An LED driver power supply with low-voltage protection that can adapt to voltage fluctuations

Abstract

The invention relates to the technical field of LED driving power supply, in particular to an LED driving power supply with low voltage protection capable of adapting to voltage fluctuations, wherein a main circuit of the LED driving power supply is provided with a rectifier filter unit and a flyback isolation constant current unit; an input end of the low voltage protection unit is electrically connected to a differential and common mode interference filtering end of the rectifier filter unit, and a control end and a power reduction end of the low voltage protection unit are electrically connected to a control end and a power reduction end of a flyback isolation constant current unit respectively; the flyback isolation constant current unit is preset with U1 and U2, and U1 is greater than U2; the low voltage protection unit receives Uac from the rectifier filter unit and compares it with U1 and U2 respectively; when U2<Uac<U1, the working power of the flyback isolation constant current unit is adjusted in a positive correlation according to the size of Uac; when Uac<U2, the flyback isolation constant current unit is turned off, otherwise it is turned on; and the problem that the low voltage protection of the LED driving power supply cannot be applied to a power grid environment with large voltage fluctuations is solved.

Description

Technical Field

[0001] The invention relates to the technical field of LED driving power supplies, and in particular to an LED driving power supply with low voltage protection capable of adapting to voltage fluctuations. Background Art

[0002] At present, there are fewer power grid resources in remote areas and the power supply facilities are relatively old, so there will be large fluctuations in the input city electricity and unstable power supply. On this basis, if the power supply lines are too long, there are peak power consumption and severe natural environments (such as thunderstorms, blizzards, etc.), the voltage fluctuations will be more obvious and the power supply stability will be worse.

[0003] The given input voltage of most LED driver power products on the market is within the range of 198V-264V, that is, there is a range limit of plus or minus 10% for normal fluctuations of the mains. When the input voltage is low or under voltage, the LED driver power supply needs to maintain its original power, which will increase its input current, which may cause irreversible damage to the circuit of the LED driver power supply and cause the power supply to stop working.

[0004] For this reason, the low-voltage protection logic of most LED driver power supplies on the market uses the method of directly stopping the LED driver power supply from working to protect the circuit when the low-voltage threshold is detected. However, when the LED driver power supply is used in remote areas, voltage fluctuations are the norm, which will cause the LED driver power supply to be in a shutdown state for a long time, seriously affecting the normal use of the LED driver power supply.

[0005] Therefore, in response to this situation, it is an urgent problem to design an LED driver power supply that can adapt to voltage fluctuations, adaptively reduce power to maintain safe circuit operation when the voltage drops, shut down for protection when the voltage is severely low, and sense the disappearance of severe low voltage to automatically resume power. Summary of the invention

[0006] In view of the above defects, the purpose of the present invention is to provide an LED driving power supply with low voltage protection that can adapt to voltage fluctuations, thereby solving the problem that the low voltage protection of the LED driving power supply cannot be applied to a power grid environment with large voltage fluctuations.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A low-voltage protection LED driving power supply capable of adapting to voltage fluctuations, comprising an LED driving power supply main circuit and a low-voltage protection unit, wherein the LED driving power supply main circuit is provided with a rectifier filter unit and a flyback isolation constant current unit; the input end of the low-voltage protection unit is electrically connected to the differential and common mode interference filtering end of the rectifier filter unit, the control end of the low-voltage protection unit is electrically connected to the control end of the flyback isolation constant current unit, and the power reduction end of the low-voltage protection unit is electrically connected to the power reduction end of the flyback isolation constant current unit;

[0009] The flyback isolation constant current unit is preset with a normal operating voltage U1 and a shutdown threshold U2, and the normal operating voltage U1 is greater than the shutdown threshold U2;

[0010] The low voltage protection unit is used to receive the input voltage Uac from the rectifier and filter unit and compare it with the normal working voltage U1 and the shutdown threshold U2 respectively;

[0011] When the input voltage Uac is lower than the normal working voltage U1 but higher than the shutdown threshold U2, the low voltage protection unit adjusts the working power of the flyback isolation constant current unit in a positive correlation according to the magnitude of the input voltage Uac;

[0012] When the input voltage Uac is lower than the shutdown threshold U2, the low voltage protection unit turns off the flyback isolation constant current unit, otherwise the flyback isolation constant current unit is turned on.

[0013] Furthermore, it also includes an APFC unit; the first end and the second end of the APFC unit are electrically connected to the front end and the end of the LC filter of the rectifier and filter unit respectively, and the power supply end of the APFC unit is electrically connected to the second power supply end of the flyback isolation constant current unit.

[0014] Further, the low voltage protection unit includes a diode D6, a diode D10, a capacitor CB3, a power reduction control circuit and a switch control circuit; the anode of the diode D6 and the anode of the diode D10 are both used as the input end of the low voltage protection unit, the output end of the switch control circuit is used as the control end of the low voltage protection unit, and the output end of the power reduction control circuit is used as the power reduction end of the low voltage protection unit;

[0015] The cathode of the diode D6, the cathode of the diode D10, the first end of the power reduction control circuit, and the first end of the switch control circuit are all electrically connected to one end of the capacitor CB3, and the second end of the power reduction control circuit, the second end of the switch control circuit, and the other end of the capacitor CB3 are all grounded;

[0016] The power reduction control circuit is used to receive the input voltage Uac and compare it with the normal working voltage U1; when the input voltage Uac is lower than the normal working voltage U1 but higher than the shutdown threshold U2, the power reduction control circuit lowers the working power of the flyback isolation constant current unit in a positive correlation according to the magnitude of the input voltage Uac;

[0017] The switch control circuit is used to receive the input voltage Uac and compare it with the shutdown threshold U2; when the input voltage Uac is lower than the preset shutdown threshold U2, the switch control circuit turns off the flyback isolation constant current unit, otherwise it turns on the flyback isolation constant current unit.

[0018] Furthermore, the power reduction control circuit includes a voltage regulator tube ZD1, a voltage regulator tube ZD2, a conduction module, a resistor R24, a resistor R36, a resistor R35 and a capacitor C12; the cathode of the voltage regulator tube ZD1 is used as the first end of the power reduction control circuit, one end of the resistor R35 is used as the second end of the power reduction control circuit, and the first end of the conduction module is used as the output end of the power reduction control circuit;

[0019] The anode of the voltage regulator tube ZD1 is electrically connected to the cathode of the voltage regulator tube ZD2, the anode of the voltage regulator tube ZD2 is electrically connected to one end of the resistor R24, the other end of the resistor R24 ​​is electrically connected to one end of the resistor R36, the other end of the resistor R36, the other end of the resistor R35, and the second end of the conduction module are all electrically connected to one end of the capacitor C12, and one end of the resistor R35 is electrically connected to the other end of the capacitor C12;

[0020] When the voltage at the second end of the conduction module is lower than the voltage at the first end, the conduction module is turned on, and the operating power of the flyback isolation constant current unit is adjusted in a positive correlation according to the magnitude of the voltage at the second end of the conduction module.

[0021] Furthermore, the conduction module is a diode D11, an anode of the diode D11 is used as a first end of the conduction module, and a cathode of the diode D11 is used as a second end of the conduction module.

[0022] Further, the switch control circuit includes a resistor R25, a resistor R37, a resistor R38, a resistor R39, a resistor R40 and a capacitor C14; one end of the resistor R25 is used as a first end of the switch control circuit, one end of the resistor R40 is used as an output end of the switch control circuit, and the other end of the resistor R40 is used as a second end of the switch control circuit;

[0023] The other end of the resistor R25 is electrically connected to one end of the resistor R37, the other end of the resistor R37 and one end of the capacitor C14 are electrically connected to one end of the resistor R38, the other end of the resistor R38 and one end of the resistor R39 are electrically connected to one end of the resistor R40, and the other end of the capacitor C14 and the other end of the resistor R39 are electrically connected to the other end of the resistor R40.

[0024] Further, the flyback isolation constant current unit includes an LED driver chip IC2, a capacitor C15, a capacitor C8, a resistor R17, a diode D8, a resistor R16, a resistor R31, a resistor R32 and a capacitor C10; one end of the resistor R17 is used as the second power supply end of the flyback isolation constant current unit, one end of the capacitor C15 is used as the control end of the flyback isolation constant current unit, and one end of the capacitor C8 is used as the power reduction end of the flyback isolation constant current unit;

[0025] The other end of the resistor R17 is electrically connected to the cathode of the diode D8, the anode of the diode D8 is electrically connected to one end of the resistor R16, the other end of the resistor R16, one end of the resistor R31, one end of the resistor R32, and one end of the capacitor C10 are all electrically connected to the detection end of the LED driver chip IC2, and the other end of the resistor R31, the other end of the resistor R32, and the other end of the capacitor C10 are all grounded;

[0026] One end of the capacitor C15 is electrically connected to the chip control end of the LED driver chip IC2, and the other end of the capacitor C15 is grounded;

[0027] One end of the capacitor C8 is electrically connected to the analog dimming end of the LED driver chip IC2, and the other end of the capacitor C8 is grounded.

[0028] Further, the APFC unit includes an APFC driver chip IC1, a resistor R1, a resistor R2, a resistor R3, a resistor RS1, a resistor RS2, a resistor RS3, a resistor R4, a resistor R33, a resistor R34, a capacitor C3 and a capacitor C4; the drain terminal of the APFC driver chip IC1 is used as the first terminal of the APFC unit, the VCC terminal of the APFC driver chip IC1 is used as the power terminal of the APFC unit, and one end of the resistor R1 is used as the second terminal of the APFC unit;

[0029] The other end of the resistor R1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is electrically connected to one end of the resistor R3, the other end of the resistor R3, one end of the resistor R4, one end of the resistor R33, and one end of the resistor R34 are all electrically connected to one end of the capacitor C3, the other end of the resistor R34 is electrically connected to the detection end of the APFC driver chip IC1, the other end of the resistor R4, the other end of the resistor R33, and the other end of the capacitor C3 are all grounded, one end of the resistor RS1, one end of the resistor RS2, and one end of the resistor RS3 are all electrically connected to the current sampling end of the APFC driver chip IC1, the VCC end of the APFC driver chip IC1 is electrically connected to one end of the capacitor C4, and the GND end of the APFC driver chip IC1, the other end of the capacitor C4, the other end of the resistor RS1, the other end of the resistor RS2, and the other end of the resistor RS3 are all grounded.

[0030] The technical solution provided by the present invention may include the following beneficial effects: the main circuit of the LED driving power supply is provided with a rectifier filter unit and a flyback isolation constant current unit, so the voltage fluctuation of the mains power, that is, the input voltage Uac, can be obtained by electrically connecting the input end of the low-voltage protection unit to the differential and common-mode interference filtering ends of the rectifier filter unit; then the control end and the power reduction end of the low-voltage protection unit are electrically connected to the control end and the power reduction end of the flyback isolation constant current unit respectively, and the low-voltage protection unit compares the normal working voltage U1 and the shutdown threshold U2 preset by the flyback isolation constant current unit according to the voltage fluctuation of the mains power, thereby controlling the flyback isolation constant current unit to realize that the LED driving power supply reduces power when the input voltage Uac is lower than the normal working voltage U1, shuts down when the power reduction operation reaches the input voltage Uac lower than the shutdown threshold U2, and restarts after recovering to be greater than or equal to the shutdown threshold U2. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The schematic diagram of an LED driving power supply with low voltage protection and adaptability to voltage fluctuations according to one embodiment of the present invention.

[0032] Figure 2 Yes Figure 1 The circuit diagram of the rectifier and filter unit and the APFC unit is shown.

[0033] Figure 3 Yes Figure 1 The circuit diagram of the low voltage protection unit is shown.

[0034] Figure 4 Yes Figure 1 The circuit of the flyback isolation constant current unit is shown Figure 1 .

[0035] Figure 5 Yes Figure 1 The circuit of the flyback isolation constant current unit is shown Figure 2 .

[0036] Among them: LED drive power main circuit 5, low voltage protection unit 3, rectifier filter unit 1, flyback isolation constant current unit 2, APFC unit 4, diode D6, diode D10, capacitor CB3, power reduction control circuit 31, switch control circuit 32, voltage regulator ZD1, voltage regulator ZD2, conduction module 311, resistor R24, resistor R36, resistor R35, capacitor C12, diode D11, resistor R25, resistor R37, resistor R38, resistor R39, resistor R40, capacitor C14, LED drive chip IC2, capacitor C15, capacitor C8, resistor R17, diode D8, resistor R16, resistor R31, resistor R32, capacitor C10, APFC drive chip IC1, resistor R1, resistor R2, resistor R3, resistor RS1, resistor RS2, resistor RS3, resistor R4, resistor R33, resistor R34, capacitor C3, capacitor C4. DETAILED DESCRIPTION

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0038] In the description of the embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0039] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0040] Combine the following Figures 1 to 5 , describes an LED driving power supply with low voltage protection capable of adapting to voltage fluctuations in an embodiment of the present invention.

[0041] A low-voltage protection LED driving power supply capable of adapting to voltage fluctuations, comprising an LED driving power supply main circuit 5 and a low-voltage protection unit 3, wherein the LED driving power supply main circuit 5 is provided with a rectifier filter unit 1 and a flyback isolation constant current unit 2; the input end of the low-voltage protection unit 3 is electrically connected to the differential and common mode interference filtering end of the rectifier filter unit 1, the control end of the low-voltage protection unit 3 is electrically connected to the control end of the flyback isolation constant current unit 2, and the power reduction end of the low-voltage protection unit 3 is electrically connected to the power reduction end of the flyback isolation constant current unit 2;

[0042] The flyback isolation constant current unit 2 is preset with a normal operating voltage U1 and a shutdown threshold U2, and the normal operating voltage U1 is greater than the shutdown threshold U2;

[0043] The low voltage protection unit 3 is used to receive the input voltage Uac from the rectifier and filter unit 1 and compare it with the normal working voltage U1 and the shutdown threshold U2 respectively;

[0044] When the input voltage Uac is lower than the normal working voltage U1 but higher than the shutdown threshold U2, the low voltage protection unit 3 adjusts the working power of the flyback isolation constant current unit 2 in a positive correlation according to the magnitude of the input voltage Uac;

[0045] When the input voltage Uac is lower than the shutdown threshold U2, the low voltage protection unit 3 turns off the flyback isolation constant current unit 2, otherwise it turns on the flyback isolation constant current unit 2.

[0046] The present invention proposes a preferred embodiment of an LED driving power supply with low voltage protection capable of adapting to voltage fluctuations, such as Figures 1 to 5 As shown, the main circuit 5 of the LED driving power supply is provided with a rectifier filter unit 1 and a flyback isolation constant current unit 2, so the voltage fluctuation of the mains, that is, the input voltage Uac, can be obtained by electrically connecting the input end of the low-voltage protection unit 3 to the differential and common-mode interference filtering ends of the rectifier filter unit 1; then the control end and the power reduction end of the low-voltage protection unit 3 are electrically connected to the control end and the power reduction end of the flyback isolation constant current unit 2 respectively, and the low-voltage protection unit 3 compares the normal working voltage U1 and the shutdown threshold U2 preset by the flyback isolation constant current unit 2 according to the voltage fluctuation of the mains, so as to control the flyback isolation constant current unit 2 to realize that the LED driving power supply reduces power when the input voltage Uac is lower than the normal working voltage U1, and shuts down when the power reduction operation is until the input voltage Uac is lower than the shutdown threshold U2, and restarts after recovering to be greater than or equal to the shutdown threshold U2.

[0047] Specifically, the low voltage protection unit 3 receives the input voltage Uac from the rectifier and filter unit 1, and learns the voltage fluctuation of the mains. When the input voltage Uac is lower than the normal operating voltage U1 but higher than the shutdown threshold U2, that is, the mains voltage fluctuates and causes the LED driver power supply to be low-voltage, the low voltage protection unit 3 positively adjusts (lowers) the working power of the flyback isolation constant current unit 2 according to the size of the input voltage Uac, that is, the lower the voltage of the mains, the more the power is reduced, so as to achieve power reduction to maintain the safe operation of the LED driver power supply (protect the internal circuit); when the LED driver power supply reduces power and operates until the input voltage Uac is lower than the shutdown threshold U2, that is, the mains has a serious low voltage, which is a fault state, the low voltage protection unit 3 is required to shut down the flyback isolation constant current unit 2, so that the LED driver power supply is shut down, and automatically resumes startup when the mains voltage recovers to above the shutdown threshold U2.

[0048] It should be noted that the rectifying and filtering unit 1 is as follows Figure 2 As shown, the terminal CON1 is used to connect the AC power. The AC power first passes through the variable resistor VR1 to the EMI filter. The capacitor CX1 in the EMI filter filters out the differential mode interference, and the common mode inductor LF1 filters out the common mode interference. Then, after the rectifier bridge and LC filtering, the voltage is transmitted to the flyback isolation constant current unit 2 for voltage reduction.

[0049] Furthermore, it also includes an APFC unit 4; the first end and the second end of the APFC unit 4 are electrically connected to the front end and the end of the LC filter of the rectifier and filter unit 1 respectively, and the power supply end of the APFC unit 4 is electrically connected to the second power supply end of the flyback isolation constant current unit 2.

[0050] For low-power power supplies, in order to reduce the pollution of harmonics to the AC power grid, relevant standards for limiting current harmonics have been formulated both at home and abroad. In the application field of PFC technology, it is divided into active PFC and passive PFC; the advantages of active PFC are: wide voltage adaptation range, high power factor, mainly used in some mid-to-high-end power supply fields, so its cost is relatively high; while the power factor of passive PFC is not very high, generally only 0.7-0.8, and its efficiency is lower than that of LED driver power supplies with active PFC; therefore, at low power, the loss of active PFC itself will be greater than that of passive PFC, so active PFC is widely used in high-end product fields, while passive PFC is mostly used in some low-end power supply fields due to its simple circuit structure and low cost.

[0051] In view of the above situation, an APFC circuit is proposed. The APFC circuit is a combination of active and passive PFC circuits. It achieves the optimal power factor correction effect by controlling the duty cycle of the switching device. The DC voltage output by the APFC circuit is higher than the input DC voltage. Within the entire input voltage range, the APFC circuit can adjust its control strategy in real time, maintain a very high power factor, and greatly reduce harmonics.

[0052] Therefore, in this embodiment, the LED driving power supply with reduced power operation is preferably provided with an APFC unit 4. Otherwise, when the power is reduced, the power factor will decrease due to the failure to use the APFC unit 4, causing pollution to the power grid, and resulting in problems such as increased line loss and reduced voltage quality.

[0053] Furthermore, the low voltage protection unit 3 includes a diode D6, a diode D10, a capacitor CB3, a power reduction control circuit 31 and a switch control circuit 32; the anode of the diode D6 and the anode of the diode D10 are both used as input terminals of the low voltage protection unit 3, the output terminal of the switch control circuit 32 is used as a control terminal of the low voltage protection unit 3, and the output terminal of the power reduction control circuit 31 is used as a power reduction terminal of the low voltage protection unit 3;

[0054] The cathode of the diode D6, the cathode of the diode D10, the first end of the power reduction control circuit 31, and the first end of the switch control circuit 32 are all electrically connected to one end of the capacitor CB3, and the second end of the power reduction control circuit 31, the second end of the switch control circuit 32, and the other end of the capacitor CB3 are all grounded;

[0055] The power reduction control circuit 31 is used to receive the input voltage Uac and compare it with the normal working voltage U1; when the input voltage Uac is lower than the normal working voltage U1 but higher than the shutdown threshold U2, the power reduction control circuit 31 lowers the working power of the flyback isolation constant current unit 2 in a positive correlation according to the magnitude of the input voltage Uac;

[0056] The switch control circuit 32 is used to receive the input voltage Uac and compare it with the shutdown threshold U2; when the input voltage Uac is lower than the preset shutdown threshold U2, the switch control circuit 32 turns off the flyback isolation constant current unit 2, otherwise it turns on the flyback isolation constant current unit 2.

[0057] In this embodiment, the low voltage protection unit 3 is composed of a diode D6, a diode D10 and a capacitor CB3 to form a rectifier and filter circuit, which rectifies and filters the AC power sinusoidal wave after the differential and common mode interference are filtered out into an envelope wave, that is, the input voltage Uac, and then transmits the input voltage Uac to the power reduction control circuit 31 and the switch control circuit 32 respectively to realize the power reduction function and the power on / off function respectively.

[0058] Furthermore, the power reduction control circuit 31 includes a voltage regulator tube ZD1, a voltage regulator tube ZD2, a conduction module 311, a resistor R24, a resistor R36, a resistor R35 and a capacitor C12; the cathode of the voltage regulator tube ZD1 is used as the first end of the power reduction control circuit 31, one end of the resistor R35 is used as the second end of the power reduction control circuit 31, and the first end of the conduction module 311 is used as the output end of the power reduction control circuit 31;

[0059] The anode of the voltage regulator tube ZD1 is electrically connected to the cathode of the voltage regulator tube ZD2, the anode of the voltage regulator tube ZD2 is electrically connected to one end of the resistor R24, the other end of the resistor R24 ​​is electrically connected to one end of the resistor R36, the other end of the resistor R36, the other end of the resistor R35, and the second end of the conduction module 311 are all electrically connected to one end of the capacitor C12, and one end of the resistor R35 is electrically connected to the other end of the capacitor C12;

[0060] When the voltage at the second end of the conducting module 311 is lower than the voltage at the first end, the conducting module 311 is turned on, and the operating power of the flyback isolation constant current unit 2 is positively correlated to the voltage at the second end of the conducting module 311 .

[0061] In this embodiment, the envelope wave (i.e., the input voltage Uac) first breaks down the two voltage stabilizing diodes ZD1 and ZD2, so that the power reduction control circuit 31 can be turned on, and then the voltage is divided by the resistors R24, R36, and R35, and a low-voltage envelope wave is obtained on the resistor R35, and then filtered by the capacitor C12, so that the voltage at the node of the resistor R35 is stable, so as to control the second terminal voltage of the conduction module 311 (i.e., the voltage at the node of the resistor R35) to be compared with the first terminal voltage. Specifically, there is a formula: (where ZD1 and ZD2 represent the voltage stabilization values ​​of the voltage stabilizing diodes ZD1 and ZD2 respectively) the voltage division of the resistor R35 can be calculated, and at the same time, the first end of the conduction module 311 also receives the normal working voltage U1 from the flyback isolation constant current unit 2. Only when the voltage division of the resistor R35 is lower than the normal working voltage U1 (representing that the voltage of the mains is lower than the normal working voltage U1 of the LED driving power supply), the conduction module 311 is turned on, and the flyback isolation constant current unit 2 is affected by the voltage division of the resistor R35, and the working voltage is pulled down by the voltage division of the resistor R35, thereby positively correlated to reduce the working power; otherwise, in other cases, the conduction module 311 is not turned on, and the flyback isolation constant current unit 2 is not affected by the voltage division of the resistor R35, and still maintains the normal working voltage U1.

[0062] Further, the conduction module 311 is a diode D11 , an anode of the diode D11 is used as a first end of the conduction module 311 , and a cathode of the diode D11 is used as a second end of the conduction module 311 .

[0063] In this embodiment, in order to realize the function that the conduction module 311 conducts only when the second terminal voltage is lower than the first terminal voltage, the conduction module 311 is preferably a diode D11, which can be realized by utilizing its unidirectional conductivity.

[0064] Further, the switch control circuit 32 includes a resistor R25, a resistor R37, a resistor R38, a resistor R39, a resistor R40 and a capacitor C14; one end of the resistor R25 is used as a first end of the switch control circuit 32, one end of the resistor R40 is used as an output end of the switch control circuit 32, and the other end of the resistor R40 is used as a second end of the switch control circuit 32;

[0065] The other end of resistor R25 is electrically connected to one end of resistor R37, the other end of resistor R37 and one end of capacitor C14 are electrically connected to one end of resistor R38, the other end of resistor R38 and one end of resistor R39 are electrically connected to one end of resistor R40, and the other end of capacitor C14 and the other end of resistor R39 are electrically connected to the other end of resistor R40.

[0066] In this embodiment, the envelope wave (i.e., the input voltage Uac) is divided by resistors R25, R37, R38, R39, and R40, filtered by capacitor C14, and a low-voltage envelope wave is obtained on resistor R39, which is then compared with the shutdown threshold U2. The voltage division of the resistor R39 can be calculated. When the voltage division of the flyback isolation constant current unit 2 receiving the resistor R39 is lower than its own preset shutdown threshold U2, the flyback isolation constant current unit 2 performs severe low voltage fault protection, that is, shuts down; until the input voltage Uac rises again, wait for the flyback isolation constant current unit 2 to receive the voltage division of the resistor R39 to be greater than or equal to its own preset shutdown threshold U2, and then restart work.

[0067] Further, the flyback isolation constant current unit 2 includes an LED driver chip IC2, a capacitor C15, a capacitor C8, a resistor R17, a diode D8, a resistor R16, a resistor R31, a resistor R32 and a capacitor C10; one end of the resistor R17 is used as a second power supply end of the flyback isolation constant current unit 2, one end of the capacitor C15 is used as a control end of the flyback isolation constant current unit 2, and one end of the capacitor C8 is used as a power reduction end of the flyback isolation constant current unit 2;

[0068] The other end of the resistor R17 is electrically connected to the cathode of the diode D8, the anode of the diode D8 is electrically connected to one end of the resistor R16, the other end of the resistor R16, one end of the resistor R31, one end of the resistor R32, and one end of the capacitor C10 are all electrically connected to the detection end of the LED driver chip IC2, and the other end of the resistor R31, the other end of the resistor R32, and the other end of the capacitor C10 are all grounded;

[0069] One end of the capacitor C15 is electrically connected to the chip control end of the LED driver chip IC2, and the other end of the capacitor C15 is grounded;

[0070] One end of the capacitor C8 is electrically connected to the analog dimming end of the LED driver chip IC2, and the other end of the capacitor C8 is grounded.

[0071] In this embodiment, the flyback isolation constant current unit 2 is as follows: Figure 4 and 5 As shown, a flyback isolated constant current circuit is built with LED driver chip IC2 as the core to receive the voltage from the rectifier filter unit 1, and the transformer and feedback loop are used to step down the voltage and maintain a constant current output (connect the device from the terminal CON2 output) to ensure the efficiency and output stability of the LED driver power supply. Among them, the analog dimming end and chip control end of the LED driver chip IC2 in the flyback isolation constant current unit 2 need to be electrically connected to the low-voltage protection unit 3 to achieve power reduction and switch control of the flyback isolation constant current unit 2. The detection end of the LED driver chip IC2 also needs to be electrically connected to the APFC unit 4 to achieve power supply detection; the LED driver chip IC2 can use, for example, BP3179F, which is an isolated low-PF dimmable LED driver controller suitable for flyback circuits, supports PWM and analog dimming signals, and simulates dimming throughout the process, which can achieve high-precision, flicker-free lighting. Its DIM end is used as the analog dimming end, and CT The RL terminal is used as the chip control terminal, and the FB terminal is used as the detection terminal. When it is working normally, the analog dimming terminal voltage is about 1.8V, which is the normal working voltage U1. When Uac (i.e. the voltage division of resistor R35) is lower than U1, the diode D11 is forward-conducted, and the analog dimming terminal voltage is pulled down by the voltage division of resistor R35, so that the analog dimming terminal can be pulled down to 0.1-1.75V, which can control the output current 1%-100%, and realize positive correlation power reduction. The chip control terminal is used for detection. It is only powered on when the voltage division of resistor R39 is greater than about 350mV, otherwise it is powered off, so 350mV is the shutdown threshold U2. It should be noted that when the LED driver chip IC2 uses different chips, U1 and U2 will also change.

[0072] Further, the APFC unit 4 includes an APFC driver chip IC1, a resistor R1, a resistor R2, a resistor R3, a resistor RS1, a resistor RS2, a resistor RS3, a resistor R4, a resistor R33, a resistor R34, a capacitor C3 and a capacitor C4; the drain terminal of the APFC driver chip IC1 is used as the first terminal of the APFC unit 4, the VCC terminal of the APFC driver chip IC1 is used as the power supply terminal of the APFC unit 4, and one end of the resistor R1 is used as the second terminal of the APFC unit 4;

[0073] The other end of the resistor R1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is electrically connected to one end of the resistor R3, the other end of the resistor R3, one end of the resistor R4, one end of the resistor R33, and one end of the resistor R34 are all electrically connected to one end of the capacitor C3, the other end of the resistor R34 is electrically connected to the detection end of the APFC driver chip IC1, the other end of the resistor R4, the other end of the resistor R33, and the other end of the capacitor C3 are all grounded, one end of the resistor RS1, one end of the resistor RS2, and one end of the resistor RS3 are all electrically connected to the current sampling end of the APFC driver chip IC1, the VCC end of the APFC driver chip IC1 is electrically connected to one end of the capacitor C4, and the GND end of the APFC driver chip IC1, the other end of the capacitor C4, the other end of the resistor RS1, the other end of the resistor RS2, and the other end of the resistor RS3 are all grounded.

[0074] In this embodiment, Figure 2 As shown, the APFC unit 4 is preferably composed of an APFC driver chip IC1, a resistor R1, a resistor R2, a resistor R3, a resistor RS1, a resistor RS2, a resistor RS3, a resistor R4, a resistor R33, a resistor R34, a capacitor C3 and a capacitor C4 to form an APFC circuit; wherein the APFC driver chip can be a BP2306CJ chip, whose FB terminal serves as a detection terminal, its CS terminal serves as a current sampling terminal, and its DRAIN terminal serves as a drain terminal.

[0075] Other structures and operations of a low-voltage protection LED driving power supply capable of adapting to voltage fluctuations according to an embodiment of the present invention are known to those skilled in the art and will not be described in detail here.

[0076] In the description of this specification, the description with reference to the terms "embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0077] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A low voltage protection LED driver power supply capable of adapting to voltage fluctuations, characterized in that: It comprises an LED driving power supply main circuit and a low voltage protection unit, wherein the LED driving power supply main circuit is provided with a rectifier filter unit and a flyback isolation constant current unit; the input end of the low voltage protection unit is electrically connected to the differential and common mode interference filtering end of the rectifier filter unit, the control end of the low voltage protection unit is electrically connected to the control end of the flyback isolation constant current unit, and the power reduction end of the low voltage protection unit is electrically connected to the power reduction end of the flyback isolation constant current unit; The flyback isolation constant current unit is preset with a normal operating voltage U1 and a shutdown threshold U2, and the normal operating voltage U1 is greater than the shutdown threshold U2; The low voltage protection unit is used to receive the input voltage Uac from the rectifier and filter unit and compare it with the normal working voltage U1 and the shutdown threshold U2 respectively; When the input voltage Uac is lower than the normal working voltage U1 but higher than the shutdown threshold U2, the low voltage protection unit adjusts the working power of the flyback isolation constant current unit in a positive correlation according to the magnitude of the input voltage Uac; When the input voltage Uac is lower than the shutdown threshold U2, the low voltage protection unit turns off the flyback isolation constant current unit, otherwise the flyback isolation constant current unit is turned on; The low voltage protection unit includes a diode D6, a diode D10, a capacitor CB3, a power reduction control circuit and a switch control circuit; the anode of the diode D6 and the anode of the diode D10 are both used as the input end of the low voltage protection unit, the output end of the switch control circuit is used as the control end of the low voltage protection unit, and the output end of the power reduction control circuit is used as the power reduction end of the low voltage protection unit; The cathode of the diode D6, the cathode of the diode D10, the first end of the power reduction control circuit, and the first end of the switch control circuit are all electrically connected to one end of the capacitor CB3, and the second end of the power reduction control circuit, the second end of the switch control circuit, and the other end of the capacitor CB3 are all grounded; The power reduction control circuit is used to receive the input voltage Uac and compare it with the normal working voltage U1; when the input voltage Uac is lower than the normal working voltage U1 but higher than the shutdown threshold U2, the power reduction control circuit lowers the working power of the flyback isolation constant current unit in a positive correlation according to the magnitude of the input voltage Uac; The switch control circuit is used to receive the input voltage Uac and compare it with the shutdown threshold U2; when the input voltage Uac is lower than the shutdown threshold U2, the switch control circuit turns off the flyback isolation constant current unit, otherwise it turns on the flyback isolation constant current unit.

2. The LED driving power supply with low voltage protection and adaptability to voltage fluctuation according to claim 1, characterized in that: It also includes an APFC unit; the first end and the second end of the APFC unit are electrically connected to the front end and the end of the LC filter of the rectifier and filter unit respectively, and the power supply end of the APFC unit is electrically connected to the second power supply end of the flyback isolation constant current unit.

3. The LED driving power supply with low voltage protection and adaptability to voltage fluctuation according to claim 1, characterized in that: The power reduction control circuit includes a voltage regulator tube ZD1, a voltage regulator tube ZD2, a conduction module, a resistor R24, a resistor R36, a resistor R35 and a capacitor C12; the cathode of the voltage regulator tube ZD1 is used as the first end of the power reduction control circuit, one end of the resistor R35 is used as the second end of the power reduction control circuit, and the first end of the conduction module is used as the output end of the power reduction control circuit; The anode of the voltage regulator tube ZD1 is electrically connected to the cathode of the voltage regulator tube ZD2, the anode of the voltage regulator tube ZD2 is electrically connected to one end of the resistor R24, the other end of the resistor R24 ​​is electrically connected to one end of the resistor R36, the other end of the resistor R36, the other end of the resistor R35, and the second end of the conduction module are all electrically connected to one end of the capacitor C12, and one end of the resistor R35 is electrically connected to the other end of the capacitor C12; When the voltage at the second end of the conduction module is lower than the voltage at the first end, the conduction module is turned on, and the operating power of the flyback isolation constant current unit is adjusted in a positive correlation according to the magnitude of the voltage at the second end of the conduction module.

4. The LED driving power supply with low voltage protection and adaptability to voltage fluctuation according to claim 3, characterized in that: The conduction module is a diode D11, an anode of the diode D11 is used as a first end of the conduction module, and a cathode of the diode D11 is used as a second end of the conduction module.

5. The LED driving power supply with low voltage protection and adaptability to voltage fluctuation according to claim 1, characterized in that: The switch control circuit includes a resistor R25, a resistor R37, a resistor R38, a resistor R39, a resistor R40 and a capacitor C14; one end of the resistor R25 is used as a first end of the switch control circuit, one end of the resistor R40 is used as an output end of the switch control circuit, and the other end of the resistor R40 is used as a second end of the switch control circuit; The other end of the resistor R25 is electrically connected to one end of the resistor R37, the other end of the resistor R37 and one end of the capacitor C14 are electrically connected to one end of the resistor R38, the other end of the resistor R38 and one end of the resistor R39 are electrically connected to one end of the resistor R40, and the other end of the capacitor C14 and the other end of the resistor R39 are electrically connected to the other end of the resistor R40.

6. The LED driving power supply with low voltage protection and adaptability to voltage fluctuation according to claim 2, characterized in that: The flyback isolation constant current unit includes an LED driver chip IC2, a capacitor C15, a capacitor C8, a resistor R17, a diode D8, a resistor R16, a resistor R31, a resistor R32 and a capacitor C10; one end of the resistor R17 is used as a second power supply end of the flyback isolation constant current unit, one end of the capacitor C15 is used as a control end of the flyback isolation constant current unit, and one end of the capacitor C8 is used as a power reduction end of the flyback isolation constant current unit; The other end of the resistor R17 is electrically connected to the cathode of the diode D8, the anode of the diode D8 is electrically connected to one end of the resistor R16, the other end of the resistor R16, one end of the resistor R31, one end of the resistor R32, and one end of the capacitor C10 are all electrically connected to the detection end of the LED driver chip IC2, and the other end of the resistor R31, the other end of the resistor R32, and the other end of the capacitor C10 are all grounded; One end of the capacitor C15 is electrically connected to the chip control end of the LED driver chip IC2, and the other end of the capacitor C15 is grounded; One end of the capacitor C8 is electrically connected to the analog dimming end of the LED driver chip IC2, and the other end of the capacitor C8 is grounded.

7. The LED driving power supply with low voltage protection and adaptability to voltage fluctuation according to claim 2, characterized in that: The APFC unit includes an APFC driver chip IC1, a resistor R1, a resistor R2, a resistor R3, a resistor RS1, a resistor RS2, a resistor RS3, a resistor R4, a resistor R33, a resistor R34, a capacitor C3 and a capacitor C4; the drain terminal of the APFC driver chip IC1 is used as the first terminal of the APFC unit, the VCC terminal of the APFC driver chip IC1 is used as the power terminal of the APFC unit, and one end of the resistor R1 is used as the second terminal of the APFC unit; The other end of the resistor R1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is electrically connected to one end of the resistor R3, the other end of the resistor R3, one end of the resistor R4, one end of the resistor R33, and one end of the resistor R34 are all electrically connected to one end of the capacitor C3, the other end of the resistor R34 is electrically connected to the detection end of the APFC driver chip IC1, the other end of the resistor R4, the other end of the resistor R33, and the other end of the capacitor C3 are all grounded, one end of the resistor RS1, one end of the resistor RS2, and one end of the resistor RS3 are all electrically connected to the current sampling end of the APFC driver chip IC1, the VCC end of the APFC driver chip IC1 is electrically connected to one end of the capacitor C4, and the GND end of the APFC driver chip IC1, the other end of the capacitor C4, the other end of the resistor RS1, the other end of the resistor RS2, and the other end of the resistor RS3 are all grounded.

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