JP2579069B2 - Output voltage remote control circuit of constant voltage power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a function circuit attached to a constant voltage power supply, and more particularly to an output voltage remote control circuit for changing the output voltage of the constant voltage power supply by a predetermined voltage value.

[0002]

2. Description of the Related Art Conventionally, as an output remote control circuit of a constant voltage power supply, an output voltage is divided by a resistor.
There is a type in which a series circuit of a resistor and a transistor is connected in parallel to each of the voltage dividing resistors. In this configuration,
Normally, the transistor is in the OFF state, and the output voltage value of the constant voltage power supply is kept constant. In this state, by turning on one of the two transistors, the voltage division ratio is changed, and the output voltage is changed by a predetermined voltage value.

[0003]

However, in the output voltage remote control circuit of the above-mentioned conventional constant voltage power supply device, since the transistor is directly turned on, the voltage division ratio changes stepwise. Therefore, as shown in FIG. 3, when the output voltage changes to a predetermined voltage value, overshoot or undershoot occurs due to delay in response of the constant voltage power supply.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an output voltage remote control circuit of a constant voltage power supply device which suppresses overshoot or undershoot of an output voltage and smoothes a voltage change. The purpose is to provide.

[0005]

In order to achieve the above object, an output voltage remote control circuit of a constant voltage power supply according to the present invention comprises a first resistor connected in series between an output terminal and a reference potential. In a constant voltage power supply device for comparing a voltage at a connection point with a second resistor with a reference voltage and stabilizing and controlling an output voltage by a control signal obtained by amplifying an error thereof, A series circuit of a third resistor and a first transistor connected in parallel at both ends;
A fourth resistor connected in parallel to both ends of the second resistor and a second resistor
And a series circuit with the transistor of (i), and forming an output voltage remote control circuit that changes an output voltage by a predetermined voltage value by turning on the first transistor or the second transistor ;
A fifth resistor connected between a collector and a base of the first transistor in the control circuit;
And a series circuit of a sixth resistor and a second capacitor connected between the collector and the base of the second transistor.

[0006]

According to the output voltage remote control circuit of the constant voltage power supply having the above configuration, a series circuit of a fifth resistor and a first capacitor connected between the collector and the base of the first transistor; Undershoot and overshoot of the output voltage are suppressed by the current mirror effect of the series circuit of the sixth resistor and the second capacitor connected between the collector and the base of the second transistor.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an output voltage remote control circuit according to an embodiment of the present invention together with a constant voltage power supply device.

The constant voltage power supply 1 compares the voltage at the connection point between the first resistor 5 and the second resistor 6 connected in series between the output terminal 52 and the reference potential with the reference voltage 4. An error amplifier 3 for amplifying the error and a converter circuit 2 for stabilizing and controlling the output voltage by a control signal obtained from the error amplifier 3 are provided.

The output voltage remote control circuit comprises a series circuit of a third resistor 7 connected in parallel to both ends of the first resistor 5 and a first transistor 10a in a photocoupler 10, And a series circuit of a fourth resistor 11 and a second transistor 14a of the photocoupler 14, which are connected in parallel to both ends of the resistor 6 of the first transistor 10a and the first transistor 10a or the second transistor 14a. By turning it on, the output voltage is changed by a predetermined voltage value.

The output voltage remote control circuit includes a series circuit of a fifth resistor 8 and a first capacitor 9 connected between a collector and a base of the first transistor 10a, and a second transistor connected to the second transistor. It has a series circuit of a sixth resistor 12 and a second capacitor 13 connected between the collector and the base of 14a.

Next, the operation of the constant voltage power supply will be described. The unstable voltage input via the input terminal 51 is converted to a predetermined stabilized DC output voltage V ₀ via the converter circuit 2 controlled by the level of the control signal level E output from the error amplifier 3. . Normally, the output voltage change instruction signal is not input to the output voltage decrease instruction input terminal 53 and the output voltage increase instruction input terminal 54. In this state, while the stabilized output voltage V ₀ is output via the output terminal 52, the resistance value is divided by the resistors ₅ and R6 of R ₅ and R ₆ , and is applied to one input terminal. , the reference voltage value V _R of the reference voltage 4 is output is input to the other terminal of the error amplifier 3 to be inputted. In the error amplifier 3, the divided value of the output voltage V ₀ by the resistors 5 and 6 (1)

(Equation 1) And the reference voltage V _R , the difference (2)

(Equation 2) And outputs a control signal level E obtained by amplifying the error voltage corresponding to. The converter circuit 2 corresponds to the control signal level E, and the respective input terminal voltages of the error amplifier 3, that is, the divided voltage value (1)

(Equation 3) A reference voltage V _R is operated to be equal. Therefore, the output voltage V ₀ is equal to the voltage (3)

(Equation 4) Is controlled to be stable.

Next, a case where an output voltage reduction instruction is input to the output voltage reduction instruction input terminal 53 will be described.

When an active low output voltage reduction instruction is input to the output voltage reduction instruction input terminal 53, a forward current flows from the control power supply 55 via the resistor 15 to the photodiode 10b in the photocoupler 10 with the base terminal. The phototransistor 10a shifts to the ON state. At this time, due to the current mirror effect of the resistor 8 and the capacitor 9 connected between the collector and the base of the phototransistor 10a, the resistance of the resistor 7 is set to R ₇ ,
_Assuming that the saturation voltage of _Oa is V _CE10 , the output voltage V ₀ is the voltage (3)

(Equation 5) To voltage (4)

(Equation 6) The undershoot does not occur as shown in FIG.

Next, a case where an output voltage increase instruction is input to the output voltage increase terminal 54 will be described.

The output voltage increase instruction input terminal
When a row output voltage increase instruction is input, a forward current flows from the control power supply 55 to the photodiode 14b in the photocoupler 14 with a base terminal via the resistor 15, and the phototransistor 14a shifts to the ON state. At this time, due to the current mirror effect of the resistor 12 and the capacitor 13 connected between the collector and the base of the phototransistor 14a, the resistance of the resistor 11 is set to R ₁₁ and the phototransistor 1 is turned on.
Assuming that the saturation voltage of 4a is V _CE14 , the output voltage is voltage (3)

(Equation 7) To voltage (5)

(Equation 8) , And no overshoot occurs as shown in FIG.

[0016]

As described above, according to the output voltage remote control circuit of the constant voltage power supply of the present invention, the output voltage is divided by the resistors, and each of the voltage dividing resistors is connected in series with a resistor and a transistor. Are connected in parallel, and when one of the two transistors is turned on to change the voltage division ratio and change the output voltage to a predetermined voltage value, a resistor connected between the collector and the base of the transistor The current mirror effect can be generated by the series circuit of the capacitor and the capacitor, so that the output voltage can be smoothly changed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an output voltage remote control circuit according to an embodiment of the present invention together with a constant voltage power supply device.

FIG. 2 is a graph showing an output voltage waveform at the time of output voltage remote control when the output voltage remote control circuit according to the embodiment of the present invention is used.

FIG. 3 is a graph showing an output voltage waveform at the time of output voltage remote control when a conventional output voltage remote control circuit is used.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 constant voltage power supply device 2 converter circuit 3 error amplifier 4 reference voltage 5 first resistor 6 second resistor 7 third resistor 8 fifth resistor 9 first capacitor 10 photocoupler 10a first transistor 10b Photodiode 11 Fourth resistor 12 Sixth resistor 13 Second capacitor 14 Photocoupler 14a Second transistor 14b Photodiode 51 Input terminal 52 Output terminal 53 Output voltage decrease instruction input terminal 54 Output voltage increase instruction input terminal 55 Control Power supply

Claims (1)

(57) [Claims] A voltage at a connection point between a first resistor and a second resistor connected in series between an output terminal and a reference potential is compared with a reference voltage, and an error thereof is amplified. A constant voltage power supply device for performing stabilization control of an output voltage by an obtained control signal, wherein a series circuit of a third resistor and a first transistor connected in parallel to both ends of the first resistor; A fourth resistor connected in parallel to both ends of the second resistor and a series circuit of a second transistor, and an output voltage obtained by turning on the first transistor or the second transistor; Is changed by a predetermined voltage value, and the first voltage in the output voltage remote control circuit is changed.
A series circuit of a fifth resistor and a first capacitor connected between the collector and the base of the second transistor; a sixth resistor and a second resistor connected between the collector and the base of the second transistor; An output voltage remote control circuit for a constant voltage power supply, comprising: a series circuit with a capacitor.