High efficiency, light weight audio amplifier and power supply
First Claim
1. An apparatus for amplifying an audio signal having an amplitude which varies at an audio frequency, said apparatus comprising(a) audio amplifier means for amplifying the audio frequency amplitude variations of the audio signal to produce an output signal corresponding to the audio signal, said amplifier means including an audio signal receiving means for receiving the audio signal and a power receiving means for receiving electrical energy for producing the output signal;
- (b) power supply means for supplying power to said amplifier means, said power supply means adapted to be connected with a source of commercially available, sinusoidally varying supply voltage having a constant frequency within the audio range, a transformer having a primary winding and a secondary winding, said secondary winding being operatively connected to said power receiving means of said amplifier means, said primary winding being adapted to be connected to said source;
(c) power control means to cause variable amounts of electrical energy to be transmitted to the primary winding of the transformer to induce corresponding variable electrical energy in said secondary winding, said power control means including switch means connected between said source and said primary winding for operating in a conductive state in response to a control signal for a selected portion of each cycle of said sinusoidally varying supply voltage to cause said selected portion of said sinusoidally varying supply voltage to be applied across said primary winding only when said switch means is in said conductive state; and
(d) control signal generating means responsive to the time varying amplitude of the audio signal to generate said control signal for said power control means to control the period of conduction of said switch means during each cycle of said sinusoidally varying supply voltage in correspondence with the time varying amplitude of the audio signal to minimize the time portion of each cycle of sinusoidally varying supply voltage during which idling currents pass through said primary winding.
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Accused Products
Abstract
The present invention comprises an amplifier circuit (2, 1100, 1500, 1600) and transformer based power supply (24, 500, 700, 1710) wherein greater efficiency is achieved by using the input signal characteristics to control various aspects of the circuit operation. The transformer primary winding (8, 500a, 700a, 1710a) is energized by a pulsed power supply (6, 502, 702, 1702) which is duty cycle modulated in response to the signal being amplified. One embodiment of the amplifier employs output transistors (Q1101, Q1103, Q1105, Q1107, Q1109, Q1111) connected to respective stepped voltage levels. Amplifier control circuitry (1126, 1130, 1138, 1140) acts in relation to the input signal amplitude to more evenly distribute the voltage drop across the interconnected transistors (Q1101, Q1103, Q1105, Q1107, Q1111), thus reducing amplifier power requirements and minimizing distortion in the amplifier output. In another embodiment, a stereo amplifier constructed in accordance with the present invention contains a network (1602) for inverting the audio signals received by a first amplifier input channel (1600). The inverted signals are thereafter processed in out-of-phase relationship to the signals in the second amplifier input channel (1500) to more efficiently utilize the power supply. In yet another embodiment, the power supply (1710) itself is constructed with a number of fault detecting circuits which sense fault conditions in either the power supply or the amplifier and shut the power off accordingly.
70 Citations
20 Claims
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1. An apparatus for amplifying an audio signal having an amplitude which varies at an audio frequency, said apparatus comprising
(a) audio amplifier means for amplifying the audio frequency amplitude variations of the audio signal to produce an output signal corresponding to the audio signal, said amplifier means including an audio signal receiving means for receiving the audio signal and a power receiving means for receiving electrical energy for producing the output signal; -
(b) power supply means for supplying power to said amplifier means, said power supply means adapted to be connected with a source of commercially available, sinusoidally varying supply voltage having a constant frequency within the audio range, a transformer having a primary winding and a secondary winding, said secondary winding being operatively connected to said power receiving means of said amplifier means, said primary winding being adapted to be connected to said source; (c) power control means to cause variable amounts of electrical energy to be transmitted to the primary winding of the transformer to induce corresponding variable electrical energy in said secondary winding, said power control means including switch means connected between said source and said primary winding for operating in a conductive state in response to a control signal for a selected portion of each cycle of said sinusoidally varying supply voltage to cause said selected portion of said sinusoidally varying supply voltage to be applied across said primary winding only when said switch means is in said conductive state; and (d) control signal generating means responsive to the time varying amplitude of the audio signal to generate said control signal for said power control means to control the period of conduction of said switch means during each cycle of said sinusoidally varying supply voltage in correspondence with the time varying amplitude of the audio signal to minimize the time portion of each cycle of sinusoidally varying supply voltage during which idling currents pass through said primary winding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification