I am playing with TRIAC dimmer from past few days, by firing TRIAC at different phase angle the overall output can be lowered.

but i was thinking if i can use a diode rectifier and a filter capacitor to get DC out of the Dimmer. I know it will be a non isolated topology.

Transformer are always there but, thinking if i can use triac dimmer output and rectify it to DC.

  • 1
    \$\begingroup\$ The answer is Yes, you could ...but I'm not sure a dimmer is the right solution. You really want a feedback based design that will give you a chance to regulate the DC output. Remember that you can only adjust the DC output over a 90 Degrees quadrant of conduction for this type of application. \$\endgroup\$ – Jack Creasey Mar 31 '17 at 19:45
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    \$\begingroup\$ Triac dimmer methods were used by Lambda and HP in the 70's to pre-regulate into LDO's to reduce the voltage drop. But with SMPS designs today, these are still inefficient and more complex by today's standards. Also dV/dt current spikes create the need for more filtering. For high power, active PFC is the 1st step. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 31 '17 at 19:46
  • \$\begingroup\$ They were used in many large scale battery chargers then too .....very simple designs. The dI/dt spikes are no worse than many other solutions with transformers. \$\endgroup\$ – Jack Creasey Mar 31 '17 at 20:51
  • \$\begingroup\$ Then why aren't they used in LED without SMPS ? \$\endgroup\$ – srijib Apr 3 '17 at 15:12
  • \$\begingroup\$ @user2557956 No need. At that low end of the LED market sprectrum, you ditch out all regulation to save cost. \$\endgroup\$ – winny Jul 14 '17 at 7:22

You are free to rectify the output of the TRIAC. You should of course ensure that whatever circuits the TRIAC is supplying can accept the dc output. You don't actually say what it is you intend to drive.

To give one real-world example, rectifying TRIAC output has often been done with universal motor controllers. This can reduce the size and weight of the motor, and decrease wear. Torque ripple can be reduced, as well as low frequency noise. This is due to the reduced rms and peak to peak current.

  • \$\begingroup\$ I am wondering if this is possible then why do the cheap china made LED uses capacitor drop (those do not use SMPS) capacitor drop circuit has a current limit of few milli amps. i can run series LED 3.3v x 50 LED with a TRIAC rectifier by adding appropriate filters \$\endgroup\$ – srijib Apr 3 '17 at 15:10

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