JP2007306665A - Power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device which can use an element which is lower than a conventional element in withstand voltage as an element of a secondary side when load requirement voltages are the same, and can be reduced in size and cost as a whole, in the power supply device comprising a converter whose primary side and secondary side are insulated from each other by transformer. <P>SOLUTION: The converter 13 constituting the power supply device 11 comprises a primary-side oscillation part 15 to which high-voltage DC power HV is inputted, and a secondary-side rectification part 16 which is insulated from the primary-side oscillation part 15 by the transformer 12. An output terminal 16a at the positive side of the secondary-side rectification part 16 is connected to a positive-side terminal 14a of a battery 14, and a negative-side terminal 14b of the battery 14 is grounded. That is, the output terminals 16a, 16b at the secondary side of the transformer 12 and the battery 14 are connected to each other in series. The converter 13 is a step-down type converter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power supply device, and more particularly to a power supply device including a converter in which a primary side and a secondary side are insulated by a transformer.

  As a vehicle that runs on an engine (internal combustion engine), a so-called hybrid vehicle that drives the drive wheels with a motor at the start and low speed ranges and drives the drive wheels with an engine at medium and high speed ranges is practical for low fuel consumption and exhaust gas reduction. It has become. Various auxiliary machines are used in automobiles, and their power sources are also required. And the use voltage of various auxiliary machines is lower than the use voltage of a motor. Such a hybrid vehicle requires a high-voltage power source for motors and a low-voltage power source for various auxiliary machines.

  Normally, when a power supply (output) with a different voltage is created by being insulated from a high-voltage power supply, the configuration is as shown in FIG. That is, the power supply device 51 includes a converter 55 in which a primary-side oscillation unit (switching unit) 52 to which a high-voltage DC power supply HV is input and a secondary-side rectification unit 53 are insulated by a transformer 54. The secondary side rectification unit 53 includes a plus side output terminal 56a and a minus side output terminal 56b, and the output terminal 56b is grounded.

In recent years, electronic equipment for vehicles has been remarkably digitized, and electric loads mounted on vehicles have been diversified. For example, studies are being made on the electrification of actuators including a steering device and a brake device. However, since such an on-vehicle actuator has a high operating voltage, it is difficult to cope with the current low-voltage power supply. Therefore, a power feeding circuit for a vehicle that uses both a low-voltage battery and a high-voltage battery that are conventionally mounted on a vehicle has been proposed (for example, see Patent Document 1). As shown in FIG. 3, in this power supply circuit, a DC / DC converter 62 for voltage drop is interposed between a high voltage DC power source including a high voltage battery 61 and a low voltage load. A low voltage battery 63 provided on the downstream side of the DC / DC converter 62 supplies power to the low voltage load when the DC / DC converter 62 is stopped. In principle, the ECU 64 stops the DC / DC converter 62 when the engine is stopped, but forcibly operates the DC / DC converter 62 when a signal for detecting the presence of a passenger is input even when the engine is stopped.
JP 2001-145333 A

  In the prior art shown in FIG. 2, the converter 55 needs to be capable of outputting the voltage required by the load from the output terminal 56a. Therefore, when the output voltage (secondary side voltage) increases, the turns ratio of the transformer 54 must be lowered. As a result, the current capacity of the primary-side oscillating unit 52 also increases, and a primary-side element having a high current capacity is required. Moreover, since the secondary side voltage becomes high, the element of the secondary side rectification unit 53 needs to have a high breakdown voltage. As a result, it is difficult to reduce the size and cost of the power supply device.

  In the power supply circuit of Patent Document 1, a voltage can be supplied from a low voltage battery 63 and a DC / DC converter 62 to a low voltage load. However, the DC / DC converter 62 and the low voltage battery 63 are connected in parallel to the low voltage load, and the voltage is supplied from the low voltage battery 63 when the DC / DC converter 62 is stopped. Therefore, the DC / DC converter 62 needs to output a voltage necessary for the low voltage load, and if the voltage necessary for the low voltage load increases, the output of the DC / DC converter 62 also increases.

  The present invention has been made in view of the above-described conventional problems, and the object thereof is a power supply device including a converter in which a primary side and a secondary side are insulated by a transformer, when the load request voltage is the same. An object of the present invention is to provide a power supply apparatus that can use an element having a lower withstand voltage than the conventional element as a secondary element, and can be reduced in size and cost as a whole.

  In order to achieve the above object, the invention according to claim 1 comprises a converter in which a primary side and a secondary side are insulated by a transformer, and a battery connected to the secondary side of the converter, An output terminal and the battery are connected in series. In this invention, since the secondary side output terminal of the converter in which the primary side and the secondary side are insulated by a transformer is connected in series to the battery, the output voltage of the power supply device is the output voltage of the battery, the converter This is the sum of the output voltage on the secondary side. Therefore, the output voltage of the converter may be a voltage obtained by subtracting the battery voltage from the voltage required by the load. That is, when the required load voltage is the same, an element having a lower withstand voltage than the conventional element can be used as the element on the secondary side, and the entire apparatus can be reduced in size and cost.

  According to a second aspect of the present invention, in the first aspect of the present invention, the converter is a step-down converter. Therefore, in the present invention, since the output voltage may be lower than the output voltage of the battery, the transformer turns ratio can be increased. As a result, the primary-side current amount is reduced, and the primary-side element having a low current capacity can be used, and the entire apparatus can be further downsized.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the primary power source is a vehicle driving power source. In the case of a vehicle, there is a strong demand for downsizing the equipment accommodated in the engine room, but the present invention can meet the demand.

  According to the present invention, in a power supply device including a converter in which a primary side and a secondary side are insulated by a transformer, when the output voltage is the same, an element having a lower withstand voltage is used as an element on the secondary side than in the past. Therefore, the entire apparatus can be reduced in size and cost.

(First embodiment)
In the following, an embodiment in which the present invention is implemented in a hybrid vehicle and embodied in a power supply apparatus that supplies a high-voltage power supply for a motor that drives a driving wheel by stepping down to a low voltage for an auxiliary machine is shown in FIG. explain.

  As shown in FIG. 1, the power supply device 11 includes a converter 13 in which a primary side and a secondary side are insulated by a transformer 12, and a battery 14 connected to the secondary side of the converter 13. The converter 13 has a primary side oscillation unit (switching unit) 15 to which a high-voltage DC power supply HV is input on the primary side, and a secondary side having a plus side output terminal 16a and a minus side output terminal 16b on the secondary side. A side rectification unit 16 is provided. The primary side oscillation unit 15 is connected to the primary winding 17 of the transformer 12, and the secondary side rectification unit 16 is connected to the secondary winding 18 of the transformer 12. The high-voltage DC power supply HV is, for example, a power supply for a motor that drives driving wheels of a vehicle, and the output is about DC 200 to 300V. The output of the converter 13 is about 30V. The converter 13 is a step-down converter, for example, a one-stone forward converter.

The primary side oscillation unit 15 includes a switching element, and is controlled to be switched by a control signal from a control unit (control IC) (not shown).
The secondary side rectification unit 16 may be configured to be able to convert the current from the secondary winding 18 of the transformer 12 into a direct current. For example, a rectifier circuit combining diodes or a switching element that is alternately turned on and off. Is used. The negative output terminal 16b of the secondary side rectifier 16 is connected to the positive terminal 14a of the battery 14, and the negative terminal 14b of the battery 14 is grounded. That is, the output terminals 16 a and 16 b on the secondary side of the transformer 12 are connected in series with the battery 14. The battery 14 has an output of about 12V. The battery 14 is used without boosting as a power source for auxiliary equipment such as a headlamp of the vehicle.

Next, the operation of the power supply device 11 configured as described above will be described.
The power supply device 11 is used with the input side connected to a high-voltage DC power supply HV of the vehicle and the output terminal 16a connected to a plus side terminal of a load (not shown).

  Based on a control signal output from the control unit, the switching element of the primary side oscillation unit 15 is controlled to be switched, and an alternating current is generated in the primary winding 17 of the transformer 12, and the primary winding 17 and the secondary winding 18 are connected to the secondary winding 18. A voltage corresponding to the winding ratio with the next winding 18 is generated. And the electric current which generate | occur | produced in the secondary winding 18 is rectified by the secondary side rectification | straightening part 16, becomes a direct current, and is output from the output terminal 16a.

  When the number of turns of the primary winding 17 is N1 and the number of turns of the secondary winding 18 is N2, the ratio (transformation ratio) between the primary voltage V1 and the secondary voltage V2 is equal to the turn ratio. Further, the ratio (current transformation ratio) between the primary current I1 and the secondary current I2 is equal to the reciprocal of the turns ratio.

V1 / V2 = N1 / N2
I1 / I2 = N2 / N1
If the voltage required at the load is Vout and the output voltage of the battery 14 is VB, the output voltage of the converter 13, that is, the secondary voltage V2 is a value obtained by subtracting the output voltage VB of the battery 14 from the voltage Vout required at the load. Well, V2 = Vout−VB. For this reason, when the required voltage of the load is the same as the element used in the secondary side rectifying unit 16, it is possible to use an element having a lower withstand voltage than in the conventional case.

Further, since the converter 13 is a step-down type, the turn ratio of the transformer 12 can be increased by lowering the secondary voltage V2 of the converter 13, and the value of the primary current I1 is lowered.
According to this embodiment, the following effects can be obtained.

  (1) The power supply device 11 includes a converter 13 having a primary side and a secondary side insulated by a transformer 12, and a battery 14 connected to the secondary side of the converter 13, and includes output terminals 16a and 16b on the secondary side. A battery 14 is connected in series. Therefore, the output voltage of the output terminal 16 a of the power supply device 11 is the sum of the output voltage VB of the battery 14 and the secondary voltage V2 of the converter 13. Therefore, the secondary voltage (output voltage) V2 of the converter 13 may be a voltage obtained by subtracting the output voltage VB of the battery 14 from the voltage Vout required by the load. As a result, when the required load voltage is the same, an element having a lower withstand voltage than the conventional element can be used as the element on the secondary side, and the entire apparatus can be reduced in size and cost.

  (2) The converter 13 is a step-down converter. Therefore, when the same output voltage is obtained, the turns ratio of the transformer 12 can be increased. As a result, the primary current is reduced, and a primary element having a low current capacity can be used. Further, coupled with the fact that an element having a lower withstand voltage can be used as a secondary side element, it is possible to reduce the size of the transformer 12 and thus the power supply device 11 as a whole.

  (3) The high-voltage DC power supply HV that is the primary power supply of the converter 13 is a vehicle drive power supply. That is, the power supply device 11 is mounted on a vehicle and used. In the case of a vehicle, there is a strong demand for downsizing the equipment accommodated in the engine room, but the power supply device 11 can meet the demand.

The embodiment is not limited to the above, and may be embodied as follows, for example.
The present invention is not limited to a hybrid vehicle, and may be applied to an electric vehicle or a fuel cell (FC) vehicle including a high voltage power source for a drive wheel motor and a battery as a low voltage power source for an auxiliary machine.

O You may apply not only to a vehicle but to the apparatus provided with the battery as a high voltage power supply and a low voltage | pressure power supply.
○ Not only devices with multiple batteries with different output voltages as batteries, but also when using a load with a voltage higher than the output voltage of the battery and applying to a device with a power supply for the power supply in addition to the battery Good.

The converter 13 is not limited to the one-stone forward type but may be another step-down type.
The converter 13 is not limited to the step-down type and may be a step-up type. For example, in addition to a battery as a power source for driving a headlight or a wiper as a vehicle auxiliary device, a battery serving as a power source for an electric power steering or the like used at a higher voltage than those auxiliary devices is provided. It is good also as a power supply device which boosts and uses.

The following technical idea (invention) can be understood from the embodiment.
-In invention of Claim 3, the battery connected to the said secondary side is a power supply of auxiliary machines, such as a headlamp.

The block diagram which shows the structure of one Embodiment. The block diagram which shows the structure of a prior art. The block diagram which shows the structure of another prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Power supply device, 12 ... Transformer, 13 ... Converter, 14 ... Battery, 16a, 16b ... Output terminal.

Claims (3)

  A power supply apparatus comprising: a converter in which a primary side and a secondary side are insulated by a transformer; and a battery connected to the secondary side of the converter, wherein the output terminal on the secondary side and the battery are connected in series.   The power supply device according to claim 1, wherein the converter is a step-down converter.   The power supply device according to claim 1 or 2, wherein the primary-side power supply is a vehicle drive power supply.

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