Overcurrent protection circuit

Abstract

The invention provides an over-current protection circuit which can rapidly detect the over-current status without damaging the stability of a circuit and implement the current limit and a voltage regulator using the over-current protection circuit. A voltage generation circuit (100) includes the regulator (10), a first detecting circuit (20) and a second detecting circuit (30). The first detecting circuit (20) includes a first transistor (22), a first resistance (R1) and an error amplifier (24). The second detecting circuit (30) includes a second transistor (32), a second resistance (R2) and a detecting transistor (34). When an output current (Iout) exceeds a detecting threshold current, the detecting transistor (34) is turned on for the feedback of the limitation of the output current on an operational amplifier (12). The detecting threshold current of the first detecting circuit (20) is arranged to be higher than the detecting threshold current of the second detecting circuit (30), and the detecting action speed is also arranged to be faster than the detecting action speed of the first detecting circuit (20).

Description

Technical field [0001] The present invention relates to an overcurrent protection circuit, and more particularly to a circuit protection technology for overcurrent of a voltage generating circuit used as a power supply circuit. Background technique [0002] In regulators that stabilize voltage, power MOSFETs (Metal Oxide Semiconductor Field Effect Transistor), IGBTs (insulated gate bipolar transistors), bipolar power transistors, etc. are used as output transistors. These transistors are designed to have a sufficient margin for the current value flowing during normal operation as the maximum allowable current. [0003] However, even in the case of such a design with sufficient design margin, if the output load circuit is short-circuited, an overcurrent exceeding the maximum allowable current flows through the transistor, and there is still a problem that affects its reliability. . In addition, even if it is below the maximum allowable current of the transistor, in order to protec...

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Problems solved by technology

[0006] However, as also pointed out in the above-mentioned literature, there is a problem that the protection circuit that detects the current flowing through the transistor and has a feedback current limiting function affects the stability of the circuit.

That is, when the frequency band of the feedback loop is enlarged to improve the followability to the fluctuation of the output current, the stability of the circuit is impaired, and there is a problem that the circuit tends to oscillate.

On the other hand, when the gain of the feedback loop is lowered and the frequency band is narrowed by prioritizing the stability of the circuit, in the case of forming a circuit that is less likely to oscillate, it cannot follow the sudden change of the output current, and it takes time to apply the current limit, and there is a current flow during this period. The problem of excessive current

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