RTC circuit with super capacitor replacing button cell
By replacing lithium batteries with supercapacitors and combining with charging and discharging circuits, the liquid leakage or explosion problems caused by vibration and high temperature of lithium batteries in RTC circuits are solved, and stable operation and fast charging and discharging are achieved in a wide temperature range, which is suitable for frequent power outage scenarios.
Patent Information
- Application Number
- CN202510561634.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-30
- Publication Date
- 2025-08-01
AI Technical Summary
In the RTC clock circuit of the existing integrated information monitoring device of locomotives, lithium button batteries are prone to leakage or explosion due to locomotive vibration and high temperature, which affects normal use.
Supercapacitors are used to replace lithium batteries, and backup power is formed through charging circuits and discharge circuits. The supercapacitors are directly welded to the on-board firewall board, combining energy storage inductors, MOS tubes, resistors and diodes to achieve fast charging and discharge, supporting millisecond charging.
The supercapacitor works stably in a wide temperature range to avoid falling off due to vibration, support frequent power outage scenarios, realize fast charging and discharging, and ensure the normal operation of the RTC circuit.
Smart Images
Figure CN120414840A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of RTC circuits, and more particularly to an RTC circuit that replaces a button battery with a super capacitor. Background Art
[0002] RTC, that is, Real-Time Clock, is a hardware or software component that can continuously track the current time. Its main function is to provide an accurate time reference and maintain the continuity of time even when the device is powered off or enters the low-power mode.
[0003] In modern electronic devices, the RTC function plays a crucial role. Hardware RTCs are usually integrated in microcontrollers or dedicated chips, such as DS1307, PCF8563, etc. As Figure 1 and Figure 2 shown, the power supply of the RTC chip in the RTC circuit includes the main power supply and the backup power supply. When the main power supply is powered off or unavailable, the backup power supply is used to maintain the operation of the internal clock circuit of the chip and ensure that the clock does not stop. The backup power supply generally uses a non-rechargeable lithium button battery with a voltage of 3V.
[0004] The locomotive on-board integrated information monitoring device is an intelligent monitoring system integrated in railway locomotives / motor cars. Through multi-dimensional data collection, analysis, and transmission, it realizes real-time monitoring of the locomotive operation status, equipment performance, and environmental parameters, ensuring train operation safety and operation efficiency.
[0005] In the existing RTC clock circuit used on the firewall card of the locomotive on-board integrated information monitoring device, due to the relatively extreme locomotive operation environment, such as locomotive vibration (10 - 20g shock) and high temperature (local temperature in the motor compartment exceeds 80°C), it is easy for the non-rechargeable lithium button battery to leak liquid or explode, thus affecting its normal use.
[0006] Therefore, in this invention patent application, the applicant has carefully studied an RTC circuit that replaces a button battery with a super capacitor to solve the above problems. Summary of the Invention
[0007] Aiming at the deficiencies of the above-mentioned existing technologies, the main purpose of the present invention is to provide an RTC circuit that replaces a button battery with a super capacitor. It replaces the disposable lithium battery with a super capacitor EC1, can directly weld the super capacitor EC1 on the on-board firewall board card, avoiding falling off due to vibration and thus affecting its normal use. Moreover, the super capacitor EC1 can work stably in a wide temperature range (i.e., -40°C to 85°C), and the super capacitor EC1 can be quickly charged and discharged, supporting millisecond-level charging, suitable for frequent power-off scenarios. At the same time, the maximum charging of the super capacitor EC1 is achieved.
[0008] To achieve the above purpose, the present invention adopts the following technical solutions: An RTC circuit using a supercapacitor to replace a button battery, which is used for an in-vehicle firewall board, includes an RTC chip, a main power supply, and a backup power supply that are respectively connected to the RTC chip; The backup power supply includes a supercapacitor CE1, a charging circuit for charging the supercapacitor CE1, and a discharging circuit for discharging the supercapacitor CE1; The charging circuit includes a storage inductor PL1, a MOS transistor Q1, a resistor R1, a diode D1, a capacitor C2, and a resistor R3; One end of the storage inductor PL1 is used to connect to the P3V3 voltage terminal of the main power supply. The other end of the storage inductor PL1 and one end of the resistor R1 are commonly connected to the drain of the MOS transistor Q1. The source of the MOS transistor Q1 is grounded. The gate of the MOS transistor Q1 is used to connect to the PWM output pin of the MCU. The positive electrode of the diode D1 is connected to the other end of the resistor R1. The negative electrode of the diode D1 is connected to the positive electrode of the supercapacitor CE1, and the connection node of the two is the VCAP node. The VCAP node is grounded through the capacitor C2. The negative electrode of the supercapacitor CE1 is grounded. The VCAP node is connected to one end of the resistor R3, and the other end of the resistor R3 is used to connect to the voltage sampling pin of the MCU; The discharging circuit includes a resistor R2. One end of the resistor R2 is connected to the VCAP node, and the other end of the resistor R2 is connected to the RTC chip for power supply; When just powered on, if the MCU detects that the voltage sampling pin is lower than the first preset voltage value, it controls the PWM output pin to output a PWM signal to the MOS transistor Q1 to charge the storage inductor PL1 and the storage inductor PL1 to charge the supercapacitor CE1; During the charging process, when the MCU detects that the voltage sampling pin reaches the second preset voltage value, it controls the PWM output pin to stop outputting the PWM signal to the MOS transistor Q1 to stop charging the storage inductor PL1 and the storage inductor PL1 from charging the supercapacitor CE1.
[0009] As a preferred solution, the charging circuit further includes a capacitor C1, and one end of the storage inductor PL1 is also grounded through the capacitor C1.
[0010] As a preferred solution, the model of the RTC chip is DS1339U-33+, and its operating voltage range is 1.3V to 3.7V.
[0011] As a preferred solution, the specification of the supercapacitor CE1 is 3.8V / 10F.
[0012] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, on the one hand, a backup power supply formed by a charging circuit, a supercapacitor EC1, and a discharging circuit. The supercapacitor EC1 replaces the disposable lithium battery, and the supercapacitor EC1 can be directly welded on the in-vehicle firewall board, avoiding falling off due to vibration and thus affecting its normal use. Moreover, the supercapacitor EC1 can work stably in a wide temperature range (i.e., -40°C to 85°C). On the other hand, the supercapacitor EC1 can be charged and discharged quickly, supporting millisecond-level charging, which is suitable for scenarios with frequent power outages. In addition, the supercapacitor EC1 is charged to the maximum by boosting through the cooperation of a storage inductor PL1, a MOS transistor Q1, a resistor R1, and a diode D1. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The drawings are used to further illustrate the content of the present invention, form a part of the specification, and are used together with the following embodiments to explain the present invention, but should not constitute a limitation to the present invention. In the drawings: Figure 1 is a control principle block diagram of the prior art; Figure 2 is a partial circuit schematic diagram of the prior art (mainly showing the RTC chip and the backup power supply); Figure 3 is a control principle block diagram of an embodiment of the present invention; Figure 4 is a backup power supply circuit schematic diagram of an embodiment of the present invention.
[0014] Explanation of the reference numerals in the drawings: 11. RTC chip 12. Main power supply 13. Backup power supply 21. Charging circuit 22. Discharging circuit 23. MCU 13a. Backup power supply. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0015] The following details the specific embodiments of the present invention with reference to the drawings. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.
[0016] For the convenience of those skilled in the art to understand, the specific implementation process of the technical solutions in the present application is described through the following embodiments.
[0017] As Figure 3 and Figure 4As shown, an RTC circuit using a supercapacitor instead of a button battery is used for a vehicle-mounted firewall board, including an RTC chip 11 and a main power supply 12 and a backup power supply 13a respectively connected to the RTC chip 11.
[0018] like Figure 4 As shown, it shows the specific circuit structure of the RTC chip 11 of this embodiment. In this embodiment, the RTC chip 11 (such as Figure 4 The chip U15 shown is of model DS1339U-33+, and its operating voltage range is 1.3 V to 3.7 V. The main power supply 12 provides a P3V3_STBY voltage terminal to the RTC chip 11 .
[0019] The backup power supply 13a includes a supercapacitor CE1, a charging circuit 21 for charging the supercapacitor CE1, and a discharging circuit 22 for discharging the supercapacitor CE1. In this embodiment, the specification of the supercapacitor CE1 is 3.8V / 10F.
[0020] The charging circuit 21 includes an energy storage inductor PL1, a capacitor C1, a MOS transistor Q1, a resistor R1, a diode D1, a capacitor C2 and a resistor R3; the function of the diode D1 is to prevent the supercapacitor CE1 from discharging to the main power supply 12 after the main power supply 12 is cut off.
[0021] One end of the energy storage inductor PL1 is used to connect to the P3V3 voltage terminal of the main power supply 12, and one end of the energy storage inductor PL1 is also grounded through the capacitor C1. The other end of the energy storage inductor PL1 and one end of the resistor R1 are commonly connected to the drain of the MOS transistor Q1, the source of the MOS transistor Q1 is grounded, and the gate of the MOS transistor Q1 is used to connect to the PWM output pin of the MCU 23 (such as Figure 4 MCU_PWMCTL pin as shown).
[0022] The positive electrode of the diode D1 is connected to the other end of the resistor R1, the negative electrode of the diode D1 is connected to the positive electrode of the super capacitor CE1, and the connection node between the two is the VCAP node. The VCAP node is grounded through the capacitor C2, and the negative electrode of the super capacitor CE1 is grounded. The VCAP node is connected to one end of the resistor R3, and the other end of the resistor R3 is used to connect to the voltage sampling pin of the MCU 23 (such as Figure 4 MCU_ADCIN pin as shown).
[0023] The PWM output pin of MCU 23 outputs a PWM signal with a predetermined duty cycle. In this embodiment, the switching frequency of MOS transistor Q1 is determined by the PWM output frequency of MCU 23. Preferably, the PWM output frequency of MCU 23 is set to 1 to 5 MHz, and the PWM duty cycle of MCU 23 is set to 33% to 67%.
[0024] In this embodiment, the PWM signal is a series of high and low level combinations. When the PWM output pin of the MCU 23 outputs a high level to the gate of the MOS transistor Q1, the MOS transistor Q1 conducts when the gate of the MOS transistor Q1 is at a high level, that is, the drain and source of the MOS transistor Q1 conduct. The energy storage inductor PL1 is grounded, the diode D1 is cut off, and the P3V3 voltage terminal of the main power supply 12 charges the energy storage inductor PL1. The voltage across the energy storage inductor PL1 is 3.3V.
[0025] When the PWM output pin of the MCU 23 outputs a low level to the gate of the MOS transistor Q1, the MOS transistor Q1 does not conduct when the gate of the MOS transistor Q1 is at a low level. Because the energy storage inductor PL1 has been charged before, there will be current flowing through. The current always flows to the right. Since the current across the energy storage inductor PL1 cannot change suddenly, a voltage will be induced (this is understood as the energy storage inductor PL1 discharging), causing the diode D1 on the side to conduct, and then realizing the charging of the super capacitor CE1 and the capacitor C2.
[0026] When just powered on, if the MCU 23 detects that the voltage sampling pin is lower than the first preset voltage value, it controls the PWM output pin to output a PWM signal to the MOS transistor Q1 to charge the energy storage inductor PL1 and the energy storage inductor PL1 to charge the super capacitor CE1; in this embodiment, the first preset voltage value is the rated voltage value of the super capacitor CE1, that is, the first preset voltage value is 3.8V.
[0027] During the charging process, when the MCU 23 detects that the voltage sampling pin reaches the second preset voltage value, it controls the PWM output pin to stop outputting the PWM signal to the MOS transistor Q1 to stop charging the energy storage inductor PL1 and the energy storage inductor PL1 to charge the super capacitor CE1.
[0028] In this embodiment, the value of the second preset voltage value is related to the rated voltage value of the super capacitor CE1 and the maximum operating voltage value of the RTC chip 11.
[0029] When the rated voltage value of the super capacitor CE1 is greater than the maximum operating voltage value of the RTC chip 11, the second preset voltage value is the maximum operating voltage value of the RTC chip 11; for example, if a super capacitor CE1 with a rated voltage value of 5V is used, and since the maximum operating voltage value of the RTC chip 11 is 3.7V, at this time, the second preset voltage value is 3.7V. That is, during the charging process, when the MCU 23 detects that the voltage sampling pin reaches 3.7V, it controls the PWM output pin to stop outputting the PWM signal to the MOS transistor Q1 to stop charging the energy storage inductor PL1 and the energy storage inductor PL1 to charge the super capacitor CE1.
[0030] When the rated voltage value of the super capacitor CE1 is less than the maximum operating voltage value of the RTC chip 11, the second preset voltage value is the rated voltage value of the super capacitor CE1; for example, if a super capacitor CE1 with a rated voltage value of 3V is used, and since the maximum operating voltage value of the RTC chip 11 is 3.7V, at this time, the second preset voltage value is 3V. That is, during the charging process, when the MCU 23 detects that the voltage sampling pin reaches 3V, it controls the PWM output pin to stop outputting the PWM signal to the MOS transistor Q1 to stop charging the energy storage inductor PL1 and the energy storage inductor PL1 to charge the super capacitor CE1.
[0031] In this embodiment, the discharge circuit 22 includes a resistor R2. One end of the resistor R2 is connected to the VCAP node, and the other end of the resistor R2 is connected to the RTC chip 11 for power supply. When the main power supply 12 is powered off, the super capacitor CE1 discharges through the discharge circuit 22 to supply power to pin 3 of the RTC chip 11, that is, the super capacitor CE1 discharges through the resistor R2 to supply power to pin 3 of the RTC chip 11.
[0032] The design key point of the present invention is that it mainly forms a backup power supply through a charging circuit, a super capacitor EC1, and a discharge circuit. On the one hand, the super capacitor EC1 replaces the disposable lithium battery. The super capacitor EC1 can be directly soldered on the in-vehicle firewall board, avoiding falling off due to vibration and then affecting its normal use. Moreover, the super capacitor EC1 can work stably in a wide temperature range (i.e., -40°C to 85°C). On the other hand, the super capacitor EC1 can charge and discharge quickly, support millisecond-level charging, and is suitable for frequent power-off scenarios. Moreover, through the cooperation of the energy storage inductor PL1, the MOS transistor Q1, the resistor R1, and the diode D1, boost charging of the super capacitor EC1 is achieved, realizing the maximum charging of the super capacitor EC1.
[0033] The above is only a preferred embodiment of the present invention, and it does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.
Claims
1. An RTC circuit using a supercapacitor to replace a button battery, which is used for an in-vehicle firewall board, includes an RTC chip and a main power supply and a backup power supply that are respectively connected to the RTC chip; it is characterized in that: The backup power supply includes a supercapacitor CE1, a charging circuit for charging the supercapacitor CE1, and a discharging circuit for discharging the supercapacitor CE1; The charging circuit includes a storage inductor PL1, a MOS transistor Q1, a resistor R1, a diode D1, a capacitor C2, and a resistor R3; One end of the storage inductor PL1 is used to connect to the P3V3 voltage terminal of the main power supply. The other end of the storage inductor PL1 and one end of the resistor R1 are commonly connected to the drain of the MOS transistor Q1. The source of the MOS transistor Q1 is grounded. The gate of the MOS transistor Q1 is used to connect to the PWM output pin of the MCU. The positive electrode of the diode D1 is connected to the other end of the resistor R1. The negative electrode of the diode D1 is connected to the positive electrode of the supercapacitor CE1, and the connection node of the two is the VCAP node. The VCAP node is grounded through the capacitor C2. The negative electrode of the supercapacitor CE1 is grounded. The VCAP node is connected to one end of the resistor R3, and the other end of the resistor R3 is used to connect to the voltage sampling pin of the MCU; The discharging circuit includes a resistor R2. One end of the resistor R2 is connected to the VCAP node, and the other end of the resistor R2 is connected to the RTC chip for power supply; When just powered on, if the MCU detects that the voltage sampling pin is lower than the first preset voltage value, it controls the PWM output pin to output a PWM signal to the MOS transistor Q1 to charge the storage inductor PL1 and the storage inductor PL1 to charge the supercapacitor CE1; During the charging process, when the MCU detects that the voltage sampling pin reaches the second preset voltage value, it controls the PWM output pin to stop outputting the PWM signal to the MOS transistor Q1 to stop charging the storage inductor PL1 and the storage inductor PL1 from charging the supercapacitor CE1.
2. The RTC circuit with a supercapacitor replacing a button battery according to claim 1, characterized in that: The charging circuit further includes a capacitor C1, and one end of the storage inductor PL1 is also grounded through the capacitor C1.
3. The RTC circuit with supercapacitor replacing button battery according to claim 1, characterized in that: The model of the RTC chip is DS1339U-33+, and its operating voltage range is 1.3V to 3.7V.
4. The RTC circuit with supercapacitor replacing button battery according to claim 1, wherein: The specification of the supercapacitor CE1 is 3.8V / 10F.