CN216390555U

CN216390555U - Super capacitor power supply circuit with under-voltage protection

Info

Publication number: CN216390555U
Application number: CN202122553510.XU
Authority: CN
Inventors: 李亚胜; 陆涛; 林斌; 王韬樾; 褚如旭; 蔡旭锋; 邓非凡; 宋靖涛
Original assignee: Hangzhou Zhiwei Yilian Power Technology Co ltd
Current assignee: Hangzhou Smart Yilian Technology Co.,Ltd.
Priority date: 2021-10-22
Filing date: 2021-10-22
Publication date: 2022-04-26
Anticipated expiration: 2031-10-22

Abstract

The utility model discloses a super capacitor power supply circuit with under-voltage protection, which comprises a super capacitor charging and discharging circuit, a voltage sampling circuit, a switch control circuit, a voltage conversion circuit and a voltage positive feedback loop. The technical scheme avoids the situation that the post-stage circuit enters an undervoltage state after the capacitor is continuously discharged when the circuit is powered by the super capacitor, and the adopted undervoltage protection circuit does not need an additional reference voltage source as a reference, only depends on the voltage stabilizing diode, the resistor and the triode to realize the setting of an undervoltage threshold, and saves the circuit cost and the layout space; the utility model adopts the design of positive voltage feedback, and accelerates the action speed of circuit protection.

Description

Super capacitor power supply circuit with under-voltage protection

Technical Field

The utility model relates to the technical field of integrated circuit power supplies, in particular to a super capacitor power supply circuit with under-voltage protection.

Background

Super capacitors are often used to supply power to current integrated circuits, so that the circuits can be supported to continue working for a period of time during sudden power failure, for storing data, giving an alarm, and the like. However, the voltage of the super capacitor can continuously drop during the discharging period, and the power supply voltage of a post-stage circuit can be insufficient after the voltage drops to a certain threshold value, so that the problems of low-voltage restart of a chip and the like are caused. Therefore, a super capacitor power supply scheme with under-voltage protection is needed, and the power circuit is turned off before the capacitor voltage reaches an under-voltage threshold value, so that circuit disorder caused by insufficient supply voltage of a rear-stage circuit is avoided.

Chinese patent document CN108347036A discloses a "switching power supply circuit with input over-voltage and under-voltage protection and LED driving circuit, patent titles (english): switching power supply circuit and LED driving circuit with input over voltage and under-voltage protection ". The LED drive circuit comprises a switch power supply circuit with input over-voltage and under-voltage protection and an LED drive circuit. The switching power supply circuit includes: the transformer comprises a transformer, a power switch, a sampling resistor, a power supply resistor, a control circuit and a power supply capacitor, wherein one end of an auxiliary winding of the transformer is connected with a pair of voltage dividing resistors, a midpoint voltage signal of the pair of voltage dividing resistors is sampled before the power switch is turned off, when the sampling signal is lower than a first reference voltage, overvoltage protection is triggered, and when the sampling signal is higher than a second reference voltage and lasts for preset time, undervoltage protection is triggered. The switching power supply circuit with the input overvoltage and undervoltage protection function provided by the utility model provides a safe and reliable overvoltage and undervoltage protection function of input alternating voltage on the premise of saving system cost without adding any peripheral circuit on the conventional flyback switching power supply. In addition, the switching power supply circuit collects input voltage information before the power switch is turned off, and errors and interference caused by voltage oscillation of the auxiliary winding are effectively avoided.

Disclosure of Invention

The utility model mainly solves the technical problems of errors and interference caused by voltage oscillation of an auxiliary winding in the prior technical scheme, and provides a super capacitor power supply circuit with under-voltage protection.

The technical problem of the utility model is mainly solved by the following technical scheme: the super-capacitor charge-discharge circuit comprises a super-capacitor charge-discharge circuit, a voltage sampling circuit, a switch control circuit, a voltage conversion circuit and a voltage positive feedback circuit, wherein one end of the capacitor charge-discharge circuit is connected with a power supply, the other end of the capacitor charge-discharge circuit is connected with the voltage sampling circuit, one end of the switch control circuit is connected with the voltage sampling circuit, the other end of the switch control circuit is connected with the voltage conversion circuit, the other end of the voltage conversion circuit is connected with an output voltage, one end of the output voltage is connected with the voltage positive feedback circuit, and the other end of the output voltage is connected with the switch control circuit.

Preferably, the super capacitor charging and discharging circuit comprises a diode D1, a resistor R1, a resistor R4 and a capacitor C3, wherein a cathode of the diode D1 is connected with one end of the resistor R1 and is also connected with the input end Vin of the power supply, an anode of the diode D1 is connected with the other end of the resistor R1, an anode of the diode D1 is grounded through a resistor R4 and a charging capacitor C3, the diode D1 is a schottky diode, and the capacitor C3 is a super capacitor. The Schottky diode has low voltage endurance, but the Schottky diode has high recovery speed and can be used in high-frequency occasions, and under the working condition, the Schottky diode can carry out reverse bias and can not transmit any current.

Preferably, the voltage sampling circuit comprises a diode D2 and a resistor R5, a cathode of the diode D2 is connected with one end of the resistor R2 and is also connected with the input end Vin of the power supply, an anode of the diode D2 is connected with one end of the resistor R3, an anode of the diode D2 is grounded through the resistor R5, and the diode D2 is a zener diode. When the voltage stabilizing tube is connected into the circuit, if the voltage of each point in the circuit fluctuates due to the fluctuation of the power voltage or other reasons, the voltage at two ends of the load is basically kept unchanged.

Preferably, the switch control circuit comprises a MOS transistor Q1, a transistor Q2, a resistor R2 and a resistor R3, one end of the MOS transistor Q1 is connected with the resistor R2 and the input end Vin of the power supply, the other end of the MOS transistor is connected with the input end of the voltage regulator U1, the gate of the MOS transistor is connected with the other end of the resistor R2, the gate of the MOS transistor is connected with the collector of the transistor Q2, the base of the transistor Q2 is connected with a diode D2 and the resistor R5 through the resistor R3, one end of the emitter of the transistor Q2 is connected with the R5, the other end of the emitter is grounded, the Q1 is a PMOS transistor, and the Q2 is an NPN transistor.

Preferably, the voltage conversion circuit comprises a capacitor C1, a capacitor C2 and a voltage regulator U1, an input end in of the voltage regulator U1 is connected with the drain of the MOS transistor and is grounded through the capacitor C1, an output end out and a feedback end tag of the voltage regulator U1 are grounded through a capacitor C2, an output end out of an output end of the voltage regulator U1, a feedback end tag and one end of a load resistor Rload are connected to an output voltage Vout, the U1 is an LDO low dropout voltage regulator chip, and Rload is a rear-stage circuit load. The voltage difference describes the minimum difference between Vin and Vout required for normal regulation. The voltage difference is the difference between the input terminal Vin and the output terminal Vout which satisfies the minimum under normal output, and can be expressed as follows:

Vin(min)-Vout(nom)＝Vdo

therefore, when designing the circuit, it must be ensured that:

Vin>＝Vout+Vdo

otherwise, the normal output cannot be performed.

Preferably, the voltage positive feedback loop (5) comprises a resistor R6, one end of the resistor R6 is connected with the base of the triode, and the other end of the resistor R6 is connected with the output voltage Vout. Rload is the load of the subsequent stage circuit

The utility model has the beneficial effects that:

1. the condition that the rear-stage circuit enters an undervoltage state after the capacitor is continuously discharged when the circuit is powered by the super capacitor is avoided.

2. The undervoltage protection circuit does not need an additional reference voltage source as a reference, and the undervoltage threshold is set only by the voltage stabilizing diode, the resistor and the triode, so that the circuit cost and the layout space are saved.

3. The voltage positive feedback design is adopted, and the action speed of circuit protection is increased.

Drawings

Fig. 1 is a schematic block diagram of the circuit of the present invention.

Fig. 2 is a circuit diagram of the present invention.

In the figure, a capacitor charging and discharging circuit 1, a voltage sampling circuit 2, a switch control circuit 3, a voltage conversion circuit 4 and a voltage positive feedback loop 5 are arranged.

Detailed Description

The technical scheme of the utility model is further specifically described by the following embodiments and the accompanying drawings.

Capacitor charging and discharging circuit 1: when an external power supply supplies power, Vin charges the super capacitor C3 through the capacitor R1, and the large current impact at the moment of electrifying the capacitor C3 is limited; after the external power supply is disconnected, the super capacitor C3 supplies power to a post-stage circuit through the diode D1, and the low-conduction-voltage characteristic of the Schottky diode can effectively improve the charge utilization rate of the super capacitor; the resistor R4 is used for self-discharging of the super capacitor when the circuit is disconnected.

Voltage sampling circuit 2: the sampling point voltage Ua is generated by voltage division of a voltage stabilizing diode D2 and a resistor R5; the sampling point voltage is approximately equal to the input voltage minus the voltage regulator tube stable voltage (Ua ≈ Vin-Uz), and a voltage regulator tube D2 with lower reverse leakage current and a resistor R5 with smaller resistance value are considered to be selected (because extra voltage drop is generated when the leakage current of the voltage regulator tube flows through the resistor R5, and the circuit debugging difficulty is increased);

the switch control circuit 3: the switch circuit adopts a PMOS tube Q1 to control the on and off of the input voltage; when the super capacitor starts to discharge, the voltage Ua at the point a is higher than the base electrode breakover voltage Vth (about 0.7V) of the triode Q2, at the moment, the Q2 is conducted, the grid voltage of the PMOS transistor Q1 is pulled to the ground, and the Q1 is in a conducting state; after the super capacitor discharges continuously, the Vin voltage drops, when the voltage Ua at the point a drops below Vth, the Q2 starts to be cut off, at the moment, the grid voltage of the PMOS tube Q1 is pulled up to Vin by the R2, and the Q1 enters an off state;

voltage conversion circuit 4: the input capacitor C1, the low dropout regulator U1 and the output capacitor C2 form a voltage conversion battery, and an input voltage Vin fluctuating in a certain range is converted into a stable output voltage Vout; however, the linear voltage regulator U1 has a voltage difference limitation, and if the voltage difference limitation of U1 is 1V, Vin is required to be greater than or equal to Vout +1V, and the linear voltage regulator U1 can normally work to maintain the output voltage Vout stable; on the contrary, the output voltage Vout is not kept stable, and will decrease with the decrease of the input voltage Vin; voltage positive feedback loop 5: the resistor R6 is connected with the output voltage end and the point b of the switch control circuit; when the voltage at the point b drops, the Q2 starts to be cut off, the Q1 starts to enter an off state, the level of the pin 3 of the U1 chip starts to drop, and the output voltage Vout of the U1 chip decreases; the change of Vout is fed back to the control circuit through R6, and the accelerating circuit enters an off state to form positive feedback.

In this embodiment, the undervoltage protection action generation process is as follows: the external power supply is disconnected, and the super capacitor C3 starts to supply power to the line; the Vin voltage begins to drop in the power supply process of the super capacitor, the sampling voltage Ua at the point A also drops, when the voltage of the Ua drops to be less than 0.7V, the triode Q2 begins to be cut off, the grid voltage of the PMOS pipe Q1 rises, and the Q1 begins to enter a cut-off state; after the Q1 enters the off state, the input voltage of the pin 3 of the U1 chip is continuously reduced, and the output Vout also begins to fall; the resistor R6 accelerates the turn-off process of the circuit by positive feedback, so that the output voltage Vout is reduced from a stable voltage value to 0V in a short time. In a super capacitor power supply circuit without under-voltage protection, the output voltage Vout of the low dropout regulator U1 continuously decreases with the decrease of the input voltage Vin, gradually decreases from a stable voltage value to 0V, and causes under-voltage disorder of a rear-stage load circuit in the process.

In this embodiment, assuming that the required regulated output voltage Vout is 3.3V and the differential voltage of the low dropout regulator U1 is limited to 1V, the Vin undervoltage protection threshold is 3.3V +1V — 4.3V, and the D2 should select a zener diode with 4.3V-0.7V — 3.6V. At this time, when the supply voltage Vin of the super capacitor continuously drops to 4.3V, the Ua voltage is smaller than the turn-on voltage drop Vth of Q2, Q2 starts to be cut off, the gate voltage of Q1 rises, Q1 enters a turn-off state, and the voltage input loop is disconnected, so that the output voltage Vout is prevented from dropping along with Vin to avoid circuit disorder caused by insufficient supply voltage of a subsequent circuit.

The specific embodiments described herein are merely illustrative of the spirit of the utility model. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the utility model as defined in the appended claims.

Although terms like voltage sampling circuits are used more here, the possibility of using other terms is not excluded. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed as being without limitation to any additional limitations that may be imposed by the spirit of the present invention.

Claims

1. The utility model provides a take under-voltage protection's super capacitor supply circuit, a serial communication port, including super capacitor charge and discharge circuit (1), voltage sampling circuit (2), on-off control circuit (3), voltage conversion circuit (4) and voltage positive feedback return circuit (5), the power is connected to capacitor charge and discharge circuit one end, voltage sampling circuit is connected to the other end, on-off control circuit one end is connected with voltage sampling circuit, the other end is connected with voltage conversion circuit, output voltage is connected to voltage conversion circuit's the other end, voltage positive feedback return circuit is connected to output voltage one end, other end connection on-off control circuit.

2. The super capacitor power supply circuit with the undervoltage protection as claimed in claim 1, wherein the super capacitor charging and discharging circuit (1) comprises a diode D1, a resistor R1, a resistor R4 and a capacitor C3, a cathode of the diode D1 is connected to one end of a resistor R1 and is also connected to the input terminal Vin of the power supply, an anode of the diode D1 is connected to the other end of the resistor R1, an anode of the diode D1 is grounded via a resistor R4 and a charging capacitor C3, the diode D1 is a schottky diode, and the capacitor C3 is a super capacitor.

3. The super capacitor power supply circuit with the undervoltage protection function as claimed in claim 1, wherein the voltage sampling circuit (2) comprises a diode D2 and a resistor R5, a cathode of the diode D2 is connected to one end of the resistor R2 and is also connected to the power supply input terminal Vin, an anode of the diode D2 is connected to one end of a resistor R3, an anode of the diode D2 is connected to the ground through the resistor R5, and the diode D2 is a zener diode.

4. The super capacitor power supply circuit with the undervoltage protection as claimed in claim 1, wherein the switch control circuit (3) includes a MOS transistor Q1, a transistor Q2, a resistor R2, and a resistor R3, one end of the MOS transistor Q1 is connected to the resistor R2 and is also connected to the power supply input Vin, the other end of the MOS transistor is connected to the input of the regulator U1, the gate of the MOS transistor is connected to the other end of the resistor R2, meanwhile, the gate of the MOS transistor is connected to the collector of the transistor Q2, the base of the transistor Q2 is connected to the diode D2 and the resistor R5 through the resistor R3, one end of the emitter of the transistor Q2 is connected to the R5, the other end of the transistor Q1 is grounded, and the transistor Q2 is an NPN transistor.

5. The super capacitor power supply circuit with the undervoltage protection as claimed in claim 1, wherein the voltage conversion circuit (4) comprises a capacitor C1, a capacitor C2, and a regulator U1, an input terminal in of the regulator U1 is connected to the drain of the MOS transistor and is grounded via the capacitor C1, an output terminal out and a feedback terminal tag of the regulator U1 are grounded via the capacitor C2, an output terminal out of the regulator U1, the feedback terminal tag, and one end of a load resistor Rload are connected to the output voltage Vout, the U1 is an LDO low dropout regulator chip, and Rload is a post-stage circuit load.

6. The super capacitor power supply circuit with the under-voltage protection as claimed in claim 1 or 5, wherein the voltage positive feedback loop (5) comprises a resistor R6, one end of the resistor R6 is connected to the base of the triode, and the other end is connected to the output voltage Vout.