This is circuit 13.8V, 40A Switching Power Supply,It is high current power supply switching regulator.And Nice Circuit for power user. This article was originally published (in a slightly modified form) in the QST magazine, December 1998 and January 1999, and in the Radio Amateur's Handbook, 1999. Visit the American Radio Relay League for information on these publications, and a world of ham radio related things! Design decisions There are several different topologies for switchers in common use, and the first decision a designer must take is which of them to consider. Among the factors affecting the decision are the power level, the number of outputs needed, the range of input voltage to be accepted, the desired tradeoff between complexity, quality and cost, and many more. For this power supply I decided to use the half bridge forward converter design. This topology connects the power transformer to a bridge formed by two power transistors and two capacitors. It is reasonably simple, puts relatively low stress on the power transistors, and makes efficient use of the transformer's magnetic capabilities.The second basic decision is which switching frequency to use. The present trend is to use ever higher frequencies. But by doing so it becomes more difficult to filter out the RF noise inevitably generated by the switching. So I decided to stay at a low switching frequency of only 25 kHz for the full cycle, which due to the frequency doubling effect of the rectifiers results in 50 kHz on the output filter. For the main switching elements, bipolar transistors or MOSFETs can be used. Bipolars have lower conduction losses, while MOSFETs switch faster. As in this design I wanted to keep the RF noise at an absolute minimum, very fast switching was not desired, so I used bipolar transistors. But these tend to become too slow if the driving is heavier than necessary. So, if the transistors have to switch at varying current levels, the drive to them must also be varied. This is called proportional driving, and is used in this project. The half bridge converter is best controlled by pulse width modulation. There are several ICs available for this exact purpose. I chose the 3524, which is very simple to use and easy to find. Any 3524 will do the job. It can be an LM3524, SG3524, etc. This basically ends the big decisions. From now on, designing the circuit is a matter of calculating proper values for everything.
Ahmet UZUN on 18 Mar 12" Precision Power Supply © 1986 Doug Bedrosian and 2010 Tony van Roon "This Precision Power Supply is a nice addition on your workbench as primary, or in my case, a supplementary power supply. With zero to 40V and 2A with adjustable current limiting it will surely gets lots of use on your bench. On average the most amperage for a power supply someone needs is around two or three amps. The sensitivity for current limiting is fully adjustable. Have fun building!" Introduction: Test instruments are considered to be some of the most useful tools available when constructing a project. They are also considered to be the most expensive tools one could buy. For instance, a power supply of any quality and usefulness can range from several hundred dollars to several thousand dollars. The alternative to buying a power supply is to build one. The power supply in this article has a voltage range from 0 to 40V and a current range from 0 to 2 amps with current limiting set by the user. The quality of the supply is determined by the time and care the builder takes while constructing it. How It Works: The power supply is best understood when divided into separate parts. The first parts to look at are the two power supply sections. The output supply section consists of XFMR1, Br1, C1, and C2. They supply the appropriate voltage and current required at the output. The IC supply consists of XFMR2, Br2, and C3. The two power supply sections must be separate from each other because a floating ground is required for IC1. The next section is the voltage control. RV1 and R2 determine the operating point of a constant current source out of pin 3 of IC1. By varying RV1 the maximum output voltage will be set. Pins 8 and 9 are inputs to a high gain differential amplifier contained in IC1. By adjusting potentiometer P1 the voltage at pin 8 will vary; this will cause the voltage at the output to change until it is equal to the voltage at pin 8. Due to the high gain of the differenti