US 6,825,726 B2 · Power amplifier with multiple power supplies

Abstract

A power amplifier for receiving an input signal and providing a corresponding amplified output signal. One embodiment of the power amplifier includes a positive half circuit for supplying power to an amplifier during positive half waves of the output signal and a negative half circuit for supplying power to the amplifier during negative half waves of the output signal. Each half circuit has a main power supply, which is typically a switching regulator, and which supplies a first power signal to the amplifier. The slew rate of this first power signal is intentionally limited to control EMI emissions. Each half circuit also has a transient power supply which may be selectively engaged to provide a second power signal to the amplifier when the first power signal is insufficient to power the amplifier. Each half circuit may also include a low voltage power supply which provides a third power signal to the amplifier, allowing the main power supply to be disabled when a low power level is required, further reducing EMI emissions. Each half circuit has a control circuit which regulates the power output from the main and transient power supplies. The control circuit may provide a pulse width modulated control signal or a pulse density modulated control signal to control the switching regulator. If a pulse density control signal is provided, the switching regulator may be a resonant switching regulator. The power amplifier may be modified for use with a bridge amplifier, with multiple channels and may incorporate an overload detection circuit. In another embodiment of power amplifier the transient power supply is replaced with a transient control circuit that, when the first power supply is insufficient to power the amplifier, temporarily forces the first power supply to a 100% duty cycle, and then for a longer period, increases the duty cycle from its normal level to allow the first power supply to adequately power the amplifier more quickly.

Claims96

Dependent claims

A power amplifier for receiving a first input signal at a first input terminal and for producing a first output signal at a first output terminal, said first output signal corresponding to said first input signal, a first signal amplifier being coupled to the first input terminal to receive the first input signal and coupled to the first output terminal to provide the first output signal, the first signal amplifier having a first power terminal for receiving a total power signal and said power amplifier having a first power supply circuit comprising:

(a) a first input signal compensation block coupled to the first input terminal to receive the first input signal and to provide a compensated input signal corresponding to the first input signal, wherein the compensated input signal defines a target power level;
(b) a power signal compensation block for receiving the total power signal and for providing a compensated power signal corresponding to the total power signal;
(c) a summer coupled to the first input signal compensation block and to the power signal compensation block for providing an error signal corresponding to a difference between the target power level and a power level of the total power signal;
(d) a control circuit coupled to the summer for receiving the error signal and for providing a first control signal and a second control signal in response to the error signal, wherein the first control signal corresponds to a target main power signal level and the second control signal corresponds to a target transient power signal level;
(e) a transient detect block coupled to the first input signal compensation block for providing a transient signal to identify a transient condition when a rate of change in a slew rate of the compensated input signal exceeds a selected transient threshold;
(f) a main power supply for providing a main power signal at the first power terminal in response to the first control signal;
and
(g) a selectively engageable transient power supply for providing a transient power signal at the first power terminal in response to the second control signal and the transient signal, wherein the transient power supply is engaged when the transient signal indicates that a transient condition exists;
wherein the control circuit provides the first and second control signals such that the target main power signal level is equal to or higher than the target transient power signal level and wherein the magnitude of the total power signal is generally equal to the higher of the magnitude of the main power signal or the magnitude of the transient power signal.

6 more elements

(a) a first input signal compensation block coupled to the first input terminal to receive the first input signal and to provide a compensated input signal corresponding to the first input signal, wherein the compensated input signal defines a target power level;
(b) a power signal compensation block for receiving the total power signal and for providing a compensated power signal corresponding to the total power signal;
(c) a summer coupled to the first input signal compensation block and to the power signal compensation block for providing an error signal corresponding to a difference between the target power level and the power level of the total power signal;
(d) a transient detect block coupled to the first input signal compensation block for providing a transient signal to identify a transient condition when a rate of change in a slew rate of the compensated input signal exceeds a selected transient threshold;
(e) a first transient control circuit coupled to the transient detect block for providing first and second digital transient control signals, wherein the first digital transient control signal indicates the occurrence of a transient condition for a first time period in response to the transient signal and wherein the second digital transient control signal indicates the occurrence of a transient condition for a second time period in response to the transient signal, and wherein the second time period is longer than the first time period;
(f) a control circuit coupled to the summer for receiving an amplified error signal for providing a first control signal in response to the amplified error signal;
(g) a signal combining block for combining the first control signal and the first transient control signal to provide a main power supply control signal;
(h) a selectively engageable second transient control circuit coupled to the first transient control circuit for receiving the second digital transient control signal and for temporarily increasing the magnitude of the error signal, wherein the second transient control circuit is engaged and disengaged in response to the second digital transient control signal, the second transient control circuit including a feedback amplifier coupled between the summer and the control circuit to provide the amplified error signal, the feedback amplifier being operative at all times;
and
(i) a main power supply for providing a main power signal at the first power terminal in response to the main power supply control signal;
wherein the total power signal corresponds to the main power signal.

8 more elements

(a) a first input signal compensation block coupled to the first input terminal to receive the first input signal and to provide a compensated input signal corresponding to the first input signal, wherein the compensated input signal defines a target power level;
(b) a main power signal compensation block for receiving a main power signal and for providing a compensated main power signal corresponding to the main power signal;
(c) a first summer coupled to the first input signal compensation block and to the main power signal compensation block for providing a first error signal corresponding to a difference between the target power level and a power level of the main power signal;
(d) a first control circuit coupled to the first summer for receiving the first error signal and for providing a first control signal in response to the first error signal, wherein the first control signal corresponds to a target main power signal level;
(e) a total power signal compensation block for receiving the total power signal and for providing a compensated total power signal corresponding to the total power signal;
(f) a second summer coupled to the first input signal compensation block and to the total power signal compensation block for providing the second error signal corresponding to a difference between the target power level and a power level of the total power signal;
(g) a second control circuit coupled to the second summer for receiving the second error signal and for providing a second control signal in response to the second error signal, wherein the second control signal corresponds to a target transient power signal level;
(h) a transient detect block coupled to the first input signal compensation block for providing a transient signal to identify a transient condition when a rate of change in a slew rate of the compensated input signal exceeds a selected transient threshold;
(i) a main power supply for providing a main power signal at the first power terminal in response to the first control signal;
and
(j) a selectively engageable transient power supply for providing a transient power signal at the first power terminal in response to the second control signal and the transient signal, wherein the transient power supply is engaged when the transient signal indicates that a transient condition exists;
wherein the magnitude of the total power signal is generally equal to the higher of the magnitude of the main power signal or the magnitude of the transient power signal.

9 more elements

Dependencies are inferred from the claim text.

Power amplifier with multiple power supplies

Life of this patent

Power amplifier with multiple power supplies

Life of this patent

Abstract

Claims96