DC-DC converter circuit

Published:2013/7/9 3:09:00 Author:muriel | Keyword: DC-DC converter | From:SeekIC

This DC-DC converter ( inverter ) needs nothing but unmodified Radio Shack parts. You don't need to build or wind any coils or transformers. This is a cheap-and-dirty experimenter's circuit. I tested this and it worked for me, but I disclaim all warranties!] Connections to the LM386 Amplifier IC Not Shown: Pins 2 and 4 Go to Gnd.Pin 6 gets B+ and also a capacitor (not shown) to Pin 4.This capacitor should be a .1 uF ceramic cap in parallel with an electrolytic cap of at least 10 uF. This circuit sometimes works better with these, but usually works without. Components Shown Above: The LM386 is an audio amplifier IC, Radio Shack Catalog # 276-1731. T1 is a Radio Shack audio transformer, 273-1380. The red and white leads get the audio output from the LM386. (One grounded, one fed from Cout.) The blue and green leads feed the voltage multiplier. (One grounded, one feeds the first diode.) Cout is at least 100 uF. The positive terminal goes to Pin 5 of the LM386, the negative terminal goes to the transformer. The eight capacitors labeled C should be .1 to 1 uF rated at least 50 volts, preferably at least 100 volts. They will typically get 70 volts.The capacitor labeled 2C should be .2 to 2.2 uF rated at least 35 volts.For best results, C should be at least .2uf, preferably at least .47 uF. 2C should be at least .47 uF, preferably at least 1 uF. The nine diodes are 1N914/1N4148. (R.S. Cat. # 276-1620 for 50 diodes or 276-276-1122 for ten diodes) The two capacitors C1 and C2 should be .01 uF, preferably not a Z5U ceramic. R.S. Cat. # 272-1065 works well. The resistors R1 and R2 are 4.7K. R3 is a 10K resistor that I recommend, even though none at all usually works. R4 is a 10 ohm resistor and C3 is a .1 uF capacitor. These are recommended in documentation for the LM386 in order to avoid ultrasonic oscillation. However, the LM386 usually does not oscillate if these are omitted. Brief Description of this Circuit and How it Works The LM386 audio amplifier, R1 and R2, and C1 and C2 are used to make a crude Wien bridge oscillator. The R1-R2-C1-C2 network has minimum loss and no phase shift at approx. 3.5 kilohertz and serves as the positive feedback route for the oscillator. If an automatic gain/level control circuit was added to keep the oscillation from building up to the point that the LM386 clips, this circuit would be a sinewave oscillator. Instead, the oscillation rapidly builds up to where severe clipping occurs. The transformer steps the output AC of the 386 by a factor of about 10. The nine diodes and nine capacitors form a voltage multiplying rectifier circuit. The DC output voltage is (not quite due to diode losses) nine times the peak voltage of the AC delivered by the transformer. How to Use This Circuit and What to Expect This circuit works from 4 to 12 volts DC. However, the power output is quite unimpressive with supply voltages under 8-9 volts or so. At 9 volts, this circuit charges up capacitors at an average wattage of .4 watt. A 200 uF capacitor would be charged to 250 volts in approximately 16 seconds. At voltages near and above 9 volts, the rated limits of some of the components in this circuit are pushed. However, this circuit seems to work at up to 12 volts without anything burning out, or at least not too quickly. However, the LM386 seems to get rather hot at 12 volts. This circuit should be used as a cheap-and-dirty experimenter's circuit rather than a highly reliable circuit unless the supply voltage is near or under 7 volts. It is not a really ideal inverter circuit but a cheap-dirty one that can be made from Radio Shack parts. The ultimate output voltage with a supply voltage of 9 volts is about 300 volts. If you want something different, you can use a different number of diodes and capacitors. CAUTION - This circuit produces high voltage. Even if you get shocked by a part of the circuit that may not kill you, the shock might cause you bump into something else that might.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Power_Supply_Circuit/DC_DC_converter_circuit.html

Print this Page | Comments | Reading(3)