According to certain aspects, a predictive tracking scheme is provided for sampling inductor currents in a digital PWM controller used for high-bandwidth voltage regulation. In one or more embodiments, the predicted current derived from the PWM waveform is fed forward to the current sense ADC in order to reduce the required conversion range. These and other embodiments only need to convert a few of the LSB of the ADC in order to correct the largest error expected in the synthesizer.

An amplifier system having first and second interleaved half bridge stages and a coupled inductor. The coupled inductor has a primary winding and a secondary winding, a first end of the primary winding is coupled to the first half bridge stage at a first node, a second end of the primary winding is coupled to the load, a first end of the secondary winding is coupled to the load, a second end of the secondary winding is coupled to the second half bridge stage at a second node. An inductor circuit is coupled between the first and second half bridge stages and a first end of a load circuit.

Various embodiments of the present technology comprise a method and apparatus for a dual mode operational amplifier. According to various embodiments, the operational amplifier functions as both a fully-differential amplifier and a single-ended amplifier. The operational amplifier may comprise additional transistors that function as switches, which can be selectively operated according to a desired mode.

A method and system for controlling the switching power supply in a car audio system. The system includes a circuit that detects when the signal voltage is approaching the power supply voltage rails, that is, circuit anticipates the conditions that cause “clipping” of the signal. In response to detecting the pre-clipping condition, the circuit boosts the power supply. Additionally, the inventive system includes a holding circuit for sustaining the boosted power supply for a predetermined period of time. Thus, the power is boosted as needed and remains on for a period of time thereby preventing frequent, repetitive activation of the power supply.

A method and system for controlling the switching power supply in a car audio system. The system includes a circuit that detects when the signal voltage is approaching the power supply voltage rails, that is, circuit anticipates the conditions that cause “clipping” of the signal. In response to detecting the pre-clipping condition, the circuit boosts the power supply. Additionally, the inventive system includes a holding circuit for sustaining the boosted power supply for a predetermined period of time. Thus, the power is boosted as needed and remains on for a period of time thereby preventing frequent, repetitive activation of the power supply.

A pulse width modulation (PWM) digital-to-analog conversion circuit includes switches 102, 104, 114, 116 controlled by a first PWM signal, and switches 106, 108, 110, 112 controlled by a second PWM signal. A first operational amplifier (op-amp) includes a first input coupled to an output of a filter, and a second input coupled to an output of the first op-amp. During a first time period, an output of a second op-amp is coupled to an input of the filter via switches 102 and 104, and an output of a third op-amp is coupled to the output of the first op-amp via switches 114 and 116. During a second time period, the output of the second op-amp is coupled to the output of the first op-amp via switches 106 and 108, and an output of the third op-amp is coupled to the input of the filter via switches 110 and 112.

A driving circuit generating a driving signal, includes a modulator generating a modulated signal by performing pulse modulation on a signal specifying a waveform of the driving signal, an amplifier generating an amplified signal by amplifying the modulated signal, and a smoothing section generating the driving signal by smoothing the amplified signal. The amplifier includes first and second transistors coupled in series between a voltage line to which a voltage which is higher than a ground voltage is supplied and a grounding conductor to which the ground voltage is supplied, and a third transistor having a drain electrode coupled to a gate electrode of the second transistor and a source electrode coupled to the grounding conductor. The first and second transistors are exclusively set to an On state in accordance with the modulated signal, and the amplified signal is output from a node which couples the first and second transistors.

A driving circuit generating a driving signal, includes a modulator generating a modulated signal by performing pulse modulation on a signal specifying a waveform of the driving signal, an amplifier generating an amplified signal by amplifying the modulated signal, and a smoothing section generating the driving signal by smoothing the amplified signal. The amplifier includes first and second transistors coupled in series between a voltage line to which a voltage which is higher than a ground voltage is supplied and a grounding conductor to which the ground voltage is supplied, and a third transistor having a drain electrode coupled to a gate electrode of the second transistor and a source electrode coupled to the grounding conductor. The first and second transistors are exclusively set to an On state in accordance with the modulated signal, and the amplified signal is output from a node which couples the first and second transistors.

An apparatus measures a speaker impedance. A DAC converts a known digital input signal to an audio frequency first analog voltage signal. Resistors with known resistance attenuate the first analog voltage signal to generate a current. The known resistance effectively determines the current because the known resistance is high relative to the speaker impedance. The current is sourced into the speaker to generate a second analog voltage signal. The known resistance is sufficiently high to cause the second analog voltage signal to be inaudible as transduced by the speaker. An amplifier amplifies the second analog voltage signal with a known gain to generate a third analog voltage signal. An ADC converts the third analog voltage signal to a digital output signal. A processing element calculates the impedance of the speaker proportional to the digital output signal based on the known digital input signal, the known resistance, and the known gain.

A negative feedback system architecture and a loop filter thereof are provided. The negative feedback system architecture includes a loop filter, a pulse width modulation circuit, and a driver. The loop filter includes a three-stage series integrator for receiving a signal and outputting the filtered signal. The loop filter has three in-bandwidth poles and at least two in-bandwidth zeros. The pulse width modulation circuit is electrically connected to the loop filter for receiving the filtered signal and modulating it into a pulse width modulation signal to output. The driver is electrically connected to the pulse width modulation circuit and the loop filter for receiving the pulse width modulation signal to generate an output signal to drive a load device, and the output signal is fed back to the loop filter.