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Title: Can this switch PDM Modulator power supply be modified to 220V input? Post by: BA7OMW on April 05, 2025, 12:39:13 AM [From Google Translate]
When I was looking through old forum content, I found a switch modulation power supply designed by QIX. It does not have a traditional iron core transformer and seems to be more efficient. But I live in a country with 220V AC voltage, so I want to know how to modify this switching modulated power supply to 220V AC input. Title: Re: Can this switch PDM Modulator power supply be modified to 220V input? Post by: BA7OMW on April 05, 2025, 12:47:11 AM The 310V DC voltage after rectified 220V AC seems too high for a push-pull circuit. Perhaps a bridge circuit would be a better choice?
Title: Re: Can this switch PDM Modulator power supply be modified to 220V input? Post by: vk3alk on April 06, 2025, 04:42:47 AM Hi
Have never seen this circuit before and found it interesting.... Steve would be the best person to comment on this really.... But in my opinion what I would do is use a 220:120 stepdown transformer and make the circuit without any changes in its design... Modifying the design for 220VAC input would require a change in the Power Supply area.... 220VAC mains has real grunt and the filter capacitors would be a short before charging up creating probably peak currents of 80Amps to exist for very short periods of time causing all kinds of problems ..... particularly if switched at the peak of the AC cycle.... Also your carrier voltage would be higher too.... which might cause you some issues.... Maybe others would like to comment.... Wayne Title: Re: Can this switch PDM Modulator power supply be modified to 220V input? Post by: W1DAN on May 04, 2025, 07:59:10 AM Hi BA7OMW! AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
This is Steve's modulator and driver and output circuit. The DC power supply is not part of this board. Steve and most of us use an unregulated analog DC supply that supplies around 115V DC to feed this board or similar. Here is Steve's website that has further information: http://www.classeradio.com/ If you choose a switching power supply, the output must be ground referenced. The K7DYY Super Senior transmitter is class D that uses a line switcher supply/modulator. The RF stage floats above ground. Dan W1DAN |