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Difference between TLP350 & IC4N35

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Rajnaveen

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Difference between TLP350 & IC4N35

hi friends ;
I am using IC TLP350 for MOSFET driver than I am getting very high voltage overshoot on Drain But when in the same circuit I use IC4N35 as a MOSFET driver there is no voltage overshoot , what may be the problem with TLP350?

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Frequeny is 100Hz in both the cases
 

FvM

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How (in which circuit) are you using 4N35 as a gate driver, it isn't but a basic optocoupler?
 

Rajnaveen

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Yes I am using 4N35 as agate driver of mosfet and the circuit is simple pwm solar charger ; it consist only mosfet as a switch between solar input and battery as output .
 

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Circuit inductance is generating the voltage peak during switch-off. To avoid it, you would supplement the circuit to a buck converter with input capacitor, free-wheeling diode and storage inductor.

If the MOSFET gate is controlled slowly by the weak opto coupler, the stored energy is burned in the transistor instead of being discharged into the voltage peak.
 

Rajnaveen

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Re: Difference between TLP350 & IC4N35

Circuit inductance is generating the voltage peak during switch-off. To avoid it, you would supplement the circuit to a buck converter with input capacitor, free-wheeling diode and storage inductor.

If the MOSFET gate is controlled slowly by the weak opto coupler, the stored energy is burned in the transistor instead of being discharged into the voltage peak.
due to cost have to use only mosfet ; not inductor and freewheeling diode ; it is just simple pwm based charger not mppt based .
My question is that when i am using 4N35 why is there no overshoot in the same sircuit , is that 4N35 is more effective than TLP350?

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due to cost have to use only mosfet ; not inductor and freewheeling diode ; it is just simple pwm based charger not mppt based .
My question is that when i am using 4N35 why is there no overshoot in the same sircuit , is that 4N35 is more effective than TLP350?
is it you mean to say that 4N35 is weak opto cuopler and the energy is burned in Mosfet itself , if it is then what is the disadvantage of it , ?
 

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due to cost have to use only mosfet ; not inductor and freewheeling diode ; it is just simple pwm based charger not mppt based .
There's no way to do regular pwm in this kind of circuit without bringing up some serious problems, either overvoltage that may damage the switch transistors or excessive switching losses.

My question is that when i am using 4N35 why is there no overshoot in the same sircuit , is that 4N35 is more effective than TLP350?
There's no overshoot because the circuit is switching less effective.

s it you mean to say that 4N35 is weak opto cuopler and the energy is burned in Mosfet itself , if it is then what is the disadvantage of it?
Probably it's the best way to it if you are for some reason stuck with the simple switch configuration. That's also what the "intelligent power switches" used in automotive etc. do, slowing down on/off time to several 10 µs and provide sufficient avalanche breakdown energy capability to absorb the remaining voltage spikes. PWM switching frequency shouldn't be higher than a few 100 Hz to limit the swiching losses. Slow switching and low frequency reduces also RF interferences.

If you're not sure about the transistor avalanche ruggedness, place a TVS diode across the transistor.
 

Rajnaveen

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All right that means 4N35 will create problem in future , OK i will not use that , I will use TLP250 bit how to drecrese overshoot in that case ?
The overshoot is near the mosfet voltage rating that burn mosfet some time ;
and one more thing does voltage overshoot produce more heating or what are the drawback of overshoot ?
 

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