JP2016143697A - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve resistance to electromagnetic radiation noise while preventing influence on fluctuation of ground potential which results from fluctuation of a ground current at a circuit board on which multiple circuit blocks are formed.SOLUTION: A circuit board (100) includes: a first ground pattern (112) which is formed along an outer periphery of the circuit board (100) so as to enclose an inner region; and a second ground pattern (114) which is formed so as to enclose a part of the region enclosed by the first ground pattern. Part of the first ground pattern and part of the second ground pattern are connected to each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a circuit board, and more particularly to a circuit board that is not easily affected by external radiation noise.

  A control device that controls the amount of operation of an actuator or the like based on a signal from a sensor receives a weak analog signal output from the sensor and amplifies the signal, and the amplified analog signal is converted into a digital signal. A digital processing circuit that converts and calculates the value of the operating amount, converts the calculated value back into an analog signal (analog signal that indicates the operating amount), and outputs the actuator, based on the output analog signal that indicates the operating amount It is composed of a plurality of circuit blocks constituting various circuits according to the purpose, such as a drive circuit that outputs a large current signal or a large voltage signal (hereinafter collectively referred to as “driving signal”) Many.

  In order for the control circuit configured by these circuit blocks to operate correctly as a whole, each circuit block is subject to interference caused by external radiation noise coming from outside the circuit board and radiation noise from adjacent circuit blocks. It is necessary to operate normally. In particular, in a vehicle that obtains driving power by an internal combustion engine or a motor, due to fluctuations in a large current or large voltage that occur when controlling a spark plug for fuel combustion, an actuator that drives a fuel valve, a large output motor, or the like, Extremely large radiation noise is generated, and it is extremely important to prevent the influence of radiation noise on electronic control equipment.

  Conventionally, as means for reducing the influence of radiation noise, a circuit board in which a plurality of circuit blocks are arranged on a circuit board and a ground pattern surrounding each circuit block is provided in each circuit block is known (Patent Document). 1).

  However, in the above conventional configuration, although resistance to radiation noise is increased, since the ground pattern is connected to one, when the ground of each circuit block flows through the ground pattern, a large ground current flows out from the one circuit block. In such a case, even though the ground pattern is formed of a conductor, a slight electric resistance exists, so that a voltage drop occurs in the ground pattern portion through which the large ground current flows, and the ground potential of the ground pattern is It becomes non-uniform and may have a potential distribution depending on the location.

  As a result, if the large ground current fluctuates, the difference between the ground potential in the one circuit block and the ground potential in the other circuit block will fluctuate, and the operation of the entire electronic circuit composed of these circuit blocks May cause errors. Such a situation has, in particular, a small signal amplification circuit block that receives and amplifies a small signal from a sensor, and a control circuit block that controls a device driven by a large current (or voltage) such as an actuator. It is likely to occur in the control device.

  Conventionally, in a circuit board having a plurality of circuit blocks having different ground current magnitudes, the ground of a circuit block having a small ground current is connected upstream of the ground current path, and the ground of a circuit block having a large ground current is connected to the ground current path. By connecting downstream, even if a large ground current causes a voltage drop in the ground path from the circuit board to the power supply, the ground potential of each circuit block fluctuates in the same phase, so that the ground potential between circuit blocks It is known to eliminate or keep the difference between them (Patent Document 2)

  However, in the configuration of Patent Document 2, there is room for improvement because the effects of external radiation noise coming from outside the circuit board and resistance to interference via radiation noise between circuit blocks are not considered.

JP 2004-247355 A Japanese Patent No. 2012-114218

  From the above background, in a circuit board composed of a plurality of circuit blocks, each circuit block is normally operated even in the presence of radiation noise while preventing the occurrence of a ground potential difference between the circuit blocks or the fluctuation of the difference. In order to operate, it is desired to improve resistance to external radiation noise coming from the outside of the circuit board and resistance to interference via radiation noise between circuit blocks.

One aspect of the present invention is configured to surround a first ground pattern formed so as to surround an inner region along the outer periphery, and a part of the region surrounded by the first ground pattern. And a second ground pattern, wherein a part of the first ground pattern and a part of the second ground pattern are connected to each other.
According to another aspect of the present invention, the first ground pattern is connected to the ground of a power source.
According to another aspect of the present invention, the total amount of ground current flowing from the circuit component on the circuit board to the first ground pattern is the ground amount flowing from the circuit component on the circuit board to the second ground pattern. Greater than current.
According to another aspect of the present invention, a first circuit block that processes a signal from a signal source and / or a second circuit block that performs a logical operation is disposed in a region surrounded by the second ground pattern. In a region surrounded by the first ground pattern other than a region surrounded by the second ground pattern, a third circuit block for driving a load is disposed.
Another aspect of the present invention is an electronic device including the circuit board.
According to another aspect of the electronic device, which is another aspect of the present invention, a housing made of a conductive material is provided, and the first ground pattern is electrically connected to the housing.

It is a block diagram which shows the structure of the electronic device using the circuit board which concerns on one Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an electronic device using a circuit board according to an embodiment of the present invention.

  The electronic device 10 is an electronic control unit (ECU, Electronic Control Unit) that is mounted on a vehicle and controls the engine of the vehicle, and includes a circuit board 100 that is a printed circuit board on which electronic components that constitute a control circuit are mounted. And a connector 102 disposed on the circuit board 100 and a housing 104 that accommodates the circuit board 100 and the connector 102. In addition, since the circuit board 100 is accommodated in the housing 104, the circuit board 100 cannot be visually recognized from the outside of the housing 104. However, in FIG. Is also shown using a solid line.

  The housing 104 is provided with a flange 106 on the outer surface thereof. The housing 104 and the flange 106 are both made of a conductive material such as metal (for example, aluminum), and the housing 104 is mechanically fixed to an external structure 108 such as a vehicle body by the flange 106 provided on the housing 104. In addition, the flange 106 is electrically connected to the external structure 108. A ground (GND) terminal of a power source 110 is connected to the external structure 108, and a + V terminal of the power source 110 is connected to an electronic circuit on the circuit board 100 via the connector 102, and Power is supplied to each circuit component.

  On the circuit board 100, a power ground (PG) 112 formed in a pattern (closed band shape of a rectangular frame shape in this embodiment) closed along the outer periphery so as to surround the inner space from the outer periphery. And a logic ground (LG) formed in a pattern on the circuit board 100 surrounded by the PG 112 so as to surround a part of the area (in this embodiment, a rectangular frame-shaped closed band). ) 114 and a signal ground (SG) 116 formed in a part of a region surrounded by LG 114.

  SG 116 is a ground pattern for a small signal circuit mainly having a function of processing a signal input from a sensor or the like, and the total amount of ground current flowing from the circuit components is minimized as compared with LG 114 and PG 112. An electronic circuit on the circuit board 100 is designed. PG112 is a ground pattern for a drive circuit for mainly driving a load such as an actuator. The electronic circuit is designed so that the total amount of ground current flowing from the circuit components is the largest compared to SG116 and LG114. Has been. LG114 is a ground pattern mainly for a logic circuit or the like that performs a logical operation, and the total amount of ground current flowing from the circuit component to LG114 is larger than the total amount of ground current flowing from the circuit component to SG116. The electronic circuit is designed so as to be smaller than the total amount of ground current flowing into the PG 112 from the circuit component.

  The PG 112 is electrically connected to the housing 104 via a conductor 118 made of a conductive material such as metal (for example, a copper plate), and is connected to the GND terminal of the power source 110 via the flange 106 and the external structure 108. It is connected. The LG 114 is connected to the PG 112 on the circuit board 100, and the SG 116 is connected to the LG 114. As a result, the SG 116 having the smallest total amount of ground current flowing from the circuit component is connected to the most upstream portion of the ground current path on the circuit board 100, and the ground current flowing from the circuit component to the most downstream portion of the ground current path. The PG 112 having the largest total amount is connected, and the LG 114 whose ground current amount flowing from the circuit component is an intermediate amount between the SG 116 and the PG 112 is connected to an intermediate portion between the SG 116 and the PG 112 along the ground current path. It becomes.

  The small signal circuit block 120 and the logic operation circuit block 122 are arranged in the area surrounded by the LG 114, and the drive circuit block 124 is arranged in the area surrounded by the PG 112 outside the LG 114. .

  The small signal circuit block 120 includes an amplifier 128 that amplifies an analog signal received from a signal source 126 (a sensor or other device that supplies a signal) via the connector 102, and an amplified analog signal that is output from the amplifier 128. And an ADC (Analog-to-Digital Converter) 130 for converting the signal into a digital signal.

  An analog signal received from the signal source 126 via the connector 102 is connected to the amplifier 128 via a noise removal circuit 132 constituted by a low-pass filter or the like disposed in the immediate vicinity of the connector 102. The noise removal circuit 132 and the amplifier are connected by a wiring pattern 138 provided on the back surface of the circuit board 100 through via holes 134 and 136.

  The signal source 126 is connected to the SG 116 via the connector 102, the via holes 140 and 142, and the wiring pattern 144 provided on the back surface of the circuit board 100. The ground of the amplifier 128 and the analog ground of the ADC 130 are also It is connected to the same SG116. As a result, the analog signal output from the signal source 126 is appropriately amplified by the amplifier 128 and converted into a digital signal by the ADC 130 with the ground potential of the SG 116 as a reference, and the digital signal with a small error indicating the magnitude of the analog signal. A signal is obtained from the ADC 130.

  The logical operation circuit block 122 receives a digital signal output from the ADC 130 and performs a predetermined arithmetic processing (CPU) 146, and a memory 148 that stores data, programs, and the like necessary for the arithmetic processing of the CPU 146. And composed of

  The drive circuit block 124 is connected via the connector 102 based on a DAC (Digital-to-Analog Converter) 150 that converts a digital signal output from the CPU 146 into an analog signal and an analog signal output from the DAC 150. It comprises a driver 154 that drives a load 152 such as an actuator. The CPU 146 and the DAC 150 are connected via via holes 156 and 158 and a wiring pattern 160 provided on the back surface of the circuit board 100.

  The logic ground of the ADC 130 constituting the small signal circuit block 120, the ground of the CPU 146 and the memory 148 constituting the logic operation circuit block 122, and the logic ground of the DAC 150 constituting the drive circuit block 124 are connected to the LG 114. . As a result, the ADC 130, the CPU 146, the memory 148, and the DAC 150 can correctly exchange digital signals with reference to the ground potential of the LG 114.

  Further, the analog ground of the DAC 150 and the ground of the driver 154 are connected to the PG 112. The load 152 is also connected to the PG 112 via the connector 102. Thus, the analog signal output from the DAC 150 is amplified by the driver 154 and used to drive the load 152 with reference to the ground potential of the PG 112, so that a driving operation with less error is realized.

  In the electronic device 10 having the above configuration, since the PG 112 having the largest total amount of ground current flowing from the circuit component is connected to the most downstream portion of the ground current path on the circuit board 100, the PG 112 flows from the circuit component to the PG 112. Even when the total ground current fluctuates and the voltage drop of the external structure 108 constituting the ground current path fluctuates outside the electronic device 10 and the ground potential of the PG 112 fluctuates, the ground potentials of the SG 116 and LG 114 change in phase with the PG 112. Therefore, the difference in the ground potential between the circuit blocks 120, 122, and 124 does not vary, and the operation of the electronic device 10 as a whole is kept stable.

  In addition, since the PG 112 is formed on the outer periphery of the circuit board 100 so as to surround the inner region of the circuit board 100, electromagnetic radiation noise coming from the outside with respect to the electronic circuit configured on the circuit board 100 is reduced. The impact is effectively reduced. In addition, since a part of the region surrounded by PG 112 is surrounded by LG 114 and the small signal circuit block 120 that is most susceptible to noise is arranged in the region surrounded by LG 114, the small signal circuit block 120 is arranged. In addition, the influence of the external electromagnetic radiation noise on the small signal circuit block 120 can be effectively reduced by the electromagnetic radiation noise generated from the drive circuit block 124 that outputs a large current.

  Similarly, since the PG 112 is formed on the outer periphery of the circuit board 100 so as to surround a region inside the circuit board 100, the electrons on the circuit board 100 are coupled with the conductive casing 104. The electromagnetic radiation noise generated from the circuit can be effectively prevented from being released to the outside of the housing 104.

  In addition, since a drive circuit block 124 that outputs a large current and generates a lot of heat is disposed in a region surrounded by the PG 112 provided on the outer periphery of the circuit board 100 outside the LG 114, the drive circuit block 124 The generated heat is absorbed by PG 112 and released to the outside through the conductor 118 and the housing 104. As a result, the heat dissipation efficiency of the electronic device 10 can be improved, and the heat generation of the drive circuit block 124 can be effectively prevented from affecting the operations of the small signal circuit block 120 and the logic operation circuit block 122.

  In the present embodiment, the PG 112 is configured to be electrically connected to the housing 104 via the conductor 118. However, the present invention is not limited to this, and the PG 112 portion (for example, two portions along the upper and lower sides in the drawing) is used. The electrical connection between the PG 112 and the housing 104 may be ensured by sandwiching the two structures (for example, the base and the cover) constituting the housing 104 from the thickness direction of the circuit board 100. In this case, since the contact area between the PG 112 and the housing 104 can be increased, the heat from the drive circuit block 124 and the like absorbed by the PG 112 can be efficiently transmitted to the housing 104, and the heat dissipation effect can be achieved. Can be increased.

  Further, by connecting some of the connection pins of the connector 102 to the PG 112, the heat of the PG 112 can be transmitted to the outside via a cable connected to the connector 102, and the heat dissipation effect can be enhanced.

  In the present embodiment, the SG 116 is illustrated as having a rectangular shape. However, the present invention is not limited thereto, and the SG 116 is formed so as to surround a part of the region on the circuit board 100 surrounded by the LG 114. The small signal circuit block 120 may be arranged in a region surrounded by SG116. In this case, it is possible to further reduce the influence of the external electromagnetic radiation noise or the electromagnetic radiation noise generated in the drive circuit block 124 on the small signal circuit block 120.

  DESCRIPTION OF SYMBOLS 10 ... Electronic device, 100 ... Circuit board, 102 ... Connector, 104 ... Housing, 106 ... Flange, 108 ... External structure, 110 ... Power supply, 112 ... PG, 114 ... LG, 116 ... SG, 118 ... conductor, 120 ... small signal circuit block, 122 ... logic operation circuit block, 124 ... drive circuit block, 126 ... Signal source, 128... Amplifier, 130... ADC, 132... Noise removal circuit, 134, 136, 140, 142, 156, 158... Via hole, 138, 144, 160. 146 ... CPU, 148 ... memory, 150 ... DAC, 152 ... load, 154 ... driver.

Claims (6)

A circuit board,
A first ground pattern formed so as to surround the inner region along the outer periphery;
A second ground pattern configured to surround a part of the region surrounded by the first ground pattern;
Have
A part of the first ground pattern and a part of the second ground pattern are connected to each other;
Circuit board.   The circuit board according to claim 1, wherein the first ground pattern is connected to a ground of a power source.   The total amount of ground current flowing from the circuit component on the circuit board into the first ground pattern is larger than the ground current flowing from the circuit component on the circuit board into the second ground pattern. 2. The circuit board according to 2. In a region surrounded by the second ground pattern, a first circuit block for processing a signal from a signal source and / or a second circuit block for performing a logical operation are arranged,
In a region surrounded by the first ground pattern other than a region surrounded by the second ground pattern, a third circuit block for driving a load is disposed.
The circuit board according to any one of claims 1 to 3.   An electronic device comprising the circuit board according to claim 1. It has a housing made of a conductive material,
The first ground pattern is electrically connected to the housing;
The electronic device according to claim 5.

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