External source under-voltage protection circuit

Abstract

The utility model discloses an external source under-voltage protection circuit, and relates to the technical field of LED under-voltage protection. Comprising an LED driving chip U3, a comparator U1 and an NMOS tube Q1, and the R end of the comparator U1, the K end of the comparator U1, the grid electrode of the NMOS tube Q1, the drain electrode of the NMOS tube Q1 and the EN end of the LED driving chip U3 are sequentially connected in series. According to the circuit provided by the utility model, the input low voltage is detected through a method of adding a reference source on the periphery, and the comparator U1 with the model of TL431 is used as a comparator; when the detection voltage of the R end of the comparator U1 is smaller than 2.5 V, the comparator U1 is turned over, the K end of the comparator U1 is pulled up to be in a high level, the NMOS tube Q1 is conducted, the enabling is pulled down, and the LED driving chip U3 stops outputting. Therefore, the situation that the EN end of the LED driving chip U3 is in an uncertain state at a certain section can be skipped, so that the LED driving chip U3 is not 0, namely 1, and false alarm output does not exist.

Description

Technical Field

[0001] The utility model relates to the technical field of LED undervoltage protection, in particular to an external source undervoltage protection circuit. Background Art

[0002] LEDs are sensitive semiconductor devices with negative temperature characteristics, necessitating stable operation and protection during their application, which led to the concept of LED drivers. LEDs are typically driven by a low voltage of 2 to 3 volts, necessitating the design of complex conversion circuits. Different LED lamps require different power adapters. LED driver undervoltage protection (UVP) automatically cuts off power when the input voltage of the LED driver falls below a certain threshold, preventing damage or unstable operation. The primary purpose of UVP is to ensure that circuits can safely shut down in the event of a voltage shortage, preventing damage or abnormal operation caused by low voltage. In practical applications, UVP circuits can be used in a variety of electronic devices, particularly in systems requiring a stable power supply. For example, in LED driver chips, UVP circuits can ensure timely power cutoff when the voltage drops below a certain threshold, protecting the LED driver chip from damage.

[0003] Existing LED driver solutions rely on the chip enable (EN) pin for undervoltage protection. However, undervoltage at the EN pin is a range and cannot be accurately pinpointed as undervoltage at a specific point. Therefore, it cannot meet the needs of demanding applications. Utility Model Content

[0004] The purpose of the present utility model is to provide an external source undervoltage protection circuit to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] An external source undervoltage protection circuit includes an LED driver chip U3,

[0007] It also includes a comparator U1 and an NMOS tube Q1;

[0008] The R terminal of the comparator U1, the K terminal of the comparator U1, the gate of the NMOS tube Q1, the drain of the NMOS tube Q1, and the EN terminal of the LED driver chip U3 are connected in series in sequence.

[0009] The source of the NMOS transistor Q1 and the A terminal of the comparator U1 are grounded respectively; the reference voltage of the comparator U1 is located inside the device, and there is no need to create another power supply or a reference voltage source of a resistor divider for the secondary terminal; when the internal reference voltage is less than the threshold voltage, the output VPUT is driven to a high level of VIN, and when the internal reference voltage is greater than the threshold voltage, the output VOUT is driven to a low level.

[0010] Preferably, the K terminal of the comparator U1, the diode D11, the resistor R33, and the gate of the NMOS tube Q1 are connected in series in sequence, and the gate of the NMOS tube Q1 and the source of the NMOS tube Q1 are connected in series through a resistor R34; the functions of the resistor R34 are: bias voltage: the resistor between the gate and the source can provide a stable bias voltage to ensure the normal working state of the NMOS tube Q1; discharge resistor: it can discharge a small amount of static electricity between GS to prevent the NMOS tube Q1 from malfunctioning or breaking down.

[0011] Preferably, the K terminal of the comparator U1, the resistor R31, the resistor R16, and the EN terminal of the LED driver chip U3 are connected in series in sequence, and an external resistor R1 and a diode D1 are connected between the resistor R16 and the EN terminal of the LED driver chip U3, and the resistor R1 and the diode D1 are grounded respectively.

[0012] Preferably, the resistor R16, the resistor R30, the resistor R35, and the resistor R32 are connected in series in sequence, the resistor R32 is grounded, and the R terminal of the comparator U1 is electrically connected between the resistor R32 and the resistor R35; the resistors here are mainly used as voltage divider resistors, and the output is fed to the feedback pin after the resistor voltage is divided, so that the feedback pin is equal to the internal reference voltage during steady state;

[0013] The VIN terminal of the LED driver chip U3 is connected to the VCC terminal through the resistor R51. The VIN terminal of the LED driver chip U3 is electrically connected between the resistor R16 and the resistor R30. The capacitor C25 and the capacitor C26 are externally connected between the VIN terminal of the LED driver chip U3 and the resistor R51. The capacitor C25 and the capacitor C26 are grounded respectively.

[0014] Preferably, the DIM terminal of the LED driver chip U3 is externally connected to a capacitor C49, the OSC terminal of the LED driver chip U3 is externally connected to a resistor R21, and the SS terminal of the LED driver chip U3 is externally connected to a capacitor C51. The capacitor C49, resistor R21 and capacitor C51 are grounded respectively.

[0015] Preferably, the COMP terminal of the LED driver chip U3 is externally connected to a capacitor C50, a resistor R15 and a capacitor C52 are connected in parallel to the outside of the capacitor C50, the resistor R15 and the capacitor C52 are connected in series, and the connection between the capacitor C50 and the capacitor C52 is grounded.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0017] The circuit of the present invention detects input low voltage by adding a peripheral reference source, and uses a TL431 comparator U1 as a comparator. When the detection voltage of the R terminal of the comparator U1 is less than 2.5V, the comparator U1 flips over, the K terminal of the comparator U1 is pulled up to a high level, the NMOS tube Q1 is turned on, the enable is pulled low, and the LED driver chip U3 stops outputting. In this way, the EN terminal of the LED driver chip U3 can be skipped in a certain period of uncertain state, so that the LED driver chip U3 is either 0 or 1, and there will be no false alarm output. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 It is a circuit diagram of the entire utility model. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only 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 ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] like Figure 1 As shown, the utility model provides a technical solution: an external source undervoltage protection circuit, including an LED driver chip U3, a comparator U1 and an NMOS tube Q1; the comparator U1 is a TL431; the R terminal of the comparator U1, the K terminal of the comparator U1, the gate of the NMOS tube Q1, the drain of the NMOS tube Q1, and the EN terminal of the LED driver chip U3 are connected in series in sequence, and the source of the NMOS tube Q1 and the A terminal of the comparator U1 are grounded respectively; 431 is a voltage stabilizer commonly used in electronic engineering, and its function is to The voltage is stabilized at a fixed value to protect electronic devices from voltage fluctuations; 431 consists of three main parts: a comparator, a reference voltage source, and an amplifier; the comparator in 431 continuously compares the voltage with the reference voltage; the comparator U1 reference voltage is located inside the device, without having to create another power supply or a reference voltage source of a resistor divider for the secondary terminal; when the internal reference voltage is less than the threshold voltage, the output VPUT is driven to a high level of VIN, and when the internal reference voltage is greater than the threshold voltage, the output VOUT is driven to a low level.

[0022] The K terminal of the comparator U1, the diode D11, the resistor R33, and the gate of the NMOS transistor Q1 are connected in series in sequence, and the gate of the NMOS transistor Q1 and the source of the NMOS transistor Q1 are connected in series via a resistor R34. The function of the resistor R34 is as follows: bias voltage: The resistor between the gate and the source can provide a stable bias voltage to ensure the normal operation of the NMOS transistor Q1. Without this resistor, the source voltage of the MOSFET will change with the change of the load current, causing the gate-source voltage to change, thereby affecting the operation of the NMOS transistor Q1. The function of the resistor R34 is as follows: a discharge resistor: This resistor can discharge a small amount of static electricity between the GS electrodes to prevent the NMOS transistor Q1 from malfunctioning or being broken down. As long as there is a small amount of static electricity, the equivalent capacitance between the GS electrodes of the NMOS transistor Q1 will generate a very high voltage, and this resistor R34 can play a protective role.

[0023] The K terminal of the comparator U1, the resistor R31, the resistor R16, and the EN terminal of the LED driver chip U3 are connected in series in sequence. An external resistor R1 and a diode D1 are connected between the resistor R16 and the EN terminal of the LED driver chip U3. The resistor R1 and the diode D1 are grounded respectively.

[0024] The resistors R16, R30, R35, and R32 are connected in series in sequence, the resistor R32 is grounded, and the R terminal of the comparator U1 is electrically connected between the resistors R32 and R35; the VIN terminal of the LED driver chip U3 is connected to the VCC terminal via the resistor R51, and the VIN terminal of the LED driver chip U3 is electrically connected between the resistor R16 and the resistor R30. External capacitors C25 and C26 are connected between the VIN terminal of the LED driver chip U3 and the resistor R51, and the capacitors C25 and C26 are grounded respectively; the resistors here are mainly used as voltage divider resistors, and the output is fed to the feedback pin after the resistor voltage is divided, so that the feedback pin is equal to the internal reference voltage during steady state;

[0025] The DIM terminal of the LED driver chip U3 is externally connected to a capacitor C49, the OSC terminal of the LED driver chip U3 is externally connected to a resistor R21, and the SS terminal of the LED driver chip U3 is externally connected to a capacitor C51. The capacitor C49, the resistor R21, and the capacitor C51 are grounded respectively; the COMP terminal of the LED driver chip U3 is externally connected to a capacitor C50, and a resistor R15 and a capacitor C52 are connected in parallel to the outside of the capacitor C50. The resistor R15 and the capacitor C52 are connected in series, and the connection between the capacitor C50 and the capacitor C52 is grounded.

[0026] Specific working principle:

[0027] The circuit of the present invention detects input low voltage by adding a peripheral reference source, that is, the comparator U1 of model TL431 is used as a comparator; when the detection voltage of the R terminal of the comparator U1 is less than 2.5V, the comparator U1 flips, the K terminal of the comparator U1 is pulled up to a high level, the NMOS tube Q1 is turned on, the enable is pulled low, and the LED driver chip U3 stops outputting; in this way, the EN terminal of the LED driver chip U3 can be skipped from being in an uncertain state in a certain period, so that the LED driver chip U3 is either 0 or 1, and there will be no false alarm output;

[0028] Comparator U1 provides a reference voltage, which is then used to compare with other voltages in the circuit. After adding NMOS tube Q1, when the detection voltage at the R terminal of comparator U1 is less than 2.5V, NMOS tube Q1 is turned on.

[0029] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An external source undervoltage protection circuit, including an LED driver chip U3, characterized in that: It also includes a comparator U1 and an NMOS tube Q1; The R terminal of the comparator U1, the K terminal of the comparator U1, the gate of the NMOS tube Q1, the drain of the NMOS tube Q1, and the EN terminal of the LED driver chip U3 are connected in series in sequence. The source of the NMOS transistor Q1 and the A terminal of the comparator U1 are grounded respectively.

2. The external source undervoltage protection circuit according to claim 1, characterized in that: The K terminal of the comparator U1, the diode D11, the resistor R33, and the gate of the NMOS transistor Q1 are sequentially connected in series, and the gate of the NMOS transistor Q1 and the source of the NMOS transistor Q1 are connected in series via the resistor R34.

3. The external source undervoltage protection circuit according to claim 1, characterized in that: The K terminal of the comparator U1, the resistor R31, the resistor R16, and the EN terminal of the LED driver chip U3 are connected in series in sequence. An external resistor R1 and a diode D1 are connected between the resistor R16 and the EN terminal of the LED driver chip U3. The resistor R1 and the diode D1 are grounded respectively.

4. The external source undervoltage protection circuit according to claim 3, characterized in that: The resistors R16, R30, R35, and R32 are connected in series in sequence, the resistor R32 is grounded, and the R terminal of the comparator U1 is electrically connected between the resistors R32 and R35; The VIN terminal of the LED driver chip U3 is connected to the VCC terminal through the resistor R51. The VIN terminal of the LED driver chip U3 is electrically connected between the resistor R16 and the resistor R30. The capacitor C25 and the capacitor C26 are externally connected between the VIN terminal of the LED driver chip U3 and the resistor R51. The capacitor C25 and the capacitor C26 are grounded respectively.

5. The external source undervoltage protection circuit according to claim 1, characterized in that: The DIM terminal of the LED driver chip U3 is externally connected to a capacitor C49, the OSC terminal of the LED driver chip U3 is externally connected to a resistor R21, and the SS terminal of the LED driver chip U3 is externally connected to a capacitor C51. The capacitor C49, the resistor R21 and the capacitor C51 are grounded respectively.

6. The external source undervoltage protection circuit according to claim 1, characterized in that: The COMP terminal of the LED driver chip U3 is externally connected to a capacitor C50, and a resistor R15 and a capacitor C52 are connected in parallel to the outside of the capacitor C50. The resistor R15 and the capacitor C52 are connected in series, and the connection between the capacitor C50 and the capacitor C52 is grounded.

Images