Reverse-connection-free protection circuit for polar capacitor
By combining resistors, Zener diodes, and NMOS transistors, the polarity protection problem of electrolytic capacitors in high-power products is solved, achieving reverse connection protection and heat reduction, resulting in a more efficient circuit design.
Patent Information
- Application Number
- CN202520028706.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-06
- Publication Date
- 2026-02-03
- Estimated Expiration
- 2035-01-06
AI Technical Summary
Existing high-power products have problems with electrolytic capacitor polarity protection circuits, such as high on-resistance, high power consumption, and severe heat generation. In addition, the surge current at startup is large, making it difficult to effectively protect electrolytic capacitors from reverse connection breakdown.
A combination circuit consisting of resistors R1, R4, and R6, Zener diode U1, and NMOS transistor Q3 is used to achieve reverse connection protection of the polarized capacitor by controlling the on and off states of Zener diode U1 and MOS transistor Q3. The on and off states of the MOS transistor are controlled by the voltage divider of the resistors and the reference voltage of the Zener diode to prevent breakdown in case of reverse connection.
It achieves unaffected charging and discharging of polarized capacitors during normal operation, prevents breakdown when reverse connected, and avoids additional power consumption and heat problems, with fewer and more streamlined circuit components.
Smart Images
Figure CN223872037U_ABST
Abstract
Description
[Technical Field]
[0001] This utility model relates to the field of circuit design technology, and in particular to a reverse connection protection circuit for polarized capacitors. [Background Technology]
[0002] Because electrolytic capacitors are polarized devices, reversing the polarity can lead to explosions and burnout. For low-power products, polarity protection for electrolytic capacitors is mostly achieved using reverse-biased diodes and MOSFETs. The unidirectional conductivity of the diodes and MOSFETs protects the electrolytic capacitor from polarity issues.
[0003] For high-power products, capacitor values are typically large, with electrolytic capacitors being the most common type. Since electrolytic capacitors are polarized, polarity protection is essential. Current electrolytic capacitor polarity protection circuits generally employ reverse-biased diodes and MOSFETs. However, high-power products have very high input currents, resulting in high on-resistance for diodes and MOSFETs, leading to high power consumption and significant heat generation. This limits the availability of suitable diodes and MOSFETs. Furthermore, the presence of large-capacity capacitors in the circuit results in significant inrush current during power-on, placing even higher demands on the polarity protection devices for electrolytic capacitors.
[0004] Therefore, it is necessary to propose a new technical solution to address the above problems. [Utility Model Content]
[0005] One of the purposes of this utility model is to provide a reverse-connection protection circuit for polarized capacitors, which not only ensures that the charging and discharging of polarized capacitors is unaffected during normal operation and prevents breakdown of polarized capacitors when reverse connected, but also eliminates the need for additional power reverse protection and solves the thermal problem of power reverse protection.
[0006] According to one aspect of this utility model, a reverse-connection protection circuit for polarized capacitors is provided, comprising resistors R1, R4, R6, and R7, a Zener diode U1, a polarized capacitor C1, a MOSFET Q3, a first power input terminal VIN_1, and a second power input terminal VIN_2. One end of resistor R1 is connected to the first power input terminal VIN_1, and the other end is connected to node A; one end of resistor R6 is connected to node A, and the other end is connected to the second power input terminal VIN_2; the Zener diode U1... The positive terminal of the transistor is connected to the first power input terminal VIN_1, and its negative terminal is connected to the second power input terminal VIN_2 via the resistor R7. Its control terminal is connected to node A. The first connection terminal of the MOSFET Q3 is connected to the first power input terminal VIN_1 via the resistor R4, and its second connection terminal is connected to the second power input terminal VIN_2. Its control terminal is connected to the negative terminal of the Zener diode U1. The positive terminal of the polarized capacitor C1 is connected to the first power input terminal VIN_1, and its negative terminal is connected to the first connection terminal of the MOSFET Q3.
[0007] Furthermore, when the positive terminal of the power supply is connected to the first power input terminal VIN_1 and the negative terminal of the power supply is connected to the second power input terminal VIN_2, the Zener diode U1 is in a forward conducting state, and the MOSFET Q3 is turned on; when the negative terminal of the power supply is connected to the first power input terminal VIN_1 and the positive terminal of the power supply is connected to the second power input terminal VIN_2, the Zener diode U1 is in a voltage regulating working state, and the MOSFET Q3 is turned off.
[0008] Furthermore, the resistance values of resistors R3 and R10 are selected to satisfy the following condition: when the negative terminal of the power supply is connected to the first power input terminal VIN_1 and the positive terminal of the power supply is connected to the second power input terminal VIN_2, the voltage drop across resistor R6 is greater than the internal reference voltage of the Zener diode U1, so that the Zener diode U1 is in a regulated operating state.
[0009] Furthermore, the voltage regulation value of the Zener diode U1 is less than the turn-on voltage value of the MOSFET Q3.
[0010] Furthermore, the MOS transistor Q3 is an NMOS transistor, and the first connection terminal, the second connection terminal, and the control terminal of the MOS transistor Q3 are the source, drain, and gate of the NMOS transistor, respectively.
[0011] Furthermore, the polarized capacitor C1 is an electrolytic capacitor.
[0012] Compared with the prior art, this utility model not only ensures that the charging and discharging of polarized capacitors are unaffected during normal operation and that polarized capacitors will not break down when reverse connected, but also eliminates the need for additional power reverse protection and solves the thermal problem of power reverse protection. [Attached Image Description]
[0013] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Among them:
[0014] Figure 1 This is a circuit diagram of a reverse-connection protection circuit for polarized capacitors in one embodiment of the present invention.
Detailed Implementation Methods
[0015] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0016] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments. Unless otherwise specified, the terms coupling, connection, linking, and interconnection used herein to indicate electrical connection mean direct or indirect connection. For example, A being connected to B includes both a direct electrical connection between A and B and a connection between A and B via electrical components or circuits.
[0017] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "back", "positive", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.
[0018] Please refer to Figure 1 As shown, it is a circuit diagram of a reverse-connection protection circuit for polarized capacitors in one embodiment of the present invention. Figure 1The reverse connection protection circuit shown for polarized capacitors includes resistors R1, R4, R6, and R7, Zener diode U1, polarized capacitor C1, MOSFET Q3, first power input terminal VIN_1, and second power input terminal VIN_2.
[0019] Among them, one end of resistor R1 is connected to the first power input terminal VIN_1, and the other end is connected to node A; one end of resistor R6 is connected to node A, and the other end is connected to the second power input terminal VIN_2; the positive terminal of Zener diode U1 is connected to the first power input terminal VIN_1, its negative terminal is connected to the second power input terminal VIN_2 via resistor R7, and its control terminal is connected to node A; the first connection terminal of MOSFET Q3 is connected to the first power input terminal VIN_1 via resistor R4, its second connection terminal is connected to the second power input terminal VIN_2, and its control terminal is connected to the negative terminal of Zener diode U1; the positive terminal of polarized capacitor C1 is connected to the first power input terminal VIN_1, and its negative terminal is connected to the first connection terminal of MOSFET Q3.
[0020] When the positive terminal of the power supply (not shown) is connected to the first power input terminal VIN_1 and the negative terminal of the power supply is connected to the second power input terminal VIN_2, the Zener diode U1 is in the forward conduction state and the MOSFET Q3 is turned on; when the negative terminal of the power supply is connected to the first power input terminal VIN_1 and the positive terminal of the power supply is connected to the second power input terminal VIN_2, the Zener diode U1 is in the reverse breakdown state (or the voltage regulation working state) and the MOSFET Q3 is turned off, thereby achieving reverse connection protection for the polarized capacitor C1.
[0021] exist Figure 1 In the specific embodiment shown, the polarized capacitor C1 is a large polarized capacitor, such as an electrolytic capacitor.
[0022] exist Figure 1 In the specific embodiment shown, MOS transistor Q3 is an NMOS transistor (N-Metal-Oxide-Semiconductor), and the first connection terminal, the second connection terminal, and the control terminal of MOS transistor Q3 are the source, drain, and gate of the NMOS transistor, respectively.
[0023] The values of resistors R3 and R10 are selected to satisfy the following conditions: when the negative terminal of the power supply is connected to the first power input terminal VIN_1 and the positive terminal of the power supply is connected to the second power input terminal VIN_2, the voltage drop across resistor R6 is greater than the internal reference voltage of Zener diode U1, so that Zener diode U1 is in reverse breakdown state (or voltage regulation operating state). The voltage regulation value of Zener diode U1 is less than the turn-on voltage of MOSFET Q3.
[0024] The following is a detailed introduction Figure 1 The diagram illustrates the working principle of a reverse-connection protection circuit for polarized capacitors.
[0025] ■Parameter Definition
[0026] ●The forward voltage drop of Zener diode U1 is U1_PN;
[0027] ●The PN junction voltage of MOSFET Q3 is Uq3_pn;
[0028] ●The voltage division between resistors R1 and R16 is Ur1_r6;
[0029] ●The turn-on voltage of MOSFET Q3 is Uq3_th.
[0030] ■ When the first power input terminal VIN1 is at a high level and the second power input terminal VIN2 is at a low level, it is defined as the normal operating state.
[0031] 1. Under normal operating conditions, path 1 (which is the path before the channel of MOSFET Q3 is turned on) is from the first power input terminal VIN1, resistor R4, body diode of MOSFET Q3 to the second power input terminal VIN2, and the source voltage of MOSFET Q3 is clamped at the Vq3_pn voltage.
[0032] 2. Path 2 is the first power input terminal VIN1, which reaches resistor R7 after passing through the PN junction of Zener diode U1. The gate voltage of MOSFET Q3 is (VIN1-U1_PN)>Uq3_th, so MOSFET Q3 is in the switching state and the channel of MOSFET Q3 is turned on. The body diode of Path 1 is bypassed by the channel.
[0033] 3. Based on the above analysis, after the channel of MOSFET Q3 is turned on, the polarized capacitor C1 can supply power to the downstream load, that is, the polarized capacitor C1 can realize the charging and discharging function.
[0034] ■ When the first power input terminal VIN1 is at a low level and the second power input terminal VIN2 is at a high level, it is defined as an abnormal operating state.
[0035] 1. In abnormal operating conditions, the path is from the second power input terminal VIN2, resistor R6, resistor R7 to the first power input terminal VIN1. The voltage is Ur1_r6≈VIN2*(R6 / (R1+R6)). The internal reference voltage of Zener diode U1 is Vref=2.5V. Since Ur1_r6>Vref, the internal voltage of Zener diode U1 is adjusted to approximately 1V for the anode output U1_K. The voltage of U1_K (which is equal to the Zener voltage of Zener diode U1) is also the input voltage of the gate terminal (or gate) of MOSFET Q3.
[0036] 2. The input voltage at the Gate terminal of MOS transistor Q3 is U1_K. The source of MOS transistor Q3 is connected to VIN1 = 0V through resistor R4. Then U1_K < Uq3_th, which causes the channel of MOS transistor Q3 to disconnect. At the same time, the body diode of MOS transistor Q3 is in the reverse state, that is, in the cut-off state. It is deduced that MOS transistor Q3 is operating in the cut-off state (or off state).
[0037] 3. Through the above analysis, after MOS transistor Q3 is cut off, the polarized capacitor C1 is disconnected from the load and will not be damaged by reverse voltage.
[0038] In summary, the functions of resistor R1 and resistor R6 are to divide the voltage of VIN1 / VIN2; the function of resistor R7 is to limit the current of voltage regulator U1; the function of resistor R4 is to limit the current of the body diode of MOS transistor Q3; the function of MOS transistor Q3 is to switch the working state of polarized capacitor C1; the function of the voltage regulator is to compare the voltage reference with the voltage of VIN1 / VIN2.
[0039] In conclusion, the beneficial effects of the non-reverse connection protection circuit for polarized capacitors provided by the present invention are as follows:
[0040] 1) The present invention can ensure that the charging and discharging of the polarized capacitor are not affected during normal operation, and the polarized capacitor will not be broken down during reverse connection.
[0041] 2) The present invention does not require additional power reverse protection and solves the heat problem of power reverse protection at the same time.
[0042] 3) The present invention uses fewer circuit components and the circuit is more concise.
[0043] The non-reverse connection protection circuit for polarized capacitors provided by the present invention can be applied to the protection of polarized capacitors in high-power vehicle-mounted and civilian products. In the case of no other polarized protection circuits, by adopting the non-reverse connection protection circuit for polarized capacitors provided by the present invention, the polarization protection of polarized capacitors (such as electrolytic capacitors) can be achieved, and at the same time, the obvious temperature rise impact on other components of the product will not be caused due to the addition of the polarization protection circuit.
[0044] It should be noted that any modification made by those skilled in the art to the specific implementation manners of the present invention does not depart from the scope of the claims of the present invention. Correspondingly, the scope of the claims of the present invention is not limited solely to the foregoing specific implementation manners.
Claims
1. A reverse-connection protection circuit for polarized capacitors, characterized in that, It includes resistors R1, R4, R6, and R7, a Zener diode U1, a polarized capacitor C1, a MOSFET Q3, a first power input terminal VIN_1, and a second power input terminal VIN_2. One end of resistor R1 is connected to the first power input terminal VIN_1, and the other end is connected to node A; one end of resistor R6 is connected to node A, and the other end is connected to the second power input terminal VIN_2; the positive terminal of Zener diode U1 is connected to the first power input terminal VIN_1, its negative terminal is connected to the second power input terminal VIN_2 via resistor R7, and its control terminal is connected to node A; the first connection terminal of MOSFET Q3 is connected to the first power input terminal VIN_1 via resistor R4, its second connection terminal is connected to the second power input terminal VIN_2, and its control terminal is connected to the negative terminal of Zener diode U1; the positive terminal of polarized capacitor C1 is connected to the first power input terminal VIN_1, and its negative terminal is connected to the first connection terminal of MOSFET Q3.
2. The reverse connection protection circuit for polarized capacitors according to claim 1, characterized in that, When the positive terminal of the power supply is connected to the first power input terminal VIN_1 and the negative terminal of the power supply is connected to the second power input terminal VIN_2, the Zener diode U1 is in the forward conduction state and the MOSFET Q3 is turned on. When the negative terminal of the power supply is connected to the first power input terminal VIN_1 and the positive terminal of the power supply is connected to the second power input terminal VIN_2, the Zener diode U1 is in a voltage-stabilizing state and the MOSFET Q3 is turned off.
3. The reverse connection protection circuit for polarized capacitors according to claim 2, characterized in that, The resistance values of resistors R3 and R10 are selected to satisfy the following condition: when the negative terminal of the power supply is connected to the first power input terminal VIN_1 and the positive terminal of the power supply is connected to the second power input terminal VIN_2, the voltage drop across resistor R6 is greater than the internal reference voltage of the Zener diode U1, so that the Zener diode U1 is in a regulated working state.
4. The reverse connection protection circuit for polarized capacitors according to claim 3, characterized in that, The voltage regulation value of the Zener diode U1 is less than the turn-on voltage value of the MOSFET Q3.
5. The reverse-connection protection circuit for polarized capacitors according to claim 2, characterized in that, The MOS transistor Q3 is an NMOS transistor, and the first connection terminal, the second connection terminal, and the control terminal of the MOS transistor Q3 are the source, drain, and gate of the NMOS transistor, respectively.
6. The reverse-connection protection circuit for polarized capacitors according to any one of claims 1-5, characterized in that, The polarized capacitor C1 is an electrolytic capacitor.