# LC resonance driver circuit design (>10A)

#### Philruti

Joined Oct 7, 2019
3
I have been trying to drive an LC circuit with a resonance frequency of 27mHz with much success. I have also been simulating it using spice, but the resulting reading from the occilloscope don't match.
The end goal is to have about 10A resonating through the LC circuit (this results in about 16kv across the capacitor).
If anyone has some good starting points, or suggestions, that would be appreciated.
Note that this has to be externally driven so that the current builds a magnetic field, without having another coil counter act the field (so it can't be a transformer type circuit).
I have tried using an external MOSFET driven at the mentioned frequency, using a boost topology, but the resulting current is way too small.

#### Philruti

Joined Oct 7, 2019
3
Here is what I have tried, and when simulating it gives me 9A, but not even close to that with a actual circuit. Note that the gate is driven with a mosfet drive chip and a an adjustable clock chip

#### Papabravo

Joined Feb 24, 2006
17,262
27 mHz (milli-Hertz) is practically DC. Do you mean 27 MHz (Mega-Hertz)? Your schematic is incomplete so it is hard to spot reason for the discrepancy. I would start by saying that those power levels at a frequency of 27 MHz. may not be possible with the actual components. The next thing I would say is that your simulation schematic looks like it uses ideal components that are not practical in real circuits. What are you trying to accomplish?

#### ronsimpson

Joined Oct 7, 2019
1,649
"this results in about 16kv across the capacitor" That is a long long way from your 24V power supply.
Where did you find 20kv capacitors that can take 10 amps? C1, C2?
The MOSFET is only 600 volts.
I think the "16kv" can not be achieved.

#### BobTPH

Joined Jun 5, 2013
4,035
calculate the power across the internal resistance when you have 16KV at 10A across it, and maybe you will understand why a real circuit won’t do this.

Bob

#### ronsimpson

Joined Oct 7, 2019
1,649
SPICE does not care if you have 16kv on a 600 volt MOSFET. In real life it will not happen.

What do you want to make? Maybe there is another way.

#### Alec_t

Joined Sep 17, 2013
12,309
If you ever get 10A 0scillating in the resonant circuit you will have a 27MHz transmitter detectable all round the planet (or at least a large chunk of it). That won't go down well with the authorities and may well cause harmful interference to legitimate users of that frequency.

#### BobTPH

Joined Jun 5, 2013
4,035
If you ever get 10A 0scillating in the resonant circuit
I wouldn’t worry too much about that.

Bob

#### Philruti

Joined Oct 7, 2019
3
Thanks for the comments so far, hopefully I covered most of them in my response below:

Yes it is 27MHz
The Capacitor is a Parallel plate and can handle high voltages.
There should not be much power radiated, the device stores energy in either the E-field or the M-field and should not radiate much. Also when the voltage is highest ~16kV the current is 0A and visa versa. The high voltage comes from it resonating at its resonance frequency so the supply voltage can be significantly lower then the voltage at the connection between the capacitor and inductor.
I have added a small series resistance to capacitor and the inductor for the simulation, since there will be losses. And base on the simulation I should get ~10A.
The voltage seen the the MOSFET is max 200V in the above configuration. In the real application it stay even lower, but the MOSFET does get fairly hot, which means that there is a fair current through it.

#### ronsimpson

Joined Oct 7, 2019
1,649
the MOSFET does get fairly hot, which means that there is a fair current through it.
Hot = power loss. It could be you are turning on the MOSFET at the wrong time.
I don't understand where you are measuring 16kV, when there is only 200V on the MOSFET.