Abstract: An electrical resource device of the present invention includes a current restriction portion for restricting current flowing in a semiconductor element based on a predetermined overcurrent restriction threshold by controlling the semiconductor element when the current detected by a current detecting portion exceeds the predetermined overcurrent restriction threshold. The predetermined overcurrent restriction threshold is defined based on a relationship between time and a change of a destruction current amount by which wiring may be destroyed, and is determined to be under the destruction current. Therefore, it is possible to prevent the wiring from being destroyed.

Abstract: A relay drive circuit includes a power supply circuit for producing a constant voltage, an initial energization circuit for performing an initial energization such that a power supply provides an initial energizing voltage to a relay, a low-holding energization circuit for performing a low-holding energization such that the constant voltage provides a constant current to the relay after the initial energizattion. Due to the low-holding energization, the relay contact can be firmly held even when relay coil resistance changes. The constant voltage for performing the low-holding energization is lower than the power supply voltage so that power consumption and heat generation can be reduced.

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 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 metal wiring board includes a metal plate as a substrate. The metal plate is stamped in a predetermined wiring pattern including wiring portions and terminal portions. The metal plate has soldering areas prepared for electrical connection and non-soldering areas coated with solder resist on its surface.

Abstract: An electrical resource device of the present invention includes a current restriction portion for restricting current flowing in a semiconductor element based on a predetermined overcurrent restriction threshold by controlling the semiconductor element when the current detected by a current detecting portion exceeds the predetermined overcurrent restriction threshold. The predetermined overcurrent restriction threshold is defined based on a relationship between time and a change of a destruction current amount by which wiring may be destroyed, and is determined to be under the destruction current. Therefore, it is possible to prevent the wiring from being destroyed.

Abstract: An intelligence power device (IPD), having a temperature-sensitive and heat-damage protecting function, is used as a semiconductor relay which controls load current supplied to an electric load. A target sensitive temperature T.sub.SD of IPD is determined according to an allowable load current value, using an equation T.sub.SD =I.sup.2 .times.R.sub.ON .times.R.sub.TEMP +T.sub.ROOM, where I represents an allowable load current value, R.sub.ON represents an on-resistance value of a power MOSFET, R.sub.TEMP represents a thermal resistance value of an entire radiation system of IPD, and T.sub.ROOM represents an ambient temperature of IPD. When the load current exceeds the allowable load current value, IPD stops the load current so that the load circuit can be prevented from being subjected to excessively large current.

Abstract: To provide a vehicular air conditioning system for activating an electric heater with the output coming from an inverter by actuating a relay at a reasonable cost, a relay and an electric heater acting as electric heat source are connected in series between an output line of three output lines of an inverter and the negative side of a vehicular power supply. The electric heater employs a nichrome wire as its heating element and is used for warming the inside of a vehicle compartment. Moreover, the relay is turned ON/OFF after the output voltage of the inverter is set to zero. As a result, the durability of the relay can be improved, and this relay can be implemented by an existing one without newly manufacturing any dedicated relay so that the cost can be lowered.

Abstract: A vehicle height sensor includes a switching circuit which is turned on and off in accordance with a vehicle height. When a drive signal is outputted to the vehicle height sensor, the vehicle height sensor is activated. A connector is connected to an output side of the switching circuit. A digital vehicle height data signal is transmitted from the switching circuit via the connector. A preset signal is outputted from the vehicle height sensor to the connector when a check signal is generated. The preset signal represents preset check data. A data receives the preset signal via the connector and reads the check data from the preset signal. The read check data is compared with a predetermined reference data. The connector is judged to be wrong when the read check data differs from the reference data.