JPS62155770A - Switching regulator - Google Patents

Abstract

PURPOSE:To prevent the damage of a field-effect transistor by altering reference voltage by an information signal corresponding to the optimum drain voltage of the field-effect transistor as a power amplifier. CONSTITUTION:A gate for a power amplifier 2 is supplied with gate voltage from a power supply 13 for a gate electrode. When gate voltage is applied completely, a feedback signal including an information required for setting drain voltage is transmitted over a detection circuit 28 through an input terminal 15. The detection circuit 28 transmits a control signal generating drain voltage as the output voltage of a switching regulator and an information signal necessary for setting drain voltage over a variable reference voltage source 29. The variable reference voltage source 29 generates reference voltage needed for setting drain voltage as the output voltage of the switching regulator by the information signal.

Description

TECHNICAL FIELD The present invention relates to a switching regulator, and more particularly to a switching regulator for supplying stabilized power to a power amplifier using an FET (field effect transistor) used in a transmitting section of a wireless communication device. It is something.

Prior Art FIG. 2 shows an example of a conventional switching regulator and an example of its connection with an amplifier. In the figure, 1 is a power amplifier power supply including a switching regulator, 2 is a power amplifier, 11-1.2 is an input terminal, 20 is a switching element,
21 is a voltage conversion transformer, 22 is a rectifier circuit, 23 is an output smoothing circuit, 24 is an input voltage smoothing circuit, 25 is a drive circuit that controls the switching element 20 on and off, and 26 is a circuit that converts fluctuations in the output voltage into changes in pulse width. Convert and drive circuit 25
This is a pulse width modulation circuit that operates to maintain a constant output voltage obtained through a voltage conversion transformer 21, a rectifier circuit 22, and a smoothing circuit 23 by changing the on/off ratio of the switching element 20 through the voltage conversion transformer 21.

Furthermore, 27 is a reference voltage 12 that is compared when the pulse width modulation circuit 26 converts a fluctuation in the output voltage into a change in pulse width.
-1.2 is an output terminal that supplies voltage (abbreviated as drain voltage) to the drain electrode of the FET used in power amplifier 2;
3 is the power supply for the gate electrode, and 14 is the F used for the power amplifier 2.
This is an output terminal that supplies a voltage (abbreviated as G1-voltage) to the gate electrode of the ET. The power amplifier 2 is configured to start operating as a transmitting section of the wireless communication device by being supplied with the drain voltage and the G1~ voltage.

The type of FET used in the power amplifier 2 must be selected according to the signal frequency to be transmitted, and generally speaking, the higher the signal frequency to be amplified, the more the FET drain
The maximum rated voltage between sources tends to be lower. Therefore, there is a drawback that the drain voltage, which is the output voltage of the switching regulator, has to be changed in accordance with the signal frequency amplified by the power amplifier 2. Additionally, since FETs generally used in power amplifiers have depletion characteristics, the drain voltage, which is the output voltage of the switching regulator, is applied to the drain electrode after the gate voltage is applied to the gate electrode. Otherwise, there was a drawback that the FET would be damaged.

OBJECTS OF THE INVENTION An object of the present invention is to provide a switching regulator in which the stabilized voltage can be set to the optimal drain voltage for the type of FET used.

Another object of the present invention is to provide a switching regulator that prevents damage to FETs to which electrodes are to be supplied.

Structure of the Invention 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 switching of a switching element is controlled according to this comparison output. The switching regulator is configured such that a reference voltage generation source that generates the reference voltage is configured to be variable in accordance with an external control signal, and the external control signal is configured to be variable in accordance with an optimum drain voltage of the field effect transistor. A switching regulator characterized in that the signal is an information signal is obtained.

Example Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and parts equivalent to those in FIG. 2 are designated by the same reference numerals.

In the figure, 15 is an input terminal for a feedback signal from the FET power amplifier 2 that is sent out immediately after a voltage is applied to the gate electrode, and 28 is a switch function for starting the operation of the switching regulator for the drain voltage by this feedback signal. A detection circuit 29 has a function of sending out a signal that determines the drain voltage according to the signal level, etc., and 29 is for changing the drain voltage, which is the output voltage of the switching regulator, by the signal voltage sent out by the detection circuit 28. , is a variable reference voltage source that varies the reference voltage of the switching regulator.

The other configurations are the same as those shown in FIG. 2, and their explanation will be omitted.

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

The variable reference voltage source 29 uses this information signal to generate a reference voltage necessary for setting the drain voltage, which is the output voltage of the switching regulator. Therefore, the optimal drain voltage for the operation of the FET is generated at the output 12-1.2 of the switching regulator.

Note that the information signal generated from the power amplifier 2 to the terminal 15 is such that information corresponding to the optimum drain voltage determined depending on the FET used is automatically generated (by using a microprocessor, etc.). Alternatively, it may be set manually.

Effects of the Invention As described above, according to the present invention, the external control signal containing information specifying the optimum drain voltage of the FET selected according to the signal frequency used in the power amplifier is used as the variable reference voltage of the switching regulator. so as to supply it to the source,
Since this variable reference voltage is set and controlled according to the FET, there is an effect that the optimum drain voltage is always supplied to the FET.

Further, by activating the switching regulator to generate the optimum drain voltage after applying the gate voltage of the FET, damage to the FET can be prevented.

[Brief explanation 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 regulator. Explanation of symbols of main parts 1...Switching regulator 2...
・Power amplifier 20...Switching element 28...Detection circuit

Claims (2)

[Claims] (1) A switching regulator that compares a reference voltage with an output voltage and controls the switching of a switching element according to the comparison output in order to supply a stabilized operating voltage to a power amplifier using field effect transistors. The 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 information signal corresponding to the optimum drain voltage of the field effect transistor. Switching regulator with special features. (2) The switching regulator according to claim 1, wherein the external control voltage is generated after a voltage is applied to the gate electrode of the field effect transistor.