Surge protection circuit for 24V power port of automotive electronic device

Abstract

The utility model discloses an automobile electronic 24V power supply port surge protection circuit, which comprises a battery BT, a fuse F1, a fuse F2, a diode D1, a diode D2, an inductor L1 and a capacitor C1, the positive electrode of the battery BT is respectively connected with the fuse F1 and the fuse F2, the other end of the fuse F1 is connected with the positive electrode of the diode D1, a diode TVS2 and a large circuit load circuit 1, and the other end of the fuse F2 is connected with the positive electrode of the diode D1. And the other end of the fuse F2 is connected with the positive electrode of a diode D2, a diode TVS1 and a large circuit load circuit II. According to the utility model, on the premise of certain cost, through separation of the large-current circuit and the small-current control circuit, good transient surge voltage suppression can be realized for the control circuit, and a P1 pulse surge impact test and a P5A pulse surge impact test specified by an automotive electronic GB / T 21437.2 standard can be passed.

Description

Technical Field

[0001] The utility model relates to the technical field of automobile electronics, in particular to a surge protection circuit for a 24V power supply port of automobile electronics. Background Art

[0002] Due to the large number of wiring harnesses, small space and harsh electromagnetic environment in the car, the power supply system of the car is powered by the generator. The power supply stability is affected by factors such as the fluctuation of the generator speed, and the automotive electrical equipment will generate electromagnetic interference when it is turned on, running and turned off. Therefore, to solve this problem, the automotive electronic circuit must pass the P1 pulse test and P5A pulse test specified in the GB / T 21437.2 standard. The usual practice is to add multi-stage LC filtering and transient voltage suppression circuits to the circuit board of the automotive electrical equipment, but this circuit is not only costly but also large in size. This interference can affect the normal operation of the equipment through the power port of the automotive electrical equipment. The interference introduced from the automotive electronic power supply causes damage to the subsequent circuit and causes power supply failures of various electronic equipment, which is very likely to cause safety problems. At present, automotive electronic equipment is developing towards miniaturization, and the smaller the size of automotive electronic equipment, the better. With the growth of automobile consumption, there is also a requirement to reduce costs. At the same time, with the improvement of the degree of intelligence of automobiles, automotive electrical equipment will have many load-type actuators. The current of the automotive electronic power port is very large. The large current circuit uses inductors for filtering through traditional solutions. The inductors are very large in size and generate a lot of heat. Utility Model Content

[0003] The utility model aims to provide a surge protection circuit for a 24V power port of automotive electronics to solve the problems raised in the above-mentioned background technology.

[0004] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0005] A surge protection circuit for a 24V power port of automotive electronics comprises a battery BT, a fuse F1, a fuse F2, a diode D1, a diode D2, an inductor L1 and a capacitor C1, wherein the positive electrode of the battery BT is connected to the fuses F1 and F2 respectively, the other end of the fuse F1 is connected to the positive electrode of the diode D1, the diode TVS2 and a large circuit load circuit 1, the other end of the fuse F2 is connected to the positive electrode of the diode D2, the diode TVS1 and a large circuit load circuit 2, the negative electrode of the diode D1 is connected to the negative electrode of the diode D2, the negative electrode of the diode TVS3 and the inductor L1, the other end of the inductor L1 is connected to the capacitor C1 and a post-stage control circuit, and the other end of the capacitor C1 is connected to the other end of the diode TVS1, the other end of the diode TVS2, the positive electrode of the diode TVS3 and the negative electrode of the battery BT.

[0006] As a further technical solution of the present utility model: the model of the diode TVS1 is PTBJ43CA.

[0007] As a further technical solution of the present utility model: the model of the diode TVS2 is PTBJ43CA.

[0008] As a further technical solution of the utility model: the model of the diode TVS3 is SM8S36A.

[0009] As a further technical solution of the utility model: the diode D1 and the diode D2 are both rectifier diodes.

[0010] Compared with the prior art, the beneficial effects of the utility model are:

[0011] Under the premise of certain cost, the utility model can achieve good transient voltage suppression and filtering for the control circuit by separating the large current circuit and the small current control circuit, and can also pass the P1 and P5A pulse impact tests specified in the GB / T21437.2 standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a circuit diagram of the utility model. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the utility model are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0014] Reference Figure 1 A surge protection circuit for a 24V power port of automotive electronics includes a battery BT, a fuse F1, a fuse F2, a diode D1, a diode D2, an inductor L1 and a capacitor C1. The positive electrode of the battery BT is connected to the fuse F1 and the fuse F2 respectively, the other end of the fuse F1 is connected to the positive electrode of the diode D1, the diode TVS2 and a large circuit load circuit one, the other end of the fuse F2 is connected to the positive electrode of the diode D2, the diode TVS1 and a large circuit load circuit two, the negative electrode of the diode D1 is connected to the negative electrode of the diode D2, the negative electrode of the diode TVS3 and the inductor L1, the other end of the inductor L1 is connected to the capacitor C1 and a post-stage control circuit, and the other end of the capacitor C1 is connected to the other end of the diode TVS1, the other end of the diode TVS2, the positive electrode of the diode TVS3 and the negative electrode of the battery BT.

[0015] The model of diode TVS1 is PTBJ43CA. The model of diode TVS2 is PTBJ43CA. The model of diode TVS3 is SM8S36A. Diode D1 and diode D2 are both rectifier diodes.

[0016] Here’s how it works:

[0017] This circuit must first separate the high-current load circuit and the low-current control circuit through the circuit diagram. The low-current control circuit has a low withstand voltage and is extremely sensitive to electromagnetic interference. The high-current load has a large current and usually has a high withstand voltage, and is insensitive to electromagnetic interference. If not separated, all currents pass through the reverse diode. Because the reverse diode has a large voltage drop when working in the forward direction, the heat is very serious. If the temperature is too high, the circuit safety cannot be guaranteed, and the circuit power consumption will also increase. If other solutions are used, not only will the circuit cost be expensive, but it will also occupy PCB board space, so the high-current load circuit and the low-current control circuit separation formula are used.

[0018] First of all, in order to solve the problem of P5A, automotive electronic electrical equipment must withstand the P5A pulse impact with a voltage amplitude of ﹢174V, a time of 350mS and an internal resistance of 2 ohms. Only the 6600W high-power automotive-specific transient voltage suppression diode TVS3, model SM8S33A, can be selected. This TVS diode is currently only unidirectional in terms of technology, and the bidirectional power is relatively small, so it cannot withstand the P5A impact.

[0019] The above principle can only solve the problem of withstanding P5A pulse impact. When testing P1 pulse, if there is no TVS1 and TVS2, the P1 negative pulse impact can only flow back from the large circuit load circuit due to the obstruction of S3J, and the large current load circuit may be damaged by the impact. At this time, the selection of TVS1 and TVS2 is very important, and the circuit material cost cannot be increased, because the circuit has already set up a higher cost TVS3, and it is not appropriate to add the same high cost TVS1 and TVS2. However, the transient power of low-priced devices must be very small, and they will inevitably be short-circuited and damaged when subjected to the large energy impact of P5A.

[0020] It is necessary to ensure that the cost of TVS1 and TVS2 is low (small transient power), and it is also necessary to ensure that they are not damaged during the P5A pulse impact. The working voltage of TVS2 and TVS2 must be above 40V to ensure that the minimum reverse breakdown voltage is 44.4V (min). When the pulse P5A impacts, TVS1 will reversely break down before TVS2 and TVS3 and then clamp, because the highest reverse breakdown voltage of TVS1 is generally 40V (min), 40V is lower than 44.4V, and the TVS tube with low breakdown voltage reacts first, because TVS1 and TVS2 break down later than TVS3 during the P5A pulse overvoltage impact, or even do not break down, so they will not be damaged due to overvoltage. Therefore, the working voltage of TVS1 and TVS2 in this circuit is better to be 43V, with a transient power of 600W and low cost, and the model is PTBJ43A.

[0021] At the same time, when P1 pulses, since the pulse amplitude reaches -600V, S3J can force the -600V pulse to make TVS1 and TVS2 forward-conducted and realize reflux due to the reverse blocking function of the diode. The negative overvoltage of P1 pulse is due to the forward conduction of TVS1 and TVS2, and the conduction voltage VF is usually about 0.7V. Such a low voltage will not cause any impact on the subsequent circuit.

[0022] Special attention should be paid to: The working voltage selection of TVS1 and TVS2 cannot only consider the later breakdown than TVS1, because if the working voltage is too high, the reverse breakdown voltage will be too high. Although it can break down later than TVS3 or even not break down when hit by P5A pulse, it can solve the problem of tolerating P5A impact, but when facing P1 pulse impact, because the working voltage of TVS1 and TVS2 is too high, it cannot reversely break down and achieve clamping. Due to the reverse blocking effect of S3J, the P1 negative pulse overvoltage is forced to return only through the large current load circuit, which may cause the large current load circuit to suffer from the P1 negative pulse overvoltage and cause harmful damage.

[0023] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0024] In addition, it should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment have also been appropriately combined to form other implementation modes that are easy for those skilled in the art to understand.

Claims

1. A surge protection circuit for a 24V power port of automotive electronics, comprising a battery BT, a fuse F1, a fuse F2, a diode D1, a diode D2, an inductor L1 and a capacitor C1, characterized in that: The positive electrode of the battery BT is connected to fuse F1 and fuse F2 respectively, the other end of fuse F1 is connected to the positive electrode of diode D1, diode TVS2 and large circuit load circuit one, the other end of fuse F2 is connected to the positive electrode of diode D2, diode TVS1 and large circuit load circuit two, the negative electrode of diode D1 is connected to the negative electrode of diode D2, the negative electrode of diode TVS3 and inductor L1, the other end of inductor L1 is connected to capacitor C1 and the post-stage control circuit, and the other end of capacitor C1 is connected to the other end of diode TVS1, the other end of diode TVS2, the positive electrode of diode TVS3 and the negative electrode of battery BT.

2. The surge protection circuit for a 24V power port of automotive electronics according to claim 1, characterized in that: The model of the diode TVS1 is PTBJ43CA.

3. The surge protection circuit for a 24V power port of automotive electronics according to claim 1, characterized in that: The model of the diode TVS2 is PTBJ43CA.

4. The surge protection circuit for a 24V power port of automotive electronics according to claim 1, characterized in that: The model of the diode TVS3 is SM8S36A.

5. The surge protection circuit for a 24V power port of automotive electronics according to claim 4, characterized in that: The diode D1 and the diode D2 are both rectifier diodes.

Images