RTC power supply circuit and electronic product

Abstract

An RTC power supply circuit is used for supplying power to an RTC circuit and comprises a charging circuit, a first power source and a second power source. The input end of the charging circuit is connected with an external power supply, the output end of the charging circuit is connected with the power supply end of the first power supply, and the charging circuit is used for charging the first power supply when the external power supply is connected; the power supply end of the first power supply is also connected with the power supply end of the RTC circuit, the first power supply has a first power supply capacity, and the first power supply capacity can supply power to the RTC circuit for a first duration; the power supply end of the second power supply is connected with the power supply end of the RTC circuit, the second power supply has a second power supply capacity, the second power supply capacity can supply power to the RTC circuit for a second duration, and the first duration is greater than the second duration. Power is supplied to the RTC circuit through the power supplies with different power supply durations, so that the power supply stability and the power supply continuity of the RTC circuit are ensured.

Description

Technical Field

[0001] This utility model relates to the field of power supply technology for electronic devices, specifically to an RTC power supply circuit and an electronic product. Background Technology

[0002] Currently, in areas with network coverage, the time information of portable communication electronic devices is synchronized and updated by a network time server. However, in areas without network coverage, the time information of portable communication electronic devices is recorded by the device itself, and time recording can only occur when the device's battery has power. If the device's battery is dead or being replaced, the time information may be reset, for example, when a mobile phone's time is reset. When the device's time is reset, the previously recorded time information is lost, causing significant inconvenience to users. For instance, when users need the device's time information to record information for application functions, such as recording the time of photos and videos, or recording the time of objects, these recording tasks cannot be completed after the device's time is suddenly reset, resulting in a poor user experience.

[0003] Therefore, how to provide a continuous and stable power supply to the RTC circuit in electronic products is an urgent problem to be solved. Utility Model Content

[0004] The main technical problem this invention addresses is how to provide a continuous and stable power supply to the RTC circuit in electronic products. 。

[0005] According to the first aspect, one embodiment provides an RTC power supply circuit for supplying power to an RTC circuit. The RTC power supply circuit includes a charging circuit, a first power supply, and a second power supply.

[0006] The input terminal of the charging circuit is used to connect to an external power source, and the output terminal of the charging circuit is connected to the power source terminal of the first power source. The charging circuit is used to charge the first power source when an external power source is connected.

[0007] The power supply terminal of the first power supply is also connected to the power supply terminal of the RTC circuit. The first power supply has a first power supply capacity, which is sufficient to supply power to the RTC circuit for a first duration.

[0008] The power supply terminal of the second power supply is connected to the power supply terminal of the RTC circuit. The second power supply has a second power supply capacity, which is able to supply power to the RTC circuit for a second duration, where the first duration is longer than the second duration.

[0009] In one embodiment, the RTC power supply circuit further includes: a step-down circuit and a first filter capacitor;

[0010] The input terminal of the step-down circuit is connected to the output terminal of the first power supply and grounded through the first filter capacitor. The output terminal of the step-down circuit is connected to the power supply terminal of the RTC circuit. The step-down circuit is used to step down the voltage output by the first power supply before outputting it.

[0011] In one embodiment, the RTC power supply circuit further includes: an isolation circuit;

[0012] The isolation circuit has a first terminal and a second terminal. The first terminal is connected to the output terminal of the step-down circuit, and the second terminal is connected to the power supply terminal of the RTC circuit and the power supply terminal of the second power supply, respectively. The isolation circuit is used to allow the current at its first terminal to flow unidirectionally to its second terminal. The first power supply is also used to supply power to the second power supply.

[0013] In one embodiment, the first power source includes: a positive filter capacitor and a first battery;

[0014] The positive terminal of the first battery is connected to one end of the positive filter capacitor, and the other end of the positive filter capacitor is grounded.

[0015] In one embodiment, the first power supply further includes: a surge protection diode;

[0016] The positive terminal of the first battery is connected to one end of a surge protection diode, and the other end of the surge protection diode is grounded; the surge protection diode is connected in parallel with the positive filter capacitor.

[0017] In one embodiment, the second power source includes: a current-limiting resistor and a second battery; one end of the current-limiting resistor is connected in parallel with the power supply terminal of the RTC circuit and connected to the second terminal of the isolation circuit, the other end of the current-limiting resistor is connected to the positive terminal of the second battery, and the negative terminal of the second battery is grounded.

[0018] In one embodiment, the RTC power supply circuit further includes: a second filter capacitor;

[0019] The output of the step-down circuit is also connected in parallel with the first terminal of the isolation circuit to one end of the second filter capacitor, and the other end of the second filter capacitor is grounded.

[0020] In one embodiment, the RTC power supply circuit further includes: a third filter capacitor;

[0021] The second terminal of the isolation circuit is connected in parallel with the current-limiting resistor, and then connected in parallel with the power supply terminal of the RTC circuit to one end of the third filter capacitor, while the other end of the third filter capacitor is grounded.

[0022] In one embodiment, the first battery is used to power the RTC circuit; or, the second battery is used to power the RTC circuit.

[0023] According to a second aspect, one embodiment provides an electronic product including an RTC circuit and an RTC power supply circuit, the RTC power supply circuit being used to supply power to the RTC circuit.

[0024] According to the RTC power supply circuit of the above embodiment, the RTC power supply circuit is equipped with a first power supply with a relatively short power supply duration and a second power supply with a relatively long power supply duration. Both the first and second power supplies can supply power to the RTC clock circuit at the chip level. When the RTC circuit requires a long-term power supply, the first battery of the first power supply can provide a continuous and stable power supply to the RTC circuit. When the first battery is being replaced, the second battery of the second power supply can provide a short-term, continuous, and stable power supply to the RTC circuit. In this way, by providing targeted power to the RTC circuit with power supplies of different durations, the stability and continuity of the RTC circuit's power supply can be ensured, reducing clock frequency errors and voltage fluctuations. Attached Figure Description

[0025] Figure 1 This embodiment provides a circuit structure diagram of an RTC power supply circuit;

[0026] Figure 2 This is a structural block diagram of an RTC power supply circuit provided in this embodiment.

[0027] Reference numerals: charging circuit 110, first power supply 120, second power supply 130, RTC circuit 140, step-down circuit 150, isolation circuit 160. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted or replaced by other elements or materials in different situations. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0029] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. Similarly, the steps or actions in the circuit description can be rearranged or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0030] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0031] Currently, in areas with network coverage, the time information of portable communication electronic devices is synchronized and updated by a network time server. However, in areas without network coverage, the time information of portable communication electronic devices is recorded by the device itself, and time recording can only occur when the device's battery has power. If the device's battery is dead or being replaced, the time information may be reset, for example, when a mobile phone's time is reset. When the device's time is reset, the previously recorded time information is lost, causing significant inconvenience to users. For instance, when users need the device's time information to record information for application functions, such as recording the time of photos and videos, or recording the time of objects, these recording tasks cannot be completed after the device's time is suddenly reset, resulting in a poor user experience.

[0032] Currently, electronic devices' clocks are continuously powered by individual button batteries or capacitors, thus reducing the occurrence of time resets. However, the power supply duration of button batteries or capacitors to electronic device clocks is limited, the supply voltage is unstable, and it can also cause significant clock frequency errors.

[0033] To address the aforementioned issues, this application proposes an RTC power supply circuit. This circuit includes a second power supply with a shorter power duration and a first power supply with a longer power duration. Both the first and second power supplies can power the RTC circuit at the chip level. When the RTC circuit requires prolonged power, it can be continuously and stably powered by the first battery of the first power supply. During the interval between replacing the first battery, the RTC circuit can be briefly and continuously powered by the second battery of the second power supply. Thus, by providing targeted power to the RTC circuit with power supplies of varying durations, the stability and continuity of the RTC circuit's power supply can be ensured, reducing clock frequency errors and voltage fluctuations. The following embodiments will illustrate this in detail. These embodiments use electronic devices as examples.

[0034] Please refer to Figure 1 , Figure 1 This is a circuit structure diagram of an RTC power supply circuit provided in this embodiment, as shown below. Figure 1 As shown, the RTC power supply circuit is used to power the RTC circuit. The RTC power supply circuit includes a charging circuit 110, a first power supply 120, and a second power supply 130. The input terminal of the charging circuit 110 is used to connect to an external power supply VCHG, and the output terminal of the charging circuit 110 is connected to the power supply terminal of the first power supply 120. The charging circuit 110 is used to charge the first power supply 120 when the external power supply VCHG is connected. The power supply terminal of the first power supply 120 is also connected to the power supply terminal of the RTC circuit 140. The first power supply 120 has a first power supply capacity, which is sufficient to power the RTC circuit 140 for a first duration. The power supply terminal of the second power supply 130 is connected to the power supply terminal of the RTC circuit 140. The second power supply 130 has a second power supply capacity, which is sufficient to power the RTC circuit 140 for a second duration, where the first duration is longer than the second duration.

[0035] In practical applications, when the external power supply VCHG has a charging voltage, the external power supply VCHG will charge the first power supply 120. The first power supply 120 will supply power to the RTC circuit 140 (RTC clock circuit) through the isolation circuit 160. After the RTC circuit 140 works, it will save the recorded time information.

[0036] In practical applications, during the interval when the user replaces the first power supply 120, the second power supply 130 will continuously supply power to the RTC circuit 140, thereby ensuring that the time information of the electronic device can be continuously recorded.

[0037] In one embodiment, the RTC power supply circuit further includes: a step-down circuit 150 and a first filter capacitor C1; the input terminal of the step-down circuit 150 is connected to the output terminal of the first power supply 120 and grounded through the first filter capacitor C1, and the output terminal of the step-down circuit 150 is connected to the power supply terminal of the RTC circuit 140; the step-down circuit 150 is used to step down the voltage output by the first power supply 120 before outputting it.

[0038] It should be noted that the supply voltage required by the RTC circuit 140 is relatively small. When the external power supply VCHG charges the first power supply 120, the voltage of the first power supply 120 may be much higher than the supply voltage required by the RTC circuit 140. At this time, the voltage output by the first power supply 120 can be stepped down by the step-down circuit 150 so that the first power supply 120 can output a supply voltage suitable for the RTC circuit 140.

[0039] It should be noted that the step-down circuit 150 includes, but is not limited to, an LDO (Low Dropout Regulator).

[0040] In one embodiment, the RTC power supply circuit further includes an isolation circuit 160; the isolation circuit 160 has a first terminal and a second terminal, the first terminal is connected to the output terminal of the step-down circuit 150, and the second terminal is connected to the power supply terminal of the RTC circuit 140 and the power supply terminal of the second power supply 130 respectively, and the isolation circuit 160 is used to unidirectionally transfer the current of its first terminal to its second terminal; wherein, the first power supply 120 is also used to supply power to the second power supply 130.

[0041] It should be noted that the isolation circuit 160 can be an electrical component with unidirectional conductivity, such as a diode. The function of this isolation circuit 160 is to prevent the fully charged second battery T1 from charging the first battery J1, because if the second battery T1 were to charge the first battery J1, it would instantly deplete the charge of the second battery T1. Another function of this isolation circuit 160 is to allow the first battery J1 to charge the second battery T1, thereby ensuring that the second battery T1 is in a charged state.

[0042] In one embodiment, the first power supply 120 includes: a positive filter capacitor C2 and a first battery J1; the positive terminal of the first battery J1 is connected to one end of the positive filter capacitor C2, and the other end of the positive filter capacitor C2 is grounded.

[0043] It should be noted that when the load in the RTC circuit changes, such as a sudden increase or decrease in load current, the output voltage of the first battery J1 will fluctuate. In this case, the positive filter capacitor C2 can quickly provide or absorb charge to maintain a stable output voltage. Specifically, when the load current increases, the output voltage of the first battery J1 tends to decrease. At this time, the positive filter capacitor C2 will release its stored charge to replenish the circuit and prevent excessive voltage drop. When the load current decreases, the output voltage of the first battery J1 will increase, and the positive filter capacitor C2 will absorb excess charge to prevent the voltage from rising too high.

[0044] It should be noted that the first battery J1 is a rechargeable energy battery. For example, it can be a lithium battery, a solid polymer electrolyte lithium-ion battery, or a gel polymer electrolyte lithium-ion battery. This application does not impose any limitations on this.

[0045] In one embodiment, the first power supply 120 further includes: a surge protection diode D1; the positive terminal of the first battery J1 is connected to one end of the surge protection diode D1, and the other end of the surge protection diode D1 is grounded; the surge protection diode D1 is connected in parallel with the positive filter capacitor C2.

[0046] It should be noted that when the normal operating voltage in the RTC power supply circuit is lower than its breakdown voltage, the surge protection diode D1 exhibits a high-resistance state and is almost non-conductive, having no impact on the circuit. However, when a surge voltage occurs and its value exceeds the breakdown voltage of the surge protection diode D1, the diode quickly transitions from a high-resistance state to a low-resistance state, clamping the surge voltage to a relatively safe voltage level, thereby protecting the downstream circuitry. In other words, when the instantaneous peak value of the charging voltage of the RTC circuit 140 is unstable, the surge protection diode D1 adjusts the generated surge voltage to a stable voltage, providing a stable power supply voltage to the RTC circuit 140.

[0047] In one embodiment, the second power supply 130 includes: a current-limiting resistor R1 and a second battery T1; one end of the current-limiting resistor R1 is connected in parallel with the power supply terminal of the RTC circuit 140 and connected to the second terminal of the isolation circuit 160, the other end of the current-limiting resistor R1 is connected to the positive terminal of the second battery T1, and the negative terminal of the second battery T1 is grounded.

[0048] It should be noted that the voltage of the second power supply 130 may fluctuate, which may cause changes in the current in the RTC power supply circuit. The current-limiting resistor R1 can reduce the impact of these changes on the circuit to a certain extent. That is, the current-limiting resistor R1 will share part of the voltage, limit the excessive increase of current, thereby reducing the fluctuation of the output voltage and improving the stability of the circuit.

[0049] In one embodiment, the RTC power supply circuit further includes: a second filter capacitor C3; the output terminal of the step-down circuit 150 is also connected in parallel with the first terminal of the isolation circuit 160 to one end of the second filter capacitor C3, and the other end of the second filter capacitor C3 is grounded.

[0050] It should be noted that the second filter capacitor C3 is mainly used to filter out high-frequency noise and interference signals in the circuit, thereby improving the signal-to-noise ratio of the circuit; at the same time, it can also be used as a decoupling capacitor to isolate mutual interference between different circuit stages and ensure that each circuit stage operates independently and stably.

[0051] In one embodiment, the RTC power supply circuit further includes: a third filter capacitor C4; the second terminal of the isolation circuit 160 is connected in parallel with the current limiting resistor R1, and then connected in parallel with the power supply terminal of the RTC circuit 140 to one end of the third filter capacitor C4, and the other end of the third filter capacitor C4 is grounded.

[0052] It should be noted that the third filter capacitor C4 is mainly used to store electrical energy and provide temporary energy support to the RTC circuit 140 when the first power supply 120 and the second power supply 130 are momentarily powered off or the voltage drops.

[0053] In one embodiment, the first battery is used to power the RTC circuit; or, the second battery is used to power the RTC circuit.

[0054] It should be noted that the first battery J1 is mainly used to power the RTC circuit 140 for extended periods, while the second battery T1 is mainly used to power the RTC circuit 140 for short periods. This is because the first battery J1 has a much greater energy capacity than the second battery T1. When the electronic device is in an area without network coverage, the first battery J1 powers the RTC circuit 140, ensuring uninterrupted time information. When the first battery J1 malfunctions or needs to be replaced, the second battery T1 powers the RTC circuit 140 to maintain uninterrupted time information. When the first battery J1 is functioning normally, it can continue to power the RTC circuit 140.

[0055] It should be noted that when the electronic device is powered off, or when the power supply current provided by the second battery T1 to the RTC circuit 140 decreases, the first battery J1 supplies power to the RTC circuit 140.

[0056] It should be noted that when the RTC circuit 140 requires a relatively large supply current, the RTC circuit 140 is powered by both the first battery J1 and the second battery T1.

[0057] In practical applications, when the power supply current required by the RTC circuit 140 is relatively stable, it can be powered by the first battery J1 alone without the need for the second battery T1, or the second battery T1 can be removed to save costs.

[0058] like Figure 1 As shown, the charging circuit 110 includes a charging IC U2. The charging IC U2 is connected to a filter capacitor C5 through pin 1, and the other end of the filter capacitor C5 is grounded. The charging IC U2 is connected to a resistor R3 through pin 4, and the other end of the resistor R3 is grounded. The charging IC U2 is connected to an adjustment resistor R4 through pin 6. The charging IC U2 is connected to an adjustment resistor R5 through pin 7. The adjustment resistors R4 and R5 are connected in parallel and then grounded. The charging IC U2 is connected to the first end of a resistor R6 through pin 3. The second end of the resistor R6 is connected to VCC through a pull-up resistor R7. The third end of the resistor R6 is connected to OUT_EN, and the other end of OUT_EN is connected to the CPU. The first power supply 120 and the step-down circuit 150 are connected in parallel and then connected in parallel with pin 8 of the charging IC U2 to one end of the filter capacitor C6. The other end of the filter capacitor C6 is grounded.

[0059] like Figure 1 As shown, pin 1 of the first battery J1 is the positive terminal, used to connect to pin 8 of the charging IC U2 of the charging circuit 110. Pins 2 and 3 of the first battery J1 are the negative terminals. The first battery J1 is connected to one end of the first filter capacitor C1 through pin 1 and pins 3 and 4 of the step-down circuit 150, and the other end of the first filter capacitor C1 is grounded. Pin 1 of the charging circuit 110 and the first end of the isolation circuit 160 are connected to one end of the second filter capacitor C3, and the other end of the second filter capacitor C3 is grounded.

[0060] like Figure 1 As shown, pin M8 of the RTC terminal of RTC circuit 140 is the RTC power supply pin inside the CPU. Pins F10, G12, and M7 of RTC circuit 140 are the CPU clock output pins, used to output clock signals.

[0061] like Figure 1 As shown, the first battery J1 receives the power supply current through pin 4 of the step-down circuit 150 and outputs the power supply current to pin M8 of the RTC circuit 140 through pin 1.

[0062] like Figure 1 As shown, the second battery T1 supplies power to the RTC circuit 140 through pin M8.

[0063] Using a mobile phone as an example: After inserting the first battery J1 and the second battery T1 into the phone, press the power button. The phone's system will then boot up according to the normal boot process. When the phone is in an area without network access, the phone first powers the RTC circuit 140 through the first battery J1. When the first battery J1 needs to be replaced, the second battery T1 powers the RTC circuit 140. After the first battery J1 is replaced, it can continue to power the RTC circuit 140. If the RTC circuit 140 requires a large current, both the first battery J1 and the second battery T1 can power it simultaneously. This ensures the stability and continuity of the power supply to the RTC circuit 140, reducing clock frequency errors and voltage fluctuations.

[0064] This application provides an RTC power supply circuit for powering an RTC circuit. The RTC power supply circuit includes a charging circuit, a first power supply, and a second power supply. The input terminal of the charging circuit is connected to an external power supply, and the output terminal of the charging circuit is connected to the power supply terminal of the first power supply. The charging circuit charges the first power supply when an external power supply is connected. The power supply terminal of the first power supply is also connected to the power supply terminal of the RTC circuit. The first power supply has a first power supply capacity capable of supplying power to the RTC circuit for a first duration. The power supply terminal of the second power supply is connected to the power supply terminal of the RTC circuit. The second power supply has a second power supply capacity capable of supplying power to the RTC circuit for a second duration, where the first duration is longer than the second duration. This RTC power supply circuit provides a first power supply with a relatively short power supply duration and a second power supply with a relatively long power supply duration. Both the first and second power supplies can power the RTC clock circuit on the chip side. When the RTC circuit requires long-term power supply, the first battery of the first power supply can provide continuous and stable power to the RTC circuit. During the interval between replacing the first battery, the second battery of the second power supply can provide short-term continuous and stable power to the RTC circuit. In this way, by supplying power to the RTC circuit with power supplies of different durations, the stability and continuity of the power supply to the RTC circuit can be ensured, reducing clock frequency errors and voltage fluctuations.

[0065] Please refer to Figure 2 , Figure 2 This is a structural block diagram of an RTC power supply circuit provided in this embodiment, as follows: Figure 2 As shown, the RTC power supply circuit includes a charging circuit 110, a first power supply 120 and a second power supply 130, an RTC circuit 140, a step-down circuit 150 and an isolation circuit 160.

[0066] It should be noted that the input terminal of the charging circuit 110 is used to connect to an external power source, and the output terminal of the charging circuit 110 is connected to the power source terminal of the first power source 120. The charging circuit 110 is used to charge the first power source 120 when an external power source is connected.

[0067] It should be noted that the power supply terminal of the first power supply 120 is also connected to the power supply terminal of the RTC circuit 140. The first power supply 120 has a first power supply capacity, which is sufficient to supply power to the RTC circuit 140 for a first duration. The first power supply 120 is also used to supply power to the second power supply 130.

[0068] It should be noted that the power supply terminal of the second power supply 130 is connected to the power supply terminal of the RTC circuit 140. The second power supply 130 has a second power supply capacity, which can supply power to the RTC circuit 140 for a second duration, where the first duration is longer than the second duration.

[0069] It should be noted that the input terminal of the step-down circuit 150 is connected to the output terminal of the first power supply 120, and the output terminal of the step-down circuit 150 is connected to the power supply terminal of the RTC circuit 140; the step-down circuit 150 is used to step down the voltage output by the first power supply 120 before outputting it.

[0070] It should be noted that the isolation circuit 160 has a first terminal and a second terminal. The first terminal is connected to the output terminal of the step-down circuit 150, and the second terminal is connected to the power supply terminal of the RTC circuit 140 and the power supply terminal of the second power supply 130, respectively. The isolation circuit 160 is used to unidirectionally transfer the current from its first terminal to its second terminal.

[0071] This application provides an RTC power supply circuit for powering an RTC circuit. The RTC power supply circuit includes a charging circuit, a first power supply, and a second power supply. The input terminal of the charging circuit is connected to an external power supply, and the output terminal of the charging circuit is connected to the power supply terminal of the first power supply. The charging circuit charges the first power supply when an external power supply is connected. The power supply terminal of the first power supply is also connected to the power supply terminal of the RTC circuit. The first power supply has a first power supply capacity capable of supplying power to the RTC circuit for a first duration. The power supply terminal of the second power supply is connected to the power supply terminal of the RTC circuit. The second power supply has a second power supply capacity capable of supplying power to the RTC circuit for a second duration, where the first duration is longer than the second duration. This RTC power supply circuit provides a first power supply with a relatively short power supply duration and a second power supply with a relatively long power supply duration. Both the first and second power supplies can power the RTC clock circuit on the chip side. When the RTC circuit requires long-term power supply, the first battery of the first power supply can provide continuous and stable power to the RTC circuit. During the interval between replacing the first battery, the second battery of the second power supply can provide short-term continuous and stable power to the RTC circuit. In this way, by supplying power to the RTC circuit with power supplies of different durations, the stability and continuity of the power supply to the RTC circuit can be ensured, reducing clock frequency errors and voltage fluctuations.

[0072] The above-described specific examples are for illustrative purposes only and are not intended to limit the scope of this invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the concept of this invention.

Claims

1. An RTC power supply circuit, used to supply power to an RTC circuit, characterized in that, The RTC power supply circuit includes a charging circuit, a first power supply, and a second power supply. The input terminal of the charging circuit is used to connect to an external power source, and the output terminal of the charging circuit is connected to the power source terminal of the first power source. The charging circuit is used to charge the first power source when the external power source is connected. The power supply terminal of the first power supply is also connected to the power supply terminal of the RTC circuit. The first power supply has a first power supply capacity, which is capable of supplying power to the RTC circuit for a first duration. The power supply terminal of the second power supply is connected to the power supply terminal of the RTC circuit. The second power supply has a second power supply capacity, which is capable of supplying power to the RTC circuit for a second duration, wherein the first duration is longer than the second duration.

2. The RTC power supply circuit as described in claim 1, characterized in that, The RTC power supply circuit also includes: a step-down circuit and a first filter capacitor; The input terminal of the step-down circuit is connected to the output terminal of the first power supply and grounded through the first filter capacitor. The output terminal of the step-down circuit is connected to the power supply terminal of the RTC circuit. The step-down circuit is used to step down the voltage output by the first power supply before outputting it.

3. The RTC power supply circuit as described in claim 2, characterized in that, The RTC power supply circuit also includes: an isolation circuit; The isolation circuit has a first terminal and a second terminal. The first terminal is connected to the output terminal of the step-down circuit, and the second terminal is connected to the power supply terminal of the RTC circuit and the power supply terminal of the second power supply, respectively. The isolation circuit is used to allow the current at its first terminal to flow unidirectionally to its second terminal. The first power supply is also used to supply power to the second power supply.

4. The RTC power supply circuit as described in claim 3, characterized in that, The first power source includes: a positive filter capacitor and a first battery; The positive terminal of the first battery is connected to one end of the positive filter capacitor, and the other end of the positive filter capacitor is grounded.

5. The RTC power supply circuit as described in claim 4, characterized in that, The first power supply also includes: a surge protection diode; The positive terminal of the first battery is connected to one end of the surge protection diode, and the other end of the surge protection diode is grounded; the surge protection diode is connected in parallel with the positive filter capacitor.

6. The RTC power supply circuit as described in claim 4, characterized in that, The second power source includes a current-limiting resistor and a second battery; one end of the current-limiting resistor is connected in parallel with the power supply terminal of the RTC circuit to the second terminal of the isolation circuit, and the other end of the current-limiting resistor is connected to the positive terminal of the second battery, and the negative terminal of the second battery is grounded.

7. The RTC power supply circuit as described in claim 6, characterized in that, The RTC power supply circuit also includes: a second filter capacitor; The output terminal of the step-down circuit is also connected in parallel with the first terminal of the isolation circuit to one end of the second filter capacitor, and the other end of the second filter capacitor is grounded.

8. The RTC power supply circuit as described in claim 7, characterized in that, The RTC power supply circuit also includes: a third filter capacitor; The second terminal of the isolation circuit is connected in parallel with the current-limiting resistor, and then connected in parallel with the power supply terminal of the RTC circuit to one end of the third filter capacitor, while the other end of the third filter capacitor is grounded.

9. The RTC power supply circuit as described in claim 7 or 8, characterized in that, The first battery is used to power the RTC circuit; or, the second battery is used to power the RTC circuit.

10. An electronic product, characterized in that, The electronic product includes an RTC circuit and an RTC power supply circuit as described in any one of claims 1 to 9, wherein the RTC power supply circuit is used to supply power to the RTC circuit.

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