Rechargeable real-time clock device and network camera

Abstract

The utility model relates to a rechargeable real-time clock device and a network camera. The rechargeable real-time clock device comprises a power supply switching unit, a battery unit and a real-time clock unit, the power supply switching unit comprises a first transistor; an external power supply is connected with the battery unit and the real-time clock unit through the first transistor so as to supply power to the battery unit and the real-time clock unit when the first transistor is switched on; the battery unit is further connected with the real-time clock unit and used for supplying power to the real-time clock unit when the first transistor is cut off, the problem that the battery is overcharged or not fully charged is solved, the service life of the battery is prolonged, reverse leakage current is very small when an external power source is powered down, and the power-down maintaining time is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power supply circuit, in particular to a rechargeable real-time clock device and network camera. BACKGROUND

[0002] In modern electronic devices, real-time clock (RTC) circuits play a crucial role. They not only provide accurate time and date information, but also are widely used in data recording, event timestamping, power management, timing tasks, and alarm clock functions. Among them, rechargeable RTC circuits have become important components in many electronic systems due to their unique performance and practicality. Rechargeable RTC circuits enable the provision of stable operating voltage to the RTC chip when the main power of the terminal device is normal, allowing the device to start normally, while also supplementing the backup battery with energy. When the main power is disconnected, the backup battery can discharge alone to maintain the operation of the RTC chip.

[0003] In the prior art, the switching between external power supply and backup battery is achieved through the unidirectional conduction of diodes, as shown in FIG. 1. When there is an external power supply input, the diode of the battery-to-RTC chip supply path VRTC is cut off, the diode of the +3.3V-to- VRTC path is turned on, and VRTC charges the battery through R7. The limit charging voltage of the rechargeable battery BT2 is 3.1V, so the resistors R5 and R6 are used to obtain 3.1V through voltage division. Figure 1

[0004] However, the above-mentioned circuit has the following problems: (1) battery overcharging or inability to fully charge: because the forward voltage drop Vf of the diode is related to current and temperature, if a general diode is used, Vf will change with current and temperature, ranging from 0.2V to 0.7V, resulting in the problem of battery not being able to fully charge. If the R5, R6 voltage division value is forcibly increased, the problem of overcharging will occur. (2) Battery leakage problem: if D2 is a low-dropout Schottky diode, due to the low-dropout characteristic of Schottky, Vf varies in the range of 0.1-0.3V, which can solve the problem of overcharging or inability to fully charge to some extent, but the leakage current of the Schottky diode is much larger than that of the ordinary diode, which will cause the problem of reverse leakage of the RTC battery through the diode after the external power supply is powered off. Invention content

[0005] In this embodiment, a rechargeable real-time clock device and network camera are provided to solve the problem of unreliable charging and discharging performance in related technologies.

[0006] ​In a first aspect, a chargeable real-time clock device is provided in the embodiments. The device comprises a power supply switching unit, a battery unit and a real-time clock unit. The power supply switching unit comprises a first transistor.

[0007] An external power source is connected to the battery unit and the real-time clock unit through the first transistor, so as to supply power to the battery unit and the real-time clock unit when the first transistor is turned on.

[0008] The battery unit is also connected to the real-time clock unit, for supplying power to the real-time clock unit when the first transistor is turned off.

[0009] In the embodiments, the stability and reliability of charging and discharging are improved by replacing the diode with the first transistor.

[0010] In some of the embodiments, the device further comprises a voltage comparison circuit and a switch control circuit.

[0011] One end of the voltage comparison circuit is connected to the external power source, and the other end of the voltage comparison circuit is connected to the first transistor through the switch control circuit.

[0012] The switch control circuit is configured to control the first transistor to be turned on according to the output of the voltage comparison circuit.

[0013] In the embodiments, the voltage comparison circuit improves the sensing ability to the change of the external power source, thereby improving the reliability of the charging and discharging switching.

[0014] In some of the embodiments, the voltage comparison circuit comprises a reset chip, and a reset signal output end of the reset chip is connected to the switch control circuit.

[0015] In the embodiments, the reset chip improves the efficiency of the charging and discharging switching, and the reset chip provided by the system is used without additional circuit structure.

[0016] In some of the embodiments, the voltage comparison circuit further comprises a first resistor, and the reset signal output end of the reset chip is grounded through the first resistor.

[0017] In some of the embodiments, the switch control circuit comprises a second transistor.

[0018] The first end of the second transistor is connected to the reset chip, the second end of the second transistor is connected to the first transistor, and the third end of the second transistor is grounded.

[0019] In some of the embodiments, the first transistor and the second transistor are one of a triode and a field effect transistor.

[0020] In some embodiments, the battery unit comprises: a second resistor, a diode and a charge-discharge battery.

[0021] One end of the second resistor is connected with the first transistor, and the other end of the second resistor is connected with one end of the charge-discharge battery; the other end of the charge-discharge battery is grounded.

[0022] The other end of the charge-discharge battery is also connected with the anode of the diode, and the cathode of the diode is connected with the real-time clock unit.

[0023] In some embodiments, the real-time clock unit comprises: a real-time clock chip and a capacitor.

[0024] One end of the capacitor is connected with the first transistor and the real-time clock chip, and the other end of the capacitor is grounded.

[0025] In some embodiments, the first transistor is connected with an auxiliary power supply; the voltage provided by the auxiliary power supply is greater than the voltage provided by the external power supply.

[0026] In a second aspect, a network camera is provided in the embodiments, comprising the chargeable real-time clock device of any one of the first aspect.

[0027] Compared with the related art, the chargeable real-time clock device and the network camera provided in the embodiments comprise a power supply switching unit, a battery unit and a real-time clock unit; the power supply switching unit comprises a first transistor; an external power supply is connected with the battery unit and the real-time clock unit through the first transistor, so as to supply power to the battery unit and the real-time clock unit when the first transistor is turned on; the battery unit is also connected with the real-time clock unit, for supplying power to the real-time clock unit when the first transistor is turned off, solving the problem of overcharging or not fully charging, prolonging the service life of the battery, and reducing the reverse leakage current when the external power supply is powered off, prolonging the time of power failure retention.

[0028] The details of one or more embodiments of the present application are presented in the following drawings and description to make other features, objects and advantages of the present application more apparent. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings described herein are intended to provide further understanding of the present application, and form a part of the present application. The schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0030] Figure 1 It is a structural schematic diagram of a real-time clock power supply circuit in the prior art.

[0031] Figure 2 Structure block diagram of a rechargeable real-time clock device in one embodiment;

[0032] Figure 3 Structure block diagram of a rechargeable real-time clock device in one preferred embodiment;

[0033] Figure 4 Circuit topology of a rechargeable real-time clock device in one preferred embodiment;

[0034] Figure 5 Waveform of a reset chip output signal in one preferred embodiment;

[0035] Figure 6 Circuit topology of a rechargeable real-time clock device in another preferred embodiment.

[0036] Reference numerals: 21, power supply switching unit; 22, battery unit; 23, real-time clock unit; 24, switching control unit; 241, voltage comparison circuit; 242, switch control circuit; 31, first waveform; 32, second waveform. DETAILED DESCRIPTION

[0037] In order to more clearly understand the objects, technical solutions and advantages of the present application, the present application is described and explained below in conjunction with the accompanying drawings and embodiments.

[0038] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the same meaning as those commonly understood by a person having ordinary skill in the art to which the present application belongs. In the present application, the terms "one", "a", "an", "the", "these", and similar terms are not limited to refer to only one thing, but can refer to one or more things. In the present application, the terms "include", "contain", "have", and any variants thereof are intended to cover the non-exclusive inclusion; for example, a process, method, and system, product or device including a series of steps or modules (units) are not limited to the listed steps or modules (units), but can include steps or modules (units) not listed, or can include other steps or modules (units) inherent to the process, method, product or device. In the present application, the terms "connect", "connected", "coupled" and the like are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. In the present application, "multiple" refers to two or more. "And / or" describes the association between the associated objects, which means that there can be three relationships, for example, "A and / or B" can mean that A exists alone, A and B exist together, and B exists alone. Generally, the character " / " represents an "or" relationship between the associated objects. In the present application, the terms "first", "second", "third" and the like are only used to distinguish similar objects, and do not represent a specific order of the objects.

[0039] In the present embodiment, a chargeable real-time clock device is provided, Figure 2 is a structural block diagram of the chargeable real-time clock device of the present embodiment, as Figure 2 shown, the device includes a power supply switching unit 21, a battery unit 22, and a real-time clock unit 23; the power supply switching unit 21 includes a first transistor.

[0040] The external power supply is connected to the battery unit 22 and the real-time clock unit 23 through the first transistor, so as to supply power to the battery unit 22 and the real-time clock unit 23 when the first transistor is turned on.

[0041] The battery unit 22 is also connected to the real-time clock unit 23, for supplying power to the real-time clock unit 23 when the first transistor is turned off.

[0042] Specifically, the first transistor is one of a triode and a field effect transistor, and preferably, the first transistor is a MOS transistor. The first end of the first transistor is connected with an external power supply, and the external power supply serves as a power supply; the second end of the first transistor is connected with the battery unit 22 and the real-time clock unit 23; when the voltage of the external power supply is greater than the voltage of the battery unit 22, the first transistor is turned on, the external power supply charges the battery unit 22, and supplies power to the real-time clock unit 23. The third end of the first transistor is connected with a control signal, which controls the on and off of the first transistor, and the control signal can be provided by an auxiliary power supply higher than the external power supply, or generated by the switching control unit 24, that is, the switching control unit 24 is connected with the third end of the first transistor.

[0043] In the embodiment, the power supply switching unit 21 includes a first transistor; the external power supply is connected with the battery unit 22 and the real-time clock unit 23 through the first transistor, so as to supply power to the battery unit 22 and the real-time clock unit 23 when the first transistor is turned on; the battery unit 22 is also connected with the real-time clock unit 23, and is used to supply power to the real-time clock unit 23 when the first transistor is turned off. The on-resistance of the transistor is small, and the on-voltage drop is close to zero, so there is no problem of incomplete charging or overcharging when a diode is used. Moreover, the reverse leakage current of the transistor is small when it is turned off, which prolongs the time of power failure retention.

[0044] In some embodiments, referring to Figure 3 , the device further includes a voltage comparison circuit 241 and a switch control circuit 242.

[0045] One end of the voltage comparison circuit 241 is connected with the external power supply, and the other end of the voltage comparison circuit 241 is connected with the first transistor through the switch control circuit 242.

[0046] The switch control circuit 242 is used to control the on of the first transistor according to the output of the voltage comparison circuit 241.

[0047] Specifically, the voltage comparator circuit 241 is used to determine whether the voltage supplied by the external power supply is lower than a preset voltage; the switch control circuit 242 is used to convert the output signal of the voltage comparator circuit 241 to control the first transistor. If the voltage supplied by the external power supply is lower than the preset voltage, it means that the external power supply cannot supply power to the real-time clock unit 23 normally (i.e., power failure), so the switch control circuit 242 is controlled to output a cutoff signal, which controls the first transistor to be cut off; conversely, if the voltage supplied by the external power supply is not lower than the preset voltage, the switch control circuit 242 is controlled to output a conduction signal, which controls the first transistor to be turned on. In one embodiment, the switch control circuit 242 is an inverter, and the first transistor is a PMOS transistor. When the voltage supplied by the external power supply is lower than the preset voltage, the voltage comparator circuit 241 outputs a low level, the inverter outputs a high level under the control of the low level, and the PMOS transistor is cut off under the control of the high level; when the voltage supplied by the external power supply is higher than the preset voltage, the voltage comparator circuit 241 outputs a high level, the inverter outputs a low level under the control of the high level, and the PMOS transistor is turned on under the control of the low-high level.

[0048] In this application, the voltage comparison circuit 241 and the switch control circuit 242 serve as the switching control unit 24, generating control signals to improve the control accuracy of the power supply switching unit 21 and ensure the accuracy of power supply mode switching.

[0049] In some of these embodiments, see Figure 4 The voltage comparison circuit 241 includes a reset chip; the reset signal output terminal of the reset chip is connected to the switch control circuit 242.

[0050] Specifically, the power-on reset (POR) function of the reset chip, with its built-in voltage comparator, allows for more reliable control of the first transistor's on / off state via an external power supply voltage. Figure 5 This is a schematic diagram of the output waveform of the reset chip. Figure 5 In the waveform, the first waveform 31 represents the change in the external power supply VCC, and the second waveform 32 represents the change in the reset signal RESET; when the external power supply increases and exceeds the threshold voltage VCC... TH The reset signal also changes from low to high accordingly; when the external power supply decreases and falls below the threshold voltage V TH The reset signal also changes from high to low accordingly. This is due to the internal threshold voltage V of the reset chip. TH2.93V, when the external power supply is powered off, the rechargeable real-time clock device does not have the risk of reverse leakage. In one embodiment, the first end of the first transistor is connected to the external power supply through the resistor R1, and the second end of the first transistor is grounded through the capacitor C1. Due to the existence of C1 and R1, even if there is a very short reverse leakage time, it will be filtered out. In addition, since most small system reset circuits already have reset chips, there is no need to increase the cost of additional reset chips.

[0051] In some embodiments, referring to Figure 4 , the voltage comparison circuit 241 further comprises: a first resistor R8; the reset signal output end of the reset chip is further connected to ground through the first resistor R8.

[0052] Specifically, the first resistor R8 controls the reset chip to output a stable and reliable reset signal, thereby accurately controlling the switch control circuit 242.

[0053] In some embodiments, the switch control circuit 242 comprises: a second transistor. The first end of the second transistor is connected to the reset chip; the second end of the second transistor is connected to the first transistor; and the third end of the second transistor is grounded.

[0054] Specifically, the second end of the second transistor is further connected to the external power supply. The second transistor is one of a triode and a field effect transistor. Taking the second transistor as an NMOS tube as an example, referring to Figure 4 , the gate of the NMOS tube M1 is connected to the reset signal output end of the reset chip, the drain of the NMOS tube M1 is connected to the external power supply through the resistor R4, the drain of the NMOS tube M1 is further connected to the first transistor, and the source of the NMOS tube M1 is grounded. The NMOS tube M1 connects the reset chip and the first transistor as an inverter.

[0055] In some embodiments, referring to Figure 4 and Figure 6 , the battery unit 22 comprises: a second resistor R3, a diode D1, and a charge-discharge battery BT1.

[0056] One end of the second resistor R3 is connected to the first transistor, and the other end of the second resistor R3 is connected to one end of the charge-discharge battery BT1; the other end of the charge-discharge battery BT1 is grounded; one end of the charge-discharge battery BT1 is further connected to the positive electrode of the diode D1, and the negative electrode of the diode D1 is connected to the real-time clock unit 23.

[0057] In some embodiments, referring to Figure 4 and Figure 6 , the real-time clock unit 23 comprises: a real-time clock chip and a capacitor C1. One end of the capacitor C1 is connected to the first transistor and the real-time clock chip, and the other end of the capacitor C1 is grounded.

[0058] Specifically, one end of the capacitor C1 and the output end of the first transistor are connected with the power supply end VRTC of the real-time clock chip.

[0059] In some of the embodiments, the first transistor is connected with an auxiliary power supply; the voltage provided by the auxiliary power supply is greater than that of the external power supply.

[0060] Specifically, referring to Figure 6 , the first transistor is a MOS transistor M3, the 3.3V external power supply is connected with the source S of the MOS transistor M3 through the resistor R1, the 5.0V auxiliary power supply is connected with the gate G of the MOS transistor M3 through the resistor R6, the drain D of the MOS transistor M3 is connected with the battery unit 22, and the source S of the MOS transistor M3 is further connected with the ground through the resistor R2. When the system power supply exists, i.e. 3.3V, 5.0V, the Vgs of the MOS transistor M3 is 1.7V, the MOS transistor M3 is turned on, 3.3V is divided into 3.1V through the resistors R1 and R2, the battery BT1 is charged through M3 and R3, and the real-time clock chip is powered at the same time through M3. When the system power supply is off, 3.3V and 5.0V are off to 0V, the Vgs of the MOS transistor M3 is 0V, the MOS transistor M3 is cut off (the MOS body diode is also reversely cut off), and the real-time clock chip is powered by BT1 through R3 and D1. When the MOS transistor M3 is cut off, the current through the MOS body diode is nA level, which is much smaller than the leakage current of the Schottky diode.

[0061] In the embodiment, the charging and discharging of the RTC battery is realized through a simple circuit structure, and the cost of the device is reduced.

[0062] The embodiment will be described and explained below through preferred embodiments.

[0063] Figure 4 is the circuit topology of the rechargeable real-time clock device of the preferred embodiment. As shown in Figure 4 , the rechargeable real-time clock device comprises a power supply switching unit 21, a battery unit 22, a real-time clock unit 23, and a switching control unit 24.

[0064] The power supply switching unit 21 comprises a MOS transistor M2, a resistor R1, and a resistor R2. The 3.3V external power supply is connected with the drain D of the MOS transistor M2 through the resistor R1, and the drain D of the MOS transistor M2 is further connected with the ground through the resistor R2.

[0065] The battery unit 22 comprises a resistor R3, a diode D1, and a rechargeable battery BT1. One end of the resistor R3 is connected with the source S of the MOS transistor M2, the other end of the resistor R3 is connected with one end of the rechargeable battery BT1, and the other end of the rechargeable battery BT1 is connected with the ground; one end of the rechargeable battery BT1 is further connected with the anode of the diode D1, and the cathode of the diode D1 is connected with the source S of the MOS transistor M2.

[0066] The real-time clock unit 23 comprises a real-time clock chip and a capacitor C1. One end of the capacitor C1 is connected with the first transistor and the real-time clock chip, and the other end of the capacitor C1 is grounded; the real-time clock chip is also connected with the source S of the M2.

[0067] The switching control unit 24 comprises a reset chip, a resistor R8, a MOS transistor M1 and a resistor R4. The reset signal output end of the reset chip is connected with the gate G of the MOS transistor M1, the drain D of the MOS transistor M1 is connected with the power supply end VRTC of the real-time clock chip through the resistor R4, the drain D of the MOS transistor M1 is also connected with the gate G of the MOS transistor M2, and the source S of the MOS transistor M1 is grounded.

[0068] When the external power supply is powered off, the voltage VCC provided by the external power supply is lower than the threshold voltage V TH of the reset chip, the reset chip outputs a low-level signal, the reset signal at the low level controls the MOS transistor M1 to output a high-level signal, the high-level signal of the M1 controls the MOS transistor M2 to be cut off, at this time, the charge-discharge battery BT1 supplies power to the real-time clock chip through the diode D1.

[0069] When the external power supply is powered on, the voltage VCC provided by the external power supply is higher than the threshold voltage V TH of the reset chip, the reset chip outputs a high-level signal, the reset signal at the high level controls the MOS transistor M1 to output a low-level signal, the low-level signal of the M1 controls the MOS transistor M2 to be turned on, at this time, the external power supply charges the charge-discharge battery BT1 and supplies power to the real-time clock chip through the M2.

[0070] The preferred embodiment uses a MOS transistor to replace a Schottky diode, and controls the gate of the MOS transistor M2 through a reset chip and the MOS transistor M1. When the external power supply voltage is greater than the threshold voltage V TH , the MOS transistor M2 is turned on; when the system power supply is less than the threshold voltage V TH , the MOS transistor M2 is switched off. Since the on-resistance of the MOS transistor M2 is very small, the on-voltage drop is close to zero, so there is no problem of incomplete charging or overcharging when a diode is used. And since the reverse leakage current of the body diode of the MOS transistor M2 is very small when it is cut off, it is generally in the order of nA, so there is no problem of large reverse leakage current after the system is powered off. The internal V TH of the reset chip is usually 2.93V, there is no risk of reverse leakage when the RTC is powered off, and since C1 and R1 exist, even if there is a very short reverse leakage time, it will be filtered out. In addition, since most small system reset circuits already have a reset chip, there is no need to increase the cost of the reset chip.

[0071] The battery charging voltage of the preferred embodiment is equal to the external power supply voltage, and there is no influence of the diode conduction voltage drop. The problem of overcharging or incomplete charging is solved, and the service life of the battery is prolonged. The reverse leakage current is very small when the external power supply is powered off, greatly prolonging the power-off retention time of the RTC circuit. The circuit structure of the preferred embodiment is simple and low in cost.

[0072] In the present embodiment, there is also provided a network camera comprising the rechargeable real-time clock device of any of the above embodiments.

[0073] In the present embodiment, the rechargeable real-time clock device provides a time reference for the network camera, wherein the device controls the power supply switching unit 21 to be on or off by the system power supply (i.e. external power supply) of the network camera to realize the functions of charging and power-off retention of the RTC battery, and can prolong the service life and power-off retention time of the battery, ensuring the stability and reliability of the network camera.

[0074] Obviously, the drawings are only some examples or embodiments of the present application, and the present application can also be applied to other similar situations without creative labor according to the drawings for those skilled in the art. In addition, it can be understood that although the work done in the development process may be complex and long, some design, manufacture or production changes according to the technical content disclosed in the present application are only routine technical means for those skilled in the art, and should not be regarded as insufficient disclosure of the present application.

[0075] The term "embodiment" in the present application means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present application. The presence of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean independence or alternative to other embodiments. It can be clearly or implicitly understood by those skilled in the art that the embodiments described in the present application can be combined with other embodiments without conflict.

[0076] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of patent protection. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of protection of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A rechargeable real-time clock device, characterized by, The device comprises a power supply switching unit, a battery unit and a real-time clock unit; the power supply switching unit comprises a first transistor; An external power supply is connected with the battery unit and the real-time clock unit through the first transistor, so as to supply power to the battery unit and the real-time clock unit when the first transistor is turned on; The battery unit is also connected with the real-time clock unit, and is used to supply power to the real-time clock unit when the first transistor is turned off.

2. The rechargeable real-time clock device of claim 1, wherein, The device further comprises a voltage comparison circuit and a switch control circuit; One end of the voltage comparison circuit is connected with the external power supply, and the other end of the voltage comparison circuit is connected with the first transistor through the switch control circuit; The switch control circuit is used to control the first transistor to be turned on according to the output of the voltage comparison circuit.

3. The rechargeable real-time clock device of claim 2, wherein, The voltage comparison circuit comprises a reset chip; a reset signal output end of the reset chip is connected with the switch control circuit.

4. The rechargeable real-time clock device of claim 3, wherein, The voltage comparison circuit further comprises a first resistor; the reset signal output end of the reset chip is also connected with the ground through the first resistor.

5. The rechargeable real-time clock device of claim 3, wherein, The switch control circuit comprises a second transistor; A first end of the second transistor is connected with the reset chip; a second end of the second transistor is connected with the first transistor; and a third end of the second transistor is connected with the ground.

6. The rechargeable real-time clock device of claim 5, wherein, The first transistor and the second transistor are one of a triode and a field effect transistor.

7. The rechargeable real-time clock device of claim 1, wherein, The battery unit comprises a second resistor, a diode and a charge-discharge battery; One end of the second resistor is connected with the first transistor, and the other end of the second resistor is connected with one end of the charge-discharge battery; the other end of the charge-discharge battery is connected with the ground; One end of the charge-discharge battery is also connected with a positive electrode of the diode, and a negative electrode of the diode is connected with the real-time clock unit.

8. The rechargeable real-time clock device of claim 1, wherein, The real-time clock unit comprises a real-time clock chip and a capacitor; One end of the capacitor is connected with the first transistor and the real-time clock chip, and the other end of the capacitor is connected with the ground.

9. The rechargeable real-time clock device of claim 1, wherein, The first transistor is connected with an auxiliary power supply; and the auxiliary power supply provides a voltage greater than the external power supply.

10. A network camera, characterized by The device comprises a chargeable real-time clock device as claimed in any one of claims 1 to 9.

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