RTC circuit compatible with batteries and supercapacitors

Abstract

This application relates to an RTC circuit compatible with batteries and supercapacitors, comprising: a clock chip, a supercapacitor, a battery, a first charging circuit, and a second charging circuit; the input terminals of both the first and second charging circuits are electrically connected to the output terminal of a main power supply; the output terminal of the first charging circuit is electrically connected to the VDD pin of the clock chip; the output terminal of the second charging circuit is electrically connected to the supercapacitor, suitable for simultaneously supplying power to the supercapacitor through the second charging circuit while the main power supply supplies power to the clock chip via the first charging circuit; the supercapacitor is electrically connected to the VDD pin of the clock chip, suitable for supplying power to the clock chip via the supercapacitor when the main power supply is de-energized and the output voltage of the supercapacitor is higher than the output voltage of the battery; the battery is electrically connected to the VDD pin of the clock chip via diode D1, suitable for supplying power to the clock chip via the battery when the main power supply is de-energized and the output voltage of the supercapacitor is lower than the battery voltage.

Description

Technical Field

[0001] This application relates to the field of real-time clock technology, and more particularly to an RTC circuit compatible with batteries and supercapacitors. Background Technology

[0002] The real-time clock (RTC) circuit is the core module for maintaining the time reference of electronic devices. Its typical structure includes a quartz crystal oscillator, a frequency divider, a calendar counter, a data register, and a serial communication interface. When the main power supply is normal, the RTC is powered by the main power supply. When the main power supply is disconnected, the RTC immediately switches to the backup power supply to ensure the continuity and accuracy of timing.

[0003] Existing backup power supplies use a single type of power supply device, mostly disposable batteries or supercapacitors. However, while disposable batteries can provide a continuous and stable static power supply for real-time clocks, they can cause deep discharge when the real-time clock experiences a sudden surge in current demand. This accelerates electrode passivation, shortens the battery's lifespan, and necessitates frequent battery replacements. Supercapacitors can better handle the sudden surge in current demand required by real-time clocks, but their energy storage capacity is relatively limited. In the event of a prolonged disconnection of the main power supply, they cannot provide a continuous and stable power supply for the real-time clock.

[0004] Therefore, how to make both disposable batteries and supercapacitors compatible backup power sources so that the backup power source can meet the instantaneous high current demand while providing long-term static power supply for the real-time clock has become a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, this application proposes an RTC circuit compatible with batteries and supercapacitors, including: a clock chip, a supercapacitor, a battery, a first charging circuit, and a second charging circuit;

[0006] The input terminals of both the first and second charging circuits are suitable for electrical connection to the output terminal of the main power supply.

[0007] The output of the first charging circuit is electrically connected to the VDD pin of the clock chip;

[0008] The output of the second charging circuit is electrically connected to the supercapacitor, which is suitable for supplying power to the supercapacitor through the second charging circuit at the same time as the main power supply supplies power to the clock chip through the first charging circuit.

[0009] The supercapacitor is electrically connected to the VDD pin of the clock chip, which is suitable for supplying power to the clock chip by the supercapacitor when the main power supply is off and the output voltage of the supercapacitor is higher than the output voltage of the battery.

[0010] The battery is electrically connected to the VDD pin of the clock chip via diode D1, which is suitable for supplying power to the clock chip by the battery when the main power supply is off and the output voltage of the supercapacitor is lower than the battery voltage.

[0011] In one possible implementation, the first charging circuit includes a diode D4; the anode of diode D4 is electrically connected to the output of the main power supply, and the cathode of diode D4 is electrically connected to the VDD pin of the clock chip.

[0012] In one possible implementation, the second charging circuit includes a diode D3; the anode of diode D3 is electrically connected to the output of the main power supply, and the cathode of diode D3 is electrically connected to the input of the supercapacitor through a current-limiting resistor.

[0013] In one possible implementation, diode D2 is also included; the anode of diode D2 is electrically connected to the output terminal of the supercapacitor through a current-limiting resistor, and the cathode of diode D2 is electrically connected to the VDD pin of the clock chip; and one end of the supercapacitor is grounded.

[0014] In one possible implementation, a decoupling capacitor is also included; one end of the decoupling capacitor is electrically connected to the anode of diode D3 and the anode of diode D4, respectively, and the other end of the decoupling capacitor is grounded.

[0015] In one possible implementation, an oscillator is also included; the input of the oscillator is electrically connected to the OSCI pin of the clock chip, and the output of the oscillator is electrically connected to the OSCO pin of the clock chip.

[0016] In one possible implementation, the VSS pin of the clock chip is grounded.

[0017] In one possible implementation, the battery is a disposable button cell.

[0018] Beneficial effects

[0019] When the main power supply Vmain is supplying power, the first charging circuit transmits the current output by the main power supply Vmain to the clock chip U1. At the same time, the second charging circuit transmits the current output by the main power supply Vmain to the supercapacitor C1 for charging. Since the voltage output by the main power supply Vmain is higher than the voltage of the supercapacitor C1 and the voltage of the battery VCC-BAT, the supercapacitor C1 and the battery VCC-BAT do not supply power to the clock chip U1 at this time.

[0020] When the main power supply Vmain is de-energized, the first and second charging circuits are in the off state, and the power supply mode of the clock chip U1 switches to either the supercapacitor C1 or the battery VCC-BAT. Specifically:

[0021] When the voltage of battery VCC-BAT is higher than the voltage of supercapacitor C1, diode D1 conducts, creating a circuit between battery VCC-BAT and clock chip U1, while creating an open circuit between supercapacitor C1 and clock chip U1. At this time, battery VCC-BAT supplies power to clock chip U1, while supercapacitor C1 does not supply power to clock chip U1.

[0022] When the voltage of battery VCC-BAT drops below the voltage of supercapacitor C1, diode D1 is turned off, and there is an open circuit between battery VCC-BAT and clock chip U1, while there is a closed circuit between supercapacitor C1 and clock chip U1. At this time, supercapacitor C1 supplies power to clock chip U1, and battery VCC-BAT does not supply power to clock chip U1.

[0023] When the voltage of supercapacitor C1 is equal to the voltage of battery VCC-BAT, since the internal resistance of supercapacitor C1 is lower than that of battery VCC-BAT, according to the current distribution principle, diode D1 is cut off, there is an open circuit between battery VCC-BAT and clock chip U1, and there is a closed circuit between supercapacitor C1 and clock chip U1. Supercapacitor C1 prioritizes powering clock chip U1, while battery VCC-BAT does not power clock chip U1.

[0024] When the main power supply Vmain resumes power supply, it supplies power to the clock chip U1 while continuing to charge the supercapacitor C1 through the second charging circuit. When the main power supply Vmain is de-energized again, the power supply process of the battery VCC-BAT and the supercapacitor C1 is repeated.

[0025] This application utilizes a supercapacitor C1 and a battery VCC-BAT to achieve automatic switching between them, forming a complementary power supply mechanism. The supercapacitor C1, with its low internal resistance, powers the clock chip U1 when its output voltage is higher than or equal to the battery VCC-BAT voltage. This reduces electrode passivation caused by deep discharge in the battery VCC-BAT, extending its lifespan and reducing its replacement frequency. Simultaneously, when the output voltage of the supercapacitor C1 is lower than the battery VCC-BAT voltage... When the voltage of C-BAT is low and the main power supply Vmain has not resumed power supply, it automatically switches to battery power supply VCC-BAT. With its high energy density, it provides a long-term stable static current for the clock chip U1, avoiding timing interruptions caused by the limited energy storage capacity of the supercapacitor C1, thus ensuring the continuity and accuracy of the clock chip U1's timing. At the same time, the supercapacitor C1 can be charged when the main power supply Vmain is supplying power normally, maintaining a good working condition, further improving the overall service life and reliability of the backup power supply, reducing maintenance costs, and extending the standby time of the clock chip U1.

[0026] Other features and aspects of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0027] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of this application together with the specification and serve to explain the principles of this application.

[0028] Figure 1 A circuit diagram showing an embodiment of the RTC circuit compatible with batteries and supercapacitors is provided. Detailed Implementation

[0029] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0030] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0032] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0033] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0034] This application proposes an RTC circuit compatible with batteries and supercapacitors, comprising: a clock chip U1, a supercapacitor C1, a battery VCC-BAT, a first charging circuit 100, and a second charging circuit 200; the input terminals of the first charging circuit 100 and the second charging circuit 200 are both electrically connected to the output terminal of the main power supply Vmain; the output terminal of the first charging circuit 100 is electrically connected to the VDD pin of the clock chip U1; the output terminal of the second charging circuit 200 is electrically connected to the supercapacitor C1, suitable for supplying power from the main power supply Vmain to the clock chip U1 through the first charging circuit 100. Simultaneously, power is supplied to the supercapacitor C1 through the second charging circuit 200. The supercapacitor C1 is electrically connected to the VDD pin of the clock chip U1, which is suitable for supplying power to the clock chip by the supercapacitor C1 when the main power supply Vmain is de-energized and the output voltage of the supercapacitor C1 is higher than the output voltage of the battery VCC-BAT. The battery VCC-BAT is electrically connected to the VDD pin of the clock chip U1 through the diode D1, which is suitable for supplying power to the clock chip U1 by the battery VCC-BAT when the main power supply Vmain is de-energized and the output voltage of the supercapacitor C1 is lower than the voltage of the battery VCC-BAT.

[0035] It should be noted that the main power supply Vmain is suitable for providing a 3.3V operating voltage to the clock chip U1. The main power supply Vmain is electrically connected to the VDD pin of the clock chip U1 through the first charging circuit 100, thereby stably transmitting power to the clock chip U1. Simultaneously, the main power supply Vmain charges the supercapacitor C1 through the second charging circuit 200, ensuring that the supercapacitor C1 is always fully charged or at a high charge level before the main power supply Vmain is powered off. The supercapacitor C1 is suitable for supplying power to the clock chip U1 when the main power supply Vmain is powered off and its own voltage is higher than the battery VCC-BAT. When the main power supply Vmain resumes power supply, it is charged again through the second charging circuit 200. The supercapacitor C1 has good charge and discharge performance, strong cycle reuse capability, and eliminates the need for frequent replacement of the backup power supply, reducing maintenance costs. The initial voltage of the supercapacitor C1 is... The battery is 2.7V, and the internal resistance of the supercapacitor C1 is 10mΩ. The output terminal of the battery VCC-BAT is connected to the anode of diode D1, and the cathode of diode D1 is connected to the VDD pin of the clock chip U1. The battery VCC-BAT is used to power the clock chip U1, and the diode D1 is used to limit the current flow. When the main power supply Vmain or the supercapacitor C1 is powered, the diode D1 is in the cutoff state, thereby blocking the current flow to the battery VCC-BAT and preventing the battery VCC-BAT from powering the clock chip U1, ensuring that the battery VCC-BAT has no leakage current. When the main power supply Vmain is de-energized, and the voltage of the supercapacitor C1 is lower than the voltage of the battery VCC-BAT, the diode D1 conducts, thereby enabling the battery VCC-BAT to power the clock chip U1. The voltage of the battery VCC-BAT is 3V, and the internal resistance of the battery VCC-BAT is 20mΩ.

[0036] When the main power supply Vmain is supplying power, the first charging circuit 100 transmits the current output by the main power supply Vmain to the clock chip U1. At the same time, the second charging circuit 200 transmits the current output by the main power supply Vmain to the supercapacitor C1 for charging. Since the voltage output by the main power supply Vmain is higher than the voltage of the supercapacitor C1 and the voltage of the battery VCC-BAT, the supercapacitor C1 and the battery VCC-BAT do not supply power to the clock chip U1 at this time.

[0037] When the main power supply Vmain is de-energized, the first charging circuit 100 and the second charging circuit 200 are in the off state, and the power supply mode of the clock chip U1 is switched to the supercapacitor C1 or the battery VCC-BAT. Specifically:

[0038] When the voltage of battery VCC-BAT is higher than the voltage of supercapacitor C1, diode D1 conducts, creating a circuit between battery VCC-BAT and clock chip U1, while creating an open circuit between supercapacitor C1 and clock chip U1. At this time, battery VCC-BAT supplies power to clock chip U1, while supercapacitor C1 does not supply power to clock chip U1.

[0039] When the voltage of battery VCC-BAT drops below the voltage of supercapacitor C1, diode D1 is turned off, and there is an open circuit between battery VCC-BAT and clock chip U1, while there is a closed circuit between supercapacitor C1 and clock chip U1. At this time, supercapacitor C1 supplies power to clock chip U1, and battery VCC-BAT does not supply power to clock chip U1.

[0040] When the voltage of supercapacitor C1 is equal to the voltage of battery VCC-BAT, since the internal resistance of supercapacitor C1 is lower than that of battery VCC-BAT, according to the current distribution principle, diode D1 is cut off, there is an open circuit between battery VCC-BAT and clock chip U1, and there is a closed circuit between supercapacitor C1 and clock chip U1. Supercapacitor C1 prioritizes powering clock chip U1, while battery VCC-BAT does not power clock chip U1.

[0041] When the main power supply Vmain resumes power supply, it supplies power to the clock chip U1 while continuing to charge the supercapacitor C1 through the second charging circuit 200. When the main power supply Vmain is de-energized again, the power supply process of the battery VCC-BAT and the supercapacitor C1 is repeated.

[0042] This application utilizes a supercapacitor C1 and a battery VCC-BAT to achieve automatic switching between them, forming a complementary power supply mechanism. The supercapacitor C1, with its low internal resistance, powers the clock chip U1 when its output voltage is higher than or equal to the battery VCC-BAT voltage. This reduces electrode passivation caused by deep discharge in the battery VCC-BAT, extending its lifespan and reducing its replacement frequency. Simultaneously, when the output voltage of the supercapacitor C1 is lower than the battery VCC-BAT voltage... When the voltage of C-BAT is low and the main power supply Vmain has not resumed power supply, it automatically switches to battery power supply VCC-BAT. With its high energy density, it provides a long-term stable static current for the clock chip U1, avoiding timing interruptions caused by the limited energy storage capacity of the supercapacitor C1, thus ensuring the continuity and accuracy of the clock chip U1's timing. At the same time, the supercapacitor C1 can be charged when the main power supply Vmain is supplying power normally, maintaining a good working condition, further improving the overall service life and reliability of the backup power supply, reducing maintenance costs, and extending the standby time of the clock chip U1.

[0043] In one possible implementation, the first charging circuit 100 includes a diode D4; the anode of the diode D4 is electrically connected to the output of the main power supply Vmain, and the cathode of the diode D4 is electrically connected to the VDD pin of the clock chip U1.

[0044] It should be noted here that diode D4 is used to limit the direction of current flow. Diode D4 uses its unidirectional conductivity to allow the current output by the main power supply Vmain to be transmitted in the direction of the clock chip U1 through the first charging circuit 100. This prevents the current output by the supercapacitor C1 or the battery VCC-BAT from flowing back to the main power supply Vmain through the first charging circuit 100 when the main power supply Vmain is powered off.

[0045] In one possible implementation, the second charging circuit 200 includes a diode D3; the anode of the diode D3 is electrically connected to the output of the main power supply Vmain, and the cathode of the diode D3 is electrically connected to the input of the supercapacitor C1 through a current-limiting resistor.

[0046] It should be noted that diode D3 is used to limit the direction of current flow. The design of diode D3 ensures that the current output from the main power supply Vmain is transmitted towards the supercapacitor C1 through the second charging circuit 200. This prevents the current output from the supercapacitor C1 from flowing back to the main power supply Vmain through the second charging circuit 200 when the main power supply Vmain is de-energized. The current transmitted by the second charging circuit 200 is delivered to the supercapacitor C1 through the current-limiting resistor R7. The current-limiting resistor R7 is used to control the charging or discharging current of the supercapacitor C1. By setting the current-limiting resistor R7, it is possible to prevent the supercapacitor C1 from being damaged by excessive current when the second charging circuit 200 is charging it. At the same time, the current-limiting resistor limits the instantaneous discharge current of the supercapacitor C1, preventing the supercapacitor C1 from experiencing a sudden voltage drop or internal overheating due to large current discharge. The resistance of the current-limiting resistor R7 is 1KΩ.

[0047] In one possible implementation, diode D2 is also included; the anode of diode D2 is electrically connected to the output terminal of supercapacitor C1 through a current-limiting resistor, and the cathode of diode D2 is electrically connected to the VDD pin of clock chip U1; and one end of supercapacitor C1 is grounded.

[0048] It should be noted here that the supercapacitor C1, current-limiting resistor R7, and diode D2 are connected in series. When the voltage of supercapacitor C1 is higher than that of battery VCC-BAT, the output current of supercapacitor C1 is transmitted to clock chip U1 through the current-limiting resistor and diode D2. Diode D2 is used to limit the current flow, thereby ensuring that the current output of supercapacitor C1 is transmitted in the direction of clock chip U1. This avoids the current output of battery VCC-BAT flowing back to supercapacitor C1 when the voltage at the output terminal of supercapacitor C1 is lower than that of battery VCC-BAT, which supplies power to clock chip U1 (i.e., prevents battery VCC-BAT from charging supercapacitor C1).

[0049] Furthermore, the design of diodes D2 and D1 forms a bidirectional isolation circuit. When the supercapacitor C1 is powered, diode D1 is cut off, and the battery VCC-BAT does not participate in the power supply of the clock chip U1. When the battery VCC-BAT is powered, diode D2 is cut off, and the supercapacitor C1 does not participate in the power supply of the clock chip U1. The setting of diodes D2 and D1 avoids power supply conflicts caused by current superposition during the switching process of the two backup power supplies, ensuring the reliability of the entire circuit after the main power supply Vmain is powered off.

[0050] In one possible implementation, diodes D1, D2, D3, and D4 are all diodes with a voltage drop of 0.3V.

[0051] In one possible implementation, a decoupling capacitor C3 is also included;

[0052] One end of the decoupling capacitor C3 is electrically connected to the anode of the diode D3 and the anode of the diode D4, respectively, and the other end of the decoupling capacitor C3 is grounded. The decoupling capacitor C3 is suitable for reducing the voltage fluctuation of the main power supply Vmain output, and ensuring that the voltage of the first charging circuit 100 and the second charging circuit 200 is more stable.

[0053] In one possible implementation, an oscillator Y1 is also included. The input of oscillator Y1 is connected to the OSCI pin of clock chip U1, and the output of oscillator Y1 is connected to the OSCO pin of clock chip U1. It should be noted that the input and output of oscillator Y1 form a closed-loop oscillation with the internal circuitry of clock chip U1 through the OSCI and OSCO pins, respectively, thus providing a precise time reference for clock chip U1. The external oscillator Y1 offers better frequency stability, thereby ensuring that the timing error of clock chip U1 is minimized.

[0054] Furthermore, the oscillator Y1 is a crystal oscillator with a frequency of 32.768kHz.

[0055] In one possible implementation, the VSS pin of clock chip U1 is grounded.

[0056] In one possible implementation, the battery VCC-BAT is a disposable button cell, preferably a CR2032 lithium manganese battery.

[0057] In one possible implementation, the clock chip U1 is a BLX8563-PARC chip.

[0058] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A RTC circuit compatible with both battery and supercapacitor, characterized in that, include: Clock chip, supercapacitor, battery, first charging circuit and second charging circuit; Both the input terminals of the first charging circuit and the input terminals of the second charging circuit are suitable for electrical connection to the output terminal of the main power supply. The output terminal of the first charging circuit is electrically connected to the VDD pin of the clock chip; The output terminal of the second charging circuit is electrically connected to the supercapacitor, and is suitable for supplying power to the supercapacitor simultaneously through the second charging circuit when the main power supply supplies power to the clock chip through the first charging circuit; The supercapacitor is electrically connected to the VDD pin of the clock chip, and is suitable for supplying power to the clock chip by the supercapacitor when the main power supply is off and the output voltage of the supercapacitor is higher than the output voltage of the battery; The battery is electrically connected to the VDD pin of the clock chip via diode D1, which is suitable for supplying power to the clock chip by the battery when the main power supply is turned off and the output voltage of the supercapacitor is lower than the battery voltage.

2. The RTC circuit compatible with a battery and a supercapacitor according to claim 1, characterized in that, The first charging circuit includes diode D4; The anode of diode D4 is electrically connected to the output terminal of the main power supply, and the cathode of diode D4 is electrically connected to the VDD pin of the clock chip.

3. The RTC circuit compatible with a battery and a supercapacitor according to claim 2, characterized in that, The second charging circuit includes diode D3; The anode of diode D3 is electrically connected to the output terminal of the main power supply, and the cathode of diode D3 is electrically connected to the input terminal of the supercapacitor through a current-limiting resistor.

4. The RTC circuit compatible with a battery and a supercapacitor according to claim 3, characterized in that, It also includes diode D2; The anode of diode D2 is electrically connected to the output terminal of the supercapacitor through the current-limiting resistor, and the cathode of diode D2 is electrically connected to the VDD pin of the clock chip; and one end of the supercapacitor is grounded.

5. The RTC circuit compatible with a battery and a supercapacitor according to claim 3, characterized in that, It also includes decoupling capacitors; One end of the decoupling capacitor is electrically connected to the anode of diode D3 and the anode of diode D4, respectively, and the other end of the decoupling capacitor is grounded.

6. The RTC circuit compatible with a battery and a supercapacitor according to claim 1, characterized in that, Also includes: Oscillator; The input terminal of the oscillator is electrically connected to the OSCI pin of the clock chip, and the output terminal of the oscillator is electrically connected to the OSCO pin of the clock chip.

7. The RTC circuit compatible with a battery and a supercapacitor according to claim 1, characterized in that, The VSS pin of the clock chip is grounded.

8. The RTC circuit compatible with a battery and a supercapacitor according to claim 1, characterized in that, The battery is a disposable button battery.

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