JPH07303370A - Switching regulator - Google Patents

Abstract

PURPOSE:To suppress the power loss of a switching regulator to a low level by controlling the regulator to turn off a second transistor when a first transistor is turned on and turn on the second transistor when the first transistor is turned off. CONSTITUTION:In a switching regulator, the emitter E and collector C of a transistor 20 and a resistor 21 are connected between the emitter E and base B of a transistor 2 and the base B of the transistor 2 is grounded through the collector C and emitter E of a transistor 23. In addition, the base B of the transistor 23 is grounded through a resistor 25 and also connected to the collector C of a transistor 8 through a resistor 24. As a result, the voltage across the collector C and emitter E of a first transistor is suppressed to a low level and the power loss of the switching regulator is reduced when the first transistor is turned on, because a sufficiently large base current flows and turns on the transistor. When the first transistor is turned off, the power loss of the switching regulator is also reduced, because the transistor is turned off in a short carrier storing time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator used in a power supply circuit such as a mobile phone and a charger.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a configuration example of a conventional switching regulator. As shown in the figure, the conventional switching regulator has an input terminal 1, a transistor 2, a diode 3, a coil 4, a capacitor 5, an output terminal 6, a resistor 7, a transistor 8, a PWM (pulse width modulation) controller 9, Comparator 10, reference power supply 11, resistor 12, resistor 1
3 and resistor 14.

A DC power source from a battery is connected to an input terminal 1, a DC current from the DC power source is interrupted by turning on / off a transistor 2, and a smoothing circuit composed of a diode 3, a coil 4 and a capacitor 5 and , Is connected to the load through the output terminal 6. The output voltage Vo is divided by the resistors 12 and 13 and compared with the reference power source 11 by the comparator 10, and the error voltage is input to the PWM controller 9. PWM
The output signal of the controller 9 controls the on / off of the transistor 8, and the on / off interval of the transistor 2, that is, the pulse width is controlled by the on / off of the transistor 8 to control the output voltage Vo to be constant. -Dubbing control is performed.

FIG. 4 is a diagram showing voltage and current of a switching element of a conventional switching regulator. As shown in the figure, the PWM controller 9 controls the pulse width t of the transistor 2 which is a switching element to control the output voltage Vo output through the smoothing circuit.

[0005]

However, in the conventional switching regulator, when the value of the resistor 14 connected between the emitter E and the base B of the transistor 2 which is a switching element is large, a in FIG. As shown in (3), the carrier accumulation time becomes long when the transistor 2 is turned off, and the power loss during this time increases.

When the value of the resistor 14 is reduced to shorten the carrier storage time, the voltage of the base B is increased and the base current is decreased, so that the transistor 2 is turned on as shown in FIG. 4b. In this state, there is a problem that the voltage V _CE between the collector and the emitter increases and the power loss also increases. When the power loss becomes large, the battery usage time becomes short, which is a serious problem especially in mobile phones.

The present invention has been made in view of the above points, and an object of the present invention is to provide a switching regulator in which the above problems are eliminated and the power loss of a switching element is suppressed to a low level.

[0008]

In order to solve the above-mentioned problems, the present invention comprises a first transistor as a switching element, which is input to an emitter by controlling the on / off interval of the first transistor. In a switching regulator for controlling a DC output voltage by controlling an intermittent interval of a DC current output from a collector, a second transistor is provided between an emitter of a first transistor 2 and a base as shown in FIG. The emitter and the collector of 20 are connected, and the second transistor 20 is turned off when the first transistor 2 is turned on, and the second transistor 20 is turned on when the first transistor 2 is turned off. It is characterized by

[0009]

According to the present invention, when the transistor 2 of the switching element is turned on as described above, the transistor 20 is turned off, and the base current of the transistor 2 flows sufficiently to be turned on, so that the collector C and the emitter E are connected. The voltage V _CE is kept low and the power loss is reduced. Further, when the transistor 2 of the switching element is turned off, the transistor 20
Is turned on, the carrier storage time is short and the turn-off is performed, so that the power loss during this time is also reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a switching regulator of the present invention. As shown in the figure, the switching regulator of the present invention comprises an input terminal 1, a transistor 2,
Diode 3, coil 4, capacitor 5, output terminal 6,
Resistor 7, transistor 8, PWM controller 9, comparator 1
0, reference power supply 11, resistor 12, resistor 13, transistor 20, resistor 21, resistor 22, transistor 2
3, resistor 24, resistor 25.

Portions having the same numbers as those in FIG. 3 perform the same functions as those in FIG. 3, and the description of the feedback control is omitted (see the prior art).

The emitter E and the collector C of the transistor 20 are connected between the emitter E and the base B of the transistor 2. A resistor 21 is connected between the emitter E of the transistor 20 and the base B, and the base B is grounded via the collector C-emitter E of the transistor 23. The base B of the transistor 23 is grounded through the resistor 25, and further connected to the collector C of the transistor 8 through the resistor 24.

The switching regulator of the present invention is based on the emitter E of the transistor 2 which is a switching element and a base.
The loss due to the switching of the transistor 2 is reduced by connecting and controlling the transistor 20 between the switches B.

When the PWM controller 9 turns on the transistor 8, the base current of the transistor 23 does not flow, the transistors 23 and 20 are both turned off, and the base current of the transistor 2 sufficiently flows to be turned on. The voltage V _CE between C and the emitter E is kept low.

When the PWM controller 9 turns off the transistor 8, the base current of the transistor 23 flows and both the transistor 23 and the transistor 20 are turned on. In the transistor 2, the transistor 20 is on between the emitter E and the base B. The carrier accumulation time is short and the turn-off is performed.

As described above, the voltage and current of the switching element (transistor 2) of the switching regulator of the present invention are as shown in FIG. 2, and the voltage V between the collector C and the emitter E of the transistor 2 is ON even in the ON state. _CE is suppressed to a low level, power loss is reduced, and the carrier storage time is shortened even during turn-off to reduce power loss.

[0017]

As described in detail above, according to the present invention, the following excellent effects are expected. (1) When the first transistor, which is a switching element, is turned on, the base current of the transistor sufficiently flows to be turned on, so that the voltage V _CE between the collector C and the emitter E is kept low and the power loss is reduced. When the first transistor is turned off, the carrier accumulation time is short and it is turned off, so that the power loss during this period is also reduced. (2) When the switching regulator of the present invention is used in a mobile phone, the battery usage time is extended.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a switching regulator of the present invention.

FIG. 2 is a diagram showing voltage and current of a switching element of the switching regulator of the present invention.

FIG. 3 is a diagram showing a configuration example of a conventional switching regulator.

FIG. 4 is a diagram showing a voltage and a current of a switching element of a conventional switching regulator.

[Explanation of symbols]

 1 Input Terminal 2 Transistor 3 Diode 4 Coil 5 Capacitor 6 Output Terminal 7 Resistor 8 Transistor 9 PWM Controller 10 Comparator 11 Reference Power Supply 12 Resistor 13 Resistor 14 Resistor 20 Transistor 21 Resistor 22 Resistor 23 Transistor 23 Transistor 24 resistors 25 resistors

Claims (1)

[Claims] 1. A first transistor is provided as a switching element, and an on / off interval of the first transistor is controlled to control an intermittent interval of a direct current input to an emitter and output from a collector. In a switching regulator for controlling a DC output voltage, an emitter and a collector of a second transistor are connected between an emitter and a base of the first transistor, and a second transistor is turned on when the first transistor is turned on. A switching regulator in which a transistor is turned off and a second transistor is turned on when turning off the first transistor.