| 摘要 |
A power supply device, a signal output apparatus and a power supply method are provided to reduce a loss suitably even though power is supplied to an output device which outputs a high-frequency signal. A signal output apparatus includes a transmission signal generator(10), a pulse generation circuit(80), and a voltage converter(40). A transmission signal generated by the transmission signal generator is inputted to an amplifier(20) and is also inputted to a low pass filter(60). A filter of several ten MHz is used as the low pass filter. The envelope of the transmission signal is extracted by the low pass filter. The extracted envelope is sampled by a 2 GHz AD converter(70) and the sampled signal is sent to the pulse generation circuit. The pulse generation circuit is a circuit for generating a pulse signal for controlling the power supply voltage by PWM(Pulse Width Modulation) control and inputting the pulse signal to the voltage converter. This circuit generates the pulse signal at a constant frequency by on-off control of the 2 GHz fundamental pulses. In the pulse generation circuit, the pulse width with respect to the magnitude of the envelope obtained from the AD converter is set in advance in an association table on the basis of the known relationship. The pulse width of the pulse signal is obtained at a high speed from the envelope of the transmission signal by using the association table, and the pulse signal having the pulse width thus determined is generated. The pulse signal generated in this way is inputted to the voltage converter. The voltage converter includes two semiconductor switches(41,42) which perform switching operations according to the pulse signal in a contrary relationship with each other. A constant-voltage power supply is connected to the voltage converter. The constant voltage power supply(50) is a power supply designed so as to stabilize the output voltage. A stabilized voltage is supplied from the constant voltage power supply to the voltage converter. This stabilized voltage is converted into a voltage according to the duty ratio of the pulse signal by the switching operations of the semiconductor switches, and the converted voltage is output from the voltage converter.
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