Piezoelectric driver using resonant energy transfer

• US 5,126,589 A
• Filed: 08/31/1990
• Issued: 06/30/1992
• Est. Priority Date: 08/31/1990
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Siemens Pacesetter, Inc. (Abbott Laboratories Incorporated)
• Inventors: Renger, Herman L.
• Primary Examiner(s): Zazworsky, John
• Application Number:
  US07/575,922
• Time in Patent Office: 669 Days
• Field of Search: 307/270, 307/271, 307/308, 307/261, 307/246, 328/67, 328/113, 328/123, 328/27, 310/316, 310/314, 310/321
• US Class Current: 327/111
• CPC Class Codes: B06B 1/023 and stepped in amplitude, e.g. square wave, 2-level signal
• CPC Class Codes: B06B 2201/55 Piezoelectric transducer
• CPC Class Codes: H10N 30/802 Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for

Abstract

A drive circuit for use with a capacitive load includes two transistors controlled by a drive voltage and connected to the load through an inductor. A supply voltage is alternately connected and disconnected to the circuit to achieve a resonant transfer of energy from the supply voltage. Energy stored in the load is transferred to the inductor and then back to the load, thereby reversing and augmenting the output voltage across the load and providing an instantaneous output voltage many times the supply voltage. Diodes ensure that the current flows in the proper polarity through the transistors.

Claims

1. A drive circuit for driving a capacitive load, comprising:

an inductive element having a first terminal and a second terminal, connected at its first terminal in series with the capacitive load and forming an L-C circuit having a resonant frequency;

a supply voltage source;

a reference voltage source;

switching means for alternately connecting the second terminal of the inductive element to the supply voltage source and then to the reference voltage source at a predetermined frequency, such that the voltage across the capacitive load reaches a first level when the current through the inductive element reaches its peak, and then energy is transferred from the inductive element to the capacitive load until the voltage across the capacitive load reaches a second level higher than the first level during a first part of the alternating cycle, and the capacitive load discharges energy into the inductive element until current through the inductive element reaches a peak having the opposite polarity and a greater magnitude than the first inductive element current peak, producing a third voltage level across the capacitive load equal in magnitude an opposite in polarity from the second level during a second part of the alternating cycle, and the alternating cycle is then begun again, whereby the transfer of energy occurs at the resonant frequency of the L-C circuit, and the voltage across the capacitive load is augmented by the energy from the supply voltage source through the inductive element, and increases with each alternating cycle; and

controller means, connected between the switching means and the L-C circuit, for responding to a predetermined voltage level in the L-C circuit by disconnecting the supply voltage source from the L-C circuit when the voltage level in the L-C circuit exceeds the predetermined voltage level.

2. A drive circuit as recited in claim 1, wherein the switching means comprises:

a first MOSFET having a gate, a drain, and a source, the source of the first MOSFET being coupled to the supply voltage source;

a second MOSFET having a gate, a drain, an a source, the source of the second MOSFET being coupled to the reference voltage source;

a first diode connecting the drain of the first MOSFET to the second terminal of the inductive element;

a second diode connecting the drain of the second MOSFET to the second terminal of the inductive element; and

drive means for producing a cyclic drive voltage having a predetermined cycle time including a waiting time interval and being connected to the gate of each MOSFET;

wherein the cyclic drive voltage controls the first MOSFET and second MOSFET such that when the first MOSFET is conducting the second MOSFET is nonconducting, and when the second MOSFET is conducting the first MOSFET is nonconducting.

3. A drive circuit as recited in claim 2, wherein the drive means controls the drive voltage such that the cycle time of the drive voltage results in a drive voltage frequency that is lower than the L-C circuit resonant frequency.

4. A drive circuit as recited in claim 2, further comprising:

a third MOSFET having a gate coupled to the drive means, a source coupled to the reference voltage source, and a drain;

a third diode connecting the drain of the third MOSFET to the second terminal of the inductive element; and

whereby the conductive state of the third MOSFET changes in accordance with the value of the cyclic drive voltage.

5. A drive circuit for use with a capacitive load, the capacitive load having a first terminal and a second terminal and being connected at its first terminal to a reference voltage source, the drive circuit comprising:

an inductor having a first terminal and a second terminal, the inductor being connected at its first terminal in series with the second terminal of the capacitive load and forming an L-C circuit having an L-C circuit resonant frequency;

a supply voltage source producing a voltage at a supply potential of +V with respect to the reference voltage source; and

switching means for alternately connecting the second terminal of the inductor to the supply voltage source and then to the reference voltage source, wherein the switching means comprises;

a first MOSFET having a gate, a drain, and a source, the source of the second MOSFET coupled to the reference potential source;

a second MOSFET complementary to the first MOSFET, having a gate, a drain, and a source, the source of the second MOSFET coupled to the supply voltage source;

a first diode connecting the drain of the first MOSFET to the second terminal of the inductor;

a second diode connecting the drain of the second MOSFET to the second terminal of the inductor;

drive means, connected to the gage of each MOSFET, for producing a cyclic drive voltage having a predetermined frequency less than the L-C circuit resonant frequency and for controlling the first MOSFET and second MOSFET such that when the first MOSFET is conducting the second MOSFET is nonconducting and when the second MOSFET is conducting the first MOSFET is nonconducting; and

controller means, connected to the L-C circuit, for responding to a predetermined voltage level in the L-C circuit when the voltage level in the L-C circuit exceeds the predetermined voltage level by biasing off the second MOSFET, thereby disconnecting the supply voltage source from the L-C circuit.

6. A drive circuit as recited in claim 5, wherein the control means comprises:

a third MOSFET having a gate, a drain, and a source, the gate of the third MOSFET coupled to the drive means and the source of the third MOSFET coupled to the reference voltage source;

a third diode connecting the drain of the third MOSFET to the second terminal of the inductor; and

peak responding means, connected to the L-C circuit, for responding to a predetermined voltage level in the L-C circuit to render the second MOSFET nonconductive when the voltage level in the L-C circuit exceeds the predetermined voltage level.

7. A drive circuit for use with a capacitive load, the drive circuit comprising:

an inductive element having a first terminal and a second terminal, connected at its first terminal in series with the capacitive load and forming an L-C circuit having a resonant frequency;

a supply voltage source;

a reference voltage source;

switching means for alternately connecting, at a predetermined frequency less than the resonant frequency of the L-C circuit, the second terminal of the inductive element to the supply voltage source for causing current to flow through the inductive element in a first direction and then to the reference voltage source for causing current to flow through the inductive element in a direction opposite to the first direction; and

energy limiting means, connected to the L-C circuit, for responding to a predetermined voltage level in the L-C circuit by disconnecting the supply voltage source from the L-C circuit when the voltage level in the L-C circuit exceeds the predetermined voltage level.

8. A method of driving a capacitive load with a supply voltage, the capacitive load being connected to an inductive element that together with the load comprises an L-C circuit having a resonant frequency, comprising the steps of:

connecting the supply voltage through a first diode to the L-C circuit for a predetermined time interval at least equal to one-half the cycle time of the L-C circuit resonant frequency, such that the capacitive load voltage reaches a first load voltage level and the inductive element current reaches an inductive current value;

allowing the current through the inductive element to decrease to zero during the predetermined time interval as the load voltage reaches a second load voltage level greater than the supply voltage;

disconnecting the supply voltage from the L-C circuit after the predetermined time interval has expired, allowing the load to discharge its energy into the inductive element through a second diode and allowing the inductive element to discharge its energy back into the load, producing a third load voltage level at least substantially equal in magnitude and opposite in polarity from the second load voltage level;

detecting when the second load voltage level exceeds a predetermined desired peak value; and

causing the current in the L-C circuit to flow through a third diode to the reference voltage source, instead of the supply voltage source, thereby limiting the load voltage level to substantially the peak value.