Mains voltage frequency amplifier?

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Discussion Overview

The discussion revolves around designing a circuit that can take power from the mains AC supply and increase its frequency from standard levels (50 or 60 Hz) to higher frequencies (around 15 kHz to 150 kHz), while maintaining an output voltage of at least 25 or 30 volts. The context includes theoretical considerations, practical applications, and circuit design challenges.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that to achieve the desired frequency increase, the circuit must first rectify the AC to DC and then convert it back to AC at the higher frequency.
  • Another participant expresses a desire to wirelessly transfer power through induction, indicating that increasing the frequency could enhance transfer efficiency.
  • A participant mentions that there is no physical method to simply increase the frequency of an AC power signal without using a powered circuit to create a higher-frequency waveform.
  • One suggestion is to use a 100V power amplifier style to facilitate frequency adjustments.
  • A reference is made to the Sinclair Z30/Z50 power amplifier applications, which included a high power variable frequency oscillator, noting the need for a transformer to step up the voltage when using semiconductor amplifiers.
  • A participant questions whether a Colpitts oscillator would be suitable for the application, while another suggests that traditional audio oscillator topologies like Wein bridge or Phase shift might be more appropriate due to challenges in finding inductors for the required power levels.

Areas of Agreement / Disagreement

Participants express various ideas and suggestions, but there is no consensus on the best approach or specific circuit design. Multiple competing views remain regarding the methods for achieving the desired frequency increase and the practicalities involved.

Contextual Notes

There are limitations regarding the assumptions made about circuit components and configurations, as well as the dependence on specific definitions of frequency and power levels. The discussion does not resolve the technical challenges or provide a definitive solution.

Who May Find This Useful

Individuals interested in circuit design, power electronics, wireless power transfer, and frequency modulation may find this discussion relevant.

masab_ahmad
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hello all
i wanted to make a circuit that takes power from the main a.c supply and increases its frequency( from 60 or 50Hz to about any frequency (lets say about 150KHz? or 15KHz?)), but the output voltage should not drop less than about 25 or 30v...
 
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masab_ahmad said:
hello all
i wanted to make a circuit that takes power from the main a.c supply and increases its frequency( from 60 or 50Hz to about any frequency (lets say about 150KHz? or 15KHz?)), but the output voltage should not drop less than about 25 or 30v...

Sounds like you need to rectify to DC, and then chop back to AC... What is the application for such high voltage at 15kHz-150kHz?
 
well i actually wanted to wirelessly through induction...incresing the frequency should help...i don't understand how the conversion u mentioned would help though...
 
masab_ahmad said:
well i actually wanted to wirelessly through induction...incresing the frequency should help...i don't understand how the conversion u mentioned would help though...

Do you mean that you want to transfer power wirelessly through induction, and to increase the transfer efficiency, you want the frequency of the AC power to be in the kHz range, instead of the standard 50/60 Hz of the AC Mains supply?

There is no physical way to just increase the frequency of an AC power signal. You must instead make the higher-frequency waveform with a powered circuit. That circuit can get its input power from the AC Mains. It will usually rectify the input AC Mains into a DC voltage, and use that DC voltage to power the kHz oscillator and power amplifier to make your output power kHz AC waveform.
 
Would the easiest way be to use a 100V PA style amplifier ?
Then you can play with the frequency easily.
 
One of the applications in the old Sinclair Z30 / Z50 power amp applications and service manual was for a high power variable frequency oscillator for doing exactly this. I think the Z50 could reach 30 Watts.

However one problem with this approach is that you need a transformer to step up the voltage if you are using semiconductor amps. You could get old valve amps to reach mains voltages this way though.
 
@berkeman
thats a good idea
@mgb phys
i don't think i have acces to that amplifier
@studiot
thats a good idea too
@all
thanks for ur replies and would a colpitts oscillator do the trick?
 
thanks for ur replies and would a colpitts oscillator do the trick?

You are looking for an audio frequency oscillator. You would have trouble finding inductors for the power levels you require.

Traditional audio oscillator topologies such as Wein bridge or Phase shift or T would be better.

The Sinclair circuit used their amp in a Wein bridge.
 

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