JP2763393B

• Main Authors: SUWADA MAKOTO, USUI JUZO, INOE SHUICHI
• Format: Patent
• Language: English
• Published: 11.06.1998
• Edition: 6
• Subjects: AMPLIFIERS; BASIC ELECTRONIC CIRCUITRY; CONTROLLING; ELECTRICITY; PHYSICS; PULSE TECHNIQUE; REGULATING; SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES

A constant current circuit (1, 2, 3, 4) whose output current I2 can be varied with change of a power source voltage Vcc, and an oscillating circuit (5, 6, 7) whose oscillation frequency can be varied with change of the constant current circuit output current I2, suitable for use in portable computers. The constant current circuit comprises bipolar transistors (Q3, Q5) coupled to form a differential amplifier (3) wherein one of the transistors (Q3) is supplied with a reference voltage (V1) and the other (Q5) is supplied with a divided voltage of the power source voltage Vcc, and a resistor (R4) connecting the emitters of the transistors is provided for controlling the slope of the Vcc-I2 characteristic curve of the constant current circuit. The oscillating circuit comprises a capacitor (Co) charged by current I2, a switching means (SW) for discharging the capacitor when closed, and a voltage detecting means (D1) operating to close or open the switching means (SW) according to the voltage at one end of the capacitor (Co). Thus, the switching means switches on and off to generate pulses with a frequency depending on I2, hence, depending on Vcc. Methods for controlling the frequency range of the oscillating circuit and the rise time to fall time ratio of the pulses by introducing additional constant current supplying sources are also disclosed.