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

Inactive Publication Date: 2007-06-27
ROHM CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] However, even in the case of such a design with a sufficient margin, in the case of a short-circuit of the output load circuit, etc., a large overcurrent exceeding the maximum allowable current flows through the output transistor, which may affect its reliability. question
In addition, even below the maximum allowable current of the output transistor, there are cases where it is desirable to limit the current in order to protect the load circuit connected to the regulator

Method used

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

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Embodiment Construction

[0037] FIG. 1 is a circuit diagram showing a power supply device 100 according to an embodiment of the present invention. In the following figures, the same reference numerals are assigned to the same constituent elements, and descriptions thereof are appropriately omitted.

[0038] The power supply device 100 includes a regulator 10 and an overcurrent protection circuit 20 that adjust the output voltage to a certain value based on a reference voltage. The overcurrent state of the regulator 10 is detected by the overcurrent protection circuit 20 , and the driving capability of the voltage regulator 10 is reduced when overloaded or when the load is short-circuited.

[0039]The power supply device 100 is integrated on a semiconductor substrate, and includes an input terminal 102 and an output terminal 104 . The voltages applied or presented to the respective terminals are referred to as input voltage Vin and output voltage Vout. The load circuit 50 is connected to the output t...

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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.

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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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G05F1/56H02H9/02G05F3/24
CPCG05F1/575G05F3/24H02H9/02
Inventor 石野勉
Owner ROHM CO LTD
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