Motor Driver Chips

If you are looking for 1W rather than 1kW output what's wrong with something like the good old LM386 - bridged if necessary?

You can switch it off when not in use to save power if its standby current is too high. Putting a piezo sounder across the loudspeaker adds some transducer redundancy if this is for an alarm.

Sounds a lot more like woodwind if the mark space ratio is 3:1 or higher. 1:1 square wave sounds very brutal so you won't need much of it.

I believe this would require a change in the frequency of PWM. At the higher rate used to control the motor the off time is not long enough for the inductive current to decay. What you are saying is the brake mode would be applied closing both low side switches allowing the inductive EMF to decay and the inertial EMF to reverse the current. then when connected to the power source again the inductive EMF would push current back to the power source. So to drive the motor with power requires a fast cycle that prevents the decay of the inductive current and to regenerate requires a slower cycle that allows time for the inductor current to reverse and be boosted.

The model X and S regen down to about 4-5 mph, but the model 3 is supposed to come to a stop. I expect they are using power from the battery to do the last bit of stopping.

Yeah, that intuitively seems wasteful with AC current flowing for no benefit. The motor controller could be used that way, but I plan to use a sign-magnitude drive with unipolar pulses at any given signal level.

Thats what the VNH5019 does and is what I plan to do for the speaker.

Do they typically use inductive smoothing? The efficiency of TECs are poor at high current I believe.

Hey! I could switch it off and on like a PWM!

I have played square waves and they do not sound bad. Pleasant in fact, like an oboe. Sawtooth and triangle get harsh.

On Sunday, 14 March 2021 at 12:47:03 UTC-7, snipped-for-privacy@gmail.com wrote: ...

No. No change in frequency is required.

It is not necessary that the current decays to negative values during a single cycle - it can take many if necessary. Since the average voltage has reversed polarity the current will eventually reverse. This will affect the stabilization of any feedback loop of course and how fast the motor can respond to a speed command change.

The actual frequency is not critical. It is a compromise between losses in the switches and motor inductance (eg eddy current losses in the laminations) at the high end and excessive ripple causing losses at the low end. (as well as any loop control issues) frequencies of a few kHz are used with large motors to tens of kHz for small motors. IGBTs are limited in their switching speed whereas the SiC devices in later cars (such as Tesla) can allow higher frequencies.

The Tesla Model 3 has similar limitations in regeneration - it only gets down to zero by either applying the brakes (in some cases such as hill-hold I think it does inject current to keep the motor at zero speed). I found that a bit of a surprise when I first had the Model 3 in that it would roll-backwards on a hill as there is no regeneration at low speeds. A conventional vehicle with auto transmission doesn't. When it is set to one-pedal operation it will come to a complete stop when releasing the throttle.

The Model 3 does have slightly different characteristics in that it has a permanent magnet motor so doesn't require excitation to extract regeneration (The recent Model S and X do as well for one of the motors).

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PWM control of TECs always have to use series inductors to keep the ripple to acceptable limits or the Joule heating in the TEC resistance will lose you cooling capability. Phil Hobbs is the expert around here in that area.

kw

For just 1 watt of a 200-500 Hz square wave into a speaker with no closed-loop feedback, he could just use one of these isolated gate drivers and an external PFET (top circuit on page 7 of datasheet), 3.3 volt logic power supply on the input side, 7.5 higher-current supply on the output side, PWM "IN" at 50kHz and screw having an H bridge and class D output filter entirely.

IXDN602 is technically a gate driver, but has plenty of power on its own.

Un bel giorno Rick C digitò:

I think it just means what I wrote. They have named the input voltage pin "VM" (I suppose it can stand for "V Motor" or "V Main", who knows?) and therefore "VM rated" just means that the capacitor rated voltage has to be greater than or equal to the input voltage applied to the VM pin.

Or I can use the DRV8876 at half the price and get the current measurement for free! You forgot about that didn't you?

That is like saying use a resistor that is rated for the wattage it will dissipate. Duh!

Don't we select capacitors for the voltage always? It is a silly way to say this and why does this capacitor stand out from any of the others in this regard? I guess that is their way of saying rated to X voltage rather than saying a number. Odd wording.

I used two of the internal-H-bridge isolated-type 4A units from SL in my flying-driver 100 volt sine generator; together they can deliver a couple watts into a restive load at 3 MHz at over 70% efficiency no prob when the load is matched up.

I guess they call the topology a "multilevel inverter"; 5 steps requires two isolated power supplies. PWM is no help at that speed it has to be direct-switching. Efficiency can probably be improved if the supplies are asymmetric but I haven't looked into it too much:

seems perfectly clear since the refer to the motor voltage as VM throught out the datasheet

that capacitor stands out because unless you know how the charge pump works it might not be immedeately obvious that it needs to handle the full voltage

There is something seriously wrong with your high frequency hearing!

Square waves sound like the worst rock band ever with amp set to 11/10.

Pulse sounds like reeds and sawtooth sounds roughly like bowed strings and triangle is the first simple waveform that begins to sound pleasant. It is the result of integrating a square wave and so has much less brash harmonic content. A bit of clever diode shaping and it is a sine wave.

The good old 8038 did it that way.

Please visit this web site and play a few of the sounds so you can tell me they sound like something played by Disaster Area.

A high-side switch and grounded load makes open/short detection pretty easy. Power is transferred across the isolation so the PFET gate can be driven fully on and off at speed