problem 5 level H-bridge inverter

[Jakie Ee]

hi i face problem with my 5 level H bridge inverter
it cannot receive input voltage higher than 3v
if the input higher than 3 voltage it will short circuit
the output also cnnot show 5 level step voltae output

i am using irfz44r power mosfet with ir2101 gate driver
help, please

 

[skylarks]

ir2101 can be used for 3 to 12volt in put without any problem. What do you mean by 5 level. and what gets short circuit. the H bridge require 4 in puts in particular way.

 

[FvM]

I'm unable to recognize a 5-level inverter in your schematic. To work as a multi-level inverter, it would need isolated power supplies, and a different way to drive the gates across the potential differences. As shown, it's simply shorting H-bridge outputs.

Reconsider!

 

[--BawA--]

yes fvm is right , u have to use 2 isolated dc bus to make 5 level inverter,

 

[Jakie Ee]

- - - Updated - - -

thx for the reply..
i am using different power supplies...
as for input.. each gate driver has non inverting signal at Hin and inverting signal at Lin..
pwm at first h bridge is different from second one.only square wave is same
i mean i actually already has 6 input to the h bridge...
is there a problem in my gate driver design??

 

[FvM]

According to your schematic, you are not using different power supplies, because "VCC" and "VDD" have a common ground. The grounds must be separated and each IR2101 ground must be connected to the separated grounds respectively. So at least one of both control voltages needs optical isolation.

 

[Jakie Ee]

same ground is just in schematic. sorry,im in hurry when i draw this.
in real experiment, i am using different power source and of course different grounding..it the same case also for gate driver..

do i need separate source for each gate driver??
does it mean i need six different input??

 

[FvM]

same ground is just in schematic. sorry,im in hurry when i draw this.
in real experiment, i am using different power source and of course different grounding..it the same case also for gate driver..

Then report what you exactly did in your real circuit. According to your initial post you did something wrong, I'll stop guessing for the time being.

 

[Jakie Ee]

ok2..here the details..
1. no error in input signal because when i used voltage controlled switch, it works perfectly..i used 100us deadtime to prevent shoot-through
2. problem started when i connect mosfet with gate driver..the input cannot be increased more than 3v
3. each h-bridge has different power source
4. i use same power source for every gate driver<--- problem in here maybe?? but why??

 

[FvM]

Please refer to my previous comment

each IR2101 ground must be connected to the separated (bus voltage) grounds respectively. So at least one of both control voltages needs optical isolation.

Not said explicitely, but separate IR2101 grounds also imply separate gate driver power supply. It should be also clear, that driving signals must be referenced to the IR2101 ground. Isolated IR2101 ground and power supply also means insolated logic signals.

 

[Jakie Ee]

ok..

how bout ground from controller?..does it need to connect to gate driver ground?
i found one thread bout paracitic capacitance in mosfet and 1k resistor between the gate and source of each MOSFET.
can u clarify this?

 

[FvM]

how bout ground from controller?..does it need to connect to gate driver ground?

Yes. Or more exactly, the driving signal for IR2101 must have a common ground with the gate driver. As you have one controller ground and two separated gate driver grounds, you need optical isolation or a similar means.

i found one thread bout paracitic capacitance in mosfet and 1k resistor between the gate and source of each MOSFET.

Not related to the discussed problem. IR2101 can be expected to drive the capacitance and don't need a pull-down resistor for operation.

 

[Jakie Ee]

thx u so much...very helping information.

one last question..what is the difference between bootstrap supply and floating gate supply? which one is better..?

 

[FvM]

Bootstrap supply is restricted in several regards
- maximum high side duty cycle < 1
- start-up behaviour can be problematic in some applications

For your application, it's a reasonable and straightforward approach to use four isolated ("floating") gate supplies and opto-isolated gate drivers.

 

[Jakie Ee]

so i need 4 gate drivers with 4 optocouplers and 4 voltage supply ..right??

can i use bootstrap supply instead?. ..so i can reduce the components in circuit

 

[FvM]

I think, I already sketched the wiring of the bootstrap version in the previous posts. But you should design the circuit yourself.