Power management circuit for a real time clock

Abstract

The application provides a power management circuit of a real-time clock. The circuit comprises: a cathode of a first diode and a cathode of a second diode connected in parallel to a voltage input end of a real-time clock chip; a first voltage output end and a second voltage output end of a main power supply connected to an anode of the first diode and a voltage input end of a secondary power supply; a voltage output end of the secondary power supply and an anode of the second diode connected to a voltage monitoring pin of a voltage monitoring chip respectively; an I 2 C interface pin connected to an I 2 C interface pin of a host computer; an enable pin of the secondary power supply connected to a digital output pin of the host computer; an output voltage of the first voltage output end of the main power supply is greater than an output voltage of a charging battery; the main power supply supplies power to the voltage input end of the real-time clock chip through the first diode; a voltage difference between the voltage of the anode of the second diode and the voltage of the cathode of the second diode is less than a forward conduction voltage of the second diode; and the second diode is reverse-biased and cut off the charging battery.

Description

Technical Field

[0001] This application relates to electronic technology; specifically, it pertains to a power management circuit for a real-time clock. Background Technology

[0002] An RTC (Real-Time Clock) is an electronic circuit or integrated circuit (IC) specifically designed to continuously track time and date. Its core function is to act as a stand-alone timing system, maintaining accurate timekeeping even when the device's main power is off, relying on backup power (such as a battery).

[0003] In switching equipment, the Real-Time Circuit (RTC) plays a crucial role. Switches need to record all critical events (such as port status changes, traffic anomalies, configuration changes, security attacks, etc.). The RTC can provide a timestamp accurate to the millisecond level for each log entry, allowing engineers to locate the root cause of the problem through time clues during troubleshooting.

[0004] Currently, the real-time clock circuit structure of common switch devices is relatively simple. It provides a time base through a 32.768kHz crystal oscillator circuit and relies on seamless switching between dual power supplies to ensure continuous power supply to the RTC chip (in the dual power supply redundancy design, the main power supply is the power supply when the device is working normally, and the backup power supply is the battery power supply. The main and backup power supplies are isolated by Schottky diodes, and the battery power supply is automatically connected when the main power supply fails). This ensures that the RTC chip can keep time continuously. In this way, after the switch device is powered on again, the accurate time can be obtained by accessing the RTC chip, so as to ensure that all critical operations (port status changes, traffic anomalies, configuration changes) have accurate timestamps.

[0005] Although the above circuit has a simple structure, it has certain defects that may lead to reliability, lifespan, and accuracy issues. 1) Battery life does not meet expectations: Due to reverse leakage current in the diodes, or because the selected RTC chip is not a low-power type chip, a battery with an expected lifespan of 3-5 years may only last for about six months to a year. 2) Battery passivation leads to power switching failure: When lithium batteries are idle for a long time, a passivation film forms inside, which can cause a sudden drop in output voltage during switching, resulting in RTC power loss and affecting time synchronization when the device is powered on again. Utility Model Content

[0006] The purpose of this application is to provide a power management circuit for a real-time clock, which supplies power to the real-time clock through a power management circuit having a main power supply and a rechargeable battery.

[0007] To achieve the above objectives, this application provides a power management circuit for a real-time clock. The circuit includes: the cathodes of a first diode and a second diode connected in parallel to the voltage input terminal of a real-time clock chip; a first voltage output terminal of a main power supply connected to the anode of the first diode; a second voltage output terminal of the main power supply connected to the voltage input terminal of a secondary power supply; a voltage output terminal of the secondary power supply connected to the voltage input terminal of a rechargeable battery; and a voltage output terminal of the rechargeable battery connected to the anode of the second diode and a voltage monitoring pin of a voltage monitoring chip; the first I... 2 The C interface pin is connected to the second I of the host computer. 2 The C interface pins; the secondary power supply enable pin connects to the host computer's digital output pins; the output voltage of the main power supply's first voltage output terminal is greater than the rechargeable battery's output voltage; the main power supply supplies power to the real-time clock chip's voltage input terminal via the first diode; the voltage difference between the anode and cathode of the second diode is less than the second diode's forward conduction voltage, thus the second diode is reverse biased to cut off the rechargeable battery; the voltage monitoring chip acquires and records the rechargeable battery's output voltage; the host computer connects to the second I... 2 C interface connection I 2 If the C-bus access voltage monitoring chip records the output voltage of the rechargeable battery and determines that the recorded output voltage of the rechargeable battery is greater than the minimum input voltage of the real-time clock chip, then the host computer will not output a secondary power supply enable signal through the digital output pin, thus keeping the secondary power supply off. Attached Figure Description

[0008] Figure 1A and Figure 1B A connection diagram of the real-time clock management circuit provided in this application;

[0009] Figure 2 A schematic diagram of the main power supply for the real-time clock management circuit provided in the embodiments of this application;

[0010] Figure 3 A schematic diagram of the battery-powered real-time clock management circuit provided in the embodiments of this application;

[0011] Figure 4 A schematic diagram of the battery-powered real-time clock management circuit provided in the embodiments of this application. Detailed Implementation

[0012] The following detailed description will be provided with reference to several examples illustrated in the accompanying figures. In this detailed description, numerous specific details are used to provide a comprehensive understanding of the present application. Known methods, steps, components, and circuits are not described in detail in the examples to avoid obscuring their meaning.

[0013] In the terminology used, the term "including" means including but not limited to; the term "containing" means including but not limited to; the terms "above," "within," and "below" include the number itself; the terms "greater than" and "less than" mean not including the number itself. The term "based on" means based on at least a portion of them.

[0014] Figure 1A and Figure 1B A connection diagram of the real-time clock management circuit provided in this application.

[0015] Crystal oscillator 1 Crystal signal output pin ( Figure 1A , 1B (Not shown) Connected to the oscillation input terminal of the real-time clock (RTC) chip ( Figure 1A , 1B (Not shown), provides a clock reference signal for RTC chip 2.

[0016] The cathodes of diode D1 and D2 are connected in parallel to the voltage input terminal Vin21 of RTC chip 2.

[0017] The voltage output terminal Vout51 of the main power supply 5 is connected to the anode of diode D1; the voltage output terminal Vout52 of the main power supply 5 is connected to the voltage input terminal Vin61 of the secondary power supply 6.

[0018] The voltage output terminal Vout62 of the secondary power supply 6 is connected to the voltage input terminal Vin72 of the rechargeable battery 7.

[0019] The voltage output terminal Vout71 of the rechargeable battery 7 is connected to the anode of diode D2 and the voltage monitoring pin Mon41 of voltage monitoring chip 4.

[0020] Voltage monitoring chip 4's I 2 C interface 42 connects to the host computer 3's I 2 Interface C 31; the digital output pin GPIO32 of the host computer 3 is connected to the enable pin EN63 of the secondary power supply 6. The host computer 3's I... 2 The C bus signal line is connected to the I of RTC chip 2. 2 The C bus signal lines are electrically connected and used to transmit control commands and time data between them.

[0021] Figure 1B In this embodiment, the voltage output terminal Vout62 of the secondary power supply 6 is connected in series with the voltage input terminal Vin72 of the rechargeable battery 7 through an adjusting resistor R8. The value of the adjusting resistor R8 is not limited in this embodiment; it can be selected based on the constant current that needs to be adjusted between the secondary power supply 6 and the rechargeable battery 7.

[0022] Figure 2A schematic diagram of the main power supply for the real-time clock management circuit provided in the embodiments of this application;

[0023] When the communication equipment is working normally, the output voltage of the main power supply 5 is greater than the output voltage of the rechargeable battery.

[0024] In one example, the main power supply 5 outputs a voltage of 3.3V at its voltage output terminals Vout51 and Vout52, and the rechargeable battery 7 outputs a voltage of 3V at its voltage output terminal Vout71; the forward conduction voltage of diodes D1 and D2 is 0.7V.

[0025] The voltage at the anode of diode D1 is higher than the voltage at the cathode, so D1 is forward-biased. Assuming the main power supply is 3.3V, and since the forward voltage drop (Vf) of diode D1 is 0.7V, the actual input voltage of the main power supply to RTC chip 2 is approximately 3.3V - 0.7V = 2.6V.

[0026] The output voltage of rechargeable battery 7 is 3V, and the anode voltage of D2 is 3V. The cathode of D2 is connected in parallel with the cathode of D1, and the voltage of the cathode of D2 is 2.6V. The voltage difference between the anode voltage and the cathode voltage of D2 is 0.4V, which is less than the forward conduction voltage of D2. Therefore, D2 is reverse biased and cut off, isolating rechargeable battery 7.

[0027] Figure 3 A schematic diagram of the battery-powered real-time clock management circuit provided in the embodiments of this application;

[0028] When the main power supply 5 is turned off, the anode voltage of diode D1 is 0V.

[0029] The anode voltage of diode D2 is 3V output from rechargeable battery 7, and the forward voltage drop of diode D2 is 0.7V. The input voltage of rechargeable battery 7 to RTC chip 2 is approximately 3V - 0.7V = 2.3V.

[0030] The cathodes of diodes D2 and D1 are connected in parallel to RTC chip 2. The cathode voltage of diode D1 is 2.3V; the anode voltage of diode D1 is less than the cathode voltage, thus it is reverse-biased and cut off, preventing the current output from rechargeable battery 7 from flowing into main power supply 5. Rechargeable battery 7 supplies power to RTC chip 2.

[0031] Figure 4 A schematic diagram of a real-time clock management circuit for charging a rechargeable battery, provided in an embodiment of this application;

[0032] Main power supply 5 is working normally, according to Figure 2 The image shows the power supply for RTC chip 2.

[0033] As the rechargeable battery 7 discharges, the output voltage of the voltage output terminal Vout71 continuously decreases.

[0034] The voltage monitoring chip 4 acquires the Vout71 output voltage of the rechargeable battery 7 through the voltage monitoring pin 41 and records the acquired output voltage of the rechargeable battery 7.

[0035] Host computer 3 via I 2 C interface 31 connects to I 2 The C-bus access voltage monitoring chip 4 recorded the output voltage of the rechargeable battery 7 as 1.4V, and determined that the obtained output voltage of the rechargeable battery 7 was less than the minimum input voltage of the RTC chip 2, which was 1.5V; the host computer 3 output the secondary power enable signal En62 through the digital output pin GPIO32.

[0036] The secondary power supply 6 is enabled. The secondary power supply 6 receives the input voltage of 3.3V from the main power supply 5 through its voltage input terminal Vin61. The secondary power supply 6 converts the voltage of the rechargeable battery 7 to 3V through its internal charging circuit, and outputs it to the voltage input terminal Vin71 of the rechargeable battery 7 through the voltage output terminal Vout62 of the secondary power supply 6 to charge the rechargeable battery according to a constant output current.

[0037] If in Figure 1B In the process, the voltage output terminal Vout62 of the secondary power supply 6 is connected in series with the voltage input terminal Vin72 of the rechargeable battery 7 through the regulating resistor R8. The secondary power supply 6 is enabled by the enable signal received from the host computer 3 at EN 63. The secondary power supply 6 is enabled, and the voltage output terminal Vout 62 of the secondary power supply 6 outputs a constant output current corresponding to the regulating resistor R8 to charge the rechargeable battery 7.

[0038] When the rechargeable battery 7 is charged with constant current for a period of time, the voltage output of the voltage output terminal Vout71 of the rechargeable battery 7 gradually increases. The voltage monitoring chip 4 collects and records the output voltage of Vout71 of the rechargeable battery 7 through the voltage monitoring pin 41.

[0039] Host computer 3 via I 2 C interface 31 connects to I 2 The C bus is accessed, and the voltage monitoring chip 4 records the output voltage of rechargeable battery 7 as 3V, confirming that the output voltage of rechargeable battery 7 has returned to normal. The GPIO pin 32 of the host computer 3 no longer outputs the En enable signal to En63 of the secondary power supply 6, and the secondary power supply 6 stops working, ceasing to charge rechargeable battery 7. This completes one charging operation for rechargeable battery 7.

[0040] When the rechargeable battery 7 experiences abnormal discharge due to reasons such as a short circuit or internal passivation, its output voltage drops rapidly within a short period of time. Meanwhile, the leakage current in diode D2 causes the rechargeable battery 7 to discharge slowly.

[0041] The host computer 3 passes through I each time 2 C interface 31 connects to I 2 The C bus accesses the voltage monitoring chip 4 to obtain the output voltage of the rechargeable battery 7. The host computer 3 records the time when the obtained output voltage of the rechargeable battery 7 is less than the minimum input voltage of the RTC chip 2.

[0042] When the rechargeable battery 7 is abnormally discharged, the host computer 3 accesses the voltage monitoring chip 4 to obtain the time T1 when the output voltage of the rechargeable battery 7 is less than the minimum input voltage of the RTC chip 2.

[0043] The host computer 3 accesses the voltage monitoring chip 4 next to obtain the time T2 when the output voltage of the charging battery 7 is less than the minimum input voltage of the RTC chip 2.

[0044] The host computer 3 calculates that the time interval between T1 and T2 is significantly shorter than the battery charging cycle of the rechargeable battery 7 (for example, the voltage drop time of abnormal discharge of the rechargeable battery 7 is in days, while the normal charging cycle of the rechargeable battery 7 is in months or even years). The host computer 3 determines that the rechargeable button battery 7 is currently in an abnormal discharge state, and then uses the serial port ( Figures 2-4 (Not shown) Outputs a serial port alarm message for abnormal discharge of the rechargeable battery (not shown in the figure), notifying staff to check and replace the rechargeable battery 7.

[0045] In this application, a machine-readable storage medium can be any electronic, magnetic, optical, or other physical storage device used to store or contain information (such as executable instructions, data, etc.). For example, any machine-readable storage medium described herein can be any type of random access memory (RAM), volatile memory, non-volatile memory, flash memory, storage drive (such as a hard disk drive), solid-state drive, any type of optical disc (such as an optical disc, DVD, etc.), and similar devices, or combinations thereof. Furthermore, any machine-readable storage medium described herein can be a non-transitory machine-readable storage medium.

[0046] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A power management circuit for a real-time clock, characterized in that, The circuit includes, The cathodes of the first diode (D1) and the second diode (D2) are connected in parallel to the voltage input terminal of the real-time clock chip; The first voltage output terminal of the main power supply is connected to the anode of the first diode; the second voltage output terminal of the main power supply is connected to the voltage input terminal of the secondary power supply. The voltage output terminal of the secondary power supply is connected to the voltage input terminal of the rechargeable battery. The voltage output terminal of the rechargeable battery is connected to the anode of the second diode and the voltage monitoring pin of the voltage monitoring chip. The first I of the voltage monitoring chip 2 The C interface pin is connected to the second I of the host computer. 2 C interface pins; The enable pin of the secondary power supply is connected to the digital output pin of the host computer; The output voltage of the first voltage output terminal of the main power supply is greater than the output voltage of the rechargeable battery. The main power supply supplies power to the voltage input terminal of the real-time clock chip through the first diode. The voltage difference between the anode voltage and the cathode voltage of the second diode is less than the forward conduction voltage of the second diode. The second diode is reverse biased to cut off the rechargeable battery. The voltage monitoring chip acquires and records the output voltage of the rechargeable battery; The host computer accesses the second I 2 C interface connection I 2 If the C-bus accesses the voltage monitoring chip to record the output voltage of the rechargeable battery, and determines that the recorded output voltage of the rechargeable battery is greater than the minimum input voltage of the real-time clock chip, then the host computer will not output a secondary power supply enable signal through the digital output pin, thus keeping the secondary power supply off.

2. The circuit according to claim 1, characterized in that, The first and second voltage output terminals of the main power supply stop outputting. The voltage of the anode of the first diode is lower than the voltage of the cathode of the first diode. The first diode is reverse biased and cut off, preventing the current of the rechargeable battery from flowing back to the main power supply circuit. The voltage difference between the anode voltage and the cathode voltage of the second diode is greater than the forward conduction voltage of the second diode; the rechargeable battery supplies power to the real-time clock chip via the second diode.

3. The circuit according to claim 1, characterized in that, The host computer accesses the second I 2 C interface connection I 2 The C bus accesses the output voltage of the rechargeable battery recorded by the voltage monitoring chip and determines that the obtained output voltage of the rechargeable battery is less than the minimum input voltage of the real-time clock chip. The host computer outputs a secondary power enable signal to the secondary power supply through the digital output pin. When the secondary power supply is enabled, the input voltage received from the main power supply at the voltage input terminal of the secondary power supply is converted into the working voltage of the rechargeable battery through the charging circuit inside the secondary power supply, and then output to the voltage input terminal of the rechargeable battery through the voltage output terminal of the secondary power supply, so as to charge the rechargeable battery at a constant output current.

4. The circuit according to claim 1, characterized in that, The voltage output terminal of the secondary power supply is connected in series with the voltage input terminal of the rechargeable battery through an adjustable resistor. The host computer accesses the second I 2 C interface connection I 2 The C bus accesses the voltage monitoring chip to record the output voltage of the rechargeable battery, and determines that the output voltage of the rechargeable battery is greater than the minimum input voltage of the real-time clock chip; The host computer outputs a secondary power enable signal through the digital output pin; The secondary power supply receives the input voltage from the main power supply at its voltage input terminal, converts it into the working voltage of the rechargeable battery through the charging circuit inside the secondary power supply, and outputs it to the voltage input terminal of the rechargeable battery through the voltage output terminal of the secondary power supply. The secondary power supply charges the rechargeable battery according to the constant output current corresponding to the regulating resistor.

5. The circuit according to claim 3 or 4, characterized in that, The host computer accesses the second I 2 C interface connection I 2 The C-bus accesses the output voltage of the rechargeable battery recorded by the voltage monitoring chip to determine if the output voltage of the rechargeable battery has recovered. The host computer stops outputting the secondary power enable signal through the digital output pin. The secondary power supply was turned off.

6. The circuit according to claim 3 or 4, characterized in that, The host computer records the time when the output voltage of the rechargeable battery is less than the minimum input voltage.

7. The circuit according to claim 6, characterized in that... If the time interval between the current time when the output voltage of the rechargeable battery is less than the minimum input voltage and the previous time is less than the charging cycle of the rechargeable battery, the host computer will output an abnormal discharge alarm message for the rechargeable battery through the serial port.

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