Linear constant current driving circuit and LED driving circuit thereof

Abstract

The invention provides a linear constant-current drive circuit and an LED drive circuit thereof, and the LED drive circuit comprises six groups of LED lamps; nine switch units; the switch unit comprises a comparator and a transistor; a first power MOS tube Q0 and a second power MOS tube QA; the grid electrode of the third power MOS tube QB is connected with the drain electrode of the transistor of the seventh switch unit, and the source electrode of the third power MOS tube QB is connected with the other end of the LED 5 through a diode D5. According to the invention, nine switch comparison power supplies and six groups of LED lamps with different voltage drops are adopted, and a multi-channel working mode of the LED lamps is realized through the first power tube Q0, the second power tube QA and the third power tube QB, so that relatively high driving efficiency is realized, and a very wide voltage range can be adapted.

Description

Technical Field

[0001] This invention relates to the field of LED technology, and more specifically, to a linear constant current driving circuit and its LED driving circuit. Background Technology

[0002] Currently, mainstream LED drivers can be divided into switching power supply drivers and linear constant current drivers. Among them, the linear constant current driver solution is becoming increasingly popular in LED lighting applications due to its advantages such as simple application, easy processing, low cost, and no EMC electromagnetic interference. However, as the market for finished LED lighting products expands, finished LED lighting products need to be able to sell to different markets worldwide to reduce product model requirements, lead times, and warehousing pressure.

[0003] refer to Figure 1 To adapt to the linear constant current drive and be compatible with a wide range of grid voltages, existing technologies design LED light strings as multiple segments that are turned on sequentially to change the series-parallel mode.

[0004] Its conduction principle is that when the input voltage is low, such as AC 110V, LED1 and LED2 form a two-stage conduction; Q1 switches LED3 and LED4 to conduct together in parallel. When the input voltage is high, such as AC 220V, LED1~LED4 are connected in series and conduct in a four-stage application.

[0005] However, its disadvantage is that the output LED voltage cannot be set too high, because if the LED voltage is set too high, the brightness of the LED will vary greatly when the input voltage is low. However, although setting the LED voltage to a lower value can accommodate a wider range of AC input voltage, the loss caused by the voltage drop between the input voltage and the lamp voltage will also increase, resulting in lower overall efficiency of the LED driver, affecting the overall lighting effect and causing higher heat loss.

[0006] refer to Figure 2 For example, using an existing circuit design compatible with 120 / 230V input, the LED voltage would be designed to be LED1+LED2=135V / LED1+LED2+LED3+LED4=270V. However, with an input voltage of 100V, the voltage after the rectifier bridge, DCMAX=141V, and the LED voltage is already 135V. According to the principle of linear constant current drive, under conditions where the AC input voltage is low, the conduction time of the second LED segment is severely insufficient. This results in the second segment of the LED string (LED2 & LED4) in the schematic circuit diagram being either not lit or only dimly lit, significantly impacting the overall lighting effect.

[0007] The existing linear constant current drive scheme has the following problems: First, the AC input grid voltage adaptation range is not wide enough, the LED power is not constant, and the LED light effect is unstable and fluctuates greatly; Second, in order to achieve a better LED light effect, the LED voltage needs to be sacrificed, increasing the voltage drop of the bus after the LED and rectifier bridge, which leads to a decrease in the overall drive efficiency, a reduction in the overall light effect, and additional heat loss. Summary of the Invention

[0008] To address the aforementioned technical problems in related technologies, this invention proposes a linear constant current driving circuit, the circuit comprising: nine switching units; each switching unit includes a comparator and a transistor;

[0009] The comparators of the first to ninth switching units are used to receive voltage divider signals, and different preset voltages are input to the other ends of the comparators of the first to ninth switching units.

[0010] The drain of the transistor in the first switching unit provides the first port;

[0011] The drain of the transistor in the second switching unit provides a second port;

[0012] The second power MOSFET QA has its source connected to a fourth port via diode D2; the drain of the second power MOSFET QA is connected to the second port; and the gate of the second power MOSFET QA is connected to the drain of the transistor in the third switching unit.

[0013] The drain of the transistor in the fourth switching unit provides a third port;

[0014] The drain of the transistor in the fifth switching unit provides the fifth port;

[0015] The drain of the transistor in the sixth switching unit provides the sixth port;

[0016] The drain of the transistor in the eighth switching unit provides the seventh port;

[0017] The third power MOSFET QB has its gate connected to the drain of the transistor in the seventh switching unit, its source provided with an eighth port through diode D5, and its drain connected to the sixth port.

[0018] The drain of the transistor in the ninth switching unit provides the ninth port;

[0019] The sources of the transistors in the first to ninth switching units are all grounded.

[0020] Specifically, the linear constant current drive circuit also includes a voltage divider circuit.

[0021] Specifically, the transistors of the second, fourth, fifth, sixth, eighth, and ninth switching units are grounded through a resistor.

[0022] Specifically, the preset voltages of the comparators in the first to fifth switching units are different; the preset voltages of the comparators in the eighth to ninth switching units are the same as the preset voltages of the comparators in the second to fifth switching units.

[0023] Secondly, another embodiment of the present invention provides an LED driving circuit, the circuit comprising: six groups of LED lights; nine switching units; each switching unit comprising a comparator and a transistor;

[0024] The first power MOSFET Q0 has its drain connected to the rectified DC voltage DCBUS, its source connected to the other end of the third LED, and its gate connected to the drain of the transistor in the first switching unit. The six LEDs are connected in series. One end of the first LED LED1 is connected to the rectified DC voltage DCBUS, and the other end is connected to the second LED LED2.

[0025] The voltage divider voltage VBS is input to the comparators of the first to ninth switching units, and different preset voltages are input to the other end of the comparators of the first to ninth switching units.

[0026] The source of the second power MOSFET QA is connected to the other end of LED2 through diode D2; the drain of the second power MOSFET QA is connected to LED1; and the gate of the second power MOSFET QA is connected to the drain of the transistor of the third switching unit.

[0027] The drain of the transistor in the second switching unit is connected to the other end of LED1; the drain of the transistor in the fourth switching unit is connected to the other end of LED2; the drain of the transistor in the fifth switching unit is connected to the other end of LED3.

[0028] The third power MOSFET QB has its gate connected to the drain of the transistor in the seventh switching unit, its source connected to the other end of LED5 via diode D5, and its drain connected to the other end of LED4.

[0029] The drain of the transistor in the sixth switching unit is connected to the other end of LED4;

[0030] The drain of the transistor in the eighth switching unit is connected to the other end of LED5;

[0031] The drain of the transistor in the ninth switching unit is connected to the other end of LED6.

[0032] The sources of the transistors in the first to ninth switching units are all grounded.

[0033] Specifically, the LED driving circuit also includes a voltage divider circuit, which includes a first voltage divider resistor VBS1 and a second voltage divider resistor VBS2. One end of the first voltage divider resistor VBS1 is connected to DCBUS and the other end is connected to VBS2. The other end of VBS2 is grounded, and the voltage of the second voltage divider resistor VBS2 is used as the voltage VBS after voltage division.

[0034] Specifically, the transistors of the second, fourth, fifth, sixth, eighth, and ninth switching units are grounded through a resistor.

[0035] Specifically, the preset voltages of the comparators in the first to fifth switching units are different; the preset voltages of the comparators in the eighth to ninth switching units are the same as the preset voltages of the comparators in the second to fifth switching units.

[0036] Specifically, it also includes a rectifier circuit, which is used to rectify alternating current (AC) into direct current (DCBUS).

[0037] Specifically, it also includes: LED2 is connected to a diode D1 at the other end, and the second power MOSFET is connected to the other end of the diode D1 through diode D2; LED3 is connected to a diode D3 at the other end; LED5 is connected to a diode D4 at the other end, and the third power MOSFET is connected to the other end of the diode D4 through diode D5; LED6 is connected to the other end of the diode D4.

[0038] This invention compares the power supply with nine switches and six groups of LEDs with different voltage drops, and realizes the multi-channel operation mode of the LEDs through the first power transistor Q0, the second power transistor QA, and the third power transistor QB, thereby achieving high driving efficiency and being able to adapt to a very wide voltage range. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 It is a linear constant current LED driver circuit based on existing technology;

[0041] Figure 2This is a schematic diagram of a linear constant current driven LED lamp with segmented conduction.

[0042] Figure 3 This is a schematic diagram of an LED driving circuit provided in an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of a linear constant current drive circuit provided in an embodiment of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0045] Example 1

[0046] refer to Figure 3 ,exist Figure 3 In this implementation, LED1, LED2, ... LED6 are listed in sequence. The left side of LED1 is defined as the positive terminal (which is also one end of the LED), and the right side is defined as the negative terminal (which is also the other end of the LED). In this embodiment, "one end" and "the other end" are used to describe the positive and negative polarity relationship of circuit elements such as LEDs and diodes in the circuit.

[0047] This embodiment provides an LED driving circuit, which includes: six groups of LED lights; nine switching units; each switching unit includes a comparator and a transistor;

[0048] The first power MOSFET Q0 has its drain connected to the rectified DC voltage DCBUS, its source connected to the other end of the third LED, and its gate connected to the drain of the transistor in the first switching unit. The six LEDs are connected in series. One end of the first LED LED1 is connected to the rectified DC voltage DCBUS, and the other end is connected to the second LED LED2.

[0049] In another embodiment, a diode D3 is connected between the third LED and the fourth LED. In this case, the source of the first power MOSFET is connected to the other end of the diode D3, or the source of the first power MOSFET is connected to one end of the fourth LED.

[0050] The voltage divider voltage VBS is input to the comparators of the first to ninth switching units, and different preset voltages are input to the other ends of the comparators of the first to ninth switching units. The voltage divider voltage VBS is obtained by dividing the rectified DC voltage DCBUS.

[0051] The second power MOSFET QA has its source connected to the other end of LED2; its drain connected to LED1; and its gate connected to the drain of the transistor in the third switching unit.

[0052] In another embodiment, the source of the second power MOSFET QA can also be connected to one end of LED3. That is, regarding the connection relationship between the source of the second power MOSFET QA and LED3 and LED4, those skilled in the art can refer to the appendix... Figure 3 As can be seen from the appendix, this embodiment only describes one type of connection relationship; other connection relationships are not described in detail. Similarly, for similar circuit connection relationships in this embodiment, this embodiment also only describes one type of connection relationship. For other connection relationships, those skilled in the art can refer to the appendix. Figure 3 It was obtained from the middle.

[0053] In another embodiment, a second power MOSFET QA is used, the source of which is connected to the other end of LED2 via diode D2.

[0054] The drain of the transistor in the second switching unit is connected to the other end of LED1; the drain of the transistor in the fourth switching unit is connected to the other end of LED2; the drain of the transistor in the fifth switching unit is connected to the other end of LED3.

[0055] The third power MOSFET QB has its gate connected to the drain of the transistor in the seventh switching unit, its source connected to the other end of LED5, and its drain connected to the other end of LED4.

[0056] In another embodiment, the source of the third power MOSFET QB is connected to the other end of LED5 via diode D5.

[0057] The drain of the transistor in the sixth switching unit is connected to the other end of LED4;

[0058] The drain of the transistor in the eighth switching unit is connected to the other end of LED5;

[0059] The drain of the transistor in the ninth switching unit is connected to the other end of LED6.

[0060] The sources of the transistors in the first to ninth switching units are all grounded;

[0061] For specific references Figure 3In this embodiment, the six groups of LEDs are LED1, LED2, ..., LED6. The six groups of LEDs are connected in series, with one end of LED1 connected to the rectified DCBUS voltage and the other end connected to LED2; the other end of LED2 is connected to LED3, the other end of LED3 is connected to LED4, the other end of LED4 is connected to LED5, and the other end of LED5 is connected to LED6; the other end of LED6 is connected to the drain of the transistor in the ninth switching unit.

[0062] The voltage drop across LEDs is 72V for LED1, 54V for LED2, 27V for LED3, 72V for LED4, 54V for LED5, and 27V for LED6. In this embodiment, the voltage drops of the LEDs represent different voltage segments. These different voltage drops can be achieved by connecting LEDs in series with different numbers of LEDs. For example, LED1 can be connected in series with 24 LEDs, each with a voltage of 3V. In another embodiment, LED1 can be connected in series with 4 LEDs, where the voltage of the LEDs used is 18V. The same applies to LEDs 2-6; their voltage segments can be set to the recommended values ​​in this embodiment, i.e., LED2 has a voltage drop of 54V, LED3 has a voltage drop of 27V, LED4 has a voltage drop of 72V, LED5 has a voltage drop of 54V, and LED6 has a voltage drop of 27V.

[0063] In this embodiment, the voltage drops of the first to third LEDs are different, the voltage drop of the fourth LED is the same as that of the first LED, the voltage drop of the fifth LED is the same as that of the second LED, and the voltage drop of the sixth LED is the same as that of the third LED.

[0064] This embodiment also includes nine switching units, each containing a comparator and a transistor, with the transistor's gate connected to the comparator's output stage. The non-inverting phase of each comparator receives a divided voltage VBS, and the negative phase of each comparator is connected to a preset voltage. The specific preset voltage is set according to actual needs. In this embodiment, the other end of the comparator in the first switching unit receives 2V, the other end of the comparator in the second switching unit receives 1V, the other end of the comparator in the third switching unit receives 1.1V, the other end of the comparator in the fourth switching unit receives 1.2V, the other end of the comparator in the fifth switching unit receives 1.3V, the other end of the comparator in the sixth switching unit receives 1V, the other end of the comparator in the seventh switching unit receives 1.1V, the other end of the comparator in the eighth switching unit receives 1.2V, and the other end of the comparator in the ninth switching unit receives 1.3V. The preset voltages of the comparators in the eighth to ninth switching units in this embodiment are the same as the preset voltages of the comparators in the second to fifth switching units, respectively.

[0065] In another embodiment, when the input AC voltage is high, in this example, high voltage refers to AC greater than or equal to 120V, and the corresponding low voltage is AC less than 120V (see appendix). Figure 3 In this example, VT1 represents low voltage and VT2 represents high voltage. The preset voltage of the comparator for the fourth switch is 2.5V, the preset voltage of the comparator for the sixth switch is 2.7V, the preset voltage of the comparator for the eighth switch is 2.9V, and the preset voltage of the comparator for the ninth switch is 3.1V. Specifically, the preset voltage allocation can be determined based on the detection of the input AC voltage, which will not be elaborated further in this embodiment.

[0066] Specifically, this embodiment also includes a voltage divider circuit, which includes a first voltage divider resistor VBS1 and a second voltage divider resistor VBS2. One end of the first voltage divider resistor VBS1 is connected to DCBUS and the other end is connected to VBS2. The other end of VBS2 is grounded, and the voltage of the second voltage divider resistor VBS2 is used as the voltage VBS after voltage division.

[0067] Specifically, this embodiment also includes a rectifier circuit, which is used to rectify alternating current (AC) into direct current (DCBUS). The rectifier circuit can be a rectifier bridge circuit. Rectifier bridge circuits are common circuits in this field and will not be described in detail in this embodiment.

[0068] Furthermore, the other end of LED2 is connected to a diode D1, and the second power MOSFET is connected to the other end of the diode D1 through a diode D2.

[0069] Furthermore, the other end of LED3 is connected to a diode D3. Specifically, the source of the first power MOSFET is connected to the other end of D3.

[0070] Furthermore, the other end of LED5 is connected to a diode D4, and the third power MOSFET is connected to the other end of diode D4 through diode D5. LED6 is connected to the other end of diode D4.

[0071] In this embodiment, diodes D1, D2, D3, D4, and D5 utilize their unidirectional conduction characteristics. Under different VBUS voltages, LED segments 1 through 6 are cyclically turned on (see the following section for the LED conduction sequence under different voltages). The LEDs can operate according to a specific conduction logic, ensuring that associated LED segments do not interfere with each other.

[0072] Furthermore, the transistors of the first to ninth switching units are all grounded through a resistor.

[0073] In another embodiment, the transistors of the second, fourth, fifth, sixth, eighth, and ninth switching units are grounded through a resistor.

[0074] The working process of this embodiment is as follows: For example, when the AC input voltage is low (120V), the voltage of the bus voltage divider signal VBS after the rectifier bridge is <2V. A low signal is detected, the SPC1 switch is turned off, and the DCBUS provides a power supply path to the LED string LEDs 4-6 via MOS Q0. At this time, LEDs 1, 2, 3 and 4, 5, and 6 are connected in parallel. MOS Q1, Q2, Q3 and Q4, Q5, Q6 respectively form a three-channel constant current LED operation. The working process is as follows:

[0075] First stage LED1Q1 conduction voltage: 72V

[0076] The voltage of LED1QAD2LED3Q3 in the second stage is 72V + 27V = 99V.

[0077] The voltage of LED1, LED2, and Q2 in the third stage is 72V + 54V = 126V.

[0078] The fourth stage conducts LED1, LED2, D1, LED3, and Q3. The lamp voltage is 72V + 54V + 27V = 153V.

[0079] At 120V AC, the MOSFET is turned on, and at this time, LED1, LED2, D1, LED3, and Q3 are turned on. The maximum AC value is 169V (120VAC*1.414), and the maximum lamp voltage is 153V. The voltage drop across the MOSFET is low, and the chip consumes less power.

[0080] Similarly: When the input voltage is low, at 100VAC, MOSFET Q2 is turned on; the maximum input voltage is 141V, which corresponds to LED1 + LED2 = 126V, and the voltage drop across the MOSFET is 141 - 126V = 15V. Therefore, the power loss is also relatively small.

[0081] When the input voltage is 90V AC, the voltage of the bus voltage divider signal VBS after the rectifier bridge is 1.1V, indicating a low signal, and the SPC1 switch is off; the maximum voltage is 127V, corresponding to the lamp voltage of LED1 + LED3 = 99V, and the voltage drop across the MOSFET is 126V - 99V = 27V.

[0082] With an input voltage of 230V AC, the voltage divider signal VBS after the rectifier bridge bus is greater than 2V. The voltage division value of VBS is high, SPC1 is turned on, and MOS Q0 is pulled low to turn off. Q2, Q4, Q5, and Q6 form a four-segment driver, operating as follows: LED1+LED2D1LED3+D3+LED4LED5D4LED6(126V-99V-54V-27V).

[0083] With a 230V AC input voltage, the maximum value is 324V, and the lamp string voltage is 306V. At this time, the lamp voltage utilization rate is extremely high, with a theoretical efficiency of over 90%.

[0084] The LED driver circuit of this embodiment has the following advantages: 1. High efficiency: Under both high and low voltage input of the mains, the linear constant current drive has an efficiency of about 90%, while the efficiency of existing linear constant current drive methods is about 85%; 2. Wide voltage range: Under a 90V AC mains voltage input, the LED lamp can be fully lit at full power without affecting the driving efficiency, losing luminous efficacy, or generating additional heat.

[0085] Example 2

[0086] This embodiment discloses a linear constant current driving circuit, the circuit including: nine switching units; each switching unit includes a comparator and a transistor;

[0087] The comparators of the first to ninth switching units are used to receive voltage divider signals, and different preset voltages are input to the other ends of the comparators of the first to ninth switching units.

[0088] The voltage divider VBS is obtained by dividing the rectified DC voltage DCBUS. The linear constant current drive circuit in this embodiment also includes a preset voltage generation circuit to generate a preset voltage, which is used to supply the comparator of the switching unit. (Reference) Figure 4 In this embodiment, pin 1 VIN of the integrated chip is a power supply pin, used to input working power to support the operation of the integrated chip. For example, the working power can be used to provide power to the preset voltage generation circuit.

[0089] The drain of the transistor in the first switching unit provides a first port. This first port is used to connect to the power transistor Q0, i.e. Figure 4 Pin 16 in the middle.

[0090] The drain of the transistor in the second switching unit provides a second port; the second port is used to provide the drain of the first LED switch, i.e. Figure 4 Pin 2.

[0091] The second power MOSFET QA has its source connected to a fourth port via diode D2. Figure 4 Pin SPC2 in the middle; the drain of the second power MOSFET QA is connected to the second port; the gate of the second power MOSFET QA is connected to the drain of the transistor in the third switching unit;

[0092] The drain of the transistor in the fourth switching unit provides a third port; the third port is used to provide the drain of the second LED switch, i.e. Figure 4 Pin 3.

[0093] The drain of the transistor in the fifth switching unit provides a fifth port; the fifth port is used to provide the drain of the third LED switch, i.e. Figure 4 Pin 4.

[0094] The drain of the transistor in the sixth switching unit provides a sixth port; the sixth port is used to provide the drain of the fourth LED switch, i.e. Figure 4 Pin 5.

[0095] The drain of the transistor in the eighth switching unit provides a seventh port; the seventh port is used to provide the drain of the fifth LED switch, i.e. Figure 4 Pin 6.

[0096] The third power MOSFET QB has its gate connected to the drain of the transistor in the seventh switching unit, and its source is connected to the eighth port via diode D5. Figure 4 SPC3, the drain of the third power MOSFET QB is connected to the sixth port.

[0097] The drain of the transistor in the ninth switching unit provides a ninth port. This ninth port is used to provide the drain for the sixth LED switch, i.e. Figure 4 Pin 7.

[0098] The sources of the transistors in the first to ninth switching units are all grounded;

[0099] For specific references Figure 3 When the linear constant current driving circuit of this embodiment is used for LED driving, it further includes: a first power MOSFET Q0, the drain of the first power MOSFET is connected to the rectified DC voltage DCBUS, the source of the first power MOSFET is connected to the other end of the third LED, and the gate of the first power MOSFET is connected to the drain of the transistor of the first switching unit.

[0100] Six sets of LED lights are connected in series. One end of the first LED light (LED1) is connected to the rectified DC voltage DCBUS, and the other end is connected to the second LED light (LED2).

[0101] The source of the second power MOSFET QA is connected to the other end of LED2 through diode D2; the drain of the second power MOSFET QA is connected to LED1; and the gate of the second power MOSFET QA is connected to the drain of the transistor of the third switching unit.

[0102] In this embodiment, the six groups of LEDs are LED1, LED2, ..., and LED6. The six groups of LEDs are connected in series, with one end of LED1 connected to the rectified DCBUS voltage and the other end connected to LED2; the other end of LED2 is connected to LED3, the other end of LED3 is connected to LED4, the other end of LED4 is connected to LED5, and the other end of LED5 is connected to LED6; the other end of LED6 is connected to the drain of the transistor in the ninth switching unit.

[0103] The voltage drop of LED1 is 72V, that of LED2 is 54V, that of LED3 is 27V, that of LED4 is 72V, that of LED5 is 54V, and that of LED6 is 27V.

[0104] This embodiment also includes nine switching units, each containing a comparator and a transistor, with the transistor's gate connected to the comparator's output stage. The non-inverting phase of each comparator receives a divided voltage VBS, and the negative phase of each comparator is connected to a preset voltage. The specific preset voltage is set according to actual needs. In this embodiment, the other end of the comparator in the first switching unit receives 2V, the other end of the comparator in the second switching unit receives 1V, the other end of the comparator in the third switching unit receives 1.1V, the other end of the comparator in the fourth switching unit receives 1.2V, the other end of the comparator in the fifth switching unit receives 1.3V, the other end of the comparator in the sixth switching unit receives 1V, the other end of the comparator in the seventh switching unit receives 1.1V, the other end of the comparator in the eighth switching unit receives 1.2V, and the other end of the comparator in the ninth switching unit receives 1.3V. The preset voltages of the comparators in the eighth to ninth switching units in this embodiment are the same as the preset voltages of the comparators in the second to fifth switching units, respectively.

[0105] Specifically, this embodiment also includes a voltage divider circuit, which includes a first voltage divider resistor VBS1 and a second voltage divider resistor VBS2. One end of the first voltage divider resistor VBS1 is connected to DCBUS and the other end is connected to VBS2. The other end of VBS2 is grounded, and the voltage of the second voltage divider resistor VBS2 is used as the voltage VBS after voltage division.

[0106] Specifically, this embodiment preferably includes a rectifier circuit, which is used to rectify alternating current (AC) into direct current (DCBUS). The rectifier circuit can be a rectifier bridge circuit. Rectifier bridge circuits are common circuits in this field and will not be described in detail in this embodiment.

[0107] Furthermore, the other end of LED2 is connected to a diode D1, and the second power MOSFET is connected to the other end of the diode D1 through a diode D2.

[0108] Furthermore, a diode D3 is connected to the other end of LED3.

[0109] Furthermore, the other end of LED5 is connected to a diode D4, and the third power MOSFET is connected to the other end of diode D4 through diode D5. LED6 is connected to the other end of diode D4.

[0110] Furthermore, the transistors of the first to ninth switching units are all grounded through a resistor.

[0111] In another embodiment, the transistors of the second, fourth, fifth, sixth, eighth, and ninth switching units are grounded through a resistor.

[0112] The working process of this embodiment is as follows: For example, when the AC input voltage is low at 120V, the voltage divider signal VBS detected by the bus voltage after the rectifier bridge is low, the SPC1 switch is closed, and the DCBUS provides a power supply path to the LED string LEDs 4-6 via MOS Q0. At this time, the LED strings LEDs 1, LED 2, LED 3 and LEDs 4, LED 5, LED 6 are connected in parallel. MOS Q1, Q2, Q3 and Q4, Q5, Q6 respectively form a three-channel constant current operation for the LEDs. The working process is as follows:

[0113] First stage LED1Q1 conduction voltage: 72V

[0114] The voltage of LED1QAD2LED3Q3 in the second stage is 72V + 27V = 99V.

[0115] The voltage of LED1, LED2, and Q2 in the third stage is 72V + 54V = 126V.

[0116] The fourth stage conducts LED1, LED2, D1, LED3, and Q3. The lamp voltage is 72V + 54V + 27V = 153V.

[0117] At 120V AC, the maximum AC value is 169V (120VAC*1.414), and the maximum lamp voltage is 153V. The voltage drop across the MOS is low, and the chip consumes less power.

[0118] Similarly: When the input voltage is low, at 100VAC, the maximum input voltage is 141V, which corresponds to LED1 + LED2 = 126V. The voltage drop across the MOSFET is 141 - 126V = 15V. Therefore, the losses are also relatively small.

[0119] With an input voltage of 90V, the maximum voltage is 127V, corresponding to a lamp voltage of LED1 + LED3 = 99V. The voltage drop across the MOSFET is 126V - 99V = 27V.

[0120] When the input voltage is 230V, the voltage divider value of VBS is high, SPC1 is turned on, and Q0 is turned off. Q2, Q4, Q5, and Q6 form a four-segment driver, and the working process is as follows: LED1+LED2D1LED3+D3+LED4LED5D4LED6(126V-99V-54V-27V).

[0121] With a 230V AC input voltage, the maximum value is 324V, and the lamp string voltage is 306V. At this time, the lamp voltage utilization rate is extremely high, with a theoretical efficiency of over 90%.

[0122] In another embodiment, the linear constant current drive circuit of this application further includes a PWM dimming circuit for performing PWM dimming. The specific PWM dimming circuit is a commonly used circuit in the art, and will not be described in detail in this example. That is, the linear constant current drive circuit of this application also provides pin 13 for setting PWM dimming.

[0123] Furthermore, the linear constant current drive circuit of this embodiment also provides pins 9 and 10 for current setting. Pin 8 provides a mains sampling pin, which is used to receive the voltage after voltage division. Pin 1 is the power supply input pin.

[0124] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A linear constant current drive circuit, the circuit comprising: Nine switching units; each switching unit includes a comparator and a transistor; The comparators of the first to ninth switching units are used to receive voltage divider signals, and different preset voltages are input to the other end of the comparators of the first to ninth switching units. The drain of the transistor in the first switching unit provides the first port; The drain of the transistor in the second switching unit provides a second port; The second power MOSFET QA has a source that provides a fourth port; the drain of the second power MOSFET QA is connected to the second port; and the gate of the second power MOSFET QA is connected to the drain of the transistor in the third switching unit. The drain of the transistor in the fourth switching unit provides a third port; The drain of the transistor in the fifth switching unit provides the fifth port; The drain of the transistor in the sixth switching unit provides the sixth port; The drain of the transistor in the eighth switching unit provides the seventh port; The third power MOSFET QB has its gate connected to the drain of the transistor in the seventh switching unit, its source providing the eighth port, and its drain connected to the sixth port. The drain of the transistor in the ninth switching unit provides the ninth port; The sources of the transistors in the first to ninth switching units are all grounded.

2. The linear constant current drive circuit according to claim 1, wherein the linear constant current drive circuit further includes a voltage divider circuit.

3. In the linear constant current drive circuit according to claim 2, the source of the second power MOSFET QA is provided with a fourth port through diode D2; the source of the third power MOSFET QB is provided with an eighth port through diode D5.

4. In the linear constant current drive circuit according to claim 3, the preset voltages of the comparators of the first to fifth switching units are different; the preset voltages of the comparators of the eighth to ninth switching units are the same as the preset voltages of the comparators of the second to fifth switching units.

5. An LED driving circuit, the circuit comprising: Six sets of LED lights; Nine switching units; each switching unit includes a comparator and a transistor; The first power MOSFET Q0 has its drain connected to the rectified DC voltage DCBUS, its source connected to the other end of the third LED, and its gate connected to the drain of the transistor in the first switching unit. The six LEDs are connected in series. One end of the first LED LED1 is connected to the rectified DC voltage DCBUS, and the other end is connected to the second LED LED2. The voltage divider voltage VBS is input to the comparators of the first to ninth switching units, and different preset voltages are input to the other end of the comparators of the first to ninth switching units. The second power MOSFET QA has its source connected to the other end of LED2; its drain connected to LED1; and its gate connected to the drain of the transistor in the third switching unit. The drain of the transistor in the second switching unit is connected to the other end of LED1; the drain of the transistor in the fourth switching unit is connected to the other end of LED2; the drain of the transistor in the fifth switching unit is connected to the other end of LED3. The third power MOSFET QB has its gate connected to the drain of the transistor in the seventh switching unit, its source connected to the other end of LED5, and its drain connected to the other end of LED4. The drain of the transistor in the sixth switching unit is connected to the other end of LED4; The drain of the transistor in the eighth switching unit is connected to the other end of LED5; The drain of the transistor in the ninth switching unit is connected to the other end of LED6; The sources of the transistors in the first to ninth switching units are all grounded.

6. The LED driving circuit according to claim 5 further includes a voltage divider circuit, the voltage divider circuit including a first voltage divider resistor VBS1 and a second voltage divider resistor VBS2, wherein one end of the first voltage divider resistor VBS1 is connected to DCBUS and the other end is connected to VBS2, the other end of VBS2 is grounded, and the voltage of the second voltage divider resistor VBS2 is used as the voltage VBS after voltage division.

7. In the LED driving circuit according to claim 5, the transistors of the second, fourth, fifth, sixth, eighth, and ninth switching units are grounded through a resistor.

8. In the LED driving circuit according to claim 5, the preset voltages of the comparators of the first to fifth switching units are different; the preset voltages of the comparators of the eighth to ninth switching units are the same as the preset voltages of the comparators of the second to fifth switching units.

9. The LED driving circuit according to claim 5 further includes a rectifier circuit, the rectifier circuit being used to rectify alternating current (AC) into direct current (DC).

10. The LED driving circuit according to claim 5, further comprising: The source of the second power MOSFET QA is connected to the other end of LED2 via diode D2; the source of the third power MOSFET QB is connected to the other end of LED5 via diode D5; the other end of LED2 is connected to diode D1, and the second power MOSFET is connected to the other end of diode D1 via diode D2; the other end of LED3 is connected to diode D3; the other end of LED5 is connected to diode D4, and the third power MOSFET is connected to the other end of diode D4 via diode D5; the LED6 is connected to the other end of diode D4.

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