I have just performed a phase angle control using triac and in which i want that ac voltage to be converted to DC. I have used rectifier with triac and the output seems well.

But if i add a filter capacitor, the situation is not good. The voltage becomes high enough.

Phase angle controlled ac voltage - 83 voltsAC Dc rectified voltage with capacitor - 300 voltsenter image description hereenter image description here


Show your circuit.

Obviously (?) if your trigger angle is earlier than \$\pi\$/2 then the capacitor will charge to the peak input voltage minus a few volts for the semiconductors.

  • \$\begingroup\$ I have just added the schematic in the question. Please see to it and help me if possible. \$\endgroup\$ – Prakash veereswar Jul 30 '17 at 4:27
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    \$\begingroup\$ What I expected. You can set the angle less than pi/2 or add a power wasting resistor or a huge, heavy and expensive choke as Tony suggests, or use something other than a triac with some much smaller inductance and much higher switching frequency- a buck converter- using a MOSFET or a BJT or an IGBT. \$\endgroup\$ – Spehro Pefhany Jul 30 '17 at 4:34
  • \$\begingroup\$ That was very helpful. So i think i could add choke in series with the rectifier but, also adding with your suggestion to use high wattage resistor, will that provide a approximate dc voltage that doesnt goes to zero for every cycle. Will adding resistor would provide me dc voltage (even if it is not pure dc) without reaching zero for every cycle? \$\endgroup\$ – Prakash veereswar Jul 30 '17 at 4:59
  • \$\begingroup\$ Yes, it could, depending on the value. But it will also depend on the load relative to the resistor. Chokes have their own issues (they can prevent commutation of the triac) and it should go in series with the load, with an added reverse-biased flyback diode at the bridge output. \$\endgroup\$ – Spehro Pefhany Jul 30 '17 at 12:53
  • \$\begingroup\$ I have searched for choke design of rectifiers and it seems to be quite complex. My load is actually an inductor with approximately 20uh or less.please direct me to use the high wattage resistors to prevent the current reaching zero for every half cycle. My equivalent resistance of the load is 35 ohms. \$\endgroup\$ – Prakash veereswar Jul 31 '17 at 8:09

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