Abnormal power failure protection circuit structure for vehicle-mounted tablet computer
By introducing a power failure detection circuit and a supercapacitor backup power circuit into the vehicle-mounted tablet, the problems of data loss and storage device damage caused by abnormal power failure of the vehicle-mounted tablet are solved, achieving data protection effects with fast response, high reliability and high energy utilization, and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHENZHEN CONGPING TECH CO LTD
- Filing Date
- 2025-05-30
- Publication Date
- 2026-05-01
AI Technical Summary
In the event of an abnormal power outage, in-vehicle tablets are prone to data loss and damage to storage devices. Existing technical solutions, such as using lithium batteries, pose high-temperature safety hazards and are highly uncontrollable. The ACC ignition switch solution cannot completely solve the power outage problem.
The system employs a power failure detection circuit and a supercapacitor backup power supply circuit. By quickly detecting power failure signals and switching to the supercapacitor backup power supply, the system ensures that it completes the data protection process in the event of an abnormal power failure. This includes the combined use of the power failure detection circuit, the backup power supply circuit, and the system processing module.
It achieves rapid response (less than 1ms) during abnormal power outages, high reliability (supercapacitors are resistant to high temperatures and have long cycle life), high energy utilization (discharge circuit boost design), low cost (using general-purpose DC-DC modules and discrete components), and effectively prevents data loss and storage device damage.
Smart Images
Figure CN224191653U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a power-off protection circuit structure, and in particular to a vehicle-mounted tablet abnormal power-off protection circuit structure. Background Technology
[0002] Vehicle-mounted tablets are typically installed in the cab of a work vehicle and are directly powered by the vehicle's battery or alternator. During use, situations frequently arise where the vehicle's battery or alternator suddenly disconnects, resulting in the tablet losing power without warning. This situation is extremely dangerous for vehicle-mounted tablets. Because the tablet is in operation, it performs read and write operations on its internal storage devices. If a sudden power outage occurs without any intervention, it can lead to data loss or corruption, and in severe cases, even damage to the storage device's hardware, causing very serious consequences for vehicle operations.
[0003] The existing product solution uses lithium batteries as backup power. However, lithium batteries are not heat-resistant and cannot meet the operating requirements of vehicle-mounted tablets in high-temperature environments. They also pose safety hazards, as battery problems caused by high temperatures can lead to unpredictable consequences.
[0004] Another existing solution relies on the vehicle's ACC ignition switch as a power-off protection function for the in-vehicle tablet. This requires restricting the tablet from being powered off by turning off the ACC ignition switch. This solution is uncontrollable; firstly, it cannot manage user behavior, as some users prefer to directly disconnect the power to shut down. Secondly, it cannot prevent unexpected power outages. Due to these two drawbacks, this solution cannot completely solve the problems caused by abnormal power outages in the in-vehicle tablet, posing a potential risk. Summary of the Invention
[0005] To address the shortcomings of existing technical solutions, this utility model provides a circuit structure for abnormal power loss protection of vehicle-mounted tablets. By quickly detecting power loss signals and switching to a supercapacitor backup power supply, it ensures that the system completes the data protection process during abnormal power loss, thus solving problems such as data loss and damage to eMMC and TF storage devices caused by abnormal power loss during the use of vehicle-mounted tablets.
[0006] The technical solution adopted by this utility model to solve its technical problem is:
[0007] A circuit structure for abnormal power failure protection of a vehicle-mounted tablet includes a power failure detection circuit, a backup power supply circuit, and a system processing module.
[0008] The power failure detection circuit is used to monitor the main power supply voltage in real time, and outputs a power failure signal when the voltage is lower than a set threshold; the backup power supply circuit stores energy by a supercapacitor and provides temporary power to the system through a charging and discharging circuit; the system processing module is used to receive the power failure signal and trigger an interrupt to control the tablet to enter the data protection state.
[0009] The main power input (VCC_DCIN) is connected to both the power failure detection circuit and the backup power circuit; the output of the power failure detection circuit (BATT_OFF_DET) is connected to the interrupt pin of the system processing module and sends a control signal (EN) to the backup power circuit; the backup power circuit is isolated from the main power supply through Schottky diode D2, and its output (VCC_BACKUP) is connected to the system power supply bus.
[0010] Furthermore, the power failure detection circuit and the backup power supply circuit communicate with each other through direct control. The output of the power failure detection circuit directly controls the opening and closing of the backup power supply, making the backup power supply respond more quickly and reliably.
[0011] The system processing module processes the signals transmitted from the power failure detection circuit via interrupts, enabling it to respond immediately when a power failure occurs.
[0012] The power-down detection circuit includes a voltage divider network, a Zener diode D1, and transistors Q1 and Q2. The voltage divider network consists of resistors R1, R2, and R3, used to set a 7V power-down detection threshold. The Zener diode D1 is connected to the midpoint of the voltage divider network to ensure voltage division stability. The base of transistor Q1 is connected to the output of the voltage divider network, and its conduction state is controlled by the VCC_DCIN voltage. The base of transistor Q2 is connected to the collector of Q1; when Q1 is off, Q2 conducts, outputting a low-level BATT_OFF_DET signal.
[0013] Furthermore, the 7V power-down detection threshold is determined by the Zener diode D1, the BE on-state voltage drop of the transistor Q1, and the voltage division of the resistors R1, R2, and R3. The power-down detection threshold can be adjusted by adjusting the parameters of D1, R1, R2, and R3.
[0014] The backup power circuit consists of a large-capacity supercapacitor C4, a charging circuit U1, a discharging circuit U2, and a resistor R19.
[0015] The supercapacitor C4 has a capacity of 10F and serves as the core of energy storage. The charging circuit U1 uses a step-down DC-DC module, with its input connected to the main power supply and its output charging C4 through a current-limiting resistor R19. The discharging circuit U2 uses a boost DC-DC module, with its input connected to C4 and its output supplying power to the system through D2. The EN signal output by the power-down detection circuit controls the enable pin of U2, triggering boost discharge.
[0016] Furthermore, the charging circuit U1 uses a step-down charging method, which has advantages such as low cost and high safety and reliability.
[0017] Furthermore, the resistor R19 is used to limit the current of the supercapacitor charging circuit, effectively preventing system malfunctions caused by excessive charging current, while ensuring the safety of the supercapacitor and improving its service life.
[0018] Furthermore, the discharge circuit U2 uses a boost circuit method for discharge, which allows the supercapacitor voltage to drop sufficiently while still continuing to power the system, greatly improving the utilization rate of the backup power supply and enhancing its endurance.
[0019] The beneficial effects of this utility model are:
[0020] 1. Fast response: The power failure detection circuit is combined with the system interrupt mechanism, and the response time is less than 1ms.
[0021] 2. High reliability: Supercapacitors are resistant to high temperatures and have a long cycle life, which is superior to lithium batteries.
[0022] 3. High energy efficiency: The discharge circuit adopts a boost design, which can still output a 5V system voltage even if the capacitor voltage drops to 1.8V; the discharge circuit adopts a boost power supply scheme to improve the energy efficiency of the supercapacitor C4 and increase the system uptime.
[0023] 4. Low cost: It adopts general-purpose DC-DC modules and discrete components, making it easy to mass-produce. Attached Figure Description
[0024] Figure 1 This is the overall block diagram of this utility model.
[0025] Figure 2 This is the power-off detection circuit diagram of this utility model.
[0026] Figure 3 This is the circuit diagram of the backup power supply for this utility model. Detailed Implementation
[0027] Now combined with the appendix Figures 1-3 The technical solution of this utility model will be further described in detail.
[0028] like Figure 1As shown, this utility model consists of a power failure detection module, a system processing module, and a backup power supply module. When the external power supply is suddenly disconnected, the power failure detection circuit responds immediately, inputting a power failure notification signal to the system. Upon receiving the power failure notification, the system immediately generates an interrupt, stopping all other services and halting data interaction between the application program and storage devices. Simultaneously, the power failure detection circuit synchronously outputs a control signal to the backup power supply, which then turns on to supply power to the system, maintaining its normal operation.
[0029] like Figure 2 As shown, the specific implementation principle of the power failure detection module circuit mainly relies on the Zener diode D1 to detect the power input VCC_DCIN. When the power supply voltage VCC_DCIN is normal, Q1 is turned on, Q2 is turned off, and the new power failure notification signal BATT_OFF_DET outputs a high level and is sent to the system. The system judges that the power supply is abnormal and no action is required.
[0030] When the power supply suddenly fails and the VCC_DCIN voltage drops below 7V, Q1 is cut off and Q2 is turned on. The new power failure notification signal BATT_OFF_DET outputs a low level and is sent to the system. The system then determines that a power failure has occurred and takes appropriate action.
[0031] The 7V power-down threshold is determined by the Zener diode D1, the BE on-state voltage drop of transistor Q1, and the voltage division of resistors R1, R2, and R3. The power-down threshold can be adjusted by adjusting the parameters of D1, R1, R2, and R3.
[0032] like Figure 3 As shown, the specific implementation principle of the backup power module circuit is mainly achieved through energy storage via supercapacitor C4. The capacity of C4 is 10 farads. In actual testing, it can maintain the operation of the vehicle-mounted tablet for 10 seconds after the power supply fails, which is sufficient to meet the system's requirements for power failure handling.
[0033] U1 is a buck DC-DC power module, responsible for charging C4. R19 is a current-limiting resistor; adjusting its value adjusts the capacitor's charging current. U2 is a boost DC-DC power module, responsible for boosting the capacitor voltage to the required system voltage to meet the system's power supply requirements.
[0034] The unidirectional conductivity of Schottky diode D2 isolates the backup power supply from the main power supply, preventing backflow of main power voltage into the backup power supply and thus preventing damage to the devices. The enable signal for U2 is provided by the power failure detection circuit. When the power failure detection circuit detects a power outage, it outputs a control signal to enable U2, causing U2 to output voltage and restore power to the system.
[0035] The following is combined with Figures 1-3 Further details on the implementation of each module:
[0036] Power-down detection circuit parameter settings: By adjusting the resistance values of R1, R2, R3 and the voltage regulation value of D1, the 7V discrimination threshold is precisely set; Q1 is an NPN transistor (such as 2N3904), and Q2 is a PNP transistor (such as 2N3906).
[0037] Backup power circuit optimization: R19 resistance is set to 1Ω to limit charging current to a safe range (≤2A); U2 uses a boost chip (such as TPS61088), with an input voltage range of 1.8V-5.5V and an output of 5V / 3A.
[0038] System processing module logic: In the interrupt service routine, unnecessary peripherals are disabled, and cached data is saved to memory first.
[0039] Actual tests show that this circuit can maintain the operation of the vehicle-mounted tablet for more than 10 seconds when the 12V main power supply is suddenly disconnected, and fully execute the data protection process with a 0% failure rate of storage devices.
[0040] Working principle: When the external power supply is suddenly interrupted, the power failure detection circuit responds immediately, sending a power failure notification signal to the system. Upon receiving the notification, the system immediately generates an interrupt, stopping all other services and halting data interaction between the application program and storage devices. Simultaneously, the power failure detection circuit outputs a control signal to the backup power supply, which then activates, supplying power to the system and maintaining its normal operation.
[0041] In the power failure detection circuit, the voltage regulation characteristics of the Zener diode are used to detect power failure. When the power supply suddenly fails and the VCC_DCIN voltage drops below 7V, Q1 is cut off and Q2 is turned on. The new power failure notification signal BATT_OFF_DET is output at a low level and sent to the system. The system determines that a power failure has occurred and takes appropriate action.
[0042] In the backup power circuit section, the energy storage characteristics of the large-capacity supercapacitor C4 are utilized to maintain power supply to the system after a power outage. A charging circuit U1 and a discharging circuit U2 are specifically designed for the supercapacitor. The charging circuit uses resistor R19 to limit the capacitor charging current, preventing excessive charging current from causing system failure.
Claims
1. A power failure protection circuit structure for a vehicle-mounted tablet, comprising a power failure detection circuit, a backup power supply circuit, and a system processing module, characterized in that: The power failure detection circuit monitors the main power supply voltage in real time and outputs a power failure signal when the voltage falls below a set threshold. The backup power supply circuit stores energy in a supercapacitor and provides temporary power to the system through a charging and discharging circuit. The system processing module receives the power failure signal and triggers an interrupt to control the tablet to enter a data protection state. The main power input is connected to both the power failure detection circuit and the backup power supply circuit. The output of the power failure detection circuit is connected to the interrupt pin of the system processing module and sends a control signal to the backup power supply circuit. The backup power supply circuit is isolated from the main power supply through a Schottky diode D2, and its output is connected to the system power supply bus.
2. The vehicle-mounted tablet abnormal power failure protection circuit structure according to claim 1, characterized in that: The power failure detection circuit and the backup power supply circuit communicate through direct control. The output of the power failure detection circuit directly controls the opening and closing of the backup power supply. The system processing module processes the signals transmitted from the power failure detection circuit through interrupts and responds immediately when a power failure occurs.
3. The vehicle-mounted tablet abnormal power failure protection circuit structure according to claim 1, characterized in that: The power-down detection circuit includes a voltage divider network, a Zener diode D1, and transistors Q1 and Q2. The voltage divider network consists of resistors R1, R2, and R3, used to set a 7V power-down threshold. The Zener diode D1 is connected to the midpoint of the voltage divider network to ensure voltage stability. The base of transistor Q1 is connected to the output of the voltage divider network, and its conduction state is controlled by the VCC_DCIN voltage. The base of transistor Q2 is connected to the collector of Q1. When Q1 is off, Q2 is on, outputting a low-level BATT_OFF_DET signal.
4. The vehicle-mounted tablet abnormal power failure protection circuit structure according to claim 3, characterized in that: The 7V power-down detection threshold is determined by the Zener diode D1, the BE forward voltage drop of the transistor Q1, and the voltage division of resistors R1, R2, and R3. The power-down detection threshold can be adjusted by adjusting the parameters of D1, R1, R2, and R3.
5. The vehicle-mounted tablet abnormal power failure protection circuit structure according to claim 1, characterized in that: The backup power circuit consists of a large-capacity supercapacitor C4, a charging circuit U1, a discharging circuit U2, and a resistor R19. The supercapacitor C4 has a capacity of 10F and serves as the energy storage core. The charging circuit U1 uses a step-down DC-DC module, with its input connected to the main power supply and its output charging C4 through a current-limiting resistor R19. The discharging circuit U2 uses a boost DC-DC module, with its input connected to C4 and its output supplying power to the system through a diode D2. The EN signal output by the power-down detection circuit controls the enable pin of U2, triggering a boost discharge.
6. The vehicle-mounted tablet abnormal power failure protection circuit structure according to claim 5, characterized in that: The charging circuit U1 uses a step-down charging method.
7. The vehicle-mounted tablet abnormal power failure protection circuit structure according to claim 5, characterized in that: The resistor R19 is used to limit the current in the supercapacitor charging circuit.
8. The vehicle-mounted tablet abnormal power failure protection circuit structure according to claim 5, characterized in that: The discharge circuit U2 uses a boost circuit method for discharge.