Battery-free power supply method and circuit

Abstract

The present invention belongs to the field of circuit design, and specifically relates to a battery-free power supply method and circuit. In the present invention, the EN (enable) pin of the power chip is controlled by two voltage signals. When the power chip is in the off state, if the energy storage capacitor is charged at this time, the input voltage of the power chip is divided by a resistor, and then the power chip is controlled through the EN pin to start after the supercapacitor stores more electricity; when the power chip works normally, its output voltage is fed back to the EN pin to form a "self-locking" function to prevent the power chip from being shut down in advance during the discharge of the supercapacitor; when the input voltage of the power chip gradually drops to the chip startup threshold, the circuit is automatically "unlocked" to ensure that it can start normally again during the next charging process. The circuit design provided by the invention has low cost and low power consumption, solves the problem of power startup when the charging device is in a low-power state, and can also make full use of the power stored in the supercapacitor.

Description

Technical Field

[0001] The invention belongs to the field of circuit design, and in particular relates to a battery-free power supply method and circuit. Background Art

[0002] Solar energy is a renewable energy source, which is generally used to generate electricity or provide energy for water heaters. When solar energy is used as an energy source, a power circuit consisting of solar panels + super capacitors + power chips is generally used. The simplest low-cost circuit structure is Figure 1 shown.

[0003] At this time, the main function of the voltage regulator D1 is to limit the output voltage of the solar panel to prevent it from exceeding the operating voltage allowed by the subsequent supercapacitor; the main function of the diode D2 is to prevent the electricity stored in the supercapacitor from leaking back to the previous device, causing unnecessary increase in static power consumption.

[0004] For example, the maximum allowable working voltage of the supercapacitor is 5.5V. A solar panel with a normal working voltage greater than 5.5V can be selected, and then D1 and D2 can be used to limit its final output voltage to below 5.5V. Since the amount of electricity stored in the capacitor is Q = C (capacitance value) × U (voltage across both ends), in order to ensure that the supercapacitor can store more electricity, the voltage limit of the solar panel can be as close as possible to the maximum working voltage of the capacitor, 5.5V.

[0005] Ideally, when the solar panel charges the supercapacitor, the voltage of the supercapacitor gradually increases. When it increases to the startup threshold of the power chip, the power chip can provide power output VCC to the subsequent circuit. When the light intensity received by the solar panel decreases to a certain level, the operating voltage and current of the solar panel will drop to a certain value and can no longer charge the supercapacitor. The leakage of the supercapacitor, the static current of the power chip and the current consumed by the subsequent circuit will consume the energy stored in the supercapacitor, and the voltage of the supercapacitor will also drop accordingly. When it drops to the shutdown threshold of the power chip, the power chip stops working.

[0006] However, in actual application scenarios, in order to better optimize product costs and mechanical size, people tend to choose small-sized solar panels. At this time, the output power of the solar panels will decrease. In general circuits, whether it is the capacitors inside the power chip and peripheral devices or the capacitors in the subsequent load circuits, they will consume a large current at the moment of startup. At this time, the voltage of the supercapacitor just reaches the power startup threshold. If the solar panel cannot provide a certain current at this time due to the limitation of its own output power characteristics or changes in the external environment (such as changes in light intensity, changes in the illuminated area, etc.), it may cause the supercapacitor voltage to drop below the shutdown voltage of the power chip, and the power chip will not be able to start normally. The above process may be repeated continuously, that is, the supercapacitor voltage continues to change between the power startup threshold and the shutdown threshold, showing a phenomenon similar to "hiccups", resulting in the entire product being unable to power on and work normally. Summary of the invention

[0007] In view of this, an object of the present invention is to provide a battery-free power supply method.

[0008] In the present invention, the EN (enable) pin of the power chip is controlled by two voltage signals. When the power chip is in the off state, if the energy storage capacitor is charged at this time, the input voltage of the power chip is divided by a resistor, and then the power chip is controlled through the EN pin to start again after the supercapacitor stores more electricity; when the power chip works normally, its output voltage is fed back to the EN pin to form a "self-locking" function to prevent the power chip from being shut down prematurely during the discharge of the supercapacitor; when the input voltage of the power chip gradually drops to the chip startup threshold, the circuit is automatically "unlocked" to ensure that it can start normally again during the next charging process.

[0009] The method is as follows: the power supply outputs current, one current is charged in the capacitor, and the other current enters the power chip. When the voltage of the power chip reaches the start-up threshold, the power chip provides an output voltage VCC for the subsequent circuit;

[0010] The EN pin of the power chip is controlled by two voltage signals;

[0011] A resistor is set to divide the input voltage of the power chip. When the power chip is in the off state, if the capacitor is charged at this time, the power chip is controlled by the EN pin to start again after the capacitor stores enough electricity;

[0012] The output voltage VCC is fed back to the EN pin. When the power chip works normally, the output voltage VCC is fed back to the EN pin to form a self-locking state, so that the capacitor turns off the power chip in advance during the discharge process; when the input voltage of the power chip gradually drops to the chip startup threshold, the circuit is automatically unlocked, and the power chip starts normally again during the next charging process.

[0013] Furthermore, a small capacitor is placed at the EN pin, so that when the power chip is started, the voltage pulled down by the EN pin will not drop to the shutdown threshold.

[0014] Furthermore, a diode is connected in series in the circuit of the small capacitor to prevent the charge of the small capacitor from flowing back after the input voltage is reduced.

[0015] Furthermore, the output voltage VCC is fed back to the EN pin in a specific method as follows: a resistor X and a diode Y are connected in series between the output voltage VCC and the EN pin; the resistor setting is specifically to set at least two resistors, and the resistor directly connected to the EN pin is the resistor Y;

[0016] When the power chip is started, the output voltage VCC starts to output voltage, at which time the diode Y is turned on, and the resistance values ​​of the resistor Y and the resistor X are set to cut off the diode, so that the self-locking function of the power chip can be realized by feeding back the output voltage VCC to the EN pin to ensure its normal operation;

[0017] When the power chip stops working, the output voltage VCC has no output voltage, the diode Y is cut off, and the resistor provides a discharge path for the electric energy in the small capacitor, so that the signal of the EN pin quickly recovers to below the start threshold, and the power chip is automatically unlocked. At this time, the capacitor is recharged and the power chip is started again.

[0018] Furthermore, a voltage stabilizing diode is connected in parallel to the power supply, and a diode is connected in series to the capacitor. The voltage stabilizing diode prevents the capacitor from exceeding the allowed operating voltage. The main function of the diode is to prevent the electricity stored in the supercapacitor from leaking back to the previous stage device, causing unnecessary increase in static power consumption.

[0019] Furthermore, the power source includes a solar panel, a wireless charging device and other devices with unstable output voltage.

[0020] Furthermore, the power chip is a DCDC or LDO chip, which is also applicable to circuits or modules with the same functions.

[0021] The present invention also aims to provide a circuit design of a battery-free power supply method.

[0022] The circuit comprises:

[0023] The Vin voltage divider module is specifically: resistors R1, R2 and R3 are connected in series between the Vin and EN pins of the power chip.

[0024] A VCC feedback module, specifically: a resistor R4 and a diode D4 are connected in series between VCC and Vin of the power chip;

[0025] Furthermore, the circuit design also includes: a capacitor charging module, specifically: the positive electrode of the power supply is connected to the positive electrode of the diode D2 to output current, and the current enters the capacitor C1 for charging; one current of the power supply in the capacitor charging module charges the capacitor C1, and another current forms a path with the power chip through the resistors R1, R2 and R3.

[0026] Furthermore, in the Vin voltage divider module, a resistor R' is connected to the EN pin of the power chip, and a capacitor C2 is connected in parallel to the resistor R'; the resistor R' is R1 or R2 or R3.

[0027] Specifically, a small capacitor C2 is placed at the EN pin to ensure that the voltage pulled down by the EN pin when it is started does not drop to the shutdown threshold. The size of C2 can be set according to the power supply startup time and the current consumed by the EN pin.

[0028] Specifically, the larger the capacitor C2 is, the more it can ensure the power startup, but the longer the unlocking time will be. If the unlocking time is shortened by reducing the resistor R3, it will bring greater static power consumption. It can be set or debugged according to actual specific needs.

[0029] Furthermore, a diode D3 is connected in series to the capacitor C2.

[0030] Specifically, a diode D3 is connected in series to the capacitor C2, and the diode D3 prevents the electric quantity in C2 from flowing back after the voltage Vin is reduced.

[0031] Furthermore, a voltage stabilizing diode D1 is connected in parallel to the power supply.

[0032] Specifically, the feedback EN voltage generated by the VCC voltage division of R3 and R4 is greater than the voltage division value of Vin by R1 and R2. It is not recommended to select too small values ​​for R3 and R4, which will lead to an increase in static power consumption. If the values ​​are larger, the input current of the EN pin (generally in the nA or uA level) may not be ignored when calculating the actual voltage division value.

[0033] Furthermore, a diode D2 is connected in series between the capacitor and the power supply.

[0034] Specifically, as long as the voltage of the diode D2 drops to the target voltage after being connected in series with the power supply, the diode D2 is preferably a Schottky diode with small reverse leakage.

[0035] Specifically, the main function of the voltage regulator D1 is to limit the output voltage of the solar panel to prevent it from exceeding the operating voltage allowed by the subsequent supercapacitor; the main function of the diode D2 is to prevent the electricity stored in the supercapacitor from leaking back to the previous device, causing unnecessary increase in static power consumption.

[0036] Furthermore, the power source includes a solar panel, a wireless charging device, and other devices with unstable output voltage. Specifically, if the solar panel is replaced with other methods such as wireless charging as a charging power source, when the output power of the charging power source may decrease or be insufficient in the application, this method can still effectively avoid the problem of the circuit failing to start.

[0037] Furthermore, the power supply chip includes a DCDC chip and an LDO chip, and is also applicable to circuits or modules with the same functions.

[0038] Furthermore, in practical applications, a larger resistance value should be selected for each resistor under the premise of ensuring the circuit function to reduce the static power consumption of the system.

[0039] Furthermore, the aforementioned battery-free power supply circuit design is applied in low-energy consumption terminals or certain high-energy consumption scenarios where the output power supply is unstable.

[0040] Specifically, in the present invention, when the power chip is in the off state (which can be understood as the power of the whole product has been exhausted), the solar panel receives light and starts to charge the supercapacitor. Since VCC has no output, the diode D4 is cut off, and Vin is divided by R1, R2, and R3 to delay the start of the power chip, that is, Vin reaches the start threshold first, but the EN start threshold has not been reached. At this time, the power chip does not start. When the supercapacitor continues to charge for a period of time (so that the extra power stored is sufficient to support the consumption of the subsequent circuit at the moment of startup), EN reaches the start threshold, and the power chip starts normally again. In order to ensure that the voltage pulled down when the EN pin is started will not drop to the shutdown threshold, a small capacitor C2 needs to be placed at the EN pin. The diode D3 prevents the power in C2 from flowing back after the Vin voltage is reduced. The size of C2 can be set according to the power startup time and the current consumed by the EN pin;

[0041] When the power chip is started, VCC starts to output normal voltage. At this time, D4 ​​is turned on. As long as the resistance values ​​of R3 and R4 are set reasonably to make D3 cut off, the "self-locking" function of the power chip can be realized through the feedback of VCC output to the EN pin to ensure its normal operation.

[0042] When the power chip is working normally, if the solar panel has stopped charging the supercapacitor (or directly providing current input to the power chip), the amount of electricity stored in the supercapacitor will gradually decrease due to the energy consumption of the subsequent circuit, and the EN signal voltage generated by the Vin voltage divider will first drop to the EN shutdown threshold. At this time, due to the existence of the EN signal fed back by the diode D3 and the VCC terminal, the power chip can still continue to work until Vin continues to drop to the shutdown threshold, and the power chip will stop working;

[0043] After the power chip stops working, VCC has no output voltage and diode D4 is cut off. Since the EN pin current of a general power chip is usually much smaller than 1uA, R3 can provide a discharge path for the electric energy in capacitor C2, so that the EN signal quickly recovers to below the start threshold to ensure that the power chip is "automatically unlocked". At this time, the supercapacitor is recharged and the power chip can be started again.

[0044] The beneficial effects of the present invention are:

[0045] The power supply circuit provided by the present invention has a simple structure, low cost and low power consumption, and can solve the problem of power startup when charging devices such as solar panels are in a low-power state, while ensuring full utilization of the power stored in the supercapacitor.

[0046] The power supply circuit provided by the present invention is significantly superior to a battery power supply solution in terms of charge and discharge life, and does not require a complex charging management circuit when charging the capacitor, which is beneficial to saving product cost and size. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The simplest low-cost circuit diagram.

[0048] Figure 2 No battery powered circuit diagram. DETAILED DESCRIPTION

[0049] The examples are provided to better illustrate the present invention, but the present invention is not limited to the examples. Therefore, those skilled in the art may make non-essential improvements and adjustments to the implementation scheme according to the above invention content, which still fall within the protection scope of the present invention.

[0050] The power source of this embodiment is a solar panel.

[0051] The power chip of this embodiment is a DCDC chip, Vin is the power stage input, Vout is the power stage output, and EN is enable.

[0052] The present invention provides a circuit design without battery power supply, such as Figure 2 As shown, the circuit includes: a capacitor charging module, a Vin voltage dividing module and a VCC feedback module.

[0053] The capacitor charging module is specifically: the positive electrode of the power supply is connected to the positive electrode of the diode D2 to output current, and the current enters the capacitor C1 for charging;

[0054] The Vin voltage divider module is specifically: resistors R1, R2 and R3 are connected in series between the Vin and EN pins of the power chip.

[0055] A VCC feedback module, specifically: a resistor R4 and a diode D4 are connected in series between VCC and Vin of the power chip;

[0056] One current path of the power supply in the capacitor charging module charges the capacitor C1, and another current path forms a path with the power chip through the resistors R1, R2 and R3.

[0057] In the Vin voltage divider module, a resistor R' is connected to the EN pin of the power chip, and a capacitor C2 is connected in parallel to the resistor R'; the resistor R' is R1 or R2 or R3.

[0058] A small capacitor C2 is placed at the EN pin to ensure that the voltage pulled down by the EN pin when it is started does not drop to the shutdown threshold. The size of C2 can be set according to the power supply startup time and the current consumed by the EN pin.

[0059] A diode D3 is connected in series to the capacitor C2, and the diode D3 prevents the charge in C2 from flowing back after the voltage of Vin decreases.

[0060] The power supply is connected in parallel with a voltage regulator diode D1, the main function of which is to limit the output voltage of the solar panel to prevent it from exceeding the operating voltage allowed by the subsequent super capacitor.

[0061] A diode D2 is connected in series between capacitor C1 and the solar panel, wherein diode D2 is a Schottky diode. The main function of diode D2 is to prevent the electricity stored in the supercapacitor from leaking back to the previous stage device, causing unnecessary increase in static power consumption.

[0062] Among them, the power supply V is grounded, the Vin voltage divider module is grounded, and the power chip is grounded.

[0063] In this embodiment, when the power chip is in the off state (which can be understood as the power of the whole product has been exhausted), the solar panel receives light and starts to charge the supercapacitor. Since VCC has no output, the diode D4 is cut off, and Vin is divided by R1, R2, and R3 to delay the start of the power chip, that is, Vin reaches the start threshold first, but the EN start threshold has not been reached. At this time, the power chip does not start. When the supercapacitor continues to charge for a period of time (so that the extra power stored is sufficient to support the consumption of the subsequent circuit at the moment of startup), EN reaches the start threshold, and the power chip starts normally again. In order to ensure that the voltage pulled down by the EN pin when it is started will not drop to the shutdown threshold, a small capacitor C2 needs to be placed at the EN pin. The diode D3 prevents the power in C2 from flowing back after the Vin voltage is reduced. The size of C2 can be set according to the power startup time and the current consumed by the EN pin;

[0064] When the power chip is started, VCC starts to output normal voltage. At this time, D4 ​​is turned on. As long as the resistance values ​​of R3 and R4 are set reasonably to make D3 cut off, the "self-locking" function of the power chip can be realized through the feedback of VCC output to the EN pin to ensure its normal operation.

[0065] When the power chip is working normally, if the solar panel has stopped charging the supercapacitor (or directly providing current input to the power chip), the amount of electricity stored in the supercapacitor will gradually decrease due to the energy consumption of the subsequent circuit, and the EN signal voltage generated by the Vin voltage divider will first drop to the EN shutdown threshold. At this time, due to the existence of the EN signal fed back by the diode D3 and the VCC terminal, the power chip can still continue to work until Vin continues to drop to the shutdown threshold, and the power chip will stop working;

[0066] After the power chip stops working, VCC has no output voltage, and the diode D4 is cut off. Since the EN pin current of a general power chip is usually much less than 1uA, R3 can provide a discharge path for the energy in the C2 capacitor, so that the EN signal quickly recovers to below the start threshold to ensure that the power chip is "automatically unlocked". At this time, the supercapacitor is recharged and the power chip can be started again;

[0067] In addition, in actual applications, larger resistance values ​​should be selected for each resistor while ensuring the circuit function to reduce the static power consumption of the system.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A battery-free power supply method, characterized in that: The external power supply outputs two currents, one output current charges the supercapacitor C1 connected in parallel to both ends of the external power supply, and the other output current enters the Vin pin and EN pin of the power chip. When the input voltage of the EN pin of the power chip reaches the chip startup threshold, the power chip provides an output voltage VCC for the subsequent circuit; The EN pin of the power chip is controlled by two voltage signals; A voltage-dividing resistor is set to be connected between the Vin pin and the EN pin of the power chip to divide the input voltage of the Vin pin of the power chip. When the power chip is in the off state, if the external power supply outputs current to charge the supercapacitor C1, the power chip is controlled by the input voltage of the EN pin to start after the supercapacitor C1 stores enough electricity; The output voltage VCC is fed back to the EN pin. When the power chip works normally, the output voltage VCC is fed back to the EN pin to form a self-locking state, so that during the discharge process of the super capacitor C1, the input voltage of the EN pin of the power chip is first reduced to the chip shutdown threshold. When the input voltage of the Vin pin of the power chip gradually decreases to the chip shutdown threshold, the power chip stops working. After the power chip stops working, the input voltage of the EN pin gradually recovers to the chip startup threshold, and the power chip is automatically unlocked until the next charging process of the super capacitor C1, when the power chip starts normally again. Among them, the voltage-dividing resistor is connected between the Vin pin and the EN pin of the power chip, and the specific method for dividing the input voltage of the Vin pin of the power chip is: a resistor R1, a resistor R2, a resistor R3, a capacitor C2, and a diode D3 are set between the Vin pin and the EN pin of the power chip, the resistor R1 and the resistor R2 are connected in series between the Vin pin of the power chip and the ground, the anode of the diode D3 is connected to the connection between the resistor R1 and the resistor R2, the cathode of the diode D3 is connected to one end of the parallel branch composed of the capacitor C2 and the resistor R3 and the EN pin of the power chip, and the other end of the parallel branch composed of the capacitor C2 and the resistor R3 is grounded; The specific method of feeding back the output voltage VCC to the EN pin is as follows: a resistor R4 and a diode D4 are connected in series between the output voltage VCC and the EN pin; when the power chip is started, the power chip starts to output the output voltage VCC, at which time the diode D4 is turned on, and the resistance values ​​of the resistor R3 and the resistor R4 are set so that the diode D3 is turned off, that is, the self-locking function of the power chip is realized by feeding back the output voltage VCC to the EN pin, thereby ensuring the normal operation of the power chip; When the power chip stops working, the output voltage VCC is zero, the diode D4 is cut off, and the resistor R3 provides a discharge path for the electric energy in the capacitor C2, so that the input voltage of the EN pin is quickly restored to below the chip startup threshold, and the power chip is automatically unlocked. At this time, the supercapacitor C1 is recharged and the power chip is started again.

2. The battery-free power supply method according to claim 1, characterized in that: The capacitor C2 is placed at the EN pin, and when the power chip is started, the input voltage of the EN pin will not drop to the chip shutdown threshold.

3. The battery-free power supply method according to claim 2, characterized in that: The diode D3 can prevent the charge of the capacitor C2 from flowing back after the input voltage of the EN pin decreases.

4. The battery-free power supply method according to claim 1, characterized in that: The external power source includes any one of a solar panel, a wireless charging device, and other devices with unstable output voltage.

5. A battery-free power supply circuit using the battery-free power supply method according to any one of claims 1 to 4, characterized in that: include: The Vin voltage divider module is specifically: a resistor R1, a resistor R2 and a resistor R3 are connected between the Vin pin and the EN pin of the power chip, wherein the resistor R1 and the resistor R3 are connected in series between the Vin pin of the power chip and the ground; the resistor R2 and the resistor R3 are connected in parallel; The VCC feedback module is specifically: a resistor R4 and a diode D4 are connected in series between the Vout pin of the power chip and the EN pin of the power chip.

6. The battery-free power supply circuit according to claim 5, characterized in that: The circuit also includes a capacitor charging module, specifically: the positive electrode of the external power supply is connected to the anode of the diode D2 to output current, and the output current enters the supercapacitor C1 for charging; one output current of the external power supply in the capacitor charging module charges the supercapacitor C1, and the other output current forms a path with the Vin pin and EN pin of the power chip through the resistor R1, the resistor R2 and the resistor R3.

7. The battery-free power supply circuit according to claim 5, characterized in that: The power chip includes any one of a DC / DC chip and an LDO chip.

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