Please recommend a hi-power motor driver....

[jtexas]

to be driven with PWM. Need an operating range of 10% (+/- 5%) to 100% power.

It's a 5-speed motor powered by a single 12 volt wet-cell deepcycle battery, one direction only, peak draw 48 amps (manufacturer specs; I have it on a 40-amp circuit breaker which it has never tripped). I'm looking for increased efficiency at less than full power.

any suggestions welcome.

thanks!

 

[dknguyen]

If it's one direction only, just build it yourself. Unidirectional DC motor drivers are the easiest thing in the world.

1 MOSFET, 1 gate driver (either built discretely out of a resistor or two and a PNP and NPN transistor, or if you're lazy just buy an IC), 1 snubber circuit (either a diode, R-C, or both).

WHat is to be driven with PWM? The motor, or the bridge? Because the motor being driven by PWM is synonomous with variable speed DC motor drives and doesn't really need to be mentioned. Or do you mean you will generate a PWM signal that the bridge accepts as an input? If so, then you need to do no more than what I just said- send the PWM signal into the gate drivers and you're off.

Dead. Easy. And far cheaper than anything you would buy.

In fact, it's so simple I can't let you walk away and spend money buying something overbloated because you did not understand my description of the circuit.

If Vbatt will never exceed the maximum gate voltage of the NMOS, you can get 10-15V by connecting it straight to Vbatt. Also don't forget the large electrolytic capacitor that goes between Vbatt and ground, and the smaller ceramic capacitor that goes between 10-15V and ground.'

10-15V is just a typical gate voltage required to turn on NMOSs. So if you choose an NMOS with different ranges, then change 10-15V to whatever is needed (you may need a regulator, step-down or step-up if your battery voltage is too low to turn on the NMOS or too high for the NMOS gate to tolerate). Step-down is cheap and easy- just use a linear regulator to step down Vbatt. Step up is more expensive but you shouldn't need it at the voltages you gave.

 

[jtexas]

right, I don't need to drive a driver, just a driver to accept a PWM signal. Battery voltage will generally range from 12.65 to 12.25 but never less than 10.6 or more than 14.

your circuit looks like just the thing.

Just for clarity, are you saying a capacitor from Vbatt to ground...what about a resistor to discharge it when the motor is shut off?

The motor presently has a momentary on/off switch and a 5-position rotary speed control. Its on for mostly 3 to 20 second bursts and occasionally 5 to 10 minutes continuously. What I would do is, set the speed control on full power and add the PWM controller I guess on the ground side as you have shown.

My uncertainty is, in selecting components that won't crap out on me. Any recommendations there would be appreciated.

Thanks!

 

[dknguyen]

right, I don't need to drive a driver, just a driver to accept a PWM signal. Battery voltage will generally range from 12.65 to 12.25 but never less than 10.6 or more than 14.

your circuit looks like just the thing.

Just for clarity, are you saying a capacitor from Vbatt to ground...what about a resistor to discharge it when the motor is shut off?

If you wish, a 10Mohm resistor or something. But it's low voltage so I don't think it's needed (you aren't gonna die if you touch 12V).

My uncertainty is, in selecting components that won't crap out on me. Any recommendations there would be appreciated.

Thanks!

THese are the ones I will use on my motor driver of similar size:

Schottky Diode - Diodes Inc. - PDS1040
NMOS- International Rectifier - IRF1324S-7PPbF
NPN/PNP pair- Zetex - ZDT6718
Discrete NPN - Zetex - ZTX618 (thru hole), FMMT618 (surface mount)
Discrete PNP - Zetex - ZTX718 (thru hole), FMMT718 (surface mount)
NMOS Heatsink (if needed) - Aavid THermalloy - 7109D
Decoupling Cap For Gate Driver - .1uF-1uF-4.7uF? ceramic
Decoupling Cap For Motor Supply - Electrolytic 1000mF?

These components can tolerate up to 20V (limited by the BJTs and NMOS max gate voltage). But if you use a regulator to provide the "10-15V" to the NPN/PNPs, then the limit is 24V of the NMOS source-drain.

THe NMOS needs 10V or greater (gate can tolerate 20V max). So if the voltage range is as you state, then you can directly connect Vbatt to the gate "10-15V".

 

[Oznog]

right, I don't need to drive a driver, just a driver to accept a PWM signal. Battery voltage will generally range from 12.65 to 12.25 but never less than 10.6 or more than 14.

If this is hooked up to a vehicle, there are often spikes far greater than that when running the starter or just whenever. Even very brief surges will damage a gate. A zener diode and current-limiting series resistor on the gate driver will keep that under control.

 

[jtexas]

great info, dkn, just what I was looking for.

it's a marine application, oz, current installation has a dedicated battery but will consider that in case we ever hook up to cranking battery.

thanks!