Protecting High-Frequency Amplifers

• US 20100171427A1
• Filed: 01/12/2010
• Published: 07/08/2010
• Est. Priority Date: 07/23/2007
• Status: Active Grant

• Current Assignee: Hüttinger Elektronik GmbH + Co. KG
• Original Assignee: Hüttinger Elektronik GmbH + Co. KG
• Inventors: Kirchmeier, Thomas, Glueck, Michael
• Granted Patent: US 8,421,377 B2
• Time in Patent Office: Days
• US Class Current: 315/111.210
• CPC Class Codes: G01R 21/06 by measuring current and voltage G01R21/08 - G01R21/133 take precedence
• CPC Class Codes: G01R 23/02 Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
• CPC Class Codes: H01J 37/32045 Circuits specially adapted for controlling the glow discharge
• CPC Class Codes: H02M 7/003 Constructional details, e.g. physical layout, assembly, wiring or busbar connections
• CPC Class Codes: H02M 7/5383 in a self-oscillating arrangement H02M7/538 takes precedence
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance
• CPC Class Codes: H05B 41/2806 with semiconductor devices and specially adapted for lamps without electrodes in the vessel, e.g. surface discharge lamps, electrodeless discharge lamps
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

In one aspect, protecting high frequency (HF) amplifiers of a plasma supply device configured to deliver >500 W at a substantially constant fundamental frequency >3 MHz is accomplished by: driving two HF amplifiers with two drive signals having a common frequency and a predetermined phase shift with respect to one another; generating two HF source signals using the HF amplifiers, the HF source signals coupled in a coupler to form a HF output signal; transmitting the HF output signal to the plasma load; measuring electrical variables related to the load impedances seen by the two HF amplifiers; determining whether the load impedance seen by one of the HF amplifiers lies outside a predetermined range; and adjusting the phase shift of the two drive signals, wherein neither of the load impedances seen by the HF amplifiers lies outside the predetermined range.

Claims

1. A method of protecting high-frequency amplifiers of a plasma supply device configured to deliver a high-frequency output signal having a power of more than 500 W and a substantially constant fundamental frequency greater than 3 MHz to a plasma load, the method comprising:

driving two high frequency amplifiers with two drive signals having a common frequency and a predetermined phase shift with respect to one another;

generating two high frequency source signals using the two high frequency amplifiers, the two high frequency source signals being coupled in a coupler to form a combined high frequency output signal;

transmitting the combined high frequency output signal to the plasma load;

measuring electrical variables related to load impedances seen by the two high frequency amplifiers; and

in response to determining that a load impedance seen by one of the two high frequency amplifiers lies outside a predetermined range, adjusting the phase shift of the two drive signals sufficiently to cause a phase shift of the high frequency source signals with respect to one another, the phase shift of the high frequency source signals causing the load impedances seen by the two high frequency amplifiers to lie within the predetermined range.

2. The method of claim 1, further comprising determining a phase angle of the load impedance seen by at least one of the two high frequency amplifiers, or a variable related thereto.

3. The method of claim 1, further comprising determining an instantaneous value of a high frequency signal supplied to the plasma load and reflected by the plasma load, or the instantaneous value of a high frequency voltage and a high frequency current at a port of the coupler or at an output of one of the two high frequency amplifiers.

4. The method of claim 1, wherein measuring the electrical variables comprises measuring D.C. power consumption.

5. The method of claim 1, wherein adjusting the phase shift of the two drive signals includes adjusting a phase angle of one of the drive signals.

6. The method of claim 1, further comprising regulating an output of at least one of the high frequency amplifiers while adjusting the phase shift of the two drive signals.

7. The method of claim 1, further comprising controlling an output of at least one of the high frequency amplifiers using a drive signal generator.

8. The method of claim 1, further comprising controlling an output of at least one of the high frequency amplifiers based on the adjustment of the phase shift of the two drive signals, using a drive signal generator.

9. The method of claim 1, wherein adjusting the phase shift of the two drive signals comprises determining an adjustment value from a table.

10. A plasma supply device configured to generate and supply an output power of more than 500 W at a substantially constant fundamental frequency greater than 3 MHz in the form of a high-frequency output signal to a plasma load, the plasma supply device comprising:

a first phase shifter;

two high frequency amplifiers, each having at least one switching element and an output;

a drive signal generator configured to drive the two high frequency amplifiers with a predetermined phase shift using the first phase shifter;

a coupler having first and second ports coupled to respective outputs of the two high frequency amplifiers, and having a third port at least indirectly connected to the plasma load;

a sensor responsive to an electrical variable indicative of the load impedances seen by the two high frequency amplifiers; and

a phase adjuster configured to cooperate with the drive signal generator to adjust the phase shift of the drive signals of the high frequency amplifiers with respect to one another based on input from the sensor.

11. The plasma supply device of claim 10, wherein the phase adjuster is integrated in the first phase shifter.

12. The plasma supply device of claim 10, wherein the phase adjuster is in the form of a second phase shifter.

13. The plasma supply device of claim 10, wherein the first phase shifter and/or the phase adjuster are formed in the drive signal generator.

14. The plasma supply device of claim 10, wherein the drive signal generator comprises a digital circuit configured to select a phase shift adjustment value.

15. The plasma supply device of claim 14, wherein the digital circuit is a digital signal processor.

16. The plasma supply device of claim 10, wherein the coupler is in the form of a hybrid coupler.