Need help with Triac & SCR

[JAIZY]

how we can use the triac and SCR as a switch in flyback converter

 

[JAIZY]

pls if anyone know then tell me.i use a triac in flyback converter in place of IGBT as a switch but the output is zero volt.so how this happen can anyone tell me pls

 

[crutschow]

You can't.

 

[Dvinchy]

I guess all the circuit has been burned

 

[JAIZY]

why i cannot use the triac in place of IGBT as a switch in flyback converter.why it will burn .Whats the logic behind that.can u pls explain me brother

 

[alec_t]

i use a triac in flyback converter in place of IGBT as a switch but the output is zero volt.so how this happen can anyone tell me pls

Post a schematic of the circuit you used and we may be able to help.

 

[JAIZY]

i am showing a circuit in which a mosfet is used but i want to use triac in place of MOSFET.
https://www.google.com.pk/imgres?im...IcnhrAeIiOXJDg&sqi=2&ved=0CEIQ9QEwAw&dur=2461

 

[edeca]

As per our discussion on the chat you cannot replace the transistor (a FET) in your circuit with a triac or SCR. You were talking about T2 in the following image:

View attachment 60374

The FET provides the pulses into the flyback transformer which are required for it to work properly.

Neither a triac or an SCR are designed to work in this way.

 

[crutschow]

why i cannot use the triac in place of IGBT as a switch in flyback converter.why it will burn .Whats the logic behind that.can u pls explain me brother

A FET can be turned on and off by the gate voltage. A triac or SCR will turn on when current flows through the gate, but will not turn off when the gate current is removed as long as there is still anode current flowing. The anode current must be reduced to zero to shut off these devices. Thus triacs and SCRs work well in AC circuits where the current periodically goes through zero, but don't work in DC circuits unless some other method is employed to reduce their current to zero.

It should thus be apparent that triacs and SCRs are not usable in flyback circuits where the control element has to turn the transformer current both on and off.

Edit: Why do you want to replace a transistor with a triac/SCR?

 

[MrAl]

how we can use the triac and SCR as a switch in flyback converter

Hi there,


SCR's can be used in high power DC switching supplies but only with special design that takes into account the extra special commutation needs of the devices. Since regular transistors and MOSFETs dont require special commutation, their circuits are not designed with that in mind and therefore will not work if the switching device is simply replaced with an SCR. It wouldnt be that logical in a power switcher anyway because a MOSFET will lead to a higher efficiency circuit and the prices came down quite a bit in the past for these devices.

Perhaps you should state your reason for wanting to use an SCR in the switching circuit in the first place.

 

[crutschow]

Some further thoughts. You can use an SCR in a high voltage pulse circuit, such as a CDI ignition, which charges a capacitor to several hundred volts and then has the SCR discharge the cap through the primary of the ignition coil (transformer). In that case there is a resonant reverse current after the discharge due to the inductance of the coil resonating with the capacitance which shuts off the SCR, resetting it for the next discharge cycle.

 

[JAIZY]

yes now i understand why we did not use SCR OR TRIAC in place of IGBT or MOSFET.i make the circuit diagram of flyback converter and use the step up transformer with the ratio of 10:1 and our input voltage is 12volt dc but the output voltage is only 3 to 4 volts.can any one know why this happen and what is the logic behind that.reply me pls.

 

[JAIZY]

sorry the transformer ratio is 1:10.

 

[crutschow]

If it's not working I suspect an error in your circuit.
Double-check all connections and component values.
Is it built exactly like the schematic including the transformer inductance values?