AC lamp-fan control dimmer circuits

From the years, we are seen lots of dimmer circuits for AC and DC as well, the circuits that mostly peoples are using traditionally and what other advance chips are available for the AC lamp and fan control, providing the review for the glans.

1] AC phase control basic

As figure shows a ac switch is in series with the load controls the power feed to the load. The switch on/off control by the variable delay circuit. This is simple as that.

2] What will be the variable delay circuit looks like.

so, most simple circuit for the same is a combination of R-C-Diac as shown in figure.

On variation of resistance, phase delay happens, and on diac threshold it will trigger the triac. It will happens on both half cycles.

3] RFI issue

The sudden ON/OFF of the any load will create the radio frequency interference. This is more bookish word, let me simplify it. If you know the key-debouch concept and its waveform.

RFI is the same, but the frequency is different and the magnitude is also high, which causes the problem to the surrounding circuits or appliances, in a results, might get damage. If you realize when relay switch the ac load or motor our micro-controller get restarted if proper care is not taken while designing.

4] AC phase control with suppressed RFI

Here L-C is added for the RFI issue. As similar we add capacitor across the sw to reduce the denounce effect.

The one more issue is there with circuit arrangement is know as backlash effect.

The charge/voltage  on C1 is the controlling item here, which is also a delay deciding element in the circuit. Backlash is case when diac fire the triac, C1 start discharging via  diac and gate of triac before the triac completely ON. Which create the problem of keeping uniform timing for control.

5] Backlash minimum control circuit

option [1] add series resistor with diac to reduce the discharging current , option [2] add slave R-C as shown in figure to remove the effect of single capacitor

6] Zero-backlash AC control circuit

It is based on ujt oscillator.

It has, 12v dc supply, zero-crossing detector ZCD, UJT oscillator and other is load with triac sw and RFI L-C cuircuit.

This circuit can be modify for slow start as shown below.

Personally, like this circuit the way it performs.

There are some dimmer chips are readily available for the same with touch pad /micro-switch  external interface like opto-couples etc.

Numbers are S566B, HK612, SLB0587 etc. for review, will took snap of application circuit to have idea about before-design.

1] S566B is from siemens, not finding datasheet for it.

standard application circuit diagram with touch pad.

with micro-switches

with opto-coupler interface

2] HK612

3] SLB0587 it is upgraded version of S566b

For more details please ref the datasheet, you can leave a comment for farther requirement or any help you needs.