SCR phase angle control

[vovoj]

Hey guys,
I would like to ask you if any of you recommend an SCR phase angle driver IC for a thyristor driven power supply project. I saw on internet one called TCA785, but it looks like it's been discontinued.
I searched on the topics and couldn't find anything on this matter.

[Wolfgang]

Hi,

I have some SCR (pre) regulators described here:

https://electronicprojectsforfun.wordpress.com/power-supplies/preregulator-circuits-for-linear-power-supplies/

[vovoj]

Cool. I didn't know about these SCR regulators. The power source for which I am designing a controller has the following specs 15-40V/1000A. I am using a three phase thyristor bridge on the secondary side of a 380V/36V transformer.
I saw that in one of these pre-regulators they use a L120A IC to drive the TRIAC gate, which is very similar to the TCA785 IC. I wonder if there's any newer IC for SCR gate driving, perhaps able to do digital communication with a microcontroller, for example.

[David Hess]

I am not sure there have ever been any common phase control ASICs but everybody seems to have made one at some point.  They are not difficult to implement with discrete parts even when operating directly off of the line voltage.

The biggest problem tends to be that the simplest circuits rely on a DIAC or other medium voltage trigger device and most of them have been discontinued also; PUTs and DIACs are still available though if you want to go that route.

[vovoj]

Yeah... I see I will probably have to build one myself... The kind of phase controller I am looking for uses the idea of the diagram attached, because these allow closed loop control. The kind I know that uses DIACs can't be used with closed loop control because it relies on setting a potentiometer resistance.

[David Hess]

The kind I know that uses DIACs can't be used with closed loop control because it relies on setting a potentiometer resistance.

A DIAC or PUT just takes the place of the comparator.  When the voltage reaches the DIAC's trip point, it discharges.

[Circlotron]

I hope you are using 6 SCRs and not 3 SCRs and 3 diodes. Had one of the latter for control of a 15kW furnace and it really made the transformer growl. 6 SCRs made a nice clean buzz sound. And most definitely use a choke input filter if the DC output is to be filtered.

[vovoj]

Thanks for the information. I didn't know about that. Fortunately I am using a 6 SCR bridge.