CN210093619U

CN210093619U - Four-channel AC LED driving chip circuit with fine dimming function

Info

Publication number: CN210093619U
Application number: CN201821984836.XU
Authority: CN
Inventors: 李国元; 殷文杰; 吴朝晖; 梁志明
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2018-11-29
Filing date: 2018-11-29
Publication date: 2020-02-18
Anticipated expiration: 2028-11-29

Abstract

The utility model discloses a four passageway AC LED driver chip circuit of meticulous adjusting luminance, carry out pulsating voltage after the full wave rectification with the commercial power and drive WLED, RLED, GLED and BLED lamp cluster simultaneously, the segmentation that the light modulation signal that produces through control signal, the PWM circuit that the logic control circuit produced and the protection signal that protection circuit produced realizes each colour channel lamp cluster switches on and adjustting of the lighteness. The utility model does not need AC-DC conversion, reduces the system volume, reduces the manufacturing cost and improves the system reliability; the utility model combines the fine light modulation of different color channels through the light modulation circuit and the PWM signals with different duty ratios to realize the color driving of design parameters, and can adjust the spectrum distribution and further improve the lighting efficiency, thereby being applied to diversified lighting purposes; the utility model can adjust the color cast problem caused by the change of the current value of each color lamp string; meanwhile, the color rendering index of the LED lamp string can be improved, so that the whole color rendering performance of the system is better.

Description

Four-channel AC LED driving chip circuit with fine dimming function

Technical Field

The utility model relates to a drive circuit field especially relates to a four-channel AC LED driver chip circuit of meticulous adjusting luminance.

Background

With the development of science and technology in recent years, LEDs are distinguished as green, energy-saving, power-saving, and long-life fourth-generation lighting fixtures. The advantages of LEDs are gradually replacing incandescent lamps and fluorescent lamps, and are widely used in various illumination fields and also under great research by governments of various countries.

The traditional LED driving circuit is mostly driven by direct current, that is, an AC-DC converter is used to process the commercial power and then output direct voltage, and then the LED is driven. But the efficiency of the LED system is reduced due to the large energy losses during the conversion process. Meanwhile, the service life of the AC-DC converter is far shorter than that of the LED, and the reliability of the driving circuit is seriously influenced.

As technology advances, technology for alternating current direct drive leds (ac leds) is beginning to be developed and adopted. The techniques can be broadly divided into two categories: bridge AC LED technology and driving chip technology for AC driving HV-LED. The bridge type AC LED technology is characterized in that LED lamp beads are arranged into a structure similar to a rectifier bridge and are directly connected to commercial power by utilizing the unidirectional conduction characteristic of an LED, so that alternating current light emitting is realized; the technology of AC driving the HV-LED adopts the sectional control and constant current processing technology, so that the LED can be lighted or extinguished in sections under different input voltages, and the efficiency of the system is improved.

However, advances in technology, improvements in quality of life, and the need for energy conservation have led to an increasing range of applications for color RGB driving, such as in the fields of lighting, landscapes, and agriculture. In addition to important parameters such as color temperature and color rendering index, the LED applied to the field of lighting also pays more and more attention to the S/P ratio (S: dark brightness, P: bright brightness) of the spectrum. Research shows that the lamp bulb with a higher S/P ratio can fully utilize the sensitivity of nerve cells of human eyes to reduce the requirement of illuminance so as to protect eyes and meet the requirement of clearer visual effect, and meanwhile, the energy is further saved. The current multi-channel alternating current direct drive LED scheme adopts the mode that the color drive is realized by changing the current of each color lamp string, but the LED lamp strings emit light and have a certain color cast problem.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to solve among the prior art direct current RGB drive circuit bulky, with high costs, inefficiency and color rendering property subalternation problem to overcome multichannel AC drive LED and have the defect of colour cast, provide a four-channel AC LED driver chip circuit of meticulous adjusting luminance. The utility model has the advantages of integrated level is high, adjustable spectral distribution, color rendering property are better and efficient to have excess temperature and overvoltage protection.

The purpose of the utility model can be realized by the following technical scheme:

a four-channel AC LED driving chip circuit for fine dimming comprises 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, WLED lamp strings, RLED lamp strings, GLED lamp strings, BLED lamp strings 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 the multistage 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; the full-wave rectification circuit is used for performing full-wave rectification on commercial power;

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; the high-voltage pulse voltage is used for reducing the voltage of the high-voltage pulse voltage output by rectification, and the obtained low-voltage pulse voltage with the amplitude smaller than the power supply voltage of the chip is supplied to the internal processing of the chip;

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 device is used for detecting the magnitude of current flowing through a WLED channel, and outputting a pulse signal as a signal for switching a logic control circuit channel when the detected current reaches a current threshold value;

the logic control circuit is connected with the dimming and protection circuit; the circuit is used for generating signals for controlling the sequential turn-off of other switch groups at each stage except the last stage of LED on WLED, RLED, GLED and BLED lamp strings 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 switch groups of all the stages except the last stage of LED on the WLED, RLED, GLED and BLED lamp strings;

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 at all stages in the WLED, RLED, GLED and BLED lamp strings;

the dimming and protection circuit is respectively connected with the logic control circuit, the PWM circuit, the protection circuit and the grid electrode of the MOS 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, and then controlling the on-off of other switch groups at each stage except the last stage of LED on the WLED, RLED, GLED and BLED lamp strings to realize the sequential on-off of the LEDs at each stage 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; when the respective channels of the RLED, GLED and BLED lamp strings are started, the channel current generating circuit provides current for the RLED, GLED and BLED lamp strings;

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; when WLED, RLED, GLED and BLED lamp strings are all lighted, the WRGB constant current circuit keeps the current on the output end channel of the last stage of LED constant;

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

The rectifier bridge is a full-wave rectifier bridge and converts 220V/50Hz alternating current into 0-311V direct current pulsating voltage.

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

In the current detection circuit, when a high-voltage switch tube of a control channel corresponding to the output end of each stage of LED in the WLED lamp string is opened, current flows through a sampling resistor R1 to generate voltage drop, the voltage value is connected to the in-phase end of an error amplifier as a feedback signal, the inverted end of the error amplifier is connected with a reference voltage VREF1, and the output end of the error amplifier is connected with a logic control circuit.

The PWM circuit includes a comparator.

In the PWM circuit, sawtooth wave voltage is connected with a reverse input end of a comparator, external voltage for generating dimming signals is respectively connected with a same-direction input end of the comparator, and dimming signals with different duty ratios of channels corresponding to WLED, RLED, GLED and BLED lamp strings can be obtained by adjusting the size of the external voltage for generating the dimming signals.

The dimming and protection circuit comprises an AND gate circuit.

In the dimming and protection circuit, an output signal of a logic control circuit, an output signal of a PWM circuit and an output signal of a protection circuit are respectively connected with an input end of an AND gate, and the output signals control switch groups of all the stages except the last stage of LED on WLED, RLED, GLED and BLED lamp strings.

The channel current generating circuit comprises an error amplifier, a MOS (metal oxide semiconductor) tube and a resistor R2.

In the channel current generating circuit, an error amplifier, an MOS tube connected with the output end of the error amplifier and a resistor R2 form a constant current circuit, which provides bias current for a current mirror formed by other MOS tubes, and then provides current for the channels corresponding to the output ends of the other LED of each level except the last LED in the RLED lamp string, the channels corresponding to the output ends of the other LED of each level except the last LED in the GLED lamp string and the channels corresponding to the output ends of the other LED of each level except the last LED in the BLED lamp string.

The WRGB constant current circuit comprises an error amplifier, an MOS (metal oxide semiconductor) tube and a resistor.

Furthermore, 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.

In the WRGB constant current circuit, when the WLED, RLED, GLED and BLED lamp strings are all lighted, current flows to a sampling resistor through a high-voltage MOS tube and generates voltage drop on sampling voltage, the voltage value is connected to the inverting input end of an error amplifier as a feedback signal, the non-inverting input end of the error amplifier is connected with a reference voltage VREF1, and the output end of the error amplifier is connected with the grid electrode of the high-voltage MOS tube.

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

The utility model discloses compare in prior art, have following beneficial effect:

1. the utility model discloses need not to carry out the AC-DC conversion, reduced the system volume, reduced manufacturing cost, improved system reliability.

2. The utility model discloses a PWM signal adjusts luminance to each lamp cluster, can improve the colour cast problem of adjusting luminance and producing through changing each lamp cluster electric current, and lamp cluster WLED's joining can improve the color rendering index of lamp cluster simultaneously, makes the whole color rendering property of system better.

3. The utility model discloses can realize the LED lamp of high S/P ratio in order to change spectral distribution according to under the low light intensity condition, through the duty cycle of each colour lamp cluster dimming signal of regulation control, can utilize the sensitivity of people' S eye better, protect eyes and optimization illuminating effect, further improve the illuminating efficiency.

4. The utility model discloses an application scope is wider, except that ordinary illumination, can also be applied to the plant illumination, and its spectral demand is different at the growth period of difference according to the plant, can make specific colour passageway switch on through adjusting the PWM circuit, realizes the specialization illumination.

5. The utility model discloses thereby well protection circuit can make chip stop work protect the chip when the chip surpasss the uniform temperature or the commercial power is undulant to exceed the certain limit.

Drawings

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

Fig. 2 is a schematic diagram of a PWM circuit according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of a dimming and protection circuit according to an embodiment of the present invention.

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

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

Fig. 6 is a waveform diagram of the work of the WLED, RLED, GLED, BLED light string under the dimming signals with different duty ratios in the fine dimming four-channel AC LED driving chip circuit according to the embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following examples and drawings, but the present invention is not limited thereto.

Examples

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

the WLED (white light LED) lamp string, the RLED (red light LED) lamp string, the GLED (green light LED) lamp string and the BLED (blue light LED) lamp string comprise multistage 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 fourth-stage LED is composed of four LED lamp strings.

one end of the current detection circuit is connected with the source electrodes of the high-voltage switching tubes HM1, HM5 and HM9 of the control channels 1-3, and the other end of the current detection circuit is connected with the logic control circuit; the detection circuit is used for detecting the current magnitude of WLED channels 1-3, and when the current reaches a current threshold value VREF1/R1, a pulse signal is output and used as a signal for switching the channels of the logic control circuit.

The logic control circuit is connected with the dimming and protection circuit; the current detection circuit is used for outputting a pulse signal to act on the logic control circuit in the rising stage of the input voltage, and the output signals S1-S12 act on the dimming and protection circuit; in the input voltage reduction stage, the logic control circuit controls output signals S1-S12 to act on the dimming and protection circuit;

the dimming and protection circuit is respectively connected with the logic control circuit, the PWM circuit, the protection circuit and the grid electrodes of high-voltage MOS (metal oxide semiconductor) transistors HM1-12 in the switch gating module (7); output signals S1-S12 of the logic control circuit, output signals P _ W, P _ R, P _ G and P _ B of the PWM circuit and output signals V _ P of the protection circuit are comprehensively processed, then output signals SW 1-SW 12 are used for controlling the on-off of switch tubes HM1-12, the sequential lighting and sequential extinguishing of the rest stages of LEDs except the last stage of LED on WLED, RLED, GLED and BLED are achieved, meanwhile, fine dimming can be achieved through dimming signals with different duty ratios, and further color driving is achieved;

the channel current generation circuit is connected with the source electrodes of high-voltage MOS tubes HM 2-4, HM 6-8 and HM 10-12 in the switch gating module; the circuit is used for providing current for each channel of the RLED, GLED and BLED lamp strings when the channel, namely the channel 5-7, the channel 9-11 and the channel 13-15, is opened.

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; when the WLED, RLED, GLED and BLED light strings are all lighted, the WRGB constant current circuit keeps the current of the corresponding channel 4, channel 8, channel 12 and channel 16 constant, and is connected with the output ends of the WLED4, RLED4, GLED4 and BLED4 units.

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

As shown in fig. 2, the PWM circuit includes four comparators, the sawtooth voltage Vsaw is respectively connected to the inverting input terminals of the four comparators, the external voltages V _ W, V _ R, V _ G and V _ B for generating the dimming signals are respectively connected to the inverting input terminals of the comparators, the output terminals of the comparators are connected to the gates of the high-voltage switching tubes of the stages of WLED, RLED, GLED and block, and the dimming signals P _ W, P _ G, P _ R and P _ B with different duty ratios of the channels WLED, RLED, GLED and block can be obtained by adjusting the magnitude of the external voltage for generating the dimming signals.

As shown in fig. 3, the dimming and protection circuit includes twelve and gate circuits, output signals S1-S12 of the logic control circuit, output signals P _ W, P _ G, P _ R, P _ B of the PWM circuit, and output signals V _ P of the protection circuit are respectively connected to input ends of the and gates, output ends of the and gates are respectively connected to gates of high-voltage MOS transistors of the rest stages except the last stage of LEDs on the WLED, RLED, GLED, and BLED, and output signals SW 1-SW 12 respectively control the high-voltage MOS transistors of the rest stages except the last stage of LEDs on the WLED, RLED, GLED, and BLED, so as to sequentially turn on and off the rest stages except the last stage of LEDs on the WLED, RLED, GLED, and BLED, and fine dimming can be realized by dimming signals with different duty ratios, thereby realizing color driving.

As shown in FIG. 4, the channel current generation circuit includes an error amplifier, N-type MOS transistors MN 1-11, P-type MOS transistors MP 1-2 and a resistor R2. The non-inverting input end of the error amplifier is connected with a reference voltage VREF1, the inverting input end of the error amplifier is connected with one end of a resistor R2 and the source electrode of an MOS transistor MN1, and the output end of the error amplifier is connected with the gate electrode of an MOS transistor MN 1; the drain electrode of the MOS transistor MN1 is connected with the grid electrode and the drain electrode of the MOS transistor MP1 and the grid electrode of the MOS transistor MP 2; the sources of the MOS tubes MP1 and MP2 are connected with VDD; the drain electrode of the MOS tube MP2 is connected with the drain electrode and the grid electrode of the MOS tube MN2 and the grid electrodes of the MOS tubes MN 3-11; the drains of the MOS tubes MN 3-11 are respectively connected with high-voltage switch groups HM 2-4, HM 6-8 and HM 10-12 in the switch gating module; the other end of the resistor R2 and the source electrodes of the MOS tubes MN 2-11 are connected with the ground; the error amplifier, the MOS transistor MN1 and the resistor R2 form a constant current circuit to generate current VREF1/R2, and current is provided for the channels 5-7, the channels 9-11 and the channels 13-15 through a current mirror formed by the MOS transistors MP 1-2 and the MOS transistors MN 2-11.

As shown in fig. 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, AND resistors R3, R4, R5, AND R6. The non-inverting input ends of error amplifiers OP 1-4 are all connected with a reference voltage VREF1, the inverting input end of an error amplifier OP1 is connected with one end of a resistor R3 AND the source electrode of a high-voltage MOS tube HM13, the output end of the error amplifier OP1 is connected with one input end of an AND gate AND1, an output signal P _ W of a PWM circuit, an output signal V _ P of a protection circuit AND the other two input ends of an AND gate AND1 are connected, the output end of the AND gate AND1 is connected with the grid electrode of the high-voltage MOS tube HM13, AND the drain electrode of the high-voltage MOS tube HM13 is connected with the output end; the reverse input end of the error amplifier OP2 is connected with one end of the resistor R4 AND the source electrode of the high-voltage MOS tube HM14, the output end is connected with one input end 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 with the other two input ends of the AND gate AND2, the output end of the AND gate AND2 is connected with the grid electrode of the high-voltage MOS tube HM14, AND the drain electrode of the high-voltage MOS tube HM14 is connected with the output end of the last stage of LEDs in the RLED lamp string; the reverse input end of the error amplifier OP3 is connected with one end of the resistor R5 AND the source electrode of the high-voltage MOS tube HM15, the output end is connected with one input end of the AND gate AND3, the output signal P _ G 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 AND3, the output end of the AND gate AND3 is connected with the grid electrode of the high-voltage MOS tube HM15, AND the drain electrode of the high-voltage MOS tube HM15 is connected with the output end of the last stage of LED in the GLED lamp string; the reverse input end of the error amplifier OP4 is connected with one end of a resistor R6 AND the source electrode of a high-voltage MOS tube HM16, the output end of the error amplifier OP4 is connected with one input end of an AND gate AND4, an output signal P _ B of the PWM circuit AND an output signal V _ P of the protection circuit are connected with the other two input ends of the AND gate AND4, the output end of the AND gate AND4 is connected with the grid electrode of a high-voltage MOS tube HM16, AND the drain electrode of the high-voltage MOS tube HM16 is connected with the output end of the last stage of LED in the; the other ends of the resistors R3-R6 are all connected with the ground; when the WLED, RLED, GLED and BLED light strings are all lighted, current flows to sampling resistors R3-R6 through high-voltage MOS tubes HM 13-16, voltage drop V1-V4 is generated on sampling voltage, the voltage value is connected to the reverse input end of an error amplifier as a feedback signal, under the combined action of the error amplifier OP 1-4, the high-voltage MOS tubes HM 13-16 and the resistors R3-R6, the current flowing through the WLED, RLED, GLED and BLED light strings is constant, meanwhile, fine dimming can be realized through dimming signals with different duty ratios, and further, color driving is realized.

In this embodiment, a control flow of a fine dimming four-channel AC LED driving chip circuit in a pulsating voltage cycle specifically includes:

alternating current commercial power is subjected to full-wave rectification by a rectifier bridge circuit to obtain periodic pulsating voltage HV, and the WLED lamp string, the RLED lamp string, the GLED lamp string and the BLED lamp string are directly driven in parallel.

The ripple voltage is increased from 0, the high-voltage MOS transistors HM1-12 in the switch gating module are all in an on state at the beginning, when the ripple voltage reaches the turn-on voltage of the WLED1, RLED1, GLED1 and BLED1 units, the string currents respectively flow to the channel 1, the channel 5, the channel 9 and the channel 13 through the first-stage LED units, the currents IR1, IG1 and IB1 flowing to the channel 5, the channel 9 and the channel 13 are generated by a channel current generation circuit, the error amplifier, the MOS transistors MN1, MP1 and the resistor R2 generate currents VREF1/R2, and then the currents are provided for the channel 5, the channel 9 and the channel 13 through the current mirrors formed by the MOS transistors MP2, MN2 and MN 3-5.

As the ripple voltage HV gradually increases, I _ WLED rapidly increases. At the time t1, the current detection circuit detects that the I _ WLED reaches a set threshold value VREF1/R1, outputs a detection signal I _ P, the logic control circuit turns off the MOS transistors HM 1-4, and at the moment, the logic control circuit records the segment point voltage VS 1.

With the continuous rising of the pulsating voltage, when the pulsating voltage reaches the starting voltage of the second-stage LED lamp, the current of each lamp string flows to the channel 2, the channel 6, the channel 10 and the channel 14 through the respective second-stage LED; at this time, currents IR2, IG2 and IB2 flowing to the channel 6, the channel 10 and the channel 14 are generated by a channel current generating circuit, a current VREF1/R2 is generated by an error amplifier, MOS tubes MN1 and MP1 and a resistor R2, and then the currents are provided for the channel 6, the channel 10 and the channel 14 through a current mirror formed by the MOS tubes MP2 and MN2 and MN 6-8. At the time t2, the current detection circuit detects that the I _ WLED reaches a set threshold value VREF1/R1, a detection signal I _ P is output, the logic control circuit turns off the MOS switch tubes HM 5-8, and at the moment, the logic control circuit records the segment point voltage VS 2.

With the continuous rising of the pulsating voltage, when the pulsating voltage reaches the starting voltage of the third-stage LED lamp, the current of each lamp string flows to the channel 3, the channel 7, the channel 11 and the channel 15 through the respective third-stage LED; at this time, currents IR3, IG3 and IB3 flowing to the channel 7, the channel 11 and the channel 15 are generated by a channel current generating circuit, the error amplifier, the MOS tubes MN1 and MP1 and the resistor R2 generate currents VREF1/R2, and then the currents are provided for the channel 7, the channel 11 and the channel 15 through a current mirror formed by the MOS tubes MP2 and MN2 and MN 9-11. At the time t3, the current detection circuit detects that the I _ WLED reaches a set threshold value VREF1/R1, outputs a detection signal I _ P, the logic control circuit turns off the MOS switch tubes HM 9-12, and at the moment, the logic control circuit records the segment point voltage VS 3.

With the continuous rising of the pulsating voltage, when the pulsating voltage reaches the turn-on voltage of the fourth-stage LED lamp, the current of each lamp string flows to the channel 4, the channel 8, the channel 12 and the channel 16 through the fourth-stage LED respectively; the channel currents I _ WLED, I _ RLED, I _ GLED and I _ BLED are determined by a WRGB constant current circuit, the currents flow to sampling resistors R3-R6 through high-voltage MOS transistors HM 13-16, voltage drops V1-V4 are generated on the sampling resistors, the voltage values are connected to the reverse input end of the error amplifier as feedback signals until the voltage values are equal to the voltage VREF1 of the non-inverting input end, and the obtained constant current values of the channels are VREF1/R3, VREF1/R4, VREF1/R5 and VREF1/R6 respectively.

With the further increase of the pulsating voltage, the current of each LED string light can be maintained to be stabilized at a constant current value, the pulsating voltage gradually decreases after reaching a peak value, the current is not enough to be maintained to be constant after decreasing to a certain degree, the current of each LED string light starts to decrease, when the pulsating voltage decreases to be smaller than the turn-on voltage of the fourth-stage LED, the MOS switch tubes HM 9-12 are opened, the channel 3, the channel 7, the channel 11 and the channel 15 are conducted, and the WLED4, the RLED4, the GLED4 and the BLED4 are extinguished.

At the time of t4, when the ripple voltage gradually drops to be less than VS3, the logic control circuit opens the high-voltage MOS switching tubes HM 5-8 to be opened, the channel 2, the channel 6, the channel 10 and the channel 14 are conducted, the LED current flows through the channel 2, the channel 6, the channel 10 and the channel 14, and the WLED3, the RLED3, the GLED3 and the BLED3 units are extinguished.

At the time of t5, when the ripple voltage gradually drops to be less than VS2, the logic control circuit opens the high-voltage MOS switching tubes HM 1-4 to be opened, the channel 1, the channel 5, the channel 9 and the channel 13 are conducted, the LED current flows through the channel 1, the channel 5, the channel 9 and the channel 13, and the WLED2, the RLED2, the GLED2 and the BLED2 units are extinguished.

At time t6, when the ripple voltage gradually drops below VS1, the current flowing through channel 1, channel 5, channel 9, and channel 13 gradually decreases, and when the ripple voltage gradually drops below the turn-on voltage of WLED1, RLED1, GLED1, and BLED1 cells, the WLED1, RLED1, GLED1, and BLED1 cells extinguish. In the period process, fine dimming can be realized by dimming signals with different duty ratios, so that color driving is realized, spectral distribution is adjusted, and the lighting efficiency is improved.

Fig. 6 is a waveform diagram of the operation of the WLED, RLED, GLED, BLED light strings in the fine dimming four-channel AC LED driving chip circuit according to the present embodiment under different duty cycle dimming signals.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be equivalent replacement modes, and all are included in the scope of the present invention.

Claims

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;

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.