A universal short-time backup power supply circuit

Abstract

The present invention discloses a universal short-time backup power supply circuit, including a first switch, a charging circuit, an energy storage device, a second switch, a discharge circuit and a main control module; the power supply is connected to the charging circuit via the first switch, and the charging circuit is connected to the energy storage device; the energy storage device is connected to the discharge circuit via the second switch; the first switch is also connected to the discharge circuit via a power supply bypass; the discharge circuit supplies power to the electrical equipment and the main control module. The present invention realizes the charge and discharge management of the supercapacitor, the stable output of the discharge circuit, and the maximum utilization of the capacity of the supercapacitor; for general short-time power-off protection equipment, it is more suitable to use this universal replacement, so that there are more advantages in terms of cost and performance.

Description

Technical Field

[0001] The invention belongs to the technical field of backup power supply, and relates to a universal short-time backup power supply circuit. Background Art

[0002] With the development of IoT applications, more and more IoT devices need to use backup power to ensure that they can continue to work after the mains power is cut off. The general solution is to use the traditional lithium battery backup power solution, which is already very mature. However, the lithium battery backup power supply solution is relatively expensive and has a very small working environment range. It is generally only suitable for working in an ambient temperature of 0 to 45°C. For IoT applications, many devices are used in industrial environments and must be installed in outdoor environments. Generally, they must meet the requirements of -40°C to 60°C. Lithium batteries cannot adapt to this working environment, which will cause the capacity of lithium batteries to drop rapidly and shorten their lifespan. The general solution is to heat or temperature compensate the lithium battery, but this will increase the cost and complexity of the application. Therefore, the traditional lithium battery backup power solution has great defects.

[0003] Using supercapacitors as backup power circuits to replace traditional lithium batteries can meet general short-term backup power applications. Although the capacity of supercapacitors is still weaker than that of lithium batteries, they have a wide range of working environment temperatures and have a natural advantage for low-power IoT devices. In terms of cost, they are also more cost-effective than lithium batteries.

[0004] The invention patent with publication number CN 111416414 A discloses a supercapacitor charging and discharging control system and its charging and discharging control circuit. Its defects are: 1) The supercapacitor, which is an energy storage device, cannot determine whether it has been fully charged and needs to be charged using VIN all the time. This causes the supercapacitor to be in a state of constant charging and discharging, which shortens the service life of the supercapacitor. 2) The use of load resistor R1 as a current limiting charging circuit results in low charging efficiency, and the circuit requires heat dissipation design of the load resistor R1, which increases costs. 3) The discharge circuit is just a simple MOS switch, which causes the backup power supply to only decrease as the voltage of the supercapacitor decreases, and the output voltage is unstable, which does not meet the general backup power supply circuit requirements; and this results in poor energy storage utilization efficiency of the supercapacitor.

[0005] The invention patent with announcement number CN 104578366 B discloses a self-powered supercapacitor energy storage power supply for line fault detection. Its defects are: 1) The capacitor is directly connected to the supercapacitor, resulting in a large surge current, which is easy to damage the supercapacitor; the power supply is unstable at the moment of power-on. 2) The discharge circuit is just a simple MOS switch, which causes the backup power supply to decrease only as the voltage of the supercapacitor decreases, and the output voltage is unstable. 3) There is a lack of shutdown logic control, and the device can only be shut down when the supercapacitor is exhausted. This will cause the device to start and shut down continuously when the shutdown power supply voltage is at the critical value, which is easy to cause equipment failure.

[0006] The utility model patent with announcement number CN 208190326 U discloses a short-time backup power supply circuit. Its defects are: 1) It uses a special hot-swap controller chip LTC4218, which reduces the surge current, but the chip cost is too high and not cost-effective. 2) It uses a special buck-boost control chip LTC3110 to manage the charge and discharge of supercapacitors, but the chip cost is too high, not cost-effective, and not universal. Summary of the invention

[0007] The technical problem solved by the present invention is to provide a universal short-time backup power supply circuit, which realizes the charge and discharge management of the supercapacitor, the stable output of the discharge circuit, and the maximum utilization of the capacity of the supercapacitor.

[0008] The present invention is achieved through the following technical solutions:

[0009] A universal short-time backup power supply circuit comprises a first switch, a charging circuit, an energy storage device, a second switch, a discharge circuit and a main control module;

[0010] The power supply is connected to the charging circuit via the first switch, and the charging circuit is connected to the energy storage device; the energy storage device is connected to the discharge circuit via the second switch; the first switch is also connected to the discharge circuit via the power supply bypass; the discharge circuit supplies power to the electrical equipment and the main control module;

[0011] The first switch and the second switch are mutually exclusive switches; when the power supply is normal, the first switch is turned on and the second switch is turned off; when the power supply is off, the first switch is turned off and the second switch is turned on;

[0012] The input signal received by the main control module includes a power failure detection signal and a voltage detection signal of the energy storage device, and the signal output includes a charge enable for controlling the charging circuit to be turned on and a discharge enable for controlling the second switch to be turned on;

[0013] The charging enable is output by connecting the power failure detection signal pin of the power supply and the voltage control pin of the energy storage device of the main control module through a logic and switch; the charging enable is issued only when the power supply is detected to be powered and the voltage of the energy storage device is lower than the threshold, and the charging circuit is turned on to charge the energy storage device;

[0014] When the power is off, the energy storage device supplies power to the discharge circuit through the second switch, and the discharge enable keeps the second switch turned on; when the power-consuming device is powered off, the discharge enable controls the second switch to turn off.

[0015] The first switch includes a path switch and a control switch, the control switch is turned on when the power supply is normal, and the path switch is turned on; the control switch is turned off when the power supply is off, and the path switch is turned off;

[0016] The second switch includes a third switch and a fourth switch connected in series, and a diode is connected in parallel on both sides of the third switch; the third switch and the first switch are mutually exclusive, and the fourth switch is controlled by the main control module;

[0017] The fourth switch is turned on by default. At the moment of power failure, the energy storage device can supply power to the discharge circuit through the diode. After the third switch is turned on, the energy storage device supplies power to the discharge circuit through the third switch and the fourth switch.

[0018] The main control module controls the fourth switch to be disconnected, thereby cutting off the power supply.

[0019] The main control module controls the charging of the energy storage device as follows:

[0020] The main control module performs power failure detection in real time and collects the voltage of the energy storage device at regular intervals; if the received power failure detection signal indicates that there is power and the received energy storage device voltage detection signal is lower than the threshold voltage, the logic and switch are turned on, the charging enable is issued, and the switch in the charging circuit is turned on to charge the energy storage device; if the detected voltage of the supercapacitor is not less than the threshold, the logic and switch are not turned on and the charging circuit is closed.

[0021] The main control module controls the discharge of the energy storage device as follows:

[0022] The main control module defaults to keeping the fourth switch turned on;

[0023] If the received power failure detection signal is power failure, the discharge enable keeps the fourth switch turned on;

[0024] After power failure, the main control module also implements the following power failure protection strategy:

[0025] The current SOC power is estimated based on the voltage of the energy storage device collected, and the backup power supply duration is estimated in combination with the current of the power-consuming device. A warning is reported to the power-consuming device, prompting and / or setting low power consumption. When the voltage of the energy storage device is lower than the threshold, the power-consuming device is prompted to prepare for power-off.

[0026] When the electrical device is turned off, the discharge enable is controlled to close the fourth switch, thereby cutting off the power supply to the discharge circuit.

[0027] An RC delay circuit is also provided between the signal end of the discharge circuit and the first switch / the second switch, and is also connected to the main control module through the discharge circuit; the main control module also controls the discharge circuit to be turned on through reset enable to perform hardware power-on reset control:

[0028] When the power-off detection signal is powered, the main control module sends a reset to turn on the discharge circuit, the level of the discharge circuit signal end changes, the discharge circuit is turned off, and the entire circuit is powered off; after the main control module is powered off, the output reset enable changes to a low level, the discharge circuit is turned off, and after the power is supplied through the RC delay circuit, the level of the discharge circuit signal end is restored, the discharge circuit works again, and the power supply returns to normal.

[0029] The RC delay circuit ensures that when the power supply is powered, the discharge circuit is enabled, and the power supply supplies power to the power-consuming device through the first switch and the discharge circuit;

[0030] The duration of power-off in power-on reset can be configured and adjusted by the resistance and capacitance values ​​of the RC delay circuit.

[0031] The energy storage device is a supercapacitor. The main control module sets the fourth switch to remain turned on by default, and the third switch is connected in parallel with a diode. At the moment of power failure, the supercapacitor can supply power to the discharge circuit through the diode.

[0032] After power failure, the third switch is turned on, the first switch is turned off, the main control module detects the power failure signal, and keeps the fourth switch turned on to ensure that the supercapacitor supplies power to the charging circuit;

[0033] The charging circuit is a current limiting circuit or a current limiting chip; the discharging circuit is a boost circuit or a boost chip;

[0034] The threshold voltage does not exceed the rated voltage of the energy storage device.

[0035] The first switch includes a PMOS tube VT1 and an NMOS tube VT2, the source of VT1 is connected to the positive electrode of the power supply; the positive electrode of the power supply is connected to the gate of VT2 via a voltage divider resistor, the source of VT2 is grounded, and the drain of VT2 is connected to the gate of VT1; the drain of VT1 is respectively connected to the charging circuit and the discharging circuit; VT2 is turned on when the power supply is normal, and VT1 is turned on; VT2 is turned off when the power supply is off, and VT1 is turned off;

[0036] The charging circuit is a current limiting chip D1, which is connected to the first switch via a voltage dividing resistor, and its signal end is connected to the IO pin of the main control module to receive the charging enable signal EN_1 of the main control module;

[0037] The energy storage device is a super capacitor C1, whose positive electrode is connected to the output end of the charging circuit and the second switch respectively, and whose negative electrode is grounded; the super capacitor C1 is connected to the AD acquisition pin of the main control module so that the main control module can collect its voltage signal;

[0038] The second switch includes a pair of back-to-back PMOS tubes VT3 and VT5;

[0039] VT3 is the third switch, whose source is connected to the output end of the charging circuit, the drain is connected to the drain of VT5, and the gate is connected to the PNP transistor VT4 which is turned on by the reverse control of the power supply; the base of VT4 is connected to the positive pole of the power supply through a voltage divider resistor, the collector is grounded through a resistor, and the emitter is connected to the gate of VT3; VT3 realizes hardware mutual exclusion with the first switch through VT4; the parasitic diode between the source and drain of VT3 realizes a diode connected in parallel with the third switch;

[0040] VT5 is the fourth switch, whose gate is connected to the drain of NMOS tube VT6, and whose source is connected to the discharge circuit; the source of VT6 is grounded, and the gate is connected to the IO pin of the main control module, and receives the discharge enable signal EN_2 sent by the active module to realize the conduction control of VT5 by the main control module.

[0041] The discharge circuit is a DC / DC boost chip D2, whose input end is connected to the first switch and the second switch; the delay circuit includes a first RC delay circuit composed of a resistor R12 and a capacitor C4, and a second RC delay circuit composed of a resistor R14 and a capacitor C5; wherein the resistor R12 and the capacitor C4 are connected between the input power supply and the ground, and the resistor R14 and the capacitor C5 are connected between the main control module and the ground;

[0042] The discharge circuit includes an NMOS tube VT7 and a resistor R13, the source of the NMOS tube VT7 is connected to the resistor R12 via the resistor R13, and is also connected to the signal end of D1; the resistor R13 and the NMOS tube VT7 can discharge the level of the first RC circuit, so that the enablement of the discharge circuit is controllable; the drain of VT7 is grounded, the gate of VT7 is connected to the resistor R14 via the resistor R15, and the other end of the resistor R14 is connected to the IO pin of the main control module, and receives the reset enable signal EN_3 to control the conduction and cutoff of VT7, so as to control whether the discharge circuit is enabled or not.

[0043] The main control module is an MCU D3 with an internally integrated crystal oscillator circuit, and its power supply part includes a power supply circuit and a power-on reset circuit; the power supply circuit includes power filter capacitors C22 and C23 connected to the power pin of MCU D3; the power-on reset circuit includes a resistor R21 and a capacitor C21 connected to the NRST pin of MCU D3 and forming an RC circuit for power-on reset;

[0044] Resistors R22 and R23 form a voltage divider circuit for power input, which is connected to the PB0 pin of MCU D3 and serves as the input signal for power failure detection of the main control module;

[0045] Resistors R24 and R25 form the voltage divider input of the supercapacitor, which is connected to the PB1 pin of MCU D3 and serves as the AD input signal for the main control module to collect the voltage of the energy storage device;

[0046] The PC4 pin of MCU D3 is used as a charging enable pin, outputting a charging enable signal EN_1;

[0047] The PC1 pin of MCU D3 is used as a discharge enable pin, and outputs a discharge enable signal EN_2;

[0048] The PC0 pin of MCU D3 is used as a power-off reset pin and outputs a reset enable signal EN_3.

[0049] Compared with the prior art, the present invention has the following beneficial technical effects:

[0050] The present invention collects the voltage of the energy storage device (supercapacitor) and detects power failure, and effectively manages the charging of the supercapacitor through the logic and control strategy of the main control module, thereby ensuring the voltage of the supercapacitor and the power of the backup power supply; at the same time, it avoids excessive use of the supercapacitor and ensures the life of the supercapacitor; the discharge circuit performs a boost process to ensure the voltage stability of the output power supply and fully and effectively utilize the energy storage capacity of the supercapacitor;

[0051] The present invention increases and improves the shutdown control of the backup power supply circuit, ensures the universal applicability and cost-effectiveness of the circuit, ensures that the power supply does not have a critical shutdown voltage state, and avoids the device from constantly starting and shutting down, which can easily cause equipment failure. At the same time, through the delay circuit and the discharge circuit, as well as the reset enable control of the main control module, under normal power supply conditions, the hardware power-off and power-on reset function is realized, which is more reliable than the traditional software reset. Furthermore, the present invention can monitor the voltage of the energy storage device in real time, and estimate the SOC capacity of the energy storage device, and can perform strategic management according to the capacity; and perform automatic power-off and power-on switching of charging and discharging, etc.; and can also control the shutdown of the backup power supply through discharge enable according to the needs of the main control.

[0052] The present invention can use a universal supercapacitor as a short-term energy storage device to replace a traditional lithium battery. The output power of the discharge circuit of the present invention is stable, which meets the requirements of a stable voltage input of a general master control or circuit. The application of the circuit is universal. For general short-term power-off protection equipment, it is more suitable to use this universal replacement, thereby having more advantages in terms of cost and performance.

[0053] In the prior art, the application of supercapacitors as backup power sources has neither charging nor discharging management, nor stable output of the discharge circuit. The capacity of the supercapacitor has not been fully utilized, and there is a lack of shutdown function. The universal versatility required for circuit application has not been achieved, and the hardware power-off and power-on reset function is not available. The present invention undoubtedly has a significant effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is a circuit diagram of the present invention;

[0055] Figure 2 is a second switch schematic diagram of the present invention;

[0056] Figure 3 A schematic diagram of enabling control of a control module of the present invention;

[0057] Figure 4 It is a circuit connection schematic diagram of the present invention;

[0058] Figure 5 It is a schematic diagram of the circuit connection of the main control module of the present invention. DETAILED DESCRIPTION

[0059] The present invention is further described in detail below in conjunction with the embodiments, which are intended to explain the present invention rather than to limit it.

[0060] See also Figure 1-Figure 5 , a universal short-time backup power supply circuit, comprising a first switch, a charging circuit, an energy storage device, a second switch, a discharge circuit and a main control module;

[0061] The power supply is connected to the charging circuit via the first switch, and the charging circuit is connected to the energy storage device; the energy storage device is connected to the discharge circuit via the second switch; the first switch is also connected to the discharge circuit via the power supply bypass; the discharge circuit supplies power to the electrical equipment and the main control module;

[0062] The first switch and the second switch are mutually exclusive switches; when the power supply is normal, the first switch is turned on and the second switch is turned off; when the power supply is off, the first switch is turned off and the second switch is turned on;

[0063] The input signal received by the main control module includes a power failure detection signal and a voltage detection signal of the energy storage device, and the signal output includes a charge enable for controlling the charging circuit to be turned on and a discharge enable for controlling the second switch to be turned on;

[0064] The charging enable is output by connecting the power failure detection signal pin of the power supply and the voltage control pin of the energy storage device of the main control module through a logic and switch; the charging enable is issued only when the power supply is detected to be powered and the voltage of the energy storage device is lower than the threshold, and the charging circuit is turned on to charge the energy storage device;

[0065] When the power is off, the energy storage device supplies power to the discharge circuit through the second switch, and the discharge enable keeps the second switch turned on; when the power-consuming device is powered off, the discharge enable controls the second switch to turn off.

[0066] The first switch includes a path switch and a control switch, the control switch is turned on when the power supply is normal, and the path switch is turned on; the control switch is turned off when the power supply is off, and the path switch is turned off;

[0067] The second switch includes a third switch and a fourth switch connected in series, and a diode is connected in parallel on both sides of the third switch; the third switch and the first switch are mutually exclusive, and the fourth switch is controlled by the main control module;

[0068] The fourth switch is turned on by default. At the moment of power failure, the energy storage device can supply power to the discharge circuit through the diode. After the third switch is turned on, the energy storage device supplies power to the discharge circuit through the third switch and the fourth switch.

[0069] The main control module controls the fourth switch to be disconnected, thereby cutting off the power supply.

[0070] An RC delay circuit is also provided between the signal end of the discharge circuit and the first switch / the second switch, and is also connected to the main control module through the discharge circuit; the main control module also controls the discharge circuit to be turned on through reset enable to perform hardware power-on reset control:

[0071] When the power-off detection signal is powered, the main control module sends a reset to turn on the discharge circuit, the level of the discharge circuit signal end changes, the discharge circuit is turned off, and the entire circuit is powered off; after the main control module is powered off, the output reset enable changes to a low level, the discharge circuit is turned off, and after the power is supplied through the RC delay circuit, the level of the discharge circuit signal end is restored, the discharge circuit works again, and the power supply returns to normal.

[0072] The various parts of the present invention are described in detail below in conjunction with the accompanying drawings.

[0073] See also Figure 1 The universal short-time backup power supply circuit of the present invention is composed of the following parts:

[0074] 1. First switch, 2. Charging circuit (current limiting), 3. Energy storage device (supercapacitor), 4. Second switch, 5. Discharge circuit (boost), 6. Main control module (MCU or IoT module).

[0075] The power supply VIN comes in from the first switch, and then has two flow paths, one to the charging circuit and the other to the power supply bypass. The charging circuit (current limiting) charges the energy storage device (supercapacitor). The power supply bypass is directly connected to the discharge circuit (boost), which is boosted by the discharge circuit and used as the main power supply VCC. VCC supplies power to the main control module and can also supply power to other circuits of the device. In the event of power failure, the energy storage device (supercapacitor) can supply power to the discharge circuit through the second switch to ensure normal power supply of the device.

[0076] The first switch and the second switch are hardware mutually exclusive switches, which ensure that the energy storage device (supercapacitor) will not be charged directly when charging, and can only be charged through the charging circuit when it is needed; and when the external power supply is turned off, the first switch is turned off, which can ensure that when the second switch is turned on, no current is fed back to the input power supply VIN terminal.

[0077] The first switch is turned on / off by the external power supply. When the external power supply is powered, the first switch is turned on. When the external power supply is powered off, the first switch is turned off.

[0078] The second switch includes a pair of dual switches connected in series, such as back-to-back switches using PMOS tubes; Figure 2 As shown, the third switch realizes mutual exclusion with the first switch, and a diode is connected in parallel to the third switch; the fourth switch is controlled by the main control module and is turned on by default. This ensures that when the external power supply is cut off, the super capacitor can first supply power to the discharge circuit through the diode to ensure that the power supply of the device will not be cut off; and when the shutdown operation is required, the main control module controls the fourth switch to be disconnected, that is, the power supply can be cut off.

[0079] The enabling control of the charging circuit (current limiting) is achieved by connecting the external power-off detection signal and the control pin of the main control module through hardware logic AND operation, ensuring that the charging circuit (current limiting) can only control the charging enable by sending a charging signal through the main control module when the external power supply is powered.

[0080] The charging circuit (current limiting) is a circuit for charging the supercapacitor. It has a charging enable switch, which mainly has the function of current limiting to prevent the instantaneous current of the input VIN power supply from being too large and protect the power supply voltage. Generally, a current limiting switch is sufficient, and the current limiting size is the charging current size of the supercapacitor.

[0081] See also Figure 3 , the main control module controls the charging of the energy storage device as follows:

[0082] The main control module performs power failure detection in real time and collects the voltage of the energy storage device at regular intervals; if the received power failure detection signal indicates that there is power and the received energy storage device voltage detection signal is lower than the threshold voltage, the logic and switch are turned on, the charging enable is issued, and the switch in the charging circuit is turned on to charge the energy storage device; if the detected voltage of the supercapacitor is not less than the threshold, the logic and switch are not turned on and the charging circuit is closed.

[0083] The main control module controls the discharge of the energy storage device as follows:

[0084] The main control module defaults to keeping the fourth switch turned on;

[0085] If the received power failure detection signal is power failure, the discharge enable keeps the fourth switch turned on;

[0086] After power failure, the main control module also implements the following power failure protection strategy:

[0087] The current SOC power is estimated based on the voltage of the energy storage device collected, and the backup power supply duration is estimated in combination with the current of the power-consuming device. A warning is reported to the power-consuming device, prompting and / or setting low power consumption. When the voltage of the energy storage device is lower than the threshold, the power-consuming device is prompted to prepare for power-off.

[0088] When the electrical device is turned off, the discharge enable is controlled to close the fourth switch, thereby cutting off the power supply to the discharge circuit.

[0089] Specifically, the main control module (single-chip microcomputer or Internet of Things module) is responsible for collecting the voltage of the energy storage device (supercapacitor) and power-off detection (using an IO port of the main control module as a pin for detecting power-off signals. When the external power supply has power, the detection pin is high (or low), and when the external power supply is powered off, it is the opposite; thus, the level is used to detect whether the power is off or not). Through the collected signals, the control module performs charging management, discharging management, and shutdown actions of the energy storage device.

[0090] Control 1 (enable 1) controls the charging of the energy storage device (supercapacitor): if the power failure signal is detected as having power and the collected voltage of the energy storage device is lower than the threshold voltage, control 1 is enabled for charging, otherwise it is not charged; the threshold voltage does not exceed the rated voltage of the energy storage device, for example, if the supercapacitor is 2.7V, the threshold is 2.6V, and 0.1V is reserved for derating protection.

[0091] Control 2 (enable 2) performs discharge control of the energy storage device (supercapacitor): when the power failure signal is detected as power failure, enable 2 controls the fourth switch to be turned on; wherein the fourth switch is turned on by default during the initial power-on period, to ensure that the backup power supply can be powered on through the second switch at the moment of power failure.

[0092] When it is detected that the external power supply has been powered off, the device has completed the pre-power-off processing task and meets the shutdown conditions, enabling 2 to close the fourth switch to cut off the power supply.

[0093] Control 3 (enable 3) performs hardware power-off and power-on reset control. When the external power supply is detected as powered, the control signal is output, the discharge circuit (boost) is turned off, and the entire circuit is powered off directly; after the main control module is powered off, the output control signal automatically changes to a low level, and the external power supply recharges the enable signal to a high level through a universal RC delay circuit, the discharge circuit (boost) works again, and the power supply returns to normal. The power-off duration can be configured and adjusted through the resistance and capacitance values ​​of RC; and the RC delay circuit ensures that the discharge circuit (boost) is enabled when the external power supply is powered.

[0094] The RC delay circuit ensures that when the power supply is powered, the discharge circuit is enabled, and the power supply supplies power to the power-consuming device through the first switch and the discharge circuit;

[0095] The duration of power-off in power-on reset can be configured and adjusted by the resistance and capacitance values ​​of the RC delay circuit.

[0096] The main control module is responsible for collecting the voltage of the supercapacitor. Since the voltage and SOC of the supercapacitor are in linear proportion, the SOC of the supercapacitor can be directly estimated, so that the corresponding power consumption of the product can be managed and estimated, and the final operating time of the equipment can be managed.

[0097] The following describes four usage scenarios:

[0098] 1. External power supply is normal

[0099] The external power supply passes through the first switch from VIN and then through the discharge circuit (boost) to power the device. After the main control module is powered on, it starts to work, collects the voltage of the energy storage device (supercapacitor), and performs power-off detection. The first switch is enabled by default, and the power is turned on by default; otherwise, the power is turned off; the discharge circuit (boost) is enabled by default, and the power is enabled by default. In this way, the main control module can be turned on normally when the external power supply is powered.

[0100] 2. Supercapacitor charging management

[0101] After the main control module is powered on, it starts to perform charge and discharge management. After detecting the external power failure signal and collecting the voltage of the supercapacitor, it calculates that the supercapacitor is not fully charged to the threshold, and then turns on the charging circuit for charging. And it keeps detecting signals until the voltage of the supercapacitor is higher than the threshold, and then starts to turn off the charging circuit.

[0102] At present, the rated voltage specifications of common supercapacitors on the market are 2.7V, 3V, 3.3V, 3.6V, 5.4V, 5.5V, and 7.5V, and the corresponding rated capacitance ranges from 33mF to 470F. It is necessary to ensure that the charging voltage of the supercapacitor does not exceed the rated voltage according to the rated voltage of the selected supercapacitor, otherwise the supercapacitor will be damaged.

[0103] The formula for the charge of a supercapacitor is: charge = capacitance * voltage across the capacitor, i.e., Q = C * U. The charge and voltage across the capacitor are linearly related. As long as the voltage of the supercapacitor is detected, it can be determined whether the supercapacitor is fully charged. Therefore, the comparison threshold during charging is the corresponding rated voltage of the selected supercapacitor. When the voltage of the supercapacitor is collected and compared with the rated voltage, it is fully charged if it is not less than the rated voltage.

[0104] The main control module periodically detects the voltage of the supercapacitor. If it is lower than the threshold, the charging circuit is reopened for charging. If the voltage of the supercapacitor is higher than the threshold, the charging circuit is closed.

[0105] 3. External power failure

[0106] When the external power supply VIN is powered off, because the third switch has a parallel diode, and the fourth switch is turned on by default by the main control module, the super capacitor can ensure that the power supply of the device remains powered through the diode at the moment of power failure.

[0107] After the main control module detects the power-off signal, it turns on the third switch to ensure that the supercapacitor supplies power to the charging circuit. Then the main control module calculates and estimates the current SOC power according to the collected supercapacitor voltage and takes corresponding actions.

[0108] The corresponding actions include calculating and testing the backup power supply duration, reporting alarms in a timely manner and making corresponding low-power settings, extending the backup power supply duration as much as possible, and providing corresponding power-off protection strategies.

[0109] The current power can be calculated based on the voltage of the supercapacitor, and the formula for power and current is: Power = Current * Time, that is, Q = I * t. According to the device's own current size I (rated working current size), the time t that the device can continue to work, that is, the power supply duration t, can be calculated. By detecting the power-off detection signal and determining that the current working state is a power-off state, a power-off alarm can be reported; and corresponding low-power setting prompts and settings are performed: for example, the main frequency of the main control module is configured to be reduced, and unnecessary peripheral functions are reduced or turned off to achieve the lowest power consumption to achieve the most basic device functions and to extend the use time of the backup power supply as much as possible; in addition, before the device reaches the power supply duration t, power-off protection is set, such as saving relevant data and logs, and turning off the read and write operations of the memory to avoid the production of bad blocks of the memory due to power failure during reading and writing.

[0110] 4. Hardware power failure and power-on reset

[0111] When the main control module needs to perform a power-off reset, the discharge circuit is turned off by controlling 3 to achieve the effect of turning off the power supply. After the RC delay circuit, the discharge circuit is used again, and the main control module and the power supply resume normal power supply.

[0112] Under normal power supply conditions, the hardware power-off and power-on reset function is realized, which is more reliable than the traditional software reset.

[0113] See also Figure 4 , Figure 5 , specific embodiments are given below.

[0114] The first switch includes a PMOS tube VT1 and an NMOS tube VT2, the source of VT1 is connected to the positive electrode of the power supply; the positive electrode of the power supply is connected to the gate of VT2 via a voltage divider resistor, the source of VT2 is grounded, and the drain of VT2 is connected to the gate of VT1; the drain of VT1 is respectively connected to the charging circuit and the discharging circuit; VT2 is turned on when the power supply is normal, and VT1 is turned on; VT2 is turned off when the power supply is off, and VT1 is turned off;

[0115] The charging circuit is a current limiting chip D1, which is connected to the first switch via a voltage dividing resistor, and its signal end is connected to the IO pin of the main control module to receive the charging enable signal EN_1 of the main control module;

[0116] The energy storage device is a super capacitor C1, whose positive electrode is connected to the output end of the charging circuit and the second switch respectively, and whose negative electrode is grounded; the super capacitor C1 is connected to the AD acquisition pin of the main control module so that the main control module can collect its voltage signal;

[0117] The second switch includes a pair of back-to-back PMOS tubes VT3 and VT5;

[0118] VT3 is the third switch, whose source is connected to the output end of the charging circuit, the drain is connected to the drain of VT5, and the gate is connected to the PNP transistor VT4 which is turned on by the reverse control of the power supply; the base of VT4 is connected to the positive pole of the power supply through a voltage divider resistor, the collector is grounded through a resistor, and the emitter is connected to the gate of VT3; VT3 realizes hardware mutual exclusion with the first switch through VT4; the parasitic diode between the source and drain of VT3 realizes a diode connected in parallel with the third switch;

[0119] VT5 is the fourth switch, whose gate is connected to the drain of NMOS tube VT6, and whose source is connected to the discharge circuit; the source of VT6 is grounded, and the gate is connected to the IO pin of the main control module, and receives the discharge enable signal EN_2 sent by the active module to realize the conduction control of VT5 by the main control module.

[0120] The discharge circuit is a DC / DC boost chip D2, whose input end is connected to the first switch and the second switch; the delay circuit includes a first RC delay circuit composed of a resistor R12 and a capacitor C4, and a second RC delay circuit composed of a resistor R14 and a capacitor C5; wherein the resistor R12 and the capacitor C4 are connected between the input power supply and the ground, and the resistor R14 and the capacitor C5 are connected between the main control module and the ground;

[0121] The discharge circuit includes an NMOS tube VT7 and a resistor R13, the source of the NMOS tube VT7 is connected to the resistor R12 via the resistor R13, and is also connected to the signal end of D1; the resistor R13 and the NMOS tube VT7 can discharge the level of the first RC circuit, so that the enablement of the discharge circuit is controllable; the drain of VT7 is grounded, the gate of VT7 is connected to the resistor R14 via the resistor R15, and the other end of the resistor R14 is connected to the IO pin of the main control module, and receives the reset enable signal EN_3 to control the conduction and cutoff of VT7, so as to control whether the discharge circuit is enabled or not.

[0122] The main control module is an MCU D3 with an internally integrated crystal oscillator circuit, and its power supply part includes a power supply circuit and a power-on reset circuit; the power supply circuit includes power filter capacitors C22 and C23 connected to the power pin of MCU D3; the power-on reset circuit includes a resistor R21 and a capacitor C21 connected to the NRST pin of MCU D3 and forming an RC circuit for power-on reset;

[0123] Resistors R22 and R23 form a voltage divider circuit for power input, which is connected to the PB0 pin of MCU D3 and serves as the input signal for power failure detection of the main control module;

[0124] Resistors R24 and R25 form the voltage divider input of the supercapacitor, which is connected to the PB1 pin of MCU D3 and serves as the AD input signal for the main control module to collect the voltage of the energy storage device;

[0125] The PC4 pin of MCU D3 is used as a charging enable pin, outputting a charging enable signal EN_1;

[0126] The PC1 pin of MCU D3 is used as a discharge enable pin, and outputs a discharge enable signal EN_2;

[0127] The PC0 pin of MCU D3 is used as a power-off reset pin and outputs a reset enable signal EN_3.

[0128] Specifically, a specific usage example is given below.

[0129] 1: The first switch. Use PMOS tube VT1 as the switch for power path conduction; VIN input power is divided by resistors R1 and R2, and then the gate of NMOS tube VT2 is controlled, thereby controlling VT2 conduction; the drain of VT2 is connected to the gate of VT1, thereby controlling VT1 conduction. Ensure that VT2 can be turned on when the VIN power supply is normal; thereby turning on VT1.

[0130] 2: Charging circuit (current limiting), using the current limiting chip D1, specifically select the current limiting protection switch chip MT9700 of Xi'an Aerospace Minxin, the current limiting can be configured by configuring the resistor R6. Alternatively, you can choose a common buck DC / DC chip in the market to ensure that the current and voltage of the charging circuit meet the rated specifications of the back-end energy storage device. Among them, R4 and R5 are voltage divider resistors, which serve as the enable signal EN_1 of D1. This enable signal is connected to the IO pin of the main control module to realize the control of the main control module.

[0131] 3: Energy storage device (supercapacitor). C1 is an energy storage device. You can choose Emerald's supercapacitor, 100F / 2.7V. You can also choose other brands and specifications. The key is to match the output voltage of the charging circuit according to the rated voltage of the supercapacitor. Otherwise, the supercapacitor will be damaged due to exceeding the rated voltage or the rated voltage will not be reached and the capacity of the supercapacitor cannot be 100% utilized. The supercapacitor needs to be connected to the main control module, and the signal C_VOL is connected to the AD acquisition pin of the main control module to ensure that the main control module can collect the voltage of the supercapacitor and obtain the energy storage capacity of the supercapacitor.

[0132] 4: The second switch. A pair of back-to-back PMOS tubes, VT3 and VT5, are used as power path switches. VT4 is a PNP transistor, which is used to control the conduction of VT3; the VIN input power supply is divided by resistors R7 and R8, and the conduction of VT4 is controlled inversely, thereby realizing the conduction control of VT3. In this way, the hardware mutual exclusion function of the VIN input power supply and the second switch can be realized. There is a parasitic diode between the source pin 2 and the drain pin 3 of VT3, which directly realizes the function of the parallel diode of the third switch. VT6 is an NMOS tube, and the gate control end is the signal EN_2, which needs to be connected to the IO pin of the main control module to realize the control of the main control module; the drain pin 3 of VT6 is connected to the gate of VT5 to control the conduction of VT5, thereby realizing the control of the second switch.

[0133] 5: Discharge circuit (boost). D2 is a DC / DC boost chip, and the HX3001 from Hexin Microelectronics is used here. Resistor R12 and capacitor C4 form an RC power-on delay circuit; resistor R13 and NMOS tube VT7 can discharge the level of the RC circuit, thereby ensuring that the D2 discharge chip can be enabled and controlled; resistor R14 and capacitor C5 form another RC power-on delay circuit; one end of R14 is connected to the IO pin of the main control module to control the conduction and cutoff of VT7, thereby controlling whether D2 is enabled or not.

[0134] 6: Main control module. Figure 5 D3 uses STMicroelectronics' STM8L051F3 as the main control MCU. The minimum system of the main control includes two parts: power supply and power-on reset circuit. The crystal oscillator circuit has been integrated inside the MCU. Capacitors C22 and C23 are the power filter capacitors of the MCU, connected to the power pin of D3. Resistor R21 and capacitor C21 are the RC circuit of power-on reset, connected to the NRST pin of D3. Resistors R22 and R23 form a voltage divider circuit for external power input, connected to the PB0 pin of D3, and used as the external power supply power-off detection of the MCU. Resistors R24 and R25 are used to divide the voltage input of the supercapacitor, connected to the PB1 pin of D3, and used as the ADC voltage acquisition of the MCU to collect the voltage of the supercapacitor. The PC4 pin of D3 is used as the charging control enable pin; the PC1 pin of D3 is used as the shutdown enable pin of the entire power supply; the PC0 pin of D3 is used as the hardware power-off reset function pin.

[0135] The above embodiments are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions and substitutions made by those skilled in the art based on the technical features of the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A general short-time backup power supply circuit, characterized in that: It includes a first switch, a charging circuit, an energy storage device, a second switch, a discharge circuit and a main control module; The power supply is connected to the charging circuit via the first switch, and the charging circuit is connected to the energy storage device; the energy storage device is connected to the discharge circuit via the second switch; the first switch is also connected to the discharge circuit via the power supply bypass; the discharge circuit supplies power to the electrical equipment and the main control module; The first switch and the second switch are mutually exclusive switches; when the power supply is normal, the first switch is turned on and the second switch is turned off; when the power supply is off, the first switch is turned off and the second switch is turned on; The input signal received by the main control module includes a power failure detection signal and a voltage detection signal of the energy storage device, and the signal output includes a charge enable for controlling the charging circuit to be turned on and a discharge enable for controlling the second switch to be turned on; The charging enable is output by connecting the power failure detection signal pin of the power supply and the voltage control pin of the energy storage device of the main control module through a logic and switch; the charging enable is issued only when the power supply is detected to be powered and the voltage of the energy storage device is lower than the threshold, and the charging circuit is turned on to charge the energy storage device; When the power supply is cut off, the energy storage device supplies power to the discharge circuit through the second switch, and the discharge enable keeps the second switch turned on; when the power-consuming device is powered off, the discharge enable controls the second switch to turn off; The first switch includes a path switch and a control switch, the control switch is turned on when the power supply is normal, and the path switch is turned on; the control switch is turned off when the power supply is off, and the path switch is turned off; The second switch includes a third switch and a fourth switch connected in series, and a diode is connected in parallel on both sides of the third switch; the third switch and the first switch are mutually exclusive, and the fourth switch is controlled by the main control module; The fourth switch is turned on by default. At the moment of power failure, the energy storage device can supply power to the discharge circuit through the diode. After the third switch is turned on, the energy storage device supplies power to the discharge circuit through the third switch and the fourth switch. The main control module controls the fourth switch to be disconnected, thereby cutting off the power supply; The main control module controls the charging of the energy storage device as follows: The main control module performs power failure detection in real time and collects the voltage of the energy storage device at regular intervals; if the received power failure detection signal indicates that there is power and the received energy storage device voltage detection signal is lower than the threshold voltage, the logic and switch are turned on, the charging enable is issued, and the switch in the charging circuit is turned on to charge the energy storage device; if the detected voltage of the supercapacitor is not less than the threshold, the logic and switch are not turned on and the charging circuit is closed; The main control module controls the discharge of the energy storage device as follows: The main control module defaults to keeping the fourth switch turned on; If the received power failure detection signal is power failure, the discharge enable keeps the fourth switch turned on; After power failure, the main control module also implements the following power failure protection strategy: The current SOC power is estimated based on the voltage of the energy storage device collected, and the backup power supply duration is estimated in combination with the current of the power-consuming device. A warning is reported to the power-consuming device, prompting and / or setting low power consumption. When the voltage of the energy storage device is lower than the threshold, the power-consuming device is prompted to prepare for power-off. When the electrical equipment is turned off, the discharge enable is controlled to close the fourth switch, thereby cutting off the power supply to the discharge circuit; An RC delay circuit is also provided between the signal end of the discharge circuit and the first switch / the second switch, and is also connected to the main control module through the discharge circuit; the main control module also controls the discharge circuit to be turned on through reset enable to perform hardware power-on reset control: When the power-off detection signal is powered, the main control module sends a reset to turn on the discharge circuit, the level of the discharge circuit signal end changes, the discharge circuit is turned off, and the entire circuit is powered off; after the main control module is powered off, the output reset enable changes to a low level, the discharge circuit is turned off, and after the power is supplied through the RC delay circuit, the level of the discharge circuit signal end is restored, the discharge circuit works again, and the power supply returns to normal.

2. The universal short-time backup power supply circuit according to claim 1, characterized in that: The RC delay circuit ensures that when the power supply is powered, the discharge circuit is enabled, and the power supply supplies power to the power-consuming device through the first switch and the discharge circuit; The duration of power-off in power-on reset can be configured and adjusted by the resistance and capacitance values ​​of the RC delay circuit.

3. The universal short-time backup power supply circuit according to claim 1, characterized in that: The energy storage device is a supercapacitor. The main control module sets the fourth switch to remain turned on by default, and the third switch is connected in parallel with a diode. At the moment of power failure, the supercapacitor can supply power to the discharge circuit through the diode. After power failure, the third switch is turned on, the first switch is turned off, the main control module detects the power failure signal, and keeps the fourth switch turned on to ensure that the supercapacitor supplies power to the charging circuit; The charging circuit is a current limiting circuit or a current limiting chip; the discharging circuit is a boost circuit or a boost chip; The threshold voltage does not exceed the rated voltage of the energy storage device.

4. The universal short-time backup power supply circuit as claimed in claim 1, characterized in that: The first switch includes a PMOS tube VT1 and an NMOS tube VT2, the source of VT1 is connected to the positive electrode of the power supply; the positive electrode of the power supply is connected to the gate of VT2 via a voltage divider resistor, the source of VT2 is grounded, and the drain of VT2 is connected to the gate of VT1; the drain of VT1 is respectively connected to the charging circuit and the discharging circuit; VT2 is turned on when the power supply is normal, and VT1 is turned on; VT2 is turned off when the power supply is off, and VT1 is turned off; The charging circuit is a current limiting chip D1, which is connected to the first switch via a voltage dividing resistor, and its signal end is connected to the IO pin of the main control module to receive the charging enable signal EN_1 of the main control module; The energy storage device is a super capacitor C1, whose positive electrode is connected to the output end of the charging circuit and the second switch respectively, and whose negative electrode is grounded; the super capacitor C1 is connected to the AD acquisition pin of the main control module so that the main control module can collect its voltage signal; The second switch includes a pair of back-to-back PMOS tubes VT3 and VT5; VT3 is the third switch, whose source is connected to the output end of the charging circuit, the drain is connected to the drain of VT5, and the gate is connected to the PNP transistor VT4 which is turned on by the reverse control of the power supply; the base of VT4 is connected to the positive pole of the power supply through a voltage divider resistor, the collector is grounded through a resistor, and the emitter is connected to the gate of VT3; VT3 realizes hardware mutual exclusion with the first switch through VT4; the parasitic diode between the source and drain of VT3 realizes a diode connected in parallel with the third switch; VT5 is the fourth switch, whose gate is connected to the drain of NMOS tube VT6, and whose source is connected to the discharge circuit; the source of VT6 is grounded, and the gate is connected to the IO pin of the main control module, and receives the discharge enable signal EN_2 sent by the active module to realize the conduction control of VT5 by the main control module.

5. The universal short-time backup power supply circuit according to claim 1, characterized in that: Said The discharge circuit is a DC / DC boost chip D2, whose input end is connected to the first switch and the second switch; the delay circuit includes a first RC delay circuit composed of a resistor R12 and a capacitor C4, and a second RC delay circuit composed of a resistor R14 and a capacitor C5; wherein the resistor R12 and the capacitor C4 are connected between the input power supply and the ground, and the resistor R14 and the capacitor C5 are connected between the main control module and the ground; The discharge circuit includes an NMOS tube VT7 and a resistor R13, the source of the NMOS tube VT7 is connected to the resistor R12 via the resistor R13, and is also connected to the signal end of D1; the resistor R13 and the NMOS tube VT7 can discharge the level of the first RC circuit, so that the enablement of the discharge circuit is controllable; the drain of VT7 is grounded, the gate of VT7 is connected to the resistor R14 via the resistor R15, and the other end of the resistor R14 is connected to the IO pin of the main control module, and receives the reset enable signal EN_3 to control the conduction and cutoff of VT7, so as to control whether the discharge circuit is enabled or not.

6. The universal short-time backup power supply circuit according to claim 4 or 5, characterized in that: The main control module is an MCU D3 with an internally integrated crystal oscillator circuit, and its power supply part includes a power supply circuit and a power-on reset circuit; the power supply circuit includes power filter capacitors C22 and C23 connected to the power pin of MCU D3; the power-on reset circuit includes a resistor R21 and a capacitor C21 connected to the NRST pin of MCU D3 and forming an RC circuit for power-on reset; Resistors R22 and R23 form a voltage divider circuit for power input, which is connected to the PB0 pin of MCU D3 and serves as the input signal for power failure detection of the main control module; Resistors R24 and R25 form the voltage divider input of the supercapacitor, which is connected to the PB1 pin of MCU D3 and serves as the AD input signal for the main control module to collect the voltage of the energy storage device; The PC4 pin of MCU D3 is used as a charging enable pin, outputting a charging enable signal EN_1; The PC1 pin of MCU D3 is used as a discharge enable pin, and outputs a discharge enable signal EN_2; The PC0 pin of MCU D3 is used as a power-off reset pin and outputs a reset enable signal EN_3.

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