Control board and control apparatus

1. Field of the Invention

The present invention relates to control boards having a pattern for a low-voltage circuit and a pattern for a high-voltage circuit and to control apparatuses including such control boards.

This application is based on Japanese Patent Application No. 2006-280010, the content of which is incorporated herein by reference.

2. Description of Related Art

Conventional car air conditioners operate by converting DC power supplied from a power supply into three-phase AC power with an inverter and supplying the three-phase AC power to a compressor. Recently, electric compressors with integrated inverters have been proposed (for example, see Japanese Unexamined Patent Application, Publication No. 2005-36773).

However, a car air conditioner including such a compressor undesirably causes significant noise because a control apparatus for controlling the compressor is often connected to both a low-voltage system (about 12V system, 24 V system or 36V system) and a high-voltage system (for example about 300 V system).

An object of the present invention is to provide a control board capable of noise reduction for use in a control apparatus connected to both a low-voltage system and a high-voltage system and a control apparatus including such a control board.

The present invention provides: a control board having a pattern for a low-voltage circuit, the pattern for the low-voltage circuit including a ground pattern connectable to a ground; a pattern for a high-voltage circuit, the pattern for the high-voltage circuit including a ground pattern; and at least one ground-connection land configured to connect the ground pattern of the low-voltage circuit and the ground pattern of the high-voltage circuit via at least one capacitor.

In the structure described above, the ground pattern of the low-voltage circuit of the control board can be grounded, so that the low-voltage circuit can operate at a stable frequency. In addition, the ground patterns of the high-voltage and low-voltage circuits can be connected via the capacitors to reduce noise on the high-voltage circuit side. Also, the low-voltage circuit and the high-voltage circuit can be electrically separated because the ground patterns thereof are connected via the capacitors.

The above control board may have one or more grounding lands configured to connect the ground pattern of the high-voltage circuit and the ground via one or more capacitors.

In this case, the ground pattern of the high-voltage circuit can be grounded via the capacitors, so that the high-voltage circuit can operate at a stable frequency.

In the control board described above, a ground-connection land may be disposed so that the capacitors are connected in parallel.

In this case, the ground patterns of the low-voltage and high-voltage circuits can be connected via the capacitors connected in parallel to ensure satisfactory frequency characteristics. In particular, noise covering a wide frequency band can be reduced by connecting capacitors having different frequency characteristics in parallel.

In the control board described above, the ground-connection land may also be disposed so that the capacitors are connected in series.

In this case, the ground patterns of the low-voltage and high-voltage circuits can be connected via the capacitors connected in series to ensure a sufficient withstand voltage.

In the control board described above, the ground-connection lands may be disposed at a plurality of positions, and the capacitors connected thereto may have frequency characteristics corresponding to a frequency band of noise to be reduced.

In this case, the characteristics of the capacitors connected to the ground-connection lands, including capacitance, can be changed according to the frequency band of noise to be reduced. Noise can therefore be reduced effectively in a target frequency band.

The control board according to the present invention is suitable for use in a control apparatus for drive control of a compressor, and more particularly, a control apparatus for a car air conditioner. The use of the control board allows for noise reduction in such a control apparatus.

The above aspects can be combined within the scope of the present invention.

The control board according to the present invention provides the advantage of noise reduction when used in a control apparatus connected to both a low-voltage system and a high-voltage system.

FIG. 1 is a block diagram of a car air conditioner according to an embodiment of the present invention;

FIG. 2 is a diagram of an example of a control board for use in a control apparatus according to an embodiment of the present invention;

FIG. 3 is a diagram of an example of an arrangement of lands for series connection of capacitors;

FIG. 4 is a graph showing an example of frequency characteristics of capacitors;

FIG. 5 is a graph showing another example of frequency characteristics of capacitors; and

FIG. 6 is a graph showing another example of frequency characteristics of capacitors.

A car air conditioner including a control board according to an embodiment of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram of a car air conditioner 1 according to this embodiment.

In FIG. 1 , the input side of a control apparatus 2 is connected to a high-voltage power supply 3 and a low-voltage power supply 4 . Specifically, the high-voltage power supply 3 is connected to the control apparatus 2 via high-voltage power lines L 1 , and the low-voltage power supply 4 is connected to the control apparatus 2 via low-voltage power lines L 2 . The output side of the control apparatus 2 is connected to a motor of a compressor 5 via three-phase power lines L 3 .

The level of voltage supplied via the high-voltage power lines L 1 is, for example, about 300 V. The level of voltage supplied via the low-voltage power lines L 2 is, for example, about 12 V or about 24 V.

In the car air conditioner 1 having the configuration described above, DC power is supplied from the high-voltage power supply 3 to the control apparatus 2 via the power lines L 1 , is converted into three-phase AC power by an inverter (not shown) in the control apparatus 2 , and is supplied to the motor of the compressor 5 via the three-phase power lines L 3 . Drive control of the inverter, for example, may be based on the known art.

Referring to FIG. 2 , the control apparatus 2 of the car air conditioner 1 includes a control board 10 having a low-voltage pattern (a pattern for a low-voltage circuit) configured to control the low voltage supplied via the power lines L 2 and a high-voltage pattern (a pattern for a high-voltage circuit) configured to control the high voltage supplied via the power lines L 1 .

The low-voltage and high-voltage patterns are formed in separate regions. In this embodiment, the low-voltage pattern is formed in a region A 1 , and the high-voltage pattern is formed in a region A 2 . Detailed patterns in the regions A 1 and A 2 are not illustrated.

In the control board 10 , the low-voltage circuit includes a ground pattern connectable to a ground. Specifically, the control board 10 has screw holes 11 a to 11 d for fastening the control board 10 to a casing (not shown), and at least one of them (the screw hole 11 a in this embodiment) is connected to the ground pattern of the low-voltage circuit. The control board 10 is fastened to the casing by inserting screws into the screw holes 11 a to 11 d and fixing them to the casing. The casing is connected to a ground of a car body when installed thereon, so that the ground pattern of the low-voltage circuit can be grounded via the screws and the casing.

The high-voltage circuit includes a ground pattern. The control board 10 has grounding lands 12 a and 12 b configured to ground the ground pattern of the high-voltage circuit via capacitors. These grounding lands 12 a and 12 b are used to connect the ground pattern of the high-voltage circuit to the screw holes that are not connected to the ground pattern of the low-voltage circuit, for example, the screw holes 11 c and 11 d , via the capacitors.

The ground pattern of the high-voltage circuit can thus be grounded via the capacitors by forming the grounding lands 12 a and 12 b . The capacitors can decrease rapid voltage fluctuations to reduce noise.

The patterns for the low-voltage and high-voltage circuits also have ground-connection lands 13 a and 13 b configured to connect the ground patterns thereof to each other via capacitors. The number of capacitors connected to the ground-connection lands 13 a and 13 b and the number of capacitors connected to the grounding lands 12 a and 12 b in FIG. 2 are merely examples and can be changed according to design specifications.

The grounding lands 12 a and 12 b and the ground-connection lands 13 a and 13 b may be arranged so that the capacitors are connected either in parallel or in series. The type of connection of the capacitors can be selected according to factors such as withstand voltage and noise level.

In the example shown in FIG. 2 , the grounding lands 12 a and 12 b and the ground-connection lands 13 a and 13 b are arranged for parallel connection of the capacitors.

FIG. 3 shows an example of an arrangement of lands for series connection of the capacitors. The capacitors may be connected in series using additional lands connected to, for example, the ground patterns of the low-voltage and high-voltage circuits.

The grounding lands 12 a and 12 b and the ground-connection lands 13 a and 13 b may be provided at a plurality of positions, depending on the characteristics of the control board 10 . The capacitance and number of capacitors connected to the grounding lands 12 a and 12 b and the ground-connection lands 13 a and 13 b are preferably selected according to the characteristics of the control board 10 and numerical noise suppression characteristics. Specifically, capacitors having frequency characteristics corresponding to the frequency band of noise to be reduced are preferably connected.

FIGS. 4 to 6 show examples of frequency characteristics of capacitors for connection to the grounding lands 12 a and 12 b and the ground-connection lands 13 a and 13 b shown in FIG. 2 . In this embodiment, capacitors having the frequency characteristics shown in FIG. 4 are connected to the grounding lands 12 a and 12 b and the ground-connection lands 13 a and 13 b.

Alternatively, capacitors having the frequency characteristics shown in FIG. 5 or 6 may be used instead of the capacitors having the frequency characteristics shown in FIG. 4 .

For example, capacitors having characteristics suitable for noise reduction in the frequency band of about 0.15 MHz to 2,500 MHz may be selected for car air conditioners, which often require noise reduction in this frequency band.

In the car air conditioner 1 according to this embodiment, as described above, the ground pattern of the low-voltage circuit of the control board 10 used in the control apparatus 2 can be grounded, so that the low-voltage circuit can operate at a stable frequency.

In addition, the ground patterns of the high-voltage and low-voltage circuits can be connected via the capacitors connected to the ground-connection lands 13 a and/or the ground-connection lands 13 b to reduce noise on the high-voltage circuit side. Also, the low-voltage circuit and the high-voltage circuit can be electrically separated because the ground patterns thereof are connected via the capacitors.

Furthermore, the ground pattern of the high-voltage circuit can be grounded via the capacitors connected to the grounding lands 12 a and/or the grounding lands 12 b , so that the high-voltage circuit can operate at a stable frequency.