JP2002165453A - Step-down dc-dc converter device for vehicle having two batteries - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a step-down DC-DC converter device for a two-battery vehicle, capable of outputting large-current while suppressing increases in power loss, temperature rise and electromagnetic noise emission in a rectifier circuit. SOLUTION: In this step-down DC-DC converter device for two-battery equipped vehicle, a rectifier diode element is fixed integrally with a blat conductor wire forming a secondary coil of a step-down transformer. For this step- down DC-DC converter device, thus it is possible to suppress power loss, heat generation and electromagnetic wave noise in the vicinity of the rectifier diode elements 81, 82 subjected to overheating and to facilitate assembly.

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 for a two-battery mounted vehicle.

[0002]

2. Description of the Related Art In an electric vehicle including a hybrid vehicle, a dual power supply system in which a driving motor is supplied from a high-voltage main battery and various auxiliary units are supplied from a low-voltage auxiliary battery is useful in various points. .

[0003] Further, even in a normal internal combustion locomotive, due to various factors, there is a tendency to mount a dual-battery power supply system having both a high-voltage main battery and an auxiliary battery for supplying a low-voltage load.

In this dual power supply type vehicle power supply system, the auxiliary battery is reduced in capacity, and when the power of the auxiliary battery becomes insufficient, assist power is transmitted from the main battery through a step-down DC-DC converter in various ways. Is a reasonable choice.

[0005] This step-down DC-DC converter device comprises:
It is usually composed of an inverter circuit that forms a single-phase AC voltage from an input DC voltage, a transformer that transforms this single-phase AC voltage, a rectifier circuit that rectifies the output voltage of this transformer, and a smoothing circuit that smoothes the rectified voltage. However, the transformer and the rectifier circuit are usually configured by a single-phase full-wave rectification system. In this single-phase full-wave rectification method, the transformer has a pair of secondary coils wound in the same direction and connected in series, and the rectification circuit is composed of a pair of rectification elements. The connected middle point is grounded or used as an output terminal to the smoothing circuit.

[0006]

However, in the above-described dual power supply system for a vehicle, the terminal voltage of the main battery is set to a high voltage of several hundred volts for various reasons, while the auxiliary battery is adapted to the conventional battery specifications. Usually, it is preferable to use 12V.

For this reason, the secondary current of the step-down transformer of the step-down DC-DC converter circuit becomes extremely large. As a result, the loss of the rectifier diode element constituting the rectifier circuit for rectifying the secondary current (resistance loss + forward direction) Voltage drop loss)
Increase of the rectifier diode element and the DC resistance due to an increase in the resistance loss of the wiring between the rectifier circuit and the secondary coil and an increase in the contact resistance loss of the connection portion between the secondary coil and the rectifier circuit.
-Decrease in DC conversion efficiency is a serious problem.

More specifically, when a silicon diode is used as a rectifier diode element, the forward voltage drop is about 0.75 V, and the voltage drop of various resistance components around the rectifier circuit is taken into consideration. Then
The rectifier circuit itself causes a DC voltage drop of about 1 V or more. Output voltage is more than 10 V, and 1.3
It is understood that when transmitting kW (100 A) (for example, when starting the engine with an auxiliary battery), a power loss of about 100 W occurs in or near the rectifier diode element.

Of course, it is possible to attach a large cooling fin to the rectifier diode element or to cool the rectifier diode element with a cooling fan. However, the required space is increased and the secondary coil of the transformer and the rectifier diode are increased. The wiring resistance increases due to the increase in the wiring distance between the elements.

As described above, a single-phase full-wave rectifier circuit using two diode elements is usually used as the rectifier circuit.
The step-down transformer has a pair of secondary coils. Half-wave currents of different single-phase alternating currents flow through conductor portions of the secondary coil (hereinafter, also referred to as “outer core conductor portions”) from the core of the step-down transformer to the rectifier diode elements.

As a result, this half-wave current contains a large amount of harmonic current, and in combination with the large amount of current, there is a problem that electromagnetic noise generated by the core outer conductor is large. Note that, of the secondary coil of the step-down transformer, a portion wound around the core of the step-down transformer (also referred to as a conductor in the core) is shielded by the core, so that the generated electromagnetic wave noise is small.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a step-down type for a two-battery mounted vehicle capable of outputting a large current while suppressing power loss, temperature rise, and increase in electromagnetic wave noise radiation of a rectifier circuit. It is an object of the present invention to provide a DC-DC converter device.

[0013]

A step-down type D according to claim 1
The C-DC converter device includes a step-down transformer, an inverter circuit that intermittently controls a DC voltage supplied from a main battery to apply a single-phase AC voltage to a primary coil of the step-down transformer, and a secondary coil of the step-down transformer. A two-battery mounted type including a rectifier circuit having a rectifier diode element connected in series and rectifying a secondary voltage of the transformer, and a smoother circuit for smoothing a rectified voltage output from the rectifier circuit and charging an auxiliary battery. In the step-down DC-DC converter device for a vehicle, an anode electrode and a cathode electrode of the rectifier diode element are individually formed on a pair of main surfaces of the rectifier diode element, and one of the two main surfaces of the rectifier diode element is , Which is joined to the main surface of the end portion of the secondary coil of the transformer made of a rectangular conductor wire, covered with a resin mold, and integrated. It is characterized by having been.

That is, in the step-down DC-DC converter device for a two-battery mounted vehicle according to the present invention, the rectifying diode element is fixed integrally with the rectangular conductor wire forming the secondary coil of the step-down transformer.

The rectifying diode element is constituted by a semiconductor chip having one main surface serving as an anode electrode surface and the other main surface serving as a cathode electrode surface. A surface other than the surface can be coated with an insulating coating film such as a resin. Further, the anode electrode surface and the cathode electrode surface of the semiconductor chip may be covered with a thin metal plate or a metal layer. This metal plate or metal layer can be preferably formed by a CVD method or a PVD method. It is preferable that the insulating coating film covers a peripheral portion of the metal plate or the metal layer. The anode electrode surface or cathode electrode surface of the rectifier diode element and the main surface of the rectangular conductor wire forming the secondary coil can be preferably joined via a solder layer, but a conductive adhesive can also be used. .
The solder layer can absorb a step between the insulating coating film and the metal plate or metal layer by melting or plastic deformation.

According to the present invention, the following effects can be realized. First, a secondary coil is manufactured separately from a conventional secondary coil, and the end of the secondary coil is mounted on a diode module incorporating a rectifying diode element chip. Compared to fastening to the provided terminal, it is possible to reduce the total wiring distance in the core outside conductor portion and the diode module which is a portion outside the core of the secondary coil, and furthermore, the secondary coil and the diode module Can reduce the contact loss between the wires, thereby reducing the resistance loss and the leakage inductance of this wiring portion, reducing the thermal effect on the rectifier diode element, and improving the power conversion efficiency. be able to.

Next, according to the present invention, the secondary coil is manufactured separately from the conventional one, and the end of the secondary coil is fastened to the terminal provided on the diode module including the rectifier diode element chip. In comparison, since the heat transfer resistance between the rectifier diode element and the core outer conductor part outside the core conductor part that is the core inner part of the secondary coil can be reduced, the rectifier diode element Large heat (especially heat generated due to the forward voltage drop) can be satisfactorily transmitted to the conductor portion in the core of the secondary coil and radiated.

Further, according to the present invention, since the wiring between the conductor portion in the core of the secondary coil and the rectifier diode element can be shortened, a harmonic electromagnetic wave which generates a large half-wave current flowing through the wiring inductance is generated. Noise can be reduced.

According to a second aspect of the present invention, in the step-down DC-DC converter device for a two-battery mounted vehicle according to the first aspect, the other of the two main surfaces of the rectifier diode element is connected to the rectifier circuit. It is characterized in that it is joined to a bus bar serving as an output terminal or a ground terminal and covered with a resin mold.

According to the present invention, the rectifying diode element comprises:
Since it is directly in contact with the main surface of the bus bar, the same effect as described above can be obtained on the rectifier diode element side. Further, since the rectifier circuit and the secondary coil are integrated, the secondary coil In addition, the work of attaching and connecting the rectifier circuit can be simplified.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Step-down DC-D of the present invention
Preferred embodiments of the C converter device will be described with reference to the following embodiments.

[0022]

[Embodiment 1] A step-down type D for a two-battery mounted vehicle according to the present invention.
One embodiment of the C-DC converter device will be described with reference to the circuit diagram shown in FIG. (Circuit configuration) This step-down DC-DC converter device
This is for converting the voltage from the main battery 1 for storing the traveling energy of the electric vehicle to the auxiliary battery 2 for supplying power to the auxiliary equipment and the control device, and supplying power. 3 is a smoothing capacitor, and 4 is four MOSs. Inverter circuit having transistors connected in a bridge, 6 is a step-down transformer, 8 is a rectifier circuit including two rectifying diode elements 81 and 82 for full-wave rectification, 9 is a choke coil 10 and a smoothing capacitor 11
, A reference numeral 12 denotes an integrated control circuit. The control circuit 12 performs negative feedback control of the duty ratio of the PWM voltage of the inverter circuit based on the voltage of the auxiliary battery 2.

The main battery 1 applies a high voltage (for example, 3 V) to the positive and negative DC input terminals of the inverter circuit 4 and the smoothing capacitor 3.
00V), and the inverter circuit is, for example, 20 kHz.
A single-phase PWM voltage is applied to the primary coil 60 of the transformer 6 at the carrier frequency of. The transformer 6 has a pair of secondary coils 61 and 62 connected in the same direction. The middle point of the secondary coils 61 and 62 supplies power to the auxiliary battery 2 through the choke coil 10. The other end of 62 is individually connected to the cathode electrodes of rectifier diode elements 81 and 82, and the anode electrodes of rectifier diode elements 81 and 82 are grounded. The smoothing capacitor 11 is connected in parallel with the auxiliary battery 2. The rated voltage of auxiliary battery 2 is 12V.

The operation of the step-down DC-DC converter circuit is well known and will not be described.

FIG. 2 shows a horizontal sectional view of the step-down transformer 6 and the rectifier circuit 8.

Reference numeral 63 denotes a ferrite core; 631, a central pillar; and 632, a peripheral wall. The central column 631 and the peripheral wall 632 are connected by a bottom plate and a top plate (not shown) to form a closed magnetic circuit. The ferrite core 63 is configured by combining two members. In the peripheral wall portion 632, three openings are formed, and in FIG.
One opening is used for taking out the primary coil 60, and the lower opening is used for taking out the secondary coils 61 and 62.

As shown in FIGS. 3 and 4, the secondary coils 61 and 62 are made of resin-coated copper rectangular conductors.
The core 63 is accommodated in a cylindrical coil groove between the central column 631 and the peripheral wall 632. Secondary coils 61, 6
2 are wound substantially one turn, the secondary coil 61 is superimposed on the secondary coil 62, and the primary coil 60 is wound on the secondary coil 61 for a predetermined turn.

Reference numeral 611 denotes an outgoing conductor (portion entering the core 63) of the secondary coil 61; 621, a return conductor (portion coming out of the core 63) of the secondary coil 61; 622 is a return conductor of the secondary coil 61 (a part coming out of the core 63).

In this embodiment, as shown in FIG. 2, the return conductor 612 of the secondary coil 61 and the outgoing conductor 621 of the secondary coil 62 are arranged one above the other. The outgoing conductor 611 and the return conductor 622 of the secondary coil 61 are individually arranged.

Next, the rectifier circuit 8 will be described below.

Rectifier diode element 8 forming rectifier circuit 8
As shown in FIGS. 3 and 4, the upper main surface (cathode electrode surface) of each of the first and second conductors 82 is a lower main surface 6110 of the outgoing conductor 611 of the secondary coil 61 and the return conductor of the secondary coil 62. 6
22 is soldered to the lower main surface 6220. As shown in FIG. 2, the soldering points are the secondary coils 61,
This is the portion immediately after the core 62 has exited. Of course, the insulating coating resin on the surfaces of the secondary coils 61 and 62 has been removed at this portion.

As shown in FIGS. 3 and 4, the lower main surfaces (anode electrode surfaces) of the rectifier diode elements 81 and 82 are soldered to the upper main surfaces of the bus bars 14 and 15 forming a ground line. The busbars 14 and 15 are fastened by screws 17 to a base plate 13 made of a thick aluminum plate which also serves as a bottom plate of the circuit case.

The rectifier diode elements 81 and 82 are covered with a resin covering portion 83 formed by a resin mold. Therefore, the resin covering portion 83 is
1, 62 outgoing conductors 611, 621, return conductor 612,
622 and a part of each of the bus bars 14 and 15 are covered and integrated. 141 is a fastening hole of the bus bar 14 protruding from the resin covering portion 83; 151 is a fastening hole of the bus bar 15 protruding from the resin covering portion 83; This fastening hole communicates with the fastening hole of the outgoing conductor 621 of the secondary coil 62 located below. 3 and 4, reference numeral 17 denotes a heat conductive sheet interposed between the bus bars 14, 15 and the base plate 13.

The rectifier circuit 8 of this embodiment described above
Is substantially integral with the secondary coils 61 and 62, so that the above-described effects can be obtained.

Further, the secondary coils 61 and 62 and the rectifier diode elements 81 and 82 can be completely fixed only by fastening the bus bars 14 and 15 to the base plate 13, thereby facilitating attachment and connection work. The rectifier diode elements 81 and 82 can also radiate heat to the base plate 13 through the bus bars 14 and 15 satisfactorily.

[0036]

[Embodiment 2] A step-down type D for vehicles with two batteries according to the present invention
FIG. 5 shows another embodiment of the C-DC converter device, and FIG. 6 shows a vertical sectional view of the rectifier circuit 8 'at the position of the line AA in FIG.

FIG. 5 shows a rectifying diode element 8 in FIG.
Only the directions of 1,82 are reversed.

In this embodiment, the secondary coils 612 and 621
Are grounded, and the outgoing conductor 622 of the secondary coil 62 and the return conductor 611 of the secondary coil 61 are connected to the choke coil 10.

Also in this embodiment, the control circuit board 8 '
Is formed integrally with the secondary coils 61 and 62,
It is clear that the same effect as in the first embodiment can be obtained.

[Brief description of the drawings]

FIG. 1 is a step-down DC for a two-battery mounted vehicle according to the present invention.
FIG. 3 is a circuit diagram showing one embodiment of a DC converter device.

FIG. 2 is a horizontal sectional view of the rectifier circuit and the step-down transformer shown in FIG.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB of FIG. 2;

FIG. 5 is a step-down DC for a two-battery mounted vehicle according to the present invention;
FIG. 10 is a circuit diagram showing another embodiment of the DC converter device.

6 is a vertical sectional view of the rectifier circuit of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main battery 2 Auxiliary battery 4 Inverter circuit 6 Step-down transformer 8 Rectifier circuit 9 Smoothing circuit 10 Choke coil 61 Secondary coil 62 Secondary coil 81 Rectifier diode element 82 Rectifier diode element

Claims (2)

[Claims] A step-down transformer, an inverter circuit for intermittently controlling a DC voltage supplied from a main battery to apply a single-phase AC voltage to a primary coil of the step-down transformer, and a series connection to a secondary coil of the step-down transformer. A rectifier circuit having a rectifier diode element for rectifying a secondary voltage of the transformer, and a smoothing circuit for charging an auxiliary battery by smoothing a rectified voltage output from the rectifier circuit. In the step-down DC-DC converter device for use, an anode electrode and a cathode electrode of the rectifier diode element are individually formed on a pair of main surfaces of the rectifier diode element, and one of the two main surfaces of the rectifier diode element is: It is joined to the main surface of the end of the secondary coil of the transformer made of a rectangular conductor wire, covered with a resin mold, and integrated. Two battery-mounted vehicle buck DC-D, wherein the door
C converter device. 2. The step-down DC-DC converter device for a two-battery mounted vehicle according to claim 1, wherein the other of the two main surfaces of the rectifier diode element forms an output terminal or a ground terminal of the rectifier circuit. 2. A step-down DC-DC converter device for a two-battery mounted vehicle, wherein the step-down DC-DC converter device is mounted on a vehicle and covered with a resin mold.