A super capacitor constant current charging circuit based on DC-DC step-down chip

Abstract

The utility model discloses an embodiment relates to a kind of supercapacitor constant current charging circuit based on DC-DC step-down chip, including step-down chip module, current sampling module, operational amplifier module, feedback selection module and prevent back flow module.The current sampling module is connected in series in supercapacitor negative pole to gather current signal, and the anode of common cathode diode is input after being amplified by operational amplifier in phase;Feedback selection module is input step-down chip feedback pin by common cathode diode automatic switching voltage feedback voltage division signal and higher one of amplified current signal, realizes constant current control and overvoltage protection;Prevent back flow module is connected in series in output end to prevent supercapacitor reverse power supply.The circuit is realized low-cost large-current constant current charging by general step-down chip combined with operational amplifier, support 8-36V wide input voltage range, output current is continuously adjustable to 12A, with simple structure, fast response, low ripple characteristics, applicable to supercapacitor fast and efficient charging scene.

Description

Technical Field

[0001] This application relates to the field of electronic technology application technology, and in particular to a supercapacitor constant current charging circuit based on a DC-DC step-down chip. Background Technology

[0002] Supercapacitors, as energy storage devices, are increasingly being applied in various aspects of our lives, particularly in defense and military applications, due to their rapid charging and discharging speeds, high efficiency, and long lifespan. Supercapacitors can store tens of thousands of times more energy than ordinary capacitors while maintaining a relatively small size, and can be fully charged in a short time, which is especially important for systems requiring rapid response. The fast charging capability of supercapacitors allows vehicles to be used more frequently, improving efficiency and convenience.

[0003] Furthermore, the charging and discharging processes of supercapacitors are primarily physical processes, involving no chemical reactions, thus offering high safety and reliability. In data storage applications, supercapacitors are replacing batteries in 3.3V memory backup solid-state drives, battery-powered portable industrial and medical equipment, industrial alarms, and smart power meters. These applications require medium- to high-current / short-duration backup power supplies and battery backups due to the need for sudden power outages. Compared to batteries, supercapacitors offer higher peak power, smaller form factor, longer charge cycle life over a wider operating temperature range, lower equivalent series resistance, and higher power density. Supercapacitor charging features fast charging, high efficiency, and long lifespan, and these characteristics, particularly in electric vehicles and data storage, demonstrate the potential and advantages of supercapacitor technology.

[0004] Constant current charging ensures a stable current during the charging process, preventing damage to the supercapacitor from excessively high or low current. Secondly, constant current charging improves charging efficiency. Because the constant current source continuously provides a stable current, the supercapacitor can be fully charged faster, shortening the charging time. Simultaneously, constant current charging also reduces energy loss during the charging process, further improving charging efficiency. Constant current charging offers numerous benefits to supercapacitors; therefore, it is an excellent choice for charging them.

[0005] However, existing constant current charging circuits only offer a single buck function, leading to instability or malfunction when the input and output voltages are close. Furthermore, most commonly used constant current control chips operate at low current, while large-capacity capacitors like supercapacitors require significantly higher currents to quickly reach the desired voltage. Additionally, dedicated buck DC-DC power management chips are expensive and unsuitable for low-cost requirements. Moreover, the circuits are complex, difficult to debug, and demand a high level of technical expertise from the designers. Utility Model Content

[0006] The purpose of this application is to provide a supercapacitor constant current charging circuit based on a DC-DC step-down chip, which solves the problems of unstable operation when the voltage is close, slow charging speed of small current chips, high cost of dedicated chips, and complex circuit debugging in the prior art.

[0007] To achieve the above objectives, this application provides a supercapacitor constant current charging circuit based on a DC-DC buck chip, comprising:

[0008] The step-down chip module U2 is used to convert the input voltage into an adjustable output voltage;

[0009] The current sampling module R6 is connected in series between the negative terminal of the supercapacitor C20 and ground to collect the charging current signal;

[0010] The operational amplifier module U3A has its non-inverting input terminal connected to the high potential terminal of the current sampling module R6 to form a non-inverting amplifier circuit.

[0011] The feedback selection module D4 uses a common cathode diode. Its first anode is connected to the output terminal of the operational amplifier module U3A, its second anode is connected to the voltage feedback divider network R3 and R4 of the buck chip module U2, and its cathode is connected to the feedback pin FB of the buck chip module U2.

[0012] The anti-backflow module D2 is connected in series between the output terminal of the step-down chip module U2 and the positive terminal of the supercapacitor C20.

[0013] Voltage divider resistor modules R3 and R4 are connected in parallel between the output terminal of step-down chip module U2 and ground to limit the maximum output voltage.

[0014] The operational amplifier module U3A amplifies the current sampling signal and inputs it to the feedback selection module D4. The feedback selection module D4 automatically selects the higher of the voltage feedback signal or the current feedback signal and inputs it to the buck chip module U2 to achieve dual control of constant current charging and overvoltage protection.

[0015] Furthermore, the step-down chip module U2 is an XL4016 DC-DC step-down chip.

[0016] Furthermore, the feedback selection module D4 is a low-dropout Schottky diode with a forward voltage drop of less than 0.3V.

[0017] Furthermore, the voltage division ratio of the voltage divider resistor modules R3 and R4 is adjustable, which is used to set the charging cutoff voltage of the supercapacitor C20.

[0018] Furthermore, the anti-backflow module D2 is a common-cathode Schottky diode, with its cathode connected to the positive terminal of the supercapacitor C20.

[0019] Furthermore, the amplification factor of the operational amplifier module U3A is set to a fixed value by the inverting input resistors R8 and R9.

[0020] Furthermore, the current sampling module R6 is a precision milliohm resistor, the resistance of which is determined according to the target charging current.

[0021] Furthermore, it also includes an output filtering module, which consists of an inductor L3 and parallel capacitors C6 and C9, connected between the switching node of the step-down chip module U2 and the anti-backflow module D2.

[0022] Furthermore, the power supply terminal of the operational amplifier module U3A is provided with a decoupling capacitor C10, which is connected between the 12V power supply and ground.

[0023] Furthermore, a current-limiting resistor R7 is connected in series between the voltage divider resistor modules R3 and R4 and the second anode of the feedback selection module D4 to suppress feedback loop noise.

[0024] As can be seen from the above, the technical solution provided in this application includes a buck chip module, a current sampling module, an operational amplifier module, a feedback selection module, and an anti-backflow module. The current sampling module is connected in series with the negative terminal of the supercapacitor to collect the current signal, which is then amplified in phase by the operational amplifier and input to the anode of the common cathode diode. The feedback selection module automatically switches between the voltage feedback divider signal and the amplified current signal via the common cathode diode, inputting the higher signal to the buck chip feedback pin to achieve constant current control and overvoltage protection. The anti-backflow module is connected in series at the output terminal to prevent reverse power supply to the supercapacitor. This circuit uses a general-purpose buck chip combined with an operational amplifier to achieve low-cost, high-current constant-current charging, supports a wide input voltage range of 8-36V, and has a continuously adjustable output current up to 12A. It features a simple structure, fast response, and low ripple characteristics, making it suitable for fast and efficient supercapacitor charging scenarios. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the architecture of a supercapacitor constant current charging circuit based on a DC-DC step-down chip in an embodiment of this application. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0027] This invention provides a supercapacitor constant current charging circuit based on a DC-DC step-down chip. Please refer to [link / reference]. Figure 1 The step-down chip module U2 is used to convert the input voltage into an adjustable output voltage;

[0028] The current sampling module R6 is connected in series between the negative terminal of the supercapacitor C20 and ground to collect the charging current signal;

[0029] The operational amplifier module U3A has its non-inverting input terminal connected to the high potential terminal of the current sampling module R6 to form a non-inverting amplifier circuit.

[0030] The feedback selection module D4 uses a common cathode diode. Its first anode is connected to the output terminal of the operational amplifier module U3A, its second anode is connected to the voltage feedback divider network R3 and R4 of the buck chip module U2, and its cathode is connected to the feedback pin FB of the buck chip module U2.

[0031] The anti-backflow module D2 is connected in series between the output terminal of the step-down chip module U2 and the positive terminal of the supercapacitor C20.

[0032] Voltage divider resistor modules R3 and R4 are connected in parallel between the output terminal of step-down chip module U2 and ground to limit the maximum output voltage.

[0033] The operational amplifier module U3A amplifies the current sampling signal and inputs it to the feedback selection module D4. The feedback selection module D4 automatically selects the higher of the voltage feedback signal or the current feedback signal and inputs it to the buck chip module U2 to achieve dual control of constant current charging and overvoltage protection.

[0034] Furthermore, the step-down chip module U2 is an XL4016 DC-DC step-down chip. The XL4016 has a high output current, capable of providing up to 12A, maintaining a high current value even during prolonged use. Its input voltage range is 8-36V, adapting to various input voltage conditions. The XL4016 boasts a conversion efficiency of up to 96%, helping to reduce energy loss and heat generation.

[0035] Furthermore, the feedback selection module D4 is a low-dropout Schottky diode with a forward voltage drop of less than 0.3V.

[0036] Furthermore, the voltage division ratio of the voltage divider resistor modules R3 and R4 is adjustable, which is used to set the charging cutoff voltage of the supercapacitor C20.

[0037] Furthermore, the anti-backflow module D2 is a common-cathode Schottky diode, with its cathode connected to the positive terminal of the supercapacitor C20. A pair of common-cathode Schottky diodes with low forward voltage drop are used to connect the voltage and current detection feedback to the two anodes of this diode. Because the internal structure of this device consists of two diodes with their cathodes connected together, the voltage feedback signal and the current feedback signal do not interfere with each other. The feedback pin of the step-down chip uses the signal with the higher voltage.

[0038] Furthermore, the amplification factor of the operational amplifier module U3A is set to a fixed value by the inverting input resistors R8 and R9.

[0039] Furthermore, the current sampling module R6 is a precision milliohm resistor, the resistance of which is determined according to the target charging current.

[0040] Furthermore, it also includes an output filtering module, which consists of an inductor L3 and parallel capacitors C6 and C9, connected between the switching node of the step-down chip module U2 and the anti-backflow module D2.

[0041] Furthermore, the power supply terminal of the operational amplifier module U3A is provided with a decoupling capacitor C10, which is connected between the 12V power supply and ground.

[0042] Furthermore, a current-limiting resistor R7 is connected in series between the voltage divider resistor modules R3 and R4 and the second anode of the feedback selection module D4 to suppress feedback loop noise.

[0043] This application uses a high-efficiency, high-power DC-DC step-down chip in conjunction with an operational amplifier to build a non-inverting amplifier for constant current charging of a supercapacitor. The 12V input voltage is filtered by electrolytic capacitor C7 and then enters pin 5 of the DC-DC step-down chip U2. Ceramic capacitor C8 serves as a bypass capacitor for the internal voltage regulator of step-down chip U2. Pin 3 of step-down chip U2 is the power switch output pin, where the stepped-down voltage is output. This pin connects to the downstream circuit. Energy storage and filtering are achieved through inductor L3 and capacitors C6 and C9. Diode D3, connected in parallel with the GND network, provides freewheeling current to inductor L3 when the internal switch of the step-down chip is closed, ensuring voltage stability in the downstream circuit. Furthermore, voltage feedback is provided to the step-down chip through resistors R3 and R4 via voltage division. A low-dropout common-cathode diode D2 is connected in series in the voltage output circuit to prevent reverse power supply from the supercapacitor to the step-down chip. Finally, the voltage output circuit connects to the positive terminal of the supercapacitor via diode D2. Charging is performed by applying a small voltage to the non-inverting input of operational amplifier U3A through current sampling resistor R6. Utilizing the virtual short and discontinuous characteristics of the operational amplifier, a non-inverting amplifier is constructed. The gain of this operational amplifier is set by two resistors R8 and R9 connected to the inverting input. This circuit's gain is set to 6.2. When the non-inverting input of the operational amplifier is 200mV, the output of the operational amplifier is amplified to 1.2V. The output of the operational amplifier is connected to one anode of a common-cathode diode D4. The other anode of diode D4 is connected to the voltage divider circuit at the output of the buck converter chip. The cathode of diode D4 is connected to the output voltage feedback pin of the buck converter chip U2 to adjust the output voltage of the buck converter chip, thereby charging the supercapacitor.

[0044] refer to Figure 1In the circuit, U2 is the main control chip. Pin 5 of U2 is connected to the positive terminal of capacitor C7. This junction is the positive power input terminal and is marked as junction 12V. The negative terminal of capacitor C7 is connected to the common ground and is marked as junction GND. One end of capacitor C8 is connected to pin 5 of U2, and the other end of C8 is connected to pin 4 of U2. Pin 1 of U2 is connected to GND. Pin 3 of U2, pin 3 of diode D3, and one end of inductor L3 are connected together. Pins 1 and 2 of diode D3 are connected to junction GND, and the other end of inductor L3... One end is marked as node A. The positive terminal of capacitor C6 is connected to node A, and the negative terminal of capacitor C6 is connected to node GND. One end of resistor R3 is connected to node A, and the other end of resistor R3 is connected to one end of resistor R4. The other end of resistor R4 is connected to node GND. The connection point of resistors R3 and R4 is then connected to pin 2 of diode D4. Pins 1 and 2 of diode D2 are connected to node A. Pin 3 of diode D2 is connected to the positive terminal of supercapacitor C20. The negative terminal of supercapacitor C20 is connected to one end of resistors R5 and R6 respectively. The other end of resistor R6 is connected to GND, the other end of resistor R5 is connected to the cathode of diode D5, the cathode of diode D5 is then connected to pin 3 of U3A, the anode of diode D5 is connected to the junction GND, pin 8 of U3A is connected to 12V, pin 4 of U3A is connected to the junction GND, C10 is a decoupling capacitor that powers U3A, one end of capacitor C10 is connected to 12V, the other end of C10 is connected to the junction GND, one end of resistors R8 and R9 is connected to pin 2 of U3A, the other end of resistor R8 is connected to the junction GND, the other end of resistor R9 is connected to pin 1 of U3A, pin 1 of U3A is then connected to pin 1 of D4, one end of resistor R7 is connected to the junction GND, the other end of resistor R7 is connected to pin 3 of diode D4, pin 3 of diode D4 is then connected to pin 2 of U2.

[0045] Output current signal feedback introduces a feedback path into the circuit, creating a negative connection between the output current and the input current, thereby controlling and regulating the current in the circuit. When the output current fluctuates, the feedback loop adjusts the input current to keep the output current stable.

[0046] The initial current signal is amplified to a sufficient amplitude by an operational amplifier, and the amplified current signal is then sent to the control input of the buck converter chip. Based on the magnitude of the input current signal, the buck converter chip adjusts the duty cycle or on-time of its internal switches, thereby changing the output voltage. During the output voltage adjustment process, the buck converter chip continuously monitors the output current magnitude, detecting the output current through a feedback mechanism and feeding this current signal back to the buck converter chip's control circuit. Based on the feedback current signal, the buck converter chip dynamically adjusts its output voltage to ensure that the output current remains constant.

[0047] A resistor divider is used at the output of the buck chip to connect to the output voltage feedback pin of the buck chip. The voltage division ratio is fixed by matching the resistance values ​​of the divider resistors. When the output voltage of the buck chip reaches the maximum voltage value after being amplified by the resistor divider ratio at the feedback pin, the output voltage of the buck chip will stabilize and will not continue to rise.

[0048] The foregoing description of various embodiments of this application is provided to those skilled in the art for illustrative purposes. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, various alternatives and variations of this application will be apparent to those skilled in the art to which the foregoing pertains. Therefore, while some alternative embodiments have been specifically discussed, other embodiments will be obvious or readily apparent to those skilled in the art. This application is intended to include all alternatives, modifications, and variations of the invention already discussed herein, as well as other embodiments falling within the spirit and scope of the foregoing application.

Claims

1. A supercapacitor constant current charging circuit based on a DC-DC step-down chip, characterized in that, include: The step-down chip module (U2) is used to convert the input voltage into an adjustable output voltage; The current sampling module (R6) is connected in series between the negative terminal of the supercapacitor (C20) and ground to collect the charging current signal; The operational amplifier module (U3A) has its non-inverting input connected to the high-potential terminal of the current sampling module (R6) to form a non-inverting amplifier circuit; The feedback selection module (D4) uses a common cathode diode. Its first anode is connected to the output terminal of the operational amplifier module (U3A), its second anode is connected to the voltage divider resistor module (R3, R4) of the buck chip module (U2), and its cathode is connected to the feedback pin (FB) of the buck chip module (U2). The anti-backflow module (D2) is connected in series between the output terminal of the step-down chip module (U2) and the positive terminal of the supercapacitor (C20); The voltage divider resistor modules (R3, R4) are connected in parallel between the output terminal of the step-down chip module (U2) and ground to limit the maximum output voltage; The operational amplifier module (U3A) amplifies the current sampling signal and inputs it to the feedback selection module (D4). The feedback selection module (D4) automatically selects the higher of the voltage feedback signal or the current feedback signal and inputs it to the buck chip module (U2) to achieve dual control of constant current charging and overvoltage protection.

2. The supercapacitor constant current charging circuit based on a DC-DC step-down chip according to claim 1, characterized in that, The step-down chip module (U2) is an XL4016 DC-DC step-down chip.

3. The supercapacitor constant current charging circuit based on a DC-DC step-down chip according to claim 1, characterized in that, The feedback selection module (D4) is a low-dropout Schottky diode with a forward voltage drop of less than 0.3V.

4. The supercapacitor constant current charging circuit based on a DC-DC step-down chip according to claim 1, characterized in that, The voltage division ratio of the voltage divider resistor module (R3, R4) is adjustable and is used to set the charging cut-off voltage of the supercapacitor (C20).

5. A supercapacitor constant current charging circuit based on a DC-DC step-down chip according to claim 1, characterized in that, The backflow prevention module (D2) is a common cathode Schottky diode, whose cathode is connected to the positive terminal of the supercapacitor (C20).

6. The supercapacitor constant current charging circuit based on a DC-DC step-down chip according to claim 1, characterized in that, The amplification factor of the operational amplifier module (U3A) is set to a fixed value by the inverting input resistors (R8, R9).

7. The supercapacitor constant current charging circuit based on a DC-DC step-down chip according to claim 1, characterized in that, The current sampling module (R6) is a precision milliohm resistor, and its resistance value is based on the target charging current.

8. The supercapacitor constant current charging circuit based on a DC-DC step-down chip according to claim 1, characterized in that, It also includes an output filtering module, which consists of an inductor (L3) and a parallel capacitor bank (C6, C9), connected between the switching node of the step-down chip module (U2) and the anti-backflow module (D2).

9. A supercapacitor constant current charging circuit based on a DC-DC step-down chip according to claim 1, characterized in that, The operational amplifier module (U3A) has a decoupling capacitor (C10) at its power supply terminal, which is connected between the power supply (12V) and ground.

10. A supercapacitor constant current charging circuit based on a DC-DC step-down chip according to claim 1, characterized in that, A current-limiting resistor (R7) is connected in series between the voltage divider resistor module (R3, R4) and the second anode of the feedback selection module (D4) to suppress feedback loop noise.

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