A noise reduction circuit for a DC power supply in which the input of a high pass filter is coupled to the output circuit of the supply so as to receive a noise signal, the output of the high pass filter is coupled to the primary winding of a transformer via an amplifier, and the secondary winding of the transformer is coupled to the output circuit of the supply so as to reduce the noise therein.
A method and apparatus reduces an output ripple signal of a power supply (200) for supplying a DC voltage and current to a load. One of the output ripple signal and an intermediate ripple signal is sensed to produce a control signal at a ripple sensing element (206), and a rectangular pulse carrier signal is generated by a pulse width modulator (302), the signal having a duty cycle modulated with the control signal to produce a pulse width modulated (PWM) signal carrying ripple signal energy. The rectangular pulse carrier signal operates at a frequency substantially higher than the control signal. The PWM signal is coupled into a portion of the power supply through a transformer (202). The transformer is arranged such that the PWM signal is combined with the intermediate ripple signal at an amplitude and relative phase sufficient to substantially reduce the output ripple signal.
A system is provided for attenuating tonal acoustic noise associated with a single positive displacement compressor, or multiple positive displacement compressors proximately located from each other. A controller selectably controls the rotational speed and the frequency of operation of each of the compressors. The controller controls the rotational speed of the compressors about a predetermined rotational speed, in a random manner, within the pre-selected speed band to reduce the magnitude of the central tonal acoustic frequency of the pressure pulsations and disperse the sound power over a wider acoustic bandwidth.
An apparatus for electrically stimulating a smart material includes a controllable power source for charging the smart material and/or switching circuitry for discharging the smart material. The controllable power source includes a regulated DC to DC converter having controllable drive circuitry associated therewith. The drive circuitry can be self-oscillating through associated feedback means. The switching circuitry can be responsive to one or more control signals.
An apparatus using electrically-stimulated smart material requires a power source to stimulate the material. This power source has three main functions, (1) to apply a known voltage potential across the smart material, (2) to convert from the control voltage to a level suitable for the smart material, and (3) to regulate the voltage based on a control input. The power source is a DC to DC converter with special properties achieved by supplying a variable stimulating voltage or actively discharging the actuator. The circuit also provides a dead band, or hysteresis, between the charge point and discharge point. When this circuit is applied with a proportional, mechanically-leveraged smart material actuator, a general-purpose industrial actuator becomes a cost-effective solution.
An apparatus for charging a battery includes a first electrical connection adapted to connect to a positive terminal of the battery and a second electrical connector adapted to connect to a negative terminal of the battery. An electrical charging source couples to the first and second electrical connectors to charge the battery. Voltage measurement circuitry couples to the first and second electrical connectors and responsively provides a voltage output related to voltage across the battery. Current measurement circuitry also couples to the first and second electrical connectors and responsively provides a current output related to electrical current through the battery. State of charge measurement circuitry responsively provides a state of charge output as a function of the voltage output and the current output.
