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Help with IRS2184 Half Bridge Driver Chip

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IamSmooth

Fri Sept 25 2009, 01:06AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I am testing this chip

It is the IR IRS2184 Half-Bridge Driver.

I am using Vc = 10v.
I have 0.1uf ceramic cap between Vc and COM. COM goes to ground.
I have 0.1uf ceramic cap between Vb and Vs.
I have the diode going between Vc and Vb.
SD is connected to 5v

I have a test LED connected with 500ohms to LO going to ground
I have a test LED connected to HO with 500ohms going to Vs (I also tried going to ground).

I measure 9.1v on Vb
When I toggle IN the LO output toggles the LED on and off. When IN is low, LO is high (LED is on). However, I get no action with the HO LED. I measure 7.5 volts on HO, but the LED does not light. I see in the diagram that Vs is suppose to be the floating return for HO, but I don't know why it is not working.

Any help?

EDIT:

Ok, I got something working, and maybe this is how it should be...
I measured the voltage on Vs and found it to be 10v, so the LED would not light because there was not difference between Vb and Vs.

I put a larger capacitor between Vb and Vs. I used 100uf. I also connected a 1k resistor from Vs to ground. So right now, each HO and LO output goes to an LED/resistor. The LO goes to ground; the HO goes to Vs, and now Vs also has a connection to ground.

When I hit IN with 5v, the LO output LED goes out like it should; the HO output flashes for a moment and goes out. If I toggle IN, I get an alternating flash. I was expecting the HO output to stay on continuously if I raise IN.

Steve Conner

Fri Sept 25 2009, 08:08AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

These driver chips can't keep the high side on continuously. The charge in the bootstrap capacitor runs out after a second or so. In use, you typically limit the duty cycle to 99% so the bootstrap is always getting charged. Search the forum and archives, I'm sure I've answered this question at least once before.

IamSmooth

Sat Sept 26 2009, 03:01AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I found your reference here:

So I've put together the TL494 PWM chip. I am driving the IRS2184 half-bridge gate drive chip which is lighting LEDs on the HO and LO outputs. The LEDs drain their current through 400 ohm resistors. I have the frequency close to 250kHz with 50% duty. Vc = 10v. The bootstrap capacitor is 10uf.

What I would like to know is what is causing the ringing on the LO output in the picture. Is this the stray capacitance on the breadboard? Will this disappear on printed circuit boards; and , will this be a problem driving mosfets for an induction heater? What can I do about this?

First picture is TL494 pulses
Second picture is HO output waveform
Third picture is LO output waveform
Fourth picture is breadboard

teravolt

Sat Sept 26 2009, 05:19AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

you might use 2 1nf caps in place of the gates insted of the leds or replace the leds with a half bridge to see what results you can get. I used a cuple of thease types of chips for the gates on a full bridge on Steve Ward's new drsstc board. it worked great and it even gave me a little dead time. the FET's I used are some of those 2.1mohm 7-D2PAK

Dr. Dark Current

Sat Sept 26 2009, 08:32AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Beware of these chips, especially when driving inductive loads.
When the floating supply ground "flies" over 5V below zero, usually from non-perfect layout of the bridge (interconnection inductances), the chip turns both high and low outputs on. I think you can guess what happens.

teravolt

Sat Sept 26 2009, 05:16PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Dr. Kilovolt have you tried these chips an have had lockup? I have herd this happan with older versions of this type of chip but newwer versions have dead time and circuitry that prevents lockup. Cirtanly you don't want to use any large igbt's for this. what do you think

BowlingSuperior

Sun Sept 27 2009, 12:31AM

Registered Member #1121 Joined: Thu Nov 15 2007, 02:34AM
Location:
Posts: 4

Just FYI - John DeArmond has a DIY-style induction heater using a similar chip that you are experimenting with - schematics, etc are posted:

Looks like he has a working design.....

- Bruce

IamSmooth

Sun Sept 27 2009, 05:46AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

Yes. I am familiar with these designs. I am slowly building my knowledge working with these chips. I am going to try the IRS21844 in order to add some deadtime. Once I am happy with the waveform and know that both signals are not above zero at the same time I will add the mosfets.

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