CN210093619U - A four-channel AC LED driver chip circuit with fine dimming - Google Patents

Abstract

The utility model discloses a four-channel AC LED driving chip circuit with fine dimming, which drives WLED, RLED, GLED and BLED light strings simultaneously with the pulsating voltage after full-wave rectification of the commercial power supply, and a control signal generated by a logic control circuit , The dimming signal generated by the PWM circuit and the protection signal generated by the protection circuit realize the segmented conduction and brightness adjustment of the light string of each color channel. The utility model does not need to perform AC-DC conversion, reduces the volume of the system, reduces the manufacturing cost, and improves the reliability of the system; the utility model performs fine dimming for different color channels through a dimming circuit and PWM signals with different duty ratios Combined to realize the color driving of the design parameters, the spectral distribution can be adjusted at the same time, and the lighting efficiency can be further improved, thereby being applied to various lighting purposes; the utility model can adjust the color shift problem caused by the change of the current value of each color light string; At the same time, the color rendering index of the LED light string can be improved, so that the overall color rendering performance of the system is better.

Description

A four-channel AC LED driver chip circuit with fine dimming

technical field

The utility model relates to the field of driving circuits, in particular to a four-channel AC LED driving chip circuit with fine dimming.

Background technique

In recent years, with the development of science and technology, LED has emerged as the fourth generation of green, energy-saving, power-saving and long-life lighting fixtures. The advantages of LED are gradually replacing incandescent lamps and fluorescent lamps, and are widely used in various lighting fields, and have also been vigorously studied by governments of various countries.

Traditional LED drive circuits mostly use DC current to drive, that is, use an AC-DC converter to process the commercial power and then output a DC voltage, and then drive the LED. However, due to the large energy loss in the conversion process, the efficiency of the LED system is reduced. At the same time, the life of the AC-DC converter is much lower than that of the LED, which seriously affects the reliability of the drive circuit.

With the advancement of technology, the technology of alternating current direct drive LED (AC LED) has been developed and adopted. The technology can be roughly divided into two categories: bridge AC LED technology and AC-driven HV-LED driver chip technology. The bridge AC LED technology uses the unidirectional conduction characteristics of LEDs to arrange the LED lamp beads into a similar rectifier bridge structure and directly connect to the mains to achieve AC lighting; while the AC-driven HV-LED technology uses segmented control and The constant current processing technology enables the LEDs to be lit or extinguished in sections under different input voltages, which improves the efficiency of the system.

However, the advancement of technology, the improvement of the quality of life, and the need for energy saving have made the application scope of color RGB driver more and more extensive, such as lighting, landscape and agriculture. In addition to important parameters such as color temperature and color rendering index of LEDs used in lighting and other fields, the industry also pays more and more attention to the S/P ratio of the spectrum (S: dark light brightness, P: strong light brightness). Studies have shown that bulbs with higher S/P ratios can make full use of the sensitivity of human eye nerve cells to reduce illumination requirements to protect eyes and meet clearer visual effects, while further saving energy. At present, the multi-channel AC direct drive LED scheme adopts the color driving by changing the current of each color light string, but there is a certain color shift problem in the light emission of the LED light string.

Utility model content

The purpose of the utility model is to solve the problems of large volume, high cost, low efficiency and poor color rendering performance of the DC RGB driving circuit in the prior art, and to overcome the defect of the color shift of the multi-channel AC driving LED, and provide a fine dimming The four-channel AC LED driver chip circuit. The utility model has the advantages of high integration, adjustable spectral distribution, better color rendering performance and high efficiency, and has overtemperature and overvoltage protection.

The purpose of the present utility model can be achieved through the following technical solutions:

A four-channel AC LED driver chip circuit with fine dimming, including a rectifier bridge, a voltage divider circuit, a current detection circuit, a logic control circuit, a PWM circuit, a dimming and protection circuit, a channel current generation circuit, a WRGB constant current circuit, and a WLED Light string, RLED light string, GLED light string, BLED light string and protection circuit;

The WLED light string, RLED light string, GLED light string and BLED light string all include multi-level LEDs; wherein, the first-level LED is composed of the first string of LED light strings, and the second-level LED is composed of the first two adjacent strings of LEDs. The third-level LED is composed of the first three strings of LED lights, and so on to form a multi-level LED.

The output end of the rectifier bridge is connected with the input end of the first-stage LED in the WLED light string, the RLED light string, the GLED light string and the BLED light string; it is used for full-wave rectification of the commercial power;

The voltage divider circuit, one end is connected with the rectifier bridge, and the other end is connected with the logic control circuit; it is used to step down the high-voltage pulsating voltage output by the rectifier, and the obtained low-voltage pulsating voltage whose amplitude is less than the chip power supply voltage is supplied to the chip. internal processing;

One end of the current detection circuit is respectively connected with the source of the high-voltage switch tube on the control channel connected with the WLED light string, and the other end is connected with the logic control circuit; it is used to detect the magnitude of the current flowing through the WLED channel, When the detected current reaches the current threshold, a pulse signal is output as a signal for the channel switching of the logic control circuit;

The logic control circuit is connected with the dimming and protection circuit; it is used to generate and control the WLED, RLED, GLED and BLED light strings except the last one when the current detection circuit outputs a pulse signal to act as the logic control circuit in the rising stage of the input voltage. The signal that the switch groups of all levels except the first-level LED are turned off in sequence; in the stage of input voltage drop, the signal to control the switch groups of all levels except the last-level LED on the WLED, RLED, GLED and BLED light strings to be turned on in sequence ;

The PWM circuit is connected with the dimming and protection circuit; it is used to generate the dimming signal of the control channel corresponding to the LEDs at all levels in the WLED, RLED, GLED and BLED light strings;

The dimming and protection circuits are respectively connected with the logic control circuit, the PWM circuit, the protection circuit and the gate of the MOS tube in the switch gating module; it is used for the control signal generated by the logic control circuit and the dimming generated by the PWM circuit. The signal and the protection signal generated by the protection circuit are synthesized, and then the on-off of the switch groups at all levels except the last-level LED on the WLED, RLED, GLED and BLED light strings are controlled to realize the WLED, RLED, GLED and BLED lights. The LEDs at all levels of the string are turned on and off in sequence;

The channel current generation circuit is connected to the source of the MOS tube in the switch gating module; when the respective channels of the RLED, GLED and BLED light strings are turned on, the channel current generation circuit provides current for them;

The WRGB constant current circuit is connected to the output end of the last LED in the WLED light string, the RLED light string, the GLED light string and the BLED light string; when the WLED, RLED, GLED and BLED light strings are all lit, the WRGB The constant current circuit keeps the current on the last stage LED output channel constant;

The protection circuit is used to provide overvoltage protection and overtemperature protection.

The rectifier bridge is a full-wave rectifier bridge, which converts the alternating current of 220V/50Hz into the DC pulsating voltage of 0-311V.

The current detection circuit includes an error amplifier and a resistor R1.

In the current detection circuit, when the high-voltage switch tube of the control channel corresponding to the output end of each LED in the WLED light string is turned on, the current flows through the sampling resistor R1 to generate a voltage drop, and the voltage value is connected to the error amplifier as a feedback signal. The non-inverting terminal, the inverting terminal of the error amplifier is connected to the reference voltage VREF1, and the output terminal of the error amplifier is connected to the logic control circuit.

The PWM circuit includes a comparator.

In the PWM circuit, the sawtooth wave voltage is connected to the inverting input terminal of the comparator, and the external voltages that generate the dimming signal are respectively connected to the non-inverting input terminal of the comparator. The dimming signals of different duty ratios of the corresponding channels of the WLED, RLED, GLED and BLED light strings can be obtained.

The dimming and protection circuit includes an AND gate circuit.

In the dimming and protection circuit, the output signal of the logic control circuit, the output signal of the PWM circuit and the output signal of the protection circuit are respectively connected to the input terminal of the AND gate, and the output signal controls the WLED, RLED, GLED and BLED light strings on the Except for the last level of LED, the rest of the switch groups at all levels.

The channel current generating circuit includes an error amplifier, a MOS transistor and a resistor R2.

In the channel current generation circuit, the error amplifier, a MOS tube connected to the output end of the error amplifier and the resistor R2 form a constant current circuit, which provides bias current for the current mirror formed by other MOS tubes, and then supplies the RLED lamp with a bias current. The output terminals of all levels of LEDs in the string except the last level of LEDs correspond to channels, the output terminals of other levels of LEDs except the last level of LEDs in the GLED light string correspond to the channels, and the rest of the BLED light string except the last level of LEDs The LED output terminals of all levels provide current to the corresponding channel.

The WRGB constant current circuit includes an error amplifier, a MOS tube and a resistor.

Further, the number of error amplifiers, the number of resistors and the number of MOS tubes in the WRGB constant current circuit are the same as the number of types of light strings.

In the WRGB constant current circuit, when the WLED, RLED, GLED and BLED light strings are all lit, the current flows to the sampling resistor through the high-voltage MOS tube, and a voltage drop is generated on the sampling voltage, and the voltage value is used as a feedback signal to connect To the inverting input terminal of the error amplifier, the non-inverting input terminal of the error amplifier is connected to the reference voltage VREF1, and the output terminal of the error amplifier is connected to the gate of the high-voltage MOS tube.

Further, in the present invention, the types and numbers of light strings are not limited to the four types of WLED light strings, RLED light strings, GLED light strings, and BLED light strings.

Compared with the prior art, the utility model has the following beneficial effects:

1. The utility model does not need AC-DC conversion, which reduces the volume of the system, reduces the manufacturing cost, and improves the reliability of the system.

2. The utility model uses PWM signal to adjust the light of each light string, which can improve the color shift problem caused by changing the current of each light string to adjust the light. The overall color rendering performance of the system is better.

3. The utility model can change the spectral distribution by adjusting and controlling the duty ratio of the dimming signal of each color light string under the condition of low light illumination, so as to realize the LED light with high S/P ratio, which can make better use of the human eye. Sensitivity, eye protection and optimized lighting effects to further improve lighting efficiency.

4. The scope of application of the utility model is wider. In addition to general lighting, it can also be applied to plant lighting. According to the different spectral requirements of plants in different growth periods, specific color channels can be turned on by adjusting the PWM circuit to achieve specialization. illumination.

5. The protection circuit in the utility model can make the chip stop working to protect the chip when the temperature of the chip exceeds a certain temperature or the fluctuation of the mains power exceeds a certain range.

Description of drawings

FIG. 1 is a schematic structural diagram of a four-channel AC LED driver chip circuit with fine dimming according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a PWM circuit in an embodiment of the present invention.

FIG. 3 is a schematic diagram of a dimming and protection circuit in an embodiment of the present invention.

4 is a schematic diagram of a channel current generating circuit in an embodiment of the present invention.

FIG. 5 is a schematic diagram of a WRGB constant current circuit in an embodiment of the present invention.

6 is a working waveform diagram of WLED, RLED, GLED, and BLED light strings in a four-channel AC LED driver chip circuit with fine dimming according to an embodiment of the present invention under different duty cycle dimming signals.

Detailed ways

The present utility model will be described in further detail below with reference to the embodiments and the accompanying drawings, but the embodiments of the present utility model are not limited thereto.

Example

1 is a schematic structural diagram of a four-channel AC LED driver chip circuit with fine dimming, the circuit includes a rectifier bridge (1), a voltage divider circuit (12), a current detection circuit (8), and a logic control circuit (6), PWM circuit (11), dimming and protection circuit (14), channel current generation circuit (9), WRGB constant current circuit (10), WLED light string (2), RLED light string (3), GLED a light string (4), a BLED light string (5) and a protection circuit (13);

The WLED (white LED) light string, RLED (red light LED) light string, GLED (green LED) light string and BLED (blue light LED) light string all include multi-level LEDs; The second-level LED is composed of the first two adjacent LED light strings, the third-level LED is composed of the first three LED light strings, and the fourth-level LED is composed of four LED light strings.

The output end of the rectifier bridge is connected with the input end of the first-stage LED in the WLED light string, the RLED light string, the GLED light string and the BLED light string; it is used for full-wave rectification of the commercial power;

The voltage divider circuit, one end is connected with the rectifier bridge, and the other end is connected with the logic control circuit; it is used to step down the high-voltage pulsating voltage output by the rectifier, and the obtained low-voltage pulsating voltage whose amplitude is less than the chip power supply voltage is supplied to the chip. internal processing;

The current detection circuit has one end connected to the source of the high-voltage switch tubes HM1, HM5 and HM9 of the control channels 1-3, and the other end is connected to the logic control circuit; it is used to detect the current of the WLED channels 1-3, when the current reaches When the current threshold is VREF1/R1, a pulse signal is output as a signal for the channel switching of the logic control circuit.

The logic control circuit is connected to the dimming and protection circuit; it is used for the current detection circuit to output a pulse signal to act on the logic control circuit during the rising stage of the input voltage, and the output signals S1 to S12 to act on the dimming and protection circuit; In the input voltage drop stage, the logic control circuit controls the output signals S1-S12 to act on the dimming and protection circuits;

The PWM circuit is connected with the dimming and protection circuit; it is used to generate the dimming signal of the control channel corresponding to the LEDs at all levels in the WLED, RLED, GLED and BLED light strings;

The dimming and protection circuits are respectively connected with the logic control circuit, the PWM circuit, the protection circuit and the gates of the high voltage MOS transistors HM1-12 in the switch gating module (7); the output signals S1-S12, The outputs P_W, P_R, P_G, P_B of the PWM circuit and the output signal V_P of the protection circuit are comprehensively processed, and then the output signals SW1~SW12 are used to control the on-off of the switch tubes HM1~12 to realize the WLED, RLED, GLED and BLED. The rest of the LEDs at the first level are turned on and off in sequence, and at the same time, fine dimming can be achieved by dimming signals with different duty ratios, thereby realizing color driving;

The channel current generating circuit is connected to the sources of the high-voltage MOS tubes HM2-4, HM6-8, HM10-12 in the switch gating module; it is used when each channel of the RLED, GLED and BLED light strings, namely channels 5-7 , Channels 9 to 11 and channels 13 to 15 provide current when they are turned on.

The WRGB constant current circuit is connected to the output end of the last LED in the WLED light string, the RLED light string, the GLED light string and the BLED light string; when the WLED, RLED, GLED and BLED light strings are all lit, the WRGB The constant current circuit keeps the currents corresponding to channel 4, channel 8, channel 12 and channel 16 constant, and is connected to the output terminals of WLED4, RLED4, GLED4 and BLED4 units.

The protection circuit is used to provide overvoltage protection and overtemperature protection.

The rectifier bridge is a full-wave rectifier bridge, which converts the alternating current of 220V/50Hz into the DC pulsating voltage of 0-311V.

The current detection circuit includes an error amplifier and a resistor R1. When the high-voltage switches of the control channels corresponding to the LED output terminals of each level in the WLED light string are turned on, the current flows through the sampling resistor R1 to generate a voltage drop, and the voltage value is connected as a feedback signal. To the non-inverting end of the error amplifier, the inverting end of the error amplifier is connected to the reference voltage VREF1, and the output end of the error amplifier is connected to the logic control circuit.

As shown in FIG. 2 , the PWM circuit includes four comparators, the sawtooth wave voltage Vsaw is connected to the inverting input terminals of the four comparators respectively, and the external voltages V_W, V_R, V_G and V_B that generate the dimming signal are respectively connected with the inverse input terminals of the four comparators. The non-inverting input terminal of the comparator is connected, and the output terminal of the comparator is connected to the gates of the high-voltage switch tubes at all levels on WLED, RLED, GLED and BLED. By adjusting the size of the external voltage that generates the dimming signal, WLED, Dimming signals P_W, P_G, P_R and P_B with different duty cycles of RLED, GLED and BLED channels.

As shown in FIG. 3 , the dimming and protection circuit includes twelve AND gate circuits, the output signals S1-S12 of the logic control circuit, the output signals P_W, P_G, P_R, P_B of the PWM circuit, and the output signal V_P of the protection circuit They are respectively connected to the input terminals of the AND gate, and the output terminals of the AND gate are respectively connected to the gates of the high-voltage MOS tubes at all levels except the last LED on the control WLED, RLED, GLED and BLED, and the output signals SW1~SW12 respectively control the WLED. , RLED, GLED and BLED except the last level of high-voltage MOS tubes, to realize the WLED, RLED, GLED and BLED light string except the last level of LEDs in order to turn on and turn off the other levels of LEDs, and at the same time Fine dimming can be achieved by dimming signals with different duty ratios, thereby realizing color driving.

As shown in FIG. 4 , the channel current generating circuit includes an error amplifier, N-type MOS transistors MN1-11, P-type MOS transistors MP1-2 and a resistor R2. The non-inverting input terminal of the error amplifier is connected to the reference voltage VREF1, the reverse input terminal is connected to one end of the resistor R2 and the source of the MOS transistor MN1, and the output terminal is connected to the gate of the MOS transistor MN1; the drain of the MOS transistor MN1 is connected to the MOS transistor. The gate and drain of MP1 are connected to the gate of MOS transistor MP2; the sources of MOS transistors MP1 and MP2 are connected to VDD; the drain of MOS transistor MP2 is connected to the drain and gate of MOS transistor MN2 and the MOS transistor MN3 The gates of ~11 are connected to each other; the drains of MOS transistors MN3 to 11 are respectively connected to the high-voltage switch groups HM2 to 4, HM6 to 8, and HM10 to 12 in the switch gating module; the other end of the resistor R2 is connected to the MOS transistor MN2. The source of ~11 is connected to the ground; the error amplifier, MOS tube MN1 and resistor R2 form a constant current circuit to generate a current VREF1/R2, and the current mirror formed by MOS tubes MP1~2 and MN2~11 is used to channel 5~7, channel 9 to 11 and channels 13 to 15 provide current.

As shown in Figure 5, the WRGB constant current circuit includes error amplifiers OP1, OP2, OP3, OP4, high voltage MOS transistors HM13, HM14, HM15, HM16, AND gates AND1, AND2, AND3, AND4, resistors R3, R4, R5 and R6. The non-inverting input terminals of the error amplifiers OP1-4 are connected to the reference voltage VREF1, the inverting input terminal of the error amplifier OP1 is connected to one end of the resistor R3 and the source of the high voltage MOS tube HM13, and the output terminal is connected to an input terminal of the AND gate AND1. The output signal P_W of the PWM circuit and the output signal V_P of the protection circuit are connected to the other two input ends of the AND gate AND1, and the output end of the AND gate AND1 is connected to the gate of the high-voltage MOS transistor HM13. The drain is connected to the output terminal of the last stage LED in the WLED light string; the reverse input terminal of the error amplifier OP2 is connected to one end of the resistor R4 and the source of the high voltage MOS tube HM14, and the output terminal is connected to an input of the AND gate AND2 The output signal P_R of the PWM circuit and the output signal V_P of the protection circuit are connected to the other two input ends of the AND gate AND2, and the output end of the AND gate AND2 is connected to the gate of the high-voltage MOS tube HM14. The high-voltage MOS tube The drain of HM14 is connected to the output terminal of the last stage LED in the RLED light string; the reverse input terminal of the error amplifier OP3 is connected to one end of the resistor R5 and the source of the high voltage MOS tube HM15, and the output terminal is connected to the AND gate AND3. One input terminal is connected, the output signal P_G of the PWM circuit and the output signal V_P of the protection circuit are connected to the other two input terminals of the AND gate AND3, and the output terminal of the AND gate AND3 is connected to the gate of the high-voltage MOS tube HM15. The drain of the MOS tube HM15 is connected to the output terminal of the last stage LED in the GLED light string; the reverse input terminal of the error amplifier OP4 is connected to one end of the resistor R6 and the source of the high voltage MOS tube HM16, and the output terminal is connected to the AND gate. One input end of AND4 is connected, the output signal P_B of the PWM circuit and the output signal V_P of the protection circuit are connected with the other two input ends of the AND gate AND4, and the output end of the AND gate AND4 is connected with the gate of the high voltage MOS transistor HM16 , the drain of the high-voltage MOS tube HM16 is connected to the output terminal of the last LED in the BLED light string; the other ends of the resistors R3 to R6 are connected to the ground; when the WLED, RLED, GLED and BLED light strings are all lit , the current flows through the high-voltage MOS transistors HM13-16 to the sampling resistors R3-R6, and generates a voltage drop V1-V4 on the sampling voltage. The voltage value is connected to the inverting input of the error amplifier as a feedback signal, and the error amplifier OP1- 4. Under the combined action of high-voltage MOS tubes HM13~16 and resistors R3~R6, the current flowing through the WLED, RLED, GLED and BLED light strings is constant, and at the same time, fine dimming can be achieved by dimming signals with different duty ratios, and then Implement color drive.

In this embodiment, the control process of a four-channel AC LED driver chip circuit with fine dimming in one pulsating voltage cycle is as follows:

The AC mains is full-wave rectified by the rectifier bridge circuit to obtain a periodic pulsating voltage HV, which directly drives the WLED light string, RLED light string, GLED light string and BLED light string in parallel.

The pulsating voltage increases from 0. At the beginning, the high-voltage MOS transistors HM1-12 in the switch gating module are all turned on. When the pulsating voltage reaches the turn-on voltage of the WLED1, RLED1, GLED1 and BLED1 units, the current of each light string passes through their respective The first-stage LED unit flows to channel 1, channel 5, channel 9 and channel 13, and the currents IR1, IG1, and IB1 flowing to channel 5, channel 9, and channel 13 are generated by the channel current generation circuit. The error amplifier, MOS transistors MN1, MP1 and The resistor R2 generates the current VREF1/R2, and then provides current to the channel 5, the channel 9 and the channel 13 through the current mirror formed by the MOS transistors MP2, MN2 and MN3-5.

As the pulsating voltage HV gradually increases, I_WLED increases rapidly. At time t1, the current detection circuit detects that I_WLED reaches the set threshold VREF1/R1, outputs the detection signal I_P, and the logic control circuit turns off the MOS transistors HM1-4. At this time, the logic control circuit internally records the segment point voltage VS1.

As the pulsating voltage continues to rise, when the pulsating voltage reaches the turn-on voltage of the second-level LED lights, the current of each light string flows to channel 2, channel 6, channel 10 and channel 14 through the respective second-level LEDs; The currents IR2, IG2, and IB2 of channel 10 and channel 14 are generated by the channel current generation circuit. The error amplifier, MOS transistors MN1, MP1 and resistor R2 generate current VREF1/R2, and then pass through the current formed by MOS transistors MP2, MN2 and MN6-8. The mirror provides current to channel 6, channel 10 and channel 14. At time t2, the current detection circuit detects that I_WLED reaches the set threshold VREF1/R1, outputs the detection signal I_P, and the logic control circuit turns off the MOS switches HM5-8. At this time, the logic control circuit internally records the segment point voltage VS2.

As the pulsating voltage continues to rise, when the pulsating voltage reaches the turn-on voltage of the third-level LED lights, the current of each light string flows to channel 3, channel 7, channel 11 and channel 15 through the respective third-level LEDs; The currents IR3, IG3, and IB3 of channel 11 and channel 15 are generated by the channel current generation circuit. The error amplifier, MOS transistors MN1, MP1 and resistor R2 generate current VREF1/R2, and then the current formed by MOS transistors MP2, MN2 and MN9~11 The mirror provides current to channel 7, channel 11 and channel 15. At time t3, the current detection circuit detects that I_WLED reaches the set threshold VREF1/R1, outputs the detection signal I_P, and the logic control circuit turns off the MOS switches HM9-12. At this time, the logic control circuit internally records the segment point voltage VS3.

As the pulsating voltage continues to rise, when the pulsating voltage reaches the turn-on voltage of the fourth-level LED lights, the current of each light string flows to channel 4, channel 8, channel 12 and channel 16 through the respective fourth-level LEDs; the channel currents I_WLED, I_RLED, I_GLED and I_BLED are determined by the WRGB constant current circuit. The current flows through the high voltage MOS transistors HM13~16 to the sampling resistors R3~R6, and generates voltage drops V1~V4 on the sampling resistors. These voltage values are used as feedback signals to be connected to the inverse of the error amplifier. input terminal until it is equal to the non-inverting input terminal voltage VREF1, and the constant current values of the channel are respectively VREF1/R3, VREF1/R4, VREF1/R5 and VREF1/R6.

With the further increase of the pulsating voltage, the current of each LED light string can be kept stable at the constant current value. After the pulsating voltage reaches the peak value, it gradually decreases. When the pulsating voltage drops below the turn-on voltage of the fourth-level LED, the MOS switches HM9-12 are turned on, channel 3, channel 7, channel 11 and channel 15 are turned on, and the WLED4, RLED4, GLED4 and BLED4 units are turned off.

At time t4, when the pulsating voltage gradually drops to less than VS3, the logic control circuit turns on the high-voltage MOS switches HM5-8 and turns on, the channel 2, channel 6, channel 10 and channel 14 are turned on, and the LED current flows from channel 2, channel 6, channel 10 and channel 14 flow through and the WLED3, RLED3, GLED3 and BLED3 units are off.

At time t5, when the pulsating voltage gradually drops to less than VS2, the logic control circuit turns on the high-voltage MOS switches HM1-4 and turns on, the channel 1, channel 5, channel 9 and channel 13 are turned on, and the LED current flows from channel 1, channel 5, channel 9 and channel 13 flow through and the WLED2, RLED2, GLED2 and BLED2 units are off.

At time t6, when the pulsating voltage gradually decreases to less than VS1, the currents flowing through channel 1, channel 5, channel 9 and channel 13 gradually decrease, and when the pulsating voltage gradually decreases to less than the turn-on voltages of WLED1, RLED1, GLED1 and BLED1 units , the WLED1, RLED1, GLED1 and BLED1 units are off. In the above-mentioned one cycle process, fine dimming can be realized by dimming signals with different duty ratios, thereby realizing color driving, adjusting spectral distribution, and improving lighting efficiency.

FIG. 6 is a working waveform diagram of WLED, RLED, GLED, and BLED light strings in a four-channel AC LED driver chip circuit with fine dimming in the present embodiment under different duty cycle dimming signals.

The above-mentioned embodiments are preferred embodiments of the present utility model, but the embodiments of the present utility model are not limited by the above-mentioned embodiments, and any other changes, modifications, and substitutions made without departing from the spirit and principle of the present utility model , combination and simplification, all should be equivalent replacement methods, which are all included in the protection scope of the present invention.

Claims (9)

1. A four-channel AC LED driving chip circuit for fine dimming is characterized by comprising a rectifier bridge, a voltage division circuit, a current detection circuit, a logic control circuit, a PWM circuit, a dimming and protection circuit, a channel current generation circuit, a WRGB constant current circuit, a WLED lamp string, an RLED lamp string, a GLED lamp string, a BLED lamp string and a protection circuit;

the WLED lamp string, the RLED lamp string, the GLED lamp string and the BLED lamp string comprise multi-stage LEDs; the first-stage LED is composed of a first string of LED lamp strings, the second-stage LED is composed of two adjacent LED lamp strings, the third-stage LED is composed of three LED lamp strings, and the like, so that a multi-stage LED is formed;

the output end of the rectifier bridge is connected with the input ends of the first-stage LEDs in the WLED lamp string, the RLED lamp string, the GLED lamp string and the BLED lamp string;

one end of the voltage division circuit is connected with the rectifier bridge, and the other end of the voltage division circuit is connected with the logic control circuit;

one end of the current detection circuit is respectively connected with the source electrode of the high-voltage switch tube on the control channel connected with the WLED lamp string, and the other end of the current detection circuit is connected with the logic control circuit;

the logic control circuit is connected with the dimming and protection circuit; the current detection circuit is used for generating signals for controlling the sequential turn-off of the rest switch groups at each stage except the last stage of LED on WLED, RLED, GLED and BLED when the current detection circuit outputs a pulse signal to act on the logic control circuit at the rising stage of the input voltage; in the input voltage reduction stage, generating signals for controlling the sequential opening of the rest switch groups at each stage except the last stage of LED on WLED, RLED, GLED and BLED;

the PWM circuit is connected with the dimming and protection circuit; the dimming control circuit is used for generating dimming signals of control channels corresponding to LEDs of all stages in the WLED, RLED, GLED and BLED lamp strings;

one end of the dimming and protection circuit is connected with the logic control circuit, one end of the dimming and protection circuit is connected with the PWM circuit and the protection circuit, and the other end of the dimming and protection circuit is connected with a grid electrode of an MOS (metal oxide semiconductor) tube in the switch gating module; the LED dimming control circuit is used for integrating a control signal generated by the logic control circuit, a dimming signal generated by the PWM circuit and a protection signal generated by the protection circuit to control the on-off of other switch groups at each level except the last-level LED on the WLED, RLED, GLED and BLED so as to realize the sequential lighting and sequential extinguishing of the LEDs at each level of the WLED, RLED, GLED and BLED lamp strings;

the channel current generating circuit is connected with the source electrode of the MOS tube in the switch gating module;

the WRGB constant current circuit is connected with the output end of the last stage of LED in the WLED lamp string, the RLED lamp string, the GLED lamp string and the BLED lamp string;

the protection circuit is used for providing overvoltage protection and over-temperature protection.

2. The fine-dimming four-channel AC LED driving chip circuit according to claim 1, wherein the PWM circuit comprises a comparator.

3. The fine dimming four-channel AC LED driving chip circuit as claimed in claim 2, wherein in the PWM circuit, four different reference voltages are set to compare with the internal sawtooth voltage, so as to generate the dimming signals of the channels corresponding to the WLED, RLED, GLED and BLED strings.

4. The fine-dimming four-channel AC LED driving chip circuit according to claim 1, wherein the dimming and protection circuit comprises an AND gate circuit.

5. The fine dimming four-channel AC LED driving chip circuit according to claim 4, wherein in the dimming and protection circuit, the output signal of the logic control circuit, the output signal of the PWM circuit and the output signal of the protection circuit are respectively connected with an input end of an AND gate, an output end of the AND gate is connected with a grid electrode of a high-voltage switch tube in the switch gating module, and the output signals control the rest switch groups except the last stage of LED on the WLED, RLED, GLED and BLED to realize that the LEDs of the WLED, RLED, GLED and BLED light strings are sequentially turned on and off.

6. The fine-dimming four-channel AC LED driving chip circuit according to claim 1, wherein the channel current generating circuit comprises an error amplifier, a MOS (metal oxide semiconductor) transistor and a resistor R2.

7. The fine dimming four-channel AC LED driving chip circuit according to claim 1, wherein the WRGB constant current circuit comprises an error amplifier, a MOS (metal oxide semiconductor) transistor and a resistor.

8. The fine dimming four-channel AC LED driving chip circuit according to claim 7, wherein the number of error amplifiers, the number of resistors and the number of MOS (metal oxide semiconductor) tubes in the WRGB constant current circuit are the same as the number of lamp string types.

9. The fine-dimming four-channel AC LED driving chip circuit as claimed in claim 1, wherein the light string type and number are not limited to four of WLED light string, RLED light string, GLED light string, BLED light string.

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