Current-limiting circuit

Abstract

The invention discloses a current-limiting circuit which comprises a first resistor (R1), a second resistor (R2), a third resistor (R3), a fourth resistor (R4), a fifth resistor (R5), a sixth resistor (R6), a seventh resistor (R7), an eighth resistor (R8), a first capacitor (C1), a first triode (T1), a second triode (T2), a third triode (T3), a fourth triode (T4) and a voltage stabilizing circuit (100). The voltage stabilizing circuit provides bias to a base electrode of the fourth triode through the eighth resistor, voltage drop of the fifth resistor during normal running is small, the fourth triode can be conducted by slight voltage rise of the fifth resistor when in over current of an output end, then the third triode is in saturated conduction so as to cut off the second triode and the first triode, so that current limit protection is realized. Once circuit protection is started, the seventh resistor maintains the protection state of the circuit. The current-liming current is quick in response, capable of resetting automatically, is small in size, low in voltage drop, low in maintenance current and heating volume after being protected.

Description

technical field [0001] The invention relates to a current limiting circuit, in particular to a recoverable current limiting circuit in a direct current circuit. Background technique [0002] There are many kinds of current-limiting circuits or devices. The fuse invented by the American inventor Thomas Alva Edison (Thomas Alva Edison, 1847-1931) more than a hundred years ago is a current-limiting device. The fuse (fuse) is also called a current fuse. IEC127 The standard defines it as a "fuse-link". [0003] Table 1 shows the electrical characteristics of the ultra-fast-acting fuses in the prior art, which meet the certification standards of CCC in China and UL in the United States. [0004] Table I [0005] [0006] From Table 1, we can see the characteristics of the fuse in the prior art. When the current is 200% of the rated current, the fusing time is allowed to be as long as 1 second, and the actual measurement is above 300mS, that is, more than 0.3 seconds. Exclude...

AI Technical Summary

Problems solved by technology

[0025] 1. The fuse in the prior art has the disadvantages of long fusing time and non-recovery after fusing;

[0026] 2. The self-recovery fuse reacts slowly when over-current, and there is still a large maintenance current after protection; after the working voltage changes, it is necessary to re-select the model, which is inconvenient to use;

[0027] 3. The electronic fuse using the sampling coil has a large volume and cannot perform current limiting protection on the DC circuit;

[0028] 4. Other current-limiting circuits used in DC circuits have large voltage drops and cause large losses. Only a large heat sink can be added to the device to work normally, and the cost is relatively high

[0029] So far, there is no low-cost low-dropout interception protection circuit

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