CN112702815A - Switch buck type LED constant current control circuit, system and method - Google Patents
Switch buck type LED constant current control circuit, system and method Download PDFInfo
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Abstract
The invention provides a switching step-down LED constant current control circuit, a system and a method, wherein the switching step-down LED constant current control circuit, the system and the method comprise the following steps: an average current comparison module for comparing the current detection sampling signal with an average reference; a peak current comparison module for comparing the current detection sampling signal with a peak reference; the self-adaptive clock generation module generates a turn-off finishing signal; a PWM logic control module for generating logic control signals; and a driving module. The current detection sampling signal is conducted within the same time when rising to the average reference and exceeding the average reference, and then the power switch tube is turned off; and if the current detection sampling signal is larger than the peak value reference, the power switch tube is turned off in advance, meanwhile, the turn-off reference signal is adjusted, and when the preset charging signal is larger than the turn-off reference signal, the power switch tube is turned on again and starts the next new PWM period. The invention can realize smaller current ripple and high-precision output current, and has better linear regulation rate and load regulation rate.
Description
Technical Field
The invention relates to the field of LED constant current control, in particular to a switching buck type LED constant current control circuit, system and method.
Background
The traditional switch buck LED controller adopts a peak current detection mode with fixed clock frequency, is influenced by inductive ripples, and has poor current precision on an output LED light-emitting unit; and when external power supply and load change, need adjust inductance value to guarantee that output inductor current work in continuous conduction mode, the selection of inductance value influences the precision and the ripple of LED electric current.
In a traditional LED control scheme, after a power supply VDD is electrified, a current detection sampling signal is compared with a reference voltage to generate a charging end signal, the charging end signal and a clock signal are controlled by a PWM logic to generate a logic control signal, and then the logic control signal is driven by an output front stage to generate a grid electrode driving signal of an external power device, so that the power device is controlled to be turned on and off to control the current (current peak value and ripple) on an external LED light-emitting unit.
The driving sequence of the continuous conduction mode is shown in fig. 1, after the power supply VDD is powered on, the internal driving circuit starts to work, the internal PWM logic controls the external inductor to periodically charge and discharge, and the corresponding current I _ LED flows through the external LED light emitting unit. Amplifying one PWM period, and the time sequence is shown in FIG. 2: in a fixed PWM period (for example, the fixed clock period may be set to 7us), the gate driving signal DRV is first set to a logic high level, the power device is turned on, the inductor current is charged, the level of the feedback signal CS slowly rises to the reference voltage VREF, when the charge end signal DISCHARGE is detected to be high, DRV becomes a logic low level, the power device is turned off, and the inductor current is discharged.
In a continuous conduction mode: the peak value of the output current I _ LED is: and Ipeak is VREF/R _ sense, wherein Ipeak is the peak current, and R _ sense is the resistance value of the sampling resistor. The ripple of the I _ LED is: Δ i ═ VLEDToff/L, wherein VLEDL is inductance and Toff is fixed discharge time, which is the voltage drop across the LED lighting unit. Due to the buck LED controller, the fixed discharge time Toff is determined by the voltage drop V across the LED lighting unitLEDThe input voltage Vin and the PWM period T determine: toff ═ 1-VLED/Vin)*TTherefore: Δ i ═ VLED*(1-VLEDVin) T/L, the accuracy of the output current I _ LED is affected by the peak value Ipeak and the ripple Δ I.
In order to ensure constant output current, a proper inductance value is adopted to ensure that the loop works in a continuous conduction mode, and the calculation formula of the minimum inductance value is as follows: l1>VLED*(1-VLEDand/Vin) T R _ sense/VREF, where Δ i is equal to Ipeak is equal to VREF/R _ sense, and the output operates in the critical continuous conduction mode. To achieve better current accuracy, it is necessary to ensure that the ripple of the inductor current is small, for example, Δ i is set to 40% Ipeak, and the inductance is increased to: l1>2.5*VLED*(1-VLEDV Vin) T R sense/VREF. If the external inductance is set to be small, the discontinuous conduction mode is easy to enter, and the ripple and the precision of the I _ LED are affected at the moment.
The conventional LED control loop has a fixed frequency, and in order to ensure the accuracy of the output current, it is necessary to ensure that the controller operates in a continuous conduction mode. When the external inductor is small or the set output I _ LED current is small, loads such as Vin, an LED light-emitting unit and the like are changed, the mode is easy to enter a discontinuous conduction mode, and the output current precision is affected. Therefore, how to ensure that the LED control loop is not affected by the input voltage and the LED light emitting unit, etc., to improve the output current accuracy and reduce the output ripple has become one of the problems to be solved by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a switching buck LED constant current control circuit, system and method, which are used to solve the problem of low accuracy of the output current of the LED control loop in the prior art.
In order to achieve the above and other related objects, the present invention provides a switching buck LED constant current control circuit, which at least includes:
the device comprises an average current comparison module, a peak current comparison module, a self-adaptive clock generation module, a PWM logic control module and a driving module;
the average current comparison module receives a current detection sampling signal of the buck LED circuit, and is used for comparing the current detection sampling signal with an average reference to obtain a first comparison result;
the peak current comparison module receives the current detection sampling signal, is used for comparing the current detection sampling signal with a peak reference, and obtains a second comparison result; the average baseline is less than the peak baseline;
the self-adaptive clock generating module receives the inverted logic signal of the second comparison result, adjusts the level of a turn-off reference signal and generates a corresponding turn-off finishing signal;
the PWM logic control module is connected with the average current comparison module, the peak current comparison module and the output end of the self-adaptive clock generation module, adjusts the on-time of a logic control signal based on the first comparison result and the second comparison result, and adjusts the off-time of the logic control signal based on the off-end signal so as to realize the constant current output of the buck LED circuit and reduce the output current ripple;
the driving module is connected to the output end of the PWM logic control module and drives a power switch tube in the buck LED circuit to be switched on or switched off based on the logic control signal.
Optionally, the adaptive clock generating module includes a turn-off reference signal control unit and a turn-off end signal generating unit;
the turn-off reference signal control unit receives an inverted logic signal of the second comparison result, and generates a pull-down control signal when the current detection sampling signal is greater than the peak reference; generating a pull-up control signal when the current detection sampling signal is less than the peak reference;
the turn-off end signal generating unit receives the pull-down control signal and the pull-up control signal to adjust the magnitude of a turn-off reference signal, the pull-down control signal controls the turn-off reference signal to discharge to reduce the level, and the pull-up control signal controls the turn-off reference signal to charge to increase the level; and meanwhile, comparing a preset charging signal with the turn-off reference signal, and generating the turn-off end signal when the preset charging signal is greater than the turn-off reference signal.
More optionally, the turn-off reference signal control unit includes a first inverter, a first nand gate, a second nand gate, a third nand gate, a fourth nand gate, and a second inverter;
the input end of the first NAND gate is respectively connected with the inverted logic signal of the second comparison result and the output end of the second NAND gate; the input end of the first inverter receives an inverted logic signal of the second comparison result; the input end of the second NAND gate is respectively connected with the first inverter and the output end of the first NAND gate; the input end of the third NAND gate is respectively connected with the input end of the first NAND gate and a pulse signal, the input end of the second inverter is connected with the output end of the third NAND gate, and the output end of the second inverter outputs the pull-down control signal; the input end of the fourth NAND gate is respectively connected with the input end of the second NAND gate and the pulse signal, and the output end of the fourth NAND gate outputs the pull-up control signal.
More optionally, the turn-off end signal generating unit includes a first current source, a pull-up tube, a pull-down tube, a second current source, a first charging capacitor, a first switch, a third current source, a second charging capacitor, and a comparator;
the first current source, the pull-up tube, the pull-down tube and the second current source are sequentially connected in series between a power supply and the ground, a connection node of the pull-up tube and the pull-down tube outputs the turn-off reference signal, a control end of the pull-up tube is connected with the pull-up control signal, and a control end of the pull-down tube is connected with the pull-down control signal; one end of the first charging capacitor is connected with the turn-off reference signal, and the other end of the first charging capacitor is grounded; one end of the first switch is connected with the turn-off reference signal, and the other end of the first switch is grounded after being connected with bias voltage;
one end of the third current source is connected with a power supply, and the other end of the third current source is connected with the second charging capacitor; the other end of the second charging capacitor is grounded; a connection node of the third current source and the second charging capacitor outputs the preset charging signal;
the input end of the comparator is respectively connected with the turn-off reference signal and the preset charging signal, and outputs the turn-off finishing signal.
More optionally, the PWM logic control module includes a conduction signal generating unit and a logic control signal generating unit;
the conducting signal generating unit receives the first comparison result and the second comparison result, and outputs an effective conducting signal at a first time when the current detection sampling signal rises to the average reference and a first time when the current detection sampling signal exceeds the average reference, wherein if the current detection sampling signal is greater than the peak reference, the conducting signal is directly invalid;
the logic control signal generating unit is connected with the conducting signal generating unit and the output end of the self-adaptive clock generating module, and generates the logic control signal based on the conducting signal and the turn-off finishing signal.
More optionally, the conducting signal generating unit includes an oscillator, an adder, and a subtractor;
the adder is connected with the oscillator and the output end of the average current comparison module, and when the current detection sampling signal rises to the average reference, the adder carries out addition operation to obtain a counting result corresponding to the first time;
the subtracter is connected with the oscillator, the adder and the output end of the peak current comparison module, and is used for subtracting the counting result of the adder, and if the current detection sampling signal is smaller than the peak reference, the conducting signal is controlled to be invalid when the subtraction result is zero; and if the current detection sampling signal is larger than the peak value reference, directly controlling the conduction signal to fail.
Optionally, the switching buck LED constant current control circuit further includes a short-circuit protection module and/or a dimming module; the short-circuit protection module receives the current detection sampling signal, compares the current detection sampling signal with a short-circuit protection reference, and turns off the power switch tube when the current detection sampling signal is greater than the short-circuit protection reference, wherein the short-circuit protection reference is greater than the peak value reference; the dimming module receives a dimming control signal and adjusts values of the average reference and the peak reference based on the dimming control signal.
In order to achieve the above and other related objects, the present invention provides a switching buck LED constant current control system, which at least includes:
according to the switch buck LED constant current control circuit and the buck LED circuit, the switch buck LED constant current control circuit receives the current detection sampling signal of the buck LED circuit and outputs the driving signal of the buck LED circuit.
Optionally, the buck LED circuit includes an LED light emitting module, an inductor, a freewheeling diode, a power switching tube, and a sampling module;
the anode of the LED light-emitting module is connected with an input power supply, and the cathode of the LED light-emitting module is connected with one end of the inductor; the other end of the inductor is connected with the anode of the freewheeling diode; the negative electrode of the freewheeling diode is connected with the input power supply; one end of the power switch tube is connected with the anode of the freewheeling diode, the other end of the power switch tube is connected with the sampling module and then grounded, and the control end of the power switch tube is connected with the driving signal; and the current detection sampling signal is output by the connection node of the power switch tube and the sampling module.
In order to achieve the above and other related objects, the present invention provides a constant current control method for a switching buck LED, the constant current control method at least comprising:
monitoring a current detection sampling signal of the buck LED circuit, and outputting an effective conduction signal in a first time when the current detection sampling signal rises to the average reference and a first time when the current detection sampling signal exceeds the average reference in a period, wherein the conduction signal fails; if the current detection sampling signal is larger than the peak value reference, the conducting signal is invalid;
decreasing a turn-off reference signal when the current detection sampling signal is greater than the peak reference, increasing the turn-off reference signal when the current detection sampling signal is less than the peak reference, comparing a preset charging signal with the turn-off reference signal, and generating the turn-off end signal when the preset charging signal is greater than the turn-off reference signal;
adjusting a driving signal of the power switch tube based on the conducting signal and the turn-off finishing signal to realize constant current output and control ripple waves of output current;
wherein the average baseline is less than the peak baseline.
Optionally, the method for obtaining the turn-on signal includes:
when the current detection sampling signal is smaller than the average reference, performing addition operation to obtain a counting result corresponding to the first time;
subtracting the counting result, and if the current detection sampling signal is smaller than the peak value reference, controlling the conducting signal to be invalid when the subtraction operation result is zero; and if the current detection sampling signal is larger than the peak value reference, directly controlling the conduction signal to fail.
Optionally, the power switch tube in the buck LED circuit is controlled to be turned on when the turn-on signal is valid, the power switch tube is controlled to be turned off when the turn-on signal is invalid, and the power switch tube is controlled to be turned on again when the turn-off end signal is valid.
Optionally, the switching buck LED constant current control method further includes: and monitoring the current detection sampling signal, and turning off the power switch tube when the current detection sampling signal is larger than a short-circuit protection reference, wherein the short-circuit protection reference is larger than the peak value reference.
Optionally, the switching buck LED constant current control method further includes: and adjusting the values of the average reference and the peak reference based on a dimming control signal to realize dimming control.
As described above, the switching buck-type LED constant current control circuit, system and method of the present invention have the following advantages:
according to the switching buck LED constant current control circuit, the switching buck LED constant current control system and the switching buck LED constant current control method, the PWM clock period is automatically adjusted through an internal circuit, the conduction time is controlled by the counter, and the constant current control mode of average current detection and peak current detection is adopted, so that high accuracy of small current ripples and output current is finally achieved, and the switching buck LED constant current control circuit has good linear regulation rate and load regulation rate.
The switching buck LED constant current control circuit, the system and the method adopt self-adaptive adjustment, can realize very small LED output current, and can be widely applied to the field of electronic circuits.
Drawings
FIG. 1 is a schematic diagram of a driving timing diagram of a continuous conduction mode.
FIG. 2 is an enlarged schematic diagram of a PWM cycle of a continuous conduction mode driving sequence.
Fig. 3 is a schematic structural diagram of the switching buck LED constant current control circuit according to the present invention.
Fig. 4 is a schematic structural diagram of the turn-off reference signal control unit according to the present invention.
Fig. 5 is a schematic structural diagram of the shutdown end signal generating unit according to the present invention.
Fig. 6 is a schematic structural diagram of a turn-on signal generating unit according to the present invention.
Fig. 7 is a schematic diagram showing another structure of the switching buck LED constant current control circuit according to the present invention.
Fig. 8 is a schematic diagram of the switching buck LED constant current control system according to the present invention.
FIG. 9 is a timing diagram illustrating the generation of the turn-on time according to the present invention.
FIG. 10 is a timing diagram illustrating the turn-down of the turn-off reference signal according to the present invention.
FIG. 11 is a timing diagram illustrating the up-regulation of the turn-off reference signal according to the present invention.
FIG. 12 is a timing diagram illustrating the generation of the shutdown completion signal according to the present invention.
Fig. 13 is an input/output timing diagram of the switching buck LED constant current control circuit, system and method of the present invention.
FIG. 14 is a timing diagram of the discontinuous conduction mode before the output current is stabilized according to the present invention.
FIG. 15 is a timing diagram of the continuous conduction mode after the output current is stabilized according to the present invention.
Description of the element reference numerals
1-switch buck type LED constant current control system
11 switch step-down LED constant current control circuit
111 average current comparing module
112 peak current comparison module
113 self-adaptive clock generating module
113a turn-off reference signal control unit
113b shutdown end signal generation unit
114 PWM logic control module
114a turn-on signal generating unit
114a1 oscillator
114a2 adder
114a3 subtracter
115 drive module
116 short-circuit protection module
117 dimming module
117a digital-to-analog conversion unit
12 step-down LED circuit
121 LED light emitting module
122 sampling module
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 3 to fig. 15. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Example one
As shown in fig. 3, the present embodiment provides a switching buck LED constant current control circuit 11, where the switching buck LED constant current control circuit 11 includes:
an average current comparison module 111, a peak current comparison module 112, an adaptive clock generation module 113, a PWM logic control module 114, and a driving module 115.
As shown in fig. 3, the average current comparing module 111 receives a current detection sampling signal Vcs of the buck LED circuit, and is configured to compare the current detection sampling signal Vcs with an average reference Vref1, and obtain a first comparison result Cp 1.
Specifically, in this embodiment, a non-inverting input terminal of the average current comparing module 111 is connected to the current detection sampling signal Vcs, and an inverting input terminal thereof is connected to the average reference Vref 1; a low level is output when the current detection sampling signal Vcs is less than the average reference Vref1, and a high level is output when the current detection sampling signal Vcs is greater than the average reference Vref 1. In practical use, the inverter can be added to adjust the corresponding relationship between the input signal and the polarity of the input terminal, which is not limited to this embodiment.
As shown in fig. 3, the peak current comparing module 112 receives the current detection sampling signal Vcs, and is configured to compare the current detection sampling signal Vcs with a peak reference Vref2, and obtain a second comparison result Cp 2; the average reference Vref1 is less than the peak reference Vref 2.
Specifically, in this embodiment, the positive input terminal of the peak current comparing module 112 is connected to the current detection sampling signal Vcs, and the negative input terminal thereof is connected to the peak reference Vref 2; a low level is output when the current detection sampling signal Vcs is less than the peak reference Vref2, and a high level is output when the current detection sampling signal Vcs is greater than the peak reference Vref 2. In practical use, the inverter can be added to adjust the corresponding relationship between the input signal and the polarity of the input terminal, which is not limited to this embodiment.
As shown in fig. 3, the adaptive clock generation module 113 receives the inverted logic signal LS of the second comparison result Cp2 to adjust the turn-Off reference signal level Ref _ Off and generates a corresponding turn-Off end signal Off.
Specifically, the adaptive clock generating module 113 includes a turn-off reference signal control unit 113a and a turn-off end signal generating unit 113 b. The off-reference signal control unit 113a receives the inverted logic signal LS of the second comparison result Cp2, and when the current detection sampling signal Vcs is greater than the peak reference Vref2, the inverted logic signal LS of the second comparison result Cp2 outputs a falling edge to generate an effective pull-Down control signal Down, which generates a one-time high-level pulse signal; when the current detection sampling signal Vcs is less than the peak reference Vref2, the inverted logic signal LS of the second comparison result Cp2 remains high, generating an active pull-Up control signal Up, which generates a low level pulse signal once. The turn-Off end signal generating unit 113b receives the pull-Down control signal Down and the pull-Up control signal Up to adjust the magnitude of a turn-Off reference signal Ref _ Off, compares a preset charging signal RC with the turn-Off reference signal Ref _ Off, and generates the turn-Off end signal Off when the preset charging signal RC is greater than the turn-Off reference signal Ref _ Off.
More specifically, as shown in fig. 4, the turn-off reference signal control unit 113a includes a first inverter not1, a first nand gate nand1, a second nand gate nand2, a third nand gate nand3, a fourth nand gate nand4, and a second inverter not 2. The input ends of the first nand gate nand1 are respectively connected with the inverted logic signal LS of the second comparison result Cp2 and the output end of the second nand gate nand 2; an input terminal of the first inverter not1 receives an inverted logic signal LS of the second comparison result Cp 2; the input end of the second nand gate nand2 is respectively connected with the output ends of the first inverter not1 and the first nand gate nand 1; the input end of the third nand gate nand3 is respectively connected to the input end of the first nand gate nand1 and a pulse signal pulse (when the driving signal Drv output by the driving module 115 becomes low, the pulse signal pulse is generated; in this embodiment, the pulse width of the pulse signal pulse is set to 300ns, and the pulse signal pulse is generated by the PWM logic control module 114. in actual use, the pulse width and the source of the pulse signal pulse can be set as required, which is not limited by this embodiment), the input end of the second inverter not2 is connected to the output end of the third nand gate nand3, and the output end outputs the pull-Down control signal Down; the input end of the fourth nand gate nand4 is connected to the input end of the second nand gate nand2 and the pulse signal pulse, and the output end outputs the pull-Up control signal Up. When the current detection sampling signal Vcs is greater than the peak reference Vref2, the second comparison result Cp2 is at a high level, the inverted logic signal LS of the second comparison result Cp2 is at a low level, the pull-Down control signal Down is a high-level pulse, the pull-Up control signal Up is also at a high level, at this time, the pull-Down control signal Down is active, and the turn-Off reference signal Ref _ Off discharges a reduced level during the high-level pulse; when the current detection sampling signal Vcs is smaller than the peak reference Vref2, the second comparison result Cp2 is kept at a low level, the inverted logic signal LS of the second comparison result Cp2 is kept at a high level, the pull-Down control signal Down is at a low level, and the pull-Up control signal Up is a low-level pulse, and at this time, the pull-Up control signal Up is active and the Off reference signal Ref _ Off is electrically boosted for the low-level pulse time.
More specifically, as shown in fig. 5, the turn-off end signal generating unit 113b includes a first current source IBP1, a pull-up tube MP, a pull-down tube MN, a second current source IBN1, a first charging capacitor C1, a first switch S1, a third current source IBP2, a second charging capacitor C2, and a comparator COMP. One end of the first current source IBP1 is connected with a power supply VDD, and the other end is connected with the source electrode of the pull-up tube MP; the grid end of the pull-Up tube MP is connected with the pull-Up control signal Up, and the drain electrode of the pull-down tube MN is connected with the drain electrode of the pull-Up tube MP; the grid end of the pull-Down tube MN is connected with the pull-Down control signal Down, and the drain electrode of the pull-Down tube MN is connected with one end of the second current source IBN 1; the other terminal of the second current source IBN1 is connected to ground. One end of the first charging capacitor C1 is connected to the drains of the pull-up tube MP and the pull-down tube MN, and the other end is grounded. One end of the first switch S1 is connected to the drains of the pull-up tube MP and the pull-down tube MN, and the other end is connected to the bias voltage Vbias and then grounded. The drains of the pull-up tube MP and the pull-down tube MN output a turn-Off reference signal Ref _ Off. One end of the third current source is connected with a power supply, and the other end of the third current source is connected with the second charging capacitor; the other end of the second charging capacitor is grounded; one end of the third current source IBP2 is connected with a power supply VDD, and the other end is connected with the upper plate of the second charging capacitor C2; the lower plate of the second charging capacitor C2 is grounded; the connection node of the third current source IBP2 and the second charging capacitor C2 outputs the preset charging signal RC. The input end of the comparator COMP is respectively connected to the turn-Off reference signal Ref _ Off and the preset charging signal RC, and outputs the turn-Off end signal Off, when the preset charging signal RC is greater than the turn-Off reference signal Ref _ Off, the turn-Off end signal Off is valid, a high-level pulse is generated, the PWM cycle is declared to be ended, a next new PWM cycle is entered, and the power switching tube is turned on again. In this embodiment, an inverting input terminal of the comparator COMP is connected to the turn-Off reference signal Ref _ Off, and a non-inverting input terminal thereof is connected to the preset charging signal RC. In practical use, the inverter can be added to adjust the corresponding relationship between the input signal and the polarity of the input terminal, which is not limited to this embodiment.
In this embodiment, the first current source IBP1 and the second current source IBN2 are uA class currents, and the first charging capacitor C1 is a pF class capacitor.
As shown in fig. 3, the PWM logic control module 114 is connected to the output terminals of the average current comparing module 111, the peak current comparing module 112 and the adaptive clock generating module 113, adjusts the on-time of the logic control signal Predrv based on the first comparison result Cp1 and the second comparison result Cp2, and adjusts the Off-time of the logic control signal Predrv based on the Off-end signal Off, so as to achieve the constant current output of the buck LED circuit and reduce the output current ripple.
Specifically, the PWM logic control module 114 includes a turn-on signal generating unit 114a and a logic control signal generating unit (not shown). The On signal generating unit 114a receives the first comparison result Cp1 and the second comparison result Cp2, outputs a valid On signal (within a period, the upper and lower deviation values of the current detection sampling signal Vcs and the average reference voltage Vref1 are equal) at a first time when the current detection sampling signal Vcs rises to the average reference Vref1 and a first time when the current detection sampling signal Vcs exceeds the average reference Vref1, and then the On signal On is disabled, and if the current detection sampling signal Vcs is greater than the peak reference Vref2, the On signal On is disabled in advance when the current detection sampling signal Vcs is greater than the peak reference Vref 2. The logic control signal generating unit is connected to the On signal generating unit 114a and the output end of the adaptive clock generating module 113, and generates the logic control signal Predrv based On the On signal On and the Off end signal Off.
More specifically, as shown in fig. 6, in the present embodiment, the turn-on signal generating unit 114a includes an oscillator 114a1, an adder 114a2 and a subtractor 114a 3. The oscillator 114a1 is used to generate a basic clock, which in this implementation has a frequency on the order of MHz. The adder 114a2 is connected to the oscillator 114a1 and the output end of the average current comparing module 111, the power switch tube starts to be turned on, when the current detection sampling signal Vcs gradually increases to the average reference Vref1, the adder 114a2 sequentially adds 1 from 0 to start to perform addition operation, and a counting result n is obtained, where the counting result n corresponds to a time when the current detection sampling signal Vcs is less than the average reference Vref1, that is, the first time. The subtractor 114a3 is connected to the output terminals of the oscillator 114a1, the adder 114a2 and the peak current comparison module 112, and subtracts the count result of the adder 114a2 from n by subtracting 1 one by one, and the current detection sampling signal Vcs continues to increase until the count result of the adder 114a2 gradually decreases from n to 0 again, so that the time when the current detection sampling signal Vcs is greater than the average reference Vref1 is also the first time. If the current detection sampling signal Vcs is always smaller than the peak reference Vref2, the On signal On is controlled to fail when the subtraction result is zero, and the On signal becomes a low level; with the increase of the current detection sampling signal Vcs, if the current detection sampling signal Vcs is larger than the peak reference Vref2, the subtraction operation is stopped, and when the current detection sampling signal Vcs is larger than the peak reference Vref2, the On signal On is directly controlled to be invalid. The output of the average current comparison module 111 controls the upper and lower deviation values of the current detection sampling signal Vcs and the average reference voltage Vref1 to be equal, so that constant current output is realized. The output of the peak current comparing module 112 controls the maximum On time of the On signal On, if the current detection sampling signal Vcs is higher than the peak reference Vref2, the output of the peak current comparing module 112 generates a high level pulse, the subtractor 114a3 stops working immediately, and the On signal On is changed to a logic low level after being ended in advance.
More specifically, the logic control signal generation unit receives the On signal On and the Off end signal Off and generates the logic control signal Predrv. When the On signal On is valid, the logic control signal Predrv controls the power switch tube in the buck LED circuit to be turned On, when the On signal On is invalid, the logic control signal Predrv controls the power switch tube to be turned Off, and when the Off end signal Off is valid, the logic control signal Predrv controls the power switch tube to be turned On again.
As shown in fig. 3, the driving module 115 is connected to the output end of the PWM logic control module 114, and generates a driving signal Drv based on the logic control signal Predrv, for driving the power switch tube in the buck LED circuit to turn on or off.
In this embodiment, the average current comparing module 111, the peak current comparing module 112, the adaptive clock generating module 113, the PWM logic control module 114, and the driving module 115 are integrated inside a chip, and in actual use, the positions of the modules may be set according to actual needs, which is not limited to this embodiment.
Example two
As shown in fig. 7, the present embodiment provides a switching buck LED constant current control circuit 11, which is different from the first embodiment in that other functional modules are added in the present embodiment.
As an implementation manner of the present invention, the switching buck LED constant current control circuit 11 further includes a short-circuit protection module 116. The Short-circuit protection module 116 receives the current detection sampling signal Vcs, compares the current detection sampling signal Vcs with a Short-circuit protection reference Vref3, and outputs a Short-circuit protection signal Short. And turning off the power switch tube when the current detection sampling signal Vcs is larger than the short-circuit protection reference Vref3, wherein the short-circuit protection reference Vref3 is larger than the peak reference Vref 2. In this embodiment, the non-inverting input terminal of the short-circuit protection module 116 is connected to the current detection sampling signal Vcs, and the inverting input terminal is connected to the short-circuit protection reference Vref 3.
As another implementation manner of the present invention, the switching buck LED constant current control circuit 11 further includes a dimming module 117, and the dimming module 117 receives a dimming control signal DIM and adjusts the values of the average reference Vref1 and the peak reference Vref2 based on the dimming control signal DIM. In this embodiment, the dimming module 117 includes a digital-to-analog conversion unit 117a, and the digital-to-analog conversion unit 117a performs digital-to-analog conversion on the dimming control signal DIM to adjust the values of the average reference Vref1 and the peak reference Vref2, so as to implement dimming control.
EXAMPLE III
As shown in fig. 8, the present embodiment provides a switching buck LED constant current control system 1, where the switching buck LED constant current control system 1 includes: a switch buck LED constant current control circuit 11 and a buck LED circuit 12.
As shown in fig. 8, the switching buck LED constant current control circuit 11 receives a current detection sampling signal of the buck LED circuit 12, and outputs a driving signal of the buck LED circuit.
Specifically, the circuit structure and the working principle of the switch buck-type LED constant current control circuit 11 are the same as those of the switch buck-type LED constant current control circuit in the first embodiment or the second embodiment, which are not repeated herein.
As shown in fig. 8, the buck LED circuit 12 obtains a stable output based on the control of the switching buck LED constant current control circuit 11.
Specifically, the buck LED circuit 12 includes an LED light emitting module 121, an inductor L, a freewheeling diode D, a power switch Q, and a sampling module 122. The anode of the LED light emitting module 121 is connected to an input power Vin, and the cathode is connected to one end of the inductor L. The other end of the inductor L is connected with the anode of the freewheeling diode D. And the cathode of the freewheeling diode D is connected with the input power Vin. In this embodiment, the power switch Q is an NMOS, a drain of the power switch Q is connected to an anode of the freewheeling diode D, a source of the power switch Q is connected to the sampling module 122 and then grounded, and a gate of the power switch Q is connected to the driving signal Drv; in practical use, the connection relationship between the ports of the power switch Q is related to the type of the power switch Q, and is not limited to this embodiment. The connection node between the power switch Q and the sampling module 122 outputs the current detection sampling signal Vcs, and in this embodiment, the sampling module 122 is implemented by a sampling resistor.
Example four
As shown in fig. 9 to 12, in this embodiment, the switching step-down LED constant current control method according to the present invention is described based on the switching step-down LED constant current control system 1 described in the third embodiment, and in practical use, any hardware circuit or software code according to the switching step-down LED constant current control method according to the present invention is applicable, and is not limited to the example of this embodiment. The switching step-down LED constant current control method comprises the following steps:
monitoring a current detection sampling signal Vcs of the buck LED circuit 12, outputting an effective On signal at a first time when the current detection sampling signal Vcs rises to the average reference Vref1 and a first time when the current detection sampling signal Vcs exceeds the average reference Vref1 in a period, and then failing to be the On signal, wherein if the current detection sampling signal Vcs is greater than the peak reference Vref2, the On signal is failed;
decreasing a turn-Off reference signal Ref _ Off when the current detection sampling signal Vcs is greater than the peak reference Vref2, increasing the turn-Off reference signal Ref _ Off when the current detection sampling signal Vcs is less than the peak reference Vref2, comparing a preset charging signal RC with the turn-Off reference signal Ref _ Off, generating the turn-Off end signal Off when the preset charging signal RC is greater than the turn-Off reference signal Ref _ Off;
and adjusting a driving signal Drv of the power switch tube Q based On the On signal On and the Off end signal Off to realize constant current output and control the ripple of the output current.
Specifically, as shown in fig. 9, in the initial state, the power switch Q is turned On, the On signal On is at a high level (active), the current detection sampling signal Vcs is smaller than the average reference Vref1, and at this time, the adder 114a2 starts to operate, and starts to count slowly from 0. The current detection sampling signal Vcs gradually increases as the inductor L is charged. When the current detection sampling signal Vcs reaches the average reference Vref1, the first comparison result Cp1 outputs a high level, the adder 114a2 stops working, the counting result is n, and the product of the counting result n and the basic clock generated by the oscillator 114a1 is the first time Δ T; at the same time, the subtracter 114a3 starts to operate, and the subtracter 114a3 subtracts the counting result n. In the initial stage, since the current detection sampling signal Vcs rises faster, when the subtractor 114a3 does not count to zero (the subtraction time is less than the first time Δ T), the current detection sampling signal Vcs is already greater than the peak reference Vref2, at this time, the second comparison result Cp2 outputs a high level, the On signal On jumps to a low level (failure), the power switch Q is controlled to be On when the On signal On is at the high level, and the power switch Q is controlled to be off when the On signal On is at the low level. As the current detection sampling signal Vcs is adjusted in multiple cycles, the rising speed of the current detection sampling signal Vcs is slowed down, the subtraction time approaches to the first time Δ T until the balance is reached, at this time, since the current detection sampling signal Vcs is always smaller than the peak reference Vref2, the subtracter 114a3 slowly counts from the counting result n back to 0, then the On signal On transitions to a low level, and the counting result n of the subtracter 114a3 multiplied by the basic clock is also Δ T. The upper and lower deviation values of the current detection sampling signal Vcs and the average reference Vref1 are equal, so that the average current value of the output current I _ LED is as follows: iaverage is Vref1/Rcs, where Rcs is the resistance of the sampling module 122.
Specifically, when the On signal On is at a low level, the adaptive clock generating module 113 starts to operate, and generates a corresponding Off end signal Off. As shown in fig. 10, if it is detected that the second comparison result Cp2 outputs a high level (a high level pulse is output) in one PWM period, the inverted logic signal LS of the second comparison result Cp2 is a low level pulse, when the driving signal Drv transitions to a low level, the pulse signal pulse (in this embodiment, the reference value is set to 300ns) arrives, the pull-Down control signal Down transitions to a high level, the pull-Down transistor MN is controlled to be turned on, and the turn-Off reference signal Ref _ Off is discharged and decreased until the turn-Off reference signal Ref _ Off is maintained when the pull-Down control signal Down transitions to a low level. As shown in fig. 11, if the second comparison result Cp2 is not detected (no high level pulse is output) in one PWM period, the inverted logic signal LS of the second comparison result Cp2 is always kept at a high level, when the driving signal Drv transitions to a low level, the pulse signal pulse comes, the pull-Up control signal Up transitions to a low level, the pull-Up transistor MP is controlled to be turned on, and the turn-Off reference signal Ref _ Off is charged Up until the pull-Up control signal Up transitions to a high level, the turn-Off reference signal Ref _ Off is kept. And comparing the preset charging signal RC with the turn-Off reference signal Ref _ Off, wherein the preset charging signal RC is a triangular wave signal, the charging is started when the turn-On signal On is invalid, the preset charging signal RC is gradually increased, and the turn-Off finishing signal Off is valid when the preset charging signal RC is greater than the turn-Off reference signal Ref _ Off, so that the power switch tube Q is controlled to be turned On again. As shown in fig. 12, after the power supply VDD is powered on, the first switch S1 is turned on first, the bias voltage Vbias provides an initial potential (in this embodiment, the reference value is 3V) to the turn-Off reference signal Ref _ Off first, and then the first switch S1 is turned Off. At this time, the turn-Off reference signal Ref _ Off is higher in potential, the turn-Off (low level) time Toff in the driving signal Drv is longer, meanwhile, the turn-on (high level) time Ton in the driving signal Drv is also longer, the charging current of the inductor L rises quickly, the peak current comparing module 112 is triggered to generate a high level pulse, the pull-Down control signal Down pulls Down the turn-Off reference signal Ref _ Off, and the turn-Off reference signal Ref _ Off gradually falls; when the output current I _ LED tends to be stable, the output of the peak current comparing module 112 no longer has a high level, and in order to avoid the shutdown reference signal Ref _ Off from decreasing due to the discharge of the first charging capacitor C1, the pull-Up control signal Up pulls Up the shutdown reference signal Ref _ Off at this time, so as to ensure that the shutdown reference signal Ref _ Off is always stable at a constant value. In the adaptive adjustment process, the period of the Off end signal Off is gradually reduced, and finally, the fixed discharge time Toff is realized, and the optimization of both inductance precision and ripple is realized.
The current detection sampling signal Vcs and the peak reference Vref2 are sent to the input terminal of the peak current comparison module 112, the output of the peak current comparison module 112 is sent to the PWM logic control module 114, meanwhile, the current detection sampling signal Vcs and the average reference voltage Vref1 are also sent to the input terminal of the average current comparison module 111, the output of the average current comparison module 111 is also sent to the PWM logic control module 114, and the On signal On is generated through counting control. When the On signal On is high, the driving signal Drv is high, and the external power switch tube Q is turned On; when the On signal On is low, the driving signal Drv is low, the external power switch tube Q is turned Off, and the adaptive clock generating module 113 is enabled, the adaptive clock generating module 113 outputs and generates a corresponding Off end signal Off, and the On signal On and the Off end signal Off are added together to realize one PWM period.
As an implementation manner of the present invention, the switching step-down LED constant current control method further includes: monitoring the current detection sampling signal Vcs, and turning off the power switch tube Q when the current detection sampling signal Vcs is larger than a short-circuit protection reference Vref3, wherein the short-circuit protection reference Vref3 is larger than the peak reference Vref 2.
As another implementation manner of the present invention, the switching buck LED constant current control method further includes: the values of the average reference Vref1 and the peak reference Vref2 are adjusted based on a dimming control signal DIM to achieve dimming control.
As shown in fig. 13, which is an input/output timing diagram of the switching buck LED constant current control circuit, system and method of the present invention, it can be seen that when the power supply VDD is powered on, the internal of the constant current control circuit is adaptively adjusted, and the constant current control circuit transitions from the discontinuous conduction mode to the continuous conduction mode, so as to achieve high accuracy and small ripple of the output current I _ LED on the LED light emitting unit. Fig. 13 is enlarged, the waveform in the discontinuous conduction mode before the output current I _ LED is stabilized is as shown in fig. 14, the average reference Vref1 is set to 200mV, the time of the incomplete adder before stabilization is consistent with that of the subtractor, the output of the peak current comparison module is detected when the subtractor operates, the conduction signal On is changed to a logic low level in advance, and the driving signal Drv is turned off to enter the inductance discharge stage. Fig. 13 is enlarged, waveforms in the continuous conduction mode after the output current I _ LED is stabilized are as shown in fig. 15, time matching between the adder and the subtractor is realized after stabilization, upper and lower deviation values of the current detection sampling signal Vcs and the average reference Vref1(200mV) are equal, and finally high accuracy and small ripple of the output current are realized.
In summary, the present invention provides a switching buck LED constant current control circuit, system and method, including: the device comprises an average current comparison module, a peak current comparison module, a self-adaptive clock generation module, a PWM logic control module and a driving module; the average current comparison module receives a current detection sampling signal of the buck LED circuit, and is used for comparing the current detection sampling signal with an average reference to obtain a first comparison result; the peak current comparison module receives the current detection sampling signal, is used for comparing the current detection sampling signal with a peak reference, and obtains a second comparison result; the average baseline is less than the peak baseline; the self-adaptive clock generating module receives the inverted logic signal of the second comparison result, adjusts the level of a turn-off reference signal and generates a corresponding turn-off finishing signal; the PWM logic control module is connected with the average current comparison module, the peak current comparison module and the output end of the self-adaptive clock generation module, adjusts the on-time of a logic control signal based on the first comparison result and the second comparison result, and adjusts the off-time of the logic control signal based on the off-end signal so as to realize the constant current output of the buck LED circuit and reduce the output current ripple of the buck LED circuit; the driving module is connected to the output end of the PWM logic control module and drives a power switch tube in the buck LED circuit to be switched on or switched off based on the logic control signal. Monitoring a current detection sampling signal of the buck LED circuit, and outputting an effective conduction signal in a first time when the current detection sampling signal rises to the average reference and a first time when the current detection sampling signal exceeds the average reference in a period, wherein the conduction signal fails; if the current detection sampling signal is larger than the peak value reference, the conducting signal fails in advance when the current detection sampling signal is larger than the peak value reference; decreasing a turn-off reference signal when the current sense sample signal is greater than the peak reference, and increasing the turn-off reference signal when the current sense sample signal is less than the peak reference; comparing a preset charging signal with the turn-off reference signal, and generating the turn-off end signal when the preset charging signal is greater than the turn-off reference signal; and adjusting the driving signal of the power switch tube based on the conducting signal and the turn-off finishing signal so as to realize constant current output and control the ripple of the output current. According to the switching step-down LED constant current control circuit, the switching step-down LED constant current control system and the switching step-down LED constant current control method, the PWM clock period is automatically adjusted through an internal circuit, the conduction time is controlled by adopting the counter, and the constant current control mode of average current detection and peak current detection is adopted, so that the high accuracy of small current ripples and output current is finally realized, and the switching step-down LED constant current control circuit has good linear regulation rate and load regulation rate; by adopting the self-adaptive adjustment, the LED output current can be very small, and the LED output current adjusting circuit can be widely applied to the field of electronic circuits. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (14)
1. The switch buck LED constant current control circuit is characterized by at least comprising:
the device comprises an average current comparison module, a peak current comparison module, a self-adaptive clock generation module, a PWM logic control module and a driving module;
the average current comparison module receives a current detection sampling signal of the buck LED circuit, and is used for comparing the current detection sampling signal with an average reference to obtain a first comparison result;
the peak current comparison module receives the current detection sampling signal, is used for comparing the current detection sampling signal with a peak reference, and obtains a second comparison result; the average baseline is less than the peak baseline;
the self-adaptive clock generating module receives the inverted logic signal of the second comparison result, adjusts the level of a turn-off reference signal and generates a corresponding turn-off finishing signal;
the PWM logic control module is connected with the average current comparison module, the peak current comparison module and the output end of the self-adaptive clock generation module, adjusts the on-time of a logic control signal based on the first comparison result and the second comparison result, and adjusts the off-time of the logic control signal based on the off-end signal so as to realize the constant current output of the buck LED circuit and reduce the output current ripple;
the driving module is connected to the output end of the PWM logic control module and drives a power switch tube in the buck LED circuit to be switched on or switched off based on the logic control signal.
2. The switching buck LED constant current control circuit of claim 1, wherein: the self-adaptive clock generation module comprises a reference signal turn-off control unit and a turn-off finishing signal generation unit;
the turn-off reference signal control unit receives an inverted logic signal of the second comparison result, and generates a pull-down control signal when the current detection sampling signal is greater than the peak reference; generating a pull-up control signal when the current detection sampling signal is less than the peak reference;
the turn-off end signal generating unit receives the pull-down control signal and the pull-up control signal to adjust the magnitude of a turn-off reference signal, the pull-down control signal controls the turn-off reference signal to discharge to reduce the level, and the pull-up control signal controls the turn-off reference signal to charge to increase the level; and meanwhile, comparing a preset charging signal with the turn-off reference signal, and generating the turn-off end signal when the preset charging signal is greater than the turn-off reference signal.
3. The switching buck LED constant current control circuit of claim 2, wherein: the turn-off reference signal control unit comprises a first inverter, a first NAND gate, a second NAND gate, a third NAND gate, a fourth NAND gate and a second inverter;
the input end of the first NAND gate is respectively connected with the inverted logic signal of the second comparison result and the output end of the second NAND gate; the input end of the first inverter receives an inverted logic signal of the second comparison result; the input end of the second NAND gate is respectively connected with the first inverter and the output end of the first NAND gate; the input end of the third NAND gate is respectively connected with the input end of the first NAND gate and a pulse signal, the input end of the second inverter is connected with the output end of the third NAND gate, and the output end of the second inverter outputs the pull-down control signal; the input end of the fourth NAND gate is respectively connected with the input end of the second NAND gate and the pulse signal, and the output end of the fourth NAND gate outputs the pull-up control signal.
4. The switching buck LED constant current control circuit of claim 2, wherein: the turn-off end signal generating unit comprises a first current source, an upper pull tube, a lower pull tube, a second current source, a first charging capacitor, a first switch, a third current source, a second charging capacitor and a comparator;
the first current source, the pull-up tube, the pull-down tube and the second current source are sequentially connected in series between a power supply and the ground, a connection node of the pull-up tube and the pull-down tube outputs the turn-off reference signal, a control end of the pull-up tube is connected with the pull-up control signal, and a control end of the pull-down tube is connected with the pull-down control signal; one end of the first charging capacitor is connected with the turn-off reference signal, and the other end of the first charging capacitor is grounded; one end of the first switch is connected with the turn-off reference signal, and the other end of the first switch is grounded after being connected with bias voltage;
one end of the third current source is connected with a power supply, and the other end of the third current source is connected with the second charging capacitor; the other end of the second charging capacitor is grounded; a connection node of the third current source and the second charging capacitor outputs the preset charging signal;
the input end of the comparator is respectively connected with the turn-off reference signal and the preset charging signal, and outputs the turn-off finishing signal.
5. The switching buck LED constant current control circuit according to any one of claims 1 to 4, wherein: the PWM logic control module comprises a conducting signal generating unit and a logic control signal generating unit;
the conducting signal generating unit receives the first comparison result and the second comparison result, and outputs an effective conducting signal at a first time when the current detection sampling signal rises to the average reference and a first time when the current detection sampling signal exceeds the average reference, wherein if the current detection sampling signal is greater than the peak reference, the conducting signal is directly invalid;
the logic control signal generating unit is connected with the conducting signal generating unit and the output end of the self-adaptive clock generating module, and generates the logic control signal based on the conducting signal and the turn-off finishing signal.
6. The switching buck LED constant current control circuit according to claim 5, wherein: the conducting signal generating unit comprises an oscillator, an adder and a subtracter;
the adder is connected with the oscillator and the output end of the average current comparison module, and when the current detection sampling signal rises to the average reference, the adder carries out addition operation to obtain a counting result corresponding to the first time;
the subtracter is connected with the oscillator, the adder and the output end of the peak current comparison module, and is used for subtracting the counting result of the adder, and if the current detection sampling signal is smaller than the peak reference, the conducting signal is controlled to be invalid when the subtraction result is zero; and if the current detection sampling signal is larger than the peak value reference, directly controlling the conduction signal to fail.
7. The switching buck LED constant current control circuit of claim 1, wherein: the switching step-down LED constant current control circuit further comprises a short-circuit protection module and/or a dimming module; the short-circuit protection module receives the current detection sampling signal, compares the current detection sampling signal with a short-circuit protection reference, and turns off the power switch tube when the current detection sampling signal is greater than the short-circuit protection reference, wherein the short-circuit protection reference is greater than the peak value reference; the dimming module receives a dimming control signal and adjusts values of the average reference and the peak reference based on the dimming control signal.
8. The switch buck LED constant current control system is characterized by at least comprising:
the switch buck-type LED constant current control circuit and the buck-type LED circuit as claimed in any one of claims 1 to 7, wherein the switch buck-type LED constant current control circuit receives a current detection sampling signal of the buck-type LED circuit and outputs a driving signal of the buck-type LED circuit.
9. The switching buck LED constant current control system of claim 8, wherein: the voltage-reducing LED circuit comprises an LED light-emitting module, an inductor, a freewheeling diode, a power switch tube and a sampling module;
the anode of the LED light-emitting module is connected with an input power supply, and the cathode of the LED light-emitting module is connected with one end of the inductor; the other end of the inductor is connected with the anode of the freewheeling diode; the negative electrode of the freewheeling diode is connected with the input power supply; one end of the power switch tube is connected with the anode of the freewheeling diode, the other end of the power switch tube is connected with the sampling module and then grounded, and the control end of the power switch tube is connected with the driving signal; and the current detection sampling signal is output by the connection node of the power switch tube and the sampling module.
10. A constant current control method for a switch buck LED is characterized by at least comprising the following steps:
monitoring a current detection sampling signal of the buck LED circuit, and outputting an effective conduction signal in a first time when the current detection sampling signal rises to the average reference and a first time when the current detection sampling signal exceeds the average reference in a period, wherein the conduction signal fails; if the current detection sampling signal is larger than the peak value reference, the conducting signal is invalid;
decreasing a turn-off reference signal when the current detection sampling signal is greater than the peak reference, increasing the turn-off reference signal when the current detection sampling signal is less than the peak reference, comparing a preset charging signal with the turn-off reference signal, and generating the turn-off end signal when the preset charging signal is greater than the turn-off reference signal;
adjusting a driving signal of the power switch tube based on the conducting signal and the turn-off finishing signal to realize constant current output and control ripple waves of output current;
wherein the average baseline is less than the peak baseline.
11. The switching buck LED constant current control method of claim 10, wherein: the method for obtaining the conducting signal comprises the following steps:
when the current detection sampling signal rises to the average reference, performing addition operation to obtain a counting result corresponding to first time;
subtracting the counting result, and if the current detection sampling signal is smaller than the peak value reference, controlling the conducting signal to be invalid when the subtraction operation result is zero; and if the current detection sampling signal is larger than the peak value reference, directly controlling the conduction signal to fail.
12. The switching buck LED constant current control method of claim 10, wherein: and when the turn-on signal is effective, controlling a power switch tube in the buck LED circuit to be turned on, when the turn-on signal is ineffective, controlling the power switch tube to be turned off, and when the turn-off finishing signal is effective, controlling the power switch tube to be turned on again.
13. The switching buck LED constant current control method of claim 10, wherein: the switching step-down LED constant current control method further comprises the following steps: and monitoring the current detection sampling signal, and turning off the power switch tube when the current detection sampling signal is larger than a short-circuit protection reference, wherein the short-circuit protection reference is larger than the peak value reference.
14. The switching buck LED constant current control method of claim 10, wherein: the switching step-down LED constant current control method further comprises the following steps: and adjusting the values of the average reference and the peak reference based on a dimming control signal to realize dimming control.
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Denomination of invention: Switch buck LED constant current control circuit, system, and method Effective date of registration: 20231008 Granted publication date: 20230505 Pledgee: Bank of China Limited Wuxi Branch Pledgor: China Resources micro integrated circuit (Wuxi) Co.,Ltd. Registration number: Y2023980060027 |
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