JP2000295836A - Noise suppression structure of power supply equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress noise without increasing the size and cost of a power supply equipment by making an insulating sheet interposed between a semiconductor switching element and a heat radiation fin from the material having a low permittivity and a high dielectric loss. SOLUTION: An insulating sheet 51 interposed between a semiconductor switching element 1 and a heat radiation fin 2 is made of the material having a low permittivity and a high dielectric loss. The permittivity of the insulating sheet 51 forms parasitic capacitance, however, the low permittivity hardly allows high frequency current to flow and the high dielectric loss increases the resistance against current, In other words, the insulating sheet 51 can be deemed as a series circuit of a capacitor and a resistor. When the semiconductor switching element 1 makes an on and off operation, there is a potential difference generated between the semiconductor switching element 1 and the heat radiation fin 2, and noise current is caused to flow through the insulating sheet 51, the parasitic capacitance 511, and the resistor 512. However, the noise current is consumed as heat by the resistor 512 and thereby it can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a noise suppression structure for a power supply device.

[0002]

2. Description of the Related Art FIG. 3 shows a first conventional power supply device.
In this example, the radiation fin 2 is connected to the ground via the housing 4, and an insulating sheet 53 is inserted between the semiconductor switch element 1 and the radiation fin 2. In the case of this structure, the parasitic capacitance 53 is provided between the semiconductor switch element 1 and the radiation fin 2 due to the dielectric constant of the insulating sheet 53.
1 is formed. FIG. 4 shows a second conventional example of the power supply device. This is because a parasitic capacitance 531 is provided between the semiconductor switch element 1 and the radiation fin 2 due to the dielectric constant of the insulating sheet 53.
Are formed, and a parasitic capacitance 6 is also formed between the radiation fin 2 and the housing 4.

[0003]

When the semiconductor switch element 1 is turned on and off, a potential difference is generated between the semiconductor switch element 1 and the radiation fin 2 in FIG. Element 1 and radiation fin 2
, And between the radiating fin 2 and the housing 4, and a noise current flows through the parasitic capacitances 531 and 6. This noise current affects other electronic devices connected to the input power supply or the output load, such as malfunction. In order to suppress this noise, a noise filter 7 composed of a reactor, a capacitor, and the like is conventionally provided, but this causes an increase in the size and cost of the device. Therefore, an object of the present invention is to suppress noise without increasing the size and cost of a power supply device.

[0004]

According to a first aspect of the present invention, an insulating sheet inserted between a semiconductor switch element and a radiating fin has a low dielectric constant and a high dielectric loss characteristic. It consists of the material which has. In the second invention, a material having a low dielectric constant and a high dielectric loss characteristic is inserted between the heat radiation fin and the housing. In the third invention, the insulating sheet inserted between the semiconductor switch element and the heat radiation fin is made of a material having a low dielectric constant and a high dielectric loss characteristic. A material having a high dielectric loss characteristic with a dielectric constant is inserted. In this way, the noise current flowing through the parasitic capacitance is consumed by the resistance of the material having a low dielectric constant and a high dielectric loss characteristic. As a result, the noise current is reduced, and the influence of malfunction on other electronic devices connected to the input power supply or the output load is reduced.

[0005]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention. As is clear from the drawing, this example is different from the insulating sheet 53 shown in FIG. 3 in that the insulating sheet 53 has a low dielectric constant and a high dielectric loss characteristic. Parasitic capacitance is formed by the dielectric constant of the insulating sheet 51. Since the parasitic capacitance is low, a high-frequency current is difficult to flow, and a high dielectric loss means a large resistance value to the current. That is, the insulating sheet 51 can be regarded as a series circuit of a capacitor and a resistor, as shown in FIG. Therefore, when the semiconductor switch element 1 is turned on and off, a potential difference is generated between the semiconductor switch element 1 and the radiation fin 2, and noise current flows through the parasitic capacitance 511 and the resistance 512 of the insulating sheet 51, but the resistance 51
2 is consumed as heat, and the noise current is reduced.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention. The difference from FIG. 4 is that a material 52 having a low dielectric constant and a high dielectric loss characteristic is inserted between the heat radiation fin 2 and the housing 4. In this configuration, when the semiconductor switch element 1 is turned on and off, a potential difference is generated between the semiconductor switch element 1 and the radiating fin 2 and between the radiating fin 2 and the housing 4, and the noise current is reduced by the insulating sheet 5.
3 parasitic capacitance 531, low dielectric constant / high dielectric loss material 52
Flows through the parasitic capacitance 521 and the resistance 522 and the parasitic capacitance 6 between the low-permittivity / high-dielectric loss material 52 and the housing 4, but is consumed as heat by the resistance 522, and the noise current is reduced. Will be.

In FIG. 2, an insulating sheet 53 is inserted between the semiconductor switch element 1 and the radiation fins 2. However, as in the case of FIG. 1, a low dielectric constant, high dielectric loss material is used instead of the insulating sheet 53. Needless to say, the insulating sheet 51 can be used.

[0008]

According to the present invention, since the noise current can be reduced by using a material having a low dielectric constant and a high dielectric loss characteristic, the device is constituted by a reactor or a capacitor which causes an increase in size and cost of the device. This provides an advantage that the noise filter can be eliminated or reduced in size.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a first conventional example.

FIG. 4 is a configuration diagram showing a second conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor switch element, 2 ... Heat radiation fin, 3 ... Board,
4 ... housing, 51, 52 ... low dielectric constant, high dielectric loss material,
53: insulating sheet, 511, 521, 531, 6: parasitic capacitance, 512, 522: resistance due to dielectric loss, 7 ...
Noise filter.

Claims (3)

[Claims] 1. A power supply device in which a radiating fin for cooling a semiconductor switch element is provided via an insulating sheet and is housed in a housing, wherein the insulating sheet has a low dielectric constant and a high dielectric loss characteristic. A noise suppressing structure for a power supply device, comprising a material. 2. A power supply device in which a radiating fin for cooling a semiconductor switch element is provided via an insulating sheet and is housed in a housing, wherein a low dielectric constant and a high dielectric constant are provided between the radiating fin and the housing. A noise suppression structure for a power supply device, wherein a material having a dielectric loss characteristic is inserted. 3. A power supply device in which a heat radiation fin for cooling a semiconductor switch element is provided via an insulating sheet and is housed in a housing, wherein the insulating sheet has a low dielectric constant and a high dielectric loss characteristic. A noise suppression structure for a power supply device, comprising a material, wherein a material having a low dielectric constant and a high dielectric loss characteristic is inserted between the radiation fins and the housing.