Real-time clock backup power supply circuit

Abstract

The utility model provides a real -time clock backup power supply power supply circuit, include: real -time clock chip U2, main power supply VCC, backup power supply VRTC, diode D1, diode D2, battery BT1, super capacitor C1 and switching circuit, main power supply VCC is connected with diode D1's anode, diode D1's cathode is connected with super capacitor C1's positive pole, diode D2's anode and switching circuit respectively, super capacitor C1's negative pole is grounded, diode D2's cathode is connected with backup power supply VRTC and switching circuit respectively, battery BT1's positive pole is connected with switching circuit, main power supply VCC and backup power supply VRTC all are connected with real -time clock chip U2. The circuit uses battery and super capacitor as backup power supply and supplies power for real -time clock, realizes the power supply switching control through hardware circuit, prolongs the working time after power failure. The circuit does not need software control, and the device of circuit is less and simple in structure, and the cost is also lower.

Description

Technical Field

[0001] This utility model relates to a real-time clock circuit, and more particularly to a real-time clock backup power supply circuit. Background Technology

[0002] A real-time clock (RTC) is a timekeeping device that provides real-time time information to the system. An RTC needs to provide an accurate clock reference continuously over a long period. To ensure continuous operation, a backup power supply is provided in addition to the main power supply to guarantee power supply after a power outage. Currently, the backup power supply for RTCs generally uses non-rechargeable batteries, such as button cells or cylindrical batteries; some RTCs also use supercapacitors. However, each of these methods has its own advantages and disadvantages. The advantages of using button cells or cylindrical batteries are their small size, low self-discharge, and long operating time, making them suitable for applications with prolonged power outages. However, their capacity is limited, and they are not rechargeable. The advantages of using supercapacitors are their rapid charging and discharging capabilities, repeated charging and discharging, and simple charging and discharging circuitry, making them suitable for applications with frequent power outages and restarts. However, their disadvantages include a large self-discharge current, and a single supercapacitor used as a backup power supply requires a larger capacity and is more expensive.

[0003] Therefore, using a single battery or supercapacitor as a backup power source cannot fully meet the requirements for continuous operation of the real-time clock. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to propose a real-time clock backup power supply circuit. This circuit uses both supercapacitors and batteries as backup power sources, and performs hardware switching control between the battery and the supercapacitor through the circuit to achieve power supply to the real-time clock after power failure.

[0005] This utility model provides a real-time clock backup power supply circuit, including: a real-time clock chip U2, a main power supply VCC, a backup power supply VRTC, diodes D1 and D2, a battery BT1, a supercapacitor C1, and a switching circuit; the main power supply VCC is connected to the anode of diode D1; the cathode of diode D1 is connected to the positive terminal of supercapacitor C1, the anode of diode D2, and the switching circuit; the negative terminal of supercapacitor C1 is grounded; the cathode of diode D2 is connected to the backup power supply VRTC and the switching circuit; the positive terminal of battery BT1 is connected to the switching circuit, and the negative terminal of battery BT1 is grounded; both the main power supply VCC and the backup power supply VRTC are connected to the real-time clock chip U2.

[0006] A further improvement of this utility model is that the switching circuit includes: a PMOS transistor Q1 and a voltage detection chip U1; the voltage detection chip U1 is connected to the positive terminal of the supercapacitor C1 and the gate terminal of the PMOS transistor Q1 respectively; the drain terminal of the PMOS transistor Q1 is connected to the backup power supply VRTC; and the source terminal of the PMOS transistor Q1 is connected to the positive terminal of the battery BT1.

[0007] A further improvement of this utility model is that the voltage detection chip U1 is model BL8506, the VDD pin of the voltage detection chip U1 is connected to the positive terminal of the supercapacitor C1; the VOUT pin of the voltage detection chip U1 is connected to the gate terminal of the PMOS transistor Q1; and the VSS pin of the voltage detection chip U1 is grounded.

[0008] A further improvement of this invention is that the switching circuit further includes a diode D3; the anode of the diode D3 is connected to the positive terminal of the battery BT1; and the cathode of the diode D3 is connected to the source terminal of the PMOS transistor Q1.

[0009] A further improvement of this invention is that the switching circuit further includes a resistor R1, the two ends of which are connected to the source (S) and gate (G) of the PMOS transistor Q1, respectively.

[0010] A further improvement of this invention is that diodes D1, D2, and D3 are all Schottky diodes.

[0011] Compared with existing technologies, the advantages of this invention are as follows: Unlike existing technologies that use a single battery or supercapacitor as a backup power source, this circuit provides both a battery and a supercapacitor as backup power for the real-time clock, effectively combining the advantages of both. Hardware circuitry enables switching control between the battery and supercapacitor power supplies, extending the real-time clock's operating time after power failure. Furthermore, this circuit requires no software control, has fewer components and a simpler structure, is easier to implement, and has lower costs. Attached Figure Description

[0012] Figure 1 This is a circuit schematic diagram of one embodiment of the present invention.

[0013] Attached diagram label: 1 - Switching circuit. Detailed Implementation

[0014] In the description of this utility model, if directional descriptions are involved, such as "up," "down," "front," "back," "left," "right," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, it is only for the convenience of describing this utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. If a certain technical feature is referred to as "set," "fixed," "connected," or "installed" on another technical feature, it can be directly set, fixed, or connected to the other technical feature, or it can be indirectly set, fixed, connected, or installed on the other technical feature.

[0015] In the description of this utility model, the term "several" means one or more; the term "multiple" means two or more; the terms "greater than," "less than," and "exceeding" should be understood as excluding the stated number; and the terms "above," "below," and "within" should be understood as including the stated number. The terms "first," "second," etc., should be understood as being used only to distinguish identical or similar technical feature names, and should not be interpreted as implying / indicating the relative importance of the technical features, the number of technical features, or the sequential relationship between the technical features.

[0016] The preferred embodiments of this utility model will be further described in detail below with reference to the accompanying drawings: like Figure 1 As shown, this embodiment provides a real-time clock backup power supply circuit, comprising a real-time clock chip U2, a main power supply VCC, a backup power supply VRTC, diodes D1 and D2, a battery BT1, a supercapacitor C1, and a switching circuit 1. The main power supply VCC is connected to the anode of diode D1. The cathode of diode D1 is connected to the anode of supercapacitor C1, the anode of diode D2, and the switching circuit 1. The cathode of supercapacitor C1 is grounded. The cathode of diode D2 is connected to the backup power supply VRTC and the switching circuit 1. The anode of battery BT1 is connected to the switching circuit 1, and the cathode of battery BT1 is grounded. Both the main power supply VCC and the backup power supply VRTC are connected to the real-time clock chip U2.

[0017] More specifically, the main power supply VCC powers the real-time clock chip U2 upon power-on and supplies power to the real-time clock chip U2 via the backup power supply VRTC upon power-off. In this embodiment, the main power supply VCC voltage is 3.3V, the battery BT1 is a CR2032 button cell battery, and the specific model of the real-time clock chip U2 is RX8111CE. The VDD pin of the real-time clock chip U2 RX8111CE is connected to the main power supply VCC, and the VBAT pin is connected to the backup power supply VRTC. After the main power supply VCC is de-energized, the switching circuit 1 controls the selection of either the supercapacitor C1 or the battery BT1 as the power supply device for the backup power supply VRTC based on the positive voltage of the supercapacitor C1. The specific control principle is as follows: When the main power supply VCC fails, supercapacitor C1 is preferentially used as the power supply device for the backup power supply VRTC. Supercapacitor C1 supplies power to the real-time clock chip U2 through diode D2. When the voltage supplied to VRTC by the positive terminal of supercapacitor C1 through diode D2 is insufficient to maintain the operation of the real-time clock chip U2, switching circuit 1 controls PMOS transistor Q1 to conduct, and battery BT1 acts as the power supply device for the backup power supply VRTC, supplying power to the real-time clock chip U2. After the main power supply VCC is powered on again, supercapacitor C1 is charged, and supercapacitor C1 stores energy to be used for power supply during the next power failure. The function of diode D1 is that when battery BT1 is used as the power supply device to supply backup power supply VRTC, diode D2 is reverse-biased and cut off to prevent charging of supercapacitor C1. The function of diode D1 is that when supercapacitor C1 is used as the power supply device to supply backup power supply VRTC, diode D1 is reverse-biased and cut off to prevent power supply to the main power supply VCC. It is worth noting that in this embodiment, the battery and supercapacitor are not simply used together. Instead, the advantages of both are fully utilized: because the supercapacitor C1 can be repeatedly charged and discharged, the backup power supply VRTC preferentially uses the supercapacitor C1 as its power supply until the supply voltage of the supercapacitor C1 is insufficient to maintain the operation of the real-time clock chip U2, at which point it switches to battery BT1. This delays the use of battery BT1 as the backup power supply for VRTC, thereby extending the operating time of the real-time clock chip U2 after power failure.

[0018] like Figure 1 As shown, the switching circuit 1 includes: a PMOS transistor Q1 and a voltage detection chip U1; the voltage detection chip U1 is connected to the positive terminal of the supercapacitor C1 and the gate terminal of the PMOS transistor Q1 respectively; the drain terminal of the PMOS transistor Q1 is connected to the backup power supply VRTC; and the source terminal of the PMOS transistor Q1 is connected to the positive terminal of the battery BT1.

[0019] like Figure 1As shown, the voltage detection chip U1 is model BL8506. The VDD pin of the voltage detection chip U1 is connected to the positive terminal of the supercapacitor C1; the VOUT pin of the voltage detection chip U1 is connected to the gate terminal of the PMOS transistor Q1; and the VSS pin of the voltage detection chip U1 is grounded.

[0020] More specifically, in this embodiment, the minimum operating voltage of the real-time clock chip U2 RX8111CE is 1.1V, the maximum current consumption is approximately 3uA, and the forward voltage drop of diode D2 BAT54 is approximately 0.3V. Considering all factors, the voltage detection threshold of the voltage detection chip U1BL8506 is selected as 1.5V. When the voltage detection chip U1's pin VDD detects that the positive voltage of the supercapacitor C1 is lower than 1.5V, the VOUT pin will output a low level, pulling the gate (G) of PMOS transistor Q1 low. Therefore, PMOS transistor Q1 conducts, and battery BT1 supplies power to the real-time clock chip U2 through PMOS transistor Q1. It is worth noting that in this embodiment, the switching control between supercapacitor C1 and battery BT1 is entirely implemented through the hardware circuit of switching circuit 1, without the need for software control. The circuit structure is simple, requires few components, is easy to implement, and has a low cost.

[0021] like Figure 1 As shown, the switching circuit 1 further includes a diode D3; the anode of the diode D3 is connected to the positive terminal of the battery BT1; the cathode of the diode D3 is connected to the source terminal of the PMOS transistor Q1. More specifically, the function of the diode D3 is that, due to manufacturing process limitations, most PMOS transistors typically have a parasitic diode running from the drain (D) to the source (S). Therefore, when the PMOS transistor Q1 is turned off, the diode D3 prevents the backup power supply VRTC from charging the battery BT1 through the parasitic diode of the PMOS transistor Q1.

[0022] like Figure 1 As shown, the switching circuit 1 further includes a resistor R1, the two ends of which are connected to the source (S) and gate (G) of the PMOS transistor Q1, respectively. More specifically, the function of the resistor R1 is to bridge the source and gate of the PMOS transistor Q1 and simultaneously pull up the voltage detection chip U1's pin VOUT to prevent the PMOS transistor Q1 from turning on due to external electromagnetic interference or other reasons.

[0023] like Figure 1 As shown, diodes D1, D2, and D3 are Schottky diodes. More specifically, the reason for using Schottky diodes for diodes D1, D2, and D3 is that Schottky diodes have a lower on-state voltage drop than ordinary diodes, which can extend the operating time of supercapacitor C1 and battery BT1.

[0024] In summary, this embodiment provides a backup power supply circuit for a real-time clock. Unlike existing technologies that use a single battery or supercapacitor as a backup power source, this circuit provides both a battery and a supercapacitor as backup power for the real-time clock. This effectively combines the advantages of both, avoiding the drawback of a battery being unrechargeable and the large size and high cost of a supercapacitor. This embodiment uses hardware circuitry to control the switching between battery and supercapacitor power supply, extending the real-time clock's operating time after power failure. Furthermore, this circuit requires no software control, has few components, a simple structure, is easy to implement, and has a low cost.

[0025] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the protection scope of the present invention.

Claims

1. A real-time clock backup power supply circuit, characterized in that, include: The system includes a real-time clock chip U2, a main power supply VCC, a backup power supply VRTC, diodes D1 and D2, a battery BT1, a supercapacitor C1, and a switching circuit. The main power supply VCC is connected to the anode of diode D1. The cathode of diode D1 is connected to the anode of supercapacitor C1, the anode of diode D2, and the switching circuit. The cathode of supercapacitor C1 is grounded. The cathode of diode D2 is connected to the backup power supply VRTC and the switching circuit. The anode of battery BT1 is connected to the switching circuit, and the cathode of battery BT1 is grounded. Both the main power supply VCC and the backup power supply VRTC are connected to the real-time clock chip U2.

2. The real-time clock backup power supply circuit according to claim 1, characterized in that, The switching circuit includes a PMOS transistor Q1 and a voltage detection chip U1; the voltage detection chip U1 is connected to the positive terminal of the supercapacitor C1 and the gate terminal of the PMOS transistor Q1; the drain terminal of the PMOS transistor Q1 is connected to the backup power supply VRTC; and the source terminal of the PMOS transistor Q1 is connected to the positive terminal of the battery BT1.

3. The real-time clock backup power supply circuit according to claim 2, characterized in that, The voltage detection chip U1 is model BL8506. The VDD pin of the voltage detection chip U1 is connected to the positive terminal of the supercapacitor C1; the VOUT pin of the voltage detection chip U1 is connected to the gate terminal of the PMOS transistor Q1; and the VSS pin of the voltage detection chip U1 is grounded.

4. The real-time clock backup power supply circuit according to claim 2, characterized in that, The switching circuit also includes a diode D3; the anode of the diode D3 is connected to the positive terminal of the battery BT1; and the cathode of the diode D3 is connected to the source terminal of the PMOS transistor Q1.

5. The real-time clock backup power supply circuit according to any one of claims 2 to 4, characterized in that, The switching circuit also includes a resistor R1, the two ends of which are connected to the source (S) and gate (G) of the PMOS transistor Q1, respectively.

6. The real-time clock backup power supply circuit according to claim 5, characterized in that, Diodes D1, D2, and D3 are all Schottky diodes.

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