| 摘要 |
The RF power amplifier (PAI) comprises a synchronous insulated power supply (220), a bridge-type circuit comprising a first switch with transistors (70,76) and a second switch with transistors (72,74), so that when one or the other switch is in on-state a current flows through a load connected to the secondary coil of transformer (T1) in one or the other direction, and a control circuit comprising a logic circuit for the provision of on-state signals and their selective application to allow the passage of RF pulses to the switches, so that the first and the second switches are set in on-state and in off-state in synchronization with the beginning and the end of the RF period. The amplifier system comprising a set of power amplifiers with inputs of digital signal levels used as control signals and outputs combined by a set of transformers, also comprises a circuit for the generation of RF pulses in phase A and in phase B, which are phase-shifted by 180 degrees and the control circuit of power amplifier comprises first and second logic gates, which when validated, pass the pulses for the control of switches. The RF pulses in phase A and phase B are generated so that there exists an interval between the pulses in two phases, in order to avoid the setting of the first and the second transistors simultaneously in on-state. The logic circuit comprises a bistable circuit of type D (302) having inputs (D,CLK) and outputs (Q, Q inverse), where the pulses in phase B are applied to the input D, and the on-state signal to the input CLK, for the synchronized control of power amplifier by validating the first and the second logic gates (300,310,320,330). The circuit for the generation of RF pulses comprises an RF oscillator, and a monostable circuit in the line of phase A, and an inverter in series with a monostable circuit in the line of phase B. The synchronous power supply (220) used for the provision of supply voltages, to buffer amplifiers, is of semi-bridge type and comprises first and second switching transistors, a transformer with a primary coil and a set of secondary coils connected to full-wave rectifiers, and a control circuit comprising an inverter, a frequency divider-by-2 circuit, and a monostable circuit in the line to the gate of each transistor. The transistors are of MOSFET type.
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