# How to increase frequency from 50Hz to 100kHz?

Discussion in 'General Electronics Discussion' started by Shehroz, Apr 29, 2015.

1. ### Shehroz

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0
Apr 29, 2015
Hi, I'd be glad if someone helped with the following:
I want to obtain a 100kHz, 15-20 V signal from mains i.e 50Hz, 220V. I have stepped the amplitude down but I can't find a circuit which could use the mains or the stepped down signal and give the increased frequency signal at the output. I looked into RF oscillator but they are somewhat not approachable. I need to use discrete components. Could someone link me to a circuit diagram or any other idea that might help in increasing the frequency?

5,164
1,087
Dec 18, 2013
Why do you need to do this using the mains frequency. What is the end project?
Thanks

3. ### Shehroz

15
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Apr 29, 2015
The end project is a wireless power transmission circuit, which charges a 5V cell phone battery for example. So it should use the mains.
I am using mutually coupled inductance to transmit the power. It turns out that the inductor coils I've prepared transmit and receive at a frequency of 100kHz.

5,164
1,087
Dec 18, 2013
Hello
Can you post any type of circuit diagram you have showing us what you have already done.
Thanks

5,164
1,087
Dec 18, 2013
You can build your own circuit quite easily. Here is one I have simulated for you, it's one method used for wireless power transfer. I am able to draw 120 mA at 12 Volts from the output. The output drops to 5 volts when drawing 500 mA.

All you need to do is power this circuit from a suitable power supply of 5 Volts and at least a few amps. Regulate the output with an LDO regulator and you should have something that works reasonably well reliably supplying 100 mA or so. The circuit is setup as a simple multi-vibrator (astable) driving the output coil tuned circuit alternately.

The tuned circuit then is inductively coupled to the receive circuit. For real life you will need to remove the ground connection from the receive circuit , I added this so it would simulate correctly. Other circuit values may need to be adjusted also. This is a proof of concept circuit and is no proof that it will work in real life without some minor component value changes.

Thanks

6. ### Shehroz

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Apr 29, 2015
That should help me a lot Adam. I have a few questions though:
What is the spacing between the mutually coupled coils (physically), and are the coils air cored?
Would this design simulate on PSIM? Or which software (freeware) may help me simulate it? I believe exact models are not available on PSIM.

7. ### Shehroz

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Apr 29, 2015
Also, I have a limited range of diodes and MOSFETs available. Could you please suggest alternatives to those models in the diagram?
Would IRF540 be an alternative to the MOSFET and 1N4148 for the diode up there? How can I modify the circuit to use these models, if possible?

Last edited: Apr 30, 2015

5,164
1,087
Dec 18, 2013
The inductor models are ideal air core. LT spice is the software I used, it's free to download. Coupling of the inductors is 1 which is ideal conditions 100%. Real life will vary greatly from this as I have said.
Thanks

5,164
1,087
Dec 18, 2013
The diodes need to be Shockley diodes really but give it a go. The MOSFETs don't need to be anything special, again give them a try, I don't have time to go through the data sheets at the moment. Maybe that's something you would like to do? You could simulate it in LT spice and see if the component variation will work.

10. ### Shehroz

15
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Apr 29, 2015
Yes I got the same simulated values with the original circuit.
Could you also please summarize whats going on in the circuit theoretically?

5,164
1,087
Dec 18, 2013
Tell me what you think is happening first? You dont get it that easy

12. ### Shehroz

15
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Apr 29, 2015
I think main purpose is to switch the direction of currents in the inductors (5uH) on the transmitting circuit.

This happens due to the direction of current passing in between the schottkey diodes and 68uH inductor on the right. This causes rapid change of polarity of the DC voltage hence causing a rate of change of flux followed by mutual induction which converts it to AC at the receiving end.

5,164
1,087
Dec 18, 2013
Yep, sounds good. Then the A.C is converted to D.C by the diode on the output.