Is anyone familiar with the IR2304 MOSFET driver?

860
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Hi All,

I'm not sure if this is the correct foray to discuss my questions about the specific IR2304 IC chip.

However, I've run into some difficulties making my first inverter and I've asked a range of questions on another website:
https://forum.allaboutcircuits.com/threads/using-the-ir2304-s-for-the-first-time-to-make-a-three-phase-inverter.155886/#post-1345395

(datasheet and circuit sketch attached to the linked thread)

but I've not had a reply.

I'm wondering if anyone knows from experience if the Vs pin goes between VB and COM? And if someone can elaborate on what the functionality diagram in the datasheet is with reference to?

I believe not what Hin must be pulsed to 'bootstrap' the capacitor, so I don't think I can really test the driver's circuit operation just using a DC source and voltmeter.

Thanks
 

Baluncore

Science Advisor
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You must turn on the low-side mosfet first, so as to charge the capacitor, only then can you turn on and test the high-side mosfet.
Maybe you could drag and drop your circuit for one phase onto your next post.
 
860
16
Thanks Baluncore,

You must turn on the low-side mosfet first, so as to charge the capacitor, only then can you turn on and test the high-side mosfet.
Maybe you could drag and drop your circuit for one phase onto your next post.
That is really strange, how long does the low-side mosfet have to be ON for before I can trigger the high-side?

The circuit is approximately this:

upload_2019-1-16_23-17-17.png


With Vcc being 15V, and the COM being connected to the GND of a raspberry pi, similar for Hin and Lin to the GPIOs.

So do you know if Vs goes to GND when the HO is triggered? or is Vs always Vcc?

Thanks again!


P.S.
I just tried triggering the lower mosfet first, however, I COULDN'T GET IT TO TRIGGER AT ALL!
I was expecting LO to be equal to Vcc, however, it was closer to 0V.
Also I noticed that Hin and Lin went between a couple volts and zero, I was expecting they would just be zero. Perhaps I damaged the chips?

P.P.S. it really bugs me that the output to the load was Vcc, as I would like the mosfet controller to be separate, as I expected it should be.
 

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Baluncore

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That is really strange, how long does the low-side mosfet have to be ON for before I can trigger the high-side?
Just long enough to charge the Vb capacitor. Initially, maybe 10 to 100 microseconds.
When LO goes high, the low-side mosfet is turned on. That pulls Vs to ground and charges the Vb capacitor through the diode from Vcc. That then supplies the capacitor voltage needed later to switch the high-side mosfet gate between off and on.

So do you know if Vs goes to GND when the HO is triggered? or is Vs always Vcc?
You are confused. I wonder what exactly you mean by triggered. Vs goes low when LO is high. Vs is the high-side mosfet source voltage which is the half bridge power output, not a supply.

With Vcc being 15V, and the COM being connected to the GND of a raspberry pi, similar for Hin and Lin to the GPIOs.
Hin and Lin control voltage thresholds are below 0.8 for low and above 2.3V for high. Your Rpi must supply that voltage.
Vcc is selected to be sufficient to fully turn on the mosfet gates.

Also I noticed that Hin and Lin went between a couple volts and zero, I was expecting they would just be zero. Perhaps I damaged the chips?
You must fully control the voltage on the Hin and Lin inputs. If input voltages do not change it is probably because you are not fully controlling them. The internal interlock between the Lin and Hin require those inputs be fully controlled at all times.
It is possible that your power supplies are not functioning as you expect, or that you have a wiring error in your prototype.

While the bridge is idle and not driving the load, you should turn low-side mosfets on, so as to maintain Vb capacitor charge in preparation for the high-side mosfet to be turned on.

P.P.S. it really bugs me that the output to the load was Vcc, as I would like the mosfet controller to be separate, as I expected it should be.
The high voltage supply will usually be significantly greater than Vcc, and often greater than the Vgs breakdown voltage of the mosfet. For higher voltages the supplies must be separate, and the Vb voltage must stay close to, and above Vs by Vcc.
 

Tom.G

Science Advisor
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Take a look at pin 1, labeled LIN. It is connected to HIN.
Pin 2 has the same labeling problem.
Confusion anyone?

upload_2019-1-16_23-17-17-png.png
 

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860
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Take a look at pin 1, labeled LIN. It is connected to HIN.
Pin 2 has the same labeling problem.
Confusion anyone?

View attachment 237415
Ha! You're right! I didn't notice that. This bloody datasheet is a real turkey.
Oh God, I'm so confused now.
 
860
16
Just long enough to charge the Vb capacitor. Initially, maybe 10 to 100 microseconds.
When LO goes high, the low-side mosfet is turned on. That pulls Vs to ground and charges the Vb capacitor through the diode from Vcc. That then supplies the capacitor voltage needed later to switch the high-side mosfet gate between off and on.


You are confused. I wonder what exactly you mean by triggered. Vs goes low when LO is high. Vs is the high-side mosfet source voltage which is the half bridge power output, not a supply.


Hin and Lin control voltage thresholds are below 0.8 for low and above 2.3V for high. Your Rpi must supply that voltage.
Vcc is selected to be sufficient to fully turn on the mosfet gates.


You must fully control the voltage on the Hin and Lin inputs. If input voltages do not change it is probably because you are not fully controlling them. The internal interlock between the Lin and Hin require those inputs be fully controlled at all times.
It is possible that your power supplies are not functioning as you expect, or that you have a wiring error in your prototype.

While the bridge is idle and not driving the load, you should turn low-side mosfets on, so as to maintain Vb capacitor charge in preparation for the high-side mosfet to be turned on.


The high voltage supply will usually be significantly greater than Vcc, and often greater than the Vgs breakdown voltage of the mosfet. For higher voltages the supplies must be separate, and the Vb voltage must stay close to, and above Vs by Vcc.
Thanks for some more insight into the operation and clarification about Vs.
So the Vb cap won't charge unless the LO mosfet has pulled Vs to ground, I didn't realise that, because I always measured Vs as being Vcc, and I was expecting it to be 0V (floating disconnected internally). I.e. there is Vcc volts coming out of the Vs pin on the chip.

You must fully control the voltage on the Hin and Lin inputs. If input voltages do not change it is probably because you are not fully controlling them. The internal interlock between the Lin and Hin require those inputs be fully controlled at all times.
It is possible that your power supplies are not functioning as you expect, or that you have a wiring error in your prototype.

While the bridge is idle and not driving the load, you should turn low-side mosfets on, so as to maintain Vb capacitor charge in preparation for the high-side mosfet to be turned on.
To be clear, I am confident that these voltages were coming from the driver, not the controller. Because I think I remember measuring the voltage of a '0' gpio pin and it was 0V and when I plugged the wire for the Lin or Hin it went to 1.4V or something. (this is just hearsay because I may be mis-remembering)

I'm going to completely rebuild the dirvers and MOSFET setup with some new leaded ICs I've ordered. Because the ones I previously used were surface mount ICs and were very hard to work with. And failing that, I'll might have to sort out using a larger voltage to drive Lin and Hin than the 3.3V coming from the GPIO of the raspberry pi (hopefully not).

Much appreciated
 

Tom.G

Science Advisor
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Because I think I remember measuring the voltage of a '0' gpio pin and it was 0V and when I plugged the wire for the Lin or Hin it went to 1.4V or something. (this is just hearsay because I may be mis-remembering)
1.4V sounds like a floating input. Check that the GPIO pin you connected to is configured as an Output and that there is a pullup to +Supply implemented. The pullup (resistor or transistor) may be internal and programmable or an external one may be needed.

Also check that a connection was really made! Use an Ohmmeter from driver chip pin to raspberry CPU chip pin. That is tough with surface mount stuff. Just the pressure of a meter probe may complete a faulty solder joint. If you have two meters available (and enough hands), measure the GPIO pin and the driver pin voltages at the same time.

Cheers,
Tom
 
860
16
1.4V sounds like a floating input. Check that the GPIO pin you connected to is configured as an Output and that there is a pullup to +Supply implemented. The pullup (resistor or transistor) may be internal and programmable or an external one may be needed.

Also check that a connection was really made! Use an Ohmmeter from driver chip pin to raspberry CPU chip pin. That is tough with surface mount stuff. Just the pressure of a meter probe may complete a faulty solder joint. If you have two meters available (and enough hands), measure the GPIO pin and the driver pin voltages at the same time.

Cheers,
Tom
Food for thought, thanks.

If you both wouldn't mind, I'll draft a new circuit layout, more professional and I'll try and make this next one be 'better', can I post it here when I'm done for both of your peer-review?
Cheers
 

Tom.G

Science Advisor
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Looking forward to it!
 

Baluncore

Science Advisor
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This bloody datasheet is a real turkey.
Oh God, I'm so confused now.
Only the external labels were swapped on the diagram. It makes no difference to the product or terminal identification. The terms are correct throughout the rest of the data sheet.

If you are still confused about the application of the IR2304 or IRS2304 half-bridge drivers you should ask a specific question.

Now you need to test the circuit by controlling the Lin and Hin signals.
Check that you have tied the drain of the low-side mosfet to Vs, the source of the high-side mosfet as shown in the diagram. If you do not do that you will be unable to charge the Vb-Vs capacitor.

When pin Lin is low, Lo will be at Gnd which will turn off the low-side mosfet.
When pin Hin is low, Ho will be at Vs which will turn off the high-side mosfet.
Do not take pins Lin and Hin high at the same time.
When pin Lin is high, Lo will be at Vcc which will turn on the low-side mosfet which will charge the Vb-Vs capacitor.
When pin Hin is high, Ho will be at Vb which will turn of the high-side mosfet.
 

Baluncore

Science Advisor
6,218
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And failing that, I'll might have to sort out using a larger voltage to drive Lin and Hin than the 3.3V coming from the GPIO of the raspberry pi (hopefully not).
According to the datasheet 3.3V is sufficient to drive the half-bridge controller.
Make sure the Rpi outputs you use are able to pull the output voltage up. If the outputs are open drain outputs they will require a pull-up resistor to the output logic voltage supply.
 
860
16
Only the external labels were swapped on the diagram. It makes no difference to the product or terminal identification. The terms are correct throughout the rest of the data sheet.

If you are still confused about the application of the IR2304 or IRS2304 half-bridge drivers you should ask a specific question.

Now you need to test the circuit by controlling the Lin and Hin signals.
Check that you have tied the drain of the low-side mosfet to Vs, the source of the high-side mosfet as shown in the diagram. If you do not do that you will be unable to charge the Vb-Vs capacitor.

When pin Lin is low, Lo will be at Gnd which will turn off the low-side mosfet.
When pin Hin is low, Ho will be at Vs which will turn off the high-side mosfet.
Do not take pins Lin and Hin high at the same time.
When pin Lin is high, Lo will be at Vcc which will turn on the low-side mosfet which will charge the Vb-Vs capacitor.
When pin Hin is high, Ho will be at Vb which will turn of the high-side mosfet.
Okay, this is a very useful sanity reference for me, when I've built the new circuit. And I'll endevour to ask specific questions and provide concrete details if issues persist. (I'll need to read through my ad hoc notes to see if I still have confusion.)

I think the safest thing to do would be to totally scrap my existing MOSFET wiring and start from scratch.

Looking forward to it!
I've just knocked it up, please tell me what you both think, hopefully you can open the picture in full size to see all the values.
inverter circuit.png

Side note, I'm quite nervous about the inductors I've made. I bought three of the largest ferrous toroids I could from ebay, I think they were about 5-10cm in diameter from memory, and wound about 80 turns on each (measured three equal lengths of silicone insulated wire). I know they saturate at a couple amps at 50Hz, but I'm hoping they'll be good at several Khz PWM.

Thanks heaps fellas!
 

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Baluncore

Science Advisor
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I can't actually resolve any of the details in that image.
PF does tend to blur what are otherwise clear .png images. You may need to post a more detailed image, in anticipation that PF will sacrifice the quality while increasing the size. PF seems to do that when converting from a compact B&W, or 4 bit colour image, to 24 bit colour.
 
860
16
I can't actually resolve any of the details in that image.
PF does tend to blur what are otherwise clear .png images. You may need to post a more detailed image, in anticipation that PF will sacrifice the quality while increasing the size. PF seems to do that when converting from a compact B&W, or 4 bit colour image, to 24 bit colour.
upload_2019-1-17_17-21-49.png

upload_2019-1-17_17-22-13.png

upload_2019-1-17_17-22-36.png

The DC bus is 36V.
 

Attachments

860
16
I can't actually resolve any of the details in that image.
PF does tend to blur what are otherwise clear .png images. You may need to post a more detailed image, in anticipation that PF will sacrifice the quality while increasing the size. PF seems to do that when converting from a compact B&W, or 4 bit colour image, to 24 bit colour.
inverter circuit.png

Or maybe this will work if you don't want to splice the three together.
 

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Baluncore

Science Advisor
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1. You do not have to insert the picture into the post, you can simply attach it.

2. The IR2304 is a low current gate driver so you should select a mosfet with a low gate capacitance. That mosfet will need a fast parallel flyback diode as it is driving an inductive load.

3. The resistor between the driver and the mosfet gate can be 22 ohm. It is there primarily to prevent a parasitic ultrasonic oscillation between the driver and the mosfet gate which might damage the gate and cause electrical noise. If the resistor value is too high it may limit the driver current to the gate during transition.

4. I would not bother with the 1 MEG resistor as the driver will clamp the gate voltage.
 
860
16
1. You do not have to insert the picture into the post, you can simply attach it.

2. The IR2304 is a low current gate driver so you should select a mosfet with a low gate capacitance. That mosfet will need a fast parallel flyback diode as it is driving an inductive load.

3. The resistor between the driver and the mosfet gate can be 22 ohm. It is there primarily to prevent a parasitic ultrasonic oscillation between the driver and the mosfet gate which might damage the gate and cause electrical noise. If the resistor value is too high it may limit the driver current to the gate during transition.

4. I would not bother with the 1 MEG resistor as the driver will clamp the gate voltage.
Ah, I should have remembered about attaching it, I was thinking it attached by drag and drop, woops.

Excellent, thanks so much for the feedback.

I am currently using IRF3205 NMOSFETs, what am I looking for on the datasheet to this end? And what range should I be hoping for?

The datasheet for the 3205 says:
total gate charge: 146 nC, gate to source charge 35 nC, gate to drain charge 54 nC
input capacitance 3247 pF
output capacitance 781 pF
reverse transfer capacitance 211 pF
reverse recovery charge 143-215 nC

...?

I was using some 1N5817 1A Shottkey diodes. Could you please suggest some? (Googling suggests: 1N4001?) Does the flyback diode need to be directly on-top of the MOSFET pins, or could it be on the circuit board of the chip?

Okay, I'll go with 22 Ohm gate resistors and not worry about the 1M Ohm

Much appreciated
 

Baluncore

Science Advisor
6,218
1,812
I was using some 1N5817 1A Shottkey diodes. Could you please suggest some? (Googling suggests: 1N4001?) Does the flyback diode need to be directly on-top of the MOSFET pins, or could it be on the circuit board of the chip?
All mosfets have an intrinsic body diode, some have a fast Schottky diode included in the package. If they do not include the diode you will have to place one as close to the mosfet as possible. The common 1N4001 will NOT survive the inductive application. What inductor current do you expect?

You will need to browse the selection tables provided by mosfet manufacturers. Mosfets for motor drive applications will include a fast recovery schottky diode matched to the mosfet current and speed.

The flyback diode should be schottky so it will conduct before the body diode. It must be fast so there is minimum transition overshoot, which also explains why it must be close to the mosfet. The body diode in the IRF3205 may be sufficient, but I would expect to find a better mosfet in the selection tables.

The IRF3205 has a high capacitance because it's high current requires a large area die. Select a lower current device and you will find it will switch faster. Also, consider later generation mosfets. Alternatively, select a higher current half bridge driver.

Again, browse the selection tables provided by the mosfet manufacturers. Learn to read the data sheets.
Also, see the selection filters available on suppliers websites such as digikey, mouser, element14, RS etc.
 

Tom.G

Science Advisor
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1) The IRF3205 data sheet shows Trr (reverse recovery time) as 104ηS. That would seem adequate for the motor since the schematic shows capacitors across the motor windings. Depending on the motor load current, the series inductors could cause trouble if they are less than about 6μH. That would put the peak of the first ringing pulse at less than the switching time of the body diode. I don't have a 'good' guess for the inductors, but it sure feels like the inductance of 80 turns on a toroid would be substantially higher, in the range of milliHenries.

2) Do not use electrolytic capacitors for the Boost cap, their high leakage current will limit the maximum pulse width.
2a) As @Baluncore said, drop the 1M resistors in the gate circuit; they are effectively the same as leakage current. (just don't turn on the 36V power without the driver chips being functional)

If you wish to calculate the needed value of the Boost caps, there is an explanation and formula on pg.6 of:
https://www.infineon.com/dgdl/Infineon-HV_Floating_MOS_Gate_Drivers_AN978-AN-v01_00-EN.pdf?fileId=5546d462533600a40153559f7cf21200

They talk about a slightly different chip but the basics are the same.

Cheers,
Tom
 

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