Abstract: An indicator system having light emitting diode (LED) indicators and an open-circuit detecting circuit. In the open-circuit detecting circuit, a voltage at a point between a constant current source and the first resistor is applied to a base of a transistor. The second resistor is connected in parallel between the base and an emitter of the transistor. The third and the fourth resistors are connected in series between the constant current source and a collector of the transistor. The fifth resistor is connected between the emitter of the transistor and the first resistor. The threshold determining circuit determines a voltage at a point between the third and the fourth resistors as a threshold voltage. With this configuration, the threshold voltage can be adjusted according to the resistance of the first resistor.

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.

Abstract: A control device of LEDs includes a lighting-up circuit and a lighting-out circuit, both of which generate pulse signals being pulse-width modulated by varying cycles and corresponding duty ratios based on an input signal during a start-up period and a falling period, respectively. The control device then provides LEDs with the electric current relative to the pulse signals. Both of the lighting-up circuit and lighting-out circuit vary the cycles and corresponding duty ratios of the pulse signals, so that a luminance variation characteristic of the LEDs becomes nonlinear, leading to being approximated to a luminance variation characteristic of an electric bulb.

Abstract: A vehicle direction indication device is configured such that a voltage of a battery power supply is detected, and when a direction indication light switch is switched to ON, a pulse width modulated signal is output. This pulse width modulated signal is generated by pulse width modulating a flash signal for driving a direction indication light in a flashing manner with a duty ratio based upon the detected voltage of the battery power supply; the duty ratio at which the voltage of the battery power supply is high becomes smaller than that at which the voltage of the battery power supply is low. The direction indication light is then driven in the flashing manner based upon the output signal.

Abstract: A flasher circuit included in a vehicular turn signal indicator system has a flashing control circuit, a flashing relay, a current detecting resistor, and a switching circuit. The control circuit detects a voltage drop across the resistor during driving of light bulb indicator lamps and light emitting diode (LED) indicator lamps of the system. Each LED lamp is configured to output a disconnection signal if at least one of their LEDs is disconnected during the driving. The signal turns on a transistor of a switching circuit, resulting in short across the resistor. As a result, the voltage drop is lowered equal to or under the threshold value, and the control circuit starts the disconnection detection.

Abstract: In an open-circuit detecting circuit, a current detecting circuit converts current flowing form 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.

Abstract: An indicator system having light emitting diode (LED) indicators and an open-circuit detecting circuit. In the open-circuit detecting circuit, a voltage at a point between a constant current source and the first resistor is applied to a base of a transistor. The second resistor is connected in parallel between the base and an emitter of the transistor. The third and the fourth resistors are connected in series between the constant current source and a collector of the transistor. The fifth resistor is connected between the emitter of the transistor and the first resistor. The threshold determining circuit determines a voltage at a point between the third and the fourth resistors as a threshold voltage. With this configuration, the threshold voltage can be adjusted according to the resistance of the first resistor.

Abstract: A vehicle direction indication device is configured such that a voltage of a battery power supply is detected, and when a direction indication light switch is switched to ON, a pulse width modulated signal is output. This pulse width modulated signal is generated by pulse width modulating a flash signal for driving a direction indication light in a flashing manner with a duty ratio based upon the detected voltage of the battery power supply; the duty ratio at which the voltage of the battery power supply is high becomes smaller than that at which the voltage of the battery power supply is low. The direction indication light is then driven in the flashing manner based upon the output signal.

Abstract: A control device of LEDs includes a lighting-up circuit and a lighting-out circuit, both of which generate pulse signals being pulse-width modulated by varying cycles and corresponding duty ratios based on an input signal during a start-up period and a falling period, respectively. The control device then provides LEDs with the electric current relative to the pulse signals. Both of the lighting-up circuit and lighting-out circuit vary the cycles and corresponding duty ratios of the pulse signals, so that a luminance variation characteristic of the LEDs becomes nonlinear, leading to being approximated to a luminance variation characteristic of an electric bulb.

Abstract: A flasher circuit included in a vehicular turn signal indicator system has a flashing control circuit, a flashing relay, a current detecting resistor, and a switching circuit. The control circuit detects a voltage drop across the resistor during driving of light bulb indicator lamps and light emitting diode (LED) indicator lamps of the system. Each LED lamp is configured to output a disconnection signal if at least one of their LEDs is disconnected during the driving. The signal turns on a transistor of a switching circuit, resulting in short across the resistor. As a result, the voltage drop is lowered equal to or under the threshold value, and the control circuit starts the disconnection detection.

Abstract: Left and right turn lamps are used as lamps in a daytime travel of a vehicle. When a first daytime turn-on requirement is satisfied, i.e., when an ignition switch is ON, a left-hand contact of a turn switch is OFF, a right-hand contact thereof is off, and the like, a left front turn lamp and a right front turn lamp are turned on as the lamps in the daytime travel, based on signals outputted from first and second AND logic circuits. When the left-hand contact of the turn switch is turned on in this state, the left front turn lamp flashes, based on a signal outputted from a flasher circuit, whereas the right front turn lamp keeps a turn-on state. On the other hand, when the right-hand contact of the turn switch is turned on, the right front-turn lamp flashes, based on a signal outputted from the flasher circuit, whereas the left front turn lamp keeps a turn-on state.

Abstract: Left and right turn lamps are used as lamps in a daytime travel of a vehicle. When a first daytime turn-on requirement is satisfied, i.e., when an ignition switch is ON, a left-hand contact of a turn switch is OFF, a right-hand contact thereof is off, and the like, a left front turn lamp and a right front turn lamp are turned on as the lamps in the daytime travel, based on signals outputted from first and second AND logic circuits. When the left-hand contact of the turn switch is turned on in this state, the left front turn lamp flashes, based on a signal outputted from a flasher circuit, whereas the right front turn lamp keeps a turn-on state. On the other hand, when the right-hand contact of the turn switch is turned on, the right front turn lamp flashes, based on a signal outputted from the flasher circuit, whereas the left front turn lamp keeps a turn-on state.

Abstract: A driving circuit for the electromagnetic relay provides a coil of the electromagnetic relay with stepped voltage having a first voltage which is slightly larger than a minimum operating voltage which caused the coil to generate magnetic field capable of closing contacts of the electromagnetic relay and a second voltage higher than the first voltage, in response to a triggering signal to trigger the electromagnetic relay. According to this structure, because the first voltage lower than the second voltage is applied to the coil firstly, the contacts are closed by attracting force of the coil risen gently. As a result, the bouncing of the moving contact can be prevented. In addition, the response time required for the closing of the contacts can be prevented to become long.