An under-voltage protection circuit

Abstract

The application discloses an under-voltage protection circuit, comprising: an input end connected with a power supply; an output end connected with a power consumer; a first capacitor, one end of which is connected with the input end and the other end of which is grounded; a first transistor, the drain of which is connected with the input end and the one end of the first capacitor, and the source of which is grounded; a second transistor, the gate of which is connected with the gate of the first transistor, the source of which is grounded, and the drain of which is connected with a signal feedback end; a second capacitor, one end of which is connected with a line between the gate of the first transistor and the gate of the second transistor, and the other end of which is grounded; and a voltage stabilizer, one pin of which is connected with the input end, the second pin of which is connected with the output end, and the third pin of which is grounded. The application has simple design, reduces design complexity, and reduces the number of components, thereby helping to reduce cost and simplify the production process.

Description

Technical Field

[0001] This application relates to the field of circuit technology, and in particular to an undervoltage protection circuit. Background Technology

[0002] High-voltage input DC / DC converters sometimes require undervoltage protection. However, the power supply method of the control chip makes the design of the undervoltage protection circuit difficult. There are two power supply methods for high-voltage control chips: one is linear power supply, which steps down the input voltage to the chip's turn-on voltage; the other is RC + auxiliary winding power supply. The former has more components and occupies a lot of product space, while the latter has fewer components but cannot set input undervoltage protection. Therefore, an additional circuit is needed to implement the product's input undervoltage protection. None of the above solutions can well meet the user's needs. Summary of the Invention

[0003] The purpose of this application embodiment is to provide an undervoltage protection circuit, including: The input terminal is connected to the power supply component; The output terminal connects to the electrical component. The first capacitor has one end connected to the input terminal and the other end grounded. The first transistor has its drain connected to the input terminal and one end of the first capacitor, and its source grounded. The second transistor has its gate connected to the gate of the first transistor, its source grounded, and its drain connected to the signal feedback terminal. The second capacitor has one end connected to the line between the gate of the first transistor and the gate of the second transistor, and the other end grounded. The voltage regulator has its first pin connected to the input terminal, its second pin connected to the output terminal, and its third pin grounded.

[0004] As an optional embodiment, the input terminal is connected to one end of the first resistor, the other end of the first resistor is connected to the first capacitor and the second resistor respectively, and the second resistor is grounded.

[0005] As an optional embodiment, a third resistor is connected on the line between the first resistor and the second resistor, and the other end of the third resistor is connected to the first pin of the voltage regulator and the drain of the first transistor, respectively.

[0006] As an optional embodiment, the second pin of the voltage regulator is connected to the output terminal via a fourth resistor.

[0007] As an optional embodiment, a fifth resistor and a sixth resistor are connected sequentially on the line between the fourth resistor and the second pin of the voltage regulator, and the sixth resistor is grounded.

[0008] The beneficial effects of the embodiments of this application are as follows: This application features a simple design, reducing design complexity and the number of components, thereby helping to lower costs and simplify the manufacturing process. This application controls the signal feedback terminal's level by controlling the on / off state of the first and second transistors, thus controlling whether the output terminal outputs a normal voltage. Simultaneously, the circuit can set a hysteresis voltage between the turn-on and turn-off voltages; increasing this hysteresis voltage effectively prevents repeated restarts caused by input jitter. Attached Figure Description

[0009] Figure 1 This is a circuit diagram of an embodiment of this application.

[0010] in, VIN, input terminal; VCC, output terminal; FB, signal feedback terminal; C1, first capacitor; C2, second capacitor; Q2, first transistor; Q1, second transistor; R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor; U1, voltage regulator. Detailed Implementation

[0011] Various embodiments and features of this application are described herein with reference to the accompanying drawings.

[0012] It should be understood that various modifications can be made to the embodiments described herein. Therefore, the above description should not be considered as limiting, but merely as an example of embodiments. Other modifications within the scope and spirit of this application will be apparent to those skilled in the art.

[0013] The accompanying drawings, which are included in and form part of this specification, illustrate embodiments of the present application and, together with the general description of the present application given above and the detailed description of the embodiments given below, serve to explain the principles of the present application.

[0014] These and other features of this application will become apparent from the following description of preferred forms of embodiments given as non-limiting examples, with reference to the accompanying drawings.

[0015] It should also be understood that although this application has been described with reference to some specific examples, those skilled in the art can certainly implement many other equivalent forms of this application.

[0016] The above and other aspects, features and advantages of this application will become more apparent when taken in conjunction with the accompanying drawings and in view of the following detailed description.

[0017] Specific embodiments of this application are described thereafter with reference to the accompanying drawings; however, it should be understood that the claimed embodiments are merely examples of this application, which can be implemented in various ways. Well-known and / or repeated functions and structures are not described in detail to avoid unnecessary or redundant details that could obscure the application. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as the basis and representative basis for the claims to teach those skilled in the art to use this application in a variety of substantially any suitable detailed structures.

[0018] This specification may use the phrases “in one embodiment,” “in another embodiment,” “in yet another embodiment,” or “in other embodiments,” all of which may refer to one or more of the same or different embodiments according to this application.

[0019] An undervoltage protection circuit according to an embodiment of this application, such as Figure 1 As shown, it includes input terminal VIN, output terminal VCC, first capacitor C1, first transistor Q2 (N-channel MOSFET), second transistor Q1 (N-channel MOSFET), second capacitor C2, and voltage regulator U1.

[0020] The input terminal VIN is connected to the power supply component, and the output terminal VCC is connected to the power consumption component. One end of the first capacitor C1 is connected to the input terminal VIN, and the other end is grounded.

[0021] The input terminal VIN is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the first capacitor C1 and the second resistor R2, which is grounded. The first resistor R1 and the second resistor R2 act as a voltage divider, so that when the voltage at pin 1 of the voltage regulator U1 reaches 2.5V, the voltage regulator U1 starts to work. The first capacitor C1 acts as a filter, filtering the voltage at pin 1 of the voltage regulator U1. At the same time, the input voltage charges the first capacitor C1 through the first resistor R1, causing the voltage at pin 1 of the voltage regulator U1 to rise slowly.

[0022] The drain of the first transistor Q2 is connected to the input terminal VIN and one end of the first capacitor C1, and its source is grounded. When the first transistor Q2 is off, the voltage at pin 1 of the regulator U1 is the voltage divided by the first resistor R1 and the second resistor R2. When the first transistor Q2 is on, the voltage at pin 1 of the regulator U1 is the voltage divided by the first resistor R1, the second resistor R2 and the third resistor R3.

[0023] A third resistor R3 is connected in the line between the first resistor R1 and the second resistor R2. The other end of the third resistor R3 is connected to pin 1 of the voltage regulator U1 and the drain of the first transistor Q2. When the first transistor Q2 is turned on, the third resistor R3 and the second resistor R2 are connected in parallel, and the voltage at pin 1 of the voltage regulator U1 drops, which is used to set the hysteresis voltage value for turning on and off.

[0024] The gate of the second transistor Q1 is connected to the gate of the first transistor Q2, its source is grounded, and its drain is connected to the feedback pin FB of the control chip. When the second transistor Q1 is off, the signal feedback pin FB is floating, and the control chip is working; when the second transistor Q1 is on, the FB pin of the control chip is pulled low to ground, and the control chip is not working.

[0025] One end of the second capacitor C2 is connected to the line between the gate of the first transistor Q2 and the gate of the second transistor Q1, and the other end is grounded. The second capacitor C2 acts as a filter, filtering the gates of the second transistor Q1 and the first transistor Q2. The voltage at pin 1 of the voltage regulator U1 is set to enable or disable it. When it is active, the voltage at pin 2 decreases, turning off the second transistor Q1 and the first transistor Q2; when it is disabled, the voltage at pin 2 increases, turning on the second transistor Q1 and the first transistor Q2.

[0026] The voltage regulator U1 has its first pin connected to the input terminal VIN, its second pin connected to the control chip's VCC, and its third pin grounded. The second pin of the voltage regulator U1 is connected to the control chip's VCC via a fourth resistor R4.

[0027] Specifically, a fifth resistor R5 and a sixth resistor R6 are connected sequentially on the line between the fourth resistor R4 and pin 2 of the voltage regulator U1, with the sixth resistor R6 grounded. The fourth resistor R4 is the current-limiting resistor of the voltage regulator U1, and the fifth resistor R5 and the sixth resistor R6 are voltage-dividing resistors used to set the turn-on voltage of the second transistor Q1.

[0028] In summary, the working principle of the undervoltage protection circuit is as follows: Power-on process: When the input terminal VIN is powered, the VCC voltage of the control chip is quickly established, and the second capacitor C2 is charged through the fourth resistor R4 and the fifth resistor R5. After the voltage is divided by the sixth resistor R6 to reach the turn-on voltage of the second transistor Q1 and the first transistor Q2, the second transistor Q1 and the first transistor Q2 are turned on, and the signal feedback terminal FB of the control chip is pulled low to ground potential, so that the control chip remains in a no-output state; the first transistor Q2 pulls the lower end of the third resistor R3 low to ground potential, forming a parallel current shunting with the second resistor R2.

[0029] The VIN power supply slowly charges the first capacitor C1 through the first resistor R1. When the voltage reaches the turn-on voltage, the voltage at pin 1 of the voltage regulator U1 is 2.5V, and the voltage regulator U1 is working. The voltage at pin 2 decreases, the second transistor Q1 and the first transistor Q2 are turned off, the signal feedback terminal FB of the control chip is left floating, and the control chip maintains an output state. The lower end of the third resistor R3 is left floating and does not form a parallel current shunting with the second resistor R2, so the voltage at pin 1 of U1 rises further.

[0030] Shutdown process: The input voltage VIN decreases. Since the third resistor R3 is not connected in parallel with the second resistor R2 to shunt the current at this time, the input voltage must be reduced to a level lower than the turn-on voltage to make pin 1 of the regulator U1 become 2.5V. After reaching the undervoltage point, the regulator U1 stops working, the voltage of its pin 2 recovers, the second transistor Q1 and the first transistor Q2 are turned on, and the control chip has no output.

[0031] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. An undervoltage protection circuit, characterized in that, include: The input terminal is connected to the power supply component; The output terminal connects to the electrical component. The first capacitor has one end connected to the input terminal and the other end grounded. The first transistor has its drain connected to the input terminal and one end of the first capacitor, and its source grounded. The second transistor has its gate connected to the gate of the first transistor, its source grounded, and its drain connected to the signal feedback terminal. The second capacitor has one end connected to the line between the gate of the first transistor and the gate of the second transistor, and the other end grounded. The voltage regulator has its first pin connected to the input terminal, its second pin connected to the output terminal, and its third pin grounded.

2. The undervoltage protection circuit as described in claim 1, characterized in that, The input terminal is connected to one end of the first resistor, and the other end of the first resistor is connected to the first capacitor and the second resistor respectively. The second resistor is grounded.

3. The undervoltage protection circuit as described in claim 2, characterized in that, A third resistor is connected on the line between the first resistor and the second resistor, and the other end of the third resistor is connected to the first pin of the voltage regulator and the drain of the first transistor.

4. The undervoltage protection circuit as described in claim 1, characterized in that, The second pin of the voltage regulator is connected to the output terminal through the fourth resistor.

5. The undervoltage protection circuit as described in claim 4, characterized in that, A fifth resistor and a sixth resistor are connected sequentially on the line between the fourth resistor and the second pin of the voltage regulator, and the sixth resistor is grounded.

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