# US 5,345,181 A · Circuit for a detecting state of conduction of current through a solenoid

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- Number: US 5,345,181 A
- Document ID: US5345181A
- Status: Granted
- Kind: A
- Application number: 07/914,785
- Filed: 1992-07-16
- Granted: 1994-09-06
- Earliest claimed: 1991-07-19
- Assignees: Yamaha Corporation
- Inventors: Rokurota Mantani; Yasutoshi Kaneko; Takashi Tamaki
- Web page: https://patentgrep.com/patent/US5345181A

## CPC

- G01R 31/72: Testing of electric windings (testing of transformers G01R31/62)
- G01R 31/2829: {Testing of circuits in sensor or actuator systems (testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844)}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A circuit is provided for detecting abnormal conduction of current conducted through a solenoid in response to the pulse width modulation signal. The circuit includes a measuring means, for detecting conduction current conducted through the solenoid in response to the pulse width modulation signal and measuring continuous conduction time of the conduction current, and determining means, for determining a conduction to be an abnormal conduction when the continuous conduction time is longer than a predetermined time. Thus, the circuit can be miniaturized and the accuracy of the circuit is not affected by the accuracy of its components. And, the circuit is capable of detecting the half short state of the transistor driving the solenoid and not malfunctioning even if tile power is turned off.

## Claims

### Claim 1

A circuit for detecting abnormal conduction of current conducted through a solenoid comprising;
a first means for receiving a charge and discharging a charge, said first means being at least one of charged and discharged in response to said current conduction by said solenoid, said solenoid conducting said current in response to a pulse width modulation signal;
detecting means for comparing the electric potential of said first means with a predetermined electric potential to detect said abnormal conduction of current in said solenoid;
second means for at least one of charging and discharging said first means when a voltage greater than a predetermined amount is applied to said solenoid; and
preventing means for preventing at least one of the charge and discharge of said first means when a power supply voltage applied to said solenoid is turned off.

### Claim 2 (depends on 1)

The circuit according to claim 1, further comprising:
measuring through said solenoid, said measuring means including time measuring means for measuring a continuous conduction time of said conduction current; and
determining means for determining when said continuous conduction time is longer than a predetermined time.