MOSFET oscillator for supplying a high-power RF inductive load

• US 5,191,302 A
• Filed: 11/25/1991
• Issued: 03/02/1993
• Est. Priority Date: 11/25/1991
• Status: Expired due to Term

• Current Assignee: Lepel Corporation
• Original Assignee: Lepel Corporation
• Inventors: Rossnick, Melvin
• Primary Examiner(s): Grimm, Siegfried H.
• Application Number:
  US07/797,524
• Time in Patent Office: 463 Days
• Field of Search: 331/109, 331/112, 331/117 FE, 331/167, 331/182, 331/183, 219/10.75, 219/10.77
• US Class Current: 331/109
• CPC Class Codes: H03B 1/02 Structural details of power oscillators, e.g. for heating construction of transmitters H04B; features of generators for heating by electromagnetic fields H05B6/00
• CPC Class Codes: H03B 5/1203 the amplifier being a single transistor
• CPC Class Codes: H03B 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H03B 5/1296 the feedback circuit comprising a transformer

Abstract

A self-excited solid-state oscillator for supplying a high-power RF inductive load. The oscillator includes at least one MOSFET transistor connected in a self-excited oscillator configuration, an output tuned circuit including an inductive load and a tank circuit connected to the load, the tank circuit having a resonant frequency determined at least in part by the inductance of the load, an RF feedback transformer coupling the tank circuit to the gate of the MOSFET for providing a switching signal to the MOSFET for causing the MOSFET to alternate between the on state and the off state at a frequency equal to the resonant frequency of the tank circuit, and a bias circuit for superimposing a forward bias voltage on the switching signal.

Claims

1. A self-excited solid-state oscillator for supplying a high-power RF inductive load, comprising

(a) at least one MOSFET transistor connected in a self-excited oscillator configuration;

(b) an output tuned circuit comprising an inductive load and a tank circuit connected to the load, the tank circuit having a resonant frequency determined at least in part by the inductance of the load;

(c) an RF feedback transformer coupling the tank circuit to the gate of the MOSFET for providing a switching signal to the MOSFET for causing the MOSFET to alternate between the on state and the off state at a frequency equal to the resonant frequency of the tank circuit; and

(d) bias circuit means for superimposing a forward bias voltage on the switching signal.

2. A self-excited solid-state oscillator according to claim 1, further comprising means for modulating the switching signal to the MOSFET.

3. A self-excited solid-state oscillator according to claim 2, wherein the means for modulating the switching signal comprises a pulse-width modulator.

4. A power supply for supplying power to an inductive load, comprising

(a) a source of input power,

(b) a tank circuit for connection to said inductive load, the tank circuit having a resonant frequency determined at least in part by the inductance of said load,

(c) at least one MOSFET transistor connected in a self-excited oscillator configuration between the source of input power and the load,

(d) feedback means coupling the tank circuit to the gate of the MOSFET for providing a switching signal to the MOSFET for switching the MOSFET alternately between an on state and an off state at a frequency equal to the resonant frequency of the tank circuit,

(e) pulse-width modulator means for modulating the switching signal to the MOSFET, and

(f) bias circuit means for superimposing a bias voltage on the switching signal for biasing the MOSFET into its forward conduction region.