H bridge voltage amplitude problem

Thread Starter

sorinn1987

Joined Mar 22, 2021
7
Hello to all members, this is my first post on this forum; I'm working on a H bridge setup to drive the primary coil of a transformer. My setup, 2 signal generators, one putting out a normal and inverted square wave for IN A and IN B inputs and the other a normal square ware for PWM input of a VNH2SP30 H bridge module. This module is fed 12 V on motor input. The problem is that my voltage amplitude on the output of the H bridge is only 5 volts. I took a series of screenshots of my oscilloscope. Previously I used a H bridge based on IR2104 and IRFP460 mosfets , and swap it with the VNH2SP30 module, hoping the issue was with the H bridge, but I get the same problem. When shorting the output leads of the H bridge it only takes 0.1 amps from the power source. Thank you.
 

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shortbus

Joined Sep 30, 2009
8,469
A schematic is a better thing to display. But from what you seem to be doing, what mosfets are being used? The module on it's own with not mosfets(switching devices) will only give/output the gate drive voltages.
 

KeithWalker

Joined Jul 10, 2017
1,681
The module has built-in over current protection. That is why yo only get a small current flowing when you short the output.
Why are you putting square waves into the IN A and IN B inputs? They are for setting the motor direction and braking. They should be steady logic levels. That is probably what is causing the odd behavior.
 

Thread Starter

sorinn1987

Joined Mar 22, 2021
7
The drive circuit was initially designed, not by me, to drive a H bridge based on IR2104 driver and IRFP460 MOSFETs, I have attached the schematic of the drive circuit from above and the initial H bridge I used with it. The input signals going to pins 2 (PWM IN) of IR2104 is the one from oscilloscope screen titled IN.A and IN.B input, the input signals going to pins 3 (SD - shut down) of IR2104 is the one from oscilloscope screen titled PWM input. Does the way the circuit drives the H bridge based on IR2104, make any sense ? I have had the same problem with low voltage (5v) at H bridge output as with my H bridge used in the initial post. I would prefer to use the second H bridge as it take more voltage. Thank you.
 

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Thread Starter

sorinn1987

Joined Mar 22, 2021
7
That whole schematic makes no sense. What exactly are you wanting/trying to do?
I'm trying to drive a primary coil whit an alternating current, where I can vary the frequency and the on/ off time, without being dependent on the operating frequency for the h bridge to work, I'm referring to the bootstrap circuit.
 

KeithWalker

Joined Jul 10, 2017
1,681
I'm trying to drive a primary coil whit an alternating current, where I can vary the frequency and the on/ off time, without being dependent on the operating frequency for the h bridge to work, I'm referring to the bootstrap circuit.
I agree with Shortbus. I have no idea what you are trying to do, or why. You initial question was about using a VNH2SP30 H bridge module. That is not what is shown in your diagram.
What is the transformer that you are trying to drive? What impedance does it present to the circuit? What is connected to the transformer secondaries?
 

Thread Starter

sorinn1987

Joined Mar 22, 2021
7
I agree with Shortbus. I have no idea what you are trying to do, or why. You initial question was about using a VNH2SP30 H bridge module. That is not what is shown in your diagram.
What is the transformer that you are trying to drive? What impedance does it present to the circuit? What is connected to the transformer secondaries?
I want to drive a step up transformer 1:10 , ferrite core ETD49, input at 12 V at 1000 Hz, primary winding dc resistance 0.044 OHMs, current around 11 amps, secondary resistance 5.32 OHMs. I do not know the impedance, My initial setup was the schematic I posted, I tried a VNH2SP30 H bridge to check if my H bridge was at fault. Thank you.
 

KeithWalker

Joined Jul 10, 2017
1,681
I want to drive a step up transformer 1:10 , ferrite core ETD49, input at 12 V at 1000 Hz, primary winding dc resistance 0.044 OHMs, current around 11 amps, secondary resistance 5.32 OHMs. I do not know the impedance, My initial setup was the schematic I posted, I tried a VNH2SP30 H bridge to check if my H bridge was at fault. Thank you.
Try running your circuit with a resistive load and measure the voltage waveforms generated. I think you might get close to 12V!
You are experimenting with an unusual combinations of devices, so you are going to have to rationalize your own results. I can't help you there..
 

shortbus

Joined Sep 30, 2009
8,469
I'm trying to drive a primary coil whit an alternating current, where I can vary the frequency and the on/ off time, without being dependent on the operating frequency for the h bridge to work, I'm referring to the bootstrap circuit.
So, will you say that you are trying to make something to make HHO? Is that the end result?

Why would you or anyone think that throwing all different types of IC's into a design of a circuit is going to get the results you want? I won't come right out and tell you your wasting your time on this design(but you are) but will tell you to explore more deeply circuit design.
 

Thread Starter

sorinn1987

Joined Mar 22, 2021
7
Try running your circuit with a resistive load and measure the voltage waveforms generated. I think you might get close to 12V!
You are experimenting with an unusual combinations of devices, so you are going to have to rationalize your own results. I can't help you there..
OK, I will try that, and look to see how others are driving this H bridge. Thank you.
 

Thread Starter

sorinn1987

Joined Mar 22, 2021
7
So, will you say that you are trying to make something to make HHO? Is that the end result?

Why would you or anyone think that throwing all different types of IC's into a design of a circuit is going to get the results you want? I won't come right out and tell you your wasting your time on this design(but you are) but will tell you to explore more deeply circuit design.
HHO is not my primary interest, there are other, "spinoff technologies" , but I'm not going into that here or at this time. I asked for help only for the the common electronics , applied also to inverters. I am looking into how others are driving the H bridge and will try to make a working variant to satisfy my requirement. Thank you for your patience.
 

shortbus

Joined Sep 30, 2009
8,469
HHO is not my primary interest, there are other, "spinoff technologies" , but I'm not going into that here or at this time. I asked for help only for the the common electronics , applied also to inverters. I am looking into how others are driving the H bridge and will try to make a working variant to satisfy my requirement. Thank you for your patience.
Then why not use one of the many existing schematics and designs? For your adjustable frequency you would only then need to change the section that controls the frequency not invent a "whole new wheel">
 
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