Full-bridge Gate driver doing funny buisness (H-Bridge Circuit) - Page 1
Forum section: electronics / projects

author: willPowell
author_rank: Contributor
timestamp: February 07, 2022, 03:26:10 pm
content: Hi everyone,I am having a rather frustrating day trying to figure out what is wrong with a H-Bridge circuit I have built- please see photo schematic attached.The full-bridge gate driver (https://docs.rs-online.com/3b00/0900766b814bf823.pdf?bcs-agent-scanner=9daa66bc-6612-6846-bc6d-a72e5dfa3912) behaves as expected when the secondary 30V supply is off - i.e. the right high-side and left low-side show a gate-source voltage of 10V whilst the other two Fets have no Gate-Source voltage.However, when I turn on the 30V supply it will short the supply if GNDs are connected. If they have separate GNDs, then the gate-source voltage is sunk to zero.Any ideas much appreciated.Otherwise, if you know a full-bridge gate driver that would work in this setup please let me know.Thanks,Will

author: jmelson
author_rank: Super Contributor
timestamp: February 07, 2022, 04:53:47 pm
content: UGH! I worked with the HIP4080 20 years ago. They were massively overspeced, and failed at much lower voltage than the datasheet showed. But, I see you are putting 12 V into the inputs. You need to allow the bootstrap capacitors to charge, and that requires you to not ram the modulator to full-scale output.Try putting a small voltage at the input and then turning it up slowly. The HIP4080 is NOT a gate driver IC, it is a full class-D audio amp on a chip (except for extranal FETs).Jon

author: willPowell
author_rank: Contributor
timestamp: February 07, 2022, 05:12:54 pm
content: Oh dear, doesn't sound like I've picked a good un. I have tried increasing primary slow slowly but no improvements sadly.Can you recommend a plug and play gate driver that will work for my case?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 07, 2022, 08:29:15 pm
content: Are you sure you aren't confusing it with something else? HIP4080A is quite clearly a gate driver. It can be used for class-D amps, but isn't exclusive to them.https://www.renesas.com/us/en/document/dst/hip4080a-datasheetI used HIP2101 some years ago on a 24V battery supplied system, works fine. Same cautions as anything, mind the peak voltage etc. The internal charge pump is fantastic for being able to drive 100% duty cycle without worry.OP: please show full schematic and layout, and how it's lashed up on the bench if applicable. The datasheet clearly says +/-2V transient between GNDs, so it is perplexing (or disturbing) that you have the load GND wired optionally. And no load bypass caps are shown. It takes very little inductance to develop this kind of voltage!Tim

author: Benta
author_rank: Super Contributor
timestamp: February 07, 2022, 08:52:53 pm
content: I remember the HIP4080 well, and it's indeed a gate driver. An extremely good one at that. And that's the problem.Its edge speeds are so fast, that excessive ringing can occur. Layout is very tricky, forget everything about a solderless breadboard. You need a real good PCB with proper layout.IIRC, Intersil acknowledged the issue and brought out application guides, also recommending low-ohm resistors in some signal/power paths.You'll need to search for old Intersil documentation. The canned data sheets from RS are not enough.

author: jmelson
author_rank: Super Contributor
timestamp: February 08, 2022, 12:54:54 am
content: Quote from: willPowell on February 07, 2022, 05:12:54 pmFor a simple gate driver, I have used the IR2113 (you need 2 for a full bridge). But, you will probably need a bit of diode-RC delay to prevent both transistors from turning on at the same time. And, you can't turn the high-side transistor on 100% of the time, as the bootstrap caps need time to charge whenthe common point (source of high-side transistor) goes low.Jon

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2022, 01:28:33 am
content: There's the whole family of IR2xxx with various features, including none, fixed or programmable dead time, single or dual inputs (when single, the outputs are complementary, minus dead time), or even self-oscillating (can be used to make a very simple resonant power supply for instance). Take your pick. But:Quote from: willPowell on February 07, 2022, 05:12:54 pm...you haven't defined anything about your case, so we have utterly no way to judge that.Tim

author: xavier60
author_rank: Super Contributor
timestamp: February 08, 2022, 02:04:33 am
content: Galvanically isolated drivers make PCB layout less critical, I'll use nothing else now after trying a STGAP part.There are lots of parts in the family and it's easy to make a bad choice.I use this half bridge driver,https://au.mouser.com/ProductDetail/STMicroelectronics/STGAP2DMTR?qs=W0yvOO0ixfF%252Bp5Pfo9gPjQ%3D%3DIt might seem expensive until compared it to the IR2113 for example.https://au.mouser.com/c/?q=IR2113

author: willPowell
author_rank: Contributor
timestamp: February 08, 2022, 09:47:11 am
content: Lots of information to take in, I am not particularly experienced with electronics.My requirements are:Fast switching circuit (at least 20kHz)For a 30V power supply,Capable of powering a none inductive load of 10k.Controlled by a 3.3V microcontrollerAs simple circuit as possible.Any suggestions much appreciated.

author: willPowell
author_rank: Contributor
timestamp: February 08, 2022, 09:50:24 am
content: Quote from: willPowell on February 07, 2022, 05:12:54 pm...you haven't defined anything about your case, so we have utterly no way to judge that.Requirements above.

author: langwadt
author_rank: Super Contributor
timestamp: February 08, 2022, 10:14:08 am
content: Quote from: willPowell on February 08, 2022, 09:47:11 am30V / 10k = 3mA that's all?

author: willPowell
author_rank: Contributor
timestamp: February 08, 2022, 10:17:25 am
content: Yes only 3mA!

author: langwadt
author_rank: Super Contributor
timestamp: February 08, 2022, 10:31:55 am
content: Quote from: willPowell on February 08, 2022, 10:17:25 amthen your gate drivers and external fets are several orderes of magnitude overkill. A dual opamp, analog switch or a few transistors would do

author: willPowell
author_rank: Contributor
timestamp: February 08, 2022, 10:41:48 am
content: Quote from: langwadt on February 08, 2022, 10:31:55 amYes I know mosfets are rather overkill, but are transistors any better? Unfamiliar with the dual op-amp circuitry, do you have a circuit diagram.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2022, 02:05:28 pm
content: Ah, much easier indeed then!Example:For 3mA out, Rb = 10k is fine, and for 3.3V logic levels, Re = 6.8k will give plenty of capacity. Do not assert A and B at the same time!Plain old 2N3904/6 will do 30V 3mA no problem, and may even survive a short circuit condition (faulty load or A & B on simultaneously).Cheers,Tim

author: willPowell
author_rank: Contributor
timestamp: February 08, 2022, 03:26:47 pm
content: This is nice and I can see this working, however, I don't want any voltage drop except from the load (and internally through the transistors/mosfet resistance).The reason why is that my supply is a constant current source which is limited to 3mA so can't afford to have any parallel circuitry.

author: Benta
author_rank: Super Contributor
timestamp: February 08, 2022, 05:28:02 pm
content: If you have the option of using +/- 15 V supply, two Vishay DG419B analog switches would do a great job.

author: jmelson
author_rank: Super Contributor
timestamp: February 09, 2022, 03:57:58 am
content: Quote from: T3sl4co1l on February 07, 2022, 08:29:15 pmWell, my memory was a bit faded. I had to do 2 days of hacking to get my Win95 virtual machine running again so I could pull up the schematics of a servo amp I built in 1997 using the HIP4080. It did a lot less of the analog stuff than I remembered. I did have an outboard triangle wave generator, but then the 4080 had an analog comparator at the input, so you fed the triangle wave in to IN+ and the analog signal into IN-, and it did all the dead time and gate driving. But, I was blowing lots of 4080 chips at 69 V DC, and so finally rebuilt the amps with the IR2113 and haven't blown a single one in 33 years! This design did not use the bootstrap scheme, as I needed a charge pump to run the high-side overcurrent sensing anyway, so that was also used to power the high-side gate drivers.Jon

author: jmelson
author_rank: Super Contributor
timestamp: February 09, 2022, 04:04:03 am
content: Quote from: willPowell on February 08, 2022, 09:47:11 amAh, for 3.3 V input, then the IR2181 is a good half-bridge driver.Jon

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 09, 2022, 04:34:37 am
content: Quote from: jmelson on February 09, 2022, 03:57:58 amAha, that makes more sense.And, that would do it, fairly low margin; if that's unregulated, just a high-line swell might be enough to cook it! Let alone stray inductance in the inverter, which, indeed for such a fast driver, can easily be a problem, even with the modest performance MOS available in the 90s.Dang, is the HIP4080 really that old? It's got fantastic specs even today.Tim

author: CaptDon
author_rank: Super Contributor
timestamp: February 09, 2022, 02:29:53 pm
content: How does your drive signal allow dead time from the time you switch off in one polarity until the time you switch on in the opposite polarity?? You need some dead time or shoot-through is inevitable!!

author: jmelson
author_rank: Super Contributor
timestamp: February 09, 2022, 04:23:11 pm
content: Quote from: CaptDon on February 09, 2022, 02:29:53 pmRight! Using the IR2113 in my older servo amps, I used an RC to delay the command to the driver, and then have a diode across the resistor to make the turn-off faster than the turn-on. I just shipped serial # 499 of that design.Jon