• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Help calculating resistance values

Status
Not open for further replies.

MikeMl

Well-Known Member
Most Helpful Member
Thank you so much for all your efforts!

I just need to replace Q3 with an optocoupler. I have one with having capacity of 50 mA. Will it do? What do you suggest?
 

MikeMl

Well-Known Member
Most Helpful Member
I1 represents the NPN output of an opto-isolator that can source 5mA. One sinking 12mA could be used to replace q3
 
Hello. There is a problem. The resistors are dissipating a lot of heat when in off mode ( low input). Also optocoupler becomes hot. I am using 817. Is there any way to "shutdown" this circuit in "standby" mode?
 

MikeMl

Well-Known Member
Most Helpful Member
Hello. There is a problem. The resistors are dissipating a lot of heat when in off mode ( low input). Also optocoupler becomes hot. I am using 817. Is there any way to "shutdown" this circuit in "standby" mode?
Did you not notice that I labeled R1 and R4 as 1W resistors? If the the opto has the original 5mA flowing through it, then it shouldn't get hot.
The only way of reducing the standby power consumption is to build a driver with active source and active sink. This one charges/discharges the gate capacitance of the IGBT quite fast, but at the expense of power...
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top