Reverse connection prevention protection circuit for vehicle storage battery

Abstract

A reverse connection prevention protection circuit for a vehicle storage battery comprises a PMOS tube, a voltage stabilizing diode and a voltage regulating resistor, a drain electrode of the PMOS tube is connected with a positive electrode of the storage battery, a source electrode of the PMOS tube is grounded through a load connected in series, a grid electrode of the PMOS tube is grounded through the voltage regulating resistor connected in series, a positive electrode of the voltage stabilizing diode is connected with the grid electrode of the PMOS tube, and a negative electrode of the voltage stabilizing diode is connected with the source electrode of the PMOS tube. Based on the general PMOS tubes in the market, the reverse connection prevention circuit is small in heat productivity, small in size, easy in PCB layout, low in price and easy to purchase, has a reverse connection prevention function, is small in voltage drop, and can be applied to large-current application occasions.

Description

Technical Field

[0001] The utility model belongs to the technical field of power supply circuits, and in particular relates to a vehicle battery anti-reverse connection protection circuit. Background Art

[0002] The battery in a fuel-powered vehicle is generally a lead-acid battery that provides voltage for the vehicle's electronic devices. There is usually a fuse to protect the vehicle from reverse polarity, but reverse polarity can still damage the vehicle's devices. If the vehicle's electrical devices are not protected against reverse polarity, care must be taken when replacing the battery, otherwise the devices are likely to be damaged. Therefore, in this case, a reverse polarity protection circuit will be a useful supplement to the vehicle's electrical devices. To protect the vehicle's electrical devices from reverse polarity connection, the traditional method is to use a Schottky diode. The positive terminal of the vehicle battery is connected to the positive terminal of the Schottky diode, and the negative terminal of the Schottky diode is connected to one end of the load. The other end of the load is connected to the negative terminal of the battery. This method has the following disadvantages:

[0003] 1. Large size: Schottky diodes are usually packaged as D2PAK3, with a size of 15.88mm*10.29mm*4.83mm. They are prone to heat and have limited PCB layout.

[0004] 2. High cost: For Schottky diodes that can pass large currents, the price of each one is high;

[0005] 3. Difficult to purchase: Schottky diodes are semiconductors and are mainly produced by foreign manufacturers. Due to global material shortages, procurement is difficult;

[0006] 4. The loss of Schottky diodes is large, and the forward voltage difference is high. When the input power supply voltage is very high, a small voltage drop may have no effect on the subsequent stage, and the current is also relatively small at this time. However, when the input power supply voltage is very low, even a small amount of voltage drop is unacceptable, and as the load current increases, the voltage drop of the diode becomes larger and larger, resulting in failure to meet the requirements of the subsequent load.

[0007] 5. Schottky diodes cannot meet the needs of high current applications. Utility Model Content

[0008] Based on this, in order to solve the above technical problems, a vehicle battery anti-reverse connection protection circuit is provided.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A vehicle battery reverse connection protection circuit is characterized by comprising a PMOS tube, a voltage regulator diode and a voltage regulating resistor, wherein the drain of the PMOS tube is connected to the positive electrode of the battery, the source is grounded via a series load, and the gate is grounded via a series voltage regulating resistor, the positive electrode of the voltage regulator diode is connected to the gate of the PMOS tube, and the negative electrode is connected to the source of the PMOS tube.

[0011] The utility model provides a vehicle battery reverse polarity protection circuit, which is based on a PMOS tube commonly used on the market. It has low heat generation, small size, easy PCB layout, low price, and is easy to purchase. While having a reverse polarity protection function, it has a small voltage drop and can meet high current applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural diagram of the utility model;

[0013] Figure 2 This is a relationship diagram between the on-state internal resistance and VGS of the PMOS tube of the present invention. DETAILED DESCRIPTION

[0014] The following will illustrate the implementation of the present utility model in conjunction with the drawings in the specification. It should be noted that the implementation methods involved in this specification are not exhaustive and do not represent the only implementation methods of the present utility model. The following corresponding embodiments are only for the purpose of clearly illustrating the utility model content of the utility model patent and are not intended to limit its implementation methods. For ordinary technicians in this field, different forms of changes and modifications can be made on the basis of the description of this embodiment. All obvious changes or modifications that belong to the technical concept and utility model content of the present utility model are also within the scope of protection of the present utility model.

[0015] like Figure 1 As shown, an embodiment of the present application provides a vehicle battery reverse connection protection circuit, including a common-mode inductor M1, a PMOS tube T2, a voltage regulator diode Z2, a voltage regulating resistor R4, a first capacitor C9, a second capacitor C10, a third capacitor C11, a fourth capacitor C12, a fifth capacitor C13 and a sixth capacitor C14.

[0016] Coil N1 of common-mode inductor M1 is connected in series between drain D of PMOS transistor T2 and the positive terminal of battery V5. Both ends of coil N2 are grounded. Terminals 1 and 3 are connected together, and terminals 2 and 4 are connected together. Common-mode inductor M1 primarily prevents common-mode noise from battery V5 from affecting subsequent circuits, improving EMC performance.

[0017] The source S of the PMOS transistor T2 is connected to the ground terminal connected to the negative electrode of the battery V5 via a series-connected load R5 , and the gate G is connected to the ground terminal via a series-connected voltage-regulating resistor R4 .

[0018] Among them, the PMOS tube T2 is packaged in DFN5 with a size of 6.3mm*5.3mm*1.1mm, which generates little heat and is easy to layout on the PCB.

[0019] The positive electrode of the voltage stabilizing diode Z2 is connected to the gate G of the PMOS transistor T2 , and the negative electrode is connected to the source S of the PMOS transistor T2 .

[0020] The two ends of the first capacitor C9 are respectively connected to the drain D and the gate G of the PMOS transistor T2 to achieve high-frequency amplification and filtering. The frequency response and gain of the circuit can also be adjusted according to the size of the capacitor.

[0021] The two ends of the second capacitor C10 are respectively connected to the drain D and source S of the PMOS transistor T2, and mainly play the role of damping, protection, voltage balancing, as well as filtering DS voltage spikes and improving EMI.

[0022] One end of the third capacitor C11, the fourth capacitor C12, and the fifth capacitor C13 are all connected to the source S of the PMOS transistor T2, and the other ends are all connected to the above-mentioned ground terminal. The third capacitor C11 is a high-frequency filter capacitor for filtering out noise. The fourth capacitor C12 and the fifth capacitor C13 are power storage capacitors, which are mainly used to deal with load instability caused by a sudden drop in the input power supply.

[0023] The ends of the sixth capacitor C14 are respectively connected to the gate G and source S of the PMOS transistor T2. As a smoothing capacitor, it can help stabilize the working state of the PMOS transistor T2 and improve its frequency response characteristics. It can also improve the circuit's anti-interference ability and reduce the impact of external noise on the circuit.

[0024] The working principle of the circuit in the embodiment of the present application is as follows:

[0025] When the battery V5 is connected in the positive direction, the battery voltage first passes through the common-mode inductor M1 and then to the body diode Z3 of the PMOS tube T2 from the drain D to the source S, then passes through the inside of the PMOS tube T2 to the gate G, and finally passes through the voltage regulating resistor R4 to the ground and back to the negative electrode of the battery. As the VGS voltage of the PMOS tube T2 gradually exceeds Vth, the PMOS tube T2 is fully turned on.

[0026] By adjusting the voltage regulating resistor R4, the VGS voltage can be adjusted, thereby adjusting the conduction capability of the PMOS tube T2. The larger the VGS, the smaller the RDS (the conduction internal resistance of the PMOS tube T2) (see Figure 2 ), the smaller the loss, when the VGS voltage of PMOS tube T2 is -10V, the RDS is only 0.014mΩ, and the maximum current it can pass is 64A, which meets the needs of high current applications.

[0027] The voltage stabilizing diode Z2 can prevent the VGS voltage from exceeding the limit voltage. In this embodiment, a 10V voltage stabilizing diode is selected.

[0028] When the battery V5 is reversely connected ( Figure 1 In the figure, V6 is used to simulate the reverse connection state), the PMOS tube T2 is not conducting and its body diode Z3 cannot conduct in the reverse direction, which effectively protects the subsequent circuit.

[0029] After simulation, when the current passing through the load R5 is 239mA, the voltage drop across the PMOS tube T2 is only 46mV (0.046V). When the battery voltage is 12V, the output voltage after passing through the PMOS tube T2 is 11.95V, and normal anti-reverse polarity protection can be completed.

[0030] In the existing technology, when the current passing through the load is 236.62mA, the voltage drop across the anti-reverse diode is 168mV. When the battery voltage is 12V, the output voltage after passing through the anti-reverse diode is 11.83V. As the current increases, the voltage drop across the anti-reverse diode will become larger and larger.

[0031] As can be seen from the above, the embodiment of the present application provides a vehicle battery reverse polarity protection circuit, which is based on the PMOS tube commonly used on the market, has low heat generation, small size, easy PCB layout, low price, and easy procurement. While having the anti-reverse polarity function, it has a small voltage drop and can meet high current applications.

[0032] Obviously, those skilled in the art should realize that the above embodiments are only used to illustrate the present invention and are not used to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A vehicle battery anti-reverse connection protection circuit, characterized in that: The invention comprises a PMOS tube, a voltage-stabilizing diode and a voltage-regulating resistor. The drain of the PMOS tube is connected to the positive electrode of the battery, the source is grounded via a series load, the gate is grounded via a series voltage-regulating resistor, the positive electrode of the voltage-stabilizing diode is connected to the gate of the PMOS tube, and the negative electrode is connected to the source of the PMOS tube.

2. A vehicle battery reverse connection protection circuit according to claim 1, characterized in that: It also includes a common-mode inductor, one coil of the common-mode inductor is connected in series between the drain of the PMOS tube and the positive electrode of the battery, and both ends of the other coil are grounded.

3. A vehicle battery reverse connection protection circuit according to claim 2, characterized in that: It also includes a first capacitor, with two ends of the first capacitor connected to the drain and gate of the PMOS tube respectively.

4. A vehicle battery reverse connection protection circuit according to claim 1, characterized in that: It also includes a second capacitor, with two ends of the second capacitor connected to the drain and source of the PMOS tube respectively.

5. A vehicle battery reverse connection protection circuit according to claim 1, characterized in that: It also includes a third capacitor, a fourth capacitor and a fifth capacitor, one end of each of the third capacitor, the fourth capacitor and the fifth capacitor is connected to the source of the PMOS tube, and the other end is grounded.

6. A vehicle battery reverse connection protection circuit according to claim 1, characterized in that: The second embodiment also includes a sixth capacitor, both ends of which are connected to the gate and source of the PMOS tube respectively.

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