JPH09289769A - Dc/dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lengthen available period and attain continuous required voltage by incorporating a DC/DC down-converter and a DC/DC up-converter into a DC/DC converter. SOLUTION: This converter is constituted of a voltage switching circuit 12 which compares DC input voltage with reference voltage and outputs voltage divided by the reference voltage into separate terminals, a DC/DC down- converter 16 which drops input in excess of the reference voltage from the voltage switching circuit 12 to required voltage, a constant voltage circuit 13 which drops the input which is the reference voltage or lower to the required voltage, a DC/DC up-converter 14 which is connected to the output circuit of the constant voltage circuit 13 and increases voltage to the required voltage when the input drops lower than the required voltage and passes the input in the other cases, and an output circuit which provides the outputs of the DC/DC down-converter 16 and the DC/DC up-converter 14 through a reverse current flow preventive diode 15 or 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC / DC converter suitable for use in a DC power supply device that uses electricity generated by a solar cell as a power source.

[0002]

2. Description of the Related Art Conventionally, solar cells are used to convert sunlight into electricity, the converted electricity is used to charge a storage battery, for example, an electric double layer battery, and the voltage of the charged electric double layer battery is used as a power source. A DC power supply device is configured by using it, and the equivalent circuit of the electric double layer battery can be regarded as a capacitor having a value of hundreds of farads, and its output voltage changes with the passage of time as shown in FIG. The voltage characteristic (E) is decreasing. Charge the secondary battery with the voltage stored in the electric double layer battery or the electric double layer battery,
Using the voltage charged in this secondary battery as the output voltage,
The output voltage is changed to a required voltage Vou by a DC / DC converter.
It was converted to t and supplied to the equipment as a power source.

When a DC / DC down converter is used as the DC / DC converter, it can be used only as a power source until the voltage characteristic (E) of the DC power source drops to the required voltage Vout, so that there is a problem that the operating time is short. there were. In order to extend the usable period, the DC / DC down converter and the DC / DC up converter are set to DC.
When incorporated in a DC / DC converter, the operating range of the DC / DC down converter and the operating range of the DC / DC up converter become discontinuous as shown in FIG.
There is a problem that a continuous output voltage (Vo) cannot be obtained from the / DC converter.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above problems, and is directed to a DC power supply having a voltage characteristic that drops with the passage of time when a solar cell or the like is used as a power supply. D to DC / DC converter
By incorporating a C / DC down converter, a DC / DC up converter, etc., the usable period is extended and a continuous required voltage is obtained.

[0005]

The DC power supply device of the first invention of the present application compares a DC input voltage having a voltage characteristic that drops with the lapse of use time with a reference voltage, and when it exceeds the reference voltage. A voltage switching circuit that outputs the DC input voltage to the first output terminal when the voltage is below the reference voltage, and a DC / DC down circuit that drops the input from the first output terminal to a required voltage. A converter and the second
Connected to the constant voltage circuit that outputs the input from the output terminal of the voltage drop to the required voltage and the output circuit of this constant voltage circuit,
When the input voltage drops below the required voltage, the voltage is boosted to the required voltage, and at other times, the input voltage is passed and output D
It comprises a C / DC up-converter, and an output circuit for connecting the output sides of the DC / DC down-converter and the DC / DC up-converter to each other to output a required voltage.

In the DC power supply device according to the second invention of the present application, the voltage switching circuit compares the DC input voltage with a reference voltage, and when the voltage exceeds the reference voltage, one output terminal, and when the voltage is less than the reference voltage, A voltage comparator that outputs a control signal to the other output terminal, and a DC input voltage that is input to each of them, and a DC input voltage that exceeds the reference voltage is output by the control signal that is input from the one output terminal. And a second switch circuit that outputs a DC input voltage equal to or lower than a reference voltage according to a control signal input from the other output terminal. In the direct-current power supply device of the third invention of the present application, the output circuit is formed by connecting the outputs of the DC / DC down converter and the DC / DC up converter via backflow prevention diodes.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the invention of the present application, a voltage switching circuit compares a DC input voltage with a reference voltage, and outputs one output terminal when the voltage exceeds the reference voltage and the other output when the voltage is less than the reference voltage. A voltage comparison unit that outputs a control signal to the terminal,
A first switch circuit that inputs a DC input voltage to each and outputs a DC input voltage exceeding a reference voltage in accordance with a control signal that is input from the one output terminal, and a control input from the other output terminal A second switch circuit that outputs a DC input voltage that is lower than the reference voltage by a signal, and a DC input voltage that has a voltage characteristic that drops with the passage of use time
DC down converter drops to the required voltage and outputs,
Inputs below the reference voltage are output by dropping them to the required voltage with a constant voltage circuit.

A DC / DC up-converter is connected to the output circuit of the constant voltage circuit. In the DC / DC up-converter, when the input voltage drops below the required voltage, the voltage is boosted to the required voltage, and at other times, the input voltage is increased. Pass and output. The output sides of the DC / DC down converter and the DC / DC up converter are connected to each other to output a required voltage, and the control range of the DC / DC down converter and the control range of the DC / DC up converter are connected. The constant voltage circuit is operated so that a continuous required voltage can be output. Therefore, it is possible to lengthen the output period of the required voltage and obtain a continuous required voltage.

[0009]

1 is a block diagram showing an embodiment of a DC power supply device of the present invention, and FIG. 2 is an explanatory diagram of output voltage characteristics of the DC power supply device of the present invention. Examples will be described below with reference to FIGS. 1 and 2. First, the DC power supply unit 3
0 will be described. A plurality of solar cells, for example, the negative sides of the solar cells 1 and 3 are commonly connected to the common electrode side of the output terminal 10, and the positive sides are connected to the three-terminal regulator 5 via the backflow preventing diodes 2 and 4, respectively. 3 terminal regulator 5 connects capacitors 6 and 7 between the input / output circuit and the common electrode,
Solar cells 1 and 3 convert sunlight into electricity, and the converted electricity is output as a predetermined DC voltage stabilized by a circuit including a three-terminal regulator 5 and capacitors 6 and 7.

The DC output voltage from the three-terminal regulator 5 is passed through the diode 8 for preventing backflow and the electric double layer battery 9 is supplied.
Of the electric double layer battery 9 and the other end of the electric double layer battery 9 are connected to the common electrode.
Is charged by the DC output voltage from the three-terminal regulator 5, and outputs a predetermined output voltage E to the output terminal 1 of the DC power supply unit 30.
Output to 0. The equivalent circuit of an electric double layer battery can be regarded as a capacitor having a value of several hundreds of farads, and its output voltage has a voltage characteristic (E) that drops with the lapse of usage time as shown in FIG.

Next, the DC / DC converter 31 will be described. FIG. 3 is a block diagram showing an embodiment of the voltage switching circuit 12 of FIG.
And a reference voltage VS are compared with each other, and a voltage comparison section 25 that separately outputs two control signals when the reference voltage VS is exceeded and when the reference voltage VS is less than or equal to the reference voltage VS, and the DC input voltage E are input to each of them. A switch circuit 27 that outputs a DC input voltage E exceeding the reference voltage VS by one control signal from the voltage comparison unit 25, and a reference voltage VS by the other control signal.
The switch circuit 26 outputs the following DC input voltage E, and the DC input voltage E having a voltage characteristic that drops with the lapse of usage time is divided into 2 according to the voltage level and output.

In the figure, the voltage comparison section 25 is constructed by using, for example, a comparator circuit, and the switch circuits 26 and 27 are constructed by using, for example, transistors.
As the DC / DC down converter 16, for example, a commercially available IC configured by a chopper type circuit is used, and as shown in FIG. 2, an input exceeding the reference voltage VS from the switch circuit 27 of the voltage switching circuit 12 is supplied with a required voltage Vo. Step down and output. The constant voltage circuit 13 uses, for example, a three-terminal regulator, steps down the input of the reference voltage VS or less from the switch circuit 26 to a required voltage Vo, outputs it, and inputs it to the DC / DC up converter 14. DC / DC up-converter 1
Since 4 is an input outside the control range, it passes the input and outputs.

When the DC input voltage E drops below the required voltage Vo, the input falls outside the control range of the constant voltage circuit 13, and the constant voltage circuit 13 outputs a voltage dropped below the required voltage Vo. The DC / DC up converter 14 is also a DC / D
When a commercially available IC or the like composed of a chopper type circuit is selected and used similarly to the C down converter 16, when the input from the constant voltage circuit 13 becomes lower than Vo, the input is boosted to obtain the required voltage Vo. I am allowed to do so.

The output of the DC / DC down converter 16 is passed through the backflow prevention diode 17, and the output of the DC / DC upconverter 14 is also in the same manner as the backflow prevention diode 15.
And the output terminal 21 of the DC / DC converter 31 via the backflow prevention diode 18.
Is connected to the positive side of. The common electrode side of the output terminal 10 is connected to the common electrode side of the output terminal 21 of the DC / DC converter 31, and the DC / DC converter 31
Is used as a common electrode for operating each part, and a series circuit of a resistor 19 and a light emitting diode 20 is connected between the anode of the backflow preventing diode 18 and the common electrode to cause the light emitting diode 20 to emit light to operate the power supply. To be able to display.

As shown in FIG. 2, for a DC power supply having a voltage characteristic (E) that drops with the passage of time,
In the voltage range VH between the voltage peak and the reference voltage VS, D
The C / DC down converter 16 is operated to operate the required voltage V
Therefore, the DC / DC up-converter 14 is operated in the voltage range VL below the reference voltage VS up to the lower limit voltage V2 of the operation of the DC / DC up-converter 14, and within the voltage range VL, the reference voltage VS During the required voltage Vo, the constant voltage circuit 13 steps down to obtain the required voltage Vo, and below the required voltage Vo, the DC / DC up converter 14 steps up to obtain the required voltage Vo.
Therefore, it is possible to lengthen the usable period and obtain a continuous required voltage Vo. There is also a method of using a three-terminal regulator instead of the DC / DC down converter 16 to drop the voltage. However, the three-terminal regulator has a large power loss, which accelerates consumption of the DC power supply. However, in the present invention, the DC / DC down converter 16 is used. Therefore, the usable period of the DC power supply can be extended.

[0016]

As described above, according to the present invention,
For a DC power supply having a voltage characteristic that drops with the lapse of usage time, a DC / DC down converter, a constant voltage circuit, and a DC / DC up converter convert the input voltage so that a required voltage can be obtained. DC / D in the circuit
The control ranges of the C down converter and the DC / DC up converter are connected to each other so that the required voltage can be continuously obtained. Therefore, it is possible to lengthen the period for obtaining the required voltage and obtain the continuously required voltage. A possible DC / DC converter can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a DC power supply device of the present invention.

FIG. 2 is an explanatory diagram of output voltage characteristics of the DC power supply device of the present invention.

FIG. 3 is a configuration diagram showing an embodiment of the voltage switching circuit of FIG.

FIG. 4 is an explanatory diagram of output voltage characteristics of a conventional DC power supply device.

[Explanation of symbols]

 1 Solar Cell 2 Diode 3 Solar Cell 4 Diode 5 3 Terminal Regulator 6 Capacitor 7 Capacitor 8 Diode 9 Electric Double Layer Battery 10 Output Terminal 12 Voltage Switching Circuit 13 Constant Voltage Circuit 14 DC / DC Up Converter 15 Diode 16 DC / DC Down Converter 17 Diode 18 diode 19 resistor 20 light emitting diode 21 output terminal 25 voltage comparison unit 26 switch circuit 27 switch circuit 30 DC power supply unit 31 DC / DC converter

Claims (3)

[Claims] 1. A direct-current input voltage having a voltage characteristic that drops with the lapse of use time is compared with a reference voltage, and when the reference voltage is exceeded, the first output terminal is provided, and when the reference voltage is not exceeded, the second output terminal is provided. A voltage switching circuit that outputs the DC input voltage to an output terminal of the DC / DC converter, a DC / DC down converter that lowers the input from the first output terminal to a required voltage, and an input from the second output terminal to the required voltage. Connected to the output circuit of this constant voltage circuit and a constant voltage circuit that drops the voltage to the output, boosts the voltage to the required voltage when the input voltage drops below the required voltage, and passes the input voltage at other times for output. / DC up-converter and a DC / DC converter including an output circuit for connecting the output sides of the DC / DC down converter and the DC / DC up-converter to each other to output a required voltage. Bata. 2. The voltage switching circuit compares the DC input voltage with a reference voltage, and outputs a control signal to one output terminal when the voltage exceeds the reference voltage and outputs the control signal to the other output terminal when the voltage is below the reference voltage. And a DC input voltage for each of which a DC input voltage is input, and a DC input voltage exceeding a reference voltage is output according to a control signal input from the one output terminal.
2. The DC / D according to claim 1, wherein the DC / D switch circuit comprises:
C converter. 3. The DC / DC converter according to claim 1, wherein the output circuit is formed by connecting the outputs of the DC / DC down converter and the DC / DC up converter via diodes for preventing backflow.