JP2003284324A - Step-down dc-dc converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a step-down DC-DC converter which has small loss even when an input voltage and an output voltage are largely different and a small size in an entire circuit. <P>SOLUTION: The step-down DC-DC converter comprises a plurality of switch means connected in series with a plurality of capacitors so that its serial sequence can be arbitrarily changed, and a controller. In this converter, the plurality of capacitors connected in series are used as input, sides and the series connection of the arbitrary capacitor is used as an output side. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step-down DC / DC converter which is mainly a converter for converting an input DC current into a DC current having a different voltage and outputting the converted DC current.

[0002]

2. Description of the Related Art As a step-down DC / DC converter, for example, there is a switching regulator such as a chopper circuit shown in FIG. By controlling the switch means with an appropriate duty ratio, it is possible to arbitrarily lower the input voltage and output.

[0003]

A step-down DC / DC converter using a switching regulator such as a chopper circuit has a problem that the loss becomes large when the input voltage and the output voltage are largely different from each other. In addition, other systems also require inductance such as transformers and choke coils, which makes it difficult to downsize the entire circuit.

Therefore, an object of the present invention is to provide a step-down DC / DC converter in which the loss is small and the entire circuit is miniaturized even if the input voltage and the output voltage are largely different.

[0005]

SUMMARY OF THE INVENTION The present invention provides a step-down DC / DC converter that can be downsized and has a simple structure. According to the present invention, a plurality of capacitors are connected in series, The number of capacitors connected in series is set as an output, and the order of the plurality of capacitors is sequentially switched by using a switch means, thereby performing control so that a constant voltage can always be maintained at the output. A step-down DC / DC converter is provided.

According to the present invention, the step-down DC /
Single pole double throw (SPDT) switch means of DC converter
The step-down DC / DC converter is characterized by reducing the number of parts and simplifying the circuit configuration.

Further, according to the present invention, the step-down DC
Provided is a step-down DC / DC converter characterized in that the number of parts is reduced and the circuit configuration is simplified by using a multiplexer as the switch means of the / DC converter.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A step-down DC / DC converter according to an embodiment of the present invention will be described below.

(First Embodiment) FIG. 1 is an explanatory diagram of a step-down DC / DC converter according to a first embodiment of the present invention. In the step-down DC / DC converter of FIG. 1, three capacitors 11 to 13 having substantially the same capacitance and ESR are prepared. All the switches repeatedly perform the operation (T1 → T3) as shown in Table 1 at high speed. The input side always supplies power to the whole and the whole voltage is switched to be equal to the input voltage. The output side always outputs electric power from the two capacitors, and the output voltage is switched to be equal to 2/3 of the total voltage. By alternately replacing the two capacitors that supply electric power to the output side, the output can always maintain the same voltage.

[0010]

[Table 1]

(Second Embodiment) FIG. 2 is an explanatory diagram of a step-down DC / DC converter according to a second embodiment of the present invention. In the step-down DC / DC converter of FIG. 2, all the switches repeatedly switch the operation (T1 → T3) as shown in Table 2 at high speed. Although the basic operation is the same as that of the first embodiment, the number of parts can be significantly reduced by using a single pole double throw (SPDT) switch.

[0012]

[Table 2]

(Third Embodiment) FIG. 3 is an explanatory diagram of a step-down DC / DC converter according to a third embodiment of the present invention. In the step-down DC / DC converter of FIG. 3, all the switches repeatedly perform the operation (T1 → T3) as shown in Table 3 at high speed. The basic operation is the same as that of the embodiment, but by using a multiplexer for the switch, the number of parts can be significantly reduced when the number of capacitors is large.

[0014]

[Table 3]

In the above embodiment, the output voltage was 2/3 of the input voltage. However, if the output voltage is an integer / integer with respect to the input voltage (where output voltage <input voltage), This circuit configuration can be applied to any step-down DC / DC converter. By doing so, for example, even if the output voltage greatly differs from 1/10 of the input voltage, there is almost no loss.

[0016]

As described above, according to the present invention, it is possible to provide a step-down DC / DC converter in which the loss is small and the entire circuit is miniaturized even when the input voltage and the output voltage greatly differ.

[Brief description of drawings]

FIG. 1 is a step-down DC / DC according to a first embodiment of the present invention.
Explanatory drawing of a converter.

FIG. 2 is a step-down DC / DC according to a second embodiment of the present invention.
Explanatory drawing of a converter.

FIG. 3 is a step-down DC / DC according to a third embodiment of the present invention.
Explanatory drawing of a converter.

FIG. 4 is an explanatory diagram of a conventional step-down DC / DC converter.

[Explanation of symbols]

1, 11, 12, 13 Capacitor 2 Switch 3 Input 4 Output 5 Choke coil 6 Diodes 26, 27, 28 Multiplexer 211, 212, 213, 221, 222, 223
Switches 231, 232, 233, 241, 242, 243
Switches 251, 252, 253 Single pole double throw switch

Claims (3)

[Claims] 1. A plurality of capacitors are connected in series, and a plurality of switch means and a controller capable of arbitrarily changing the order of the series are provided. Step-down DC / DC characterized by using an input and an output of a series connection of arbitrary capacitors
converter. 2. The step-down DC / DC converter according to claim 1, wherein in the step-down DC / DC converter, the switch means is a single pole double throw. 3. The step-down DC / DC converter according to claim 1, wherein in the step-down DC / DC converter, the switch means is a multiplexer.