Hello all,

I want to drive an H-bridge with HIP4080A. I have looked at the datasheet and Application note but I still have some questions.
1. As I understood from the truth table, I can only switch on diagonal mosfets in the bridge, so I can only have bipolar modulation, however I need to have unipolar modulation so I need to be able to switch on both high side or low side Mosfets. How should I command the driver pins to, for instance, switch high side Mosfets on and low side Mosfets off?
2. I am using Figure 12. in the application note for my design:
https://www.intersil.com/content/dam/intersil/documents/an94/an9404.pdf
How should I design the resistors connected to the gate of each Mosfet and the source of low side Mosfets? Can I just connect them with wires and no resistors?

Regards,
Ata

 

Do you understand "high side switching" in a mosfet? Google it and read about it. That should make let you answer your first question. And if it doesn't Google "shoot thru in mosfet H-bridge", to see why having both mosfets on in the same side of a H-bridge is not a good idea.

Maybe if you explain what you are wanting to do you will get better help. What are you meaning by the terms "unipolar modulation" in the context of what you're doing? The design that you referenced doesn't mean that all of the mosfets can or are all on at one time, if that is what your thinking.

 

Do you understand "high side switching" in a mosfet? Google it and read about it. That should make let you answer your first question. And if it doesn't Google "shoot thru in mosfet H-bridge", to see why having both mosfets on in the same side of a H-bridge is not a good idea.

Maybe if you explain what you are wanting to do you will get better help. What are you meaning by the terms "unipolar modulation" in the context of what you're doing? The design that you referenced doesn't mean that all of the mosfets can or are all on at one time, if that is what your thinking.

Suppose the left leg of H-bridge includes Q1 and Q2 and the right leg includes Q3 and Q4. I know if I switch on both Q1 and Q2 or both Q3 and Q4, shoot through happens. In my question I said both high side OR both low side, so the output of the H-bridge becomes zero. I mean switching on Q1 and Q3 and switching off Q2 and Q4, this way I can have zero output. So instead of only having +Vdc and -Vdc, I want to know how I can get 0 on the output of H-bridge.
Regards,

 

I want to know how I can get 0 on the output of H-bridge.

By not switching either one on. That is the only way to get no(0) output.

 

By not switching either one on. That is the only way to get no(0) output.

Thank you for your response.
I have uploaded the output that I get from the H-bridge inverter. The black one shows the output that I get. As you see when I give "high" to DIS pin, I get zero output but it has a long transient. Also there are spikes in the output. How can I solve these issues. I really appreciate your help.

Mosfet: IRF530
driver: HIP4080A
Bootstrap cap: 22uF
Bootstrap diode: 1N4148
HDEL/LDEL resistors: 100k
VDD/VCC=12V
supply voltage to the bridge=15V
In the application note of HIP4080A, I have not used gate resistors and source resistors from Q2 and Q4 to ground.

Thanks for your help.

 

What is the load on the bridge for the waveforms in #5?

 

What is the load on the bridge for the waveforms in #5?

Right now there is no load and I am just seeing the output with oscilloscope.

 

There are substantial capacitances associated with power MOSFETs. With no load, the capacitance will cause long "tailing" of the waveforms. FETs are also not perfect open circuits when off (see datasheet for drain-source leakage current), so DC offsets are possible. If you want to get a better idea of performance, use at least a resistor. Even 10k would probably make a significant difference to the appearance of the waveforms. 1k would be better, but experiment with a range of values to see the effect. Below 1k you will need to consider the power rating of the resistor used (most common small through-hole resistors are rated for about 1/4 W). Don't use a wirewound resistor because they are inductive.

It is hard to explain the overshoot and ringing without a photo of the way you have built the circuit and have the oscilloscope connected. It may be due to scope ground lead inductance. It is more likely due to inductance in the connections to the power supply and perhaps other wiring. With the fast transitions in FET switching, it is easy to excite resonance between stray inductances and the capacitance of the FETs. For circuits like this, the two wires to the power supply should be either twisted together, or if that isn't possible, fastened together as a pair using cable ties or tape. It the load is remote from the bridge, the wire to the load should also be a twisted pair. Pairing the conductors greatly reduces the effective inductance because the magnetic fields around the conductors are opposite and at least partially cancel when they are close together.

 

There are substantial capacitances associated with power MOSFETs. With no load, the capacitance will cause long "tailing" of the waveforms. FETs are also not perfect open circuits when off (see datasheet for drain-source leakage current), so DC offsets are possible. If you want to get a better idea of performance, use at least a resistor. Even 10k would probably make a significant difference to the appearance of the waveforms. 1k would be better, but experiment with a range of values to see the effect. Below 1k you will need to consider the power rating of the resistor used (most common small through-hole resistors are rated for about 1/4 W). Don't use a wirewound resistor because they are inductive.

It is hard to explain the overshoot and ringing without a photo of the way you have built the circuit and have the oscilloscope connected. It may be due to scope ground lead inductance. It is more likely due to inductance in the connections to the power supply and perhaps other wiring. With the fast transitions in FET switching, it is easy to excite resonance between stray inductances and the capacitance of the FETs. For circuits like this, the two wires to the power supply should be either twisted together, or if that isn't possible, fastened together as a pair using cable ties or tape. It the load is remote from the bridge, the wire to the load should also be a twisted pair. Pairing the conductors greatly reduces the effective inductance because the magnetic fields around the conductors are opposite and at least partially cancel when they are close together.

Thank you for your answer.
I used a 10k resistor as my load. I have uploaded the output here. As you see not only the transient still remains, but also the voltage has not reached zero! I also used 12ohm gate resistors but the result is the same. I have spikes and has not reached zero. Also my supply voltage wires are in pair. Do you think there is something wrong with my design?

Regards,
Ata

 

Do you think there is something wrong with my design?

Is this built on a "bread board" or is it on a PCB, even Vero type one? Bread boards and mosfets usually don't play well together.

How far from your mosfets is the driver? A driver should be as close to the mosfets as possible, ideally within 1inch/25mm, less is better.

 

Is this built on a "bread board" or is it on a PCB, even Vero type one? Bread boards and mosfets usually don't play well together.

How far from your mosfets is the driver? A driver should be as close to the mosfets as possible, ideally within 1inch/25mm, less is better.

Well everything is on the breadboard! So you think that causes spikes?

 

As I said previously, without a schematic and some photos of the way the circuit is built trying to determine the exact cause of the spikes is very difficult, but there is no question that inductance is an issue.

Do you have adequate local bypass capacitors for the gate driver and the supply for the H-bridge? The former should have at least 100 nF (ceramic) on very short leads as close as possible to the IC, and preferably 10 µF or more of electrolytic (aluminum is usually OK, tantalum is good) nearby. The H-bridge itself should have similar decoupling but a larger bulk capacitor such as a good quality low-ESR aluminum electrolytic of 100 µF or more near the bridge. Ceramic capacitors should be as close to the FETs as possible, again on short leads. It would be appropriate to have two ceramic caps, one for each side of the bridge, if the high-side FETs are not very close together.

And, again, as I said previously, try some lower value resistors for a load.

When posting scope images, try to set the vertical gain as high as possible while making sure everything is on-screen, and set the horizontal so there are only one or two full cycles. When you don't make use of the space on the screen it is hard to resolve what is going on. Move the trigger toward the left hand side of the screen if necessary to show a full cycle nicely. We also need to know what signals we are being shown.

 

Well everything is on the breadboard! So you think that causes spikes?

Well every thing I've ever seen suggests not to do it. A bread board has way more inductance than a short wire. Let alone the capacitance between tracks. And many times mosfets don't make good contact in the bread board.

 

Hi Atagkh;
I suspect you really want to use 2 "Half Bridge" MOSFET drivers.
I suggest using IR2184.
See an example circuit that uses them:
http://www.redrok.com/led3xassm.htm#c3schematic
I have been using this circuit for over 20 years.

Technically you could drive just the High Side pair of MOSFETs but not continuously. The gate drive circuit will run out of charge, eventually. So the low side MOSFETs must be periodicallyON to charge pump the high side driver flying capacitor.

I suspect IR2184 will work nicely for you.

 

Hi Atagkh;
I suspect you really want to use 2 "Half Bridge" MOSFET drivers.
I suggest using IR2184.
See an example circuit that uses them:
http://www.redrok.com/led3xassm.htm#c3schematic
I have been using this circuit for over 20 years.

Technically you could drive just the High Side pair of MOSFETs but not continuously. The gate drive circuit will run out of charge, eventually. So the low side MOSFETs must be periodicallyON to charge pump the high side driver flying capacitor.

I suspect IR2184 will work nicely for you.

Thanks for your suggestion! I found IR2104 in my devices and started using it. I can command the Mosfets to get the desired output from H-bridge (-Vdc,0,+Vdc), however the problem is that there are some spikes in the output and the voltage is not smooth! I mean I can see small oscillations in the output voltage. I have uploaded the output here. Is it possible to get smoother voltage without these spikes? Also I have implemented the circuit on a breadboard! And in order to prevent shoot-through, before starting the mosfets at each loop, I switch off all of them for a moment.
These are my circuit specifications:
Mosfet: IRF530
driver: IR2104
Bootstrap cap: 1uF
Bootstrap diode: 1N4148
MOSFET gate resistors: 47 ohm
supply voltage to the gate driver=15V
I have also used a 10uF capacitor between VCC and ground of each gate driver.

 

Thanks for your suggestion! I found IR2104 in my devices and started using it. I can command the Mosfets to get the desired output from H-bridge (-Vdc,0,+Vdc), however the problem is that there are some spikes in the output and the voltage is not smooth! I mean I can see small oscillations in the output voltage. I have uploaded the output here. Is it possible to get smoother voltage without these spikes? Also I have implemented the circuit on a breadboard! And in order to prevent shoot-through, before starting the mosfets at each loop, I switch off all of them for a moment.
These are my circuit specifications:
Mosfet: IRF530
driver: IR2104
Bootstrap cap: 1uF
Bootstrap diode: 1N4148
MOSFET gate resistors: 47 ohm
supply voltage to the gate driver=15V
I have also used a 10uF capacitor between VCC and ground of each gate driver.

I don't think you will be able to eliminate the spikes on a breadboard.
These drivers are quite fast switchers.
You may not see these spikes if the load resistor is much lower in value.
The spikes may also be somewhat reduced by using a capacitor across this lower value load resistor.
There is no substitute for a well made low impedance power plane.
For test purposes, you may want to directly solder to a copper ground plane. We often call this "Dead Bug" construction. Yes this can look crude but is quite effective.
We often see experimental circuits built this way. They often perform better than a real PC board layout.
redrok