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Input protection circuit

A technology for protecting circuits and input voltages, which is applied in the direction of emergency protection circuit devices, circuits, circuit devices, etc., and can solve problems such as the increase of leakage current that is difficult to allow and the influence of circuits

Active Publication Date: 2013-09-11
YOKOGAWA ELECTRIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It is difficult to allow the above-mentioned increase in leakage current in a circuit that performs analog voltage measurement with high precision such as the voltage measurement circuit 1
That is, the increase in leakage current as described above will have a bad influence on the circuit

Method used

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Experimental program
Comparison scheme
Effect test

no. 1 approach

[0037] Operation of the first embodiment

[0038] next to figure 1 The operation of the input protection circuit 10 of the first embodiment shown will be described in detail. When the input voltage Vin is within the power supply voltage range (VDD to VSS) of the voltage measurement circuit 1, the magnitude of the voltage between the gate and the source of the NMOSFET4 and PMOSFET5 becomes a predetermined voltage│Vs regardless of the input voltage Vin │. However, the predetermined voltage |Vs| is set to a minimum value for turning on the NMOSFET 4 and the PMOSFET 5 . Therefore, when the input voltage Vin is within the power supply voltage range (VDD-VSS), the NMOSFET4 and the PMOSFET5 are turned on. The voltage Vic is input to the voltage measurement circuit 1 through the NMOSFET4 and the PMOSFET5. As a result, the voltage measurement circuit 1 can measure the input voltage Vin with high precision.

[0039] When the input voltage Vin is higher than the positive power supp...

no. 2 approach

[0061] Operation of the second embodiment

[0062] next to figure 2 The operation of the input protection circuit 20 of the second embodiment shown will be described in detail. When the input voltage Vin is within the power supply voltage range VDD−Vs to VSS+2Vs, the voltage between the gate and the source of the PMOSFET 25 and the PMOSFET 26 is maintained at a predetermined value Vs. PMOSFET25 and PMOSFET26 are turned on to maintain a low resistance state. In this case, the voltage drop in PMOSFET25 and PMOSFET26 is small. Therefore, the output voltages V1 and V2 of the gate bias circuit 24 are applied to the gate terminals of the respective NMOSFET 4 and PMOSFET 5 at the same level. Thereby, the voltage between the gate and the source of NMOSFET4 and PMOSFET5 is also maintained at predetermined value Vs. NMOSFET4 and PMOSFET5 are turned on and maintained in a low resistance state. The input voltage Vin is input to the voltage measurement circuit 1 by turning on the NMO...

no. 3 approach

[0102] Operation of the third embodiment

[0103] next to Figure 6 and Figure 7 The operation of the input protection circuit 30 of the third embodiment shown will be described in detail.

[0104] First, the normal operation of the input protection circuit 30 will be described. The normal operation is the operation of the input protection circuit 30 when the input voltage Vin is within the range of the power supply voltage VDD−Vs to VSS+Vs of the voltage measurement circuit 1 . In this case, the voltage between the gate and the source of the PMOSFET 25 is maintained at a predetermined value Va. Therefore, PMOSFET 25 is turned on and maintains a low resistance state. Therefore, the voltage drop in PMOSFET 25 is small. Therefore, the output V1 of the gate bias circuit 34 is applied to the gate terminal of the NMOSFET 4 as it is. Therefore, the voltage between the gate and the source of the NMOSFET 4 is also maintained at the predetermined value Vs. Therefore, NMOSFET 4 ...

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Abstract

An input protection circuit (10, 20, and 30) includes: a first transistor (4) of a field-effect type coupled in series between an input terminal (3) and an electronic circuit (1), the input terminal (3) receiving an input voltage, the electronic circuit (1) receiving an input voltage (Vin), the first transistor (4) switching to an off-state in a case where the input voltage is higher than a positive power supply voltage (VDD) of the electronic circuit; a second transistor (5) of a field-effect type coupled in series between the first transistor and the electronic circuit, the second transistor switching to an off-state in a case where the input voltage is lower than the negative power supply voltage (VSS) of the electronic circuit; and a voltage control circuit (11, 24, and 34) configured to maintain gate-source voltages of the first transistor and the second transistor as voltages within a power supply voltage range of the electronic circuit based on the input voltage.

Description

[0001] Cross References to Related Applications [0002] This application is based on the Japanese Patent Application No. 2012-46934 submitted to the Japan Patent Office on March 2, 2012 and the Japanese Patent Application No. 2012-274206 submitted to the Japan Patent Office on December 17, 2012, so all of the Japanese Patent Application The contents are incorporated herein by reference. technical field [0003] The present invention relates to input protection circuits. Background technique [0004] Electronic devices such as voltage measuring devices that measure input voltage with high precision include devices with input protection circuits. The input protection circuit protects the internal circuit when excessive voltage is applied to the input terminal. Figure 8 An example of an input protection circuit in a conventional electronic device is shown. The input protection circuit 2 protects the voltage measurement circuit 1 from excessive input voltage Vin. The voltag...

Claims

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Application Information

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IPC IPC(8): G01R1/36
CPCH01L27/0285H02H9/046H01L27/04H02H3/207
Inventor 安田和秀萩原宏章
Owner YOKOGAWA ELECTRIC CORP