JPH0112547Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a switching regulator with improved input/output characteristics.

BACKGROUND ART Generally, batteries are used as a driving power source in various portable or vehicle-mounted electronic devices such as video tape recorders (VTRs) and video cameras. In this type of power supply, there is a possibility that the terminal voltage thereof may fluctuate greatly due to a sudden change in load due to switching of operating modes or the like. Such fluctuations are an obstacle to stable operation of electronic equipment, so
Switching regulators are used to suppress such fluctuations, and improving the input/output characteristics of switching regulators is essential for stabilizing the operation of various electronic devices.

Therefore, the object of the present invention is to provide a switching regulator with improved input/output characteristics.

That is, the switching regulator of this invention includes a first transistor that converts DC input into AC by switching, a constant voltage circuit that generates a constant voltage when the DC input is applied, and the first transistor. a second transistor connected to the base, a base voltage is supplied together with the constant voltage from the constant voltage circuit to the base, and switches the first transistor; a feedback circuit that provides positive feedback through a capacitor to the base of the second transistor to cause the second transistor to oscillate; a DC regeneration circuit that converts the AC obtained through the first transistor into a DC output; and a DC regeneration circuit that converts the AC obtained through the first transistor into DC output; A constant voltage diode generates a reference voltage, and an operating current is supplied to the collector through the constant voltage circuit, and the reference voltage applied to the emitter is compared with the DC output applied to the base. The third transistor draws a current from the base of the second transistor according to the relationship, and controls the base current of the first transistor through the second transistor.

Hereinafter, this invention will be described in detail with reference to embodiments shown in the drawings.

In the switching regulator of this invention, the constant voltage circuit has a series circuit including a resistor and a constant voltage diode connected to the DC input side.

FIG. 1 shows an embodiment of the switching regulator of this invention.

An input voltage V _i is applied as a DC input between the input terminals 2A and 2B. This DC input section has
A constant voltage circuit 6 that generates a specific constant voltage based on the input voltage V _i is installed together with a capacitor 4 for absorbing ripples contained in the input voltage V _i . The constant voltage circuit 6 includes a series circuit including a resistor 8 and a constant voltage diode 10 connected in series between the input terminals 2A and 2B.

A switching transistor 14 is connected as a first transistor between the input terminal 2A and the output terminal 12A, with the emitter on the input terminal 2A side and the collector on the output terminal 12A side. The switching transistor 14 converts the input voltage V _i into alternating current by switching, and the alternating current voltage obtained through the switching transistor 14 is sent to a direct current regeneration circuit 16 installed to regenerate direct current by rectification. has been added. The output terminal 12B and the input terminal 2B are commonly connected to a reference potential point (GND).

In the DC regeneration circuit 16, a switch coil 18 is connected in series to the switching transistor 14, and a diode 20 is connected between the collector of the switching transistor 14 and a reference potential point with the collector side serving as a cathode. A smoothing capacitor 22 is connected between the output terminal and the reference potential point. The chiyoke coil 18 includes a primary coil 18P.
A secondary coil 18S is also provided, and the polarities of these coils 18P and 18S are set so that the induced electromotive force is opposite to each other, and the terminal on the output terminal 12A side is shared. One terminal of the secondary coil 18S of this York coil 18 is connected to the base of the switching transistor 14 via a differential capacitor 24, so that the differential waveform of the switching pulse is applied to the base of the switching transistor 14. It's summery.
A bias resistor 26 is connected between the base and emitter of the switching transistor 14.

The output voltage is between the output terminals 12A and 12B.
In order to detect fluctuations in V _p , resistors 28 and 30 are connected in series, and an error amplifier is configured at the connection point of these resistors 28 and 30 to detect fluctuations in the level of output voltage V _p . The base of a control transistor 32 installed as a third transistor that controls the switching operation based on is connected. A constant voltage diode 34 is connected between the emitter of the control transistor 32 and the reference potential point with the cathode on the emitter side.
The output of the DC regeneration circuit 16 is applied through a resistor 36 to a connection point between the voltage regulator diode 34 and the emitter of the grounding transistor 32.

The collector of the control transistor 32 is connected to the base of a driving transistor 38, which is installed as a second transistor for switching the switching transistor 14, and also connected to the resistor 8 of the constant voltage circuit 6 and the constant voltage diode 1.
0 via a resistor 39, and upon application of the input voltage _Vi , a constant current is supplied from the constant voltage circuit 6 to the collector/emitter of the control transistor 32 and the base of the drive transistor 38. That is, an operating current is supplied to the collector of the control transistor 32 through the constant voltage circuit 6, and the reference voltage applied to the emitter and the DC output applied to the base are compared. Through this comparison, the current that corresponds to the magnitude relationship between the two is determined by the driving transistor 3.
8 into the control transistor 32, and the base current of the switching transistor 14 is controlled through the drive transistor 38.

Further, the base of the driving transistor 38 has a
The collector of the switching transistor 14 is connected via a feedback circuit consisting of a capacitor 40.
The switching pulse as an alternating current obtained by the switching transistor 14 is fed back positively. That is, the driving transistor 38 constitutes an oscillation circuit together with the base/collector of the switching transistor 14 and the capacitor 40, and the width of the oscillation pulse is controlled by the operating current of the control transistor 32. Therefore, the transistor 38 and the transistor 32 constitute a pulse width modulation circuit.

In the above configuration, the operation will be explained.

The driving transistor 38 for causing a driving current to flow through the switching transistor 14 oscillates with the switching pulse being positively fed back to its base via the capacitor 40. In this oscillation operation,
The base current of transistor 38 is controlled by the operation of transistor 32. That is, the operating current of the transistor 32 corresponds to the output fluctuation, and the output fluctuation is set by the DC output divided by the output voltage V _p with the resistors 28 and 30 and applied to the base, and the constant voltage diode 34 at the emitter. It is determined by comparing it with the reference voltage. Therefore, the control pulse applied to the base of the switching transistor 14 is a pulse width modulated signal corresponding to the fluctuation level of the DC output. As a result, the switching transistor 14 performs a switching operation.

Such control operations are performed continuously, and the input voltage V _i applied to the input terminals 2A and 2B passes through the switching transistor 14, is converted into a switching pulse, and is converted into DC through the DC regeneration circuit 16. The converted and stabilized output voltage V _p can be taken out from the output terminals 12A and 12B.

In this switching operation, the DC input voltage V _i applied to the input terminals 2A and 2B is applied to the constant voltage circuit 6, and a constant current is generated from the connection point between the resistor 8 and the constant voltage diode 10 via the resistor 39. It flows into the collector of the control transistor 32 and the base of the drive transistor 38. That is, the emitters of the control transistor 32 and the drive transistor 38 are made to have a constant voltage by applying the output side voltage, and from the relationship between the value of this constant voltage and the constant voltage generated at the cathode of the constant voltage diode 10, the resistor 39 A constant current flows through the transistors 38 and 32, and as a result, the operating current of each transistor 38, 32 is made constant. Therefore, a reference voltage corresponding to the input voltage V _i is formed in the constant voltage diode 34 .

The operating current of the transistor 32 is determined according to the magnitude relationship between the base-emitter voltage of the transistor 32 added to the reference voltage thus set and the divided voltage of the output voltage, and the output voltage is It will be controlled. As a result, the input/output characteristics of the switching regulator are improved.

And the secondary coil 18 of the chiyoke coil 18
The pulse waveform induced in S has a polarity opposite to that of the pulse waveform applied to the primary coil 18P.
Since this waveform is differentiated by the capacitor 24 and applied to the base of the switching transistor 14, the base potential of the switching transistor 14 is reverse biased during switching,
The switching time can be improved.

Furthermore, since the drive current of the switching transistor 14 flowing to the drive transistor 38 is supplied from the emitter of the transistor 38 to the output side of the DC regeneration circuit 16, current loss is reduced and conversion efficiency is improved. There is.

Next, the experimental results of this idea are shown in Figures 2 to 4.
This will be explained in detail with reference to the drawings.

The switching regulator shown in FIG. 2 uses a resistor 42 instead of the constant voltage circuit 6 for comparison with the embodiment described above, and the same parts as in the embodiment described above are given the same reference numerals. It has been done. FIG. 3 shows the input/output characteristics of the switching regulator according to this invention, and FIG. 4 shows the input/output characteristics of the switching regulator shown in FIG. 2. In Figures 3 and 4, characteristic A is -20℃ and characteristic B is 25℃.
℃, Characteristic C was measured at an ambient temperature of 80℃. Comparing each characteristic, the output voltage fluctuates in response to the increase in input voltage in the characteristic shown in FIG. 4, but the fluctuation is extremely small in the characteristic shown in FIG. It can be seen that the switching regulator of this invention, in which the operating currents of the control transistor 32 and the drive transistor 38 are made constant, has excellent input/output characteristics.

As explained above, according to this invention, since the operating current of the drive transistor and control transistor is made constant, the input/output characteristics can be improved, and the input/output characteristics are not affected by temperature changes. It is possible to obtain stable DC output without being affected by

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an embodiment of the switching regulator of this invention, and Figure 2 is a circuit diagram showing a switching regulator for comparison of characteristics with the switching regulator shown in Figure 1. Fig. 3 is an explanatory diagram showing the input/output characteristics of the switching regulator shown in Fig. 1, and Fig. 4 is an explanatory diagram showing the input/output characteristics of the switching regulator shown in Fig. 2. be. 6... Constant voltage circuit, 8... Resistor, 10... Constant voltage diode, 14... Switching transistor (first transistor), 16... DC regeneration circuit, 32... Control transistor (third transistor) ), 34... Constant voltage diode, 38...
Drive transistor (second transistor), 4
0...Capacitor (feedback circuit).

Claims (1)

[Claims for Utility Model Registration] (1) A first transistor that converts DC input into AC by switching, a constant voltage circuit that generates a constant voltage when the DC input is applied, and a base of the first transistor. a second transistor which is connected to the constant voltage circuit and whose base current is supplied together with the constant voltage to switch the first transistor; a feedback circuit that provides positive feedback through a capacitor to the base of the transistor to cause the second transistor to oscillate; a DC regeneration circuit that converts the AC obtained through the first transistor into a DC output; An operating current is supplied to the collector of a constant voltage diode that generates a reference voltage through the constant voltage circuit, and the reference voltage applied to the emitter is compared with the DC output applied to the base to determine the magnitude relationship between the two. The current according to the second
a third transistor drawing from the base of the transistor and controlling the base current of the first transistor through the second transistor. (2) The switching regulator according to claim 1, wherein the constant voltage circuit includes a series circuit including a resistor and a constant voltage diode connected to the DC input side.