| 摘要 |
PURPOSE:To prevent destruction of elements of a power amplifying circuit by controlling the progressive wave power so that it is constant if the reflected wave power detected by a high frequency power detecting circuit is small but it is reduced if the reflected wave power is large. CONSTITUTION:A high frequency power supply device 1 is connected to a load 2 through a matching circuit 3 and supplies a high frequency power. This device 1 consists of an oscillating circuit 11, a buffer amplifying circuit 12, a power amplifying circuit 13, a high frequency power detecting circuit 14 which detects the progressive wave power and the reflected wave power, a power control circuit 18 which controls said power amplifying circuit 13, etc. The power control circuit 18 controls the circuit 13 so that the progressive wave power is equalized to a preliminarily set progressive wave power value if the reflected wave power is small but the progressive wave power is reduced if the reflected wave power is large. Thus, when the impedance of the load 2 is changed to increase the reflected wave power, the power gain of the power amplifying circuit 13 is reduced to prevent destruction of elements, and oscillation is continued. |
