An input over-voltage and under-voltage protection circuit

Abstract

The present invention discloses an input over-voltage and under-voltage protection circuit, which relates to the field of circuit technology, and includes: a main control chip, a voltage dividing module, a conduction module and an operational amplifier module; the undervoltage lock pin of the main control chip is connected to the output end of the operational amplifier module, the positive input end of the operational amplifier module is connected to a voltage reference source or a power supply voltage, the positive input end of the power supply of the operational amplifier module is connected to the power supply voltage, the negative input end of the operational amplifier module is connected to the voltage dividing module, and the conduction module is connected in series with the voltage dividing module and is used to control the connection object of the positive input end of the operational amplifier module. The present invention adopts a resistor voltage dividing method, and utilizes the conduction characteristics of an optical coupler and a voltage stabilizing diode to realize the voltage flipping of the operational amplifier and realize input over-voltage protection and input under-voltage protection at the same time. The circuit has the characteristics of simple design and easy adjustment. By adopting fewer devices to realize input over-voltage and under-voltage protection, the required space of the layout is reduced, and the problem of insufficient space of the circuit layout is solved.

Description

Technical Field

[0001] The present invention relates to the field of circuit technology, and in particular to an input over-voltage and under-voltage protection circuit. Background Art

[0002] The input overvoltage and undervoltage protection circuit is an input protection circuit that combines overvoltage and undervoltage into one. Both input overvoltage protection and undervoltage protection refer to corresponding protection for the power input end of the device. In some cases, such as the power supply voltage is too high or the voltage is too low, it may cause damage to the device. Therefore, the device needs to be protected from input overvoltage or input undervoltage to ensure the safety of the device. The protection method can be achieved by using overvoltage protectors, filters and other devices to form a safety protection measure for the device.

[0003] However, the current input over-voltage and under-voltage protection circuit has problems such as low device utilization and a large number of devices that require a lot of space. Therefore, how to provide an input over-voltage and under-voltage protection circuit that reduces the number of devices and improves device utilization efficiency to solve the problem of insufficient circuit layout space is a technical issue that the industry needs to solve urgently. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides an input over-voltage and under-voltage protection circuit to solve the problems of low component utilization and a large number of components required to occupy a large amount of space in the input over-voltage and under-voltage protection circuit in the prior art.

[0005] According to a first aspect, an embodiment of the present invention provides an input over-voltage and under-voltage protection circuit, comprising:

[0006] Main control chip, voltage divider module, conduction module and operational amplifier module;

[0007] The undervoltage lockout pin of the main control chip is connected to the output end of the operational amplifier module, the non-inverting input end of the operational amplifier module is connected to a voltage reference source or a power supply voltage, the positive power input end of the operational amplifier module is connected to the power supply voltage, the inverting input end of the operational amplifier module is connected to the voltage divider module, and the conduction module is connected in series with the voltage divider module and is used to control the connection object of the non-inverting input end of the operational amplifier module.

[0008] In combination with the first aspect, in a first implementation of the first aspect, the operational amplifier module includes:

[0009] Operational amplifier, optocoupler light receiver and N-channel MOS tube;

[0010] The first pin of the operational amplifier is connected to the gate of the N-channel MOS tube, the drain of the N-channel MOS tube is connected to the undervoltage lockout pin of the main control chip, the source of the N-channel MOS tube is grounded, the second pin of the operational amplifier is grounded, the third pin of the operational amplifier is connected to a voltage reference source or is connected to a power supply voltage through a light receiver of the optical coupler when the optical coupler is turned on, the fourth pin of the operational amplifier is connected to the voltage divider module, and the fifth pin of the operational amplifier is connected to the power supply voltage;

[0011] The first pin is an output terminal, the second pin is a negative power input terminal, the third pin is a positive input terminal, the fourth pin is an inverting input terminal, the fifth pin is a positive power input terminal, and the optocoupler is controlled to be turned on or off by the conduction module.

[0012] In combination with the first embodiment of the first aspect, in the second embodiment of the first aspect, a fourth voltage-dividing resistor is arranged between the source and the gate of the N-channel MOS tube.

[0013] In combination with the first implementation of the first aspect, in a third implementation of the first aspect, a non-inverting input resistor is connected between the third pin of the operational amplifier and the power reference source.

[0014] In combination with the first implementation of the first aspect, in a fourth implementation of the first aspect, the voltage division module includes:

[0015] A first voltage-dividing resistor, a second voltage-dividing resistor and a third voltage-dividing resistor connected in series, one end of the first voltage-dividing resistor is grounded, the other end of the first voltage-dividing resistor is connected to one end of the second voltage-dividing resistor, the other end of the second voltage-dividing resistor is connected to one end of the third voltage-dividing resistor, and the other end of the third voltage-dividing resistor is connected to an input voltage;

[0016] The fourth pin of the operational amplifier is connected between the first voltage-dividing resistor and the second voltage-dividing resistor.

[0017] In combination with the fourth implementation of the first aspect, in a fifth implementation of the first aspect, the conduction module includes:

[0018] The light source of the Zener diode and the optocoupler;

[0019] The cathode of the voltage stabilizing diode is connected to the cathode of the light source of the optocoupler, the cathode of the voltage stabilizing diode is grounded, and the anode of the light source of the optocoupler is connected between the second voltage dividing resistor and the third voltage dividing resistor.

[0020] In combination with the fifth implementation of the first aspect, in the sixth implementation of the first aspect, the voltage of the power reference source is greater than the voltage between the connection point between the operational amplifier and the voltage divider module.

[0021] In combination with the first aspect, in a seventh implementation of the first aspect, the main control chip is a PWM chip.

[0022] In combination with the fifth embodiment of the first aspect, in the eighth embodiment of the first aspect, the light source of the optical coupler is a light emitting diode.

[0023] In combination with the fifth embodiment of the first aspect, in the ninth embodiment of the first aspect, the light receiver of the optical coupler is a phototransistor.

[0024] The input over-voltage and under-voltage protection circuit of the present invention adopts a resistor voltage division method and utilizes the conduction characteristics of an optocoupler and a voltage stabilizing diode to realize voltage flipping of an operational amplifier and simultaneously realize input over-voltage protection and input under-voltage protection for a device to be protected. The circuit has the characteristics of simple design and easy adjustment. By adopting fewer devices to realize input over-voltage and under-voltage protection, the required space for layout is reduced, and the problem of insufficient space for circuit layout is solved. The circuit is suitable for module power supplies with a small volume and densely packed devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] in:

[0027] Figure 1 The circuit diagram of the input over-voltage and under-voltage protection circuit provided by the present invention is shown. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] The input overvoltage and undervoltage protection circuit is an input protection circuit that combines overvoltage and undervoltage into one. Both input overvoltage protection and undervoltage protection refer to corresponding protection for the power input end of the device. In some cases, such as the power supply voltage is too high or the voltage is too low, it may cause damage to the device. Therefore, the device needs to be protected from input overvoltage or input undervoltage to ensure the safety of the device. The protection method can be achieved by using overvoltage protectors, filters and other devices to form a safety protection measure for the device.

[0030] However, the current two-in-one input overvoltage and undervoltage protection circuit has disadvantages such as low device utilization, a large number of devices required for related design circuits, and a large amount of space occupied during layout design.

[0031] Therefore, how to provide an input over-voltage and under-voltage protection circuit that reduces the number of components and improves the utilization efficiency of components to solve the problem of insufficient circuit layout space is a technical issue that needs to be urgently solved in the industry.

[0032] In order to solve the above problems, an input over-voltage and under-voltage protection circuit is provided in this specification. Figure 1 As shown, the circuit includes:

[0033] The main control chip includes the device to be protected, the voltage divider module, the conduction module and the operational amplifier module.

[0034] Among them, the undervoltage lockout pin of the main control chip is connected to the output end of the operational amplifier module, the non-phase input end of the operational amplifier module is connected to a voltage reference source or a power supply voltage, the positive power input end of the operational amplifier module is connected to the power supply voltage, the inverting input end of the operational amplifier module is connected to the voltage divider module, the conduction module is connected in series with the voltage divider module and is used to control the connection object of the non-phase input end of the operational amplifier module, that is, whether the non-phase input end of the operational amplifier module is connected to the voltage reference source or the power supply voltage.

[0035] The operational amplifier module includes:

[0036] Operational amplifier, optocoupler light receiver and N-channel MOS tube;

[0037] The first pin of the operational amplifier is connected to the gate of the N-channel MOS tube, the drain of the N-channel MOS tube is connected to the undervoltage lock pin of the main control chip, the source of the N-channel MOS tube is grounded, the second pin of the operational amplifier is grounded, the third pin of the operational amplifier is connected to the voltage reference source or is connected to the power supply voltage through the light receiver of the optical coupler when the optical coupler is turned on, the fourth pin of the operational amplifier is connected to the voltage divider module, the fifth pin of the operational amplifier is connected to the power supply voltage, and a positive input resistor is connected between the third pin of the operational amplifier and the power supply reference source.

[0038] An operational amplifier is an analog circuit module that uses differential voltage input to generate a single-ended voltage output. It can amplify the input signal and perform mathematical operations such as addition, subtraction, multiplication, division, microblocking, division, and integration. In this embodiment, the first pin is the output terminal, the second pin is the negative input terminal of the power supply, the third pin is the positive input terminal, the fourth pin is the inverting input terminal, and the fifth pin is the positive input terminal of the power supply. The optocoupler is controlled to be turned on or off through the conduction module.

[0039] A fourth voltage-dividing resistor R6 is provided between the source and the gate of the N-channel MOS tube.

[0040] The voltage divider module includes:

[0041] A first voltage-dividing resistor R1, a second voltage-dividing resistor R2 and a third voltage-dividing resistor R3 are connected in series, one end of the first voltage-dividing resistor R1 is grounded, the other end of the first voltage-dividing resistor R1 is connected to one end of the second voltage-dividing resistor R2, the other end of the second voltage-dividing resistor R2 is connected to one end of the third voltage-dividing resistor R3, the other end of the third voltage-dividing resistor R3 is connected to the input voltage, and the fourth pin of the operational amplifier is connected between the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, that is, Figure 1 Point B in .

[0042] The conduction module includes:

[0043] The light source of the Zener diode D1 and the optocoupler, the voltage divider module of the Zener diode D1 and the optocoupler in parallel Figure 1 Between point A in and the ground terminal.

[0044] The cathode of the voltage stabilizing diode D1 is connected to the cathode of the light source of the optocoupler, the cathode of the voltage stabilizing diode is grounded, and the anode of the light source of the optocoupler is connected between the second voltage dividing resistor R2 and the third voltage dividing resistor R3.

[0045] In this embodiment, the light source of the optocoupler is a light emitting diode, and the light receiver of the optocoupler is a phototransistor.

[0046] like Figure 1 As shown, V REF Represents the voltage reference source, V IN Indicates input voltage, V CC Indicates the supply voltage, UVLO (under voltage lock out) indicates the under voltage lock pin of the main control chip, D1 indicates the voltage regulator diode, OT-A and OT-B are both optocouplers, OT-A indicates the light receiver of the optocoupler, OT-B indicates the light source of the optocoupler, Q1 indicates the N-channel MOS tube, U1 indicates the operational amplifier, and the third pin of U1 ( Figure 1 Pin 3 in the middle) is the non-inverting input terminal, and the fourth pin of U1 ( Figure 1Pin 4 in the middle) is the reverse input terminal, and the first pin of U1 ( Figure 1 Pin 1 in the middle is the output terminal. For U1, when the voltage at the in-phase input terminal is greater than the voltage at the inverting input terminal, the op amp output terminal outputs a high level. When the voltage at the in-phase input terminal is less than the voltage at the inverting input terminal, the op amp output terminal outputs a low level.

[0047] In this embodiment, the main control chip adopts a PWM chip. When the UVLO pin is at a low level, the main control chip has no drive output, the main control chip does not work, and the protection device is in a protection state.

[0048] When the circuit works:

[0049] When the input voltage V IN When the voltage is lower than the preset threshold, the voltage zener diode D1 is not turned on, and the voltage at point B is divided by the first to third voltage-dividing resistors R1, R2, and R3 and then input to the fourth pin of the operational amplifier U1. Therefore, it can be obtained:

[0050]

[0051] Among them, V A Indicates the voltage at point A.

[0052]

[0053] Among them, V B Indicates the voltage at point B.

[0054] It can be seen that V A is greater than V B And through the configuration of the resistor, the V B Adjust to less than V REF , so that the first pin of the operational amplifier U1 outputs a high level, making the voltage at point C greater than the gate-to-source threshold voltage V of the N-channel MOS tube Q1 GS th, the N-channel MOS tube Q1 is turned on, the UVLO pin outputs a low level, and the main control chip does not work, thus achieving input undervoltage protection.

[0055] When the input voltage V IN The voltage at point A increases gradually. When the voltage rises to the point where the voltage-stabilizing diode D1 is turned on, the voltage at point A is clamped at V A =V D1 +V OT-B , where V D1 Represents the voltage of Zener diode D1, V OT-B Indicates the voltage of the light source of the optocoupler. At this time, the optocoupler is in the on state, and the supply voltage V CCThe voltage of the third pin of the operational amplifier U1 is higher than the voltage of the fourth pin. Therefore, the first pin of the operational amplifier U1 outputs a high level. Similarly, the voltage at point C is greater than the gate-to-source threshold voltage V of the N-channel MOS tube Q1. GS th, the N-channel MOS tube Q1 is turned on, the UVLO pin outputs a low level, and the main control chip does not work, thus achieving input overvoltage protection.

[0056] The input over-voltage and under-voltage protection circuit of the present invention adopts a resistor voltage division method and utilizes the conduction characteristics of an optocoupler and a voltage stabilizing diode to realize voltage flipping of an operational amplifier and simultaneously realize input over-voltage protection and input under-voltage protection for a device to be protected. The circuit has the characteristics of simple design and easy adjustment. By adopting fewer devices to realize input over-voltage and under-voltage protection, the required space for layout is reduced, and the problem of insufficient space for circuit layout is solved. The circuit is suitable for module power supplies with a small volume and densely packed devices.

[0057] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An input over-voltage and under-voltage protection circuit, characterized in that: include: Main control chip, voltage divider module, conduction module and operational amplifier module; The undervoltage lockout pin of the main control chip is connected to the output end of the operational amplifier module, the non-inverting input end of the operational amplifier module is connected to a voltage reference source or a power supply voltage, the positive power input end of the operational amplifier module is connected to the power supply voltage, the inverting input end of the operational amplifier module is connected to the voltage divider module, and the conduction module is connected in series with the voltage divider module and is used to control the connection object of the non-inverting input end of the operational amplifier module.

2. The input over-voltage and under-voltage protection circuit according to claim 1, characterized in that: The operational amplifier module comprises: Operational amplifier, optocoupler light receiver and N-channel MOS tube; The first pin of the operational amplifier is connected to the gate of the N-channel MOS tube, the drain of the N-channel MOS tube is connected to the undervoltage lockout pin of the main control chip, the source of the N-channel MOS tube is grounded, the second pin of the operational amplifier is grounded, the third pin of the operational amplifier is connected to a voltage reference source or is connected to a power supply voltage through a light receiver of the optical coupler when the optical coupler is turned on, the fourth pin of the operational amplifier is connected to the voltage divider module, and the fifth pin of the operational amplifier is connected to the power supply voltage; The first pin is an output terminal, the second pin is a negative power input terminal, the third pin is a positive input terminal, the fourth pin is an inverting input terminal, the fifth pin is a positive power input terminal, and the optocoupler is controlled to be turned on or off by the conduction module.

3. The input over-voltage and under-voltage protection circuit according to claim 2, characterized in that: A fourth voltage-dividing resistor is arranged between the source and the gate of the N-channel MOS tube.

4. The input over-voltage and under-voltage protection circuit according to claim 2, characterized in that: A positive input resistor is connected between the third pin of the operational amplifier and the power reference source.

5. The input over-voltage and under-voltage protection circuit according to claim 2, characterized in that: The voltage divider module comprises: A first voltage-dividing resistor, a second voltage-dividing resistor and a third voltage-dividing resistor connected in series, one end of the first voltage-dividing resistor is grounded, the other end of the first voltage-dividing resistor is connected to one end of the second voltage-dividing resistor, the other end of the second voltage-dividing resistor is connected to one end of the third voltage-dividing resistor, and the other end of the third voltage-dividing resistor is connected to an input voltage; The fourth pin of the operational amplifier is connected between the first voltage-dividing resistor and the second voltage-dividing resistor.

6. The input over-voltage and under-voltage protection circuit according to claim 5, characterized in that: The conduction module comprises: The light source of the Zener diode and the optocoupler; The cathode of the voltage stabilizing diode is connected to the cathode of the light source of the optocoupler, the cathode of the voltage stabilizing diode is grounded, and the anode of the light source of the optocoupler is connected between the second voltage dividing resistor and the third voltage dividing resistor.

7. The input over-voltage and under-voltage protection circuit according to claim 6, characterized in that: The voltage of the power reference source is greater than the voltage between the connection point between the operational amplifier and the voltage divider module.

8. The input over-voltage and under-voltage protection circuit according to claim 1, characterized in that: The main control chip is a PWM chip.

9. The input over-voltage and under-voltage protection circuit according to claim 6, characterized in that: The light source of the optical coupler is a light emitting diode.

10. The input over-voltage and under-voltage protection circuit according to claim 6, characterized in that: The light receiver of the optical coupler adopts a phototransistor.

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