A method of monitoring electrical loads is disclosed. In an embodiment the method includes generating a first voltage signal and a second voltage signal, the second voltage signal in quadrature to the first voltage signal, injecting one of the first voltage signal or the second voltage signal into a signal propagation path towards an electrical load, sensing a current signal flowing through the electrical load as a result of the one of the first voltage signal or the second voltage signal injected into the signal propagation path and processing the first voltage signal, the second voltage signal and the sensed current signal.

This application provides a wireless charger and a control method. The wireless charger includes a class-E power amplifier and a tunable impedance circuit that is connected to an output end of the class-E power amplifier. The class-E power amplifier includes a switching transistor and a tunable capacitance circuit that is parallelly connected to the switching transistor. The wireless charger further includes a control unit, configured to obtain a constraint condition of the class-E power amplifier; determine N1 target equivalent load impedances of the class-E power amplifier based on the constraint condition; and adjust a capacitance value of the tunable capacitance circuit in the class-E power amplifier, and adjust an impedance value of the tunable impedance circuit, to enable an equivalent load impedance of the class-E power amplifier to match one of the N1 target equivalent load impedances.

Base station antennas utilize RF transmitters and receivers, which operate with enhanced bias control to achieve very high speed switching during TDD operation. A radio frequency communication circuit for TDD includes a transmit/receive amplifier (e.g., MMIC) having first and second input terminals, which are responsive to a bias control voltage and radio frequency input signal. A bias control circuit is provided, which is electrically coupled to the first input terminal and a current receiving terminal of the transmit/receive amplifier. The bias control circuit includes a closed-loop feedback path between the current receiving terminal and the first input terminal, which is configured to regulate a magnitude of the bias control voltage with high precision to thereby achieve a substantially constant quiescent bias current at the current receiving terminal when the transmit/receive amplifier is enabled.

Base station antennas utilize RF transmitters and receivers, which operate with enhanced bias control to achieve very high speed switching during TDD operation. A radio frequency communication circuit for TDD includes a transmit/receive amplifier (e.g., MMIC) having first and second input terminals, which are responsive to a bias control voltage and radio frequency input signal. A bias control circuit is provided, which is electrically coupled to the first input terminal and a current receiving terminal of the transmit/receive amplifier. The bias control circuit includes a closed-loop feedback path between the current receiving terminal and the first input terminal, which is configured to regulate a magnitude of the bias control voltage with high precision to thereby achieve a substantially constant quiescent bias current at the current receiving terminal when the transmit/receive amplifier is enabled.

Power systems and circuitry for generation of gradient magnetic fields in magnetic resonance imaging (MRI) systems are discussed herein. Embodiments may include the use of multiple gradient amplifiers that share a high-frequency power distribution unit, that may perform power distribution and power supply roles. The high-frequency power distribution unit may allow the use of a single power supply to drive multiple gradient amplifiers via a shared power bus. The gradient amplifiers may make use of modern semiconductor materials that provide high-frequency, high voltage performance, and may be implemented using single semiconductor bridges.

A PWM modulator has a quantizer that generates a PWM output signal to speaker driver. When a first voltage swing range is supplied to the speaker driver, the quantizer analog gain is controlled to be a first gain value. When a second PWM drive voltage swing range is supplied to the speaker driver, the analog gain is controlled to be a second gain value. The first and second gain values of the analog gain of the quantizer cause the combined gain of the quantizer and driver to be approximately equal in the two modes. The quantizer has at least two gain-affecting measurable non-ideal characteristics. The quantizer is adjustable using measured first and second values to correct for first and second of the at least two non-ideal characteristics. The gain of the quantizer is calibratable while the quantizer is adjusted using the measured first and second measured values.

A PWM modulator has a quantizer that generates a PWM output signal to speaker driver. When a first voltage swing range is supplied to the speaker driver, the quantizer analog gain is controlled to be a first gain value. When a second PWM drive voltage swing range is supplied to the speaker driver, the analog gain is controlled to be a second gain value. The first and second gain values of the analog gain of the quantizer cause the combined gain of the quantizer and driver to be approximately equal in the two modes. The quantizer has at least two gain-affecting measurable non-ideal characteristics. The quantizer is adjustable using measured first and second values to correct for first and second of the at least two non-ideal characteristics. The gain of the quantizer is calibratable while the quantizer is adjusted using the measured first and second measured values.

A power amplifier circuit includes a first transistor, wherein a radio frequency signal is inputted to a base or gate of the first transistor; a second transistor having an emitter connected to a collector or drain of the first transistor, wherein a first voltage is supplied to a collector of the second transistor, and a first amplified signal obtained by amplifying the radio frequency signal is outputted from the collector of the second transistor; and a third transistor configured to supply a bias voltage to a base of the second transistor. A second voltage is supplied to a collector or drain of the third transistor, a third voltage corresponding to the first voltage is supplied to a base or gate of the third transistor, and the bias voltage, which corresponds to the third voltage, is supplied from an emitter or source of the third transistor.

A class-E power oscillator (PO) is disclosed. The class-E PO includes a first inductor, a switch, a first capacitor, a resonant circuit, and a feedback network. The first inductor is coupled in series to a first power supply. The switch is connected between the first inductor and a primary common node. The first capacitor is connected between the first inductor and the primary common node. The resonant circuit includes a second inductor, a second capacitor, and a resistor. The second inductor is connected between the first inductor and the primary common node. The second capacitor is connected between the first inductor and the primary common node, and is coupled in series to the second inductor. The resistor is connected between the first inductor and the primary common node, and is coupled in series to the second inductor. The feedback network is connected between the switch and a feedback node. The feedback node is located between the second inductor and the second capacitor. The feedback network is configured to periodically turn the switch on and off based on a resonance frequency of the resonant circuit.

A power converter produces power at a greater voltage than provided by a power source, while drawing power from the power source, wherein the power converter has a variable input current limit or a variable input power limit. One or more audio amplifiers are configured into i) drawing power from the power source bypassing the power converter and ii) drawing power from the power converter, according to audio signal amplitude, during audio playback and in accordance with an audio signal being amplified. A load of each amplifier is determined for when the amplifier is drawing power from the power source bypassing the power converter. The variable input limit of the power converter is adjusted in accordance with the determined load, during the audio playback. Other aspects are also described and claimed.