JP3019783B2 - Printed circuit board temperature detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board temperature detecting device for detecting a rise in temperature of a printed circuit board and its surroundings.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional printed circuit board temperature detecting device. In FIG. 4, the printed circuit board 1 has an electric circuit 8 for processing electric signals mounted thereon. On the other hand, as a printed board temperature detecting device, a temperature sensor 9 is used.
Is disposed near the electric circuit 8 on the printed circuit board 1, and the temperature sensor 9 detects the heat generation of the electric circuit 8 and a rise in the surrounding temperature, and generates a temperature detection signal.

Next, the operation will be described. To detect whether the electric circuit 8 on the printed circuit board 1 has exceeded the ambient temperature condition for performing a normal operation,
It is necessary to detect the temperature on the printed circuit board in order to detect the burning of the printed circuit board 1 due to the heat generated by the abnormal operation. Therefore, a temperature sensor 9 for detecting the temperature is provided on the printed circuit board 1.

As the temperature sensor 9, for example, a temperature switch is used. That is, the temperature switch is set to turn on (or off) when the temperature on the periphery of the printed circuit board 1 reaches a predetermined temperature. An abnormal temperature can be detected by the operation of the temperature switch.

[0005]

However, in the above-mentioned conventional printed circuit board temperature detecting device, the temperature sensor is disposed on the printed circuit board to detect the temperature.
Only the temperature rise around the temperature sensor can be detected,
When the size of the printed circuit board becomes large, it is impossible to detect the temperature at a position far from the temperature sensor. If the temperature is to be detected at all places on the printed circuit board, it is necessary to attach many temperature sensors, and the circuit scale becomes large.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a printed circuit board temperature detecting device capable of detecting an abnormal temperature at an arbitrary position regardless of the size of the printed circuit board.

[0007]

In order to solve the above-mentioned problems, a printed board temperature detecting device according to the present invention is provided with at least a pair of external interface terminals 1A and 1B on a printed board 1 and at least a pair of external interface terminals 1A and 1B. A conductor pattern 2 is wired at a location where temperature detection is required, and both ends thereof are connected to the pair of external interface terminals 1A,
1B, a resistance value measuring means 3 for measuring a resistance value between a pair of external interface terminals 1A and 1B of the printed circuit board 1, and a resistance value obtained by the means 3 is previously determined. A temperature detection signal generating means for generating a temperature detection signal when the set value is exceeded.

In particular, the resistance value measuring means 3 includes a constant current source 5 for supplying a constant current to the conductor pattern 2 through the pair of external interface terminals 1A and 1B, and the constant current source 5 when the constant current flows. Is read as a resistance value.

The temperature detection signal generating means 4 compares the voltage value read by the resistance value measuring means 3 with a predetermined value corresponding to a preset detected temperature, and compares the input voltage value with the specified value. When a value exceeds a specified value, a temperature detection signal is generated and output.

Further, the conductor wiring means further comprises a plurality of external interface terminals 1A, 1B1 to 1Bn on the printed circuit board 1, and connects any part of the conductor pattern 2 wired on the printed circuit board 1 to the external interface. It is selectively connected to any of the terminals 1A, 1B1 to 1Bn. At this time, the resistance value measuring means 3 is connected to the plurality of external interface terminals 1A, 1B1 to 1Bn.
Is characterized by selectively measuring a resistance value between arbitrary terminals.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS.

FIG. 1 is a block diagram showing a configuration of a first embodiment of a printed circuit board temperature detecting device according to the present invention.
In FIG. 1, a printed circuit board 1 is provided with external interface terminals 1A and 1B. On one surface of the printed circuit board 1, a conductive pattern 2 is wired so as to pass through all corners. 1
A, 1B.

A resistance meter 3 for measuring a resistance value between both ends of the conductive pattern 2 is connected to the external interface terminals 1A and 1B of the printed circuit board 1. The measurement result of the resistance meter 3 is supplied to a temperature detection signal generation circuit 4. The temperature detection signal generation circuit 4 outputs a temperature detection signal when the input resistance value exceeds a predetermined value.

The operation of the above configuration will be described below.

The conductive pattern of the conductive pattern 2 wired on the printed circuit board 1 has a resistance, which has a temperature characteristic. Therefore, in the temperature detecting device according to the present invention, the external interface terminal 1
The resistance on the printed circuit board 1 is detected by connecting the resistance meter 3 between A and 1B and reading the change in the resistance value of the conductive pattern 2.

Here, assuming that the resistivity of the conductor forming the conductive pattern 2 is P, the conductor length is L, the conductor width is W, the conductor thickness is t, the temperature coefficient of the conductor is a, and the conductor temperature is T, the conductor is conductive. The resistance R of pattern 2 is It is represented by the following equation. From this equation, it can be seen that the value of the resistance R increases as the conductor temperature T increases.

Therefore, in the temperature detection signal generating circuit 4, a reference value of the resistance value R is previously obtained from the conductor temperature T to be detected based on the above equation (1), and the input resistance value R is determined. When the temperature exceeds the reference value, a temperature detection signal is generated and output.

Therefore, according to the above configuration, even if the size of the printed circuit board 1 becomes large, the entire temperature can be obtained without increasing the size of the apparatus.

FIG. 2 shows a specific configuration of the resistance meter 3 and the temperature detection signal generation circuit 4. That is, as the ohmmeter 3, a constant current source 5 for supplying a constant current I to the conductive pattern 2 is connected to an external interface terminal 1A to which one end of the conductive pattern 2 is connected on the printed board 1, and the other end of the conductive pattern 2 is connected to the other end. The terminal 1B to be connected is grounded.

On the other hand, the temperature detection signal generation circuit 4
The terminal 1A is connected to the positive input terminal (+) of the amplifier 6, and the terminal 1B is connected to the negative input terminal (-) of the amplifier 6 via the resistor R1. The amplifier 6 is a negative feedback amplifier having an output terminal connected to a negative input terminal (-) through a resistor R2, and outputs a voltage V generated between terminals 1A and 1B to resistors R1 and R2.
2 with a gain of 2. Then, the voltage V ′ output from the amplifier 6 is compared with the judgment voltage Vref by the voltage comparator 7, and when the voltage exceeds the judgment voltage Vref, a temperature detection signal is output.

The operation of the above configuration will be described below.

First, the potential V between the terminals 1A and 1B (hereinafter referred to as the potential V)
The voltage V) is expressed as V = IR (2) from the constant current I and the conductor resistance R of the conductive pattern 2 according to Ohm's law.

As shown by the equation (1), the resistance value of the conductor resistance R of the conductive pattern 2 increases as the temperature increases. Therefore, the voltage V between the terminals 1A and 1B also increases. The temperature is detected by comparing the increase in the voltage V between the terminals 1A and 1B due to the temperature rise at this time with the judgment voltage Vref for temperature detection previously obtained from the equations (1) and (2) by the voltage comparator 7. Then, a temperature detection signal is generated.

In addition, generally used conductive patterns 2
Is extremely small, the voltage V between the terminals 1A and 1B also has a small value. For this reason, the judgment by the voltage comparator 7 is performed with a small difference in voltage level, and it is difficult to make an accurate judgment. Therefore, here, as shown in FIG. 2, the voltage V between the terminals 1A and 1B is amplified by the amplifier 6 and set as the voltage V ', and then the determination is made by the voltage comparator 7.

The voltage V 'at this time is as follows: V' = V * (R2 / R1) (3), and the temperature judgment voltage Vref is calculated by the equations (1), (2),
It can be obtained from (3).

According to the above configuration, since the resistance value is converted to a voltage value, converted to an appropriate level, and compared with the temperature determination voltage, the detection accuracy can be improved.

FIG. 3 is a block diagram showing the configuration of a second embodiment of the printed circuit board temperature detecting device according to the present invention.
Note that, in FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and duplicate description will be omitted.

In the temperature detector shown in FIG. 3, external interface terminals 1A, 1B1 to 1Bn
Are provided, and several places (here, n places) of the conductive pattern 2 stretched over the printed board 1 are connected to the terminals 1B1 to 1B1.
1Bn. Then, each resistance value between the external interface terminal 1A and the terminals 1B1 to 1Bn is measured by the resistance meter 3.

According to the above configuration, for example, the printed circuit board 1
Even when the printed circuit board is burned out due to an abnormality of the electric circuit 8 mounted on the printed circuit board and the conductive pattern 2 is deformed or cut, the resistance value between any of the terminals 1A and the terminals 1B1 to 1Bn is in a high resistance state. By reading the information, it is possible to identify at which portion on the printed circuit board 1 the burnout accident has occurred.

Therefore, the printed circuit board temperature detecting device according to each of the above-described embodiments detects the temperature by arranging conductive patterns at every corner of the printed circuit board and measuring the conductor resistance having the temperature characteristic. There is no need to arrange components for temperature measurement on the substrate. Therefore, even on a large printed circuit board, the temperature can be detected without increasing the circuit scale.

In each of the above embodiments, the conductor pattern extends all over the printed circuit board.
It goes without saying that only the portion that needs to be detected is required.

[0032]

As described above, according to the present invention, it is possible to provide a printed circuit board temperature detecting device capable of detecting an abnormal temperature at an arbitrary location regardless of the size of the printed circuit board.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a printed circuit board temperature detecting device according to the present invention.
FIG. 3 is a block diagram illustrating a configuration of the embodiment.

FIG. 2 is a circuit diagram showing a specific example of an ohmmeter and a temperature detection signal generation circuit in the embodiment of FIG.

FIG. 3 is a block diagram showing a configuration of a second embodiment of the printed board temperature detecting device according to the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional printed circuit board temperature detecting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Printed circuit board 1A-1B, 1B1-1Bn External interface terminal 2 Conductive pattern 3 Resistance meter 4 Temperature detection signal generation circuit 5 Constant current source 6 Amplifier 7 Voltage comparator 8 Electric circuit 9 Temperature sensor R1, R2 Resistance

Claims (4)

(57) [Claims] A printed circuit board (1) is provided with at least a pair of external interface terminals (1A, 1B), and a conductor pattern (2) is wired at least on the printed circuit board (1) where temperature detection is required. A conductor wiring means having both ends connected to the pair of external interface terminals (1A, 1B), and a resistor for measuring a resistance value between the pair of external interface terminals (1A, 1B) of the printed circuit board (1). Value measurement means (3)
And a temperature detection signal generating means (4) for generating a temperature detection signal when the resistance value obtained by the means (3) exceeds a predetermined value. Detection device. The resistance value measuring means (3) includes a constant current source (5) for supplying a constant current to the conductor pattern (2) through the pair of external interface terminals (1A, 1B). 2. A voltage value generated in the conductor pattern (2) when a current flows is read as a resistance value.
4. The printed circuit board temperature detecting device according to 1. 3. The temperature detection signal generating means (4) compares the voltage value read by the resistance value measuring means (3) with a prescribed value corresponding to a preset detection temperature, and compares the voltage value. 3. The printed circuit board temperature detecting device according to claim 2, wherein a temperature detecting signal is generated and output when the input voltage value exceeds a specified value. 4. The printed wiring board according to claim 1, wherein
(1) and multiple external interface terminals (1A, 1B1-
1Bn), and selectively connect any part of the conductor pattern (2) wired on the printed circuit board (1) to any of the external interface terminals (1A, 1B1-1Bn), and measure the resistance value. 2. The printed circuit board temperature measuring device according to claim 1, wherein the means (3) selectively measures a resistance value between any of the plurality of external interface terminals (1A, 1B1-1Bn). apparatus.