Abstract: A gradient amplifier for use in a MRI system can be located in the scan room. The gradient amplifier includes pair of rails connected to a gradient power supply. The gradient amplifier also includes a H-bridge of switches which includes a first high side switch and a first low side switch connected in series between the pair of rails, and a second high side switch and a second low side switch connected in series between the pair of rails. The gradient amplifier further includes a first high side driver circuit, a first low side driver circuit, a second high side driver circuit, and a second low side driver circuit, each configured to drive the corresponding switch in the H-bridge. A common power source supplies power to all driver circuits, wherein power is supplied to the high side driver circuits through bootstrap circuits.

Abstract: A method of handling a peak power requirement of a medical imaging device 106 is presented. The method includes determining, using at least one controlling unit 107, 108, a first voltage corresponding to a direct current (DC) link 116, a second voltage corresponding to one or more energy storage devices 110, or a combination thereof, where a power source 102 is coupled to a plurality of loads via the DC link, and the energy storage devices are coupled to the DC link. Further, the method includes comparing, using the at least one controlling unit, the first voltage with a first reference value and the second voltage with a second reference value and regulating, using at least one controlling unit, at least one of the first voltage and the second voltage based on the comparison, to handle the peak power requirement of the medical imaging device.

Abstract: A method is used for operating a switching amplifier, the switching amplifier includes a plurality of cascade elements. The method includes: coupling the cascade elements in series between two terminals of a load; providing two leg circuits each comprised of switches in each of the cascade elements; and controlling all of the switches comprised in the switching amplifier using space vector modulation (SVM), such that a change of a common mode (CM) voltage generated by the switching amplifier is in a predetermined range.

Abstract: A gradient amplifier for use in a MRI system can be located in the scan room. The gradient amplifier includes pair of rails connected to a gradient power supply. The gradient amplifier also includes a H-bridge of switches which includes a first high side switch and a first low side switch connected in series between the pair of rails, and a second high side switch and a second low side switch connected in series between the pair of rails. The gradient amplifier further includes a first high side driver circuit, a first low side driver circuit, a second high side driver circuit, and a second low side driver circuit, each configured to drive the corresponding switch in the H-bridge. A common power source supplies power to all driver circuits, wherein power is supplied to the high side driver circuits through bootstrap circuits.

Abstract: There is set forth herein an ultrasound signal generating circuit having a control circuit which can include a control circuit having a control signal generating circuit; a low power signal driver circuit for providing a low power ultrasound signal; a high power signal driver circuit for providing a high power ultrasound signal; and a radiofrequency switch configured to transmit the low power ultrasound signal and the high power ultrasound signal to the ultrasound probe, wherein the radiofrequency switch isolates the low power signal driver circuit from the high power signal driver circuit; wherein the ultrasound signal generating circuit is configured so that the radiofrequency switch transmits an output low power ultrasound signal output by the low power signal driver circuit or an output high power ultrasound signal output by the high power signal driver circuit based on an output of the control signal generating circuit.

Abstract: A method is used for operating a switching amplifier, the switching amplifier includes a plurality of cascade elements. The method includes: coupling the cascade elements in series between two terminals of a load; providing two leg circuits each comprised of switches in each of the cascade elements; and controlling all of the switches comprised in the switching amplifier using space vector modulation (SVM), such that a change of a common mode (CM) voltage generated by the switching amplifier is in a predetermined range.

Abstract: A method of handling a peak power requirement of a medical imaging device 106 is presented. The method includes determining, using at least one controlling unit 107, 108, a first voltage corresponding to a direct current (DC) link 116, a second voltage corresponding to one or more energy storage devices 110, or a combination thereof, where a power source 102 is coupled to a plurality of loads via the DC link, and the energy storage devices are coupled to the DC link. Further, the method includes comparing, using the at least one controlling unit, the first voltage with a first reference value and the second voltage with a second reference value and regulating, using at least one controlling unit, at least one of the first voltage and the second voltage based on the comparison, to handle the peak power requirement of the medical imaging device.

Abstract: A circuit for driving the current for inductive loads such as a electron beam deflection coil for an x-ray generator system. The circuit includes two selectable voltage levels which are provided by a high level voltage source and a low level voltage source or, alternatively, by a low level voltage source and a boosting converter. A plurality of switches for selecting the voltage source allow only one voltage source to be connected to the load at any given time, and for selecting the polarity of the current through the coil. The high level voltage source is selected when the load is charging or discharging. The low level voltage source is selected when the load is operating in a constant current mode, where a high frequency switching device uses the low level voltage source to generate a pulse width modulation waveform according to a reference current duty cycle to control the voltage across the load.

Abstract: A circuit for driving the current for inductive loads such as an electron beam deflection coil for an x-ray generator system. The circuit includes two selectable voltage levels provided by a high level and a low level source. A plurality of switches selects the voltage level and determines the polarity of the current through the coil. The high level source is selected when the load is charging or discharging. The low level source is selected when the load is operating in a constant current mode, where a high frequency switching device controls the voltage through the load by switching the low level source to generate a PWM waveform according to a reference current duty cycle. A feedback loop monitors the current through the load to adjust the duty cycle of the PWM waveform to more accurately control the current through the load.

Abstract: A gradient amplifier arrangement is described that comprises a gradient amplifier power stage. The device may be employed to provide a current to a gradient coil, as in a MRI system. The circuitry disclosed includes a series coupling of a first bridge amplifier operating at a first voltage, a second bridge amplifier operating at a second voltage, a third bridge amplifier operating at a third voltage, and a gradient amplifier control stage. The amplifiers may provide output voltages at different levels, and may be switched at different times and frequencies to provide a range of output voltage and current levels.

Abstract: The present invention provides a nano-calorimeter device operable for measuring and characterizing the thermodynamic and other physical properties of materials that are confined to essentially nano-scale dimensions. The nano-calorimeter device including a thin film membrane having a first surface and a second surface. The nano-calorimeter device also including a frame structure disposed adjacent to and in thermal contact with the first surface of the thin film membrane, the frame structure defining a plurality of hollow cells adjacent to and in thermal contact with the first surface of the thin film membrane.

Abstract: A method of operating a system having a coil includes providing a switched amplified current to the coil, and adding a second current to the switched amplified current, wherein the second current is substantially out of phase with the switched amplified current such that the coil receives current with substantially no switching frequency ripple.

Abstract: An electronic ballast which is capable of compactly powering a discharge lamp from a source of rectified, but unregulated, power having a varying DC voltage. The ballast includes a selfoscillating converter powered by the DC voltage for producing pulses at a nominal operating frequency which is determined by a resonant tank. The resonant tank converts the pulses to a sinusoidal current for powering the discharge lamp and includes an inductive impedance.in series with the lamp for providing a voltage drop which varies with the operating frequency. A feed-forward control circuit is coupled to the converter for automatically varying the operating frequency directly with variations in the DC source voltage. The voltage drop across the inductive impedance is substantially proportional to the magnitude of the DC source voltage. This enables regulation of the voltage supplied to the discharge lamp by the ballast without sensing the lamp voltage itself.

Abstract: An electronic ballast is provided which is capable of compactly powering a discharge lamp from a source of rectified, but unregulated, power having a varying DC voltage. The ballast includes a self-oscillating converter powered by the DC voltage for producing pulses at a nominal operating frequency which is determined by a resonant tank. The resonant tank converts the pulses to a sinusoidal current for powering the discharge lamp and includes an inductive impedance in series with the lamp for providing a voltage drop which varies with the operating frequency. A feed-forward control circuit is coupled to the converter for varying the operating frequency directly with variations in the DC source voltage. The voltage drop across the inductive impedance is substantially proportional to the magnitude of the DC source voltage. This enables regulation of the voltage supplied to the discharge lamp by the ballast without sensing the lamp voltage itself.

Abstract: A switching power supply is provided in two stages with the primary of the power transformer being in the first stage and the secondary in the second stage. The first stage includes an EMI filter connected to the input of a rectifier. The output of the rectifier is connected to a self oscillating, half-bridge, resonant inverter operating in open loop with the primary of the transformer to provide isolation from the power source. Feed-forward control is used to compensate for line variations, providing very small output voltage variation compared with input voltage variation. In the second stage, the secondary of the transformer provides an input to post regulator circuitry including a PWM control circuit to regulate the output current using the error signal representing the differences between the current sensed and the desired value.

Abstract: A compact circuit assembly is provided for containment within the end of a circular fluorescent lamp envelope. The circuit assembly includes a plurality of circular circuit boards arranged along the length of the envelope end and having respective peripheries contacting an inner surface of the envelope. The circuit boards are interconnected and held in spaced-apart positions by a plurality of longitudinally-extending conductors which also serve as electrical buses for making electrical connections.

Abstract: A lamp electronic ballast with a piezoelectric cooling fan. Use of ballast-driven lamps is limited in some lighting applications by thermal considerations. For example, the problem of heat removal from compact fluorescent lamps with integrated ballasts has limited their use. Similarly, the use of ballast-driven fluorescent lighting in high hat and other closed luminaire applications has been limited by thermal considerations. Thermal management of ballasts for such thermally sensitive applications is provided by a piezoelectric fan integrated with the ballast. The power to drive the fan may be obtained from the same AC line input that supplies the ballast, or from an AC ripple voltage present at the output of a rectifier in the ballast, or from the output of the ballast to the lamp, or from any suitable circuit location in the ballast. The fan maybe a membrane-type spot-cooler comprising a thin membrane carried by a frame mounted adjacent a hot spot.