WO2015178131A1

WO2015178131A1 - Switching power supply

Info

Publication number: WO2015178131A1
Application number: PCT/JP2015/061433
Authority: WO
Inventors: 榎本　倫人; 鈴木　慎吾
Original assignee: 矢崎総業株式会社
Priority date: 2014-05-20
Filing date: 2015-04-14
Publication date: 2015-11-26
Also published as: DE112015002340T5; CN106233597A; JP2015220901A

Abstract

A DC/DC converter (2) working as a switching power supply comprises: a switching type power supply circuit (21) capable of executing a voltage conversion operation for converting an input voltage and generating an output voltage; and a control unit (22) for controlling the voltage conversion operation of the power supply circuit (21). The control unit (22) allows the power supply circuit (21) to execute the voltage conversion operation while the load factor of the power supply circuit (21) is a predetermined value or more. This brings about effects of enabling the power conversion efficiency to be improved and enabling the device to be prevented from increasing in size.

Description

Switching power supply

The present invention relates to a switching power supply.

Conventionally, a switching power supply that converts an input voltage and generates an output voltage has been designed and controlled to support a maximum output. That is, in the switching power supply, the power conversion efficiency also fluctuates due to the load variation, and the power conversion efficiency tends to deteriorate particularly as the load is lighter (lower load factor). On the other hand, for example, in Patent Document 1, a plurality of DC / DC converters (switching power supplies) are connected in parallel, and the number of DC / DC converters operated in accordance with the load current of the device is controlled. The structure which avoids that a state arises and prevents the fall of power conversion efficiency is disclosed.

JP 2012-210013 A

However, as described in Patent Document 1, in the case of a power supply device in which a plurality of switching power supplies are connected in parallel, the number of switching power supplies incorporated in the device increases, resulting in a problem that the device is enlarged.

The present invention has been made in view of the above, and an object of the present invention is to provide a switching power supply capable of improving power conversion efficiency and preventing the enlargement of the apparatus.

In order to solve the above problems, a switching power supply according to the present invention controls a switching-type power supply circuit capable of performing a voltage conversion operation that converts an input voltage and generates an output voltage, and controls the voltage conversion operation of the power supply circuit. A control unit that performs the voltage conversion operation of the power supply circuit when the load factor of the power supply circuit is equal to or greater than a predetermined value.

In the switching power supply described above, it is preferable that the control unit causes the voltage conversion operation of the power supply circuit to be executed when the remaining amount of power stored in the power storage device on the output side of the power supply circuit is equal to or less than a predetermined value.

In the above switching power supply, the control unit monitors the state of the load target on the output side of the power supply circuit, and when the load target is in an operating state, compared to when the load target is in a non-operating state. Thus, it is preferable to increase the predetermined value of the remaining power storage amount.

Since the switching power supply according to the present invention performs the voltage conversion operation of the power supply circuit while limiting the load factor of the power supply circuit to a predetermined value or more, the power conversion efficiency can be maintained at a high position. In addition, the power conversion efficiency is improved by switching the execution / stop of the voltage conversion operation by a single switching power supply, and it is necessary to use a plurality of switching power supplies together in order to avoid the occurrence of a light load state. Absent. Thereby, there exists an effect that power conversion efficiency can be improved and the enlargement of an apparatus can be prevented.

FIG. 1 is a diagram illustrating an example of a schematic configuration of a power supply device to which a DC / DC converter (switching power supply) according to an embodiment of the present invention is applied. FIG. 2 is a block diagram showing a schematic configuration of the DC / DC converter according to the present embodiment in FIG. FIG. 3 is a flowchart showing the switching process of the voltage conversion operation by the DC / DC converter according to the present embodiment. FIG. 4 is a diagram illustrating an example of the characteristic of the power conversion efficiency with respect to the load factor in the switching power supply. FIG. 5 is a diagram illustrating another example of a schematic configuration of a power supply device to which the switching power supply according to the present embodiment is applied.

Hereinafter, embodiments of a switching power supply according to the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[Embodiment]
First, the configuration of a switching power supply according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of a schematic configuration of a power supply device to which a DC / DC converter (switching power supply) according to an embodiment of the present invention is applied. FIG. 2 is a block diagram showing a schematic configuration of the DC / DC converter according to the present embodiment in FIG.

A power supply device 1 illustrated in FIG. 1 is a device for supplying electric power to a starter motor 4 that starts an engine in a hybrid vehicle, for example. In the present embodiment, a step-down DC / DC converter 2 will be described as an example of a switching power supply that is applied to the power supply device 1 and converts an input voltage to generate an output voltage.

As shown in FIG. 1, the power supply device 1 includes a DC / DC converter 2, a generator 3, a starter motor 4, a high voltage battery 5, a low voltage battery 6, a high voltage load 7, and a low voltage load. 8 and.

The DC / DC converter 2 is a step-down type, and in the example of FIG. 1, a voltage conversion operation for stepping down an input voltage of 48V to an output voltage of 14V can be executed. In the configuration of the power supply device 1 shown in FIG. 1, the DC / DC converter 2 performs the voltage conversion on the electric power input from the high voltage side (the generator 3 or the high voltage battery 5) during the voltage conversion operation. Output to the low voltage side (low voltage battery 6, low voltage load 8, or starter motor 4).

The generator 3 obtains electric energy (electric power) from motive energy, and supplies the generated electric power to the DC / DC converter 2, the high-voltage battery 5, and the high-voltage load 7. The high voltage side battery 5 is a power storage device that stores electric power supplied from the generator 3, and supplies the stored electric power to the high voltage side load 7. The high voltage side load 7 is an arbitrary device that is operated by electric power supplied from the generator 3 or the high voltage side battery 5.

The low voltage side battery 6 is a power storage device that stores electric power supplied from the generator 3 via the DC / DC converter 2, and supplies the stored electric power to the starter motor 4 and the low voltage side load 8. The low-voltage load 8 is an arbitrary device that operates with electric power supplied from the generator 3 or the low-voltage battery 6. The starter motor 4 is operated by electric power supplied from the generator 3 or the low voltage side battery 6.

As shown in FIG. 2, the DC / DC converter 2 includes a power supply circuit 21 and a control unit 22.

The power supply circuit 21 is a voltage conversion circuit that constitutes a switching power supply capable of performing a voltage conversion operation for converting an input voltage and generating an output voltage. Since the power supply circuit 21 can use a known circuit that generates a desired output voltage by controlling on / off of the switching elements among the constituent elements, the detailed description of the internal configuration is omitted. .

The control unit 22 controls the voltage conversion operation of the power supply circuit 21. Specifically, the control unit 22 controls the voltage conversion operation by controlling on / off of the switching element of the power supply circuit 21. As shown in FIG. 2, the control unit 22 includes a vehicle operating status (ignition on / off), an engine operating status (engine speed), a generator operating status (generator voltage), a battery status (low voltage side battery 6 Voltage and current), load operation status (load on (operational state) / off (non-operational state)), and other information. The load operation status can be obtained using, for example, communication. Based on the input information, the control unit 22 determines whether or not the voltage conversion operation by the power supply circuit 21 can be performed. More specifically, when it is determined that the load factor of the power supply circuit 21 is equal to or greater than a predetermined value based on the input information, the control unit 22 causes the power supply circuit 21 to perform a voltage conversion operation. On the other hand, when determining that the load factor of the power supply circuit 21 is lower than the predetermined value, the control unit 22 switches the power supply circuit 21 to the standby state and does not execute the voltage conversion operation. A specific method for determining that the load factor of the power supply circuit 21 is equal to or greater than a predetermined value by the control unit 22 will be described later with reference to FIG.

The control unit 22 is physically configured to include an electronic circuit mainly including a well-known microcomputer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an interface. Integrated circuit. The function of the control unit 22 is to load various application programs stored in the ROM into the RAM and execute them by the CPU, thereby operating the various devices of the power supply device 1 under the control of the CPU, and data in the RAM and ROM. This is realized by reading and writing. Note that the control unit 22 may be configured by an analog circuit, and each function of the control unit 22 may be realized by the operation of the analog circuit.

Next, the operation of the DC / DC converter 2 (switching power supply) according to this embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing the switching process of the voltage conversion operation by the DC / DC converter according to the present embodiment. The process of the flowchart shown in FIG. 3 is performed by the control unit 22 of the DC / DC converter 2 at predetermined intervals, for example.

In step S01, detection of the state of charge of the low voltage side battery 6 is started. When the process of step S01 is completed, the process proceeds to step S02.

In step S02, the DC / DC converter 2 is set to a standby state in which no voltage conversion operation is performed. When the process of step S02 is completed, the process proceeds to step S03.

In step S03, it is determined whether or not the vehicle on which the power supply device 1 is mounted is in an ignition-on state (IG = ON). The control unit 22 can make this determination based on, for example, information on the vehicle operation status input from the vehicle (ignition on / off). If the result of determination in step S03 is that the ignition is on (Yes in step S03), the process proceeds to step S04. On the other hand, if the ignition is off (No in step S03), the process returns to step S02, and the standby state of the DC / DC converter 2 is maintained until the ignition is on.

In step S04, it is determined whether or not the low-pressure side load 8 is in an operating state (on state). In the present embodiment, the low-voltage load 8 is an element that is a load target on the output side of the power supply circuit 21 of the DC / DC converter 2. The control unit 22 determines the state of the load target on the output side of the power supply circuit 21 based on, for example, information on the load operation state input from the vehicle (load on (operating state) / off (non-operating state)). It can be performed. As a result of the determination in step S04, if the low-pressure side load 8 is in the non-operating state (No in step S04), the process proceeds to step S05. If the low-pressure side load 8 is in the operating state (Yes in step S04), the process proceeds to step S06. move on.

In step S05, it is determined whether or not the state of charge (SOC) of the low voltage side battery 6 exceeds 80% in response to the determination that the low voltage side load 8 is in the non-operating state in step S04. The control unit 22 can calculate the SOC based on, for example, information on the battery state input from the vehicle (the voltage and current of the low-voltage battery 6), and can make this determination using the calculated SOC. As a result of the determination in step S05, when the SOC of the low voltage side battery 6 is 80% or less (No in step S05), the process proceeds to step S07. On the other hand, when the SOC of the low voltage side battery 6 exceeds 80% (Yes in Step S05), the process returns to Step S02, and the DC / DC converter 2 stands by until the SOC of the low voltage side battery 6 becomes 80% or less. State is maintained.

In step S06, it is determined whether or not the state of charge (SOC) of the low voltage side battery 6 exceeds 90% in response to the determination that the low voltage side load 8 is in the operating state in step S04. As a result of the determination in step S06, if the SOC of the low voltage side battery 6 is 90% or less (No in step S06), the process proceeds to step S07. On the other hand, when the SOC of the low voltage side battery 6 exceeds 90% (Yes in Step S06), the process returns to Step S02, and the DC / DC converter 2 stands by until the SOC of the low voltage side battery 6 becomes 90% or less. State is maintained.

In the present embodiment, “80%” is used in step S05 and “90%” is used in step S06 as the SOC threshold value of the low-voltage side battery 6, but the threshold value in step S06 is that of step S05. Other values may be used as long as they are set relatively large. Steps S05 and S06 are both DC / DC in step S08, which will be described later, when the SOC is equal to or less than a predetermined threshold value (predetermined value), that is, when the low voltage side battery 6 is in a state where there is sufficient power storage. This is a determination condition for executing the voltage conversion operation of the converter 2. However, step S06 is a determination step that proceeds when the low-voltage side load 8 that is the load target on the output side of the power supply circuit 21 of the DC / DC converter 2 is in an operating state (driving). In this case, the DC / DC Part of the electric power supplied from the converter 2 to the low voltage side is also used to drive the low voltage side load 8. For this reason, in the case of step S06, even if the chargeable amount of the low-voltage side battery 6 is relatively small compared to step S05 that proceeds when the low-voltage side load 8 is in a non-operating state (stopped), the low-voltage side battery 6 is considered to be less likely to be overcharged due to excessive power supply. For the above reasons, the SOC threshold value of the low-voltage side battery 6 is set to be relatively larger than the threshold value of step S06. In other words, when the low-voltage side load 8 is in an operating state, the SOC threshold value of the low-voltage side battery 6 is increased and increased as compared with a case where the low-voltage side load 8 is in an inoperative state.

In step S07, it is determined whether or not the generator 3 is generating power. The control part 22 can determine this based on the information (generator voltage) regarding the generator operating condition input, for example from the inside of a vehicle. If the result of determination in step S07 is that the generator 3 is generating power (Yes in step S07), the process proceeds to step S08. On the other hand, when the generator 3 is stopped (No in step S07), the process returns to step S02, and the standby state of the DC / DC converter 2 is maintained until the generator 3 is driven.

In step S08, the DC / DC converter 2 performs a voltage conversion operation. Thereby, the electric power generated by the generator 3 is stepped down by the DC / DC converter 2 and supplied to the low voltage side battery 6 to be stored. In addition, when the low-voltage load 8 is in an operating state, a part of the power output from the DC / DC converter 2 is also supplied to the low-voltage load 8. When the process of step S08 is completed, the process returns to step S03, and the determination of each condition (steps S03 to S07) for executing the voltage conversion operation is performed again. The voltage conversion operation is continuously executed while each condition is satisfied. When each condition is not satisfied, the process proceeds to step S02 and the voltage conversion operation is stopped.

When the processing shown in the flowchart of FIG. 3 is summarized, the voltage conversion operation of the DC / DC converter 2 is executed when the remaining charge amount of the low voltage side battery 6 is equal to or less than a predetermined value and there is a sufficient margin for storing power. I am letting. On the other hand, the execution of the voltage conversion operation is stopped when the remaining charge of the low-voltage side battery 6 is greater than a predetermined value and there is little room for storing power. The reason for this will be described with reference to FIG. FIG. 4 is a diagram illustrating an example of the characteristic of the power conversion efficiency with respect to the load factor in the switching power supply.

4 represents the load factor of the switching power supply (DC / DC converter 2 in this embodiment). Here, the “load factor” represents the ratio of the current (load current) flowing through the switching power supply to the rated current (A) (or the ratio of the load capacity to the rated output capacity (W)) as a percentage. That is, the state where the load factor is 100% means a state where a rated current flows through the switching power supply. The vertical axis in FIG. 4 indicates the power conversion efficiency η of the switching power supply. Here, “power conversion efficiency” represents the efficiency with which input / output power is converted in the switching power supply. The power conversion efficiency η is a ratio between the input power and the output power of the switching power supply, and can be expressed by η = POUT / PIN × 100 (%) where the input power is PIN and the output power POUT. The power conversion efficiency η is more efficient as it approaches 100%, and the internal loss is reduced. Therefore, if the power conversion efficiency is improved, the power supply device can be reduced in size. FIG. 4 shows an example of characteristics relating to the load factor and power conversion efficiency in the switching power supply by a solid line.

As shown in FIG. 4, the lower the load factor (the lighter the load), the worse the power conversion efficiency η. On the other hand, as the load factor increases, the power conversion efficiency η gradually improves, and as the load factor approaches 100%, the power conversion efficiency η stabilizes at a high position. The higher the load factor, the easier it is to maintain the power conversion efficiency near 100%. That is, as the load current flowing through the DC / DC converter 2 approaches the rated current, the load factor approaches 100%, and the power conversion efficiency can be improved. The load factor is preferably as close to 100% as long as the power conversion efficiency can be maintained in a region close to 100%. In the example of FIG. 4, the load factor only needs to be larger than about 50%, and is preferably larger than about 75%.

In order to increase the load current flowing through the DC / DC converter 2 to the rated current, it is necessary to sufficiently consume power on the low voltage side of the power supply device 1. In the power supply device 1 of the present embodiment, when the remaining amount of power stored in the low-voltage side battery 6 is equal to or less than a predetermined value, it is determined that the current used for charging the low-voltage side battery 6 can be expected to the vicinity of the rated current. Then, the voltage conversion operation of the DC / DC converter 2 is executed, current is passed from the high voltage side to the low voltage side, and the low voltage side battery 6 is positively charged by the DC / DC converter 2. As a result, the load factor becomes an operation near 100%, and the power conversion efficiency of the DC / DC converter 2 can be increased. That is, in the present embodiment, the condition that “the remaining charge amount of the low-voltage side battery 6 is equal to or less than a predetermined value” for executing the voltage conversion operation of the DC / DC converter 2 is “the load factor of the DC / DC converter 2. This is an example of a condition for satisfying that “is greater than or equal to a predetermined value (and thereby maintaining power conversion efficiency at a high position)”.

Next, the effect of the DC / DC converter 2 (switching power supply) according to this embodiment will be described.

The DC / DC converter 2 of the present embodiment includes a switching-type power supply circuit 21 that can perform a voltage conversion operation that converts an input voltage and generates an output voltage, and a control unit 22 that controls the voltage conversion operation of the power supply circuit 21. . When the load factor of the power supply circuit 21 is equal to or greater than a predetermined value, the control unit 22 specifically, when the remaining charge amount of the low-voltage side battery 6 on the output side of the power supply circuit 21 is equal to or less than the predetermined value, 21 voltage conversion operation is executed.

With this configuration, the DC / DC converter is focused on when the remaining charge of the low-voltage side battery 6 on the output side of the power supply circuit 21 is equal to or less than a predetermined value, i. Since the voltage conversion operation of the second power supply circuit 21 is executed, the power conversion efficiency of the DC / DC converter 2 can be maintained at a high position, and the power conversion efficiency can be improved. Further, since the power conversion efficiency is improved by switching the execution / stop of the voltage conversion operation by the single DC / DC converter 2, a plurality of units are provided in order to avoid the occurrence of a light load state as in the prior art. It is not necessary to use a DC / DC converter together, and the enlargement of the power supply device 1 can be prevented. Further, since charging is not performed in a situation where the low-voltage side battery 6 has a large amount of remaining power, overcharging of the low-voltage side battery 6 can be avoided, and the life of the low-voltage side battery 6 can be expected to be extended.

In the DC / DC converter 2 of the present embodiment, the control unit 22 monitors the state of the low-pressure side load 8 that is the load target on the output side of the power supply circuit 21, and when the low-pressure side load 8 is in an operating state. As compared with the case where the low-pressure side load 8 is in the non-operating state, the predetermined value of the remaining amount of power storage is increased.

With this configuration, when the low-voltage side load 8 is in the operating state, the range of the remaining amount of charge of the low-voltage side battery 6 in which the voltage conversion operation of the DC / DC converter 2 can be executed is expanded. As described above, when the low-voltage load 8 is in an operating state, the power supplied from the DC / DC converter 2 to the low-voltage side is used not only for charging the low-voltage battery 6 but also for driving the low-voltage load 8. Is done. For this reason, even if the chargeable amount of the low-voltage side battery 6 is relatively small compared with the case where the low-voltage side load 8 is in the non-operating state, electric power is excessively supplied to the low-voltage side battery 6 and overcharge can occur. The nature is low. Therefore, when the low-voltage load 8 is in an operating state, the power conversion efficiency is high even if the range of the remaining amount of charge of the low-voltage battery 6 that can execute the voltage conversion operation of the DC / DC converter 2 is expanded. Can be maintained. Thereby, the opportunity to perform the voltage conversion operation of the DC / DC converter 2 can be increased while improving the power conversion efficiency.

As mentioned above, although embodiment of this invention was described, the said embodiment is shown as an example and is not intending limiting the range of invention. The above-described embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. The above embodiments and modifications thereof are included in the scope of the present invention and the gist thereof, and are also included in the invention described in the claims and the equivalents thereof.

In the above embodiment, the step-down DC / DC converter 2 has been described as an example of the switching power supply that converts the input voltage and generates the output voltage. However, the present invention is not limited to this, and for example, a step-up DC / DC converter may be used. It may be an AC / DC converter.

Moreover, in the said embodiment, although the power supply device 1 shown in FIG. 1 was illustrated as an example of the structure to which the DC / DC converter 2 (switching power supply) which concerns on this embodiment is applied, it is not restricted to this, For example, FIG. The present invention can also be applied to other devices shown in FIG. FIG. 5 is a diagram illustrating another example of a schematic configuration of a power supply device to which the switching power supply according to the present embodiment is applied. The power supply device 1a shown in FIG. 5 is different from the power supply device 1 of the above-described embodiment in that the starter motor 4 is disposed on the high voltage side. The DC / DC converter 2 (switching power supply) according to this embodiment can be applied to various devices other than the

power supply devices

1 and 1a for supplying power to the starter motor 4 shown in FIGS.

In the above-described embodiment, the condition that the voltage conversion operation of the DC / DC converter 2 is executed is exemplified by “the remaining charge amount of the low-voltage side battery 6 is not more than a predetermined value”. Other conditions may be used as long as the conditions satisfy the condition that the load factor of 2 is equal to or greater than a predetermined value (and thereby maintain power conversion efficiency at a high position). For example, the load supplied from the DC / DC converter 2 to the load target based on the load operation status of the load target on the output side of the DC / DC converter 2 (low-voltage side load 8 or starter motor 4 in the example of FIG. 1). When the operating power is a high efficiency point of the load factor to power conversion efficiency characteristic shown in FIG. 4, in other words, the load factor that is the ratio of the load operating power to the rated output capacity of the DC / DC converter 2 is the power conversion efficiency. It is also possible to adopt a configuration in which the voltage conversion operation of the DC / DC converter 2 is executed in the high region.

Moreover, in the said embodiment, when the low voltage | pressure side load 8 is an operation state, when the low voltage | pressure side load 8 is an operation state, the low voltage | pressure side load 8 is inactive. Although the structure which raises compared with the case of a state was illustrated, it is good not only as this but the constant value irrespective of the operation state of the low voltage | pressure side load 8. FIG.

2 DC / DC converter (switching power supply)
21 Power supply circuit 22 Control unit 6 Low voltage side battery (power storage device)
8 Low pressure side load (target load)

Claims

A switching type power supply circuit capable of executing a voltage conversion operation for converting an input voltage and generating an output voltage;
A control unit for controlling the voltage conversion operation of the power supply circuit;
With
The control unit causes the voltage conversion operation of the power supply circuit to be executed when a load factor of the power supply circuit is a predetermined value or more.
2. The switching power supply according to claim 1, wherein the control unit causes the voltage conversion operation of the power supply circuit to be executed when a remaining power amount of a power storage device on an output side of the power supply circuit is equal to or less than a predetermined value.
The control unit monitors the state of the load target on the output side of the power supply circuit, and when the load target is in an operating state, the charge remaining amount is lower than when the load target is in a non-operating state. The switching power supply according to claim 2, wherein the predetermined value is increased.