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JonathanFilippi
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Posts posted by JonathanFilippi
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Indeed engineering would have never got to the advanced level it is today if it wasn't for people like audioguru challenging ideas and offering constructive criticism. :)
Costructive criticism is the key for technological improvement and learning :) -
Jonathan,
Thanks for your contribution to the site. It seems that every time you post a new project, you are challenged by someone who thinks you made mistakes (like when you posted the temp controlled fan).
I hope it is not discouraging to you. Very good work!
MP
I'm not discouraged ;), answering questions and solving doubts is funny, also Audioguru started an interesting discussion.
I made a simple challenge because the project severely under-powers a pair of the excellent amplifier IC's that the author mentioned:
The power supply is easily scalable up. With those heatsinks the mosfets should hold up to 300W (but with fan), the important thing is the transformer core, that must be sized accordingly. Also the turns strenght must be increased or they will heat up and reduce efficiency, the diodes too must be be increased, maybe using higher current capablility shottkies.
The reason that i scaled down the power to 30W is because i have 20W speakers on hand (and probably i cannot go farther than 20W without blowing them). I'm building a small amplifier for a small car, to be used with an mp3 cd player. (suggestions with the Lm3886 amplifier are welcome Audioguru) -
Hi Jonathan,
I am sorry that I misunderstood your load impedance. So your voltage converter project can power a 30W per channel into 4 ohms stereo amplifier. I wish it was designed for much more voltage and power output so it could drive National's Overture amplifiers to the much higher power that they were designed to produce.
Have you seen Philips' TDA1562Q class-H amplifier IC? Its output is rated at 55W RMS into 4 ohms at low distortion with an ordinary car battery for its power supply. It has a voltage-doubler inside and operates as a 14.4V bridged amp most of the time to stay fairly cool, then switches at zero crossings of the input signal to using its doubled supply voltage for high power peaks. It also doesn't need your voltage converter circuit for much more power than your project.
http://www.semiconductors.philips.com/acrobat/datasheets/TDA1562Q_ST_SD_2.pdf
Of course it can be designed very easily to output +/- 30VDC per rail. This can be accomplished varying two things. First the turn ratio (instead of 1:2 using 1:3) and downregulating to 30V via PWM (adjusting the voltage divired feeding the error amplifier accordingly). If you want to change the turn ration without changing primary turns (and so the switching frequency), you can use 5T /15T of litz or multiple wire (more wires in parallel to reduce skin effect). This design can also work at 35V if you keep the input voltage at 12V (though it may drop due to wire resistance/battery resistance). Since at 30V the power will be higher the core size must be increased accordingly, or the switching frequency (but this will higher the hysteresys and switching losses). You may try 3:9 or 4:12 with a higher switching frequency.
The TDA1562Q is marvellous, probably it is used in most car amplifiers . But what does mean class-H ?
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Thanx for the advice. I will use the caps on the amplifier input (1000uf+100nF for each rail near the amplifier). Anyway even it is noisy because of ripple, the noise is in the ultrasound range (areound 50KHz), so it will not be heard
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You are right, but only at half.
I'm claiming 50W output power on -
This circuit itself is a crap...
Better is to use a 555 with duty cycle to 50% and 50Hz frequency, Two mosfets with respective gate driver and a half tapped transformer with the rating needed to get the power required.
Automotive 12V to +-20V converter
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