Abstract: Embodiments of the present invention provide methods and devices for controlling a command signal applied to a load. In embodiments of the invention, current through and voltage across a load are determined and the values of both are used to generate a hybrid control signal. For example, in some embodiments the hybrid control signal is generated by taking a weighted summation of the current and voltage control signals. In other embodiments, a percentage of the difference between the current and voltage control signals is added to one of the current or voltage control signals to generate the hybrid control signal. In one embodiment, a potentiometer is used to generate the hybrid control signal.

Abstract: A system and method are directed to measuring incoming transition widths by counting asynchronous clock pulses, deriving a reference shortest validated width, and using the shortest validated width for comparison in discriminating further incoming pulse widths.

Abstract: A switching amplifier includes first and second output terminals that may be connected to a load. A pulse-width modulator receiving an input signal to obtain respective positive and negative values of the input signal. The modulator is connected to first and second switching circuits. The first switching circuit applies a plurality of pulses to the first output terminal that, in response to the positive samples, have a constant frequency and are pulse-width modulated, and, in response to the negative samples, have a varying frequency and a constant width. Similarly, the second switching circuit applies a plurality of pulses to the second output terminal that, in response to the negative samples, have a constant frequency and are pulse-width modulated, and, in response to the positive samples, have a varying frequency and a constant width. The varying phase of the constant width pulses disperses RF interference across a wider spectrum.

Abstract: A circuit configuration and a method enables less-expensive bipolar switching devices to be employed in high-accuracy class D amplifiers. A constant-bias current is provided between the switching devices of a class D amplifier, and, through feedback or appropriate alternative implementation, the output levels of the class D amplifier achieve deterministic voltage levels regardless of current.

Abstract: A proximity detector on an audio device to limits the output level when a person's head is detected nearby. Although other detection schemes are anticipated, such a proximity detector may rely upon optical, acoustic, or radio-frequency energy.

Abstract: An open-loop switching amplifier achieves synchronous operation using a ring oscillator based upon a tapped delay line. A counter is clocked from the ring oscillator, periodically comparing incoming more significant data to the value of the counter to form a pulsewidth modulated output waveform. Modulating the effective width of the output waveform in incremental delay line taps is equivalent to incoming less significant data. This technique then effects time-period summation of coarse and fine resolution clocked data.

Abstract: A method of synchronizing static or dynamic dissimilar output sampling rates of multiple outputs of an integrated switching amplifier uses the step of synchronizing dissimilar static or dynamic sampling rates of multiple outputs to yield improved sonic quality, higher efficiency, lower EMI or other benefits. According to the preferred embodiment, the synchronizing is carried out with respect to pulse leading edges.

Abstract: Apparatus and methods for driving multiple output stages with a single switching amplification modulator reduce system cost and complexity. The technique also addresses applications wherein one or more of several output stages of potentially differing output powers are desired at one time. That is, the switching drivers and loads can be the same or different.

Abstract: Feedback for self-calibration of any parameter in an analog and/or digital system is described wherein a system quality factor can be represented by a voltage or current differential. The preferred embodiment is operative to alternately supply two or more optimally equivalent currents or voltages from such a system, detect amplitude and/or phase feedback of resultant output signal at the frequency of the alternation, and use feedback to modify a calibration value, voltage, or current so as to minimize or maximize the feedback, thus effecting self-calibration of the system. Such a method and attendant apparatus enables system self-calibration without need of any high-precision or high-cost components.

Abstract: Centering pulses within the output sample period corrects for instantaneous phase errors in multi-reference switching amplifiers. In the preferred embodiment, the pulses are ordered by the relative magnitude of each switched reference.

Abstract: A method and apparatus are disclosed for inferring amplifier load current from an internal control voltage governing a reference voltage in a multi-reference amplifier. Multi-reference amplifiers typically use internally-regulated references for application to the output stage. In that the output devices of these regulators exhibit limited gain or transconductance, internal voltage variances can be observed as a function of reference load current. This invention solves such problem at negligible additional cost.

Abstract: A method and attendant circuitry reduces the number of regulatory and switching devices in a multi-reference switching amplifier. In the preferred embodiment, multiple independently-modulated effective references are summed at a load through use of both linear and switched control of switching devices.

Abstract: An open-loop switching amplifier achieves synchronous operation using a ring oscillator based upon a tapped delay line. A counter is clocked from the ring oscillator, periodically comparing incoming more significant data to the value of the counter to form a pulsewidth modulated output waveform. Modulating the effective width of the output waveform in incremental delay line taps is equivalent to incoming less significant data. This technique then effects time-period summation of coarse and fine resolution clocked data.

Abstract: Apparatus and methods greatly improve AC and, optionally, DC power supply rejection in a switching amplifier. The method broadly includes the steps of modulating the amplifier output with a compensatory signal necessary to maintain a minimum difference between an otherwise unmodulated ancillary reference switching amplifier and a static or dynamic reference.

Abstract: A method and apparatus for detecting output current in switching power supplies forgoes the need for any resistor or other components in series with the load. A method according to the invention includes the steps of inferring the peak current through the inductor as a function of input voltage and inductor charge time, and deriving the current available to the load based upon the flyback voltage during discharge of the inductor. Although a disclosed example is based upon a buck/boost topology, other converter topologies are anticipated. In terms of apparatus, in a switching power supply of the type wherein a switching device is used to charge an inductor that discharges to a load, the invention provides devices arranged for detecting output current without the need for a resistor or other component in series with the load.

Abstract: A method and circuitry are disclosed that provide for linear operation of a flyback converter through zero output. Broadly, the preferred embodiment enforces a minimum control pulse width thereby isolating energy derived thereby from the eventual load, and dissipating the energy from the minimum control pulse width. The net effect is linear operation inclusive of zero output.

Abstract: An integrated speaker or microphone derives its power from an incoming signal, thereby minimizing or eliminating the need for an external amplifier or power supply. A system according to the invention includes an audio transducer, an input for receiving a digital audio signal, an amplifier for amplifying the digital audio signal to or from the audio transducer, and a rectifier for rectifying the digital audio signal for use in powering the amplifier. A filter may be included for filtering the output of the rectifier. In the preferred embodiment, the digital audio signal uses a non-return-to-zero (NRZ) encoding scheme. When the transducer is a microphone, it is connected to an analog-to-digital (A/D) converter, also powered by the rectified digital audio signal.

Abstract: A circuit configuration and a method enables less-expensive bipolar switching devices to be employed in high-accuracy class D amplifiers. A constant-bias current is provided between the switching devices of a class D amplifier, and, through feedback or appropriate alternative implementation, the output levels of the class D amplifier achieve deterministic voltage levels regardless of current.

Abstract: A method of modulating the sampling period of a sampled system with a factor N, and correcting the data stream of the sampling system with the same factor N, thus minimizing distortion artifacts induced by sample frequency modulation. At least a one-period delay from receipt of a new data stream value is used to avoid heterodyning with the incoming stream.

Abstract: A long-term power storage device associated with an amplifier is trickle-charged by a relatively low-power source. In that amplification has a very large peak-to-average power ratio, high output levels can be obtained from a low average input power. Furthermore, since most amplification use is not constant, refractory periods exist wherein battery recharging can occur.