I connected Q1's emitter to ground. Now the circuit gives 26 V on output but under 120 Ohm load it downs to 11.5V. Under this load circuit consumes 600 mA from 12.2 V battery. I don't want to make exact copy of author's toroidal coil because it is difficult for me to find appropriate core. So instead of author's coil i use factory-made coil http://electronica.bashel.ru/info/1201/RCH.jpg with L=1 mH (not 1 mkH) and R=1.8 Ohm. Is it possible to tune circuit for predefined coil?
Wow, I can't believe I made such an elementary mistake while drawing the diagram. I'll update the schematic with the missing ground.
The coil you have used looks to be either air core or have a small ferrite core? You really need a better core for this. Toroids are easily salvaged from computer power supplies.
Yes, i can get some toroids. But you didn't specified the exact inductance of L1 so i can't make my one. I think it is bad way to look for toroid of the same size and the same permeability as yours one and wire of the same diameter as yours. Instead i prefer made or buy coil of the certain inductance which can be measured using sound card and this beatyful software: http://www.baudline.com/solutions/swept_sine_vs_wgn/index.html .
Can you inform us about the inductance of L1? This can be simply made by connecting capacity parallel to coil and measuring resonance frequency.
I don't know the inductance of L1 as I have never run the calculations and it was not specified in the circuit. If you find a toroid of similar dimensions and wind it as shown, then the circuit will work.
I followed links you show. Good theory but the question still: how do i know the value of permability of the core? Because i don't know the value of unknown core so i decided that it will be simplier and moe reliable just to measure it using LC resonance effect.
I'm not sure how one would measure that, or if it is even easily possible. Best bet is to look up the specs of a toroid of approximately the same construction and make a guess.
Measuring of L can be done very simple! I connect the coil parallel to capacitor of the known value. Then i connect first end of the capacitor to the output of the soundcard and the second end to the mic input. The schematics looks like this: C out(sig) ---||--- mic(sig) out(gnd) -------- mic(gnd)
Then i use baudline software (see above) to generate gauss noise. Then find resonance frequency using gain-frequency characteristic.
L can be easily calculated from resonance condition. As we know the equation of resonance looks like this:
wL=1/(wC) where w=2*Pi*N where N is resonance frequency (Hz).
12V To 24V DC-DC Converter
Posted - Nov 19 2009 : 01:08:16 AM
