Abstract: A power source unit includes an inverter connected to a power transfer device, a first battery that can be charged and discharged through the inverter and a second battery that can be charged and discharged through the inverter. The second battery has a power voltage lower than that of the first battery. The power source unit further includes a power conversion device connected to the inverter, providing a transforming function, and a switching device provided between the power conversion device and the first and second batteries. The switching device switches a connection between the power conversion device and the first battery, and the power conversion device and the second battery. The inverter is connected to the first and the second batteries through the power conversion device.

Abstract: Power from a high voltage battery (10) (for example 36V) is supplied through an inverter (12) to a motor generator (14). A low voltage battery (20) (for example 12V) is connected through a reactor (18) to the neutral point of the motor generator (14). A voltage ratio of the low voltage battery (20) to the high voltage battery (10) is preferably from 1:2 to 1:4. In order to set the neutral point voltage to a desired charging voltage into the low voltage battery (20), the inverter (12) is controlled so as to follow a current distortion phenomenon. In this way, in a dual-power source system with a voltage ratio of a low voltage battery (20) to a high voltage battery (10) between 1:2 and 1:4, voltage switching means for use in charging a charge voltage of a high voltage side into a low voltage source can be implemented at low cost.

Abstract: A voltage conversion apparatus is connected between a first charging/discharging device and a second charging/discharging device, and performs voltage conversion between the first and second charging/discharging devices. The apparatus includes a first switching device having one terminal connected to the first charging/discharging device, a second switching device connected between the other terminal of the first switching device and the earth, a third switching device having one terminal connected to the second charging/discharging device, a fourth switching device connected between the other terminal of the third switching device and the earth, and a coil provided between the other terminal of the first switching device and the other terminal of the third switching device.

Abstract: A vibration-sensing gyro composed of a light alloy such as duralumin includes a base and a first pair of tines projecting parallel to each other from the base. Piezoelectric elements are mounted on the root of the side faces of the first pair of tines to excite the first pair of tines along an X axis. The vibrations of the first pair of tines along the X axis are then propagated to a second pair of tines to vibrate the second pair of tines along the X axis. Piezoelectric elements are mounted on the root of the upper and the lower faces of the second pair of tines to detect vibrations of the second pair of tines along an Y axis. When the second pair of tines receives the Coriolis force based on an angular velocity .omega. around a Z axis and vibrates along the Y axis, the vibrations along the Y axis are detected as electric signals (alternating current voltages) by piezoelectric effects of the piezoelectric elements.

Abstract: A pulse width modulation circuit includes an operation unit which generates a compensation signal based on the product of a deviation of an input signal from a first reference value and a deviation of a power supply voltage from a second reference. A level change unit changes the level of at least one of an error signal from an error amplifier and a reference wave signal generated by a reference wave signal generator in accordance with the compensation signal so that a relative level defined by a level difference between the error signal and the reference wave signal changes in accordance with the compensation signal. The pulse width modulation circuit also includes a unit for comparing the level of the error signal and the level of the reference wave signal having a changed relative level with each other and for generating a pulse width modulated signal based on a comparison result.