Shin-ichi Ohashi

100 Watt Super Audio Amplifier Using New Mos Devices

A 100 watt audio amplifier was recently developed using a new Power MOSFET which was developed by our MOS Device Group. The Power MOSFET has several advantages over bipolar transistors. It has good frequency response, no carrier storage delay, thermal stability, no secondary breakdown and high input impedance.

Multi channel PWM power invertors integrated in a switching power supply circuit

A description is given of a PWM (pulse-width modulated) power inverter circuit integrated into a conventional switching power-supply circuit. The output current of the switching power supply is distributed to several output loads by a time-sharing scheme using a PWM switching network that uses input voltage values to determine which load is energized. This circuit configuration eliminates choke coils and pulse-width modulator circuits, which are indispensable in conventional PWM power inverter circuits. The method will increase power efficiency, the cost-performance ratio, and the compactness of resulting devices, e.g. consumer electronic products and robotic systems. To verify the proposed scheme, a three-channel inverter was constructed and its DC pulse and AC output characteristics were measured. The circuit was of the flyback type, its left side being the primary switching circuit and the right side containing the output switching circuits for positive and negative DC/pulse and AC output voltages. The maximum output power was 50 W, and the power efficiency was 60% (approximately) at the switching frequency of 50 kHz. >

CD-4 IC'S for High-Quality Demodulators for 4-Channel Discs

This paper reports improvements on the CD-4, discrete four-channel stereo system including newly developed integrated circuits. Up to now, the CD-4 systems have been considered to possess several disadvantages in performance compared with conventional two-channel stereo systems. These disadvantages were, for example, unsatisfactory signal-to-noise ratio (S/N), frequency response, distortions and unusual shock noises in the absence of a subcarrier as well as cross-modulation between the main and subchannels.