WO2021012191A1

WO2021012191A1 - Insulation detection circuit, mainboard, and related device

Info

Publication number: WO2021012191A1
Application number: PCT/CN2019/097344
Authority: WO
Inventors: 唐林; 胡定高; 赵德琦; 吴壬华
Original assignee: 深圳欣锐科技股份有限公司
Priority date: 2019-07-23
Filing date: 2019-07-23
Publication date: 2021-01-28
Also published as: CN111566490A; CN111566490B

Abstract

Disclosed in the present application is an insulation detection circuit, comprising an alternating current power supply, a filter circuit, and a detection circuit. The detection circuit comprises a first sub-detection circuit and a second sub-detection circuit; the alternating current power supply is connected to the filter circuit; the filter circuit is connected to the first sub-detection circuit and the second sub-detection circuit; an alternating current signal generated by the alternating current power supply passes through the filter circuit to generate a first current signal; the first current signal flows to the first sub-detection circuit and the second sub-detection circuit, a first voltage is generated at the first sub-detection circuit, and a second voltage is generated at the second sub-detection circuit. Embodiments of the present application can simplify design of an insulation detection circuit.

Description

Insulation detection circuit, motherboard and related devices

Technical field

This application relates to the technical field of circuit structures, and in particular to an insulation detection circuit, a motherboard and related devices.

Background technique

In life, electricity is an essential element. In some occasions where there is no power supply or the power supply cannot be interrupted, it is inevitable to use some equipment to convert other energy sources into alternating current to supply power to the electrical equipment, such as Uninterruptible Power System/Uninterruptible Power Supply, UPS, Car inverter. In order to avoid electric shock accidents caused by insulation failure when using these devices, it is necessary to test the insulation performance of the AC power supply and the chassis, and cut off the power supply in time when the insulation failure is found. At present, the common method of insulation detection circuit is the unbalanced bridge method. The unbalanced bridge method needs to control four switches and measure four voltages to calculate the insulation resistance. This measurement method is complicated.

Summary of the invention

The embodiments of the present application provide an insulation detection circuit, a motherboard, and related devices to simplify the design of the insulation detection circuit.

In a first aspect, an embodiment of the present application provides an insulation detection circuit, including an AC power supply, a filter circuit, and a detection circuit. The detection circuit includes a first sub-detection circuit and a second sub-detection circuit, wherein:

The AC power supply is connected to the filter circuit, and the filter circuit is connected to the first sub-detection circuit and the second sub-detection circuit;

The AC power supply generates an AC signal, the AC signal passes through the wave detection circuit to generate a first current signal, and the first current signal generates a first voltage in the first sub-detection circuit. The current signal generates a second voltage in the second sub-detection circuit.

In an embodiment of the present application, the filter circuit includes a first capacitor, a first resistor, a second capacitor, and a second resistor, wherein:

The second port of the first capacitor is connected to the first port of the first resistor, the second port of the first resistor is connected to the first port of the second resistor, and the second port of the second resistor is connected The port is connected to the first port of the second capacitor.

In an embodiment of the present application, the first port of the filter circuit is connected to the first port of the first capacitor; the second port of the filter circuit is connected to the second port of the first capacitor and the The first port of the first resistor is connected; the third port of the filter circuit is connected to the second port of the first resistor and the first port of the second resistor; the fourth port of the filter circuit is connected to the The second port of the second resistor is connected to the first port of the second capacitor; the fifth port of the filter circuit is connected to the second port of the second capacitor.

In an embodiment of the present application, the first sub-detection circuit includes a first rectifier diode and a third capacitor, and the second sub-detection circuit includes a second rectifier diode and a fourth capacitor, wherein:

The first port of the first sub-detection circuit is connected to the anode of the first rectifier diode, the cathode of the first rectifier diode is connected to the first port of the third capacitor, and the first port of the third capacitor is The two ports are connected to the second port of the first sub-detection circuit;

The first port of the second sub-detection circuit is connected to the first port of the fourth capacitor, the second port of the fourth capacitor is connected to the cathode of the second rectifier diode, and the second rectifier diode The positive pole of is connected to the second port of the second sub-detection circuit;

The second port of the first sub-detection circuit is connected to the first port of the second sub-detection circuit.

In an embodiment of the present application, the first port of the filter circuit is connected to the first port of the AC power supply; the second port of the filter circuit is connected to the first port of the first sub-detection circuit The third port of the filter circuit is connected to the second port of the first sub-detection circuit and the first port of the second sub-detection circuit; the fourth port of the filter circuit is connected to the second The second port of the sub-detection circuit is connected; the fifth port of the filter circuit is connected to the second port of the AC power supply.

In an embodiment of the present application, the capacitance value of the first capacitor is equal to the capacitance value of the second capacitor, the resistance value of the first resistor is equal to the resistance value of the second resistor, and the The capacitance value of the three capacitors is equal to the capacitance value of the fourth capacitor, and the model of the first rectifier diode is the same as the model of the second rectifier diode.

In an embodiment of the present application, the casing is connected to the second port of the first resistor and the first port of the second resistor.

In an embodiment of the present application, the insulation detection circuit is connected to a control circuit, the control circuit includes a micro control unit, and the micro control unit is used to detect the voltage of the third capacitor and the fourth capacitor;

Wherein, if the voltage difference between the third capacitor and the fourth capacitor is less than or equal to the preset threshold, the micro-control unit indicates that the insulation is normal; if the voltage difference between the third capacitor and the fourth capacitor is When the value is greater than the preset threshold, the micro control unit displays insulation failure.

In the second aspect, an embodiment of the present application provides a motherboard, which includes a printed circuit board and the insulation detection circuit described in any one of the above.

In a third aspect, the present application provides an insulation detection device, which includes a housing and the above-mentioned motherboard.

In the embodiment of the present application, the AC power supply is connected to the filter circuit, and the filter circuit is connected to the detection circuit. The detection circuit includes a first sub-recognition circuit and a second sub-recognition circuit; the AC power source generates an alternating current signal. The electric signal passes through the wave detection circuit to generate a first current signal, the first current signal generates a first voltage in the first sub-detection circuit, and the first current signal generates a second voltage in the second sub-detection circuit. It can be seen that this application only needs to measure two voltages, and by comparing the difference between the two voltages, the insulation performance of the AC power supply and the casing can be judged. Compared with the existing unbalanced bridge method, the insulation detection circuit is simplified.

These and other aspects of the application will be more concise and understandable in the description of the following embodiments.

Description of the drawings

In order to more clearly describe the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative work, other drawings can be obtained based on these drawings.

FIG. 1 is a circuit block diagram of an insulation detection circuit provided by an embodiment of the present application;

2A is a schematic structural diagram of an insulation detection circuit provided by an embodiment of the present application;

2B is a schematic diagram of the structure of the insulation detection circuit when the insulation performance is normal;

2C is a schematic diagram of the structure of the insulation detection circuit when the insulation performance fails;

3 is a schematic structural diagram of a filter circuit in the insulation detection circuit shown in FIG. 2A;

4 is a schematic diagram of the structure of the wave detection circuit in the insulation detection circuit shown in FIG. 2A.

Detailed ways

In order to enable those skilled in the art to better understand the solution of the application, the technical solutions in the embodiments of the application will be clearly and completely described below in conjunction with the drawings in the embodiments of the application. Obviously, the described embodiments are only It is a part of the embodiments of this application, not all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work should fall within the protection scope of this application.

Detailed descriptions are given below.

The terms "first", "second", "third" and "fourth" in the description and claims of the application and the drawings are used to distinguish different objects, rather than describing a specific order . In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes unlisted steps or units, or optionally also includes Other steps or units inherent to these processes, methods, products or equipment.

Reference to "embodiments" herein means that a specific feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art clearly and implicitly understand that the embodiments described herein can be combined with other embodiments.

The embodiments of the present application will be described below in conjunction with the drawings.

Please refer to FIG. 1. FIG. 1 is a circuit block diagram of an insulation detection circuit provided by an embodiment of the present application. The insulation detection circuit includes an AC power supply, a filter circuit, and a detection circuit. The detection circuit includes a first sub-detection circuit and a second sub-detection circuit, wherein:

The AC signal generated by the AC power source passes through the filter circuit to generate the first current signal. The first current signal flows to the first sub-recognition circuit and the second sub-recognition circuit, and the first voltage is generated in the first sub-recognition circuit. The two sub-detection circuit generates the second voltage.

It can be seen that in the embodiment of the present application, the AC power supply is connected to the filter circuit, and the filter circuit is connected to the detection circuit. The detection circuit includes a first sub-detection circuit and a second sub-detection circuit connected; An alternating current signal, the alternating current signal passes through the wave detection circuit to generate a first current signal, the first current signal generates a first voltage in the first sub-detection circuit, and the first current signal generates a second voltage in the second sub-detection circuit. It can be seen that this application only needs to measure two voltages, and by comparing the difference between the two voltages, the insulation performance of the AC power supply and the casing can be judged. Compared with the existing unbalanced bridge method, the insulation detection circuit is simplified.

Please refer to FIG. 2A, which is a schematic structural diagram of another insulation detection circuit provided by an embodiment of the present application. The insulation detection circuit includes an AC power supply 100, a filter circuit 200, and a detection circuit 300. The detection circuit 300 includes a first sub The detection circuit 310 and the second sub-detection circuit 320, in which:

The filter circuit 200 includes a first capacitor C1, a first resistor R1, a second capacitor C2, and a second resistor R2. The second port of the first capacitor C1 is connected to the first port of the first resistor R1. The two ports are connected to the first port of the second resistor R2, and the second port of the second resistor R2 is connected to the first port of the second capacitor C2.

The first port 201 of the filter circuit 200 is connected to the first port of the first capacitor C1; the second port 202 of the filter circuit 200 is connected to the second port of the first capacitor C1 and the first port of the first resistor R1; the filter circuit 200 The third port 203 of the first resistor R1 is connected to the second port of the second resistor R2; the fourth port 204 of the filter circuit 200 is connected to the second port of the second resistor R2 and the first port of the second capacitor C2. Port connection; the fifth port 205 of the filter circuit 200 is connected to the second port of the second capacitor C2.

The first sub-detection circuit 310 includes a first rectifier diode D1 and a third capacitor C3. The first port 311 of the first sub-detection circuit 310 is connected to the anode of the first rectifier diode D1, and the cathode of the first rectifier diode D1 is connected to The first port of the third capacitor C3 is connected, and the second port of the third capacitor C3 is connected to the second port 312 of the first sub-detection circuit;

The second sub-detection circuit 320 includes a second rectifier diode D2 and a fourth capacitor C4. The first port 321 of the second sub-detection circuit 320 is connected to the first port of the fourth capacitor C4, and the second port of the fourth capacitor C4 is The port is connected to the cathode of the second rectifier diode D2, and the anode of the second rectifier diode D2 is connected to the second port 322 of the second sub-detection circuit 320;

The second port 312 of the first sub-detection circuit 310 is connected to the first port 321 of the second sub-detection circuit 320.

The first port 201 of the filter circuit 200 is connected to the first port of the AC power supply 100; the second port 202 of the filter circuit 200 is connected to the first port 311 of the first sub-detection circuit 310; the third port 203 of the filter circuit 200 is connected to The second port 312 of the first sub-detection circuit 310 and the first port 321 of the second sub-detection circuit 320 are connected; the fourth port 204 of the filter circuit 200 is connected with the second port 322 of the second sub-detection circuit 320; The fifth port 205 of the filter circuit 200 is connected to the second port of the AC power supply 100.

Among them, the capacitance value of the first capacitor C1 is equal to the capacitance value of the second capacitor C2, the resistance value of the first resistor R1 is equal to the resistance value of the second resistor R2, and the capacitance value of the third capacitor C3 is equal to the capacitance value of the fourth capacitor C4. The values are equal, and the model of the first rectifier diode D1 and the model of the second rectifier diode D2 are the same.

Wherein, the casing is connected to the second port of the first resistor R1 and the first port of the second resistor R2.

Wherein, the insulation detection circuit is connected to the control circuit, and the control circuit includes a micro control unit, which is used to detect the voltage of the third capacitor C3 and the fourth capacitor C4.

Wherein, if the voltage difference between the third capacitor C3 and the fourth capacitor C4 is less than or equal to the preset threshold, the micro-control unit displays that the insulation is normal; if the voltage difference between the third capacitor C3 and the fourth capacitor C4 is greater than the preset threshold , The micro control unit shows insulation failure.

It can be seen that, in the embodiment of the present application, the AC power supply is connected to the filter circuit, and the filter circuit is connected to the detection circuit. The detection circuit includes a first sub-detection circuit and a second sub-detection circuit connected; the AC power source generates AC The electric signal, the alternating current signal passes through the wave detection circuit to generate a first current signal, the first current signal generates a first voltage in the first sub-detection circuit, and the first current signal generates a second voltage in the second sub-detection circuit. It can be seen that this application only needs to measure two voltages, and by comparing the difference between the two voltages, the insulation performance of the AC power supply and the casing can be judged. Compared with the existing unbalanced bridge method, the insulation detection circuit is simplified.

The working process of the insulation detection circuit shown in FIG. 2A is described in detail below.

First, it should be noted that the filter circuit 200 is connected to the output terminal of the AC power supply 100 in a symmetrical structure, and the internal component parameters correspond one-to-one. At the same time, since the first sub-recognition circuit 310 and the second sub-recognition circuit 320 have the same structure, the internal component parameters of the two are also the same. For example, the capacitance values of the first capacitor C1 and the second capacitor C2 in the filter circuit 200 are the same, and the resistance values of the first resistor R1 and the second resistor R2 are the same; the third capacitor C3 in the first sub-detection circuit 310 and The capacitance value of the third capacitor C4 in the second sub-detection circuit 320 is the same. The model of the first rectifier diode D1 in the first sub-detection circuit 310 is the same as that of the second rectifier diode D2 in the second sub-detection circuit 320. The models are the same.

Please refer to FIG. 2B. FIG. 2B is a structural diagram of the insulation detection circuit when the insulation performance is normal. Compared with FIG. 2A, FIG. 2B is connected to the casing at the second port of the first resistor R1 and the first port of the second resistor R2 in FIG. 2A. The AC power source generates an AC signal. The AC signal passes through the first capacitor C1, the first resistor R1, the second resistor R2, and the second capacitor C2 to generate a first current signal in the detection circuit. The first current signal is used in the first sub-test. The third capacitor C3 is charged through the first rectifier diode D1 in the wave circuit, and the first current signal is charged through the second rectifier diode D2 in the second sub-wave circuit to charge the fourth capacitor C4. The insulation performance described in Figure 2B is normal. When the insulation detection circuit is completely symmetrical, it can be detected that the first voltage U1 at both ends of the third capacitor C3 and the second voltage U2 at both ends of the fourth capacitor C4 are equal.

Please refer to FIG. 2C, which is a schematic diagram of the structure of the insulation detection circuit when the insulation performance fails. When the insulation performance of the AC power supply 100 fails, the output cable of the AC power supply and the casing do not show an open circuit state. Compared with FIG. 2B, FIG. 2C is equivalent to connecting a third resistor Rx between the first port of the first capacitor C1 and the casing of FIG. 2B. The AC power source generates an AC signal, the AC signal passes through the third resistor Rx to generate a second current signal, the AC signal passes through the first capacitor C1 and the first resistor R1 to generate a third current signal, and the AC signal passes through the second resistor R2 and the The second capacitor C2 generates a fourth current signal. The magnitude of the fourth current signal is equal to the sum of the second current signal and the third current signal. The third current signal passes through the first rectifier diode D1 to the third capacitor in the first sub-detection circuit. C3 is charged. The fourth current signal passes through the second rectifier diode D2 to charge the fourth capacitor C4 in the second sub-detection circuit. Because the third current signal is smaller than the fourth current signal and the model of the first rectifier diode D1 is the same as the second rectifier The diode D2 has the same model and the third capacitor C3 and the fourth capacitor C4 have the same capacitance value. It can be detected that the first voltage U1 across the third capacitor C3 and the second voltage U2 across the fourth capacitor C4 are not equal.

Please refer to FIG. 3. FIG. 3 is a schematic structural diagram of a filter circuit in the insulation detection circuit shown in FIG. 2A. The filter circuit 200 includes a first capacitor C1, a first resistor R1, a second capacitor C2, and a second resistor R2. :

The second port of the first capacitor C1 is connected to the first port of the first resistor R1, the second port of the first resistor R1 is connected to the first port of the second resistor R2, and the second port of the second resistor R2 is connected to the second capacitor The first port of C2 is connected.

Among them, C1 and C2 are safety capacitors.

Wherein, the capacitance value of the first capacitor C1 is equal to the capacitance value of the second capacitor C2, and the resistance value of the first resistor R1 is equal to the resistance value of the second resistor R2.

The first port 201 of the filter circuit 200 is connected to the first port of the first capacitor C1, the second port 202 of the filter circuit 200 is connected to the second port of the first capacitor C1 and the first port of the first resistor R1, the filter circuit 200 The third port 203 of the first resistor R1 is connected to the second port of the second resistor R2, and the fourth port 204 of the filter circuit 200 is connected to the second port of the second resistor R2 and the first port of the second capacitor C2. Port connection, the fifth port 205 of the filter circuit 200 is connected to the second port of the second capacitor C2.

Please refer to FIG. 4. FIG. 4 is a schematic structural diagram of a detection circuit in the insulation detection circuit shown in FIG. 2A. The detection circuit 300 includes a first sub-detection circuit 310 and a second sub-detection circuit 320, wherein:

The first sub-detection circuit 310 includes a first rectifier diode D1 and a third capacitor C3. The first port 311 of the first sub-detection circuit 301 is connected to the anode of the first rectifier diode D1, and the cathode of the first rectifier diode D1 is connected to the The first port of the three capacitor C3 is connected, and the second port of the third capacitor C3 is connected to the second port 312 of the first sub-detection circuit;

The second sub-detection circuit 320 includes a second rectifier diode D2 and a fourth capacitor C4. The first port 321 of the second sub-detection circuit 320 is connected to the first port of the fourth capacitor C4, and the second port of the fourth capacitor C4 Connected to the cathode of the second rectifier diode D2, and the anode of the second rectifier diode D2 is connected to the second port 322 of the second sub-detection circuit 320;

Wherein, the capacitance value of the third capacitor C3 is equal to the capacitance value of the fourth capacitor C4, and the model of the first rectifier diode D1 is the same as the model of the second rectifier diode D2.

In a possible example, an embodiment of the present application provides a motherboard, which includes a printed circuit board and the insulation detection circuit described in any one of the above.

In a possible example, an embodiment of the present application provides an insulation detection device, including a housing and the above-mentioned motherboard.

Wherein, the insulation detection circuit in the insulation detection device is the same as the insulation detection circuit described in any of the above application embodiments, and will not be described here.

It should be noted that for the foregoing application embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should know that this application is not limited by the described sequence of actions. Because according to this application, some steps can be performed in other order or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by this application.

In the above-mentioned embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in an embodiment, reference may be made to related descriptions of other embodiments.

In the several embodiments provided in this application, it should be understood that the disclosed device may be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the above-mentioned units is only a logical function division, and there may be other divisions in actual implementation, for example, multiple units or components can be combined or integrated To another system, or some features can be ignored, or not implemented. In addition, the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or units, and may be in electrical or other forms.

The units described above as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

In addition, the functional units in each embodiment of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units may be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or software functional unit.

The embodiments of the application are described in detail above, and specific examples are used in this article to illustrate the principles and implementation of the application. The descriptions of the above embodiments are only used to help understand the application and its core ideas; at the same time, for the field According to the ideas of the application, the general technical personnel of, will have changes in the specific implementation and the scope of application. In summary, the content of this specification should not be construed as a limitation of the application.

Claims

An insulation detection circuit, characterized by comprising: an AC power supply, a filter circuit, and a detection circuit. The detection circuit includes a first sub-detection circuit and a second sub-detection circuit, wherein:

The AC power supply is connected to the filter circuit, and the filter circuit is connected to the first sub-detection circuit and the second sub-detection circuit;

The AC signal generated by the AC power source passes through the filter circuit to generate a first current signal, and the first current signal flows to the first sub-detection circuit and the second sub-detection circuit, and in the first A sub-detection circuit generates a first voltage, and the second sub-detection circuit generates a second voltage.
The insulation detection circuit according to claim 1, wherein the filter circuit comprises a first capacitor, a first resistor, a second capacitor, and a second resistor, wherein:

The second port of the first capacitor is connected to the first port of the first resistor, the second port of the first resistor is connected to the first port of the second resistor, and the second port of the second resistor is connected The port is connected to the first port of the second capacitor.
The insulation detection circuit according to claim 2, wherein the first port of the filter circuit is connected to the first port of the first capacitor; the second port of the filter circuit is connected to the first port of the first capacitor. The second port is connected to the first port of the first resistor; the third port of the filter circuit is connected to the second port of the first resistor and the first port of the second resistor; the filter circuit The fourth port is connected to the second port of the second resistor and the first port of the second capacitor; the fifth port of the filter circuit is connected to the second port of the second capacitor.
The insulation detection circuit of claim 3, wherein the first sub-detection circuit includes a first rectifier diode and a third capacitor, and the second sub-detection circuit includes a second rectifier diode and a fourth capacitor. ,among them:

The first port of the first sub-detection circuit is connected to the anode of the first rectifier diode, the cathode of the first rectifier diode is connected to the first port of the third capacitor, and the first port of the third capacitor is The two ports are connected to the second port of the first sub-detection circuit;

The first port of the second sub-detection circuit is connected to the first port of the fourth capacitor, the second port of the fourth capacitor is connected to the cathode of the second rectifier diode, and the second rectifier diode The positive pole of is connected to the second port of the second sub-detection circuit;

The second port of the first sub-detection circuit is connected to the first port of the second sub-detection circuit.
The insulation detection circuit according to claim 4, wherein the first port of the filter circuit is connected to the first port of the AC power supply; the second port of the filter circuit is connected to the first sub-detection wave The first port of the circuit is connected; the third port of the filter circuit is connected to the second port of the first sub-detection circuit and the first port of the second sub-detection circuit; the fourth port of the filter circuit The port is connected to the second port of the second sub-detection circuit; the fifth port of the filter circuit is connected to the second port of the AC power source.
The insulation detection circuit of claim 5, wherein the capacitance value of the first capacitor is equal to the capacitance value of the second capacitor, and the resistance value of the first resistor is equal to the resistance value of the second resistor. If the values are equal, the capacitance value of the third capacitor is equal to the capacitance value of the fourth capacitor, and the model of the first rectifier diode is the same as the model of the second rectifier diode.
7. The insulation detection circuit according to claim 6, wherein the housing is connected to the second port of the first resistor and the first port of the second resistor.
The insulation detection circuit according to claim 7, wherein the insulation detection circuit is connected to a control circuit, the control circuit includes a micro control unit, and the micro control unit is used to detect the third capacitance and the The voltage of the fourth capacitor;

Wherein, if the voltage difference between the third capacitor and the fourth capacitor is less than or equal to the preset threshold, the micro-control unit indicates that the insulation is normal; if the voltage difference between the third capacitor and the fourth capacitor is When the value is greater than the preset threshold, the micro control unit displays insulation failure.
A motherboard, characterized by comprising a printed circuit board and the insulation detection circuit according to any one of claims 1-8.
An insulation detection device, characterized in that it comprises a casing and the main board as claimed in claim 9.