ir2110 problems

SgtWookie

Joined Jul 17, 2007
22,210
Post the schematic of your circuit (not just copied out of the datasheet - YOUR circuit with all the values you used) and the layout of your circuit, or photos of the layout.
 

praondevou

Joined Jul 9, 2011
2,942
What is purpose of the diodes in parallel with the 22 ohm resistors?
They provide a fast turn-off of the MOSFETs. The gate is being charged through the 22R resistor and discharged through the diode (and partially through the resistor when the diode stops conducting, but at this moment the MOSFET has already turned off)
 

SgtWookie

Joined Jul 17, 2007
22,210
It's necessary for the MOSFETs to get some "extra help" in turning off quickly, as an idiosyncrasy of MOSFETs is that they turn ON more quickly than they turn OFF.

This is a real problem in H-bridges, as one side (high or low) needs to be turned off before its complement turns ON, or there will be a "shoot through" condition; where the power supply is shorted out via the path through the high and low side MOSFETs.

The resistor is necessary as a "snubber" to keep the MOSFET gate from "ringing" excessively. The wire from the driver to the MOSFET gate has inductance, and the MOSFET gate acts as a small capacitor. This creates a series LC circuit that will ring like a bell struck with a hammer when the gate toggles from one state to the other.
 

Thread Starter

stylediva

Joined Dec 6, 2011
72
sorry for the mistakes in connection..actually i 4got to draw that connection.. i have done all the connections..plz tell me that all the values of the capacitors that i m using are right or is there anything to change??..i am applying 5vp-p. and i m giving PWM from AVR microcontroller..and inverting PWM from schmitt trigger thru RC network at its input..i m attaching full schematic.plz tell me the mistakes in that.
 

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Thread Starter

stylediva

Joined Dec 6, 2011
72
also tell me shud i use ceramic capacitors or the mentioned ones are ok??..and i use normal diodes..shud they be schottky???..
 

Thread Starter

stylediva

Joined Dec 6, 2011
72
plz tell me that all the values of the capacitors that i m using are right or is there anything to change??..i am applying 5vp-p. and i m giving PWM from AVR microcontroller..and inverting PWM from schmitt trigger thru RC network at its input..i m attaching full schematic.plz tell me the mistakes in that.
 

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praondevou

Joined Jul 9, 2011
2,942
1. What is the PWM frequency/duty cycle?

2. If the capacitor at the 74HC74 input is really 10uF then there will be no inverting PWM signal. Therefore the lower left and upper right MOSFET will not be switching. (or in an unpredictable manner) Since the lower left MOSFET will not be switching the bootstrap capacitor won't be properly charged, so the upper left MOSFET will also be doing nothing.

If this RDC at the 74HC14 was supposed to introduce an additional deadtime the circuit needs to be changed.

For both signals that go to the IR2110s the rising slope needs to be delayed.
 

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Thread Starter

stylediva

Joined Dec 6, 2011
72
thank u so much for ur help..its a great help..:)
plz tell me that the rest of the circuit is ok??..or is there any mistakes in the values of capacitors??...or anythng else..??..
 

Thread Starter

stylediva

Joined Dec 6, 2011
72
i will generate the PWM from AVR with the frequency u mentioned that is 10khz and also i can adjust the duty cycle..u guide me wat shud i do..??..plz..if i take 50% duty cycle which changes shud i need to do in ur ckt..???..
 
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