JPH01116712A - Stabilizing power source circuit - Google Patents

Abstract

PURPOSE:To surely prevent the malfunction of equipment with a simple constitution when an input power source is erroneously switched by constituting the title circuit so as to control a reference voltage circuit with a voltage detecting element, and setting the output voltage at an extremely small value or at 0 when the input voltage is at a prescribed value or below. CONSTITUTION:A voltage detecting element 8 to detect the input voltage is provided, the circuit is constituted so that the voltage detecting element 8 may control a reference voltage circuit 3, and when the input voltage is at the prescribed value or below, the output voltage is set at the extremely small value or at 0, and its malfunction is prevented. That is, when the input voltage is lowered to a degree, which cannot be coped with, by an amplification in a stabilizing power source circuit, since the voltage detecting element 8 controls the reference voltage circuit 3, and the output voltage is set at 0 or the extremely small value, the load connected to the stabilizing power source circuit can be prevented from malfunction at the low voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stabilized power supply circuit suitable for use in a VTR capable of switching the human power supply voltage between 120V and 220V, for example.

[Summary of the invention]

The present invention provides a stabilized power supply circuit suitable for use in a VTR capable of switching the input power supply voltage between 120V and 220V, for example, in which a voltage detection element for detecting the input voltage is provided, and the voltage detection element uses the reference voltage By configuring the circuit to control the circuit and making the output voltage extremely small or zero to prevent malfunctions when the input voltage falls below a predetermined value, it is possible to switch the input power supply voltage with a simple configuration. This is to reliably prevent equipment malfunctions if a mistake is made.

[Conventional technology]

Conventionally, as a stabilized power supply circuit used in a video tape recorder (hereinafter referred to as VT1), etc., there has been a stabilized power supply circuit as shown in FIG. In I, (1) indicates an input terminal to which low-voltage DC power obtained by transforming and rectifying a commercial AC power supply is supplied, and the DC power obtained at this input terminal (1) is connected to an amplifier (2) and a reference voltage. Supplied to circuit (3).

Then, the reference voltage circuit (3) creates a reference voltage signal with a constant voltage value at a lower voltage than the power supply voltage supplied from the terminal (1), and sends this reference voltage signal from the reference voltage circuit (3) to the error detection circuit. This error detection circuit (4) detects the voltage difference between this reference voltage signal and a divided voltage signal supplied from a voltage divider (5), which will be described later, and sends the detected signal to the amplifier (2). ).

The amplifier (2) amplifies the DC power supplied from the terminal +11 with an amplification factor based on the detection signal supplied from the error detection circuit (4), and converts the DC voltage amplified by the amplifier (2) into It is supplied to an output terminal (6) connected to a load (7) and also to a voltage divider (5). The voltage divider (5) divides the DC voltage amplified by the amplifier (2) at a predetermined ratio and supplies the divided voltage to the error detection circuit (4).

With this configuration, even if there is a fluctuation in the voltage value of the DC power source obtained at the input terminal (1), the amplifier (
In order to compare the voltage value obtained by dividing the DC voltage output by 2) with the reference voltage output by the reference voltage circuit (3), and change the amplification factor in the amplifier (2) according to the compared voltage difference. , the variation in the voltage value is canceled out by this change in amplification degree in the amplifier (2). Therefore, a stable DC voltage with a constant voltage value is output from the output terminal (6), and a constant DC voltage is supplied to the load (7).

By the way, as a device that uses this type of stabilized power supply circuit, there is a device that can manually operate a commercial AC power source with multiple voltages. For example, in countries where the commercial AC power supply is 120V (
one V in the home country, etc.) and a 220v country (Europe, etc.)
There is one in which TR can be used in common. In this case, the voltage value of the DC power supplied to the input terminal (1) of the stabilized power supply circuit can be changed by using a changeover switch to change the transformation ratio of the transformer that transforms the AC power supply. It was made to be the same regardless of the voltage value of the commercial AC power supply.

[Problem that the invention seeks to solve]

However, with this type of equipment where the input commercial AC power source is switched, if the selection of the input commercial AC power source with the changeover switch is incorrect, the equipment may malfunction.
With V'I'R, which can switch between 120v and 220v as an input commercial AC power source, turn the selector switch to 22v.
If you use it in a country with a power supply voltage of 120V while leaving it on the 0V side,
The DC voltage obtained at the input terminal (1) of the stabilized power supply circuit becomes approximately half of the current voltage value, which exceeds the amount of variation in voltage value that this stabilized power supply circuit can handle. In other words, if the DC voltage obtained at the input terminal (1) significantly decreases, the reference voltage circuit (3) will no longer be able to create a predetermined reference voltage signal, and the voltage from the output terminal (6) will be significantly lower than normal. A low DC voltage will be output.

When the DC voltage supplied to the load (7) decreases significantly in this way, in the case of a VTR, each motor in the tape running system, such as the capstan motor, rotates differently than usual (low speed, low torque). There was a risk that the videotape would be damaged due to incomplete running of the videotape.

In view of the above, an object of the present invention is to provide a stabilized power supply circuit that can reliably prevent equipment from malfunctioning when the input power supply voltage differs significantly from a set value.

[Means for solving problems]

The stabilized power supply circuit of the present invention is, for example, as shown in FIG.
A voltage detection element (8) for detecting the input voltage is provided, and the voltage detection element (8) is configured to control the reference voltage circuit (3), and when the input voltage becomes less than a predetermined value, the output voltage is adjusted. This is made extremely small or zero to prevent malfunctions.

[Effect]

According to the stabilized power supply circuit of the present invention, when the input voltage drops to a level that cannot be handled by amplification in the stabilized power supply circuit, the voltage detection element (8) controls the reference voltage signal scale to reduce the output voltage to zero. Alternatively, since it becomes smaller in size, the load connected to this stabilized power supply circuit is prevented from malfunctioning at low voltage.

〔Example〕

An embodiment of the stabilized power supply circuit of the present invention will be described below with reference to FIGS.
Let's explain with reference to FIG. In FIGS. 1 to 3, parts corresponding to those in FIG. 4 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

As shown in Fig. 1, the stabilized power supply circuit of this example transforms and rectifies a commercial AC power supply to obtain a low-voltage DC power supply at an input terminal (1). We will supply it to you. This voltage detection element (8) has an input terminal (1
), when it is detected that the voltage value of the DC power source obtained at ! Positive reference voltage circuit (3)
When it is detected that the voltage value of the DC power source obtained at the input terminal +11 is less than a predetermined value, the DC voltage is not supplied to the reference voltage circuit (3).

The reference voltage circuit (3) creates a reference voltage signal having a constant voltage value based on the DC voltage output by the voltage detection element (8), and supplies this reference voltage signal to the error detection circuit (4). The error detection circuit (4) compares the reference voltage signal with the voltage signal output from the voltage divider (5) and supplies a detection signal to the amplifier (2). And in the amplifier (2),
The DC power supply supplied from the terminal (1) is amplified with an amplification factor based on this detection signal, and the output voltage of this amplifier (2) is supplied to the load (7) via the output terminal (6).

The other parts of the stabilized power supply circuit of this example are constructed in the same manner as the stabilized power supply circuit of the example shown in FIG. 4 as a conventional example.

Next, to explain the operation of the stabilized power supply circuit of this example, when the DC voltage obtained at the input terminal (1) is within the range that can be stabilized by this stabilized power supply circuit,
The DC voltage output by the voltage detection element (8) is supplied to the reference voltage circuit (3), and based on this DC voltage, the reference voltage circuit (
3) creates a reference voltage signal.

When the reference voltage circuit (13) creates this reference voltage signal, the error detection circuit (4) uses this reference voltage signal and the voltage divider (5).
) is detected, and the detected signal is supplied to the amplifier (2). Then, the amplifier (2) amplifies the DC voltage obtained at the input terminal (1) with an amplification factor according to this detection signal, outputs a constant DC voltage from the output terminal (6), and outputs the DC voltage with a constant voltage value from the output terminal (6). ).

Then, when the DC voltage obtained at the input terminal (1) becomes lower than the range that can be stabilized by this stabilized power supply circuit, the voltage detection element (8) stops outputting the DC voltage, and the reference voltage Generation of the reference voltage signal in circuit (3) is stopped. Therefore, the error detection circuit (4) no longer performs error detection, the amplifier (2) stops signal amplification, and the supply of DC power obtained from the input terminal (11) to the output terminal (6) is blocked. As a result, DC power is no longer supplied to the load (7).

In this way, according to the stabilized power supply circuit of this example, the input terminal (
When the voltage value of the DC voltage obtained in step 1) is within the range that can be stabilized by this stabilized power supply circuit, a DC voltage with a constant voltage value is output from the output terminal (6) and the load (
7) operates stably and well.

When the voltage value of the DC voltage obtained at the input terminal (1) becomes lower than the range in which it can be stabilized, almost no DC voltage is output from the output terminal (6).
The load (7) will not operate at all. Figure 3 is a diagram showing the relationship between the power supply voltage supplied to this input terminal (11) and the DC voltage output from the output terminal (6), and shows the lowest input voltage that can be stabilized by this stabilized power supply circuit. If the value is vl, and the voltage value output when stable is Vo, as shown by the solid line, when the input voltage value is 1 or more, the output voltage is stabilized at VQ, but when the input voltage value is 1 or less, The output voltage value rapidly decreases from Vo and approaches zero.On the other hand, in the conventional circuit, as shown by the broken line, when the input terminal value v1 or less, a DC voltage proportional to the input voltage value is output.

In this way, as long as a constant value of DC power can be supplied to the load (7), this DC power can be stably supplied.
If the setting of the input commercial AC power supply is incorrect, the voltage value of the DC voltage supplied to each motor in the tape running system, which is a load, will be extremely small or zero, and each motor in this tape running system will It does not rotate, does not damage the video tape, and protects the video tape.
The setting in TR is 120■, and the actual human power supply is 220
If the input becomes excessive in (2), the protection circuit connected to negative 4't1 (7) blocks the supply of power.

Next, an example of a specific circuit of the stabilized power supply circuit of this example will be explained in the second section.
Let me explain with reference to the diagram. In this example, the input terminal (
11 is an npn type transistor Tr1 constituting an amplifier;
The emitter of this transistor Tt1 is connected to the output terminal (6). Then input terminal (1
) is connected to the cathode of a Zener diode ZDL, which is a voltage detection element, via a resistor RL, and the anode of this Zener diode Z1) is connected to the cathode of a Zener diode ZD2, which constitutes a reference voltage circuit.
The anode of this Zener diode ZD2 is grounded.

Further, the anode of the Zener diode ZDz is grounded via a resistor R2 having a relatively high resistance value.

The base of the transistor Trx is connected to the collector of a pnp transistor Ttz constituting the error detection circuit, and the emitter of the transistor Tr2 is connected to the cathode of the Zener diode ZD2.

Further, the collector and base of the transistor Trz are connected via a resistor R3. And the transistor T'r
The emitter of t is grounded through a series circuit of resistor R4 and resistor R5 that constitute a voltage divider, and resistor a R41R6
The midpoint of the connection is connected to the base of the transistor Trz.

In addition, the emitter of the transistor Tr1 is connected to the capacitor C
1 to ground.

By configuring the stabilized power supply circuit in this way, the potential on the cathode side of the Zener diode ZD2 becomes a constant voltage value based on the Zener voltage of the Zener diode ZD2. Therefore, the transistor Tr2 is turned on and off by the difference between the voltage divided by the resistors R4 and R5 and the cathode potential of the Zener diode ZD2, and the transistor Tr2 amplifies the DC power supply. power supply is stabilized.

Since there is a Zener diode zD1, the potential on the cathode side of this diode ZD2 and the input terminal (1)
When the potential difference between the Zener diode ZD2 and the potential of
rz is turned off, and the DC power obtained at the input terminal (1) flows to the ground side via the resistor R3 and the resistor R2, and is no longer supplied to the output terminal (6) side.

In this way, when the voltage value of the DC power source obtained at the input terminal (1) is a value that cannot be stabilized by simply connecting the Zener diode ZD1, which is a voltage detection element,
Supply to the output terminal (6) is blocked.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be taken without going over the gist of the present invention.

〔Effect of the invention〕

According to the stabilized power supply circuit of the present invention, the supply of power to the load side is blocked when the input power supply voltage is significantly different from the set value and cannot be stabilized, with a simple configuration of just connecting a voltage detection element. There is the benefit of being able to prevent equipment malfunctions.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the stabilized power supply circuit of the present invention, FIG. 2 is a circuit diagram showing a specific example of the example in FIG. 1, and FIG. 3 is a diagram for explaining the example in FIG. 1. , FIG. 4 is a configuration diagram showing an example of a conventional stabilized power supply circuit. (1) is an input terminal, (3) is a reference voltage circuit, and (8) is a voltage detection element. Figure 1 Figure 2

Claims (1)

[Claims] A voltage detection element for detecting an input voltage is provided, and the voltage detection element is configured to control a reference voltage circuit, and when the input voltage falls below a predetermined value, the output voltage is made extremely small or becomes zero and malfunctions. A stabilized power supply circuit characterized in that it is designed to prevent.