CN112188684A - Constant-current LED driving circuit, device and driving method thereof - Google Patents

Constant-current LED driving circuit, device and driving method thereof Download PDF

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Publication number
CN112188684A
CN112188684A CN202011050315.9A CN202011050315A CN112188684A CN 112188684 A CN112188684 A CN 112188684A CN 202011050315 A CN202011050315 A CN 202011050315A CN 112188684 A CN112188684 A CN 112188684A
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voltage
module
sampling
constant current
resistor
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CN112188684B (en
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叶羽安
陈博
邓迅升
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Shenzhen Sendis Semiconductor Co Ltd
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Shenzhen Sendis Semiconductor Co Ltd
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/345—Current stabilisation; Maintaining constant current

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Abstract

The invention discloses a constant current LED drive circuit, a device and a drive method thereof, wherein the constant current LED drive circuit comprises an LED lamp string, a voltage sampling module, a sampling processing module and a constant current module; the voltage sampling module is connected with the output end of the LED lamp string and the sampling processing module, the sampling processing module is connected with the constant current module, and the constant current module is also connected with the output end of the LED lamp string; the voltage sampling module is used for outputting sampling voltage to the sampling processing module according to the voltage signal at the output end of the LED lamp string; the sampling processing module is used for increasing the current first dimming voltage to a second dimming voltage and outputting the second dimming voltage to the constant current module when judging that the sampling voltage is greater than a preset voltage; the constant current module is used for setting constant current flowing through the LED lamp string according to the second dimming voltage, so that the luminous efficiency of the LED lamp string is improved when the voltage of a mains supply network is increased.

Description

Constant-current LED driving circuit, device and driving method thereof
Technical Field
The invention relates to the technical field of LEDs, in particular to a constant-current LED driving circuit, a constant-current LED driving device and a constant-current LED driving method.
Background
In the conventional LED non-stroboscopic constant current scheme, as shown in fig. 1, commercial power is rectified by a rectifier bridge and then connected to a capacitor to ground, and the capacitor is used to maintain the current of the LED light string when the voltage of the wire mesh is lower than that of the LED light string. When the voltage of the commercial power network rises, the voltage of the capacitor rises, but the current of the LED lamp string is constant, the voltage drop of the LED lamp string is constant, and the voltage drop of the LED lamp string is constant, as shown in fig. 2a and 2b, the voltage of the commercial power network rises and falls on the constant current chip, so that the power consumption of the constant current chip is increased, and the luminous efficiency of the LED lamp string is reduced.
Thus, the prior art has yet to be improved and enhanced.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a constant current LED driving circuit, a constant current LED driving device and a driving method thereof, which can effectively solve the problems that the power consumption of a constant current chip is increased and the light emitting efficiency of an LED lamp string is reduced because the rising voltage of a mains supply network falls on the constant current chip in the conventional constant current scheme.
In order to achieve the purpose, the invention adopts the following technical scheme:
a constant current LED drive circuit comprises an LED lamp string, a voltage sampling module, a sampling processing module and a constant current module; the voltage sampling module is connected with the output end of the LED lamp string and the sampling processing module, the sampling processing module is connected with the constant current module, and the constant current module is also connected with the output end of the LED lamp string; the voltage sampling module is used for outputting sampling voltage to the sampling processing module according to the voltage signal at the output end of the LED lamp string; the sampling processing module is used for increasing the current first dimming voltage to a second dimming voltage and outputting the second dimming voltage to the constant current module when judging that the sampling voltage is greater than a preset voltage; the constant current module is used for setting constant current flowing through the LED lamp string according to the second dimming voltage.
The constant-current LED driving circuit also comprises a voltage maintaining module, and the voltage maintaining module is respectively connected with the sampling processing module and the constant-current module; the voltage maintaining module is used for storing the peak voltage of the first dimming voltage or the second dimming voltage.
In the constant current LED driving circuit, the sampling processing module is specifically configured to, when it is determined that the sampling voltage is greater than a preset voltage, multiply a difference between the sampling voltage and the preset voltage by a preset coefficient, add the difference to the current first dimming voltage, and output the second dimming voltage to the constant current module.
In the constant-current LED driving circuit, the sampling processing module comprises a comparison unit, a switch unit and a voltage output unit; the comparison unit is respectively connected with the voltage sampling module and the switch unit, the switch unit is connected with the voltage output unit, and the voltage output unit is also connected with the constant current module; the comparison unit is used for controlling the switch unit to be conducted when judging that the sampling voltage is greater than the preset voltage; the voltage output unit is used for multiplying a difference value between the sampling voltage and the preset voltage by a preset coefficient when the switch unit is switched on, adding the difference value to the current first dimming voltage, and outputting the second dimming voltage to the constant current module.
In the constant current LED driving circuit, the comparison unit comprises a first operational amplifier, a second operational amplifier and a first resistor; the positive phase input end of the first operational amplifier is connected with the voltage sampling module, the negative phase input end of the first operational amplifier is connected with the switch unit and one end of the first resistor, the output end of the first operational amplifier is connected with the switch unit, the other end of the first resistor is connected with the output end of the second operational amplifier and the negative phase input end of the second operational amplifier, and the positive phase input end of the second operational amplifier is connected with the voltage source.
In the constant current LED driving circuit, the switch unit comprises a first MOS tube, the grid electrode of the first MOS tube is connected with the output end of the first operational amplifier, the source electrode of the first MOS tube is connected with the inverting input end of the first operational amplifier and one end of the first resistor, and the drain electrode of the first MOS tube is connected with the voltage output unit.
In the constant-current LED driving circuit, the voltage output unit comprises a second MOS tube, a third MOS tube, a fourth MOS tube, a fifth MOS tube, a sixth MOS tube, a second resistor, a third resistor and a third operational amplifier; the grid electrode of the second MOS tube is connected with the grid electrode of the third MOS tube, the drain electrode of the second MOS tube and the drain electrode of the first MOS tube, the source electrode of the second MOS tube is connected with the source electrode of the third MOS tube, the drain electrode of the third MOS tube is connected with the drain electrode of the fifth MOS tube, one end of a third resistor and the constant current module, the grid electrode of the fourth MOS tube is connected with the grid electrode of the fifth MOS tube, the drain electrode of the fourth MOS tube and the drain electrode of the sixth MOS tube, the source electrode of the fourth MOS tube is connected with the source electrode of the fifth MOS tube, the source electrode of the sixth MOS tube is connected with the inverting input end of the third operational amplifier and one end of the second resistor, the grid electrode of the sixth MOS tube is connected with the output end of the third operational amplifier, the positive phase input end of the third operational amplifier is connected with a voltage source, and the other end of the second resistor and the other end of the third resistor are both grounded.
In the constant-current LED driving circuit, the voltage sampling module comprises a fourth resistor and a fifth resistor; one end of the fourth resistor is connected with the output end of the LED lamp string, the other end of the fourth resistor is connected with the positive phase input end of the first operational amplifier and one end of the fifth resistor, and the other end of the fifth resistor is grounded.
A driving method based on the constant-current LED driving circuit comprises the following steps:
the voltage sampling module samples a voltage signal at the output end of the LED lamp string and outputs the sampled voltage to the sampling processing module;
when the sampling processing module judges that the sampling voltage is greater than the preset voltage, the current first dimming voltage is increased to a second dimming voltage and then the second dimming voltage is output to the constant current module;
and the constant current module sets the constant current flowing through the LED lamp string according to the second dimming voltage.
A constant-current LED driving device comprises a PCB, wherein the PCB is provided with the constant-current LED driving circuit.
Compared with the prior art, the constant current LED driving circuit, the device and the driving method thereof provided by the invention have the advantages that the constant current LED driving circuit comprises an LED lamp string, a voltage sampling module, a sampling processing module and a constant current module; the voltage sampling module is connected with the output end of the LED lamp string and the sampling processing module, the sampling processing module is connected with the constant current module, and the constant current module is also connected with the output end of the LED lamp string; the voltage sampling module is used for outputting sampling voltage to the sampling processing module according to the voltage signal at the output end of the LED lamp string; the sampling processing module is used for increasing the current first dimming voltage to a second dimming voltage and outputting the second dimming voltage to the constant current module when judging that the sampling voltage is greater than a preset voltage; the constant current module is used for setting constant current flowing through the LED lamp string according to the second dimming voltage, so that the luminous efficiency of the LED lamp string is improved when the voltage of a mains supply network is increased.
Drawings
Fig. 1 is a circuit schematic diagram of a conventional constant current LED driving circuit;
FIG. 2a is a voltage waveform diagram of an LED in a conventional constant current LED driving circuit;
fig. 2b is a voltage waveform diagram of an LED when the voltage of the mains network increases in the conventional constant current LED driving circuit;
fig. 3 is a block diagram of a constant current LED driving circuit according to the present invention;
FIG. 4a is a voltage waveform diagram of the LED lamp string in the constant current LED driving circuit according to the present invention
Fig. 4b is a voltage waveform diagram of the LED lamp string when the voltage of the mains network is increased in the constant current LED driving circuit according to the present invention;
fig. 5 is a schematic circuit diagram of a first embodiment of a constant current LED driving circuit according to the present invention;
fig. 6 is a schematic circuit diagram of a second embodiment of the constant current LED driving circuit according to the present invention;
fig. 7 is a flowchart illustrating steps of a driving method of a constant current LED driving circuit according to the present invention.
Detailed Description
The constant-current LED driving circuit, the device and the driving method thereof can effectively solve the problems that the power consumption of a constant-current chip is increased and the luminous efficiency of an LED lamp string is reduced because the voltage of a mains supply net rises and falls onto the constant-current chip in the conventional constant-current scheme.
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 3, the constant current LED driving circuit provided by the present invention includes a rectifier bridge 100, an LED string 200, a voltage sampling module 300, a sampling processing module 400, a constant current module 500, and an energy storage capacitor C0, wherein the voltage sampling module 300, the sampling processing module 400, and the constant current module 500 are all integrated inside a constant current chip; the voltage sampling module 300 is connected with the output end of the LED lamp string 200 and the sampling processing module 400, the sampling processing module 400 is connected with the constant current module 500, the constant current module 500 is further connected with the output end of the LED lamp string 200, the input end of the LED lamp string 200 is connected with the output end of the rectifier bridge 100, the input end of the rectifier bridge 100 is connected with an alternating current power supply, one end of the energy storage capacitor C0 is connected with the output end of the rectifier bridge 100, and the other end of the energy storage capacitor C0 is grounded.
In the first embodiment of the present invention, the rectifier bridge 100 is used for rectifying the ac power outputted by the ac power supply and outputting the line voltage to the LED light string 200 and the energy storage capacitor C0; when the voltage of the commercial power grid rises, the corresponding line voltage rises, the voltage on the energy storage capacitor C0 rises, the voltage at the output end of the LED light string 200, that is, the voltage at the negative end, rises, and the voltage sampling module 300 is configured to output the sampling voltage to the sampling processing module 400 according to the voltage signal at the output end of the LED light string 200; the sampling processing module 400 is configured to increase the current first dimming voltage to a second dimming voltage and output the second dimming voltage to the constant current module 500 when determining that the sampling voltage is greater than the preset voltage; the constant current module 500 is configured to set a constant current flowing through the LED light string 200 according to the second dimming voltage, so as to control the brightness of the LED light string 200.
In the invention, the voltage sampling module 300 is arranged at the negative end of the LED lamp string 200 to sample the voltage signal at the negative end, then the sampling processing module 400 judges and processes the voltage signal, when the sampled voltage is greater than the preset voltage, the voltage of a mains supply line network rises, then the sampling processing module 400 correspondingly increases the first dimming voltage of the current constant current module 500 to the second dimming voltage, then the constant current module 500 sets the constant current flowing through the LED lamp string 200 according to the second dimming voltage, and the constant current correspondingly set due to the increase of the dimming voltage also increases, so that the current value of the constant current is adjusted to increase along with the increase of the line voltage; the voltage difference between the input end and the output end of the LED lamp string 200, that is, between the positive end and the negative end, changes with the constant current flowing through the LED lamp string 200, and when the constant current increases, the voltage difference increases, and when the constant current decreases, the voltage difference decreases; therefore, when the constant current of the LED light string 200 increases, the voltage drop of the LED light string 200 also increases, and the voltage dropped on the constant current chip is substantially unchanged or slightly increased, so that the power consumption of the constant current chip is substantially unchanged, and the light emitting efficiency of the LED light string 200 is improved.
When the sampling module is used to determine that the sampling voltage is not greater than the preset voltage, it indicates that the mains network voltage is not increased, then the sampling processing module 400 does not change the dimming voltage currently output to the constant current module 500, and the constant current module 500 still sets the constant current of the LED light string 200 with the current first dimming voltage, thereby implementing brightness control of the LED light string.
Specifically, the average voltage of the energy storage capacitor C0 is recorded as VCAPThe voltage drop of the LED light string 200 is VLEDThe constant current of the LED lamp string 200 is ILEDTotal input power of the circuit system is PGeneral assemblyThe power of the LED lamp string 200 is PLED(ii) a Wherein, when the mains supply network voltage is normal, PGeneral assembly＝VCAP*ILED；PLED＝VLED*ILEDThe luminous efficiency of the LED lamp string 200 is PLED/PGeneral assembly。
According to the prior art, when the voltage of the utility grid rises, the total input power of the circuit system is PGeneral assemblyThe power of the LED lamp string 200 is PLEDThe average voltage on capacitor is increased by delta V;
Pgeneral assembly`＝VCAP*ILED+△V*ILED
`
PLED＝VLED*ILED
Luminous efficiency of LED light string 200:
PLED`/Pgeneral assembly`＝PLED/(VCAP*ILED+△V*ILED)
Because of PLED`/PGeneral assembly`＝PLED/(VCAP*ILED+△V*ILED)<PLED/PGeneral assembly(ii) a Therefore, when the voltage of the mains line network increases, the voltage of the energy storage capacitor C0 increases, but the current of the LED light string 200 does not change, the voltage drop of the LED light string 200 does not change, the system input power increases, and the power of the LED light string 200 does not change, which leads to the low light emitting efficiency of the system LED light string 200.
At this time, if the constant current flowing through the LED lamp string 200 is increased, the voltage drop of the LED lamp string 200 is increased by Δ V', and the constant current flowing through the LED lamp string 200 is increased by Δ ILED`；
PGeneral assembly`＝(VCAP+△V)*(ILED+△ILED`)
PLED`＝(VLED+△V`)*(ILED+△ILED`)
Luminous efficiency of LED light string 200:
PLED/Pgeneral assembly`＝{(VLED+△V`)*(ILED+△ILED`)}/(VCAP+△V)*(ILED+△ILED`)＝(VLED+△V`)/(VCAP+. Δ V). Therefore, in the present invention, when the voltage of the utility power network rises, the voltage drop of the LED light string 200 is increased by increasing the current of the LEDs, so that (VLED +/Δ V')/(VCAP +/Δ V) is substantially maintained, as shown in fig. 4a and 4b, the voltage falling to the constant current chip is substantially unchanged, thereby effectively solving the problem of the light emitting efficiency of the LED light string 200 of the circuit system being reduced when the voltage of the utility power network rises in the conventional scheme.
Further, the constant current LED driving circuit further includes a power supply module 700 and a voltage maintaining module 600, the power supply module 700 is connected to the output end of the rectifier bridge 100, and the voltage maintaining module 600 is respectively connected to the sampling processing module 400 and the constant current module 500; the power supply module 700 is configured to provide electric energy to the voltage sampling module 300, the sampling processing module 400, and the constant current module 500 according to the line voltage, so as to ensure that the voltage sampling module 300, the sampling processing module 400, and the constant current module 500 operate normally; the voltage maintaining module 600 is used for storing the peak voltage of the first dimming voltage or the second dimming voltage, so as to ensure that the LED light string 200 has no stroboscopic effect; in the invention, the voltage maintaining module 600 is arranged to enable the constant-current LED driving circuit to be applied to the field of no stroboflash, so as to ensure that the LED lamp string has no stroboflash.
Further, the sampling processing module 400 is specifically configured to, when it is determined that the sampling voltage is greater than the preset voltage, multiply a difference between the sampling voltage and the preset voltage by a preset coefficient, add the difference to the current first dimming voltage, and output a second dimming voltage to the constant current module 500, and when it is determined that the sampling voltage is less than or equal to the preset voltage, it indicates that the mains voltage is not increased, then the sampling processing module 400 does not change the current dimming voltage output to the constant current module 500, and the constant current module 500 still sets the constant current of the LED light string 200 with the current first dimming voltage; specifically, in this embodiment, when the voltage of the mains network is increased, the dimming voltage is correspondingly increased to increase the constant current, so that the voltage drop of the LED lamp string 200 is increased, thereby reducing the power consumption of the constant current chip and improving the light emitting efficiency of the LED lamp string 200; otherwise, if the voltage of the mains network is not increased, the current first dimming voltage is not changed.
Further, referring to fig. 5, the sampling processing module 400 includes a comparing unit 410, a switching unit 420 and a voltage output unit 430; the comparing unit 410 is respectively connected with the voltage sampling module 300 and the switching unit 420, the switching unit 420 is connected with the voltage output unit 430, and the voltage output unit 430 is further connected with the constant current module 500; the comparing unit 410 is used for controlling the switch unit 420 to be switched on when the sampling voltage is judged to be greater than the preset voltage; the voltage output unit 430 is configured to, when the switch unit 420 is turned on, multiply a difference between the sampling voltage and a preset voltage by a preset coefficient, add the difference to the current first dimming voltage, and output a second dimming voltage to the constant current module 500, so as to increase the first dimming voltage to the second dimming voltage, so as to implement setting of a constant current of the LED lamp string 200; the predetermined coefficient is determined by the specific circuit structure of the sampling processing module 400.
In a normal state, the voltage output unit 430 of the constant current LED driving circuit directly outputs a first dimming voltage to the constant current module 500, so that the constant current module 500 sets the current of the LED string 200 according to the first dimming voltage; when the mains line network voltage increases, the voltage sampling module 300 samples the voltage from the negative end of the LED light string 200 and outputs the voltage to the determining unit, and when the determining unit compares that the sampled voltage is greater than the preset voltage, the determining unit controls the switch unit 420 to be turned on, so that the voltage output unit 430 increases the first dimming voltage to the second dimming voltage, so as to increase the constant current of the LED light string 200; when the judgment unit compares that the sampling voltage is less than or equal to the preset voltage, the current first dimming voltage is not changed, and the current constant current of the LED lamp string 200 is not changed, so that the luminous efficiency of the LED lamp string 200 is improved when the voltage of the mains supply network is increased.
Further, the comparing unit 410 includes a first operational amplifier OP1, a second operational amplifier OP2, and a first resistor R1; the non-inverting input terminal of the first operational amplifier OP1 is connected to the voltage sampling module 300, the inverting input terminal of the first operational amplifier OP1 is connected to the switching unit 420 and one end of the first resistor R1, the output terminal of the first operational amplifier OP1 is connected to the switching unit 420, the other end of the first resistor R1 is connected to the output terminal of the second operational amplifier OP2 and the inverting input terminal of the second operational amplifier OP2, and the non-inverting input terminal of the second operational amplifier OP2 is connected to the voltage source.
Further, the switch unit 420 includes a first MOS transistor M1, a gate of the first MOS transistor M1 is connected to the output terminal of the first operational amplifier OP1, a source of the first MOS transistor M1 is connected to the inverting input terminal of the first operational amplifier OP1 and one end of the first resistor R1, and a drain of the first MOS transistor M1 is connected to the voltage output unit 430, where the first MOS transistor M1 is an N-channel MOS transistor, and when the first operational amplifier OP1 compares that the sampling voltage is greater than the preset voltage, the first MOS transistor M1 is controlled to be turned on by outputting a high-level signal; when the first operational amplifier OP1 compares that the sampling voltage is less than or equal to the preset voltage, the first MOS transistor M1 is controlled to be turned off by outputting a low level signal, so that the working state of the MOS transistor is effectively controlled by comparing the sampling voltage with the preset voltage, and the subsequent voltage output unit 430 adjusts the current first dimming voltage.
Further, the voltage output unit 430 includes a second MOS transistor M2, a third MOS transistor M3, a fourth MOS transistor M4, a fifth MOS transistor M5, a sixth MOS transistor M6, a second resistor R2, a third resistor R3, and a third operational amplifier OP 3; a gate of the second MOS transistor M2 is connected to a gate of the third MOS transistor M3, a source of the second MOS transistor M2 and a drain of the first MOS transistor M1, a source of the second MOS transistor M2 is connected to a source of the third MOS transistor M3, a drain of the third MOS transistor M3 is connected to a drain of the fifth MOS transistor M5, one end of the third resistor R3 and the constant current module 500, a gate of the fourth MOS transistor M4 is connected to a gate of the fifth MOS transistor M5, a drain of the fourth MOS transistor M4 and a drain of the sixth MOS transistor M6, a source of the fourth MOS transistor M4 is connected to a source of the fifth MOS transistor M5, a source of the sixth MOS transistor M6 is connected to an inverting input terminal of the third operational amplifier OP3 and one end of the second resistor R2, a gate of the sixth transistor M6 is connected to an output terminal of the third operational amplifier OP3, an input terminal of the third operational amplifier M3 is connected to a voltage source, the other terminal of the second positive-phase resistor R3 and one end of the third MOS transistor M8672, and the second positive-phase resistor R8672 of the third MOS transistor M3682 are grounded, and, The fourth MOS transistor M4 and the fifth MOS transistor M5 are both P-channel MOS transistors, and the sixth MOS transistor M6 is an N-channel MOS transistor.
In practical implementation, a reference voltage is input from the voltage source to the non-inverting input terminal of the third operational amplifier OP3, and the reference voltage is used as the first dimming voltage in the present embodiment; when the first MOS transistor M1 is turned on, the corresponding second MOS transistor M2 and the corresponding third MOS transistor M3 are connected to the circuit, and at this time, the voltage output unit 430 multiplies the difference between the sampling voltage and the preset voltage by a preset coefficient, and then adds the difference to the current first dimming voltage to obtain a second dimming voltage, which is output to the constant current module 500, where correspondingly, the preset coefficient in this embodiment is the number ratio of the third MOS transistor M3 to the second MOS transistor M2; when the first MOS transistor M1 is turned off, which is equivalent to the second MOS transistor M2 and the third MOS transistor M3 are not connected, the voltage output unit 430 still uses the current first dimming voltage as the input voltage of the constant current module 500, and the current of the LED string 200 is not changed.
If the voltage at the non-inverting input terminal of the third operational amplifier OP3 is VREF1, the sampling voltage received by the first operational amplifier OP1 is VSEN, the preset voltage is VREF0, the input voltage received by the constant current module 500 is VREF, the second dimming voltage is VREF2, and the preset coefficient is M; when the first switching tube is in an off state in the normal state, the input voltage VREF received by the constant current module 500 is equal to VREF 2; when the sampling voltage is greater than the preset voltage, indicating that the voltage of the utility power network is increased, the first MOS transistor M1 is turned on, and at this time, the input voltage received by the constant current module 500 is increased, that is, VREF is (VSEN-VREF0) × M (R3/R1) + VREF1, where R3 is a resistance value of the third resistor R3, R1 is a resistance value of the first resistor R1, and M is a preset coefficient, and if the sampling voltage is not greater than the preset voltage, indicating that the voltage of the utility power network is not increased, the first MOS transistor M1 is kept in a disconnected state, and at this time, the input voltage of the constant current module 500 is not changed, that is, VREF is VREF 1; in this embodiment, whether the voltage of the mains line network is increased is detected according to the sampled voltage of the negative terminal of the LED light string 200, so as to determine whether to increase the constant current of the LED light string 200 according to the sampled voltage, thereby ensuring that the light emitting efficiency of the LED light string 200 is improved when the voltage of the mains line network is increased.
Further, the voltage sampling module 300 includes a fourth resistor R4 and a fifth resistor R5; one end of the fourth resistor R4 is connected to the output end of the LED light string 200, the other end of the fourth resistor R4 is connected to the non-inverting input end of the first operational amplifier OP1 and one end of the fifth resistor R5, and the other end of the fifth resistor R5 is grounded; in this embodiment, the fifth resistor R5 and the fifth resistor R5 are voltage dividing resistors, and voltage dividing and sampling are performed on the voltage signal at the output end of the LED light string 200 through the fourth resistor R4 and the fifth resistor R5 to obtain a sampling voltage, so as to subsequently determine whether the voltage of the current utility power network is increased, where the corresponding sampling voltage VSEN is R5/(R4+ R5) × VOUT; VOUT is a voltage signal at the output terminal of the LED string 200, R5 is a resistance of the fifth resistor R5, and R4 is a resistance of the fourth resistor R4.
Further, in the present embodiment, the voltage maintaining module 600 includes a third resistor R3 and a first capacitor C1, one end of the third resistor R3 is connected to the source of the fifth MOS transistor M5, one end of the first capacitor C1 and the constant current module 500, the other end of the third resistor R3 is grounded, and the other end of the first capacitor C1 is grounded, in the present embodiment, the voltage maintaining module 600 formed by the third resistor R3 and the first capacitor C1 stores the peak voltage of the first dimming voltage or the second dimming voltage, that is, the peak voltage of the input voltage of the constant current module 500, so as to maintain the LED light string 200 without stroboflash.
Further, the power supply module 700 includes a zener diode ZD1, a sixth resistor R6, and a second capacitor C2, and the constant current module 500 includes a fourth operational amplifier OP4, a seventh MOS transistor M7, and a seventh resistor R7; the anode of the zener diode ZD1 is grounded, the cathode of the zener diode ZD1 is connected to one end of the sixth resistor R6 and one end of the second capacitor C2, the other end of the sixth resistor R6 is connected to the output end of the rectifier bridge 100, and the other end of the second capacitor C2 is grounded; a non-inverting input end of the fourth operational amplifier OP4 is connected to a source of the fifth MOS transistor M5, a source of the third MOS transistor M3, one end of the third resistor R3 and one end of the first capacitor C1, an inverting input end of the fourth operational amplifier OP4 is connected to a source of the seventh MOS transistor M7 and one end of the seventh resistor R7, the other end of the seventh resistor R7 is grounded, a gate of the seventh MOS transistor M7 is connected to an output end of the fourth operational amplifier OP4, and a drain of the seventh MOS transistor M7 is connected to an output end of the LED light string 200; due to the clamping of the fourth operational amplifier OP4 in the constant current module 500, in order to maintain the normal operation of the fourth operational amplifier OP4, the seventh MOS transistor M7 is enabled to operate normally to maintain the constant current operation of the constant current module 500, and the supply voltage VDD required by the fourth operational amplifier OP4 cannot be powered down, so that the line voltage output by the rectifier bridge 100 is clamped by the sixth resistor R6 and the zener diode ZD1 to generate the supply voltage, and the voltage is stored by the second capacitor C2, thereby ensuring that the supply voltage is not powered down to maintain the normal operation of the voltage sampling module 300, the sampling processing module 400 and the constant current module 500.
Further, referring to fig. 6, in the second embodiment of the present invention, the voltage maintaining module 600 includes an eighth resistor R8 and a third capacitor C3, wherein one end of the eighth resistor R8 and one end of the third capacitor C3 are both connected to the output end of the fourth operational amplifier OP4, the other end of the eighth resistor R8 is grounded, and the other end of the third capacitor C3 is grounded; different from the first embodiment, in the present embodiment, the voltage maintaining module 600 is connected to the output of the fourth operational amplifier OP4 in the constant current module 500, and is configured to store the gate voltage of the seventh MOS transistor M7 corresponding to the input voltage of the constant current module 500, in the present embodiment, the peak voltage of the first dimming voltage or the second dimming voltage sets the constant current of the LED light string 200 through the constant current module 500, and the voltage maintaining module 600 maintains the gate voltage of the seventh MOS transistor M7, so as to maintain the LED light string 200 without stroboflash. The line voltage output by the rectifier bridge 100 is clamped by the sixth resistor R6 and the zener diode ZD1 to generate a supply voltage, and no capacitor is needed to maintain, so that no capacitor is provided in the corresponding power supply module 700 in this embodiment, that is, only the zener diode ZD1 and the sixth resistor R6 are provided in the power supply module 700 in this embodiment, power is taken at the negative terminal of the LED string 200, when the voltage is high, the fourth operational amplifier OP4 normally operates, and when the voltage is low, the fourth operational amplifier OP4 does not operate, and the gate voltage of the seventh MOS transistor is maintained by the third capacitor C3, so as to ensure the constant current state of the constant current module 500.
Based on the above constant current LED driving circuit, please refer to fig. 7, the present invention further provides a driving method of the constant current LED driving circuit, which specifically includes the following steps:
s100, a voltage sampling module samples a voltage signal at the output end of the LED lamp string and outputs the sampled voltage to a sampling processing module;
s200, when the sampling processing module judges that the sampling voltage is greater than the preset voltage, the current first dimming voltage is increased to a second dimming voltage and then the second dimming voltage is output to the constant current module;
and S300, the constant current module sets the constant current flowing through the LED lamp string according to the second dimming voltage.
Based on the constant current LED driving circuit, the invention also provides a constant current LED driving device, which includes a PCB board, wherein the PCB board is provided with the constant current LED driving circuit, and the constant current LED driving circuit is not described herein again because the constant current LED driving circuit is described in detail above.
In summary, the present invention provides a constant current LED driving circuit, a device and a driving method thereof, where the constant current LED driving circuit includes an LED string, a voltage sampling module, a sampling processing module and a constant current module; the voltage sampling module is connected with the output end of the LED lamp string and the sampling processing module, the sampling processing module is connected with the constant current module, and the constant current module is also connected with the output end of the LED lamp string; the voltage sampling module is used for outputting sampling voltage to the sampling processing module according to the voltage signal at the output end of the LED lamp string; the sampling processing module is used for increasing the current first dimming voltage to a second dimming voltage and outputting the second dimming voltage to the constant current module when judging that the sampling voltage is greater than a preset voltage; the constant current module is used for setting constant current flowing through the LED lamp string according to the second dimming voltage, so that the luminous efficiency of the LED lamp string is improved when the voltage of a mains supply network is increased.
It should be understood that equivalents and modifications of the technical solution and inventive concept thereof may occur to those skilled in the art, and all such modifications and alterations should fall within the scope of the appended claims.

Claims (10)

1. A constant current LED drive circuit is characterized by comprising an LED lamp string, a voltage sampling module, a sampling processing module and a constant current module; the voltage sampling module is connected with the output end of the LED lamp string and the sampling processing module, the sampling processing module is connected with the constant current module, and the constant current module is also connected with the output end of the LED lamp string; the voltage sampling module is used for outputting sampling voltage to the sampling processing module according to the voltage signal at the output end of the LED lamp string; the sampling processing module is used for increasing the current first dimming voltage to a second dimming voltage and outputting the second dimming voltage to the constant current module when judging that the sampling voltage is greater than a preset voltage; the constant current module is used for setting constant current flowing through the LED lamp string according to the second dimming voltage.
2. The constant-current LED driving circuit according to claim 1, further comprising a voltage maintaining module, wherein the voltage maintaining module is respectively connected to the sampling processing module and the constant-current module; the voltage maintaining module is used for storing the peak voltage of the first dimming voltage or the second dimming voltage.
3. The constant-current LED driving circuit according to claim 1, wherein the sampling processing module is specifically configured to, when determining that the sampling voltage is greater than a preset voltage, multiply a difference between the sampling voltage and the preset voltage by a preset coefficient, add the difference to the current first dimming voltage, and output the second dimming voltage to the constant current module.
4. The constant-current LED driving circuit according to claim 3, wherein the sampling processing module comprises a comparison unit, a switch unit and a voltage output unit; the comparison unit is respectively connected with the voltage sampling module and the switch unit, the switch unit is connected with the voltage output unit, and the voltage output unit is also connected with the constant current module; the comparison unit is used for controlling the switch unit to be conducted when judging that the sampling voltage is greater than the preset voltage; the voltage output unit is used for multiplying a difference value between the sampling voltage and the preset voltage by a preset coefficient when the switch unit is switched on, adding the difference value to the current first dimming voltage, and outputting the second dimming voltage to the constant current module.
5. The constant-current LED driving circuit according to claim 4, wherein the comparison unit comprises a first operational amplifier, a second operational amplifier and a first resistor; the positive phase input end of the first operational amplifier is connected with the voltage sampling module, the negative phase input end of the first operational amplifier is connected with the switch unit and one end of the first resistor, the output end of the first operational amplifier is connected with the switch unit, the other end of the first resistor is connected with the output end of the second operational amplifier and the negative phase input end of the second operational amplifier, and the positive phase input end of the second operational amplifier is connected with the voltage source.
6. The constant-current LED driving circuit according to claim 5, wherein the switching unit comprises a first MOS transistor, a gate of the first MOS transistor is connected to the output terminal of the first operational amplifier, a source of the first MOS transistor is connected to the inverting input terminal of the first operational amplifier and one end of the first resistor, and a drain of the first MOS transistor is connected to the voltage output unit.
7. The constant-current LED driving circuit according to claim 6, wherein the voltage output unit comprises a second MOS transistor, a third MOS transistor, a fourth MOS transistor, a fifth MOS transistor, a sixth MOS transistor, a second resistor, a third resistor and a third operational amplifier; the grid electrode of the second MOS tube is connected with the grid electrode of the third MOS tube, the drain electrode of the second MOS tube and the drain electrode of the first MOS tube, the source electrode of the second MOS tube is connected with the source electrode of the third MOS tube, the drain electrode of the third MOS tube is connected with the drain electrode of the fifth MOS tube, one end of a third resistor and the constant current module, the grid electrode of the fourth MOS tube is connected with the grid electrode of the fifth MOS tube, the drain electrode of the fourth MOS tube and the drain electrode of the sixth MOS tube, the source electrode of the fourth MOS tube is connected with the source electrode of the fifth MOS tube, the source electrode of the sixth MOS tube is connected with the inverting input end of the third operational amplifier and one end of the second resistor, the grid electrode of the sixth MOS tube is connected with the output end of the third operational amplifier, the positive phase input end of the third operational amplifier is connected with a voltage source, and the other end of the second resistor and the other end of the third resistor are both grounded.
8. The constant-current LED driving circuit according to claim 5, wherein the voltage sampling module comprises a fourth resistor and a fifth resistor; one end of the fourth resistor is connected with the output end of the LED lamp string, the other end of the fourth resistor is connected with the positive phase input end of the first operational amplifier and one end of the fifth resistor, and the other end of the fifth resistor is grounded.
9. A driving method of the constant current LED driving circuit according to any one of claims 1 to 8, comprising:
the voltage sampling module samples a voltage signal at the output end of the LED lamp string and outputs the sampled voltage to the sampling processing module;
when the sampling processing module judges that the sampling voltage is greater than the preset voltage, the current first dimming voltage is increased to a second dimming voltage and then the second dimming voltage is output to the constant current module;
and the constant current module sets the constant current flowing through the LED lamp string according to the second dimming voltage.
10. A constant-current LED driving device comprises a PCB board, and is characterized in that the PCB board is provided with the constant-current LED driving circuit according to any one of claims 1-8.
CN202011050315.9A 2020-09-29 2020-09-29 Constant-current LED driving circuit, device and driving method thereof Active CN112188684B (en)

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CN103917016A (en) * 2014-03-10 2014-07-09 陕西亚成微电子股份有限公司 High-voltage linear power current compensating circuit
CN104540287A (en) * 2012-10-30 2015-04-22 四川新力光源股份有限公司 LED dimming driving circuit
CN108882461A (en) * 2018-07-27 2018-11-23 深圳市明微电子股份有限公司 A kind of adjusting control circuit and system
CN109152157A (en) * 2018-10-26 2019-01-04 深圳市晟碟半导体有限公司 A kind of twin voltage LED drive circuit, driving device and driving method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104540287A (en) * 2012-10-30 2015-04-22 四川新力光源股份有限公司 LED dimming driving circuit
CN103917016A (en) * 2014-03-10 2014-07-09 陕西亚成微电子股份有限公司 High-voltage linear power current compensating circuit
CN108882461A (en) * 2018-07-27 2018-11-23 深圳市明微电子股份有限公司 A kind of adjusting control circuit and system
CN109152157A (en) * 2018-10-26 2019-01-04 深圳市晟碟半导体有限公司 A kind of twin voltage LED drive circuit, driving device and driving method

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