JPH0698535A - Dc stabilized power supply circuit - Google Patents

Abstract

PURPOSE:To reduce the number of components by simplifying the configuration of a DC stabilized power supply circuit. CONSTITUTION:The output voltage applied to a load 10 is detected as the middle-point voltage of two resistors 20 by a signal 100. An output voltage detection circuit 30 feeds an oscillation drive signal 106 to an oscillation circuit 32 when the potential indicated by the signal 100 is reduced. The oscillation operation of the oscillation circuit 32 is directly controlled by the oscillation drive signal 106 and an oscillation signal 104 is directly given to a switching transistor 18. When the switching transistor 18 performs switching operation, an output voltage is boosted. When the output voltage exceeds a certain voltage, oscillation stops and the operation of the switching transistor 18 also stops.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chopper type switching regulator for stabilizing a DC voltage by controlling switching of a switching transistor.

[0002]

2. Description of the Related Art Stabilization of a power supply is required to properly operate an electronic device. In particular, in an automobile or the like, the voltage itself between the terminals of the battery fluctuates, so it is important to stabilize the DC voltage supplied from the battery.

FIG. 4 shows a conventional DC stabilized power supply circuit (for example, see Japanese Patent Laid-Open No. 49-12347). This circuit provides a pulse width (PWM) controlled signal to a switching transistor to stabilize the voltage.

In FIG. 4, a choke coil 12 and a rectifying diode 14 are provided in the path to the load 10, and a smoothing capacitor 16 is provided in parallel with the load 10.

A switching transistor 18 is provided in parallel with the load 10 in order to stabilize the input voltage Vin and obtain an output voltage to the load 10.

In order to control the switching transistor 18, the voltage across the load 10 (output voltage) is detected as the midpoint voltage (divided voltage) of the two resistors 20 forming the output voltage detecting section. The detection signal 100 is input to one terminal of the differential amplifier 22 provided in the control circuit 21, and the other input terminal of the differential amplifier 22 is supplied with the reference voltage from the reference power supply 24.

Then, the output signal 102 of the differential amplifier 22.
Is input to one terminal of the comparator 26, and the oscillation signal from the oscillator 28 that generates a triangular wave is input to the other terminal of the comparator 26.

When the load voltage (output voltage) drops, the level of the output signal 102 of the differential amplifier 22 drops, and the pulse width of the oscillation signal 104, which is the differential output of the comparator 26, widens to the base terminal of the switching transistor 18. Supplied. As a result, the output voltage is boosted by the action of the choke coil 12 and the like. On the other hand, when the output voltage rises above a certain value, the level of the output signal 102 from the differential amplifier 22 rises, and the oscillation signal 104 from the next comparator 26 to the switching transistor 18
Pulse width is narrowed. As a result, the boosting action is reduced and the output voltage is stabilized.

[0009]

However, the above-mentioned conventional DC stabilized power supply circuit has a problem that the circuit configuration becomes complicated. That is, in the above circuit, it is necessary to provide the reference voltage source, the differential amplifier, the comparator, etc. independently, and the circuit scale of the control unit becomes large and complicated.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a stabilized DC power supply circuit capable of stabilizing an output voltage with a simple circuit configuration.

[0011]

In order to achieve the above object, the present invention provides a DC stabilized power supply circuit for stabilizing a DC voltage applied to a load by controlling switching of a switching transistor. And a circuit for outputting a periodic on / off signal to the switching transistor, the output voltage detecting circuit detecting the generated voltage and outputting an oscillation drive signal when the voltage fluctuates from a reference value. And an oscillating circuit whose oscillating operation is directly controlled by.

[0012]

According to the above configuration, the oscillation drive signal is directly output from the output voltage detection circuit to the oscillation circuit to directly control the oscillation, and the oscillation signal from the oscillation circuit is supplied to the switching transistor and switched. Voltage control is executed. Therefore, it is not necessary to provide a plurality of comparators, reference voltage sources, etc. as in the conventional case.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the basic structure of a stabilized DC power supply circuit according to the present invention. First, the basic configuration will be described, and then the specific configuration will be described with reference to FIGS. 2 and 3. In each drawing, the same components as those shown in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, the control unit 21 comprises an output voltage detection circuit 30 and an oscillation circuit 32.

Here, the detection signal 100 extracted from the midpoint of the two resistors 20 connected in series for detecting the output voltage is input to the output voltage detection circuit 30.
The output voltage detection circuit 30 sends the oscillation drive signal 106 to the oscillation circuit 32 when the output voltage falls below a certain value.
Is output. The oscillation drive signal 106 is generated by the oscillation circuit 32.
The oscillation drive signal 1
When 06 is obtained, the oscillation circuit 32 starts oscillation and the oscillation signal 104 is directly supplied to the base terminal of the switching transistor 18. As a result, the chopper control is executed and the output voltage is boosted.

On the other hand, when the output voltage rises above a certain value, the oscillation drive signal 106 is no longer output and the output of the oscillation signal 104 is also stopped. This also stops the switching operation of the switching transistor 18. The output voltage is stabilized by performing such feedback control.

As described above, in the present invention, the rise and fall of the output voltage is detected by the output voltage detection circuit 30, and the oscillation drive signal 106, which is the output signal, directly controls the oscillation operation. Is directly supplied to the switching transistor to simplify the circuit.

Next, a specific structure will be described below. FIG. 2 shows the configuration of the first embodiment.

2, the control unit 21 includes a transistor 40 corresponding to the output voltage detection circuit 30 of FIG.
Astable multivibrator 4 corresponding to the oscillation circuit 28 of
2, a so-called step-up type switching regulator is configured. Here, the astable multivibrator 42 has a known circuit configuration including the transistors 42a and 42b, and continuously generates pulses according to a time constant determined by a resistor and a capacitor.

Here, the detection signal 100 is supplied to the base terminal of the transistor 40. When the voltage of the signal 100 drops, the collector current of the transistor 40 is stopped (in other words, the oscillation drive signal is generated), the base terminal of the transistor 42a of the astable multivibrator 42 becomes "Hi", and the oscillation operation starts. To be done. As a result, the switching transistor 18 performs a switching operation and the output voltage is boosted.

On the other hand, when the detection voltage of the signal 100 rises, the collector current of the transistor 40 flows, the base terminal of the transistor 42a of the astable multivibrator 42 becomes "Lo", and the base potential is forced to "L".
It is clamped to "o" and the oscillation operation stops. As a result, the switching operation of the switching transistor 18 is stopped and the boosting action is stopped.

It should be noted that it is necessary to determine the potential at the midpoint thereof to be about 0.7 V by the resistance ratio of the two resistors 20 at the proper output voltage. That is, it is necessary to set the resistance ratio of the two resistors 20 so that the appropriate potential at the midpoint matches the base-emitter potential difference of the transistor 40.

A second embodiment is shown in FIG. In FIG. 3, the control unit 21 includes two transistors 44 and 46 that form the output voltage detection circuit 30 and a monostable multivibrator 48 that is an oscillation circuit, and forms a so-called step-up switching regulator. .

Here, the monostable multivibrator 48
Has a known circuit configuration, and includes two transistors 48a and 48b that perform an oscillating action and a trigger transistor 48.
c and are included.

The detection signal 100 indicating the output voltage is supplied to the base terminal of the transistor 44 of the output voltage detection circuit 30. When the output voltage drops and the transistor 44 receiving the signal 100 stops operating, the collector current of the transistor 44 stops and the base potential of the transistor 46 rises (occurrence of an oscillation drive signal). Then,
The collector current of the transistor 46 flows, and the monostable multivibrator 48 outputs a pulse to the switching transistor 18.

However, the monostable multivibrator 48
Does not generate a continuous pulse unless a trigger signal is applied.

Therefore, a trigger transistor 48c is provided on the emitter side of the switching transistor 18 via a resistor. That is, when the switching transistor 18 operates, the potential on the emitter side thereof fluctuates, so that it is fed back and used as a trigger signal. Trigger pulses are intermittently generated in the monostable multivibrator 48 by the transistor 48c, so that the monostable multivibrator 48 eventually performs a continuous oscillation operation, and the output voltage rises.

On the other hand, when the output voltage is boosted above a certain value, the transistor 44 is turned on by the signal 100,
In conjunction with this, the transistor 46 is turned off. This completes the transistor 4 of the monostable multivibrator 48.
The oscillation is stopped because the base potential of 8 is forcibly clamped. Of course, no trigger pulse is generated by the transistor 48c. As a result, the boosting action of the output voltage is stopped. Also in this second embodiment, the two resistors 2
Depending on the resistance ratio of 0, the proper potential at the midpoint is about 0.7V
It is necessary to determine that That is, it is necessary to set the resistance ratio of the two resistors 20 so that the appropriate potential at the midpoint matches the potential difference between the base and the emitter of the transistor 40.

It should be noted that the potential serving as a comparison reference for the output voltage can be freely set by cascading a plurality of transistors.

In the above embodiment, the switching transistor 18 is inserted in parallel with the load 10. However, the present invention can be applied to a type in which the switching transistor 18 is inserted in series.

According to each of the above embodiments, the oscillation drive signal is generated by operating the output voltage detecting transistor by utilizing the potential difference between the base and the emitter of the transistor, and the oscillation drive signal is directly output from the oscillation circuit. Since the operation is controlled, the circuit configuration of the DC stabilized power supply circuit can be simplified, and in particular, the number of parts can be significantly reduced, so that the cost of the circuit can be reduced.

[0033]

As described above, according to the present invention,
The oscillation circuit is controlled by the oscillation drive signal output from the output voltage detection circuit, and the output signal from the oscillation circuit is directly applied to the switching transistor, so that the circuit configuration can be simplified. It is possible to reduce the number of points and reduce the cost of the circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic configuration of a stabilized DC power supply circuit according to the present invention.

FIG. 2 is a circuit diagram showing a first embodiment of a stabilized DC power supply circuit according to the present invention.

FIG. 3 is a circuit diagram showing a second embodiment of a stabilized DC power supply circuit according to the present invention.

FIG. 4 is a circuit diagram of a conventional DC stabilized power supply circuit.

[Explanation of symbols]

 10 load 18 switching transistor 21 control unit 30 output voltage detection circuit 32 oscillation circuit 100 detection signal 104 oscillation signal

Claims (1)

[Claims] 1. A DC stabilized power supply circuit for stabilizing a DC voltage applied to a load by controlling switching of a switching transistor, wherein the voltage applied to the load is detected, and the voltage fluctuates from a reference value. An output voltage detection circuit that outputs an oscillation drive signal to the switching circuit, and a circuit that outputs a periodic on / off signal to the switching transistor, the oscillation circuit having its oscillation operation directly controlled by the oscillation drive signal. And a stabilized direct current power supply circuit, wherein the output of the oscillation circuit is directly supplied to the switching transistor.