RF heating system with phase detection for impedance network tuning

Patent metadata

Field	Value
Publication number	US-10917065-B2
Application number	US-202016917035-A
Country	US
Kind code	B2
Filing date	Jun 30, 2020
Priority date	Nov 17, 2017
Publication date	Feb 9, 2021
Grant date	Feb 9, 2021

Abstract

A system and method for tuning an impedance network of a device is provided. An RF signal is provided through a transmission path connected to an impedance matching network that includes a first variable component and a second variable component. A phase angle between a forward signal and a reflected signal along the transmission path is determined. Based on the phase angle between the forward signal and the reflected signal, the first variable component is modified to improve an impedance match between the RF signal source and the electrode. After modifying the first variable component, a ratio of a power of the reflected signal to a power of the forward signal is determined, and an inductance of the second variable component is modified to reduce the ratio of a power of the reflected signal to a power of the forward signal.

First claim

The invention claimed is:

1. A method comprising:
generating, by a radio frequency (RF) signal source, a forward signal along a transmission path electrically coupled between the RF signal source and an electrode;
performing impedance matching by an impedance matching network electrically coupled to an output of the RF signal source, wherein the impedance matching network is an inductor-only network that does not include capacitors, and the impedance matching network includes:
a series inductance coupled along the transmission path, wherein the series inductance includes a first terminal coupled to the RF signal source, and a second terminal coupled to an electrode,
a first shunt inductive network directly connected to the second terminal of the series inductance, wherein the first shunt inductive network includes a first variable inductance network coupled between the second terminal of the series inductance and a ground reference, and
a second shunt inductive network directly connected to the first terminal of the series inductance, wherein the second shunt inductive network includes a second variable inductance network coupled between the first terminal of the series inductance and the ground reference;

determining, by power detection circuitry, a phase angle between the forward signal and a reflected signal along the transmission path;
causing, by a controller, the RF signal source to supply the forward signal at a relatively low power level;
while the RF signal source is supplying the forward signal at the relatively low power level, determining, by the controller, that the phase angle between the forward signal and the reflected signal is greater than a threshold phase angle value;
modifying, by the controller, based on the phase angle between the forward signal and the reflected signal, the first variable inductance network to reduce the phase angle between the forward signal and the reflected signal to a first phase angle that is less than the threshold phase angle value;
while the RF signal source is supplying the forward signal at the relatively low power level, determining, by the controller, that a ratio of a power of the reflected signal to a power of the forward signal is greater than a threshold power ratio;
modifying, by the controller, the second variable inductance network to reduce the ratio of the power of the reflected signal to the power of the forward signal to a first power ratio that is less than the threshold power ratio; and
after modifying the first and second variable inductance networks to reduce the phase angle between the forward signal and the reflected signal and to reduce the ratio of the power of the reflected signal to the power of the forward signal, causing, by the controller, the RF signal source to supply the forward signal at a relatively high power level.

2. The method of claim 1 , further comprising:
causing, by the controller, the RF signal source to produce the RF signal with a power less than 100 Watts while modifying at least one of the first variable inductance network and the second variable inductance network.

3. The method of claim 2 , further comprising:
after modifying at least one of the first variable inductance network and the second variable inductance network, the controller causing the RF signal source to increase a power of the RF signal to output a second RF signal having a power greater than 1,000 Watts.

4. The method of claim 1 , wherein the impedance matching network further comprises:
a plurality of fixed-value inductors with fixed inductance values coupled to the electrode.

5. The method of claim 1 , wherein the threshold phase angle value is less than 5 degrees.

6. The method of claim 1 , wherein the threshold power ratio is less than −15 decibels.

7. The method of claim 1 , further comprising:
repeatedly determining, by the controller, the phase angle between the forward signal and the reflected signal along the transmission path; and
repeatedly modifying, by the controller, based on the phase angle between the forward signal and the reflected signal, the first variable inductance network to improve an impedance match between the RF signal source and the electrode.

8. The method of claim 1 , wherein the first shunt inductive network further includes a fixed-value inductor with a first terminal directly connected to the second terminal of the series inductance, and a second terminal directly connected to the first variable inductance network.

9. A method comprising:
providing, by a radio frequency (RF) signal source, an RF signal along a transmission path electrically coupled between the RF signal source and an electrode;
performing impedance matching by an impedance matching network electrically coupled between the RF signal source and the electrode, wherein the impedance matching network is an inductor-only network that does not include capacitors, and the impedance matching network includes:
a first fixed-value inductor with a fixed inductance value, the first fixed-value inductor having a first terminal and a second terminal, wherein the first terminal of the first fixed-value inductor is coupled to the RF signal source, and the second terminal of the first fixed-value inductor is coupled to the electrode,
a first shunt inductive network directly connected to the second terminal of the first fixed-value inductor, wherein the first shunt inductive network includes a first variable inductance network coupled between the second terminal of the first fixed-value inductor and a ground reference node, and
a second shunt inductive network directly connected to the first terminal of the first fixed-value inductor, wherein the second shunt inductive network includes a second variable inductance network coupled between the first terminal of the first fixed-value inductor and the ground reference node;
causing, by a controller, the RF signal source to supply the RF signal at a relatively low power level;
while the RF signal source is supplying the forward signal at the relatively low power level, determining, by the controller, a phase angle between a forward signal and a reflected signal along the transmission path;
modifying, by the controller, based on the phase angle between the forward signal and the reflected signal, the first variable inductance network to improve an impedance match between the RF signal source and the electrode;
after modifying the first variable inductance network, determining, by the controller, a ratio of a power of the reflected signal to a power of the forward signal;
after modifying the first variable inductance network, modifying, by the controller, an inductance of the second variable inductance network to reduce the ratio of the power of the reflected signal to the power of the forward signal; and
after modifying the first variable inductance network to reduce the ratio of the power of the reflected signal to the power of the forward signal, the controller causing the RF signal source to supply the forward signal at a relatively high power level.

10. The method of claim 9 , wherein the controller causes the RF signal source to produce the RF signal with a power less than 100 Watts while modifying at least one of the first variable inductance network and the second variable inductance network.

11. The method of claim 10 , wherein the controller, after modifying at least one of the first variable inductance network and the second variable inductance network, causes the RF signal source to increase a power of the RF signal to output a second RF signal having a power greater than 1,000 Watts.

12. The method of claim 9 , further comprising:
repeatedly determ

Assignees

• Nxp Usa Inc

Inventors

• Mongin Lionel
• Piel Pierre Marie Jean
• Scott James Eric

Classifications

• H05B6/705 Primary

  using microwave tuning · CPC title

• F25D23/12

  Arrangements of compartments additional to cooling compartments; Combinations of refrigerators with other equipment, e.g. stove · CPC title

• H05B6/50 Primary

  for monitoring or control · CPC title

• H03H7/40 Primary

  Automatic matching of load impedance to source impedance · CPC title

• H05B6/54

  Electrodes · CPC title