Virginia Tech Intellectual Properties Inc

Other

Caterpillar Inc.

Wojciech A Tabisz

Fred C Lee

Milan M Jovanovic

James A Antone

An apparatus that drives a piezoelectric actuator in response to charging and discharging command signals is disclosed. The apparatus includes an energy source that supplies electrical energy to the piezoelectric actuator. A charging circuit includes: a charging transistor connected to the energy source to control the amount energy supplied to the piezoelectric actuator, a charging inductor connected to the charging transistor to limit the rate of change of energy supplied to the piezoelectric actuator, and a charging thyristor disposed between the charging circuit and the piezoelectric actuator. A selecting circuit receives the charging command signal and responsively biases the charging thyristor ON to connect the piezoelectric actuator to the charging circuit. A comparator determines the magnitude of voltage applied to the piezoelectric actuator. A control circuit receives the charging command signal, and responsively biases the charging transistor alternately ON and OFF to control the amount of energy supplied to the piezoelectric actuator in response to the piezoelectric actuator voltage being less than an upper desired voltage value. Finally, the selecting circuit biases the charging thyristor OFF to disconnect the piezoelectric actuator from the charging circuit in response to the piezoelectric actuator voltage being greater than or equal to the upper desired voltage value.

Apparatus for driving a piezoelectric actuator

A half-bridge zero-voltage-switched multi-resonant converter. The converter basically comprises a device for converting an input voltage signal to a DC output signal to be imposed across a load. The device includes input terminals for receiving the input signal and output terminals for imposing the DC output signal across the load. Serially connected first and second switching assemblies are connected in parallel across the input terminals. Each of the first and second switching assemblies includes a transistor switch, a diode and a capacitor all arranged in parallel. The device further includes a transformer having a primary winding and serially connected first and second secondary windings. A first rectifier in parallel with a first resonant capacitor is used to connect the first secondary winding across the output terminals. Circuitry is provided for connecting the primary winding of the transformer to the input terminals and to the serial connection between the first and second switching assemblies. In order to complete the zero-voltage-switched multi-resonant converter for off-line use, a resonant circuit is formed with the first and second resonant capacitors and the total inductance of the primary winding of the transformer.

Half-bridge zero-voltage switched multi-resonant converters

A multi-resonant-switching network that operates under switching conditions that are favorable to both the active switch and the diode that constitute the switch. In a zero-current multi-resonant switch, the resonant circuit is formed in a T-network with resonant inductors in series with the switching devices. In a zero-voltage multi-resonant switch, the resonant circuit is formed in a .pi.-network with resonant capacitors connected in parallel with the switch. In this way, the two networks are dual. During operation of a multi-resonant converter, a multi-resonant switches forms three different resonant circuits depending on whether the active switch and diode are open or closed. This results in operation of the converter with three different resonant stages in one cycle of operation. In practicing the present invention, certain rules are applied to derive a ZVS-MRC from a PWM converter. In particular, one resonant capacitor is placed in parallel with the active switch, which may be either uni-directional or bi-directional, another resonant capacitor is placed in parallel with the rectifying diode, and an inductor is inserted in the loop containing the switch and the diode. This loop can also contain voltage sources and filter or blocking capacitors. Improvement in the operation of ZVS-MRCs is obtained with synchronous rectification which is achieved by replacing rectifying diodes in a DC/DC converter with active devices, called synchronous rectifiers.

Zero-voltage-switched multi-resonant converters including the buck and

A generalized multi-resonant switch that combines current-mode and voltage-mode resonant switches. Application of the multi-resonant switch in zero-voltage switched multi-resonant converters results in reduction of the voltage stress to the switching transistor, increase of the load range and reduction of the switching frequency bandwidth. Each embodiment of the multi-resonant converter includes a multi-resonant switch having an active switch, a passive switch and reactive components for causing the active and passive switches to operate in a multi-resonant manner.

Growing community of inventors

Blacksburg, VA, United States of America

Wojciech A Tabisz