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US 7,064,553 B2Granted
Open-circuit detecting circuit
AssigneesAnden Co., Ltd., Denso Corporation
InventorsShinji Tani, Yoshichika Abe
Life of this patent
Estimating the term…
Abstract
In an open-circuit detecting circuit, a current detecting circuit converts current flowing from a driving circuit to a load to a voltage. A comparator circuit compares the voltage with a reference voltage and outputs a signal according to a result of the comparison to a D flip-flop. An open-circuit is determined based on an output of the flip-flop, which is outputted when a clock signal indicating a falling edge of a PWM signal outputted from a PWM signal generating circuit is inputted.
Claims11
An open-circuit detecting circuit comprising:
- a driving circuit for controlling power supply to a load;
- an on-off signal generating circuit for generating a on-off signal for controlling power supply to the driving circuit;
- a current detecting circuit for converting current flowing from the driving circuit to the load to a voltage;
- a comparator circuit for comparing the voltage with a reference voltage and outputs a signal according to a result of the comparison;
- and
- a storage circuit for storing the result of the comparison until a falling edge appears in the on-off signal
- wherein:
- the driving circuit is a switch connected between a power source and the load;
- the current detecting circuit obtains a voltage calculated by subtracting a voltage drop at the driving circuit from a source voltage, determines the calculated voltage as the voltage converted from the current flowing from the driving circuit to the load, and outputs the calculated voltage to the comparator circuit;
- the load is a light emitting diode indicator unit having a plurality of lines of light emitting diodes, the lines connected in parallel to each other;
- and
- the reference voltage is set to a voltage calculated by adding a variation in a voltage drop at the driving circuit when a predetermined number of light emitting diode lines become open to the voltage converted from the current flowing from the driving circuit to the load.
9 more elements
A detecting circuit comprising:
- a driving circuit switchably controlling a power supply to a load, the driving circuit driven by a pulse width modulation (PWM) signal;
- a current detecting circuit converting a current flowing from the driving circuit to the load to a voltage;
- a comparator circuit comparing the voltage with a reference voltage and outputting a signal according to a result of the comparison;
- and
- a storage circuit coupled to the comparator circuit and the PWM signal, the storage circuit storing the result of the comparison based on a state of the PWM signal,
- wherein:
- the current detecting circuit obtains the voltage by:
- subtracting a voltage drop at the driving circuit from a source voltage to generate a subtracted voltage,
- determining that the subtracted voltage is the voltage converted from the current flowing from the driving circuit to the load, and
- outputting the subtracted voltage to the comparator circuit as the voltage;
- the load includes a light emitting diode indicator unit having a plurality of lines of light emitting diodes, the lines connected in parallel to each other;
- and
- the reference voltage is set by adding a variation to the voltage drop at the driving circuit when a predetermined number of light emitting diode lines become open to the voltage converted from the current flowing from the driving circuit to the load.
10 more elements
Dependencies are inferred from the claim text.