Charging circuit and active pen

Abstract

The utility model discloses a charging circuit and an active pen, and relates to the technical field of charging management, wherein the charging circuit comprises a main control circuit, an inductance circuit, a first switch circuit, a second switch circuit, a first comparison circuit and a second comparison circuit; when the current at the output end of the first switch circuit is greater than a first reference current, the first comparison circuit outputs a first comparison signal so that the main control circuit controls the first switch circuit to be turned off and the second switch circuit to be turned on respectively; when the current at the input end of the second switch circuit is less than a second reference current, the second comparison circuit outputs a second comparison signal so that the main control circuit controls the first switch circuit to be turned on and the second switch circuit to be turned off respectively; the utility model aims to shorten the charging time of the active pen.

Description

Technical Field

[0001] The utility model relates to the technical field of charging management, in particular to a charging circuit and an active pen. Background Art

[0002] As the power source of the active pen, the supercapacitor is equivalent to its battery. Due to the size limit of the active pen, the supercapacitor is generally selected to be 1~10F. If the supercapacitor capacity is 8F, the charging limit voltage is 2.7V, and the charging current is 500mA, according to the capacitance formula I=CdU / dt, the theoretical charging time is calculated to be 8F*2.7V / 0.5A=43S.

[0003] If a linear charging IC is used to charge a supercapacitor, its thermal resistance parameter θja is generally 100℃ / W. The power dissipation of the linear charging IC is Pd=Vin*Iin-Vout*Iout=[5V-(0~2.7V)]*0.5A=1.15~2.5W. The temperature rise of the charging IC during the charging process is Pd*θja=115℃~250℃. According to the ambient temperature of 25℃, the junction temperature of the charging IC during the charging process is 140~275℃, where Vin and Iin are the input voltage and input current respectively, and Vout and Iout are the output voltage and output current of the linear charging IC respectively.

[0004] Many semiconductor devices, especially those in plastic packages, have a maximum rated junction temperature of 150°C. Exceeding this temperature may result in reduced performance, reduced reliability, or even damage to the device. To avoid this problem, ICs are equipped with an over-temperature protection mechanism.

[0005] Because the charging IC has an internal over-temperature protection circuit, when the chip junction temperature rises to 150°C, the chip will shut down automatically, wait for the chip junction temperature to cool down, and then resume work after a certain period of hysteresis. If the shutdown + hysteresis time and the charging time each account for 50%, then the total impulse time will increase to 43 / 50% = 86S.

[0006] The 86S time is not a good experience for users because the charging time is too long. In addition, because the charging IC generates too much heat during charging, users will obviously feel the temperature of the pen tube getting hot during long-term charging, which is a bad experience. Utility Model Content

[0007] The main purpose of the utility model is to provide a charging circuit and an active pen, aiming to shorten the charging time of the active pen.

[0008] To achieve the above object, the utility model provides a charging circuit, which is applied to an active pen, the active pen includes a supercapacitor, and the charging circuit includes:

[0009] A power input terminal and a power output terminal, wherein the power output terminal is electrically connected to the super capacitor;

[0010] Main control circuit;

[0011] an inductor circuit, wherein a second end of the inductor circuit is electrically connected to the power supply output end;

[0012] a first switch circuit, wherein an input end of the first switch circuit is electrically connected to the power input end, an output end of the first switch circuit is electrically connected to a first end of the inductor circuit, and a controlled end of the first switch circuit is electrically connected to a control end of the main control circuit;

[0013] a second switch circuit, wherein an input end of the second switch circuit is electrically connected to the first end of the inductor circuit, an output end of the second switch circuit is grounded, and a controlled end of the second switch circuit is electrically connected to a control end of the main control circuit;

[0014] a first comparison circuit, wherein a first input terminal of the first comparison circuit is electrically connected to an output terminal of the first switch circuit, a second input terminal of the first comparison circuit is connected to a first reference current, an output terminal of the first comparison circuit is electrically connected to a detection terminal of the main control circuit, and when a current at the output terminal of the first switch circuit is greater than the first reference current, the first comparison circuit outputs a first comparison signal;

[0015] a second comparison circuit, wherein a first input terminal of the second comparison circuit is electrically connected to an input terminal of the second switch circuit, a second input terminal of the second comparison circuit is connected to a second reference current, an output terminal of the second comparison circuit is electrically connected to a detection terminal of the main control circuit, and when a current at the input terminal of the second switch circuit is less than the second reference current, the second comparison circuit outputs a second comparison signal;

[0016] The main control circuit controls the first switch circuit to be turned off and the second switch circuit to be turned on respectively according to the received first comparison signal;

[0017] The main control circuit controls the first switch circuit to be turned on and the second switch circuit to be turned off according to the received second comparison signal.

[0018] In one embodiment, the first switch circuit includes:

[0019] a first switch tube, wherein an input end of the first switch tube is electrically connected to the power input end, an output end of the first switch tube is electrically connected to a first end of the inductor circuit, and a controlled end of the first switch tube is electrically connected to a control end of the main control circuit;

[0020] The second switch circuit comprises:

[0021] A second switch tube, wherein an input end of the second switch tube is electrically connected to the first end of the inductor circuit, an output end of the second switch tube is grounded, and a controlled end of the second switch tube is electrically connected to a control end of the main control circuit.

[0022] In one implementation, both the first switch tube and the second switch tube are NMOS tubes.

[0023] In one embodiment, the inductor circuit comprises:

[0024] A first inductor, wherein a first end of the first inductor is electrically connected to an output end of the first switch circuit and an input end of the second switch circuit respectively, and a second end of the first inductor is electrically connected to an output end of the power supply.

[0025] In one embodiment, the first comparison circuit includes:

[0026] A first comparator, wherein a non-inverting terminal of the first comparator is electrically connected to an output terminal of the first switch circuit, an inverting terminal of the first comparator is connected to a first reference current, and an output terminal of the first comparator is electrically connected to a detection terminal of the main control circuit;

[0027] The second comparison circuit comprises:

[0028] A second comparator, wherein the inverting end of the second comparator is electrically connected to the input end of the second switch circuit, the non-inverting end of the second comparator is connected to the second reference current, and the output end of the second comparator is electrically connected to the detection end of the main control circuit.

[0029] In one implementation, the main control circuit, the first switch circuit, the second switch circuit, the first comparison circuit, and the second comparison circuit are all integrated into the same chip.

[0030] In one embodiment, the charging circuit further includes:

[0031] a first voltage divider circuit and a first amplifier circuit, wherein a first end of the first voltage divider circuit is electrically connected to an output end of the inductor circuit, a second end of the first voltage divider circuit is electrically connected to a first input end of the first amplifier circuit, a second input end of the first amplifier circuit is connected to a first reference voltage, and an output end of the first amplifier circuit is electrically connected to a detection end of the main control circuit;

[0032] The first amplifier circuit is used to amplify the difference between the voltage of the first voltage divider circuit and the first reference voltage, and output a corresponding first difference signal. The main control circuit controls the on-time of the first switch circuit and the on-time of the second switch circuit according to the size of the first difference signal.

[0033] In one implementation, the first voltage divider circuit includes:

[0034] A first resistor and a second resistor, wherein the first end of the first resistor is electrically connected to the second end of the inductor circuit, the second end of the first resistor is electrically connected to the first end of the second resistor, the first end of the second resistor is also electrically connected to the first input end of the first amplifier circuit, and the second end of the second resistor is grounded.

[0035] The utility model also provides an active pen, comprising a super capacitor and any one of the charging circuits described above.

[0036] The technical solution of the utility model includes a main control circuit, a first switch circuit, a second switch circuit, a first comparison circuit and a second comparison circuit. When the first switch circuit is turned on and the second switch circuit is turned off, the current input from the power input terminal charges the inductor circuit and the super capacitor at the same time. When the current stored in the inductor circuit is greater than a preset value, the current at the output terminal of the first switch circuit is greater than a first reference current value. The first comparison circuit outputs a first comparison signal to the main control circuit, and the main control circuit controls the first switch circuit to be turned off and the second switch circuit to be turned on according to the first comparison signal. When the first switch circuit is turned off and the second switch circuit is turned on, the inductor circuit is discharged to charge the super capacitor. After the current stored in the inductor circuit is released, the current at the input terminal of the second switch circuit is less than the second reference current. The second comparison circuit outputs a second comparison signal to the main control circuit, and the main control circuit controls the first switch circuit to be turned on and the second switch circuit to be turned off according to the second comparison signal, so that the current output from the power input terminal charges the inductor circuit and the super capacitor again.

[0037] With such a configuration, the output voltage reduction of the charging circuit of the utility model is realized through the switch circuit and the inductor, and the voltage reduction loss is very small, which reduces the direct loss of energy and improves the energy conversion efficiency. Since the energy conversion efficiency of the charging circuit of the utility model is high and the heat generated is less, the over-temperature protection circuit in the charging IC using the charging circuit of the utility model will not be triggered under normal circumstances, thereby shortening the charging time of the active pen and avoiding the problem that the over-temperature protection circuit of the existing linear charging IC is activated due to the high temperature, so that the linear charging IC temporarily stops working, resulting in a long charging time for the active pen. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0039] Figure 1 This is a schematic diagram of a module of an embodiment of the utility model;

[0040] Figure 2 This is a schematic diagram of the circuit structure of an embodiment of the utility model;

[0041] Figure 3 It is a module schematic diagram of another embodiment of the utility model.

[0042] Description of Figure Numbers:

[0043] 10. Main control circuit; 20. Inductor circuit; 30. First switch circuit; 40. Second switch circuit; 50. First comparison circuit; 60. Second comparison circuit; 70. First voltage divider circuit; 80. First amplifier circuit.

[0044] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0046] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0047] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the utility model.

[0048] As the power source of the active pen, the supercapacitor is equivalent to its battery. Due to the size limit of the active pen, the supercapacitor is generally selected to be 1~10F. If the supercapacitor capacity is 8F, the charging limit voltage is 2.7V, and the charging current is 500mA, according to the capacitance formula I=CdU / dt, the theoretical charging time is calculated to be 8F*2.7V / 0.5A=43S.

[0049] If a linear charging IC is used to charge a supercapacitor, its thermal resistance parameter θja is generally 100℃ / W. The power dissipation of the linear charging IC is Pd=Vin*Iin-Vout*Iout=[5V-(0~2.7V)]*0.5A=1.15~2.5W. According to the ambient temperature of 25℃, the junction temperature of the charging IC during the charging process is 140~275℃, where Vin and Iin are the input voltage and input current respectively, and Vout and Iout are the output voltage and output current of the linear charging IC respectively.

[0050] Many semiconductor devices, especially those in plastic packages, have a maximum rated junction temperature of 150°C. Exceeding this temperature may result in reduced performance, reduced reliability, or even damage to the device. To avoid this problem, ICs are equipped with an over-temperature protection mechanism.

[0051] Because the charging IC has an internal over-temperature protection circuit, when the chip junction temperature rises to 150°C, the chip will shut down automatically, wait for the chip junction temperature to cool down, and then resume work after a certain period of hysteresis. If the shutdown + hysteresis time and the charging time each account for 50%, then the total impulse time will increase to 43 / 50% = 86S.

[0052] The 86S time is not a good experience for users because the charging time is too long. In addition, because the charging IC generates too much heat during charging, users will obviously feel the temperature of the pen tube getting hot during long-term charging, which is a bad experience.

[0053] Therefore, the utility model provides a charging circuit and an active pen, aiming to shorten the charging time of the active pen.

[0054] refer to Figure 1 In one embodiment of the utility model, a charging circuit is applied to an active pen, the active pen includes a super capacitor, and the charging circuit includes:

[0055] A power input terminal and a power output terminal, wherein the power output terminal is electrically connected to the super capacitor;

[0056] Main control circuit 10;

[0057] an inductor circuit 20, wherein a second end of the inductor circuit 20 is electrically connected to the power output end;

[0058] a first switch circuit 30, wherein an input end of the first switch circuit 30 is electrically connected to the power input end, an output end of the first switch circuit 30 is electrically connected to a first end of the inductor circuit 20, and a controlled end of the first switch circuit 30 is electrically connected to a control end of the main control circuit 10;

[0059] a second switch circuit 40, wherein an input end of the second switch circuit 40 is electrically connected to a first end of the inductor circuit 20, an output end of the second switch circuit 40 is grounded, and a controlled end of the second switch circuit 40 is electrically connected to a control end of the main control circuit 10;

[0060] a first comparison circuit 50, wherein a first input terminal of the first comparison circuit 50 is electrically connected to an output terminal of the first switch circuit 30, a second input terminal of the first comparison circuit 50 is connected to a first reference current, an output terminal of the first comparison circuit 50 is electrically connected to a detection terminal of the main control circuit 10, and when a current at the output terminal of the first switch circuit 30 is greater than the first reference current, the first comparison circuit 50 outputs a first comparison signal;

[0061] a second comparison circuit 60, wherein a first input terminal of the second comparison circuit 60 is electrically connected to an input terminal of the second switch circuit 40, a second input terminal of the second comparison circuit 60 is connected to a second reference current, an output terminal of the second comparison circuit 60 is electrically connected to a detection terminal of the main control circuit 10, and when a current at the input terminal of the second switch circuit 40 is less than the second reference current, the second comparison circuit 60 outputs a second comparison signal;

[0062] The main control circuit 10 controls the first switch circuit 30 to be turned off and the second switch circuit 40 to be turned on respectively according to the received first comparison signal;

[0063] The main control circuit 10 controls the first switch circuit 30 to be turned on and the second switch circuit 40 to be turned off according to the received second comparison signal.

[0064] In this embodiment, the first switching circuit 30 and the second switching circuit 40 can be implemented by at least one switching tube, such as a MOS tube, an IGBT tube, a thyristor, a triode, a power tube, etc., and / or by at least one switching device, such as a contactor, a circuit breaker and a relay.

[0065] In this embodiment, the main control circuit 10 can be implemented by a main controller, such as MCU (Microcontroller Unit), DSP (Digital Signal Process), FPGA (Field Programmable Gate Array), SOC (System On Chip), etc.

[0066] In this embodiment, the first input end of the first comparison circuit 50 and the second input end of the second comparison circuit 60 respectively collect the current at the output end of the first switch circuit 30 and the current at the input end of the second switch circuit 40 through a current clamp. The current clamp can detect the current passing through its jaws in real time and convert it into an electrical signal that can be observed or recorded.

[0067] In this embodiment, the main control circuit 10 , the first switch circuit 30 , the second switch circuit 40 , the first comparison circuit 50 and the second comparison circuit 60 are all integrated in the same chip.

[0068] In this embodiment, the inductor circuit 20 is composed of at least one inductor. Figure 2 The first inductor L1 in.

[0069] In this embodiment, specifically, the technical solution of the utility model includes a main control circuit 10, a first switch circuit 30, a second switch circuit 40, a first comparison circuit 50 and a second comparison circuit 60. When the first switch circuit 30 is turned on and the second switch circuit 40 is turned off, the current input from the power input terminal charges the inductor circuit 20 and the supercapacitor at the same time. When the current stored in the inductor circuit 20 is greater than a preset value, the current at the output terminal of the first switch circuit 30 is greater than a first reference current value. The first comparison circuit 50 outputs a first comparison signal to the main control circuit 10, and the main control circuit 10 controls the first comparison signal according to the first comparison signal. The first switch circuit 30 is turned off and the second switch circuit 40 is turned on; when the first switch circuit 30 is turned off and the second switch circuit 40 is turned on, the inductor circuit 20 discharges to charge the super capacitor. When the current stored in the inductor circuit 20 is released, the current at the input end of the second switch circuit 40 is less than the second reference current, and the second comparison circuit 60 outputs a second comparison signal to the main control circuit 10. The main control circuit 10 controls the first switch circuit 30 to be turned on and the second switch circuit 40 to be turned off according to the second comparison signal, so that the current output from the power input end charges the inductor circuit 20 and the super capacitor again.

[0070] With such a configuration, the output voltage reduction of the charging circuit of the utility model is realized through the switch circuit and the inductor, and the voltage reduction loss is very small, which reduces the direct loss of energy and improves the energy conversion efficiency. Since the energy conversion efficiency of the charging circuit of the utility model is high and the heat generated is less, the over-temperature protection circuit in the charging IC using the charging circuit of the utility model will not be triggered under normal circumstances, thereby shortening the charging time of the active pen and avoiding the problem that the over-temperature protection circuit of the existing linear charging IC is activated due to the high temperature, so that the linear charging IC temporarily stops working, resulting in a long charging time for the active pen.

[0071] Assuming that the switching frequency FSW of the first switch circuit 30 and the second switch circuit 40 controlled by the main control circuit 10 is 3.5MHz, the impedance of the inductor circuit 20 is 4.7uH, the voltage of the supercapacitor is Vsupercap, the upper limit preset current value represented by the first reference current is 1.5A, and the energy conversion efficiency is 95%, it can be calculated that the current I flowing through the inductor circuit 20 when the voltage of the supercapacitor reaches 0V, 1.5V and 2.7V respectively L :

[0072]

[0073]

[0074]

[0075] From this, we can calculate the charging current IOUT when the supercapacitor voltage reaches 0V, 1.5V and 2.7V respectively:

[0076] I OUT =1.5A-0=1.5A, Vsupercap=0V

[0077] I OUT =1.5A-0.064A / 2≈1.5A, Vsupercap=1.5V

[0078] I OUT =1.5A-0.075A / 2≈1.5A, Vsupercap=2.7V

[0079] Referring to the above content, the charging current of the supercapacitor can be stabilized at 1.5A throughout the process. According to the chip conversion efficiency of 95%, the chip dissipation power Pd = (0 ~ 2.7V) * 1.5A / 95% * 5% = 0 ~ 0.21W is calculated. Similarly, the chip θja = 100℃ / W is added, and the temperature rise of the charging circuit of the utility model is Pd * θja = 0°C ~ 21℃. According to the ambient temperature of 25℃, the junction temperature of the charging circuit of the utility model during charging is 25℃ ~ 46℃. This temperature is the chip junction temperature and will not trigger the 150℃ temperature protection of the chip junction temperature. In actual applications, when the charging circuit of the utility model is used in an active pen, this temperature is transmitted to the PCB of the active pen, and then transmitted to the active pen housing. Due to the low temperature, it is imperceptible to the user and will not feel any heat during the charging process.

[0080] Therefore, according to the capacitance formula I = CdU / dt, at a charging current of 1.5A, the charging time of a capacitor with a capacity of 8F only requires 8F*2.7V / 1.5A=14.4S. Compared with the 86S of the existing linear charging IC, the charging time of the charging circuit of the utility model is greatly shortened.

[0081] refer to Figure 2 In one embodiment of the present utility model, the first switch circuit 30 includes:

[0082] a first switch tube Q1, wherein an input end of the first switch tube Q1 is electrically connected to the power input end, an output end of the first switch tube Q1 is electrically connected to a first end of the inductor circuit 20, and a controlled end of the first switch tube Q1 is electrically connected to a control end of the main control circuit 10;

[0083] The second switch circuit 40 includes:

[0084] The second switch tube Q2, the input end of the second switch tube Q2 is electrically connected to the first end of the inductor circuit 20, the output end of the second switch tube Q2 is grounded, and the controlled end of the second switch tube Q2 is electrically connected to the control end of the main control circuit 10.

[0085] In this embodiment, both the first switch tube Q1 and the second switch tube Q2 are NMOS tubes. When the current at the output end of the first switch tube Q1 is greater than the first reference current, the main control circuit 10 outputs a low level signal to control the first switch tube Q1 to be turned off, and outputs a high level signal to control the second switch tube Q2 to be turned on according to the first comparison signal output by the first comparison circuit 50, so that the inductor circuit 20 is discharged to charge the super capacitor; when the current at the input end of the second switch tube Q2 is less than the second reference current, the main control circuit 10 outputs a high level signal to control the first switch tube Q1 to be turned on, and outputs a low level signal to control the second switch tube Q2 to be turned off according to the second comparison signal output by the second comparison circuit 60, so that the current at the power input end charges the inductor circuit 20 and the super capacitor at the same time.

[0086] refer to Figure 2 In one embodiment of the present utility model, the first comparison circuit 50 comprises:

[0087] A first comparator U1, wherein a non-inverting terminal of the first comparator U1 is electrically connected to an output terminal of the first switch circuit 30, an inverting terminal of the first comparator U1 is connected to a first reference current, and an output terminal of the first comparator U1 is electrically connected to a detection terminal of the main control circuit 10;

[0088] The second comparison circuit 60 comprises:

[0089] The second comparator U2, the inverting end of the second comparator U2 is electrically connected to the input end of the second switch circuit 40, the non-inverting end of the second comparator U2 is connected to the second reference current, and the output end of the second comparator U2 is electrically connected to the detection end of the main control circuit 10.

[0090] In this embodiment, when the current at the output end of the first switch circuit 30 is greater than the first reference current, the first comparator U1 outputs a high-level signal to the main control circuit 10, so that the main control circuit 10 controls the first switch circuit 30 to be turned off and the second switch circuit 40 to be turned on; when the current at the input end of the second switch circuit 40 is greater than the second reference current, the second comparator U2 outputs a high-level signal to the main control circuit 10, so that the main control circuit 10 controls the first switch circuit 30 to be turned on and the second switch circuit 40 to be turned off.

[0091] refer to Figure 3 In one embodiment of the present utility model, the charging circuit further includes:

[0092] A first voltage divider circuit 70 and a first amplifier circuit 80, wherein a first end of the first voltage divider circuit 70 is electrically connected to an output end of the inductor circuit 20, a second end of the first voltage divider circuit 70 is electrically connected to a first input end of the first amplifier circuit 80, a second input end of the first amplifier circuit 80 is connected to a first reference voltage, and an output end of the first amplifier circuit 80 is electrically connected to a detection end of the main control circuit 10;

[0093] The first amplifier circuit 80 is used to amplify the difference between the voltage of the first voltage divider circuit 70 and the first reference voltage, and output a corresponding first difference signal. The main control circuit 10 controls the on-time of the first switch circuit 30 and the on-time of the second switch circuit 40 according to the size of the first difference signal.

[0094] In this embodiment, the first voltage divider circuit 70 includes:

[0095] A first resistor R1 and a second resistor R2, wherein the first end of the first resistor R1 is electrically connected to the second end of the inductor circuit 20, the second end of the first resistor R1 is electrically connected to the first end of the second resistor R2, the first end of the second resistor R2 is also electrically connected to the first input end of the first amplifier circuit 80, and the second end of the second resistor R2 is grounded.

[0096] In this embodiment, the first amplifier circuit 80 is implemented by at least one amplifier, the first voltage divider circuit 70 is used to divide the voltage at the output end of the inductor circuit 20, and the first amplifier circuit 80 is used to amplify the difference between the voltage division amount of the first voltage divider circuit 70 and the third reference voltage, and output a corresponding first difference signal. When the difference reaches a preset value, it indicates that the voltage of the inductor circuit 20 is too high. The main control circuit 10 reduces the duty cycle of the control signal output to the first switch circuit 30 and the second switch circuit 40 according to the first difference signal, so that the conduction time of the first switch circuit 30 and the conduction time of the second switch circuit 40 are both reduced, thereby reducing the output voltage at the output end of the power supply, thereby preventing excessive voltage from damaging the components in the circuit, especially the switch circuit.

[0097] The utility model also provides an active pen, comprising a super capacitor and the charging circuit as described above.

[0098] It is worth noting that, since the active pen of the present invention is based on the above-mentioned charging circuit, the embodiments of the active pen of the present invention include all technical solutions of all the embodiments of the above-mentioned charging circuit, and the technical effects achieved are also exactly the same, which will not be repeated here.

[0099] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A charging circuit, applied to an active pen, wherein the active pen includes a supercapacitor, characterized in that: The charging circuit comprises: A power input terminal and a power output terminal, wherein the power output terminal is electrically connected to the super capacitor; Main control circuit; an inductor circuit, wherein a second end of the inductor circuit is electrically connected to the power output end; a first switch circuit, wherein an input end of the first switch circuit is electrically connected to the power input end, an output end of the first switch circuit is electrically connected to a first end of the inductor circuit, and a controlled end of the first switch circuit is electrically connected to a control end of the main control circuit; a second switch circuit, wherein an input end of the second switch circuit is electrically connected to the first end of the inductor circuit, an output end of the second switch circuit is grounded, and a controlled end of the second switch circuit is electrically connected to a control end of the main control circuit; a first comparison circuit, wherein a first input terminal of the first comparison circuit is electrically connected to an output terminal of the first switch circuit, a second input terminal of the first comparison circuit is connected to a first reference current, an output terminal of the first comparison circuit is electrically connected to a detection terminal of the main control circuit, and when a current at the output terminal of the first switch circuit is greater than the first reference current, the first comparison circuit outputs a first comparison signal; a second comparison circuit, wherein a first input terminal of the second comparison circuit is electrically connected to an input terminal of the second switch circuit, a second input terminal of the second comparison circuit is connected to a second reference current, an output terminal of the second comparison circuit is electrically connected to a detection terminal of the main control circuit, and when a current at the input terminal of the second switch circuit is less than the second reference current, the second comparison circuit outputs a second comparison signal; The main control circuit controls the first switch circuit to be turned off and the second switch circuit to be turned on respectively according to the received first comparison signal; The main control circuit controls the first switch circuit to be turned on and the second switch circuit to be turned off according to the received second comparison signal.

2. The charging circuit according to claim 1, characterized in that: The first switch circuit comprises: a first switch tube, wherein an input end of the first switch tube is electrically connected to the power input end, an output end of the first switch tube is electrically connected to a first end of the inductor circuit, and a controlled end of the first switch tube is electrically connected to a control end of the main control circuit; The second switch circuit comprises: A second switch tube, wherein an input end of the second switch tube is electrically connected to the first end of the inductor circuit, an output end of the second switch tube is grounded, and a controlled end of the second switch tube is electrically connected to a control end of the main control circuit.

3. The charging circuit according to claim 2, characterized in that: The first switch tube and the second switch tube are both NMOS tubes.

4. The charging circuit according to claim 1, characterized in that: The inductor circuit comprises: A first inductor, wherein a first end of the first inductor is electrically connected to an output end of the first switch circuit and an input end of the second switch circuit respectively, and a second end of the first inductor is electrically connected to an output end of the power supply.

5. The charging circuit according to claim 1, characterized in that: The first comparison circuit comprises: A first comparator, wherein a non-inverting terminal of the first comparator is electrically connected to an output terminal of the first switch circuit, an inverting terminal of the first comparator is connected to a first reference current, and an output terminal of the first comparator is electrically connected to a detection terminal of the main control circuit; The second comparison circuit comprises: A second comparator, wherein the inverting end of the second comparator is electrically connected to the input end of the second switch circuit, the non-inverting end of the second comparator is connected to the second reference current, and the output end of the second comparator is electrically connected to the detection end of the main control circuit.

6. The charging circuit according to any one of claims 1 to 5, characterized in that: The main control circuit, the first switch circuit, the second switch circuit, the first comparison circuit and the second comparison circuit are all integrated in the same chip.

7. The charging circuit according to any one of claims 1 to 5, characterized in that: The charging circuit further comprises: a first voltage divider circuit and a first amplifier circuit, wherein a first end of the first voltage divider circuit is electrically connected to an output end of the inductor circuit, a second end of the first voltage divider circuit is electrically connected to a first input end of the first amplifier circuit, a second input end of the first amplifier circuit is connected to a first reference voltage, and an output end of the first amplifier circuit is electrically connected to a detection end of the main control circuit; The first amplifier circuit is used to amplify the difference between the voltage of the first voltage divider circuit and the first reference voltage, and output a corresponding first difference signal. The main control circuit controls the on-time of the first switch circuit and the on-time of the second switch circuit according to the size of the first difference signal.

8. The charging circuit according to claim 7, characterized in that: The first voltage divider circuit comprises: A first resistor and a second resistor, wherein the first end of the first resistor is electrically connected to the second end of the inductor circuit, the second end of the first resistor is electrically connected to the first end of the second resistor, the first end of the second resistor is also electrically connected to the first input end of the first amplifier circuit, and the second end of the second resistor is grounded.

9. An active pen, characterized in that: The invention comprises a super capacitor and a charging circuit as claimed in any one of claims 1 to 8.

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