This article will help you to build yourself a simple, yet effective dc dc converter.
After trying a couple of circuits from internet, which used 4001 chip and do not worked, I made my own. The converter was intended to power different devices from a USB port. It has a simple push-pull design with a driver from a single 4001 CMOS chip. The result turned to be an universal converter - the driver is operational from 3V to 15V; with a change of the windings of the output transformer you can get any voltage you need; and if you change the transformer and the output transistors, you can use the same simple driver for more powerfull projects. The driver is very simple but versatile - it can power both bipolar and FET transistors, and it is quite efficient - at a full load, the converter had 95% efficiency. The 4001 chip is used to generate switching frequency with two anti phase outputs. This assures that when one of the push-pull transistors is ON, the other is OFF. The cirquit also has a pause between the switching of the transistors and this is the main reason for the high efficiency. Both frequiency and the pause between the pulses can be regulated, so the driver can be used with different transformers. The dead time between the switching of the output transistors is one reason for the high efficiency of this simple circuit. The other is that the output of the device is connected in series with the input. The effect of this is two-fold. In this way only part of the power is actually converted - with this transformer ratio a bit more than half. For example: if the input power is 4W, at the output 2 watts are transferrd directly with no convertion and hence with no loss. The other 2 watts will be converted with say 80% efficiency, that is, with a 20% loss. So, at the output we have 2W + 2x0.8W = 3.6W. Given that the device consumes 4W the total efficiency is 3.6/4=0.9 or 90%. The other effect of connecting the output in series is that the converter needs less voltage difference to overcome. The peak currents through the switches are lower. If you decrease the current twice, the conduction power losses decrease four times.This program excellentIT(4000)EN version is in English will be very useful for those, who need to calculate impulse power transformers - Free SMPS transformer calculation tool made by Vladimir Denisenko.
- Simple and low cost design. - Compact and lightweight. - High efficiency up to 95%. - Consumption without load - 50mA. - Supply from +3V to +15V. - Output with USB supply +12V, 300mA. - Time to build: Appr. 2.5 hours. - Cost of elements: Appr. USD 2.
- 4001 CMOS chip. - 4 NPN transistors. - 2 schottky diodes. - 7 resistors and 5 capacitors. - impulse transformer.
In the zip file (1.4MB) you will find:
- Circuit diagram with EAGLE PCB design. - LTspice simulation of the circuit. - Read me.pdf file with explanations and practical tips. - Pictures of the the device.
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