JPH0728530B2 - Switching Regulator - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator, and more particularly to a switching regulator for supplying a stabilized power supply to a power amplifier using a FET (field effect transistor) used in a transmitter of a wireless communication device. It is a thing.

2. Related Art An example of a conventional switching regulator and an example of connection with an amplifier are shown in FIG. In the figure, 1 is a power amplifier power supply including a switching regulator, 2 is a power amplifier, 11-1 and 2 are input terminals, 20 is a switching element, 21 is a voltage conversion transformer, 22 is a rectifier circuit, and 23 is an output smoother. Circuit, 24 is an input voltage smoothing circuit, 25 is a switching element 20
A drive circuit for controlling the ON / OFF of the output voltage, and 26 is a voltage conversion transformer 21, a rectifier circuit 22 and a smoothing circuit by converting the fluctuation of the output voltage into a change of the pulse width and changing the ON / OFF ratio of the switching element 20 via the drive circuit 25. It is a pulse width modulation circuit that operates so as to keep the output voltage obtained through 23 constant.

Further, 27 is a reference voltage to be compared when the pulse width modulation circuit 26 converts the fluctuation of the output voltage into the change of the pulse width, 12-1, 2
Is an output terminal that supplies a voltage (abbreviated as drain voltage) to the drain electrode of the FET used in the power amplifier 2, 13 is a power source for the gate electrode, and 14 is a voltage (gate voltage and It is an output terminal for supplying (abbreviated). The power amplifier 2 starts to operate as a transmitter of the wireless communication device when the drain voltage and the gate voltage are supplied.

It is necessary to select the type of FET used in the power amplifier 2 according to the signal frequency to be transmitted. Generally, the higher the signal frequency to be amplified, the lower the maximum rated voltage between the drain and source of the FET. Tend. Therefore, there is a drawback in that the drain voltage, which is the output voltage of the switching regulator, must be changed according to the signal frequency amplified by the power amplifier 2. Further, since the FET used in the power amplifier generally has a depletion characteristic, the drain voltage, which is the output voltage of the switching regulator, should be applied to the drain electrode after the gate voltage is applied to the gate electrode. Otherwise, the FET would be damaged.

OBJECT OF THE INVENTION It is an object of the present invention to provide a switching regulator that allows a regulated voltage to be an optimum drain voltage for the type of FET used.

Another object of the present invention is to provide a switching regulator designed to prevent damage to the FET to which the electrode is supplied.

According to the present invention, in order to supply a stabilized operating voltage to a power amplifier using a field effect transistor, a reference voltage and an output voltage are compared, and a switching element is switching-controlled according to the comparison output. And a reference voltage generation source for generating the reference voltage is configured to be variable according to an external control signal, the external control signal being dependent on a signal frequency to be amplified by the field effect transistor. A switching regulator having an information signal according to different optimum drain voltages is obtained.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and the same portions as those in FIG. 2 are designated by the same reference numerals. In the figure, 15
Is a FET that is sent out immediately after the voltage is applied to the gate electrode
An input terminal for a feedback signal from the power amplifier 2 has a switching function for starting the operation of a switching regulator for drain voltage by this feedback signal and a function for sending a signal for determining the drain voltage according to the signal level and the like. The detection circuit 29 is a variable reference voltage source that changes the reference voltage of the switching regulator in order to change the drain voltage, which is the output voltage of the switching regulator, required by the signal voltage sent from the detection circuit 28. Other configurations are the same as those of FIG. 2,
The description is omitted.

The operation will be described below. First, the power amplifier 2 terminal
A gate voltage is supplied from the gate electrode power supply 13 via 14. At this time, the drain voltage of the FET is not yet applied. Next, when the application of the gate voltage is completed, the input terminal
A feedback signal containing information necessary for setting the drain voltage is sent to the detection circuit 28 via 15. The detection circuit 28 sends a control signal for generating a drain voltage which is an output voltage of the switching regulator and an information signal necessary for setting the drain voltage to the variable reference voltage source 29.

The variable reference voltage source 29 generates a reference voltage necessary for setting the drain voltage, which is the output voltage of the switching regulator, based on this information signal. Therefore, the optimum drain voltage for the operation of the FET is generated at the outputs 12-1, 2 of the switching regulator.

The information signal generated from the power amplifier 2 to the terminal 15 is
Information according to the optimum drain voltage determined depending on the FET used may be automatically generated (by using a microprocessor or the like), or may be manually set.

As described above, according to the present invention, the external reference signal including the information designating the optimum drain voltage of the FET selected according to the signal frequency used for the power amplifier is used as the variable reference voltage of the switching regulator. Since the variable reference voltage is supplied to the power source and the variable reference voltage is set and controlled according to the FET, the optimum drain voltage is always supplied to the FET.

Further, after the gate voltage of the FET is applied, the switching regulator is activated to generate the optimum drain voltage, so that the FET is prevented from being damaged.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional switching rectifier. Explanation of symbols of main parts 1 …… Switching regulator 2 …… Power amplifier 20 …… Switching element 28 …… Detecting circuit 29 …… Variable reference voltage source

Claims (2)

[Claims] 1. A switching device which compares a reference voltage with an output voltage and controls switching of a switching element according to the comparison output in order to supply a stabilized operating voltage to a power amplifier using a field effect transistor. In the regulator, a reference voltage generation source that generates the reference voltage is configured to be variable according to an external control signal, and the external control signal is an optimum drain voltage that varies depending on a signal frequency to be amplified by the field effect transistor. A switching regulator characterized by being an information signal according to. 2. The switching regulator according to claim 1, wherein the external control signal is generated after a voltage is applied to the gate electrode of the field effect transistor.