Protecting SMPS and driving circuit from inductive loads (motor)

[amaschas]

Hi all, I have been working on a project that involves driving a 24V/1A (max under load) geared motor bidirectionally from a SMPS. I've been trying to understand what exactly is involved in protecting the power supply from the various conditions that can arise from inductive loads and getting a bit confused. From what I understand, when a motor slows or reverses, the energy stored in the coils need somewhere to go, and so the circuit that controls the motor needs to be able to absorb that energy somehow. My application involves turning the motor one direction for a few seconds, and then reversing it and turning it the other way, under load the entire time. If I understand correctly this kind of a worse case scenario for back EMF. The motor will be rotating fairly slow, < 60 RPM, and it is is geared which IIRC mitigates this issue somewhat, but I feel like I'm still going to need some kind of back EMF protection.

The driver I am using is a MAX14870 (https://www.pololu.com/file/0J885/MAX14870.pdf) which seems way too tiny to be able to drive a motor, though the specs are well above what my motor requires. It advertises free-wheeling diodes, but if I understand correctly those only clamp the voltages under the level that would damage the _driver_, and I'm actually not quite clear on whether those diodes actually absorb any energy. I'm wondering if I need some sort of circuit to feed any excess energy into a beefy resistor, or if the driver itself is sufficient to handle the motor load in my case.

[edit] I'm considering a scaled down version of this circuit: https://drmrehorst.blogspot.com/2022/05/bank-account-protection-circuit-for.html, though without the capacitor since the IC data sheet specifically notes "Maxim does not recommend using external capacitors across the motor terminals. Added capacitance between H-bridge outputs increases the power dissipated in the H-bridge".

Alternatively I am considering a MOV like this one: https://www.digikey.com/en/products/detail/eaton-electronics-division/MLVC13V024C1050/13687315

[fullmoon6661]

Seconded on this, I'm currently having project that's fairly similar to this and facing similar problem..

For now I've designed only:
1. Reverse battery protection using P-MOSFET so I assume that the power supply is protected from any motor supply spikes.
2. "Bank account protection circuit" similar to the linked. I think this acts like a voltage clamp that dissipate any spikes through Q1 and R3 (spikes that doesn't get absorbed by C1).

though without the capacitor since the IC data sheet specifically notes "Maxim does not recommend using external capacitors across the motor terminals. Added capacitance between H-bridge outputs increases the power dissipated in the H-bridge".

So I don't think this is correct since this capacitor (C1) is added to the motor driver supply line, not to the motor terminals.

There are few cases I think still can happen. For example when the supply disconnected (thus driver chip turned off) and the motor gets driven by external force, it will induce voltage on driver chip output, and while they're high impedance they can still get damaged (?) I'm not sure about this so I haven't put anything on..