JPS60200728A - Surge protecting device for power supply system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Technical fields> The present invention relates to a surge protection device in a power supply system.

BACKGROUND TECHNOLOGY> For example, in the power supply system of a vehicle, which is composed of an alternator 1, a battery 2, and an electric load 3 of various electrical components and electronic devices, as shown in FIG. , etc., various transient voltages called surges are generated in the power supply line A by turning the electric load 3 on and off. Semiconductor components such as ICs used in electronic devices are weak against such transient voltages, and may be damaged unless some protection measures are taken.

Of the transient voltages, the one with the highest energy is called the load damp buzz generated by the alternator, and in the schematic waveform diagram of Fig. 2, its peak voltage Vp is 60 to 70V, and the duration t is 0.2. It may even reach about 0.3 sec.

Therefore, conventionally, as shown in Fig. 1, for each electronic device of the electric load 3, a surge absorbing element 4 such as a voltage regulator diode is connected between the power source and the ground to protect the circuit inside the electronic device. I have to.

In the figure, 5 is a field coil, 6 is a voltage regulator, 7 is a charge lamp, and 8 is an ignition switch.

However, with the conventional surge protection method in which a surge absorption element is provided for each electronic device, the number of surge absorption elements increases as the number of electronic devices mounted on a vehicle increases, which is disadvantageous in terms of cost. . Further, since the failure mode of the surge absorbing element is usually Show 1, there is a possibility that the reliability of the vehicle electrical system may be lowered. Furthermore, in order to withstand high-energy transient voltages such as load dump surges, it is necessary to use a surge absorption element with a high power rating, which not only reduces costs but also reduces the size of electronic devices themselves. However, there are some problems.

(Objective of the Invention) The present invention has been made in view of the above-mentioned circumstances, and by providing the alternator's rectifier circuit with a surge absorption function, it is unnecessary to install surge absorption elements on the electronic equipment side, and the number of surge absorption elements can be reduced. The purpose of the present invention is to provide a surge protection device that can significantly reduce the number of surges, thereby reducing costs and improving the reliability of vehicle electrical systems.

<Summary of the Invention> Therefore, in the present invention, a group of diode pairs constituting a rectifier circuit that converts alternating current generated by an alternator into direct current, that is, a plurality of diodes formed by connecting two diodes in series between an alternator output terminal and ground. At least one of the pairs is configured using a constant voltage diode having predetermined constant voltage characteristics, and the transient voltage generated in the power supply line of the power supply system is passed through the constant voltage diode in the rectifier circuit. This protects electronic equipment connected to the power supply line by grounding it.

<Example> The present invention will be explained in detail below.

FIG. 3 is a diagram showing the main part of an embodiment of the present invention.

In the figure, 11 is an alternator, and stake coil 1
2. In addition to the rectifier circuit 13 of this embodiment having a surge protection function, it is provided with a field coil, a voltage regulator, etc. (not shown). Reference numeral 14 denotes an output terminal of the alternator 11, which is connected via a power line 15 to a battery 16 and an electric load 17 such as various electrical components and electronic devices.

Further, the rectifier circuit 13 having the surge protection function is composed of a number of diode pairs corresponding to the number of output terminals of the stator coil 12, and for example, when there are three output terminals as in this embodiment, three diode pairs are provided. diode pair 13A, 1
It is composed of 3B and 13C.

These diode pairs 13A to 13C are two diodes connected in series in a forward direction from the ground side to the alternator output terminal 14 side, respectively.
The output end of stator coil 12 is connected between the two diodes. In the rectifier circuit 13 of this embodiment, among the three diode pairs 13A to 13C, two diode pairs 13A and 13B are similar to the conventional one and use normal rectifying diodes DI and Dz, but the other one The two diode pairs 13C are constant voltage diodes Z D + having predetermined constant voltage characteristics.

Z D 2, such a constant voltage diode Z
Diode pair 13G with D + , Z D z
By providing a surge protection function.

Next, the operation will be explained with reference to FIGS. 4 to 6.

First, the operation with respect to the transient voltage generated within the alternator 11 will be explained.

The transient voltage generated from the alternator 11 is the aforementioned load dump surge, and the source of this is the overvoltage generated from the stator coil 12.

Therefore, the overvoltage is caused by the constant voltage diode ZDI.

A case where the problem occurs in a coil that is not directly connected to the diode pair 13c using ZD2 and a case where the problem occurs in a coil that is directly connected will be explained separately.

In the former case, for example, if an overvoltage Vs occurs in the stator coil 11 connected to the diode pair 13A as shown in FIG. to be applied. This overvoltage Vs is caused by the diode pair 13G
Each constant voltage diode Z01゜Z Dz (7) When the relationship of Vs>V1+■2 with respect to the s-ner voltages VI and V2 is established, the overvoltage Vs is absorbed through the path shown by the broken line in Fig. 4. . Therefore, this overvoltage Vs is not directly applied to the electronic device of the electric load 17, and the circuit inside the electronic device can be protected.

In the latter case, the overvoltage V in the stator coil 12
When s occurs, the overvoltage Vs is applied to the constant voltage diode ZDz of the diode bear 13C, so the overvoltage Vs
If Vs>V with respect to the Zener voltage V2 of the constant voltage diode ZDz, the overvoltage Vs will be absorbed along the path shown by the broken line in FIG. Therefore, the circuit inside the electronic device can be protected in the same way.

On the other hand, when an overvoltage Vs occurs, it is rectified via the output terminal 14 of the alternator 11 with respect to a transient voltage generated not in the alternator 11 (but in a transient voltage generation source such as an electric load 17 connected to the power supply line 15). Since the overvoltage Vs is applied to the circuit 13, Vs>V.

If the relationship is +V2, the overvoltage Vs can be absorbed through the path shown by the broken line in FIG. Therefore, in this case as well, the circuit inside the electronic device can be protected.

In addition, since the constant voltage diodes Z Dr and Z D 2 have exactly the same function as the normal rectifying diodes DI and D2 in the forward direction, they do not interfere with the normal alternator generated voltage in any way.

By the way, the constant voltage characteristics (Zener voltage) of the constant voltage diodes ZD, ZD2 are set as follows.

The elements that determine the Zener voltages V, V2 of the constant voltage diodes Z D + and Z D z are the alternator generated voltage A in the normal control range, the maximum value B of the DC voltage that may be applied from outside the alternator, and the surge absorption means. There is an effective value C for the transient voltage of the electronic equipment to be protected when no protection is provided.

Therefore, considering these, A<V, B<V.

It is necessary to set the Zener voltages V, , V2 with the constraint b of +Vz and C>Vl +V2.

Here, generally A#16V; B#24V (jumper start of 2 batteries in series), C=30~40■ (I
Estimated value from DC rating such as C), so 24<
V, +V2<40 and V2>16 may be set as a guide.

<Effects of the Invention> As described above, according to the present invention, at least one of the diode pair groups of the rectifier circuit existing in the power supply system is formed with a constant voltage diode, so that the rectifier circuit has a surge absorption function. With this configuration, there is no need to provide a surge absorbing means for each electronic device, and it is possible to reduce costs and significantly improve the reliability of vehicle electrical systems and the like.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional example of a power supply system, Fig. 2 is a diagram showing an example of the waveform of loader 7 surge generated in an alternator, Fig. 3 is a main part configuration diagram showing an embodiment of the present invention, 4 to 6 are diagrams for explaining the operation of the above embodiment, and the fourth
The figure is an explanatory diagram when a transient voltage occurs in a stator coil that is not directly connected to a diode pair that uses constant voltage diodes. Figure 5 shows a transient voltage that occurs in a stator coil that is directly connected to a diode bare that uses constant voltage diodes. FIG. 6 shows an explanatory diagram for the case where a transient voltage occurs in a part other than the alternator. 11...Alternator 12...Stator coil 1
3... Rectifier circuit 14... Alternator output terminal 1
5...Power line 16...Battery 17...
Electric load DI, Dz...Diode ZD,
, ZD2... Constant voltage diode patent applicant Nissan Motor Co., Ltd. agent Patent attorney Fujio SasashimaFigure 3 11 Figure 4

Claims (1)

[Claims] In a power supply system that includes an alternator equipped with a rectifier circuit that rectifies alternating current generated in a stator coil into direct current, and an electric load that takes in power from a power line connected to the output terminal of the alternator, two diodes are connected from the ground side. It is constructed by connecting diode pairs in series so that they are in the forward direction toward the alternator output terminal side, and connecting the stator coil output terminals between these diodes, and providing them in parallel in correspondence with the number of stator coil output terminals. A surge protection device for a power supply system, characterized in that at least one diode bear of the rectifier circuit is configured using a constant voltage diode having predetermined constant voltage characteristics.