Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
A light dimmer is not the same as a high frequency PWM circuit.
The reason I brought up PFC is that; Most boost up switchers have a fast error amplifier. So fast that they will try to filter out 60hz noise. A PFC’s has a very slow error amplifier. It takes about 6 cycles of the 60hz for the amplifier to respond. **SNIP**
The reason I brought up PFC is that; Most boost up switchers have a fast error amplifier. So fast that they will try to filter out 60hz noise. A PFC’s has a very slow error amplifier. It takes about 6 cycles of the 60hz for the amplifier to respond.
In your case you want to buck down 240 volts to lets say 120 volts (RMS). If you have a fast error amplifier, anything above 120 volts will be bucked down to 120. You want to run the FET at 50% duty cycle. The error amplifier will look at the RMS of the output voltage and adjust the duty cycle to maintain 120 volts AC.
If the input voltage moves the output voltage will move. In about .1 second the error amplifier will move the duty cycle around to cause the output voltage to remain constant.
I see what you're saying, as the duty cycle is varied the input voltage is divided by the same factor. However a buck is totally different, it only works on DC and a freewheell diode keeps the current flowing from the inductor when ther switch is turned off.
**broken link removed**
Filter it how? A capacitor would instantaneously charge to the line voltage, and an inductor would, in it's attempt to keep the current flowing when the FET turned off, blow the FET.
The original "schematic" was more of a block diagram showing a FET in a diode bridge going to a filter block as a GIF file. ( I can still see it here )Well I can no longer see the original schematic as there is a problem with the file.
Only hero can answer this, but I now am curious. Where is that schemo!..lol
-BaC
Are you talking about this circuit?Filter it how? A capacitor would instantaneously charge to the line voltage, and an inductor would, in it's attempt to keep the current flowing when the FET turned off, blow the FET.