Electricity: measuring and testing – Electric lamp or discharge device – Electric lamp
Reexamination Certificate
2002-10-25
2004-05-18
Deb, Anjan K. (Department: 2858)
Electricity: measuring and testing
Electric lamp or discharge device
Electric lamp
C324S537000, C324S511000, C327S536000
Reexamination Certificate
active
06737868
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-342102 filed on Nov. 7, 2001.
FIELD OF THE INVENTION
The present invention relates to an electrical load disconnection detecting apparatus.
BACKGROUND OF THE INVENTION
An electrical load disconnection detecting apparatus is shown in FIG.
8
. This apparatus is especially used in a vehicle for detecting disconnection of electrical loads, such as taillights or stoplights. The apparatus includes a differential amplifier circuit
14
, a noninverting amplifier circuit
16
, and a microcomputer
18
. A resistor
12
for current-voltage conversion is connected in series with a path for supplying a current to lamps L
1
-Ln.
Voltages that appear at each end of the resistor
12
are inputted to the differential amplifier circuit
14
. An output Vout
1
of the differential amplifier circuit
14
is amplified by the noninverting amplifier circuit
16
. The amplified voltage Vout
2
is inputted to the microcomputer
18
and compared with a reference to determine whether disconnection exists.
In this apparatus, two amplifiers
20
,
25
, one is for the differential amplifier circuit
14
and the other is for the noninverting amplifier circuit
16
, are required. This makes the apparatus large and costly.
SUMMARY OF THE INVENTION
The present invention therefore has an objective to reduce the size and the cost of the electrical load disconnection detecting apparatus.
The electrical load disconnection detecting apparatus of the present invention includes a resistor for current-voltage conversion, a differential amplifier circuit, a disconnection detecting device, and a charge pump circuit. The resistor is connected in series with a path for supplying power to an electrical load to be monitored. Voltages that appear at the ends of the resistor are inputted to the differential amplifier circuit. The charge pump circuit increases the battery voltage and supplies the increased voltage to an operational amplifier included in the differential amplifier circuit.
Because the operational amplifier is supplied with the amplified operating voltage, it can output an amplified output voltage to the detecting device. Therefore, the detecting device can perform accurate detection. Furthermore, the charge pump circuit can be constructed small and at low cost as compared with the noninverting amplifier circuit.
REFERENCES:
patent: 4894648 (1990-01-01), Talbot
patent: 5337013 (1994-08-01), Langer et al.
patent: 5589802 (1996-12-01), O'Shaughnessy et al.
patent: 6611166 (2003-08-01), Chan et al.
patent: A-S56-121296 (1981-09-01), None
patent: A-H07-201471 (1995-08-01), None
patent: A-2000-74977 (2000-03-01), None
Deb Anjan K.
Posz & Bethards, PLC
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