A supercapacitor charging and discharging system and method

Abstract

The present invention relates to the technical field of capacitor charging and discharging, and in particular to a supercapacitor charging and discharging system and method. The charging and discharging system includes a power supply, an MCU, a charging capacitor, a charging circuit, a discharging circuit, and a load connected to the discharging circuit. The charging power supply voltage, the charging voltage and the charging current of the charging capacitor can be detected in real time, and the charging current is controlled in a PID manner through a PWM interface of the MCU. By setting a charging power supply voltage threshold and a charging voltage threshold, different charging modes such as a trickle charging mode, a constant current charging mode, a voltage-equalizing charging mode, and a constant voltage charging mode are switched. The size of the charging current is controlled according to different charging modes. When the load is connected for discharging, a MOS tube is set to be turned on to avoid heating problems caused by a diode voltage drop, thereby ensuring the safety and stability of the charging and discharging process.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmentally friendly power supply charging and discharging management, in particular to the technical field of capacitor charging and discharging, and more particularly to a supercapacitor charging and discharging system and method. Background Art

[0002] Compared with batteries and traditional physical capacitors, supercapacitors have the advantages of high power density, which can reach 102-104kW / kg, which is much higher than the power density level of batteries; long cycle life, after 500,000 to 1 million times of high-speed deep charge and discharge cycles in a few seconds, the characteristics of supercapacitors change very little, and the capacity and internal resistance only decrease by 10% to 20%; wide operating temperature range, because the adsorption and desorption rate of ions in supercapacitors does not change much at low temperatures, so its capacity changes much less than batteries, and the operating temperature range of commercial supercapacitors can reach -40℃~+80℃; maintenance-free, supercapacitors have high charging and discharging efficiency, have a certain tolerance to overcharging and overdischarging, can be stably charged and discharged repeatedly, and theoretically do not require maintenance; green and environmentally friendly. Supercapacitors do not use heavy metals and other harmful chemicals in the production process, and have a long life, so they are a new type of green and environmentally friendly power source.

[0003] Therefore, energy storage through supercapacitors has been gradually promoted and used. Among them, the power density of the farad capacitor is high and the voltage is small. The farad capacitor is connected in series in many applications, but it will bring the following problems:

[0004] (1) The charging current is high, and the general adapter will be pulled to undervoltage, resulting in output protection;

[0005] (2) Series connection brings about the problem of equalized charging. If individual capacitors are overcharged, it will affect the life and quality of the capacitors.

[0006] (3) The use of diode switching during charging and discharging causes a series of problems such as low efficiency and high heat generation. Summary of the invention

[0007] In order to overcome the above technical problems, the present invention proposes a charging and discharging system and method that can switch different charging modes by controlling the charging current of a farad capacitor through an MCU, which is achieved by the following technical solutions:

[0008] A supercapacitor charging and discharging system includes a power supply, an MCU, a charging capacitor, a charging circuit, a discharging circuit, and a load connected to the discharging circuit.

[0009] The positive electrode of the charging capacitor is connected to the power supply, and the negative electrode of the charging capacitor is connected to the external power ground via the inductor, the switch element, and the current collection resistor in sequence to form a charging circuit;

[0010] The current collection resistor is connected to the current collection pin of the MCU through the amplifier circuit to collect the current value of the charging circuit. The PWM pin of the MCU is connected to the switch element to control the current value of the charging circuit, and the inductor is connected in parallel with the freewheeling diode;

[0011] The positive electrode and the negative electrode of the charging capacitor are grounded via a voltage collection resistor, respectively. The voltage collection resistor is connected to a voltage collection pin of the MCU to collect the voltage values ​​of the positive electrode and the negative electrode of the charging capacitor, and the charging voltage of the charging capacitor is measured by the voltage difference;

[0012] The discharge circuit includes a bleed resistor and a first MOS tube, the positive electrode of the charging capacitor is also connected to the negative electrode of the charging capacitor via the bleed resistor and the first MOS tube in sequence, and the conduction and cutoff of the first MOS tube are controlled by the discharge pin of the MCU;

[0013] The load connected to the discharge circuit includes an operational amplifier, a discharge freewheeling diode and a second MOS tube, the source and drain of the second MOS tube are connected to the anode and cathode of the discharge freewheeling diode, the gate of the second MOS tube is connected to the output end of the operational amplifier, the anode of the discharge freewheeling diode is connected to the positive electrode of the charging capacitor on one side and to the inverting input end of the operational amplifier on another side, and the cathode of the discharge freewheeling diode is connected to the external power supply ground on one side and to the non-inverting input end of the operational amplifier on another side.

[0014] Furthermore, the switch element is a third MOS tube, and the PWM pin of the MCU is connected to the gate of the third MOS tube via a low-side gate driver chip.

[0015] Furthermore, the discharge circuit also includes a transistor, the gate of the first MOS transistor is connected to the collector of the transistor, the emitter of the transistor is grounded, the base of the transistor is connected to the discharge pin of the MCU, and the gate of the first MOS transistor is connected to a voltage regulator diode.

[0016] Furthermore, the power supply generates the working power supply of the MCU through a voltage stabilizing chip.

[0017] Furthermore, the negative electrode of the charging capacitor is provided with a capacitor ground.

[0018] Furthermore, the MCU is also connected to a Bluetooth module.

[0019] A supercapacitor charging and discharging method, characterized in that any of the above-mentioned farad capacitor charging and discharging systems is used to control the charging current by PID method, comprising the following steps:

[0020] Determine whether the charging power supply is connected, if not, enter standby mode; if so, detect the charging power supply voltage;

[0021] Determine whether the charging power supply voltage is greater than Vdcmax, if not, detect the capacitance voltage of the charging capacitor, if yes, return to standby, wherein the capacitance voltage of the charging capacitor includes the capacitance voltage of the single-cell charging capacitor and the capacitance voltage of the overall charging capacitor;

[0022] According to the charging voltage, different charging modes are entered:

[0023] If the capacitor voltage of the overall charging capacitor is less than Vmin, the trickle charging mode is turned on; if the capacitor voltage of the overall charging capacitor is greater than or equal to Vmin, the constant current charging mode is turned on, where Vmin is defined as the capacitor voltage too low threshold;

[0024] If it is detected that the capacitor voltage of any single-cell charging capacitor is greater than or equal to Vcapmax, the voltage-balanced charging mode is turned on, where the single-cell charging capacitor with a charging voltage greater than or equal to Vcapmax is defined as a fully charged state;

[0025] According to different charging modes, control the charging current:

[0026] Turn on the trickle charge mode and control the charging current to I1; turn on the constant current charge mode and control the charging current to Imax;

[0027] The voltage-equalizing charging mode is turned on, and the charging current is controlled to be Imdm2. After the power is released, when any single-cell charging capacitor has not reached the full charge state, the charging current is controlled to be Imdm1.

[0028] Furthermore, if the load capacity is insufficient and the charging power supply voltage is detected to be low, the constant voltage charging mode is entered to charge at a constant current voltage value.

[0029] Furthermore, whether the charging power supply is connected is determined by whether the charging capacitor generates a floating voltage. If Vdc>Vrch+Vcap, it is determined that the charging power supply is connected. If Vdc≤Vrch+Vcap, it is determined that the charging power supply is connected, where Vdc is the charging power supply voltage, Vcap is the capacitor voltage of the overall charging capacitor, and Vrch is the charging detection threshold.

[0030] Furthermore, the real-time parameters of the charging capacitor are monitored through the Bluetooth module.

[0031] The present invention provides a supercapacitor charging and discharging system and method, and the beneficial effects of the invention are: being able to detect the charging power supply voltage, and the charging voltage and charging current of the charging capacitor in real time, and controlling the charging current in a PID manner through a PWM interface of an MCU, and switching different charging modes such as a trickle charging mode, a constant current charging mode, a voltage-equalizing charging mode, and a constant voltage charging mode by setting a charging power supply voltage threshold and a charging voltage threshold, and controlling the size of the charging current according to different charging modes, and when connected to a load for discharge, by setting a MOS tube to be turned on, heating problems caused by a diode voltage drop are avoided, thereby ensuring the safety and stability of the charging and discharging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A circuit diagram of a charge-discharge system MCU in one embodiment of the present invention;

[0033] Figure 2 A circuit diagram of a voltage stabilizing chip of a charging and discharging system in one embodiment of the present invention;

[0034] Figure 3 A circuit diagram of a charging and discharging system in accordance with an embodiment of the present invention in which a plurality of charging capacitors are connected in series;

[0035] Figure 4 A circuit diagram of a single set of charging capacitors in one embodiment of the present invention;

[0036] Figure 5 A current collection and control circuit diagram of a charging and discharging system in one embodiment of the present invention;

[0037] Figure 6 A flow chart of a charging and discharging method in one embodiment of the present invention; DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the embodiments. The embodiments described are only a part of the present invention. These embodiments are only used to explain the present invention and do not constitute any limitation to the scope of the present invention.

[0039] A supercapacitor charging and discharging system, wherein a power supply charges a plurality of charging capacitors connected in series through a charging circuit, and a current acquisition circuit detects the charging current of the charging circuit in real time, and a voltage acquisition circuit detects the capacitor voltage of the charging capacitor in real time, and an MCU controls the charging current in a PID manner.

[0040] In one embodiment, as shown in the accompanying drawings of the specification, an MCU of model HC32F030J8T6 is used, the power supply is 5V-15V, represented by DCIN, and the sixth capacitor C6, the twelfth capacitor C12, the twentieth capacitor C20, the twenty-fifth capacitor C25, and the twenty-seventh capacitor C27 represent five groups of charging capacitors connected in series.

[0041] The power supply provides working power to the MCU and electrical components in the circuit through a voltage regulator chip. In this embodiment, a dual voltage regulator chip of model HT7533 (indicated by U1 in the figure) and model HT 7550 (indicated by U2 in the figure) is used. The power supply is converted into DC5V through U2, and DC5V is then converted into DC3.3V through U1.

[0042] The following takes a single group of charging capacitors C27 as an example to illustrate its charging and discharging process. The positive electrode of the twenty-seventh capacitor C27 is connected to DCIN, and its negative electrode is connected to the external power supply ground PGND in turn through the second inductor L2, the twentieth MOS tube Q20, and the current collection resistor (the seventy-sixth resistor R76 and the seventy-seventh resistor R77 connected in parallel) to form a charging circuit. When charging, the twentieth MOS tube Q20 is turned on. Further, the charging circuit also includes a ninth diode D9, the anode of the ninth diode D9 is connected between the second inductor L2 and the twentieth MOS tube Q20, and its cathode is connected to the positive electrode of the twenty-seventh capacitor C27, which is used as a freewheeling diode of the second inductor L2 of the charging circuit. Further, the negative electrode of the twenty-seventh capacitor C27 is also set to the capacitor ground CGND, that is, a common DCIN end is adopted, and the floating ground mode is used to supply power to eliminate AC interference.

[0043] The current collection pin of the MCU is connected between the twentieth MOS tube Q20 and the current collection resistor through an amplifier, and is used to collect the charging current of the charging circuit. In this example, the twentieth MOS tube Q20 adopts an N-channel MOS tube, whose source is connected to the current collection resistor, whose drain is connected to the second inductor L2, and whose gate is connected to the PWM pin of the MCU through a low-side gate driver chip. The magnitude of the charging current is controlled by the current duty cycle, that is, the charging current is controlled in a PID manner. This is a technical means well known to those skilled in the art, and its working principle is not specifically described.

[0044] A voltage acquisition circuit is provided at both the positive terminal and the negative terminal of the twenty-seventh capacitor C27, and the capacitor voltage of the twenty-seventh capacitor C27 is calculated through the voltage difference between the two ends. Specifically, the positive electrode of the twenty-seventh capacitor C27 is connected to the ground GND via the fifty-second resistor R52, the thirteenth MOS transistor Q13, and the fifty-fourth resistor R54 in sequence, and the voltage collection pin of the MCU is connected between the thirteenth MOS transistor Q13 and the fifty-fourth resistor R54, wherein the thirteenth MOS transistor Q13 adopts an N-channel MOS transistor, a source electrode thereof is connected to the fifty-fourth resistor R54, a drain electrode thereof is connected to the fifty-second resistor R52, and a gate electrode thereof is connected to the voltage collection control pin of the MCU; the negative electrode of the twenty-seventh capacitor C27 is connected to the ground GND via the sixteenth MOS transistor Q16, the sixty-third resistor R63, and the sixty-sixth resistor R66 in sequence, and the voltage collection pin of the MCU is connected between the sixty-third resistor R63 and the sixty-sixth resistor R66, wherein the sixteenth MOS transistor Q16 adopts an N-channel MOS transistor, a source electrode thereof is connected to the sixty-third resistor R63, a drain electrode thereof is connected to the negative electrode of the twenty-seventh capacitor C27, and a gate electrode thereof is connected to the voltage collection control pin of the MCU. When the voltage acquisition control pin of the MCU outputs a high level, the thirteenth MOS tube Q13 and the sixteenth MOS tube Q16 are turned on, and the voltage values ​​of the positive and negative electrodes of the twenty-seventh capacitor C27 are obtained through the fifty-second resistor R52 and the fifty-fourth resistor R54, and the sixty-third resistor R63 and the sixty-sixth resistor R66. The voltage difference is the capacitor voltage of the twenty-seventh capacitor C27.

[0045] When the twenty-seventh capacitor C27 is fully charged, it discharges itself through the discharge circuit. Specifically, the discharge circuit includes a bleeder resistor, a fifteenth MOS tube Q15 and a fourteenth transistor Q14. The fifteenth MOS tube Q15 is a P-channel MOS tube, and its drain is connected to the negative electrode of the twenty-seventh capacitor C27, and its source is connected to the positive electrode of the twenty-seventh capacitor C27 through a bleeder resistor (a fifty-fifth resistor R55, a fifty-seventh resistor R57, a fifty-eighth resistor R58, and a sixtieth resistor R60 connected in parallel), and its gate is connected to the ground GND through the sixty-second resistor R62 and the fourteenth transistor Q14 in turn, and a second diode D10 for voltage stabilization is also arranged between its gate and its source, wherein the collector of the fourteenth transistor Q14 is connected to the sixty-second resistor R62, its emitter is connected to the ground GND, and its base is connected to the discharge pin of the MCU. When the twenty-seventh capacitor C27 is fully charged, the discharge pin of the MCU outputs a high level, so that the fourteenth transistor Q14 is turned on, and then the fifteenth MOS tube Q15 is turned on to discharge through the bypass leakage resistor.

[0046] When a load is connected between the positive electrode of the twenty-seventh capacitor C27 and the external power ground PGND, the twenty-seventh capacitor C27 is connected to the discharge circuit through the load and discharged. The load connected to the discharge circuit includes the eleventh diode D11 (also including the twelfth diode D12 and the thirteenth diode D13 connected in parallel), the seventeenth MOS transistor Q17 (also including the eighteenth MOS transistor Q18 and the twenty-first MOS transistor Q21 connected in parallel) and the operational amplifier, wherein the seventeenth MOS transistor Q17 is an N-channel MOS transistor, the gate of which is connected to the output end of the operational amplifier, the source of which is connected to the external power ground PGND, and the drain of which is connected to the positive electrode of the twenty-seventh capacitor C27, the anode of the eleventh diode D11 is connected to the external power ground PGND, and connected to the non-inverting input end of the operational amplifier through the eighty-second resistor R82, and the cathode of which is connected to the positive electrode of the twenty-seventh capacitor C27, and connected to the reverse input end of the operational amplifier through the seventy-fifth resistor R75. When a load RL is connected between the positive electrode of the twenty-seventh capacitor C27 and the external power ground PGND, the eleventh diode D11, the twelfth diode D12 and the thirteenth diode D13 generate a voltage drop, so that the level of the non-inverting input terminal of the operational amplifier is greater than the level of the inverting input terminal thereof, so that the output terminal of the operational amplifier outputs a high level, and the seventeenth MOS transistor Q17, the eighteenth MOS transistor Q18 and the twenty-first MOS transistor Q21 are turned on, so that the output internal resistance is reduced to the minimum, thereby effectively avoiding the heating problem.

[0047] Based on the same inventive concept, an embodiment of the present invention further provides a supercapacitor charging and discharging method, which uses the above-mentioned farad capacitor charging and discharging system, including the following steps:

[0048] Determine whether the charging power supply is connected, and if not, enter standby mode; if yes, detect the charging power supply voltage, specifically, determine whether the charging power supply is connected by whether the charging capacitor generates a floating voltage;

[0049] Determine whether the charging power supply voltage is greater than Vdcmax, if not, detect the capacitance voltage of the charging capacitor, if yes, return to standby, wherein the capacitance voltage of the charging capacitor includes the capacitance voltage of the single-cell charging capacitor and the capacitance voltage of the overall charging capacitor;

[0050] According to the charging voltage, different charging modes are entered: if the capacitor voltage of the overall charging capacitor is less than Vmin, the trickle charging mode is turned on; if the capacitor voltage of the overall charging capacitor is greater than or equal to Vmin, the constant current charging mode is turned on, where Vmin is defined as the capacitor voltage too low threshold; if it is detected that the capacitor voltage of any single charging capacitor is greater than or equal to Vcapmax, the voltage equalization charging mode is turned on, where the single charging capacitor with a charging voltage greater than or equal to Vcapmax is defined as a fully charged state;

[0051] According to different charging modes, the charging current is controlled: when the trickle charging mode is turned on, the charging current is controlled to I1; when the constant current charging mode is turned on, the charging current is controlled to Imax; when the voltage equalization charging mode is turned on, the charging current is controlled to Imdm2, and after the power is released, when any single charging capacitor has not reached the full charge state, the charging current is controlled to Imdm1.

[0052] In one embodiment, DCIN is 15V, Vmin is set to 4V, I1 is set to 0.2A, Imax is set to 3A, Vcapmax is set to 2.5V, Imdm1 is set to 1A, Imdm2 is set to 0.2A, and Vdcmax is set to 16V.

[0053] After initialization standby, first determine whether the charging power supply is connected. When the charging power supply is connected, the charging capacitor generates a floating voltage. If Vdc>Vrch+Vcap, it is determined that the charging power supply is connected. If Vdc≤Vrch+Vcap, it is determined that the charging power supply is connected, where Vdc is the charging power supply voltage, Vcap is the capacitor voltage of the overall charging capacitor, and Vrch is the charging detection threshold. In this embodiment, Vrch is set to 1V.

[0054] After it is determined that the charging power source is connected, it is further determined whether the charging power source is too large. If Vdc exceeds 16V, the twentieth MOS tube Q20 is disconnected, charging is stopped, and the indicator light flashes for prompting.

[0055] When it is confirmed that the charging power supply is not over-voltage, if the capacitor voltage of the overall charging capacitor is less than 4V, the trickle charging mode is turned on and the charging current is controlled to 0.2A; if the capacitor voltage of the overall charging capacitor is greater than or equal to 4V, the constant current charging mode is turned on and the charging current is controlled to 3A; if it is detected that the capacitor voltage of any single charging capacitor is greater than or equal to 2.5V, the voltage-equalizing charging mode is turned on and the charging current is controlled to 0.2A. When the fully charged charging capacitor is discharged by the load and exits the fully charged state, the charging current is controlled to 1A. In addition, when the load is too large, it is detected that the charging power supply voltage is pulled down, and the constant voltage charging mode is entered to charge at a constant current voltage value.

[0056] Furthermore, the MCU is also connected to a Bluetooth module, through which the parameters of the charging capacitor can be monitored in real time.

[0057] Therefore, the supercapacitor charging and discharging system and method can ensure safe and stable charging of the charging capacitor and discharge when connected to a load.

[0058] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A supercapacitor charging and discharging system, characterized in that: Including power supply, MCU, charging capacitor, charging circuit, discharge circuit and load connected to the discharge circuit, The positive electrode of the charging capacitor is connected to the power supply, and the negative electrode of the charging capacitor is connected to the external power ground via the inductor, the switch element, and the current collection resistor in sequence to form a charging circuit; The current collection resistor is connected to the current collection pin of the MCU through the amplifier circuit to collect the current value of the charging circuit. The PWM pin of the MCU is connected to the switch element to control the current value of the charging circuit, and the inductor is connected in parallel with the freewheeling diode; The positive electrode and the negative electrode of the charging capacitor are grounded via a voltage collection resistor, respectively. The voltage collection resistor is connected to a voltage collection pin of the MCU to collect the voltage values ​​of the positive electrode and the negative electrode of the charging capacitor, and the charging voltage of the charging capacitor is measured by the voltage difference; The discharge circuit includes a bleed resistor and a first MOS tube, the positive electrode of the charging capacitor is also connected to the negative electrode of the charging capacitor via the bleed resistor and the first MOS tube in sequence, and the conduction and cutoff of the first MOS tube are controlled by the discharge pin of the MCU; The load access discharge loop includes an operational amplifier, a discharge freewheeling diode and a second MOS tube, the source and drain of the second MOS tube are connected to the anode and cathode of the discharge freewheeling diode, the gate of the second MOS tube is connected to the output end of the operational amplifier, the anode of the discharge freewheeling diode is connected to the positive electrode of the charging capacitor on one side and to the inverting input end of the operational amplifier on another side, the cathode of the discharge freewheeling diode is connected to the external power supply ground on one side and to the non-inverting input end of the operational amplifier on another side; the switch element is a third MOS tube, and the PWM pin of the MCU is connected to the gate of the third MOS tube via a low-side gate driver chip; The discharge circuit also includes a transistor, the gate of the first MOS transistor is connected to the collector of the transistor, the emitter of the transistor is grounded, the base of the transistor is connected to the discharge pin of the MCU, and the gate of the first MOS transistor is connected to a voltage regulator diode.

2. A supercapacitor charging and discharging system according to claim 1, characterized in that: The power supply generates the working power of the MCU through a voltage stabilizing chip.

3. A supercapacitor charging and discharging system according to claim 1, characterized in that: The negative electrode of the charging capacitor is provided with a capacitor ground.

4. A supercapacitor charging and discharging system according to claim 3, characterized in that: The MCU is also connected to a Bluetooth module.

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