hip4081 drive problems

[notfet]

I have several questions about this drive circuit I have made. After breadboarding and running a small motor this circuit works.(with the exception of R9 and R10 which I added but not breadboarded) It is when I make the main board I have problems( although the small motor still runs) when the drive motors are powered up I blow mosfets and the hip4081 What I noticed is when the pwm signal is at a low duty cycle(10% or less) both drive leds(led 1 and 2) are lit up. indicating back emf is going to my hip4081 chips. Note the first board (or breadboard) did not have any of the line filter circuitry. Before I replaced the mosfets and 4081, I cut out the mosfets and connected each leg of the 4081 to my scope and one leg was firing at the wrong time causing shoot-through. I replace the 4081 and everything fires correctly the delay settings of the 4081 are well within the range of the IRFP2907 mosfets so there is no shoot-through problem there. Replacing everything and running a resistive load, I get full power. Not shown is the shunt/op-amp current monitor which reduces Pwm demand thru the Arduino microcontroller and that works as well. I ran the batteries to the drive motors and my back emf was around 120 volts out of a 24vdc motor, well over the limits of the 4081. that is when I made the filter. Running straight 24v from the batteries and the circuit shown the back emf is limited to the TVS diode's 40 v which is acceptable for the 4081 but what about the mosfets? When I tried to limit Vgs with a 19volt zener the motors ran but it's speed and power was greatly reduced. So here is my series of questions…
1. Will the resistors R9 and r10 reduce the internal mosfet in the 4081's power?( my thinking is that if any back emf gets thru they will delay enough for the TVS diodes to protect the 4081.( 100Ω was just a guess) if so what resistance should they be?
2. will the line filter reduce back EMF to a point that the motor becomes inefficient?
3. At a pwm frequency of 31.5 kHz what should the resonance of inductors L2 and L3 be?
4. Is the common mode choke necessary?
5. if I am overlooking something what is it?

Here are all the details about this drive.
24v dc from batteries 22ah
180 watt motors run around a load of 5-6 amps 11 peak
31.5 khz Pwm drive signal from arduino controller.
flywheel diodes handle 20 amps each.
Back emf frequency Im not sure if my reading is correct it vary's from 8mhz to 2.3 ghz(5 ns scale you can see a pattern)
motor rpm full speed 3400
line filter L1 common mode 10 turns each side w/14 ga mag wire yellow torrid coil
L2 and L3 9 turns same core as above 14 ga mag wire

any help will be much appreciated as I have ruined 5 boards and countless mosfets( hence my name notfet lol.)
pin names on the 4081 7 and 8 are reversed but the pins are correct. I need to edit my part in Eagle

 

[BradtheRad]

Your D10-11 diode pairs are oriented incorrectly.

Questions:

All of your mosfets appear to be N-mos. Do the high side mosfets get a high enough gate voltage, in order to turn them on fully, regardless whether they have a definite path from their source terminal to zero grournd?

Does your commutator produce sparks? If so then you have an idea what voltage your mosfets are subjected to. As an experiment, does anything change when you reverse the leads to the motor?

Have you tried using switching devices that have no insulated gate? Such as high voltage transistors?

 

[notfet]

sorry about d-10 and d-11 I redrew the original as it was cluttered with all the other circuits such as microprocessor relays etc. I did not want to delete the original and did not want to confuse people with things unrelated.
the mosfets are n-ch and on the scope gate voltage in both directions using the small motor was 15-16 volts. and the small motor was fully on and with 3%-100% pwm ran fine. I did notice that when it ran backwards it destroyed the first hip4081 thats why I added R2 and c2 in the reverse direction and the small motor ran fine for an hour in each direction. when I connected the large motor it ran for 2 secs and blew 2 mosfets and the 4081.
reversing did the same thing( it,s actually 2 channels) on the other motor.
I did build a transistor drive board but scrapped it because I could not drive the motor fully and when I increased the base current to handle the load I could not drive it extremely slow 1-5%pwm.
I like the Mosfets if i could get this to work reliably.

 

[notfet]

The bottom Schematic is the corrected one

 

[BradtheRad]

Your system ran okay with a resistive load, and a small motor. So the most likely problem is that high V spikes are coming from your large motor, especially as you turn the current up high.

Since have an oscilloscope, it's a good idea to check for spikes.

Also to try a variety of tests with your large motor. Your PWM applies 24V at 5 kHz. What intensity of spikes come from applying 12V at 5 kHz?

What intensity of spikes come when you apply 6V continuous?
24V continuous?
Etc.

You have installed diodes where they can do a certain amount of good. It is not easy to find the right snubbing tactics to solve the spike problem. So it seems to be normal to burn up a few mosfets when experimenting with switching high current through inductive loads.

This link is to the website of someone (Richard Torrens) who makes motor controllers professionally. He favors the use of discrete devices (such as transistors). It's possible he has found they survive operating conditions better than mosfets and IC's. You may find some useful tips at his website.

Some pages are for viewing by paid members. Some pages are free to public view.

H Bridge Motor control

https://www.4qdtec.com/bridge.html

H bridge switch for small motors

https://www.4qdtec.com/h.html

 

[notfet]

What is the best way to determine the inductance of L2 and L3? and is L1 necessary? I will replace the mosfets Change the PWM freq. to 5khz and let you know the results

 

[notfet]

As soon as I connected the big motor, I put the scope to record and 12 volts at 5 kHz pwm it blew the mosfets, the 30 amp fuse and the 4081. I do not have a way to do 6 volts. the scope shows ac with 70v pole to pole even though dc is sent out. I was unclear in post#1 R5 and r6 are not in the circuit that I ran the test neither is L1 L2 or L3. I put those in because I ran straight battery thru those components to the big motor to see if I could cut out the harmful EMI. So I Ask again before I etch another board. Will r5 and r6 hurt performance? and What is the best way to determine the inductance of L1 L2 and L3 and is L1 necessary? Also Dis is held high by a resistor as per Intersil instructions. the Arduino pulls it low after a 2 sec delay.

 

[BradtheRad]

the scope shows ac with 70v pole to pole even though dc is sent out.

Assuming your power supply is 24V smooth DC...
Your motor apparently is creating high voltage spikes, which overcome the diodes and other protective measures.

All this happens in the first second of operation.

The spikes must have a polarity which defeats diode absorption.

Furthermore it will not work to put a diode across the motor itself (not in either direction).

There is just a chance your 5 kHz PWM sets up a resonant action. Coils have a self-resonant frequency due to internal capacitance. With a high L/R (as your system has), it is easier for resonance to get out of control.

It may help to try different PWM frequencies.

Remember a motor at power-up draws several times its normal running current. Do you know the maximum current it draws in the first second of start-up?

Have you tested your motor with plain DC?
Different PWM frequencies?

Also did you say you tested your system with a heavy resistive load? This load should equal what your motor equals at start-up.

 

[notfet]

with straight battery power(24v dc) I do not measure any noise as the batteries must be absorbing it. I measure 13 amps start current and 3.3 amps no load but that is with a brick under the carriage and the wheel free spinning. I left the brake off(by accident) and it blew a 30 amp fuse. while free spinning I put a 10 amp fuse and it blew it
I changed he fuse to 15 amps and it runs fine. As far as the drive board I am going to put sockets so I can change the mosfets without un-soldering them.I am tired of blowing mosfets up. I have tried everything making sure the delay is high enough for the irfz2907's to turn off(no shoot-through),the start delay, the 2907's should handle the current, and protection to make sure ali and bli never get turned on at the same time. I put a 3 ohm resistor across the motor and you are right the noise is highest on start up. I will try different pwm frequency and see how that works maybe a larger inductor? or smaller. I made a mistake in post#1 where I asked about r9 and r10 those are fine. What i meant is I want to add r5 and r6. I know the 4081 uses that to drive AL0 and BL0 Would I be incorrect to add these? thanks for your help.

 

[notfet]

I simplified the design and now blowing the 4081 when a resistive load is connected on the M1 and M2 terminals. Using a milliamp meter and a 220ohm resistor the h-bridge works fine in 31khz pwm as I increase resistance to 100ohm I get the calculated milliamps at 24v but the 4081 gets hot. and a 3 ohm it blows up. Why are the mosfets not taking the load? the gate capacitance is high 13000pf for the mosfets but the data sheet says the 4081 can supply 2.5 amps. it heats up in the 500ma range. I was thinking the bootstrap caps were too high so I reduced them to 0.22uf with the same results. I know reducing the pwm frequency will help but any lower and the motor rings so for now I would like to make this work as a last resort i will lower the freq. I think raising the gate resistors might help but 100ohms seems high to me and I could loose the diodes but they help cut-off the mosfets. Thanks for any help. The data sheets do not help because most of the calculations are not explained.

 

[freedomhouse]

hi,

i'm building an H bridge with 4n mosfet







IRFIZ44NPbF 55 Vds and 31A Id.
I'm using a dspic 15khz pwm for drive hip4081.
-i blow 5 hip and finally it work with a 12V 1A (no load) DC motor ( it's the motor for electric car glass).
-I used uf4007 diodes and 2.2uF tantalio capacitors for bootstrap
- 20 ohm and schottky diode for gates
-100kohm resistors for delay + uC delay
-0,1 uF capacitors between Vcc Vdd hip pins

the drive work not well but i must work on it only because the speed is less than the nominal speed.

the problems of hip that burn is the EMI or delays that creates a short circuit between the mosfets of the same side and burs the port...the output is 12V cc with no PWM signal.


have you scoped the AXO and BXO without load conected for see if there isn't any port burn?

I used a 0.9A no load motor and hip don't heats..it heats only when there is a shortcircuit that burn some port and ruin the chip.


I posted a video...no any mosfet or driver hearts:

https://youtu.be/94jaUIDckp4