JPH05276643A - Overload detector - Google Patents

Abstract

PURPOSE:To provide an overload detector which can detect overload of electronic components mounted on each printed circuit board when multiple printed boards are arranged. CONSTITUTION:An example of protection object, i.e., a transistor Q, is mounted on a printed board 10 while a first temperature sensor 11 is mounted in the vicinity of the transistor Q and a second temperature sensor 12 is mounted at a position remoter from the transistor Q than the first temperature sensor 11. A decision circuit 13 for n-th channel receives temperatures T1n, T2n of its own printed circuit board 10 detected through the temperature sensors 11, 12 and produces an alarm indicating that n-th channel is defective if the temperature T1n is higher than an alarm temperature TLn and the temperature difference (T1n-T2n) is higher than a predetermined level Twn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload detecting device for detecting an overload of electronic parts on a printed circuit board.

[0002]

2. Description of the Related Art Generally, a transistor is used to drive an external load such as an actuator, and the transistor is mounted on a printed board. However, when an external load is short-circuited and an overcurrent flows through the transistor, the transistor is destroyed. Therefore, a device for protecting the transistor from the overload is required.

Conventionally, this type of overload detection device is provided with a temperature sensor for detecting heat generation of a transistor on a printed circuit board in the vicinity of a transistor to be protected, and when the detected temperature is a predetermined value or more, an overload is caused. It is judged that it has occurred,
It is configured to reduce the drive current of the transistor and issue an alarm.

[0004]

However, in the above-mentioned conventional overload detection device, as shown in FIG. 2, a large number of printed circuit boards (shown as channels A, B, and C) are arranged and the temperature on each printed circuit board is increased. When the sensor is provided, there is a problem in that each temperature sensor malfunctions because it is affected by heat generated by a transistor on an adjacent printed circuit board.

In view of the above-mentioned conventional problems, the present invention provides an overload detection device capable of accurately detecting an overload of an electronic component on each printed circuit board when a large number of printed circuit boards are arranged. The purpose is to

[0006]

SUMMARY OF THE INVENTION The present invention provides an overload detection device in which a large number of printed circuit boards are arranged to detect an overload of electronic components on each printed circuit board, in the vicinity of the electronic component on each printed circuit board. Of the first temperature sensor disposed on the printed circuit board, a second temperature sensor disposed on a position farther from the electronic component than the first temperature sensor on each printed circuit board, and the first and second temperature sensors. And a determination means for determining that the electronic component on the printed circuit board is overloaded when the difference between the detected temperatures is equal to or more than a predetermined value.

[0007]

In the present invention, when the electronic component on the printed circuit board is overloaded, the temperature rise of the first temperature sensor arranged in the vicinity of the electronic component is faster than that of the second temperature sensor. The difference becomes large and it is judged as an overload. On the other hand, when the electronic components on the adjacent printed circuit board are overloaded and the electronic components on the printed circuit board are not overloaded, the first and second temperature sensors on the printed circuit board are Since the detected temperature difference is small, it is not judged as an overload. Therefore, when a large number of printed circuit boards are arranged, malfunction can be prevented and overload of each electronic component can be accurately detected.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a transistor Q as an example of a protection target is mounted on a printed circuit board 10. Further, on the printed circuit board 10, a first temperature sensor 11 is mounted near the transistor Q, and a second temperature sensor 12 is mounted at a position farther from the transistor Q than the first temperature sensor 11. .. The outputs of the first and second temperature sensors 11 and 12 are input to the discrimination circuit 13 installed outside. Here, if an overload is determined, an alarm is issued.

A large number of such printed circuit boards 10 are arranged as shown in FIG. 2, and the respective external loads (not shown) are driven by the transistors Q on each printed circuit board 10. Therefore, when an external load short-circuits or the like and an overcurrent flows through the transistor Q, the transistor Q generates heat, and the temperature sensors 11 and 12 on the adjacent printed circuit board 10 detect a temperature rise due to heat conduction or convection. To do.

The temperature transitions a to f of the printed circuit board of channel B sandwiched between the two printed circuit boards of channels A and C in FIG. 2 will be described with reference to FIG. State a in which overload has not occurred in all channels A to C
Then, the detected temperatures of the temperature sensors 11 and 12 of the channel B are low and almost the same. Then, in a state b in which the transistor Q heats up due to the overload occurring in the adjacent channel A, the detected temperatures of the temperature sensors 11 and 12 of the channel B rise at almost the same gradient and become constant at a certain temperature.

In this state b, in the state c in which an overload occurs in the channel B and the transistor Q thereof generates heat,
The temperature detected by the first temperature sensor 11 in the vicinity of the transistor Q sharply rises, and the second temperature that is far from the first temperature sensor 11 increases.
The temperature detected by the temperature sensor 12 of FIG. Therefore, the determination circuit 13 can detect the overload of the channel B by detecting the difference ΔT _L between the detected temperatures.

In this state c, when the drive current of the transistor Q decreases, the temperature detected by the temperature sensors 11 and 12 stops increasing (overload protection state), and an alarm for channel B is issued to release the overload. Then, the temperatures detected by the temperature sensors 11 and 12 decrease.

Further, in a state d in which overheating occurs in both adjacent channels A and C and the respective transistors generate heat, the temperature detected by the temperature sensors 11 and 12 of the channel B are almost the same, and It is higher than the state b in which only the channel A is overloaded and lower than the state c in which the channel B is overloaded. Further, the state e in which the overload of the channel C is released is the same as the state b, and the state f in which the overload of the channels A and C is released is the same as the state a.

That is, the transistor Q as in the conventional example.
In the method of detecting only the first temperature sensor 11 in the vicinity of, the determination temperature T _D is the temperature in the state c in which the channel B is overloaded, and the state in which both the adjacent channels A and C are overloaded. It must be set between the temperature d and the temperature d, and if not set to a considerably high temperature, an erroneous judgment will be made. The same applies to the case where a plurality of protected components are mounted on the same board to individually protect each component.

Next, FIG. 4 shows the operation of the discrimination circuit 13 (FIG. 1) for the n-th channel printed circuit board. In steps S1 and S2, the temperature sensors 11 and 12, respectively.
The detected temperatures T _1n and T _2n are detected, and in the subsequent step S3, it is determined whether the detected temperature T _1n of the temperature sensor 11 is _{equal to} or higher than the alarm temperature T _Ln . The detected temperature T _1n is the alarm temperature T
In the case of more than _Ln, in step S4, the detected temperature difference between the temperature sensor 11,12 (T _1n -T _2n), it is determined whether or not more than the predetermined value T _wn, the n in the case of more than the predetermined value T _wn An alarm is issued indicating that the channel is defective (step S
5).

[0016]

As described above, according to the present invention, when the electronic component on the printed circuit board is overloaded, the temperature rise of the first temperature sensor arranged in the vicinity of the electronic component increases. Since it is faster than the second temperature sensor, the difference in the detected temperature becomes large, and it is determined that the load is overload. On the other hand, when the electronic components on the adjacent printed circuit board are overloaded and the electronic components on the printed circuit board are not overloaded, the first and second temperature sensors on the printed circuit board are Since the detected temperature difference is small, it is not judged as an overload.
Therefore, when a large number of printed circuit boards are arranged, malfunction can be prevented and overload of each electronic component can be accurately detected.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an overload detection device according to the present invention.

FIG. 2 is a side view showing a state in which a large number of printed circuit boards of FIG. 1 are arranged.

FIG. 3 is an explanatory diagram showing a detected temperature transition of a printed circuit board of channel B in the arrangement state of FIG.

4 is a flow chart for explaining the operation of the discrimination circuit of FIG.

[Explanation of symbols]

Q ... Transistor, 10 ... Printed circuit board, 11, 12 ...
Temperature sensor 13, discrimination circuit.

Claims (1)

[Claims] 1. An overload detection device in which a large number of printed circuit boards are arranged to detect an overload of an electronic component on each printed circuit board, the first temperature being arranged on each printed circuit board in the vicinity of the electronic component. A sensor, a second temperature sensor arranged on each printed circuit board at a position farther from the electronic component than the first temperature sensor, and a difference between detected temperatures of the first and second temperature sensors is a predetermined value. An overload detection device comprising: a determination unit that determines that the electronic component on the printed board is overloaded in the above case.