Patent ID: 8134816

Claim:
A high-frequency power supply system for supplying high-frequency power from a high-frequency power source to a load via an impedance matching unit, the system comprising: a first detector for detecting information about a forward wave traveling from the high-frequency power source toward the load; a second detector for detecting information about a reflected wave traveling from the load toward the high-frequency power source; a differentiator for calculating a change of a magnitude of reflection coefficient per unit time at a detection point provided for the first and the second detectors based on the information about the forward wave detected by the first detector and the information about the reflected wave detected by the second detector; and an anomaly determiner for determining an occurrence of an anomaly on a side toward the load as from the detection point provided for the first and the second detectors based on the change of the magnitude of reflection coefficient per unit time calculated by the differentiator; wherein the anomaly determiner includes a counter for counting the number of times when the change of the magnitude of reflection coefficient per unit time exceeds a first predetermined reference value, and determines the occurrence of anomaly when the number of times counted by the counter exceeds a predetermined norm number, the high-frequency power supply system further comprising: an output power changer for changing an electric power outputted from the high-frequency power source in a decreasing direction upon detection of an occurrence of anomaly by the anomaly detector; an output power resumption unit for bringing the electric power outputted from the high-frequency power source back to an original amount after a lapse of a first predetermined time from upon the change made by the output power changer on the output power; and a matching operation stopping unit for stopping a matching operation performed by the impedance matching and holding operation parameters upon the change made by the output power changer on the output power from the high-frequency power source.