# design firing circuit for thyristor

Posted by hasan081043
 design firing circuit for thyristor November 28, 2013 06:41AM Registered: 10 years ago Posts: 3
The supply is 220v 50Hz ac.I need 80V DC output voltage .For this i need to fire the thyristor at 80

degree.The main problem is to fire the thyristor at 60 degree .please sugest me the firing circuit.
for half wave controlled rectifier
Vdc=Vm(1+cost)/2*pi
here t=firing angle
Vm=maximum ac voltage
Vdc=output DC voltage

So for Vdc=60V ,Vm=1.414*220=311
t=?
the required firing angle would be 80 degree
 Re: design firing circuit for thyristor November 28, 2013 06:55AM Registered: 10 years ago Posts: 86
 Re: design firing circuit for thyristor November 28, 2013 08:54AM Registered: 13 years ago Posts: 1,797
you are overcomplicating things. look at lamp dimmer circuit. it is more complex that using a mosfet, and a arduino to control such as ramps and at a safer voltage such as 12v.

[wiki.dxarts.washington.edu]

this is a full wave and uses an scr, but concept is same. you want to lower the voltage across the gate to keep it from turning on until the voltage you want is reached. it relies on the fact that the input voltage is sinusoidal, and has a wide range of increasing voltages through its wave form.

you need to control the forward voltage as to not trigger until a certain point. you can control average power but peek voltage will still reach maximum as what the input voltage is. it is just the nature of the circuit.

if you are looking for average output power control, and not voltage control this circuit above would be a good starting point. also just google lamp dimming circuits.

Edited 1 time(s). Last edit at 11/28/2013 08:55AM by jamesdanielv.
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