The article had introduced to shed protective principle, introduced to had been taken in detail shed source of protective dc Electromechanical to devise a method, the power source of small-power dc electric machinery that uses design of LM317 compositive manostat, circuit structure is simple, efficiency is tall, cost is low, output voltage performance is good, having very good application perspective.

Foreword
　　　
Current, products of all sorts of direct current source are flooding the market, power source technology has matured quite. However, be based on the consideration of cost, asking to power source function is not very tall circumstance, can use had contained the circuit of compositive stabilized voltage that sheds protection, can satisfy the requirement of the product likewise.
　　　
Shed an indispensable component in protecting circuit to regard power source as circuit too, its control method can divide the basis to break means and current limliting pattern to close roughly, and dc Electromechanical source relatively appropriate is used involve kind.
　　　
Shed protective circuit to want to have link of sampling of an electric current above all too, commonly used practice is series connection component of suddenly perhaps Er comes to a little resistance obtain voltaic signal. Because volume of suddenly Er component is larger, the price is high, consequently the consideration introduces series the method of a little resistance.
　　　
　　 1, working principle
　　　
If the graph is shown 1 times,had led the circuit of LM317 stabilized voltage that sheds protective function, circuit of compositive stabilized voltage is divided commonly for 5 parts, communicate step-down circuit, rectification circuit, filter wave circuit, stabilized voltage circuit, protection circuit namely. Commutate of step-down of transformer of power source of classics of communication 220V voltage gets volts d.c. Vin, this voltage inputs compositive manostat to input end through filter wave circuit, in compositive manostat output is carried attainable volts d.c. of 1.25 ～ 37V. If working principle graph and weaveform of each part voltage pursue 2 are shown. Land please: ? of pole of uncut jade of Mian Lai white browses more information

Land please: ? of pole of uncut jade of Mian Lai white browses more information

Origin: Pole of uncut jade of Mian Lai white?

Graph the 1 LM317 that contains protection stabilizes circuit


Graph origin of block diagram of 2 dc regulated power supply: WWw.tede.cn

The analysis protects the working process of circuit below.
The protection of 1.1 compositive manostat
　　　
To obtain higher output voltage is worth, the adjustment of LM317 manostat the resistor R2 value between end and ground and its are pressed fall often bigger, in R2 two end receive a capacitance C3 that is less than 10μF, can restrain the ripple that outputs end effectively. When input end or output end short-circuit, the discharge of capacitance C3 will pound voltage in the generation on R1, can endanger the fiducial voltage circuit of manostat, because this needs in R1 two carry and diode D3 in order to protect manostat.
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