Abstract: A half-bridge gate driver circuit including two separate floating high-side driver circuits for operating a switch circuit having a high-side switch and a low-side switch. Each of the driver circuits include input control logic which is referenced to a supply signal with a potential that becomes negative relative to the negative common terminal of the switches, thereby enhancing the operation of the switch circuit. The circuit may further include signal translation stages for translating control signals to the control logic of the driver circuits. The signal translation stages include a plurality of cascoded parasitic transistors which provide a neutralizing capacitance to minimize noise.

Abstract: An apparatus and method for reducing power loss due to switching of a switch mode power converter includes a power converter having a plurality of switch assemblies, each connected in parallel through an inductor to a common output node and a diode connected to a second common output node, and a switch controller for activating and deactivating the plurality of switch assemblies during successive switching cycles. The controller activates and deactivates each switch assembly one time during each switching cycle and activates one subset of switch assemblies before activating the remaining switch assemblies. The switch controller provides enable signals to commute the subset of switch assemblies among the plurality of switch assemblies to be activated before the remaining switch assemblies. The switch controller includes a modulator for modulating a clock signal and demand signal, and at least one delay circuit for providing a signal which is delayed in time relative to the modulated signal.

Abstract: A generalized method for balancing paralleled power converters is disclosed wherein (N) power converters, generally voltage amplifiers, are paralleled and have current sensors positioned so as to form a differencing equation for the circulating current, and use that difference current as feedback to the paralleled power converters to force the circulating current to zero. The current sensors are current transforming transducers, where (N−1) transducers are included and where the feedback from the (N−1) transducers is distributed to summing amplifiers, which according to their gain distribution, balances the power converters. The system also includes passive magnetic devices to facilitate current sharing, where the devices are generally inductors which are designed to store no magnetic energy when under balanced excitation.

Abstract: The present invention provides an active low-pass filter system including a low-pass filter circuit and at least one frequency-rejecting network coupled to the low-pass filter circuit. The frequency-rejecting network is included in a resistive forward signal flow branch of the low-pass filter. The present invention also provides a power amplifier system for driving a load. The power amplifier system includes a pulse width modulation circuit which creates ripple spectra, an error amplifier and modulator circuit, and a demodulation filter connected in series, and a feedback control loop coupled to the pulse modulation circuit and including an active low-pass filter having a feedback demodulation filter and an isolated-integrator frequency-rejecting network.

Abstract: A power converter having a remote sensing system. The power converter includes a high-pass feedback signal, a remote sensing low-pass signal, a constant-sum filter combining the high-pass feedback signal and the remote sensing low-pass signal. The constant-sum filter is at least a second order filter and generates an error signal. The constant-sum filter is a three terminal low-pass filter and an input terminal, an output terminal, and a common terminal. The input terminal receives the remote sensing low-pass signal. The common terminal receives the high-pass feedback signal. The output terminal transmits the feedback control signal.

Abstract: A generalized method for balancing paralleled power converters is disclosed wherein (N) power converters, generally voltage amplifiers, are parallel and have current sensors positioned so as to form a differencing equation for the circulating current, and use that difference current as feedback to the paralleled power converters to force the circulating current to zero. The current sensors are current transforming transducers, where (N−1) transducers are included and where the feedback from the (N−1) transducers is distributed to summing amplifiers, which according to their gain distribution, balances the power converters. The system also includes passive magnetic devices to facilitate current sharing, where the devices are generally inductors which are designed to store no magnetic energy when under balanced excitation.

Abstract: A closed loop Hall effect current transformer in which the Hall effect device has an input resistance which varies with its operating temperature. The Hall effect device is driven by a fixed voltage passing through a current limiting a resistor with variations in voltage across the resistor being indicative of the operating temperature of the device. Further, variations in the input resistance of the device caused by variations in its operating temperature is corrected for by mixing a correcting signal with the outputted signal from the device, said correcting signal being derived from a voltage signal taken across the resistor at the driving input of the device.

Abstract: A dual mode gradient coil system in which amplifiers powered by a single signal source are connected by a switch to a plurality of coils. The switch selectively serves to place the coils in series with said amplifiers placed in parallel for a high change in magnetic field per unit distance or, alternatively, to allow each coil to be driven by a separate amplifier for a high change in magnetic field per unit time.

Abstract: A power supply for supplying a DC voltage from an AC supply voltage provided by an AC voltage source to an amplifier includes a plurality of input lines coupled to the AC voltage source a rectifier coupled to the input lines to provide an unregulated positive DC voltage component and an unregulated negative DC voltage component, first and second regulators coupled to the rectifier and generating controlled positive and negative DC voltage components, and a plurality of output lines coupled to the regulators. The regulators augment the unregulated positive and negative DC voltage components with the controlled positive and negative DC voltage components to create positive and negative DC voltages on the output lines.

Abstract: A power converter includes a pair of switches, each of the switches being connected between positive and negative constant DC voltage sources and a common output node which is connected to a load. A modulator opens and closes the switches in a sequence in which the electrical current controlled by the switches are in opposition to one another at the common output node, and are summed at the output node. The modulator includes a triangle wave generator and comparators which are connected to an error amplifier to provide a bearing switching voltage to the comparators. The comparators switch the control switches in response to the triangle wave generated by the triangle wave generator increasing above and decreasing below the reference levels. Underlap and overlap of the converter is controlled by varying of the DC bias level of the triangle wave.

Abstract: A power converter which includes a bridged power amplifier powered from a sole or single DC input power source through a plurality of parallel connected PWM buck converters. The converters are modulated with reference signals which operate in time alternation such that in any conversion cycle there exists a plurality of modulating wave forms which are identical except for their time delays and which are evenly spaced in time over a single conversion cycle. A feedback control amplifier compares the voltage output of the parallel connected converters through the magnitude of the amplifier's required supply voltage and drives the modulating components of the circuit to control the switching duty cycle of each of the individual PWM converters.

Abstract: This invention employs timing circuitry for each voltage source in a multilevel power supply for an amplifier to control the change in voltage outputted from the associated voltage source over time or slew rate when that voltage source is switched on or off preventing large instantaneous voltage increases at the input of the amplifier from occurring when a combination of the voltage sources supplying the amplifier is switched to a different combination upon the output voltage of the amplifier changing.

Abstract: A sixteen level power supply including four voltage sources having stepped voltage values. The voltage sources are controlled by an electronic switch assembly and may be switched into series between the positive and negative output voltage terminals. The switches are controlled by a controller circuit which monitors voltage available at each voltage source in comparison to a demand signal. The controller output a digital control bit to activate each switch.

Abstract: An amplifier selector for use with a MRI machine having stacked amplifiers. The selector includes a switch assembly carried by each amplifier and controlled by a central controller. Each switch assembly includes a motor for rotating a plurality of switch plates to various predetermined stations. The stations connect the input and output terminals of the slave amplifier to either the X, Y or Z axis of the MRI machine. A fourth station is included to define an off line condition for the amplifier.

Abstract: A sixteen level power supply including four voltage sources having stepped voltage values. The voltage sources are controlled by an electronic switch assembly and may be switched into series between the positive and negative output voltage terminals. The switches are controlled by a controller circuit which monitors voltage available at each voltage source in comparison to a demand signal. The controller output a digital control bit to activate each switch.

Abstract: A switch connected between two voltage sources and responsive to a sensing circuit. The switch includes a transistor which operates to interchange the electrical connection of the two voltage sources from parallel to series upon the sensing circuit signals the need for more voltage. The two sources are normally in parallel to increase the cost efficiency and energy efficiency of the amplifier and power supply.

Abstract: A method of fault sensing for a power amplifier having direct coupled power stages with normally mutually exclusive current flow in which the alternating current output is simultaneously sensed and, when a fault is detected, is ANDed. A power reduction to the amplifier is initiated when the ANDed output exists for a selected period of time.

Abstract: A bridge amplifier having paired high and low output stages in which a main amplifier receiving an input signal drives the high output stages and a balancing amplifier drives the low of the output stages. A junction temperature simulation circuit extends between the main amplifier and the low output stages in which the temperatures of the low output stages are sensed to produce an arresting of the main amplifier drive to the high output stages and thereby simultaneously control the balancing amplifier and its drive to the low output stages.

Abstract: A programmable signal generator which utilizes an eight bit microprocessor to generate a sixteen bit signal. Information is passed from an eight bit processor having a sixteen bit address register into one or more latches to produce a sixteen bit digital signal. The generator may be utilized in a time delay spectrometer to produce digital signals in quadrature form which are analyzed by the system microprocessor.

Abstract: A thermal protection circuit for the die of a transistor having a heat sink in which a signal proportional to the dissipative input current and a signal proportional to the dissipative applied voltage of the transistor are multiplied to produce a signal representative of the applied power to the transistor. This representative applied power signal is transformed into a simulated differential in temperature between the die of the transistor and its heat sink. Simultaneously, the temperature of the heat sink is determined and this temperature is added to the simulated differential in temperature between the die of the transistor and the heat sink to determine a sensed die temperature. A control responsive to this sensed die temperature reduces the applied power to the transistor.