JP2002095255A - Dc-dc converter for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure capable of suppressing generation of radio noise radiated from a DC-DC converter for automobile to the outside. SOLUTION: A circuit component 50b forming the DC-DC converter for automobile is formed on a cooling body 50h and is structured so as to be covered with the cooling body 50h and a magnetic cover 50i to suppress the radio noise of an AM broadcasting band from being radiated to the outside by the cover 50i.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC-DC converter for an automobile, which charges an auxiliary DC power supply from a main DC power supply that supplies an electric motor for driving a vehicle via an inverter.

[0002]

2. Description of the Related Art FIG. 6 shows a typical configuration of an electric system of an electric vehicle as this kind of vehicle. , An inverter 3, a motor for driving the vehicle that is variably controlled by the inverter 2, an auxiliary battery 4 as an auxiliary DC power supply, and a DC-DC converter 5 for charging the auxiliary battery 4 from the main DC power supply 1. Here, one terminal (usually a negative terminal) of the auxiliary battery 4 is connected to the vehicle body 6 of the electric vehicle.

FIG. 7 is a diagram showing an example of a detailed circuit configuration of the DC-DC converter 5 shown in FIG. 6, and this circuit configuration is referred to as a dual forward circuit system.

In FIG. 7, 51a and 51b are semiconductor switches, 52 is an insulating transformer, 51c and 51d are return diodes of the exciting current of the insulating transformer 52, 53a and 53b are rectifying diodes, 54 is a smoothing reactor, and 55 is a capacitor. , 56 are input filter circuits.

In the DC-DC converter shown in FIG.
The semiconductor switches 51a and 51b are high-frequency switched to generate a high-frequency AC voltage in the primary winding 52a of the insulating transformer 52, and the high-frequency AC voltage induced in the secondary winding 52b of the insulating transformer 52 is converted to a rectifier diode 53a. , 53b
The DC voltage is converted into a DC voltage by the smoothing reactor 54 and the capacitor 55, and the auxiliary battery 4 is charged by the DC voltage.

Reference numerals 15p and 15n denote power supply lines from the main DC power supply 1 to the DC-DC converter 5, respectively.
Reference numeral 5n denotes a power supply line from the DC-DC converter 5 to the auxiliary battery 4, where p denotes a plus side and n denotes a minus side.

FIG. 8 is an operation waveform diagram of each part of the DC-DC converter 5 shown in FIG.

FIG. 8A shows a semiconductor switch 5.
1a, 51b ON / OFF operating state, (b) voltage of semiconductor switches 51a, 52b, (c) current of semiconductor switches 51a, 52b, (d) voltage of primary winding 52a of insulating transformer 52 , (E) shows the current of the primary winding 52a of the insulation transformer 52, and (f) shows the current of the secondary winding 5a of the insulation transformer 52.
2b, (g) is the current of the rectifier diode 53a,
(H) is the current of the rectifier diode 53b, (i) is the current of the smoothing reactor 54, (j) is the voltage of the capacitor 55, the broken line in the drawing is the average output voltage [Vo], (k) is the output current, The dashed line in the figure indicates the average output current [Io],
(L) is the input current, and the broken line in the figure indicates the average input current [I
i].

That is, in FIG. 8, the semiconductor switches 51a and 51b are turned on at time T1, turned off at time T2, and turned on again at time T3. At this time, time T1
The period up to T3 is a switching cycle, and the output voltage control controls the ON period of the semiconductor switches 51a and 51b between times T1 and T2. Between times T2 and T4, a reset period of the magnetic flux of the insulating transformer 52 after the semiconductor switches 51a and 51b are turned off, and the reset is completed at time T4.

In the DC-DC converter shown in FIG.
Insulation transformer 52, smoothing reactor 54, capacitor 55
The semiconductor switches 51a, 51a,
51b is switched at a high frequency of the 100 kHz class.

As can be seen from the waveforms of the respective parts shown in FIG. 8, (1) the input current, the smoothing reactor current, and the output current have a ripple current of the switching frequency. (2) A comb-like current having the switching frequency flows through the semiconductor switch and the rectifier diode. (3) The alternating voltage of the switching frequency is applied to the insulating transformer. That is, the radiation noise due to the voltage and current shown in FIG. 8 is different from the high frequency noise based on the switching frequency,
There are high-frequency noises caused by transient changes in voltage and current when semiconductor switches and rectifier diodes are turned on and off. At this time, the switching frequency is 10
Since the frequency is about 0 kHz, the high frequency noise due to the switching frequency affects the frequency range of the AM broadcast band, and the high frequency noise caused by the turn-on and turn-off of the semiconductor switch and the rectifier diode is of the order of several MHz. Affects the frequency domain.

[0012]

[0005] This type of automotive DC
One of the problems in the DC converter is the reduction of the above-mentioned radio noise.

FIG. 9 is a circuit diagram illustrating the generation of radio noise from the DC-DC converter 5 shown in FIG.

In FIG. 9, arrows indicate generation of conduction and radiation noise due to harmonic current flowing through the feeder line 15p, arrows indicate generation of radiation noise due to changes in voltage and current of the semiconductor switch 51a and its circuit, and arrows indicate insulation transformer. Vessel 52
Of the rectifier diode 53a and its circuit, the generation of radiated noise due to changes in voltage and current, the arrow indicates the generation of radiated noise due to the leakage magnetic flux of the smoothing reactor 54, and the arrow indicates the power supply line 45p. The generation of conduction and radiation noise due to the flowing harmonic current is shown.

As is apparent from FIG. 9, the noise generated by the DC-DC converter 5 includes the radiation noise from the feeder line and
It is roughly classified into noise due to electromagnetic radiation from a switching circuit including an insulating transformer. Here, the noise to the AM broadcast band is particularly large as electromagnetic noise due to magnetic flux leakage from the insulating transformer and the smoothing reactor indicated by the arrow.

Here, FIG. 10 shows a conventional schematic structural example of the DC-DC converter 5 shown in FIG.

In FIG. 10, DC is placed in a metal container 50a.
-Circuit components 50b forming the DC converter 5 (circuit components shown in FIG. 7 and a control device not shown)
And a metal cover 50c is fixed to the upper surface of the metal container 50a by a screw 50d. Further, a cooling unit 50e is provided below the metal container 50a in the drawing, and the cooling unit 50e has a cooling fin structure in the case of air cooling and a water cooling plate structure in the case of water cooling. further,
The power supply lines 15p and 15n and the power supply lines 45p and 45n are drawn out of the metal container 50a via rubber bushes 50f and 50g, respectively.

That is, in the structural example shown in FIG. 10, aluminum or its alloy is mainly used for the metal container 50a for weight reduction. As a result, high-frequency electromagnetic noise is radiated from the circuit components contained in the metal container 50a, as shown in FIG. FIG. 11 shows these noise generation situations.

In FIG. 11, the same arrow numbers as those in FIG. 9 indicate the same noise generation, the arrow indicates electromagnetic radiation noise passing through the metal cover 50c of the DC-DC converter 5, and the arrow indicates passing through the metal container 50a. 3 shows the obtained electromagnetic radiation noise.

That is, in the example of the structure of the DC-DC converter 5 shown in FIG.
Radiation noise due to magnetic flux leakage from the smoothing reactor 54 may cause a problem. As a countermeasure against this, a thicker metal container 50a made of aluminum or an alloy thereof is used. However, this measure has resulted in an increase in the weight and cost of the entire DC-DC converter for automobiles.

An object of the present invention is to provide a DC-DC converter for an automobile which solves the above problems.

[0022]

According to a first aspect of the present invention, there is provided a vehicle DC-DC converter for charging an auxiliary DC power supply from a main DC power supply for supplying a motor for driving a vehicle via an inverter. The DC converter is formed on a non-magnetic cooling body, and the DC-DC converter is covered with the cooling body and a magnetic cover.

The second invention is a vehicle D according to the first invention.
In the C-DC converter, the vehicle DC-DC
When the converter is covered with the cooling body and the magnetic cover, a part or the entire periphery of the portion where the cover and the cooling body are in contact with each other has a structure that prevents the electromagnetic radiation from the DC-DC converter from going straight. It is characterized by.

According to a third aspect of the present invention, in the DC-DC converter for a vehicle according to the first or second aspect, the cover is an iron plate.

According to a fourth aspect of the present invention, in the DC-DC converter for an automobile according to the first or second aspect, the cooling body is made of a material mainly containing aluminum, magnesium, or an alloy thereof.

According to the present invention, the noise generated by a DC-DC converter for automobiles is large in noise to an AM broadcast band caused by radiated magnetic flux of a switching frequency generated from a circuit component in the DC-DC converter. The electromagnetic waves generated from the components go straight and this DC-
It has been made paying attention to radiation to the outside of the DC converter, and that magnetic metal can absorb a large amount of electromagnetic waves.

[0027]

FIG. 1 is a schematic structural view of a DC-DC converter for a vehicle showing a first embodiment of the present invention, and has the same components as those of the conventional structural view shown in FIG. Are given the same numbers.

That is, in the structure shown in FIG.
The circuit component 50b is mounted on 0h, and the periphery of the circuit component 50b is covered with a magnetic cover 50i as shown in the figure. The cover 50i is fixed to the cooling body 50h via a screw 50k at a mounting portion 50j. Feeding line 15
p, 15n, 45p, 45n are rubber bushes 50g, 5
It is pulled out from the cover 50i through 0f.

Therefore, in the structure shown in FIG. 1, since the periphery of the circuit component 50b is covered with the magnetic cover 50i such as iron, the electromagnetic radiation noise indicated by the arrow in FIG. 11 is greatly reduced. You. Also, the electromagnetic radiation noise of the arrows shown in FIG. 11 is almost the same as that of the conventional structure.

FIG. 2 is a partial detailed structural view when the cover 50i shown in FIG. 1 is attached to the cooling body 50h, and the same components as those in FIG. 1 are denoted by the same reference numerals.

The cover 50i and the cooling body 50h shown in FIG.
When the electromagnetic radiation noise from the circuit component 50b is very large, a part of the electromagnetic radiation noise is converted into a DC-current through the gap (A in the drawing) between the cover 50i and the cooling body 50h. Leakage may occur outside the DC converter, and this leakage electromagnetic radiation noise may cause radio noise.

FIG. 3 shows a third embodiment of the present invention for reducing the above-mentioned leakage electromagnetic radiation noise.
1 shows a schematic structural diagram of a DC converter, and the same components as those in FIG. 1 are denoted by the same reference numerals.

In FIG. 3, reference numeral 50l denotes a cover corresponding to the cover 50i shown in FIG. 1, and 50m denotes a mounting portion corresponding to the mounting portion 50j shown in FIG.

That is, the difference between the structure shown in FIG. 3 and the structure shown in FIG. 1 is that the mounting portion 50 of the cover 50i in FIG.
j is a planar structure, whereas in FIG.
To cover the cooling body 50h, and fastened with screws 50n.

FIG. 4 is a partially detailed structural view when the cover 50l shown in FIG. 3 is attached to the cooling body 50h.
The same components as those described above are denoted by the same reference numerals.

That is, the mounting portion 50m of the cover 50l is bent as shown in the figure to cut off the passage of the electromagnetic radiation (arrows shown) from the circuit component 50b.

FIG. 5 is a schematic configuration diagram of a DC-DC converter for an automobile according to a third embodiment of the present invention.
The same components as those in FIG. 1 or 3 are denoted by the same reference numerals.

That is, the cover 50p basically has the structure shown in FIG.
Has the same configuration as that of the cover 50i shown in FIG.
1) has the same structure as that of FIG. 1. Therefore, the mounting portion 50q has the same structure as the mounting portion 50j of FIG. 1, and is fixed with screws 50s. Further, a portion (part B in the drawing) where the electromagnetic radiation noise due to the leakage magnetic flux is large has the same structure as that of FIG. 3, and therefore, the mounting portion 50r has the same structure as the mounting portion 50m of FIG.

[0039]

According to the present invention, the circuit components of the DC-DC converter for an automobile are mounted on a cooling body, and the circuit components are covered with a magnetic cover, and the cover and the mounting portion to the cooling body are formed of a circuit. Since the structure is such that the magnetic flux leakage from the components is blocked, the following effects (1) to (3) are obtained. (1) Radiation noise from a DC-DC converter for automobiles is greatly reduced. (2) Since the iron plate material can be used for the cover, the weight can be reduced. (3) Cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention;
Schematic structure diagram of DC converter

FIG. 2 is a partially detailed structural view of FIG. 1;

FIG. 3 shows an automotive DC-DC converter according to a second embodiment of the present invention.
Schematic structure diagram of DC converter

FIG. 4 is a partial detailed structural view of FIG. 3;

FIG. 5 shows a third embodiment of the present invention.
Schematic structure diagram of DC converter

FIG. 6 is a configuration diagram of an electric system of the electric vehicle.

FIG. 7 is a detailed circuit configuration diagram of an automotive DC-DC converter.

FIG. 8 is a waveform chart for explaining the operation of FIG. 7;

FIG. 9 is a circuit diagram illustrating the operation of FIG. 7;

FIG. 10 is a schematic structural diagram of a conventional automotive DC-DC converter.

11 is a structural diagram illustrating the operation of FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 main DC power supply 2 inverter 3 electric motor 4 auxiliary battery 5 DC-DC converter 6 vehicle body 15
p, 15n, 45p, 45n: power supply line, 50a: metal container, 50b: circuit component, 50c, 50i, 50
1, 50p ... cover, 50d, 50k, 50n, 50
s, 50t: screw, 50e, 50h: cooling body, 50g,
50f rubber bush, 50j, 50m, 50q, 50
r ... Mounting part.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Fumito Takahashi 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Hisashi Iwami 1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-ku, Kanagawa Prefecture No. 1 Fuji Electric Co., Ltd. F term (reference) 5H115 PA04 PG04 PI15 PI16 PI29 PI30 PU08 PV02 PV09 UI40 5H730 AA02 AS17 BB24 BB57 DD04 EE02 EE08 EE10 ZZ01 ZZ09

Claims (4)

[Claims] 1. An automotive DC-DC converter for charging an auxiliary DC power supply from a main DC power supply that supplies an electric motor for driving a vehicle via an inverter, wherein the DC-DC converter for an automobile is provided on a non-magnetic cooling body. Wherein the DC-DC converter is covered with the cooling body and a magnetic cover.
C converter. 2. The automotive DC-DC converter according to claim 1, wherein when the automotive DC-DC converter is covered with the cooling body and a magnetic cover, the cover contacts the cooling body. A DC-DC converter for automobiles, wherein a part or the entire periphery of the part is structured to prevent the electromagnetic radiation from the DC-DC converter from traveling straight. 3. The DC-DC converter according to claim 1, wherein the cover is an iron plate.
-DC converter. 4. The automotive DC-DC converter according to claim 1, wherein the cooling body is made of a material containing aluminum, magnesium, or an alloy thereof as a main component. -DC converter.