JPH0231908Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a printed circuit board protection device used in a transistor inverter device.

Inverter devices include those using transistor elements and those using thyristor elements. In particular, the base circuit system of the former inverter device using transistor elements is complicated, unlike the gate firing circuit of the latter inverter device using thyristor elements. Figure 1 is a schematic configuration diagram of an inverter device using transistor elements.
is a converter device, 2 is a smoothing capacitor, 3 is an inverter device, and 4 is a base circuit. Also, 3
a is the main circuit transistor of the inverter device 3;
A collector C of this transistor 3a is connected to the positive electrode side of the converter device 3, and an emitter E is connected to its negative electrode side. The base B of the transistor 3a is connected to the base circuit 4. Since the output voltage of the converter device 1 shown in FIG. 1 is normally about 280V, it is assumed that an overcurrent flows through the transistor 3a of the inverter device 3 for some reason. Due to this overcurrent, the emitter portion of the transistor 3a is fused and the emitter becomes open, and the collector C and base B of the transistor 3a are short-circuited. Therefore, the transistor 3a
The area between collector C and base B loses its semiconductor function, and the output voltage (approximately 280 V) of converter device 1 is applied to base circuit 4 through collector C and base B. As a result, a large current I flows into the base circuit 4 as indicated by the arrow in the figure. Then, the electronic components mounted on the printed circuit board (not shown) forming the base circuit will burn due to the large current, which may cause the fire to spread to the board and destroy the printed circuit board. Further, as described above, even if combustion does not occur, the large current I is a direct current, so if an arc occurs, the current will be interrupted, which is extremely problematic. In the worst case, not only the printed circuit board constituting the base circuit but also the control circuit printed circuit board may be destroyed by the large current.

This invention was made in view of the above circumstances, and an object thereof is to provide a printed circuit board protection device that prevents electronic components and printed circuit boards from burning.

An embodiment of this invention will be described below with reference to the drawings, in which the same parts as in FIG. 1 are designated by the same reference numerals. In FIG. 2, reference numeral 11 denotes a printed circuit board constituting the base circuit 4, and a terminal 12a of the base circuit printed pattern 12 of this board 11 is connected to the base B of the main circuit transistor 3a. 1
2b is a fusing portion formed by narrowing the width of a portion of the steel foil of the printed pattern 12. 13 is a ground circuit printed pattern of the printed circuit board 11, and the emitter E of the main circuit transistor 3a is connected to the terminal 13a of this pattern 13. 14
is a Zener diode, and the cathode of this Zener diode 14 is connected to a connection pattern 12c connected to a fusing portion 12b of the printed pattern 12. The anode of the Zener diode 14 is connected to the ground circuit printed pattern 13 via a diode 15 of the illustrated polarity.

Next, the operation of the above embodiment will be described. now,
As described in FIG. 1, when the base B and collector C of the transistor 3a are short-circuited, the terminals 12a and 13 of the printed circuit board 11 are
A DC voltage is applied to a. This DC voltage is applied to the series circuit of the Zener diode 14 and the diode 15, and between the patterns 12 and 13, the Zener voltage of the Zener diode 14 and the diode 1
The voltage is clipped to the sum of the forward voltages of 5. For example, the Zener voltage of the Zener diode 14 is approximately
When set to 5V, the sum with the forward voltage of diode 15 is clipped to about 6V. As described above, since the voltage between the patterns 12 and 13 is clipped to a predetermined voltage, no high voltage is applied between the patterns 12 and 13. At the same time, when a high voltage is clipped to a low voltage by the series circuit of the Zener diode 14 and the diode 15, a large current flows through the series circuit. Therefore, the Zener diode 14 and the diode 15 are both destroyed and welded together, resulting in a short circuit state. As a result, a large current continues to flow through the base circuit printed pattern 12,
This current melts the fusing portion 12b and cuts that portion. That is, the copper foil in the fusing portion 12b is instantaneously scattered and cut. Therefore, arcing will no longer occur.

As described above, even if the main circuit transistor 3a is damaged, only a portion of the base circuit pattern is destroyed, thereby eliminating problems such as burnout of the printed circuit board.

As described above, according to this invention, a series circuit consisting of a Zener diode and a diode is connected between the base circuit pattern of a printed circuit board and the ground circuit printed pattern of the board, and the width of a part of the base circuit pattern is Because it is formed narrowly, even if the main circuit transistor of the inverter device breaks down, it is possible to prevent the base circuit printed circuit board from being burned out, and at the same time, it is possible to prevent the spread of the burnout to other printed circuit boards. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an inverter device using transistor elements as a conventional example, and FIG. 2 is a schematic diagram of an embodiment of the invention. 3... Inverter device, 3a... Main circuit transistor, 11... Printed circuit board, 12... Base circuit printed pattern, 12b... Fusing part,
13...Earth circuit print pattern, 14...
Zener diode, 15... diode.

Claims (1)

[Claim for Utility Model Registration] In a transistor inverter device in which the main circuit is formed of NPN transistor elements, a base circuit print pattern of a printed circuit board to which the base of the NPN transistor element is connected and a ground circuit print of the board. A series circuit consisting of a Zener diode and a diode is connected between the patterns, and the above-mentioned
A printed circuit board protection device characterized in that the width of a portion of the printed pattern is narrowed over a predetermined length between the base circuit printed patterns to which the base of an NPN transistor element is connected.