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Triac BTA208S600D, BTA208S600F blinking or working unstable

olek_el

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Hello! Please help me validate the electrical design and the set of the components.

The goal is to create removable modules that could switch the different types of payload:
1. DC MosFET module - switching and PWM of the 9-56V with 4A
2. AC MosFET module - switching and dimming (front and back-edge) of 230V 100W alternate current payload.
3. AC Triak module - switching and dimming of 230V 100W payload.

The biggest problem at this time appears when I connect lamps to the Triac module.
First, when the BTA208S600D triac was used, connected to the triac lamps were blinking ones at the moment when the triac was powered.
After I changed the triac to the BTA208S600F model, this blinking went out, but the glowing and dimming of the lamp became unstable.

Does anybody have ideas or remarks about the circuits?
 

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Easy peasy

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you usually need a soft start on a triac circuit powering lamps as the cold resistance of a 100W lamp is only a few ohms and a hard start can kill a cheap triac pretty easily ...
 

KlausST

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Hi,

It seems you want to control all three circuits by the same PWM. But a triac does not work corrcetly with a usual PWM.
It needs to be aligned to mains frequency.
Either for phase control or for full wave control.

Klaus
 

olek_el

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you usually need a soft start on a triac circuit powering lamps as the cold resistance of a 100W lamp is only a few ohms and a hard start can kill a cheap triac pretty easily ...
Hi! Cold start of 100W bulb isn't a problem for this triac. Its nominal current is 5A and inrush current is 60A.

Hi,

It seems you want to control all three circuits by the same PWM. But a triac does not work corrcetly with a usual PWM.
It needs to be aligned to mains frequency.
Either for phase control or for full wave control.

Klaus
No. There are different PWMs for each module. For driving triac we use zero-detector.
 

schmitt trigger

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I am going to ask AN EXTREMELY IMPORTANT piece of information that you have not provided;
What kind of lamps are those? Incandescent? CFL? LED?

If you are attempting to dim the latter two, and those are of the non-dimmable types, you will get those weird behaviors.
 

olek_el

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What kind of lamps are those? Incandescent? CFL? LED?

If you are attempting to dim the latter two, and those are of the non-dimmable types, you will get those weird behaviors.
LED lamps with impulse power supply and incandescent lamps blink when triac turned on.
Bad dimming is with incandescent and LED lamp bulbs.
 

schmitt trigger

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Excellent information, thanks.

The TLP267 indicates a recommended forward current between 4.5 and 7.5 mA.
With 820 ohm resistor and substracting Vf and VCEsat from 5 volts, you don’t meet the requirements.
Lower the resistor to 510 ohm
 

olek_el

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Excellent information, thanks.

The TLP267 indicates a recommended forward current between 4.5 and 7.5 mA.
With 820 ohm resistor and substracting Vf and VCEsat from 5 volts, you don’t meet the requirements.
Lower the resistor to 510 ohm

Hi! Thanks for helping.

According to our calculations, with an 820 Ohm resistor, we get exactly 4.5mA.

But we've also tried 560 Ohm (6,5mA) and the result was the same. The dimming was bad.

Weird thing, that with a 3 KOhm resistor dimming becomes a little better.
 

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trying to dim an impulse power supply with a triac - is not a very straightforward thing to do - for many reasons.

p.s. the cold start peak current of an incandescent 100W bulb is > 100A
 

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