated user manual that we will release in a few days. Send an email to This email address is being protected from spambots. You need JavaScript enabled to view it. to request an advance copy.

Will two 12 V batteries in series work?
And, do the batteries need to fully charged every time when the system is energized? (Since the battery might have discharged to some extent over the course of time).

Will 2 x 12 Volt batteries in parallel work? (Since standalone 24 V battery is not available).

yes