Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Pulse transformer to drive scr circuit

Status
Not open for further replies.
S

samuelr

Member level 4
Joined
Sep 23, 2008
Messages
78
Helped
4
Reputation
8
Reaction score
2
Trophy points
1,288
Activity points
1,861
Hi

I am trying to drive an SCR using a pulse transformer with the following circuit

1493025300_1447821358.gif


I got an MCU to swtich the MOSFETs are about 1 second interval repeated the total current to the transformer is about 200mA but there is no voltage on the output side.
I am using a 1:1 78601/2C pulse transformer from Murata

https://www.murata-ps.com/en/products/magnetics/pulse-transformers/78601-2c.html

I am not sure what I am not doing which is incorrect here.

- - - Updated - - -

Here is the circuit in its entirety.

SCR_TRIGGER_CIRCUIT.jpg

Basically SCR_N and SCR_P are from the MCU, the MOSFETs are working well its only the secondary side of the pulse where I am not getting anything.
 
Last edited by a moderator:

the one on the left might work - but not the one on the right as the gate current has to come out of the cathode - you have the return path via the anode which will never work... unless you source an anode gate SCR...

- - - Updated - - -

also the 4k7 limits the gate current to too small a value for SCR turn on - depending on the part you need 10 - 150mA, more at lower temps...
 
The classical UJT circuit would surely work, your actual design hasn't much in common with it.

It can work though if you add a bypass capacitor after the 4k7 current limiting resistor and the MOSFET is fed with a pulse train of respectively low duty cycle. In any case, a trigger circuit should be designed according to the SCR specification. Doing so would have revealed that the trigger current sourced by your design is far too low to trigger a SCR of some current rating.
 

Also, unless the SCR has an internal gate resistor, you need to add one to prevent spurious turn on, under transient dV/dt across the main terminals
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top