H bridge Problem

[keets]

Hi, this is my first post on this forum.

I am developing 24 V PMDC Motor control using H-bridge with 4 IRF540,IR2110 as drivers to the mosfets & PIC18F4523 for control with PWM.
Basically the application is of speed control.

PWM frequency is 10 kHZ.
My problem is that i don't get output voltage to the motor not above 10 volts at 100% duty cycle.Controller pwm o/p shows the variation but motor voltage varies from 0- 10 volts.

voltage across drain/source of High side mosfet varies from 13v-15v at any duty cycle. where as d-s voltage of lower side mosfet never exceed .3v.

vb-vs voltage for ir2110 is 3v.
I tried with different bootstrap capacitor .47mf,1mf,10mf no change is seen in the behavior.

what could be the problem?

 

[panic mode]

post your circuit

 

[keets]

View attachment 65125

 

[panic mode]

your circuit does not follow connection diagram in the datasheet:
https://www.electro-tech-online.com/custompdfs/2012/06/ir2110.pdf

for example outputs are swapped (LO and HO), diode from Vcc to Vb is not in right place (should go from 3 to 6, not from 3 to 5).
i didn't bother to look for more issues, this schematic is not very readable.

 

[keets]

I am sorry , I made some mistakes while drawing the ckt.
I will scan the copy of ckt & post it tomorrow.
Sorry again...

 

[panic mode]

Nothing to be sorry about,

If you are already making drawings on a computer, you could try to use one of the cad packages to make the drawings.
there are free ones too. for example Linear has LT Spice (meant to simulate circuits) or KiCad (PCB design) etc.
Any program you use will start with schematic capture. It would be nice to see actual signal names (HO, LO, Vb, Vcc, etc.) at each pin.

Just an idea...

 

[johansen]

make sure the bootstrap circuit is working.

the datasheet has the circuit in it...

 

[keets]

View attachment 65148

Please find the attached schematic

 

[johansen]

i'm supprised your IR 2110 hasn't blown up.

download the datasheet and read it, it is not built for a negative referanced h bridge, you've got the whole thing backwards.

 

[ronsimpson]

The IR2110 can not run at +5V! It needs 10 to 20V.

 

[shortbus=]

The IR2110 can not run at +5V! It needs 10 to 20V.

The logic side can

 

[ronsimpson]

Yes I see it now! Logis is 3-20V.

 

[keets]

what do you mean by negative reference H Bridge?
Please tell me what exactly has gone wrong?
I am getting 0-10v at the output but not full 24v.

 

[ronsimpson]

The two left side FETs look good. The two right side FETs are not right. Up side down

The power for the motor is +12V or -12V (+12V)

The bottom FETS should have 0/10 volts on the gate.
The top FETs should have 0/22V on the gate. (the source should have 0/12V and the gate should be 0/+10V more) 0+0=0 and 12+10=22V

 

[ronsimpson]

The IR2110 can not turn on the top FETs for a long period of time. The FETs must be 'switching'. The bottom FET driver is powered from the +12V supply. The top FET driver is powered by power stored in a capacitor. This cap will run down if not replenished by switching. You probably have to have the duty cycle kept between 1% and 99% and must never go to 0% or 100%. If you leave one of your inputs at 0 or 1 for a long time the IR2110 will not work the way you want.

 

[keets]

Sir my PWM frequency is 10 khz is it ok?
Also at 75% duty cycle how much voltage is expected at the output of 24v bridge?
I am getting no more than 9v on resistive as well as motor load.
Also variation is not linear i.e for 1% to 80% duty cycle.
I am stuck up at final stage please help.

 

[ronsimpson]

10khz is probably OK. I would not use small capacitors like .01uf. I have never used this gate driver that slow. 0.1uF is what I use at 100khz (which I call slow). You could use 0.1uf and (1uF to 10uF ele. cap) in parallel.

Your schematic shows 12 volt supply! At 75% you output should be at 75% of supply voltage and the other output should be at 25% of supply. (measured with a average meter) A scope will see the voltage at 0 and 12 (supply). This is measuring from output to ground.

If you measure from out1 to out2 you should see about 50% of supply voltage at 75%.

 

[keets]

Sir my supply voltage is 24v. & I am getting only 8.16v at the output. at approx 75% duty cycle. Upper mosfet is getting very hot.
Please let me know what do you mean by out1/out2
What may be wrong ? Are my connections & component values ok?

 

[ronsimpson]

By "output1 and output 2" I am talking about the two motor leads.
Every where labeled "12" is really 24 volts???
Have you increased the size of the capacitors?

 

[ronsimpson]

Sir my supply voltage is 24v. & I am getting only 8.16v at the output. at approx 75% duty cycle. Upper mosfet is getting very hot.
Please let me know what do you mean by out1/out2
What may be wrong ? Are my connections & component values ok?

How are you measuring 8.16 volts?
On the schematic there is a spot "-12" and two places "+12" are all three now "+24"?