Circuit protection method, protection circuit and power supply device using the protection circuit

A technology for protecting circuits and power supply devices, which is applied in emergency protection circuit devices, emergency protection circuit devices for limiting overcurrent/overvoltage, circuit devices, etc., and can solve problems such as reliability impact
CN1989467AInactive Publication Date: 2007-06-27ROHM CO LTD
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Patent Information

Authority / Receiving Office
CN Β· China
Patent Type
Applications(China)
Current Assignee / Owner
ROHM CO LTD
Publication Date
2007-06-27
Estimated Expiration
Not applicable Β· inactive patent

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Abstract

An excess current protection circuit which can change a limited current corresponding to an output voltage by simple constitution. A power supply device (100) is provided with a regulator (10), which regulates the output voltage to be constant based on a reference voltage, and an excess current protection circuit (20). The regulator (10) is a general three-terminal regulator which includes an output transistor (14), an error amplifier (12) and resistors (R1, R2). The excess current protection circuit (20) detects an output current (Iout) by a first transistor (M1), and converts it into a voltage by a variable resistor (Rvar). A voltage comparator (24) compares the voltage with a threshold voltage (Vth) corresponding to a limited current and detects an excess current status. A current adjusting circuit (26) drops driving performance of the regulator (10) when the excess current status is detected, and protects the circuit. The resistance value of the variable resistor (Rvar) is set based on an output voltage (Vout), and a value of the limited current is changed corresponding to the output voltage.
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Description

technical field

[0001] The present invention relates to a protection circuit, in particular to an overcurrent protection technology of the circuit. Background technique

[0002] In a voltage stabilizer or the like, a power MOSFET (Metal Oxicide Semiconductor Field Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor), and a bipolar power transistor are provided as output transistors. Wait. These transistors are designed to have a sufficient margin for the current value that flows during normal operation as the maximum allowable current.

[0003] However, even if it is designed to have a sufficient margin in this way, when the output load circuit is short-circuited or the like, a large overcurrent exceeding the maximum allowable current flows through the output transistor, which affects the reliability of the output transistor. question. In addition, even if the output transistor's maximum allowable current is less than or equal to the maximum allowable current o...

Claims

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