Push-pull DC/AC inverter

Thread Starter

Pyrex

Joined Feb 16, 2022
239
Hi all,

The interesting and simple inverter with sine wave output:

Push-Pull DC-AC Inverters (smps.us)

I have a small PCB from an old TV or a monitor which produces high voltage for CFL lamp, the circuit diagram of the output stage was drawn from the PCB and was found comparable to the second circuit diagram ( with inductor and BJT transistors).
The PCB was powered from two AA NiMh batteries. Oscilloscope was used to examine the PCB. It oscillate at about 40kHz, voltage at the C was about 14Vp-p, a slightly distorted sine wave. I suppose, the PCB was powered from 12V rectifier before.
A good sine wave oscillator...
I have an idea to build such an inverter able to work from 1V source and use it in the ESR tester. A dozen of EE13 ferrite cores and rings and a low power germanium transistors are available:

GT308B Datasheet, Equivalent, Cross Reference Search. Transistor Catalog (alltransistors.com)

Can anyone suggest me how to calculate resistor and capacitor values and number of turns?

Thank you in advance
 

wayneh

Joined Sep 9, 2010
17,493
I have an idea to build such an inverter able to work from 1V source and use it in the ESR tester.
Why reinvent the wheel? There are a handful of ESR designs out there, and both commercially available kits and finished meters. You don't need a nice sine wave to make a useful ESR meter.
 

MisterBill2

Joined Jan 23, 2018
17,843
Hi all,

The interesting and simple inverter with sine wave output:

Push-Pull DC-AC Inverters (smps.us)

I have a small PCB from an old TV or a monitor which produces high voltage for CFL lamp, the circuit diagram of the output stage was drawn from the PCB and was found comparable to the second circuit diagram ( with inductor and BJT transistors).
The PCB was powered from two AA NiMh batteries. Oscilloscope was used to examine the PCB. It oscillate at about 40kHz, voltage at the C was about 14Vp-p, a slightly distorted sine wave. I suppose, the PCB was powered from 12V rectifier before.
A good sine wave oscillator...
I have an idea to build such an inverter able to work from 1V source and use it in the ESR tester. A dozen of EE13 ferrite cores and rings and a low power germanium transistors are available:

GT308B Datasheet, Equivalent, Cross Reference Search. Transistor Catalog (alltransistors.com)

Can anyone suggest me how to calculate resistor and capacitor values and number of turns?

Thank you in advance
Why even consider operating any piece of test equipment on one volt? Three volts (2 cells) is a bit better but six volts provides vastly more capability..
 

Thread Starter

Pyrex

Joined Feb 16, 2022
239
The idea is to power the ESR tester from a single AA NiMh battery. 0.2V for regulator.
The inverter is resonant type, and worked nice. When voltage was lowered to 2V , it's stopped. Sine wave is more like triangle, anyway, it's much better than square wave.
Sine wave is preferred for ESR tester for reliable results, almost all professional testers work on sine wave
 

BobTPH

Joined Jun 5, 2013
8,671
Why are you making life so difficult? The circuit should not be designed to work with a poor battery choice, the battery should be chosen to make the circuit work. A small Li Ion would be smaller than an AA and have plenty of voltage.
 

MisterBill2

Joined Jan 23, 2018
17,843
With the mosfet circuit in the one attachment, the fact is that one volt is not enough to turn on the transistor Vgs has some minimum requirement that is greater than that. And with silicon bipolar transistors you need close to 0.7 Vbe for it to even start to conduct.
Add a diode drop and there is no way it can come close.
One option might be to use germanium transistors that can function with a lower Vbe. Maybe.
 

Thread Starter

Pyrex

Joined Feb 16, 2022
239
Thank you, guys, for the answers,
Let's say, it's a hobby. Of course, various ESR meters are available on the shop. In short, I want to make a low voltage powered sine wave oscillator. I have some old components for free, so why not? Why AA- it have relatively high capacity, and low cost.
I do use an ESR meter with 5 LED indicator, powered from 9V battery, and I want something more advanced
 
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