CN111585324A - Low-voltage protection circuit and charger - Google Patents

Abstract

The invention relates to the technical field of protection circuits, and discloses a low-voltage protection circuit and a charger, which are applied to a charging loop of a photovoltaic power generation energy storage system. Therefore, when the charging loop is in a low voltage state, the comparison circuit controls the switch circuit to be in a broken circuit working state, and then the power supply for the system controller is cut off, so that the system controller is prevented from working in an undervoltage state, and the system controller is reliably protected from low voltage.

Description

A low-voltage protection circuit and charger

technical field

The invention relates to the technical field of protection circuits, in particular to a low-voltage protection circuit and a charger.

Background technique

In the process of using off-grid photovoltaic power generation and energy storage products, users have higher and higher requirements for intelligent energy storage products, especially the requirements for intelligent activation and intelligent charging of energy storage products are becoming more and more significant. In the process of use, users usually hope that when the photovoltaic power generation panel is connected to the energy storage product, the product can realize intelligent activation and intelligent charging. The product can still be activated and charged normally. For this reason, in the off-grid photovoltaic power generation energy storage products, most of the energy storage products use a dual power supply to activate the MCU power supply scheme in the design of the MCU power supply circuit, that is, use a power supply circuit design that is compatible with batteries and photovoltaic power generation panels. , The software control strategy is correct, the charging port of the energy storage product is detected in real time to control it, so that the intelligent activation and charging of the energy storage product can be realized by the photovoltaic power generation panel.

However, in the actual use process, since the photovoltaic power generation panel is greatly affected by the light intensity, when the external light intensity is weak, the output power of the photovoltaic power generation panel is very low. Although the MCU can be activated, it cannot maintain the normal operation of the MCU. This will cause the MCU to be in an undervoltage working state for a long time, and then cause the MCU to enter a dormant state, because it cannot meet the user's requirements for intelligent activation and intelligent charging, which seriously affects the user experience. Therefore, in off-grid photovoltaic power generation and energy storage products, the design of low-voltage protection circuits for MCU power supply is very important.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, the purpose of the present invention is to provide a low-voltage protection circuit and a charger, so as to realize low-voltage protection.

The purpose of this invention is to realize through following technical scheme:

In order to solve the above technical problems, in the first aspect, the embodiment of the present invention provides a low-voltage protection circuit, which is applied to a charging circuit of a photovoltaic power generation and energy storage system, and is characterized in that, it includes:

a sampling circuit for sampling the input voltage of the charging circuit;

A voltage regulator circuit for providing a reference voltage;

a comparison circuit, connected to the sampling circuit and the voltage regulator circuit respectively, for outputting a control signal according to the sampling signal and the reference voltage; and

A switch circuit, which is respectively connected to the comparison circuit and the charging circuit, is used for controlling the working state of the charging circuit according to the control signal, and the working state includes an on state and an off state.

Optionally, the switch circuit includes: a first switch circuit and a second switch circuit connected in series, the first switch circuit is further connected to the comparison circuit, and the second switch circuit is also connected to the charging circuit loop connection.

Optionally, the sampling circuit includes a first operational amplifier, the non-inverting input terminal of the first operational amplifier is connected to the negative pole of the input voltage of the charging loop, and the inverting input terminal of the operational amplifier is connected to the charging loop. The input voltage is positive, and the output end of the first operational amplifier is connected to the comparison circuit.

Optionally, the comparison circuit includes a second operational amplifier, the non-inverting input terminal of the second operational amplifier is connected to the output terminal of the first operational amplifier, and the inverting input terminals of the second operational amplifier are respectively connected to the The positive pole of the input voltage of the voltage regulator circuit and the charging circuit.

Optionally, the power supply terminal of the second operational amplifier is connected to the positive pole of the input voltage of the charging loop.

Optionally, the first switch circuit is a triode, the base of the triode is connected to the output end of the second remote amplifier, the collector of the triode is connected to the second switch circuit, and the transmitter of the triode is connected. pole ground.

Optionally, the second switch circuit is a MOS switch, and the collector of the triode is connected to the gate of the MOS switch to control the on or off of the MOS switch.

Optionally, the voltage regulator circuit includes a voltage regulator tube, the negative electrode of the voltage regulator tube is connected to the inverting input terminal of the second operational amplifier, and the positive electrode of the voltage regulator tube is grounded.

In a second aspect, an embodiment of the present invention provides a charger, the charger comprising:

Photovoltaic power generation system, which is used to generate electric energy using photovoltaic system;

The low-voltage protection circuit as described above, connected to the photovoltaic power generation system for low-voltage protection; and

The charging circuit is respectively connected with the low-voltage protection circuit and the system controller, and is used for supplying power to the system controller with the electric energy generated by the photovoltaic power generation system.

Compared with the prior art, the beneficial effects of the present invention are: different from the prior art, a low-voltage protection circuit is provided in the embodiment of the present invention, which is applied to the charging circuit of the photovoltaic power generation and energy storage system. It includes a sampling circuit, a voltage stabilizer circuit, a comparison circuit and a switch circuit. The sampling circuit is used to sample the input voltage of the charging circuit, and the voltage stabilizer circuit is used to provide a reference voltage. The signal and the reference voltage output a control signal, and the switch circuit is respectively connected with the comparison circuit and the charging circuit, and is used to control the working state of the charging circuit according to the control signal. Therefore, when the charging circuit is low-voltage, the comparison circuit controls the switch circuit to be in an open-circuit working state, thereby disconnecting the power supply for the system controller, preventing the system controller from working in an under-voltage state, and realizing reliable low-voltage protection for the system controller.

Description of drawings

One or more embodiments are exemplified by the pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations to the embodiments, and the elements/modules and steps with the same reference numerals in the drawings represent For similar elements/modules and steps, the figures in the accompanying drawings do not constitute a scale limitation unless otherwise stated.

1 is a schematic structural diagram of a charger according to an embodiment of the present invention;

2 is a schematic structural diagram of a low-voltage protection circuit provided by an embodiment of the present invention;

3 is a schematic structural diagram of a low-voltage protection circuit provided by another embodiment of the present invention;

FIG. 4 is a schematic diagram of a circuit structure of a low-voltage protection circuit provided by yet another embodiment of the present invention.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

Please refer to FIG. 1 . FIG. 1 shows a charger according to an embodiment of the present invention, which is applied to a photovoltaic power generation energy storage system. The photovoltaic power generation system refers to a power generation system that directly converts light energy into electrical energy without a thermal process. Its main components are solar cells, accumulators, controllers and inverters. It is characterized by high reliability, long service life, no environmental pollution, independent power generation and grid-connected operation. The photovoltaic power generation system includes a battery pack and a system controller. The function of the battery pack is to store the electric energy emitted by the solar cell array when it is illuminated and can supply power to the load at any time. The system controller is a device that controls the charging and discharging of the battery. At the same time, the power generated by the photovoltaic power generation system supplies power to the system controller, so that the system controller can work normally. When the power output from the photovoltaic power generation panel is low and the system controller is in an under-voltage working state, the system controller will go to sleep. state, can not meet the requirements of intelligent charging, affecting the user experience. Therefore, it is necessary to carry out low-voltage protection for the system controller. When the charging input voltage is low, the low-voltage protection circuit cuts off the charging circuit, thereby completely shutting down the system controller, so that the system controller stops working and prevents the system controller from entering a sleep state.

As shown in FIG. 1 , the charger includes a photovoltaic power generation system 400, a low voltage protection circuit 100, and a charging circuit 200. The electric energy generated by the photovoltaic power generation system 400 supplies power to the system controller 300 through the charging circuit 200, so that the system controller 300 can work normally , the circuits of each part in the photovoltaic power generation system 400 can be normally controlled, for example, the photovoltaic power generation system 400 is controlled to charge the battery pack for energy storage. The low-voltage protection circuit 100 is arranged between the photovoltaic power generation system 400 and the charging circuit 200, and the charging circuit 200 is respectively connected with the low-voltage protection circuit 100 and the system controller 300. During the process of supplying power to the system controller 300, the low-voltage protection circuit 100 is in the In the on state, the photovoltaic power generation system 400 can normally supply power to the system controller 300 through the charging circuit 200. If the power generated by the photovoltaic power generation system 400 is low, so that the system controller 300 is in an under-voltage state, the low-voltage protection circuit 100 detects When the charging input voltage reaches the low voltage value, the circuit between the photovoltaic power generation system 400 and the charging circuit 200 will be disconnected, so that the charger works in an open-circuit working state, so that the charger can no longer supply power to the system controller 300, completely. The system controller 300 is turned off to achieve the purpose of low voltage protection of the system controller 300 .

Please refer to FIG. 2 . FIG. 2 is a schematic structural diagram of a low-voltage protection circuit according to an embodiment of the present invention. As shown in FIG. 2 , the low-voltage protection circuit 100 includes a sampling circuit 10 , a voltage regulator circuit 20 , a comparison circuit 30 and a switch circuit 40 . , the sampling circuit 10 is used to sample the input voltage of the charging circuit 200, the voltage stabilizer circuit 20 is used to provide a reference voltage, and the comparison circuit 30 is connected to the sampling circuit 10 and the voltage stabilizer circuit 20 respectively, and is used for sampling according to the output of the sampling circuit 10. The reference voltage generates a control signal; and the switch circuit 40 is connected to the comparison circuit 30 and the charging circuit 200 respectively, and is used for controlling the working state of the charging circuit 200 according to the control signal, and the working state includes an on state and an off state. Therefore, when the charging circuit 200 is low-voltage, the control signal output by the comparison circuit 30 controls the switch circuit 40 to be in an open-circuit working state, thereby causing the charging circuit 200 to be disconnected, so that the photovoltaic power generation system 400 can no longer supply power to the system controller 300 and control the system. The device 300 realizes reliable low-voltage protection.

Please refer to FIG. 3 . FIG. 3 is a low-voltage protection circuit provided by another embodiment of the present invention. As shown in FIG. 3 , the low-voltage protection circuit 100 includes a sampling circuit 10 , a voltage regulator circuit 20 , a comparison circuit 30 and a switch circuit 40 . The sampling circuit 10 is respectively connected with the charging circuit 200 and the comparison circuit 30, the comparison circuit 30 is respectively connected with the sampling circuit 10, the voltage regulator circuit 20 and the switching circuit 40, the switching circuit 40 is also connected with the charging circuit 200, and the working state of the switching circuit 40 is controlled Passing and breaking of the charging circuit 200 .

Wherein, the sampling circuit 30 is configured to output the control signal to control the working state of the switching circuit 40 according to the sampling signal and the reference voltage, and the working state includes an on state and an off state. The sampled signal is the input voltage of the charging circuit 200, and the reference voltage is a preset voltage value, which is provided by the voltage regulator circuit 20. When the sampled voltage value is less than the reference voltage, it means that the power supply voltage of the system controller 300 has reached the low voltage protection level. value, the comparison circuit 21 outputs a control signal, and then the control signal controls the switch circuit 40 to be disconnected, so that the charging circuit 200 works in an open-circuit working state, so that the charging circuit 200 can no longer continue to supply power to the system controller 300, and can reliably supply power to the rear The system controller implements low voltage protection. It should be noted that the reference voltage can be set as required, and is not specifically limited.

In some embodiments, please continue to refer to FIG. 3 , the switch circuit 40 includes a first switch circuit 41 and a second switch circuit 42 connected in series, the first switch circuit 41 is also connected to the comparison circuit 30 , and the first switch circuit 41 is connected to the comparison circuit 30 . The second switch circuit 42 is also connected to the charging circuit 200 . Specifically, the second switch circuit 42 is disposed on the charging bus of the charging circuit 200 . Wherein, when the charging input voltage is low, the output signal of the comparison circuit 30 controls the first switch circuit 41 to be turned off, and the turn-off of the first switch circuit 41 will cause the second switch circuit 42 to work in an open state. Therefore, the charging circuit 200 The charging bus is in a disconnected state, so that the charging circuit 200 is disconnected and can no longer supply power to the system controller 300, so that the system controller 300 is completely shut down, and low-voltage protection is reliably realized.

In some embodiments, the entire charging system further includes an auxiliary power supply circuit 400, which is connected to the charging circuit 200 and the system controller 300 respectively, and is used to adjust the working voltage provided by the charging circuit 200, and will adjust the subsequent The operating voltage is applied to the system controller 300 . The auxiliary power supply circuit 400 is used to convert the power provided by the charging circuit 200 into a voltage suitable for the system controller 300 , so that the system controller 300 can be powered normally, thereby enabling the system controller 300 to work normally. Generally, the voltage provided by the auxiliary power supply circuit 40 is low voltage. It should be noted that the operating voltage of the system controller 300 can be determined by the specific chip of the controller, and does not need to be bound by the specific value.

Please refer to FIG. 4 . FIG. 4 is a schematic diagram of a circuit structure of a low-voltage protection circuit provided by yet another embodiment of the present invention. As shown in FIG. 4 , the sampling circuit 10 includes a first operational amplifier U1 , the inverting input terminal of the first operational amplifier U1 is connected to the positive input voltage Input+ of the charging circuit 200 , and the non-inverting input terminal of the operational amplifier U1 The input terminal is connected to the negative electrode Input- of the input voltage of the charging circuit 200, and the output terminal of the first operational amplifier U1 is connected to the comparison circuit 30. Specifically, the output terminal of the first operational amplifier U1 is connected to the comparison circuit. At the same time, in order to filter out the clutter in the input signal of the charging circuit 200, the sampling circuit 10 also includes a first filter capacitor C1 and a second filter capacitor C2, and the first filter capacitor C1 is respectively connected to the first operational amplifier U1 The inverting input terminal of the first operational amplifier and the output terminal of the first operational amplifier, and the second filter capacitor C2 is respectively connected to the non-inverting input terminal of the first operational amplifier U1 and the ground.

In some embodiments, please continue to refer to FIG. 4 , the sampling circuit 10 further includes a first resistor R1 , a second resistor R2 , a third resistor R3 and a fourth resistor R4 , and the first resistor R1 is connected in series with the positive electrode of the input terminal of the charging loop 200 Between Input+ and the inverting input terminal of the first operational amplifier U1, the second resistor R2 is connected in series between the negative electrode Input- of the input terminal of the charging loop and the non-inverting input terminal of the first operational amplifier U1, and the third resistor R3 is connected in series with the first operational amplifier U1. Between the inverting input terminal of an operational amplifier U1 and the output terminal of the first operational amplifier U1, it is a feedback resistor, and the fourth resistor is connected in series between the negative input terminal Input- of the input terminal and the non-inverting input terminal of the first operational amplifier U1.

In some embodiments, please continue to refer to FIG. 4 , the voltage regulator circuit 20 includes a voltage regulator tube ZD1 , the negative electrode of the voltage regulator tube ZD1 is connected to the comparison circuit 30 , and the positive electrode of the voltage regulator tube ZD1 is grounded. The voltage regulator ZD1 is used to provide the reference voltage V_ref. Select the type of Zener tube ZD1 according to the required reference voltage.

In some embodiments, please continue to refer to FIG. 4 , the comparison circuit 30 includes a second operational amplifier U2, the non-inverting input terminal of the second operational amplifier U2 is connected to the output terminal of the first operational amplifier U1, the first operational amplifier U1 The inverting input terminals of the two operational amplifiers U2 are connected to the reference voltage.

In some embodiments, please continue to refer to FIG. 4 , the comparison circuit 30 further includes a third capacitor C3 , and the third capacitor C3 is connected in series between the non-inverting input terminal of the second operational amplifier U2 and the ground. The comparison circuit 30 further includes a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8 and a ninth resistor R9, and the sixth resistor R6 is connected in series with the non-inverting input terminal of the second operational amplifier U2 and the first operational amplifier. The output end of the amplifier U1, the fifth resistor R5 is connected in series between the inverting input end of the second operational amplifier U2 and the ground, one end of the seventh resistor R7 is connected to the inverting input end of the second operational amplifier U2, and the other end is respectively connected to the inverting input end of the second operational amplifier U2. The eighth resistor R8 and the ninth resistor R9 are connected in series with the output end of the second operational amplifier U2 and the positive electrode Input+ of the charging input end. In addition, the power supply end of the second operational amplifier U2 is connected to the common connection point of the seventh resistor R7, the eighth resistor R8 and the ninth resistor R9.

The second operational amplifier U2 outputs a high-level signal or a low-level signal according to the output signal of the first operational amplifier U1 and the reference voltage. If the output signal of the first operational amplifier U1 is less than the reference voltage, it proves that the voltage supplied to the system controller is When the low-voltage protection value is reached, the second operational amplifier U2 outputs a low-level signal to control the switch circuit 40 at the back end to work in an open-circuit state. If the output signal of the first operational amplifier U1 is greater than the reference voltage, it proves that the power supply to the system controller is When the voltage does not reach the low-voltage protection value, the second operational amplifier U2 outputs a high-level signal to control the switch circuit 40 at the back end to work in the channel state, so that the charger circuit 200 continues to supply power to the system controller.

In some embodiments, please continue to refer to FIG. 4 , the first switch circuit 41 is a transistor Q1 , the second switch circuit 42 is a MOS switch Q2 , and the base of the transistor Q1 is connected to the comparator circuit 30 . At the output end, the collector of the triode Q1 is connected to the gate of the MOS switch Q2 to control the on or off of the MOS switch Q2, and the source and drain of the MOS switch Q2 are serially connected to on the bus of the charging circuit.

Specifically, the switch circuit 40 further includes a tenth resistor R10 , an eleventh resistor R11 , a twelfth resistor R12 , a thirteenth resistor R13 and a fourteenth resistor R14 . The tenth resistor is connected in series between the base of the transistor Q1 and the output end of the second operational amplifier U2, the eleventh resistor is connected in series between the output end of the second operational amplifier U2 and the ground, the twelfth resistor R12 and the first The fourteenth resistor R14 is connected in series between the collector of the transistor Q1 and the gate of the MOS transistor Q2, and the thirteenth resistor R13 is connected in series between the connection point of the twelfth resistor R12 and the fourteenth resistor R14 and the positive electrode of the input terminal of the charging loop. Between Input+, the MOS switch Q2 is disposed on the bus of the charging circuit 200, and its source is connected to the positive electrode Input+ of the charging input, and the MOS switch Q2 is a PMOS switch.

Therefore, if the transistor Q1 is turned off, the potential of the collector terminal of the transistor Q1 is equal to the potential of the positive electrode Input+ of the charging input terminal, and then the potential of the gate terminal of the MOS switch Q2 is equal to the potential of the positive electrode Input+ of the charging input terminal, so the MOS switch transistor Q2 is turned off. , disconnect the charging circuit. If the transistor Q1 is turned on, the potential of the collector terminal of the transistor Q1 is pulled down, and then the MOS switch is turned on, so that the charging circuit works normally and supplies power to the system controller.

Please continue to refer to FIG. 4, and the working principle of the low-voltage protection circuit is described below with reference to each device in FIG. 4, as follows:

The charging loop 200 supplies power to the back-end system controller, while the sampling circuit 10 samples the input terminal voltage Input of the charging loop, the first remote amplifier U1 outputs a sampling signal, and inputs the sampling signal to the non-inverting input terminal of the second operational amplifier U2, At the same time, the voltage regulator tube is broken down by the positive voltage Input+ of the charging input terminal, thereby maintaining the voltage regulation value, which is the reference voltage, and the reference voltage is input to the inverting input terminal of the second operational amplifier U2. If the first operational amplifier The output signal of U1 is greater than the reference voltage, which proves that the powered system controller has not reached the low-voltage protection value, and the second operational amplifier U2 outputs a high-level signal, which acts on the base of the transistor Q1, making the transistor Q1 conduct The PMOS switch tube Q2 is turned on, so that the charging circuit normally supplies power to the system controller. If the sampling signal is less than the reference voltage, it proves that the powered system controller has reached the low-voltage protection value, and the second operational amplifier U2 outputs a low-voltage output. The low-level signal acts on the base of the transistor Q1, so that the transistor Q1 is turned off, and then the PMOS switch Q2 is turned off, disconnecting the charging circuit, completely shutting down the system controller, and preventing the system controller from working in an undervoltage state. , to achieve the purpose of low-voltage protection for the system controller, and the low-voltage protection circuit works stably and can reliably realize low-voltage protection.

An embodiment of the present invention provides a low-voltage protection circuit, which is applied to a charging circuit of a photovoltaic power generation energy storage system. When the charging circuit is low-voltage, a comparison circuit in the low-voltage protection circuit controls the switch circuit to be in an open-circuit working state to disconnect charging. circuit, and then disconnect the power supply for the system controller, so as to prevent the system controller from working in an undervoltage state, and realize reliable low-voltage protection for the system controller. The low-voltage protection circuit is completely realized by a hardware circuit, and has a simple structure, low cost, and strong anti-interference ability, which is more convenient for popularization and application.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; under the idea of the present invention, the technical features in the above embodiments or different embodiments can also be combined, And there are many other variations of the various aspects of the invention as described above, which for the sake of brevity have not been provided in detail; although the invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art will Modifications can be made to the technical solutions recorded in the foregoing embodiments, or equivalent replacements are made to the regional technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions in the embodiments of the present invention. .

Claims (9)

1. A low-voltage protection circuit, applied to the charging circuit of a photovoltaic power generation energy storage system, is characterized in that, comprising: a sampling circuit for sampling the input voltage of the charging circuit; A voltage regulator circuit for providing a reference voltage; a comparison circuit, connected to the sampling circuit and the voltage regulator circuit respectively, for outputting a control signal according to the sampling signal and the reference voltage; and A switch circuit, which is respectively connected to the comparison circuit and the charging circuit, is used for controlling the working state of the charging circuit according to the control signal, and the working state includes an on state and an off state. 2 . The low-voltage protection circuit according to claim 1 , wherein the switch circuit comprises: a first switch circuit and a second switch circuit connected in series, the first switch circuit is further connected to the comparison circuit, 3 . The second switch circuit is also connected to the charging circuit. 3 . The low-voltage protection circuit according to claim 2 , wherein the sampling circuit comprises a first operational amplifier, the non-inverting input terminal of the first operational amplifier is connected to the negative pole of the input voltage of the charging loop, and the one The inverting input terminal of the operational amplifier is connected to the positive pole of the input voltage of the charging circuit, and the output terminal of the first operational amplifier is connected to the comparison circuit. 4. The low-voltage protection circuit according to claim 3, wherein the comparison circuit comprises a second operational amplifier, the non-inverting input terminal of the second operational amplifier is connected to the output terminal of the first operational amplifier, and the The inverting input terminal of the second operational amplifier is respectively connected to the positive pole of the input voltage of the voltage regulator circuit and the charging loop. 5 . The low-voltage protection circuit according to claim 4 , wherein the power supply terminal of the second operational amplifier is connected to the positive pole of the input voltage of the charging loop. 6 . 6 . The low-voltage protection circuit according to claim 4 , wherein the first switch circuit is a triode, the base of the triode is connected to the output end of the second remote amplifier, and the collector of the triode The second switch circuit is connected, and the emitter of the triode is grounded. 7 . The low-voltage protection circuit according to claim 6 , wherein the second switch circuit is a MOS switch, and the collector of the triode is connected to the gate of the MOS switch to control the MOS switch. 8 . On or off of the tube. 8 . The low-voltage protection circuit according to claim 4 , wherein the voltage regulator circuit comprises a voltage regulator tube, and the negative electrode of the voltage regulator tube is connected to the inverting input of the second operational amplifier. 9 . terminal, the positive pole of the Zener tube is grounded. 9. A charger, characterized in that the charger comprises: Photovoltaic power generation system, which is used to generate electric energy using photovoltaic system; The low-voltage protection circuit according to any one of claims 1-8, connected with the photovoltaic power generation system, for low-voltage protection; and The charging circuit is respectively connected with the low-voltage protection circuit and the system controller, and is used for supplying power to the system controller with the electric energy generated by the photovoltaic power generation system.

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