I know how to use basic voltage doublers, triplers and the like. But is there a way to multiply an ac voltage by 1.5 ? I need about 24-25VDC regulated out of a 18VAC xformer for a small load (about 50ma).
Thanks in advance.
Thanks in advance.
Under such a light load, the transformer may put out somewhat more than 25 volts. If you're lucky, you may need nothing more than a bridge rectifier and a 7824 regulator. Measure the transformer secondary voltage with no load. Otherwise, I agree with Mooly.
Voltage doubler and a regulator.
Voltage doubler and a regulator.
Thanks. It seems like I have no choice...
- actually the transformer is also used for other stuff at 200ma/17VDC, so I don't expect it to put it a lot more voltage than what it's rated for. A quick check shows me about 25VDC after rectification and filtering.
- with a doubler, I can expect about 44VDC. That means about 20*0.05= 1W of dissipation for the regulator. That's why I asked about this.
- actually the transformer is also used for other stuff at 200ma/17VDC, so I don't expect it to put it a lot more voltage than what it's rated for. A quick check shows me about 25VDC after rectification and filtering.
- with a doubler, I can expect about 44VDC. That means about 20*0.05= 1W of dissipation for the regulator. That's why I asked about this.
Could you perhaps play around with the value of the caps in the doubler --- using the reactance as a wattless dropper and so on --- and still have reasonable DC voltage for the regulator to work off without the ripple component being too high.
Would have to think about that.
Would have to think about that.
Hi,
Fractional voltage multiplier do exist, but they're probably too complicated for your application.
I would use a regular voltage doubler, but with a small input capacitor serving also as ballast, and a shunt regulator at the output.
A capacitive supply in fact.
The power that will be wasted is tolerable, and the complexity is minimal.
LV
Fractional voltage multiplier do exist, but they're probably too complicated for your application.
I would use a regular voltage doubler, but with a small input capacitor serving also as ballast, and a shunt regulator at the output.
A capacitive supply in fact.
The power that will be wasted is tolerable, and the complexity is minimal.
LV
lineup said:
No, but space is an issue. The aim of this is to provide a higher regulated voltage for an (headphones) amplifier front end, using the existing power rails.
I think I will go for a voltage doubler but I'll stick a pair of 33R/2W resistor in serie before the voltage doubler.
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