An apparatus for controlling a pulse width modulation (PWM) amplifier is disclosed. In one aspect, the apparatus includes a delay circuit configured to delay an input signal and provide the delayed input signal to the PWM amplifier. The apparatus also includes a controller configured to generate and provide a supply voltage to the PWM amplifier based at least in part on the input signal such that the PWM amplifier generates an output signal based at least partially on the delayed input signal and the supply voltage.

A quaternary/ternary modulation selecting circuit of an audio amplifier includes a quaternary signal generating circuit, for receiving complementary analog input signals to generate complementary quaternary signals; and a ternary signal generating circuit for generating a ternary signal according to the complementary quaternary signals, wherein the ternary signal includes a positive ternary wave and a negative ternary wave; wherein when a difference in amplitude between the complementary analog input signals is within a predetermined range of zero amplitude, a signal pattern of the positive ternary wave generated from the ternary signal generating circuit is identical to a signal pattern of the negative ternary wave generated from the ternary signal generating circuit.

A quaternary/ternary modulation selecting method of an audio amplifier includes: generating a ternary signal and a quaternary signal; generating a plurality of pulses with limited duty cycles; and selecting one of the quaternary signal, the ternary signal and the plurality of pulses for an output stage of the audio amplifier.

A buck-boost DC-DC converter, which includes converter control circuitry, converter switching circuitry, and a first inductive element, is disclosed. The converter control circuitry provides a buck mode timing signal and a boost mode timing signal. The converter switching circuitry provides a switching output signal. During a buck mode of the buck-boost DC-DC converter, when a buck pulse-width of the switching output signal is less than a buck pulse-width threshold, the buck pulse-width is limited based on both the buck mode timing signal and the boost mode timing signal. During a boost mode of the buck-boost DC-DC converter, when a boost pulse-width of the switching output signal is less than a boost pulse-width threshold, the boost pulse-width is limited based on both the buck mode timing signal and the boost mode timing signal. The first inductive element receives and filters the switching output signal to provide a converter output signal.

A switching amplifying method or a switching amplifier for obtaining one or more than one linearly amplified replicas of an input signal, is highly efficient, and does not have the disadvantage of dead time problem related to the class D amplifiers. Said switching amplifying method comprises the steps of: receiving the input signal; pulse modulating the input signal for generating a pulse modulated signal; switching a pulsed current from a direct current (DC) voltage according to the pulse modulated signal; conducting said pulsed current positively or negatively to a filter according to the polarity of the input signal; filtering said pulsed current positively or negatively conducted to the filter for outputting an output signal by the filter.

An apparatus includes a first power stage circuit having a first output and a power terminal, and a second power stage circuit having a second output and the power terminal. The apparatus further includes a control circuit having a control input, a first control output, and a second control output. In an example, the control input is coupled to the power terminal, the first control output is coupled to the first output, and the second control output is coupled to the second output. In an example, the control circuit is configured to, responsive to a first voltage at the power terminal being below a threshold voltage, set the first and second outputs to a second voltage.

An apparatus includes a first power stage circuit having a first output and a power terminal, and a second power stage circuit having a second output and the power terminal. The apparatus further includes a control circuit having a control input, a first control output, and a second control output. In an example, the control input is coupled to the power terminal, the first control output is coupled to the first output, and the second control output is coupled to the second output. In an example, the control circuit is configured to, responsive to a first voltage at the power terminal being below a threshold voltage, set the first and second outputs to a second voltage.

The present disclosure relates to a class-D audio amplifier. When the system is powered on, an auxiliary power amplifier and an auxiliary feedback circuit constitute an auxiliary close loop so that a control loop is established in advance. The auxiliary close loop is disconnected after various circuit modules reach their steady operation points, and the system operates at a normal state. A soft start circuit is provided for suppressing noise which occurs when the system is powered on. Thus, the class-D audio amplifier suppresses POP noise at an output terminal when the system is powered on.

The present invention relates to a class D audio amplifier comprising a pulse width modulator, an adjustable loop filter and a feedback loop. The pulse width modulator generates a first set of pulse width modulated control signals at an adjustable modulation frequency for respective switch control terminals of a first output driver. A controller of the class D audio amplifier is configured to control frequency response characteristics of the adjustable loop filter based on a frequency setting of the adjustable modulation frequency.

The amplifier according to the present invention serves to amplify an input signal to an output signal and includes a signal path and a negative feedback connection. The signal path includes a modulator which is suitable for receiving the input signal and for generating a switching signal in response to the received input signal. The signal path further includes a switched output stage, which is connected to a supply voltage, wherein the switched output stage contains a switch that is switched according to the switching signal generated by the modulator, wherein the switched output stage generates an output signal the amplitude of which depends on the supply voltage.