JP2006014544A - Step-down device, method and circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a size of a step-down device, and to realize a large step-down ratio by reducing power loss in the circuit. <P>SOLUTION: The step-down device comprises switching elements 15a, 15b, 17a-17c for connecting a plurality of capacitors 11a-11c in series by connecting a diode between the capacitors and switching the capacitors 11a-11c to parallel connection state. Since the output voltage decreases at the time of series connection and increases at the time of parallel connection, a control circuit 18 adjusts the period of series connection and the period of parallel connection to realize a large step-down ratio. As compared with a case where a coil (reactor) is used in chopper control, the size is reduced, and power loss is also reduced in the circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a step-down device, a step-down method, and a step-down circuit that step down and output an input voltage.

  In recent years, electric motors are used not only for trains such as railways, but also for automobiles for traveling. As an electric motor in such an automobile, there is an example in which a driving voltage is driven via an inverter with a DC voltage of about 200 to 300V.

  On the other hand, the drive voltage of the electric motor mounted on the automobile has shifted to a high voltage with the aim of improving the acceleration force of the automobile, and a drive voltage exceeding 500V is required.

  For this reason, as a drive voltage, it is necessary to adjust both the high voltage which exceeds 500V as mentioned above, and the increase in the volume of a rechargeable battery for relaxation of a discharge rate.

  In addition, a regenerative function such as charging a battery when going down a hill is also required in an automobile.

  In general, a step-down device (step-down circuit) is used as one that adjusts the regenerative voltage and applies an output voltage to the battery (load) according to various situations. This step-down device steps down the generated voltage from the generator by chopper control and outputs a voltage, and controls the step-down ratio by the ratio of the pulse ON time to the OFF time in a fixed period.

  In general, a step-down device using chopper control controls the step-down ratio by the ratio of the on time and off time of a pulse in a certain period as described above. However, if this step-down ratio increases, the waveform of the electronic circuit Since there is a limit to the responsiveness of the rise time and the fall time, not only is it difficult to ensure a sufficient step-down ratio, but if the responsiveness of the waveform is not sufficient, significant power loss can occur.

  In addition, in the conventional step-down device using chopper control, a coil (reactor) is used, so that the size is increased and the space saving of the automobile is reversed.

  Accordingly, an object of the present invention is to provide a step-down device, a step-down method, and a step-down circuit that can be reduced in size, have small power loss in the circuit, and can realize a large step-down ratio.

  In order to solve the above problem, the invention according to claim 1 is a step-down device that steps down an input voltage and outputs the voltage, a plurality of capacitors, a series connection means for connecting the plurality of capacitors in series, and the plurality of the plurality of capacitors. Parallel connection means for connecting the capacitors in parallel, a first period in which the plurality of capacitors are connected in series by the series connection means and charging is performed by the input voltage, and the plurality of capacitors are connected in parallel by the parallel connection means And a control means for alternately controlling the second period of discharge output.

  The invention according to claim 2 is the step-down device according to claim 1, wherein the series connection means is a diode connected between capacitors, and the parallel connection means is the control means. Switch means for switching the plurality of capacitors to a parallel connection state under control.

  The invention according to claim 3 is the step-down device according to claim 2, further comprising an output capacitor connected to the plurality of capacitors via the switch means, wherein the output capacitor is the first capacitor. It is charged by the discharge voltages of the plurality of capacitors during the period 2 and is discharged during the first period.

  The invention according to claim 4 is a step-down method for stepping down and outputting an input voltage, wherein a plurality of capacitors are connected in series, and the plurality of capacitors are charged with the input voltage; and The second period in which a plurality of capacitors are connected in parallel and discharge is output is controlled alternately.

  The invention according to claim 5 is a step-down circuit for stepping down and outputting an input voltage, wherein a plurality of capacitors, serial connection means for connecting the plurality of capacitors in series, and a parallel connection for connecting the plurality of capacitors in parallel A first period in which the plurality of capacitors are connected in series by the series connection means and charging is performed by the input voltage; and a second period in which the plurality of capacitors are connected in parallel by the parallel connection means and discharged. And a control means for alternately controlling the periods.

  In the step-down device according to the first, second, fourth, and fifth aspects of the present invention, an input voltage is divided and output by a plurality of capacitors, so that a rough step-down ratio can be easily obtained depending on the number of capacitors. Therefore, a large step-down ratio can be easily realized, for example, an output voltage of about 1 / N of the input voltage is output using N capacitors.

  In addition, as compared with a step-down device using chopper control, it is possible to reduce the size because a coil (reactor) is not required.

  In addition, since a low output voltage is output using the charging of the capacitor, power loss is reduced as compared with a step-down device using chopper control.

  And fine voltage | pressure reduction adjustment can be easily performed by adjusting a 1st period and a 2nd period by a control means.

  In the step-down device according to the third aspect of the present invention, the output capacitor is charged by the discharge voltages of the plurality of capacitors in the second period and discharged in the first period, so that the output voltage is stabilized. be able to.

<Configuration>
FIG. 1 is a block diagram schematically showing a supply path for a regenerative voltage of an automobile equipped with a step-down device (step-down circuit) 1 according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing the step-down device 1. is there.

  As shown in FIG. 1, the step-down device 1 is used for stepping down a regenerative voltage when a regenerative voltage is applied from the generator 5 when the vehicle is traveling down a hill or the like. As shown in FIG. 2, the input voltage Vin is stepped down to obtain a voltage of 1 / N (N is a natural number of 2 or more). In this embodiment, an example in which the input voltage Vin is stepped down by a factor of three is described.

  Here, in this embodiment, the element described as the generator 5 is, for example, the traveling motor when the traveling motor is used as a generator, and the element described as the load 21 is, for example, the regeneration. Battery at the time. However, examples to which the present invention is applied are not necessarily limited thereto.

  As shown in FIG. 2, the step-down device 1 includes three capacitors (first to third capacitors) 11a to 11c functioning as a battery, and a first capacitor 11a and a second capacitor 11b connected in series. Switching element 15a, 15b, 17a for connecting the three capacitors 11a-11c in parallel with the diode 13a, the second diode 13b connecting the second capacitor 11b and the third capacitor 11c in series 17c and a control circuit (control means) 18 for controlling the charging time in the series connection and the consumption time in the parallel connection by turning on and off the switching elements 15a, 15b, and 17a to 17c. The step-down voltage output to the load 21 is adjusted by the control.

  One end of the first capacitor 11 a is connected to the emitter of a charge / discharge changeover switch (input voltage charging transistor: npn transistor) 19 whose collector is connected to one end of the generator 5.

  The anode of the first diode 13a is connected to the other end of the first capacitor 11a.

  One end of the second capacitor 11b is connected to the cathode of the first diode 13a.

  The anode of the second diode 13b is connected to the other end of the second capacitor 11b.

  The third capacitor 11 c is connected between the cathode of the second diode 13 b and the other end of the generator 5.

  Due to the connection relationship between the capacitors 11a to 11c and the diodes 13a and 13b, the three capacitors 11a to 11c are connected when the charge / discharge switch 19 is turned on and the switching elements 15a, 15b, and 17a to 17c are turned off. The generator 5 is connected in series with the current flowing from one end to the other end. That is, each diode 13a, 13b functions as a series connection means for connecting the capacitors 11a to 11c in series. In this state of series connection, the capacitors 11a to 11c are charged, and a relatively small output voltage is supplied to the load 21 by discharging from the output capacitor 7 (FIG. (See T1 in 3: described later).

  As the first switching element 15a, for example, an npn transistor is used, its collector is connected to the other end of the generator 5, and its emitter is connected to a connection point between the first capacitor 11a and the first diode 13a. .

  As the second switching element 15b, for example, an npn transistor is used, its collector is connected to the other end of the generator 5, and its emitter is connected to a connection point between the second capacitor 11b and the second diode 13b. .

  As the third switching element 17a, for example, an npn transistor is used, its collector is connected to the connection point between the charge / discharge changeover switch 19 and the first capacitor 11a, and its emitter is connected to the load 21.

  As the fourth switching element 17b, for example, an npn transistor is used, its collector is connected to the connection point between the first diode 13a and the second capacitor 11b, and its emitter is connected to the load 21.

  As the fifth switching element 17c, for example, an npn-type transistor is used, its collector is connected to the connection point between the second diode 13b and the third capacitor 11c, and its emitter is connected to the load 21.

  Here, the charge / discharge changeover switch 19 and the switching elements 15 a, 15 b, 17 a to 17 c are turned on / off by a gate signal from the control circuit 18. In FIG. 2, for the sake of convenience, the control circuit 18 is shown to output a gate signal only to the charge / discharge changeover switch 19, but in actuality, not only the charge / discharge changeover switch 19 but also the switching elements 15a, Gate signals are also output to 15b, 17a to 17c.

  Here, when these switching elements 15 a, 15 b, 17 a to 17 c are turned on and the charge / discharge switching switch 19 is turned off, the first to third capacitors 11 a to 11 c are connected in parallel to each other and to the load 21. A relatively high voltage will be supplied (see T2 in FIG. 3). That is, the switching elements 15a, 15b, and 17a to 17c function as a parallel connection unit that connects the capacitors 11a to 11c in parallel.

  For example, a microcomputer chip including a ROM and a RAM is used as the control circuit 18, and the charging time at the time of series connection (series charging period T1: first period) and the consumption time at the time of parallel connection (parallel discharge period T2: By adjusting the second period), a voltage that is about one third of the input voltage Vin is output from the step-down device 1.

  2 denotes an output capacitor connected in parallel to the load 21. For charging and discharging the output capacitor 7, a stable output voltage is supplied to the load 21. Is.

<Operation>
The operation of the step-down device 1 having the above configuration will be described. FIG. 3 is a timing chart showing output voltages to the charge / discharge changeover switch 19, the first to fifth switching elements 15 a, 15 b, 17 a to 17 c and the load 21, and (A) in FIG. (B) in the figure is the on / off state of the first and second switching elements 15a and 15b, (C) in the figure is the on / off state of the third to fifth switching elements 17a to 17c, (D) in the figure shows the output voltage applied to the load 21.

  First, at the time of charging the capacitors 11a to 11c, in (A) in FIG. 3, the charge / discharge changeover switch 19 is turned on and becomes conductive as in the period T1. In the period T1, as shown in FIGS. 3B and 3C, the switching elements 15a, 15b, and 17a to 17c are turned off.

  In this period T1, the three capacitors 11a to 11c are connected in series through the first diode 13a and the second diode 13b, so that the input voltage Vin applied from one end of the generator 5 is connected in series to each other. The three capacitors 11a to 11c are applied.

  In this period T1, the three capacitors 11a to 11c are simultaneously charged by the input voltage Vin, while power is supplied to the load 21 by discharging from the output capacitor 7 as shown in FIG. Therefore, the output voltage output to the load 21 is relatively small.

  Next, at the time of discharging the capacitors 11a to 11c, the charge / discharge changeover switch 19 is turned off to enter a cut-off state as in the period T2 in FIG. At the same time, the five switching elements 15a, 15b, and 17a to 17c are turned on and become conductive as in a period T2 of (B) and (C) in FIG.

  Then, the three capacitors 11 a to 11 c are connected in parallel to each other, supplying power to the load 21 and charging the capacitor 7.

  Here, as shown in FIG. 3D, the output voltage output to the load 21 is a period during which power is supplied to the load 21 by discharging from the three capacitors 11a to 11c (the output capacitor 7). Is charged at a high voltage at T2. On the other hand, when a voltage is discharged from the output capacitor 7 (a period in which the three capacitors 11a to 11c are connected in series and charged) at T1, there is Will begin to decline.

  Therefore, by performing control to change the series charging period T1 and the parallel discharging period T2, the output voltage to the load 21 can be made constant.

  Specifically, the output voltage to the load 21 can be increased by increasing the series charging period T1 and shortening the parallel discharge period T2.

  By adjusting the series charging period T1 and the parallel discharging period T2 by the control circuit 18, it is possible to easily output a voltage about one third of the input voltage Vin.

  In order to increase the output current, a large amount of electricity may be stored in the three capacitors 11a to 11c in the series charging period T1.

  As described above, the input voltage Vin is divided and output by the plurality of capacitors 11a to 11c, so that the rough step-down ratio can be easily adjusted by the number of capacitors 11a to 11c. For example, N capacitors are used. A large step-down ratio can be easily realized by outputting an output voltage that is approximately 1 / N of the input voltage.

  In addition, as compared with a step-down device using chopper control, it is possible to reduce the size because a coil (reactor) is not required.

  Furthermore, fine voltage step-down adjustment can be easily performed by adjusting the first period and the second period by the control means.

  Furthermore, since the capacitors 11a to 11c generally have a small power loss, the power loss of the entire step-down device can be made as small as possible.

  In the above embodiment, an example in which the voltage of about one third of the input voltage Vin is output using the three capacitors 11a to 11c has been described. However, N (where N is 2 or 4 or more) May be used to output a voltage about 1 / N times the input voltage Vin. In this way, a voltage about 1 / N can be easily obtained with N capacitors, so the step-down ratio can be set freely by simply setting the number of capacitors used, and the design is easy. Can be provided.

It is a block diagram which shows the state by which the pressure | voltage fall apparatus which concerns on one Embodiment of this invention was applied to the motor vehicle. 1 is a circuit diagram showing a step-down device according to an embodiment of the present invention. It is a timing chart which shows operation and output voltage of each part of a pressure-down converter concerning one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Voltage step-down device 7 Output capacitor 11a-11c Capacitor 13a, 13b Diode 15a, 15b, 17a-17c Switching element 18 Control circuit 19 Charging / discharging changeover switch 21 Load

Claims (5)

A step-down device that steps down and outputs an input voltage,
Multiple capacitors,
Series connection means for connecting the plurality of capacitors in series;
Parallel connection means for connecting the plurality of capacitors in parallel;
A first period in which the plurality of capacitors are connected in series by the series connection means and charging is performed by the input voltage; and a second period in which the plurality of capacitors are connected in parallel by the parallel connection means and discharged. A step-down device comprising control means for alternately controlling. The step-down device according to claim 1,
The series connection means is a diode connected between capacitors,
The step-down device, wherein the parallel connection means is switch means for switching the plurality of capacitors to a parallel connection state under the control of the control means. The step-down device according to claim 2,
An output capacitor connected to the plurality of capacitors via the switch means;
The step-down device, wherein the output capacitor is charged by the discharge voltages of the plurality of capacitors in the second period and discharges and outputs in the first period. A step-down method for stepping down and outputting an input voltage,
A first period in which a plurality of capacitors are connected in series and the plurality of capacitors are charged with the input voltage, and a second period in which the plurality of capacitors are connected in parallel and discharged and output are controlled alternately. A step-down method characterized. A step-down circuit that steps down and outputs an input voltage,
Multiple capacitors,
Series connection means for connecting the plurality of capacitors in series;
Parallel connection means for connecting the plurality of capacitors in parallel;
A first period in which the plurality of capacitors are connected in series by the series connection means and charging is performed by the input voltage; and a second period in which the plurality of capacitors are connected in parallel by the parallel connection means and discharged. A step-down circuit comprising control means for alternately controlling.

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