Abstract: A sensorless brushless-DC-motor mounted on an electric or hybrid vehicle is powered by an on-board battery through an inverter supplying a three-phase pulse width modulated voltage (PWM voltage). The inverter is controlled to generate the PWM voltage having an average voltage level corresponding to a target motor speed. The PWM voltage level is controlled by changing its duty ratio, so that a difference between the target motor speed and an actual motor speed is minimized. The actual motor speed is determined based on a signal indicating a rotor position detected from the PWM voltage imposed on the motor. When the battery voltage drops and the duty ratio becomes 100%, the target motor speed is temporarily reduced to the level of the actual motor speed. When the battery voltage is recovered and the duty ratio becomes lower than 100%, the target motor speed is gradually increased again to the original level.

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 control device controls operation of a brushless DC motor in such a way that the motor is started and accelerated up to a predetermined rotational speed by applying driving voltage formulated based on a synchronous signal under a startup-drive-mode and the driving mode is switched, after the predetermined rotational speed is established, to a self-controlled-drive-mode in which the driving voltage is formulated based on signals indicating an angular position of the rotor relative to the armature. In the transient period for switching-over from the start-up-drive to the self-controlled-drive, phase difference between the driving voltage and the rotor position signal is detected for a period covering more than one rotation of the rotor, the switching-over is carried out only when the phase difference is sufficiently small to avoid a motor stall or an excessive shock.

Abstract: In a driving system for vehicles having a high voltage main battery for a vehicle drive motor and a low voltage accessory battery for accessory devices such as a radio receiver, a three-phase inverter circuit for driving the vehicle drive motor and a DC-DC converter are connected to the main battery through electromagnetically shielded high voltage power lines. The DC-DC converter supplies a low voltage electric power to a driver circuit for switching on and off the inverter circuit. Switching noise voltages caused by switching operations in the inverter circuit, the driver circuit and the DC-DC converter are restricted from being superimposed on low voltage power lines connecting the accessory battery to the accessory devices.