Buck convertor my circuit has been damaged

• Aug 29, 2017

• #1

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baby_2

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Hi,
Here is my circuit

I use a IGBT(VCE>800 , IC=35) instead of BJT transistor with a IGBT driver(VCC=15v). I want to get a 1A current output with switching frequency 50khz (duty cyle less than 15%).
However after I inject 220VAC as input my IGBT gone and after that all my circuit behind of gate such as IGBT driver , PWM generator has gone too.
what is my mistake?

 

• Aug 29, 2017

• #2

KlausST

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Hi,

what is my mistake?

Click to expand...

* wrong PCB layout
* wrong device selection
* wrong schematic
* ..

Klaus

 

• Aug 29, 2017

• #3

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mtwieg

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Most likely problem is with the gate drive circuit, which isn't shown. Show your full schematic if you really want help.

Also consider testing with a lower voltage/current supply, rather than just plugging it into the wall first.

 

• Aug 29, 2017

• #4

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baby_2

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Thanks a lot for your comment
Here is my gate driver (10 ohm resistor is series with gate) and I make a clear and exact pwm wave form with my micro-controller

 

• Aug 29, 2017

• #5

KlausST

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Hi,

What is "TC442"?
Without power supply it won´t work.
Without capcitors it won´t run stable.
Without proper layout it won´t run stable.

I´l be back when there is useful information.

Klaus

 

• Aug 29, 2017

• #6

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baby_2

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Sorry , it is TC4426,https://www.mouser.com/ds/2/268/20001422G-967549.pdf
I set 15v power for TC4426, I use something like figure 4-1 in datasheet and it's output voltage is:

 

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• Aug 30, 2017

• #7

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nikhilmahasvar

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What is your output voltage ?

 

• Aug 30, 2017

• #8

FvM

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TC4426 is a low side driver. How is the driver supply connected input DC and how the pwm signal to the gate driver?

You need a floating power supply for the driver and isolation for the pwm signal.

 

• Sep 1, 2017

• #9

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baby_2

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Hi,
Thanks for your contributions
Here is my IGBT driver circuit ( I applied 15v for biasing the driver and also a 10ohm series resistor in gate pin) (TC4426)

the PWM generates with micro-controller that you can see the output pwm wave form after passing the driver (at gate) here

 

• Sep 1, 2017

• #10

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baby_2

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My output voltage is 40volt

 

• Sep 1, 2017

• #11

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mtwieg

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As expected, the problem is with the unsuitable gate driver. As FvM stated already, the TC442 is a low side gate driver, but you're using a high side switch. Consider using a proper high side gate driver (IR2110 family), or using a P channel device with proper driver circuits.

 

• Sep 1, 2017

• #12

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CataM

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mtwieg said:

Consider using a proper high side gate driver (IR2110 family), or using a P channel device with proper driver circuits.

Click to expand...

Or, he can move the IGBT in the low side and still use the current low-side gate driver, but then, the load will float.

 

• Sep 1, 2017

• #13

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baby_2

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Thanks for your recommendation and explanation
I've used 2101 with this circuit.


I inject a %20 PWM voltage (20% on) but I get output voltage ( I put a resistor at the output) with average of 10v!! and when I change duty cycle to %80 I get 7V across the output resistor.

 

Last edited: Sep 1, 2017

• Sep 2, 2017

• #14

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baby_2

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Hi,
My problem is that I can't get less voltage with changing pwm duty cycle less than 10% but as I know with duty cycle between 0 to 100% I should get the minimum and maximum voltage across the load. it means my MOSFET doesn't switch on or off completely.

 

• Sep 2, 2017

• #15

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nikhilmahasvar

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In buck converter it is not advisable to go for less than 10% duty cycle. Device strain will be substantially higher.

 

• Sep 2, 2017

• #16

FvM

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In buck converter it is not advisable to go for less than 10% duty cycle. Device strain will be substantially higher.

Click to expand...

Don't agree as a general rule. Buck converters with low duty cycle are less efficient, switching losses (and "device strain") are proportional to input voltage multiply output current in the first order. But there are cases where 5 % or even lower duty cycle is appropriate for designed fixed output voltage. Furthermore it's just normal to have switchers with variable output voltage starting at zero.

A bootstrap gate driver as used in the present circuit will however never work with 100 % duty cycle, and it may also have problems with very low duty cycle and startup without a resistive load. The driver is intended to be used with synchronous (transistor/transistor) switchers and has problems with transistor/diode switchers.