Abstract: Class D amplifiers are used for their high efficiency, but they have some undesirable characteristics, one of these being the residual switching frequency ripple. Embodiments of the present invention comprise methods and apparatuses for reducing the switching frequency ripple using a technique known herein as ripple steering. A secondary output is added to the amplifier for the purpose of steering the switching ripple away from the main output thus substantially relieving the main output from a major artifact of prior art Class D amplifiers.

Abstract: Class D amplifiers are used for their high efficiency, but they have some undesirable characteristics that limit their useable bandwidth, one of these being the residual switching frequency ripple. Embodiments of the present invention comprise methods and apparatuses for reducing the switching frequency ripple using a technique known herein as ripple steering. The zero ripple class D amplifier is used in a hybrid system comprising a linear amplifier. The hybrid Class D amplifier is modified for extended bandwidth and lowered distortion by the addition of a linear current source feeding output capacitor. The low frequency bandwidth limit on the linear current source is matched to the high frequency bandwidth limit on the Class D current source, resulting in a composite linear/switching current source with bandwidth extended to the high frequency bandwidth limit of the linear current source.

Abstract: A heat dissipation system for an audio amplifier is presented, including a housing having a plurality of apertures therein; at least one completely enclosed air tunnels, each air tunnel extending between one of the apertures in the housing and another of the apertures in the housing, each air tunnel at least partially defined by a pair of opposed heat sinks mounted within the housing.

Abstract: A system and method for protecting an output transistor in an audio amplifier output stage includes a protection circuit that protects the output transistor from excessive currents and voltages, and does not interfere with the normal operation of the output transistor. The protection circuit generates an estimate of the power dissipated by the output transistor, applies this estimate to an electrical analog of the thermal time constants of the transistor to obtain an estimate of the temperature differential between junction and case, compares this differential to a limit, which is a function of transistor case temperature.

Abstract: A multicolor function indicator light system is provided for an audio amplifier or similar electronic equipment. A sensor circuit monitors operation of the equipment. An indicator light device has a plurality of different color outputs.

Abstract: A heat dissipation system for an audio amplifier is presented, including a housing having a plurality of apertures therein; at least one completely enclosed air tunnels, each air tunnel extending between one of the apertures in the housing and another of the apertures in the housing, each air tunnel at least partially defined by a pair of opposed heat sinks mounted within the housing.

Abstract: A multiple power factor audio amplifier with a power draw up to a maximum amplifier power draw flowing through at least two power flow circuits with at least one circuit including a power factor corrector electrically connected between the amplifier and input terminals. One embodiment including a power factor corrector sized to provide a first output less than the maximum amplifier power draw of the amplifier and a high output power factor bypass adapted to provide a second output to supplement the first output when the amplifier power draw exceeds the first output. Also described are methods for controlling the amplifier demand power factor including adjusting the draw of a first portion of the direct current power at a first level to improve the power factor of an input demand at the rectifier to provide a first part of the demanded amplifier power; and transferring a second portion of the direct current power without power factor correction to provide a second part of the demanded amplifier power.

Abstract: An audio power amplifier including a rail voltage detection circuit connected to a feedback generator and a rail voltage, the detection circuit is adapted to detect an overvoltage or undervoltage condition and control the feedback signal to a regulated switching power supply to adjust the rail voltage. Additional protection is provided through thermal stress detection and output fault detection to control the feedback signal and protect the audio power amplifier.

Abstract: An audio power amplifier including a rail voltage detection circuit connected to a feedback generator and a rail voltage, the detection circuit is adapted to detect an overvoltage or undervoltage condition and control the feedback signal to a regulated switching power supply to adjust the rail voltage. Additional protection is provided through thermal stress detection and output fault detection to control the feedback signal and protect the audio power amplifier.

Abstract: A multiple power factor audio amplifier with a power draw up to a maximum amplifier power draw flowing through at least two power flow circuits with at least one circuit including a power factor corrector electrically connected between the amplifier and input terminals. One embodiment including a power factor corrector sized to provide a first output less than the maximum amplifier power draw of the amplifier and a high output power factor bypass adapted to provide a second output to supplement the first output when the amplifier power draw exceeds the first output. Also described are methods for controlling the amplifier demand power factor including adjusting the draw of a first portion of the direct current power at a first level to improve the power factor of an input demand at the rectifier to provide a first part of the demanded amplifier power; and transferring a second portion of the direct current power without power factor correction to provide a second part of the demanded amplifier power.