# DC 12 V to AC 220 V

#### mjuric03

Jun 19, 2023
3
Hi, I really need some help with this. So, my paper presents the principle of the 12V DC voltage to 220V AC voltage converter, based on RL-astable. A mains transformer is used in the opposite connection of the primary and secondary, where the coils of the secondary form the reactive components of the astable. I need to do analysis of the operation of circuit and simulation of the circuit.

First step is to determine theoretical frequency of oscillation of this circuit. I couldn't find anywhere this equation, so if someone knows, please can you share it with me.

I attached below my "final circuit" (this is just principle I need to explain, but in simulation I will need some new parameters like diodes, resistors etc. and of course consumer - picture 1). Also, I will need some simulation of the output voltage (I attached below the circuit from which I need to do simulation - picture 2).

Thank you for help in advance

#### Attachments

• WhatsApp Image 2023-06-19 at 13.48.22.jpeg
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Feb 19, 2021
672

You will have to perform a non linear analysis. IEEE has a book and a number of papers
in this area.

Regards, Dana.

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,448
I'm afraid I don't see how this oscillator should oscillate at all.
I labeled the transistors:

Assuming Q1 is on, the the collector of Q1 is at ~ 0.1 V (VCEsat to be precise).
This in turn means that the base of Q2 is also at 0.1 V via R1. Therefore Q2 is off.
The collector of Q2 is then at Vcc via L2 and subsequently the base of Q1 is at ~0.7 V (VBE) via R2.
This keeps Q1 on and Q2 off. Permanently.

Only by coupling L1 and L2 am I able to create an oscillation via the feedback that results from the coupled inductors.

The "classic" astable multivibrator uses capacitors and resistors, no inductors, and is comparatively easy to calculate. You'll find heaps of information on that type of astable multivibrator on the internet.

#### Alec_t

Jul 7, 2015
3,481
Only by coupling L1 and L2 am I able to create an oscillation
Harald, L1 and L2 would be coupled, since they are the original secondaries on a re-purposed back-to-front mains transformer.

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,448
A, I see. An oversight on my part, I beg to excuse.

#### mjuric03

Jun 19, 2023
3
I'm afraid I don't see how this oscillator should oscillate at all.
I labeled the transistors:
View attachment 59562
Assuming Q1 is on, the the collector of Q1 is at ~ 0.1 V (VCEsat to be precise).
This in turn means that the base of Q2 is also at 0.1 V via R1. Therefore Q2 is off.
The collector of Q2 is then at Vcc via L2 and subsequently the base of Q1 is at ~0.7 V (VBE) via R2.
This keeps Q1 on and Q2 off. Permanently.

Only by coupling L1 and L2 am I able to create an oscillation via the feedback that results from the coupled inductors.

The "classic" astable multivibrator uses capacitors and resistors, no inductors, and is comparatively easy to calculate. You'll find heaps of information on that type of astable multivibrator on the internet.
Yes, I know about RC astable multivibrator, but I need to analyize this particular RL astable and I am not able to find any information about this circuit. My final circuit will probably look something like this (picture attached). But first I need to determine somehow frequency of oscillation and to simulate the circuit shown on picture 2 above. I did some simulation based on that but I don't know if it is correct because I am not aware what to expect on output..

#### Attachments

• Izrezak6.JPG
31 KB · Views: 3
• current.JPG
64.7 KB · Views: 3
• circuit_picture2.JPG
24.5 KB · Views: 3

#### mjuric03

Jun 19, 2023
3
View attachment 59559

You will have to perform a non linear analysis. IEEE has a book and a number of papers
in this area.

Regards, Dana.
Thank you Dana But first I need to determine somehow frequency of oscillation and to simulate the circuit shown on picture 2 above. I did some simulation based on that but I don't know if it is correct because I am not aware what to expect on output..

#### Attachments

• circuit_picture2.JPG
24.5 KB · Views: 2
• current.JPG
64.7 KB · Views: 2

#### Alec_t

Jul 7, 2015
3,481
The circuit is a classic "Royer oscillator". Since its operation is very dependent on the saturation characteristics of the transformer core, I'd be surprised if you could find a simple equation for calculating oscillation frequency.

#### bertus

Moderator
Nov 8, 2019
3,087
Hello,

Have a look at the attached PDF.

Bertus

#### Attachments

• Solid state vibrator.pdf
10 KB · Views: 2

#### ramussons

Jun 10, 2014
458
Hi, I really need some help with this. So, my paper presents the principle of the 12V DC voltage to 220V AC voltage converter, based on RL-astable. A mains transformer is used in the opposite connection of the primary and secondary, where the coils of the secondary form the reactive components of the astable. I need to do analysis of the operation of circuit and simulation of the circuit.

First step is to determine theoretical frequency of oscillation of this circuit. I couldn't find anywhere this equation, so if someone knows, please can you share it with me.

I attached below my "final circuit" (this is just principle I need to explain, but in simulation I will need some new parameters like diodes, resistors etc. and of course consumer - picture 1). Also, I will need some simulation of the output voltage (I attached below the circuit from which I need to do simulation - picture 2).

Thank you for help in advance
The frequency will change depending on the load. The Inductance of the coils will change depending on the load currents.

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