Charger output end battery reverse connection protection circuit and control method thereof

Abstract

The invention relates to the field of battery charging, and discloses a charger output end battery reverse connection protection circuit and a control method thereof.The charger output end battery reverse connection protection circuit comprises a battery charger circuit, a mains supply sampling circuit, a power input and conversion circuit, a mains supply detection circuit and an MCU control circuit, and the MCU control circuit comprises a main control chip U3 and a signal input module; the battery charger circuit, the commercial power sampling circuit, the power input and conversion circuit and the commercial power detection circuit are electrically connected with pins of the main control chip U3, and the signal input module comprises a Line-F interface, a pull-up resistor R52 and a filter capacitor C42. Through mutual cooperation of the battery charger circuit, the commercial power sampling circuit, the power input and conversion circuit, the commercial power detection circuit and the MCU control circuit, the battery charger has the advantages of safety, reliability, strong anti-interference capability, accurate voltage monitoring, intelligent control and the like, high-efficiency and stable operation of the charger is ensured, and a battery and related equipment are protected.

Description

Technical Field

[0001] The present invention relates to the technical field of battery charging, and in particular to a battery reverse connection protection circuit at a charger output end and a control method thereof. Background Art

[0002] Some current chargers are online. When replacing the battery, the mains power is not disconnected, and the charging voltage may still be in the output state. At this time, if the battery is replaced with the polarity reversed, the battery will flow back into the charging circuit, causing the entire circuit to be short-circuited. The short-circuit current can cause the components in the circuit to burn out, resulting in unnecessary losses.

[0003] During charger operation, users can mistakenly replace a battery with the wrong polarity, shorting the entire charging circuit. This short-circuit current can damage components within the circuit, resulting in unnecessary losses. Therefore, a reverse-connection battery protection circuit and control method for the charger output are needed. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a battery reverse polarity protection circuit for the charger output end and a control method thereof, which solves the problem that during the operation of the charger, the user mistakenly replaces the polarity of the replacement battery, causing the entire charging circuit to be in a short-circuited state. The short-circuit current may cause the components in the charging circuit to burn out, thereby causing unnecessary losses.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a charger output terminal battery reverse connection protection circuit and a control method thereof, including a battery charger circuit, a mains sampling circuit, a power input and conversion circuit, a mains detection circuit, and an MCU control circuit. The MCU control circuit includes a main control chip U3 and a signal input module. The battery charger circuit, the mains sampling circuit, the power input and conversion circuit, and the mains detection circuit are all electrically connected to the various pins of the main control chip U3. The signal input module includes a Line-F interface, a pull-up resistor R52, and a filter capacitor C42.

[0006] By adopting the above technical solution, each circuit works together to monitor the mains power status in real time. After mains power sampling and detection circuit processing, the signal is transmitted to the main control chip U3 of the MCU control circuit. The main control chip U3 controls the on and off of the battery charger circuit based on the signal. The power input and conversion circuit ensures the safety and stability of the input power. It can also quickly cut off the charging circuit when the battery is reversed to prevent damage to circuit components and abnormal discharge of the battery. It also has overcurrent and overvoltage protection, anti-interference and other functions to improve the safety, stability and reliability of the charger.

[0007] Preferably, the battery charger circuit includes a charger rectifier output part A, a charger output switch control part B, an output port and a battery part C. The charger rectifier output part A includes a transformer T1, diodes D1 and D2, filter capacitors EC1, EC2 and EC3, capacitor C2, inductor L1 and resistors R4 and R5. The diodes D1 and D2 are co-packaged and each includes two diodes to form a bridge rectifier structure. The diodes D1 and D2 are respectively connected to the two side windings of the secondary of the transformer T1, and then filtered by capacitors EC2 and EC3. The inductor L1 and filter capacitor EC1 form a π-shaped filter circuit.

[0008] Preferably, the charger output switch control part B includes N-channel switching MOSFET transistors Q1 and Q2, bipolar transistors Q3 and Q4, an optocoupler U1, a capacitor C3, a diode D3, resistors R1, R3, R7, R9, R10, R13, R14, R17, and a ferrite core inductor LF1, which are used to control the on and off of the charger output and adjust the output voltage. The bipolar transistor Q3 is a PNP transistor and Q4 is an NPN transistor.

[0009] Preferably, the output port and battery part C includes a fuse F1, two connectors CON1, and a battery BT2. The fuse F1 is connected in series in the circuit for overcurrent protection. The two connectors CON1 are both used to connect to the battery BT2 to jointly provide a connection port for the battery charging circuit.

[0010] Preferably, the AC power sampling circuit includes a dual-channel symmetrical voltage divider network, a high-voltage protection circuit, and a star-topology filtering and amplifying module. The dual-channel symmetrical voltage divider network includes a first voltage divider path composed of multiple series resistors R4, R254, R147, R148, R149, and R151, whose input end is connected to the AC power Vin_NN, and a first voltage divider path composed of multiple series resistors R256, R255, R156, R157, R158, and R159, whose input end is connected to the AC power Vin_LL. The star-topology filtering and amplifying module includes an operational amplifier U8, which is the central node.

[0011] Preferably, the power input and conversion circuit includes an overcurrent protection module, an overvoltage protection module, a common mode suppression module, a switch control module, a transformer and rectifier module, and an output filter module.

[0012] Preferably, the over-current protection module is composed of a fuse in series with the input Vin_LL and a fuse in series with the input Vin_NN, for cutting off the circuit when the current is abnormal, the over-voltage protection module includes a MOV in parallel in the circuit, for discharging the current when the mains voltage is too high, the common-mode rejection module includes a common-mode inductor T4 and a capacitor, for rejecting common-mode interference and purifying the input power supply, the switch control module includes a relay K2 and a transistor Q13, for switching on and off the circuit and controlling the energy, the transformer rectifier module is composed of a transformer T9 and a rectifier bridge BD2, for voltage conversion and AC to DC conversion, and the output filter module includes a capacitor and a resistor, for filtering and smoothing the rectified DC voltage, and reducing the voltage ripple.

[0013] Preferably, the mains detection circuit includes a first operational amplifier U8D, a second operational amplifier U7D, a comparator U2, filter capacitors C54, C43, C53, C38, C8, C10, and C39.

[0014] Preferably, the inverting terminal of the comparator U2 is connected to the processed signal, the non-inverting terminal is connected to a reference circuit composed of a resistor R7, a resistor R9, and a filter capacitor C8, and the output terminal outputs a high or low level signal to indicate whether the mains voltage exceeds the threshold value, and the resistor R9 and the filter capacitor C8 form an RC filter circuit.

[0015] Preferably, a control method for a battery reverse connection protection circuit at the output end of a charger includes the following steps: first, a differential sampling of the mains signal is performed by a differential amplifier circuit composed of operational amplifiers U8D and U7D in the mains sampling circuit, common-mode noise is eliminated by the common-mode rejection ratio of the circuit, and the differential-mode effective signal is retained, so that the voltage polarity signal and the current flow direction signal at the output end of the battery are sampled in real time by the main control chip U3, and the electrical state parameters of the connected battery are obtained; The sampled mains signal is transmitted to the main control chip U3 after rectification and filtering by the mains detection circuit, and the voltage / current signal sampled at the battery end is logically compared, so that the main control chip U3 determines whether the battery is reversely connected based on the preset voltage polarity threshold value, such as positive voltage for positive polarity and negative voltage for negative polarity, and the current flow direction characteristic, i.e., the current flows from the charger to the battery during normal charging and reversely during reverse connection. If the battery is reversely connected, the voltage polarity is reversed or the current is reversely abnormal, the main control chip U3 outputs a low level or control signal, and the MOSFET transistors Q1 and Q2 are driven by the bipolar transistors Q3 and Q4 to cut off the current path of the charging circuit. The main control chip U3 in the MCU control circuit continuously monitors the voltage / current signal at the battery end through the pin to maintain the disconnected state of the charging circuit. When the battery polarity is restored to normal connection, the voltage polarity is positive and the current flow is normal, the main control chip U3 outputs an enable signal to re-connect the charging circuit, thereby realizing dynamic protection and recovery control during the charging process of the charger.

[0016] Working principle: Through the charger rectifier output part A, when the charger is plugged into the normal mains, the charger main circuit part A will start working, the transformer converts the high voltage alternating pulse into a low voltage alternating pulse, which is full-wave rectified by D1, D2, filtered by EC2, EC3 capacitors, and then formed into a π-shaped filter by L1, EC1 to obtain the charging voltage V28. Through the charger output switch control part B, when the central processing unit MCU detects that a normal battery is connected, the charger will first turn on the charging voltage, then turn on the output switch, and apply the charging voltage to the battery, and perform a charging action with controlled current and voltage. The specific action is that the OUT end of the MCU control chip U3 sends a HI signal, which is limited by R14 and acts on the Q4-B pole. Q14 is saturated and turned on, and the voltage 1 2.6V passes through Q3E-B and R13, then through Q4C-E and back to GND. This creates a negative voltage at Q3B-E, turning Q3 on. A voltage of 12.6V passes through Q3E-C and reaches the output switch MOSFETQ1 / Q2-G. Since Q1 and Q2 are N-channel MOSFETs, they immediately turn on when the 12.6V voltage is applied to the Q1 and Q2G terminals. The charging voltage V28 passes through the positive and negative terminals of the battery, then through the output switches Q1 and Q2, the current sensing battery R5, and back to the charging voltage loop GND, forming the entire charging circuit. The HI signal sent by the MCU control chip OUT is the "enable signal" for turning on the charging circuit. By driving the BJT, it indirectly controls the on and off of the MOSFET and relay, achieving circuit connection during normal charging and circuit disconnection during reverse connection. When the battery is connected in a forward direction, since D3-A is connected to the battery's negative terminal and the charging voltage GND, no forward voltage flows into the optocoupler U1. The diode between U11-2 is in the off state, and U1's output terminals 3-4 have no current flowing, remaining in the open state. The switching states of Q1 and Q2 are determined by the output signal at the OUT terminal of the MCU control chip. When the battery is connected in a reverse direction, the charger output port voltage is high at the negative terminal and low at the positive terminal. Since D3-A is connected to the battery's negative terminal and the charging voltage GND, the battery voltage flows through D3-A, R7, U1-1, and then back to the battery's negative terminal through U1-2, causing U1 to turn on. Current flows through U1's output terminals 3-4, which are in the on state. At this time, the voltage difference between Q3's EB is close to 0V because U1 is fully conductive. Q3 (PNP) BE has no negative voltage and is turned off. Q3's C terminal has no voltage output. Q1 and Q2 (NMOSFET) are turned off due to the lack of positive turn-on voltage. DS is open, disconnecting the charging circuit. Regardless of whether Q1Q2 is in the on or off state, this protection device will immediately shut down or not turn on as long as the battery is reversed, thereby protecting the charging circuit from damage caused by reverse battery connection. By utilizing the unidirectional conduction characteristics of the diode and the isolation of the optocoupler, the signal generated when the external battery is reversed is applied to the output switch. Regardless of whether the output switch is turned on before the reverse connection, it can be instantly shut down when the reverse connection occurs, thus ensuring that the charging circuit is protected from damage caused by reverse connection at all times.

[0017] The present invention provides a charger output terminal battery reverse connection protection circuit and control method thereof. It has the following beneficial effects: 1. In the present invention, through the mutual cooperation of the battery charger circuit, the mains sampling circuit, the power input and conversion circuit, the mains detection circuit, and the MCU control circuit, the battery charger system has the advantages of safety and reliability, strong anti-interference ability, accurate voltage monitoring, and intelligent control, ensuring the efficient and stable operation of the charger and protecting the battery and related equipment.

[0018] 2. In the present invention, whether the battery is connected first and then the mains, or the mains is connected first and then the battery, or the battery is replaced during charging, if the battery is connected incorrectly, the device of the present invention can protect the charging equipment and the battery without causing any damage.

[0019] 3. In this invention, the mains detection circuit eliminates common-mode noise through an operational amplifier, retaining the effective components of the mains power. A comparator is used to determine the voltage threshold, accurately monitoring the mains voltage status and providing accurate mains power information to the system. If the mains power is abnormal, timely feedback can be provided to trigger corresponding protection or control mechanisms.

[0020] 4. In the present invention, through the reasonable design of the signal input module of the MCU control circuit, the external signal can be input into the MCU control circuit stably and reliably, laying the foundation for the main control chip U3 in the MCU control circuit to accurately analyze and process the signal and make correct decisions, thereby ensuring that the entire charger system operates according to the predetermined logic. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a circuit diagram of a battery charger of the present invention; Figure 2 This is the mains power sampling circuit diagram of the present invention; Figure 3 This is the power input and conversion circuit diagram of the present invention; Figure 4 This is the mains power detection circuit diagram of the present invention; Figure 5 This is the MCU control circuit diagram of the present invention. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0023] Please see the attached Figure 1 -Attached Figure 5 An embodiment of the present invention provides a battery reverse polarity protection circuit for a charger output terminal and a control method thereof, comprising a battery charger circuit, a mains sampling circuit, a power input and conversion circuit, a mains detection circuit, and an MCU control circuit. The MCU control circuit comprises a main control chip U3 and a signal input module. The battery charger circuit, the mains sampling circuit, the power input and conversion circuit, and the mains detection circuit are all electrically connected to respective pins of the main control chip U3. The signal input module comprises a Line-F interface, a pull-up resistor R52, and a filter capacitor C42. Specifically, the mains input status can be monitored in real time through the mains sampling circuit and the mains detection circuit, and the voltage, frequency and other signals can be transmitted to the main control chip U3 in the MCU control circuit. When the battery is connected in the positive direction, the main control chip U3 can drive the switch MOSFET transistors Q1 and Q2 to be forward-conducted, and charging is carried out normally. If the battery is reversely connected when the mains is abnormal, the main control chip U3 can make a comprehensive judgment to avoid danger. For example, if the mains is over-voltage and the battery is reversely connected, the main chip can quickly cut off the charger circuit. After the mains is converted to a suitable voltage through the power input and conversion circuit, the conversion is monitored by the main chip U3. In the rear power state, if the battery is reversed, the power conversion output can be stopped. The Line-F interface is used as the signal input terminal to introduce external signals. Then the resistor R52 acts as a pull-up resistor to pull the level of the Line-F interface to +3.3V. When the external signal is not connected or the signal is low, the LINE-F node is kept in a high level state. At the same time, it can also limit the current and protect the circuit. The filter capacitor C42 is connected to the ground to filter out the high-frequency noise in the signal introduced by the Line-F interface, smooth the signal waveform, and make the signal input to the subsequent circuit purer and more stable.

[0024] Please see the attached Figure 1 -Attached Figure 5 The battery charger circuit includes a charger rectifier output part A, a charger output switch control part B, an output port and a battery part C. The charger rectifier output part A includes a transformer T1, diodes D1 and D2, filter capacitors EC1, EC2 and EC3, capacitor C2, inductor L1, and resistors R4 and R5. Diodes D1 and D2 are co-packaged and each contains two diodes to form a bridge rectifier structure. Diodes D1 and D2 are respectively connected to the two side windings of the secondary of transformer T1, and then filtered by capacitors EC2 and EC3. Inductor L1 and filter capacitor EC1 form a π-shaped filter circuit. Specifically, transformer T1 converts the input mains voltage into an AC voltage suitable for subsequent rectification and charging according to a certain transformation ratio to achieve voltage adaptation. The bridge rectifier structure composed of diodes D1 and D2 can convert the AC power output from the secondary side of transformer T1 into unidirectional pulsating DC power. Utilizing the unidirectional conductivity of the diode, the current can flow through the load in the same direction regardless of the positive half-cycle or negative half-cycle of the AC power. The rectified unidirectional pulsating DC power is first preliminarily filtered by filter capacitors EC2 and EC3 to reduce ripple. Then, the AC component is further filtered out by a π-shaped filter circuit composed of inductor L1 and filter capacitor EC1, outputting smoother DC power to provide a stable power supply for subsequent charging.

[0025] Please see the attached Figure 1 -Attached Figure 5The charger output switch control part B includes N-channel switch MOSFET transistors Q1 and Q2, bipolar transistors Q3 and Q4, an optical coupler U1, a capacitor C3, diodes D3, resistors R1, R3, R7, R9, R10, R13, R14, R17, and a ferrite core inductor LF1, which are used to control the on-off of the charger output and adjust the output voltage; the bipolar transistor Q3 is a PNP transistor, and the bipolar transistor Q4 is an NPN transistor; Specifically, the on-off of the current path between the charger and the battery can be accurately controlled according to the circuit instruction of the main control chip U3 through the switching elements of the switch MOSFET transistors Q1 and Q2 and the bipolar transistors Q3 and Q4, so that the circuit is quickly cut off when the battery is fully charged or reversely connected, thereby preventing damage, and the output voltage and current can be dynamically adjusted according to the battery state to realize the switching of different charging modes such as constant-current charging and constant-voltage charging.

[0026] Please refer to the attached Figure 1 -attached Figure 5 The output port and battery part C includes a fuse F1 and two connectors CON1, and the fuse F1 is connected in series in the circuit for overcurrent protection, and the two connectors CON1 are both used to connect the battery BT2 to provide connection ports for the charging circuit of the battery. Specifically, the output port and battery part C can provide a physical interface connected with the battery, ensure the correct connection between the charger and the battery, thereby forming a charging circuit, and the fuse F1 can be quickly fused to cut off the circuit when the current is too large (such as short circuit), thereby protecting the battery and the charger from overcurrent damage, and the circuit can cooperate with the MCU control circuit to monitor the battery state to prevent overcharging and overdischarging of the battery, and the two ports of the two connectors CON1 are used to connect the positive and negative electrodes of the battery BT2 to provide an electrical connection path for the battery charging.

[0027] Please refer to the attached Figure 1 -attached Figure 5 The mains sampling circuit includes a double-channel symmetric voltage division network, a high-voltage protection circuit, and a star topology filter amplification module; the double-channel symmetric voltage division network includes a first voltage division path composed of a plurality of series resistors R4, R254, R147, R148, R149, and R151, and a first voltage division path composed of a plurality of series resistors R256, R255, R156, R157, R158, and R159, and the input end of the double-channel symmetric voltage division network is connected with the mains Vin_NN and Vin_LL; and the star topology filter amplification module includes an operational amplifier U8 as a center node. Specifically, due to the existence of the phase line and the phase line (such as Vin_LL), the phase line and the neutral line (such as Vin_NN) voltage, by adopting a double-channel symmetrical voltage division network to sample it respectively, the voltage information of the power supply can be fully obtained. The high voltage signal of the power supply Vin_NN and Vin_LL is first divided by a front-end resistor string, reduced by a certain proportion, converted into a low voltage signal suitable for subsequent circuit processing, and then processed by a star topology filter amplification module to output a clean and appropriate amplitude signal for the main control chip U3 in the MCU control circuit for voltage monitoring, overvoltage / undervoltage protection, etc. At the same time, the double channels respectively sample different power supply voltages, which is convenient for obtaining more comprehensive power supply information to provide accurate voltage data for the system, realize overvoltage and undervoltage judgment functions, and prevent the damage of the rear-end circuit caused by surge, peak and other overvoltage impacts in the power supply through the high-voltage protection circuit. When the power supply voltage abnormally rises, the high-voltage protection circuit can protect the entire power supply sampling circuit and other connected circuits. The star topology filter amplification module is a star topology structure centered on operational amplifier U8, which combines RC filter circuit, voltage dividing resistor and feedback network to realize the filtering, amplification and anti-interference conditioning of the power supply signal, improve the signal quality and amplitude, and facilitate accurate analysis and processing by the main control chip, which is the core signal processing unit of the power supply sampling circuit. The star topology filter amplification module can filter and remove high-frequency noise and interference signals in the power supply signal, making the sampling signal more pure. Amplification is to amplify the weak power supply signal after voltage division to an appropriate amplitude to facilitate accurate processing and analysis of the subsequent circuit.

[0028] Please refer to the attached Figure 1 -attached Figure 5 The power input and conversion circuit includes an overcurrent protection module, an overvoltage protection module, a common mode suppression module, a switch control module, a voltage conversion and rectification module, and an output filter module. Specifically, when overcurrent occurs in the circuit, the overcurrent protection module can quickly act to cut off the circuit or limit the current size. The overvoltage protection module can monitor the input voltage value to prevent overvoltage damage to the rear-end circuit. The common mode suppression module can reduce common mode interference to reduce the probability of circuit malfunction and improve the stability and reliability of the entire power input and conversion circuit. The switch control module can accurately control the on-off between the power input and the subsequent circuit according to the working requirements of the circuit. The voltage conversion and rectification module can convert the input power voltage to an appropriate value according to the actual requirements of the circuit. The rectifier bridge BD2 converts the alternating current output by the transformer into direct current. Since the rectified direct current voltage usually contains a certain ripple (alternating component), the output filter module can filter the rectified direct current voltage to smooth the voltage waveform and make the output direct current voltage more stable and pure.

[0029] Please see the attached Figure 1 -Attached Figure 5 The overcurrent protection module consists of a fuse connected in series to the mains input terminal Vin_LL and a fuse connected in series to the mains input terminal Vin_NN, which are used to cut off the circuit when the current is abnormal. The overvoltage protection module includes a varistor MOV connected in parallel in the circuit, which is used to discharge the current when the mains is overvoltage. The common-mode suppression module includes a common-mode inductor T4 and a capacitor, which are used to suppress common-mode interference and purify the input power. The switch control module includes a relay K2 and a transistor Q13, which are used for circuit on-off and energy control. The transformer rectifier module consists of a transformer T9 and a rectifier bridge BD2, which are used for voltage conversion and AC to DC conversion. The output filter module includes a capacitor and a resistor, which are used to filter and smooth the rectified DC voltage and reduce voltage ripple. Specifically, by connecting two fuses in series at the mains input terminal Vin_LLh and the mains input terminal Vin_NN respectively, double protection can be formed, thereby ensuring that the circuit can be cut off when any line is overcurrent. When the circuit is overloaded or short-circuited, the fuse melts due to excessive current, cutting off the circuit to prevent subsequent components (such as transformers and rectifier bridges) from being damaged due to overcurrent. Through the parallel varistor MOV, when the mains voltage exceeds the breakdown voltage of the varistor, the resistance of the varistor MOV drops sharply, discharging the overvoltage energy to the ground, thereby protecting the back-end circuit. The common-mode inductor T4 can suppress common-mode interference (such as lightning, EMI radiation), and the common-mode signal is presented through the principle of reverse magnetic flux cancellation. High impedance, and then the differential mode and common mode noise are further filtered out through the capacitor to purify the power supply. In the switch control module, the relay K2 controls the contact opening and closing through the coil to realize the on and off of the main circuit (such as mains connection / disconnection), which is suitable for high voltage and high current scenarios. Then, the relay coil current is driven by the transistor Q13 to realize the switch control of electrical isolation. The high voltage AC power can be converted into low voltage AC power through the transformer T9 to realize voltage conversion and electrical isolation. The AC power output by the transformer T9 can be converted into pulsating DC power through the rectifier bridge BD2 to provide input for subsequent filtering. The mains power can be converted into a suitable DC voltage through the transformer and rectifier module to meet the needs of battery charging, etc.

[0030] Please see the attached Figure 1 -Attached Figure 5 , the mains detection circuit includes a first operational amplifier U8D, a second operational amplifier U7D, a comparator U2, and filter capacitors C54, C43, C53, C38, C8, C10, and C39; Specifically, the differential amplifier circuit composed of the first operational amplifier U8D and the second operational amplifier U7D can eliminate the common-mode noise in the sampling signal and retain the effective component of the AC power. By converting the analog AC power signal into a digital logic signal, the main control chip U3 in the MCU control circuit can respond quickly. Multiple filter capacitors can filter out high-frequency noise, ensure the stability of the sampling signal, and avoid malfunction of the comparator.

[0031] Please see the attached Figure 1 -Attached Figure 5 The inverting terminal of the comparator U2 is connected to the processed signal, and the non-inverting terminal is connected to the reference circuit composed of resistor R7, resistor R9, and filter capacitor C8. The output terminal indicates whether the mains voltage exceeds the threshold through high and low levels. The resistor R9 and filter capacitor C8 form an RC filter circuit; Specifically, the RC filter circuit composed of resistor R9 and filter capacitor C8 can smooth the reference voltage to prevent false triggering caused by interference. The threshold monitoring of the mains voltage is achieved through the comparator and the reference voltage. The anti-interference ability is enhanced in conjunction with the filter network. It is the core component of the power protection circuit. Its output signal directly triggers the protection logic of the main control chip U3 in the MCU control circuit, thereby ensuring that the charger works safely under abnormal mains conditions.

[0032] Please see the attached Figure 1 -Attached Figure 5 A control method for a reverse-connection battery protection circuit at a charger output terminal includes the following steps: first, differentially sampling a mains signal using a differential amplifier circuit comprised of operational amplifiers U8D and U7D in a mains sampling circuit, eliminating common-mode noise using the circuit's common-mode rejection ratio characteristics while retaining differential-mode valid signals. This allows a main control chip U3 to sample the voltage polarity signal and current direction signal at the battery output terminal in real time through a pin to obtain electrical status parameters of the battery connection; The mains power detection circuit transmits the sampled mains power signal to the main control chip U3 after rectification and filtering, and performs a logical comparison with the voltage / current signal sampled at the battery end. This allows the main control chip U3 to determine whether the battery is reversely connected based on the preset voltage polarity threshold, such as positive forward voltage and negative reverse voltage, and the current flow characteristics. During normal charging, the current flows from the charger to the battery, and in the opposite direction during reverse connection. If reverse connection of the battery, reverse voltage polarity or abnormal reverse current is detected, the main control chip U3 outputs a low level or control signal to drive the switching MOSFET transistors Q1 and Q2 through the bipolar transistors Q3 and Q4 to cut off the current path of the charging circuit; The main control chip U3 in the MCU control circuit continuously monitors the voltage / current signal at the battery end through the pin to maintain the disconnected state of the charging circuit. When the battery polarity is restored to normal connection, the voltage polarity is positive and the current flow is normal, the main control chip U3 outputs an enable signal to re-open the charging circuit, thereby realizing dynamic protection and recovery control during the charging process of the charger; Specifically, the AC power sampling circuit and the main control chip U3 in the MCU control circuit jointly monitor the AC power and battery status, and then the differential amplifier circuit composed of the first operational amplifier U8D and the second operational amplifier U7D is used to eliminate common-mode noise to obtain accurate signals. The main control chip U3 is then used to analyze and determine whether the battery is reversely connected. Once reverse connection is detected, the main control chip U3 immediately outputs a control signal to drive the N-channel MOSFET transistors Q1 and Q2, bipolar transistors Q3 and Q4, and relay K2 to cut off the charging circuit. In conjunction with the overcurrent and overvoltage protection of the power input and conversion circuit, double protection is achieved. It can not only quickly block the reverse current to avoid damage to the battery and circuit components, but also resist abnormal interference from the AC power, thereby effectively improving the safety and reliability of the charger during operation, and preventing the user from misoperating the battery and replacing it with the wrong polarity, causing the entire charging circuit to be short-circuited. The short-circuit current will cause the components in the charging circuit to burn, thereby causing unnecessary losses.

[0033] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A battery reverse connection protection circuit for a charger output terminal, comprising a battery charger circuit, a mains sampling circuit, a power input and conversion circuit, a mains detection circuit, and an MCU control circuit, characterized in that: The MCU control circuit includes a main control chip U3 and a signal input module. The battery charger circuit, mains sampling circuit, power input and conversion circuit, and mains detection circuit are all electrically connected to the various pins of the main control chip U3. The signal input module includes a Line-F interface, a pull-up resistor R52, and a filter capacitor C42.

2. A charger output terminal battery reverse connection protection circuit according to claim 1, characterized in that: The battery charger circuit includes a charger rectifier output section A, a charger output switch control section B, an output port, and a battery section C. The charger rectifier output section A includes a transformer T1, diodes D1 and D2, filter capacitors EC1, EC2, and EC3, capacitor C2, inductor L1, and resistors R4 and R5. The diodes D1 and D2 are co-packaged and each comprises two diodes, forming a bridge rectifier structure. The diodes D1 and D2 are respectively connected to the two side windings of the secondary of transformer T1, and then filtered by capacitors EC2 and EC3. The inductor L1 and filter capacitor EC1 form a π-shaped filter circuit.

3. A charger output terminal battery reverse connection protection circuit according to claim 1, characterized in that: The charger output switch control part B includes N-channel switching MOSFET transistors Q1 and Q2, bipolar transistors Q3 and Q4, optocoupler U1, capacitor C3, diode D3, resistors R1, R3, R7, R9, R10, R13, R14, R17, and ferrite core inductor LF1, which are used to control the on and off of the charger output and adjust the output voltage. The bipolar transistor Q3 is a PNP transistor and Q4 is an NPN transistor.

4. A charger output terminal battery reverse connection protection circuit according to claim 1, characterized in that: The output port and battery part C includes a fuse F1, two connectors CON1, and a battery BT2. The fuse F1 is connected in series in the circuit for overcurrent protection. The two connectors CON1 are both used to connect to the battery BT2 to jointly provide a connection port for the battery charging circuit.

5. A charger output terminal battery reverse connection protection circuit according to claim 1, characterized in that: The mains sampling circuit includes a dual-channel symmetrical voltage divider network, a high-voltage protection circuit, and a star-topology filtering and amplifying module. The dual-channel symmetrical voltage divider network includes a first voltage divider path composed of multiple series resistors R4, R254, R147, R148, R149, and R151, whose input end is connected to the mains Vin_NN, and a first voltage divider path composed of multiple series resistors R256, R255, R156, R157, R158, and R159, whose input end is connected to the mains Vin_LL. The star-topology filtering and amplifying module includes an operational amplifier U8, which is the central node.

6. A charger output terminal battery reverse connection protection circuit according to claim 1, characterized in that: The power input and conversion circuit includes an overcurrent protection module, an overvoltage protection module, a common mode suppression module, a switch control module, a transformer and rectifier module, and an output filter module.

7. A charger output terminal battery reverse connection protection circuit according to claim 6, characterized in that: The overcurrent protection module is composed of a fuse connected in series to the mains input terminal Vin_LL and a fuse connected in series to the mains input terminal Vin_NN, which is used to cut off the circuit when the current is abnormal. The overvoltage protection module includes a varistor MOV connected in parallel in the circuit, which is used to discharge current when the mains is overvoltage. The common-mode suppression module includes a common-mode inductor T4 and a capacitor, which is used to suppress common-mode interference and purify the input power supply. The switch control module includes a relay K2 and a transistor Q13, which are used for circuit on-off and energy control. The transformer and rectifier module is composed of a transformer T9 and a rectifier bridge BD2, which is used for voltage conversion and AC to DC conversion. The output filter module includes a capacitor and a resistor, which is used to filter and smooth the rectified DC voltage and reduce voltage ripple.

8. The charger output terminal battery reverse connection protection circuit according to claim 1, characterized in that: The mains power detection circuit includes a first operational amplifier U8D, a second operational amplifier U7D, a comparator U2, and filter capacitors C54, C43, C53, C38, C8, C10, and C39.

9. A charger output terminal battery reverse connection protection circuit according to claim 8, characterized in that: The inverting terminal of the comparator U2 is connected to the processed signal, and the non-inverting terminal is connected to a reference circuit composed of resistors R7, R9, and filter capacitor C8. The output terminal indicates whether the mains voltage exceeds the threshold through high and low levels. The resistor R9 and filter capacitor C8 form an RC filter circuit.

10. A control method for a battery reverse connection protection circuit at a charger output end, characterized in that: A charger output terminal battery reverse connection protection circuit according to claim 8, the method comprising the following steps: first, differentially sampling the mains signal through a differential amplifier circuit composed of operational amplifiers U8D and U7D in the mains sampling circuit, eliminating common-mode noise by utilizing the common-mode rejection ratio characteristic of the circuit, retaining the differential-mode effective signal, so that the main control chip U3 samples the voltage polarity signal and current flow direction signal of the battery output terminal in real time through the pin to obtain the electrical state parameters of the battery connection; The mains power detection circuit transmits the sampled mains power signal to the main control chip U3 after rectification and filtering, and performs a logical comparison with the voltage / current signal sampled at the battery end. This allows the main control chip U3 to determine whether the battery is reversely connected based on the preset voltage polarity threshold, such as positive forward voltage and negative reverse voltage, and the current flow characteristics. During normal charging, the current flows from the charger to the battery, and in the opposite direction during reverse connection. If reverse connection of the battery, reverse voltage polarity or abnormal reverse current is detected, the main control chip U3 outputs a low level or control signal to drive the switching MOSFET transistors Q1 and Q2 through the bipolar transistors Q3 and Q4 to cut off the current path of the charging circuit; The main control chip U3 in the MCU control circuit continuously monitors the voltage / current signal at the battery end through the pin to maintain the disconnected state of the charging circuit. When the battery polarity is restored to normal connection, the voltage polarity is positive and the current flow is normal, the main control chip U3 outputs an enable signal to re-connect the charging circuit, thereby realizing dynamic protection and recovery control during the charging process of the charger.

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