CN117336920A - Low-voltage program-controlled LED constant current driving circuit based on singlechip - Google Patents
Low-voltage program-controlled LED constant current driving circuit based on singlechip Download PDFInfo
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- CN117336920A CN117336920A CN202311416176.0A CN202311416176A CN117336920A CN 117336920 A CN117336920 A CN 117336920A CN 202311416176 A CN202311416176 A CN 202311416176A CN 117336920 A CN117336920 A CN 117336920A
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- 238000004146 energy storage Methods 0.000 claims abstract description 21
- 239000003990 capacitor Substances 0.000 claims abstract description 8
- 239000011324 bead Substances 0.000 claims description 16
- 230000001939 inductive effect Effects 0.000 claims description 6
- 230000007423 decrease Effects 0.000 claims description 2
- 238000005070 sampling Methods 0.000 claims description 2
- 239000013307 optical fiber Substances 0.000 claims 1
- 230000001965 increasing effect Effects 0.000 description 9
- HEZMWWAKWCSUCB-PHDIDXHHSA-N (3R,4R)-3,4-dihydroxycyclohexa-1,5-diene-1-carboxylic acid Chemical compound O[C@@H]1C=CC(C(O)=O)=C[C@H]1O HEZMWWAKWCSUCB-PHDIDXHHSA-N 0.000 description 8
- 238000010586 diagram Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000001075 voltammogram Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
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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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- 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]
- H05B45/10—Controlling the intensity of the light
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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
- H05B45/32—Pulse-control circuits
- H05B45/325—Pulse-width modulation [PWM]
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Abstract
The invention discloses a low-voltage program-controlled LED constant current driving circuit based on a singlechip, which comprises an MOS tube Q1, wherein a source electrode of the MOS tube Q1 is connected with an input power Vin, a drain electrode of the MOS tube Q1 is connected with one end of an energy storage inductor L1, one end of an energy storage capacitor C3 is connected with the drain electrode of the MOS tube Q1, the other end of the energy storage inductor L1 is grounded, the other end of the energy storage inductor L1 is connected with the anode of a freewheeling diode D1, when the MOS tube Q1 is conducted, energy is stored, and when the MOS tube Q1 is turned off, continuous current is provided for a load; and a flywheel diode D1, the cathode of which is connected with the output Vout. The invention directly constructs the booster circuit and the constant current drive circuit by utilizing the PWM component, the comparator component and the AD component in the MCU, samples the working current of the LED, compares the working current with the working current set in the program, and dynamically adjusts the duty ratio of PWM output pulse according to the comparison result, thereby adjusting and controlling the working voltage at two ends of the LED, and achieving the purpose of adjusting the working current.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a low-voltage program-controlled LED constant current driving circuit based on a single chip microcomputer.
Background
Since the LED is a semiconductor device with sensitive characteristics and has negative temperature characteristics, the LED is extremely easy to burn out or cause light attenuation due to improper use. Thus, stable operation and protection of the operating current are required during application.
Fig. 1 is a typical voltammogram of LEDs of different colors. As can be seen from the volt-ampere characteristics of the LED, when the forward voltage across the LED reaches the LED turn-on threshold, the forward operating current versus voltage relationship is very steep. This means that when the voltage applied across the LED has a slight variation, its operating current varies very much.
When the working current of the LED is increased, the PN junction temperature of the LED is increased, and as the LED has negative temperature characteristics, when the working current of the LED is increased, the resistance of the LED is reduced, so that the working current of the LED is further increased, the PN junction temperature is further increased, a cacheline cycle is formed, and finally the LED is burnt. Therefore, the LED generally adopts a constant current driving mode, preventing the LED from thermal runaway.
In some special application scenarios, such as battery-powered products, the conventional LED driving circuit mostly adopts a constant current driving chip, but because the voltage is low, the turn-on threshold voltage of the LED cannot be reached, the LED is usually boosted and then driven, and the driving mode is shown in fig. 2, but in the typical low-voltage constant current driving LED circuit, several disadvantages still exist that the special application cannot be satisfied:
1. the working voltage is still higher, most of the boosting DCDC or constant current driving chips have the lowest working voltage of 2.7V, and the working voltage is still higher for some special products such as products powered by a single battery;
2. the DCDC chip or the constant current driving chip is often rated to achieve about 90% of efficiency, but under a large current, the chip generates heat seriously, the efficiency drops rapidly, the comprehensive efficiency of the DCDC chip and the constant current driving chip is lower after the DCDC chip and the constant current driving chip are connected in series, the comprehensive efficiency of the DCDC chip and the constant current driving chip is often only about 50% -60%, and for a battery powered product, the energy utilization rate is too low, and the waste is serious;
3. the dynamic dimming can not be performed as required, although many DCDC chips and constant current driving chips can adjust the output voltage or the output current through PWM, because the DCDC chips and the constant current driving chips have no programmable capability, only a specific brightness can be realized, the brightness of the LED can not be dynamically adjusted according to the actual needs, and if the dynamic dimming is required, the MCU is additionally added to realize the program control of the output voltage or the output current, but the circuit complexity and the BOM cost are definitely increased.
Disclosure of Invention
In order to solve the problems, the invention provides a low-voltage program-controlled LED constant-current driving circuit based on a singlechip, which directly constructs a booster circuit and a constant-current driving circuit by utilizing a PWM component, a comparator component and an AD component in an MCU, samples the working current of an LED, compares the working current with the working current set in a program, and dynamically adjusts the duty ratio of PWM output pulses according to the comparison result, thereby adjusting and controlling the working voltage at two ends of the LED, achieving the purpose of adjusting the working current of the LED, and effectively solving a plurality of problems in the prior art.
The invention is realized by the following technical scheme: a low-voltage program-controlled LED constant current driving circuit based on a singlechip comprises:
MOS tube Q1 with source connected to input power supply V in The drain electrode is connected with one end of the energy storage inductance L1, so that the current of the input power supply Vin flows to the output V in a controlled manner out ;
One end of the energy storage capacitor C3 is connected with the drain electrode of the MOS tube Q1, and the other end of the energy storage capacitor C is grounded to play a role in energy storage, so that continuous energy supply of a load is ensured;
the other end of the energy storage inductor L1 is connected with the anode of the freewheeling diode D1, energy is stored when the MOS tube Q1 is turned on, and continuous current is provided for a load when the MOS tube Q1 is turned off;
the cathode of the freewheeling diode D1 is connected with the output Vout and is used for providing a loop for the inductive current when the MOS transistor Q1 is turned off so as to prevent the current from flowing backwards;
the singlechip U1 is connected with the MOS tube Q1 and used for controlling the on and off of the MOS tube Q1 and detecting and controlling the output voltage and the output current.
As a preferable technical scheme, when the PWM driving MOS transistor Q1 is turned on, the voltages at two ends of the inductor L1 are: v (V) Lon =V in At this time, according to the basic equation of inductance: v (V) Lon = L * dI on / dT on The inductor current will rise linearly.
As a preferable technical scheme, when the PWM driving MOS tube Q1 is cut off, the inductorThe voltage across L1 is: v (V) Loff = V out -V in At this time, the inductor current linearly decreases, and according to the basic characteristic equation of the inductor: v (V) Loff = L * dI off / dT off 。
As a preferred technical solution, according to the law of inductive voltage volt-second balance: v (V) Lon * T on = V Loff * T off And the duty cycle of the PWM drive signal output by the known DC-DC controller is D, then: d=t on /( T on+ T off )。
As a preferred technical solution, the voltage output of the BOOST topology circuit is: v (V) out = V in * The larger the duty cycle D, the higher the output voltage, and conversely the lower the output voltage.
As a preferable technical scheme, after Vout is established, the LED lamp bead D2 is driven, and meanwhile, the voltage drop V is established on R1 R Wherein the LED lamp bead current can pass through formula I led = V R R1 calculation.
As a preferable technical scheme, the singlechip U1 utilizes an AD component contained therein to sample voltages at two ends of the R1 in real time and calculate the current value I of the LED lamp bead led And comparing the PWM output duty ratio D value with the set value, thereby adjusting the PWM output duty ratio D value.
As the preferable technical scheme, the AD component is used for continuously sampling the LED lamp bead current and adjusting the PWM output duty ratio D value in real time.
As a preferable technical scheme, the voltage output formula V of the topological circuit is based on BOOST out = V in * D/(1-D), when the battery voltage V in When the PWM output falls, the output voltage Vout can be kept stable by adjusting the duty ratio D value of the PWM output.
As the preferable technical scheme, the model of the singlechip U1 is STC8G1K08A, but is not limited to the model.
The beneficial effects of the invention are as follows: 1. according to the invention, only one MCU chip is needed, and the aim of boosting and constant current driving of the LED can be realized by matching with a small number of peripheral components such as an energy storage inductor, a flywheel diode, an energy storage capacitor, a small number of resistors and the like;
2. compared with the traditional control mode, the invention omits the DCDC boost chip and the constant current drive chip, obviously reduces the BOM cost, occupies less space and is easier to integrate and assemble;
3. the invention has flexible control, is used for the patent, can dynamically control the brightness of the LED lamp beads according to the use scene, has large brightness adjusting range, is more flexible to use, and can realize the brightness control under the complex scene without increasing the cost.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a typical prior art LED volt-ampere characteristic;
FIG. 2 is a schematic diagram of a typical low voltage constant current driving LED circuit in the prior art;
fig. 3 is a circuit diagram of the present invention.
Description of the embodiments
All of the features disclosed in this specification, or all of the steps in a method or process disclosed, may be combined in any combination, except for mutually exclusive features and/or steps.
Any feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. That is, each feature is one example only of a generic series of equivalent or similar features, unless expressly stated otherwise.
As shown in FIG. 3, the low-voltage program-controlled LED constant-current driving circuit based on the singlechip comprises a MOS tube Q1, wherein the source electrode of the MOS tube Q1 is connected with an input power Vin, and the drain electrode of the MOS tube Q1 is connected with one end of an energy storage inductor L1, so that the input power V in Current-controlled flow direction output V out ;
One end of the energy storage capacitor C3 is connected with the drain electrode of the MOS tube Q1, and the other end of the energy storage capacitor C is grounded to play a role in energy storage, so that continuous energy supply of a load is ensured;
the other end of the energy storage inductor L1 is connected with the anode of the freewheeling diode D1, energy is stored when the MOS tube Q1 is turned on, and continuous current is provided for a load when the MOS tube Q1 is turned off;
freewheel diode D1 with its cathode connected to output V out The MOS transistor Q1 is used for providing a loop for the inductive current when the MOS transistor Q1 is turned off, so that current reverse filling is prevented;
the singlechip U1 is connected with the MOS tube Q1 and used for controlling the on and off of the MOS tube Q1 and detecting and controlling the output voltage and the output current.
When the PWM driving MOS tube is conducted, the conduction voltage drop of the MOS tube is ignored, and the voltage at two ends of the inductor is kept unchanged at the moment:
V Lon = V in
according to the basic equation of inductance:
V Lon = L * dI on / dT on
the inductor current will rise linearly.
When the PWM driving MOS tube is cut off, the inductance current passes through the freewheeling diode D to form a loop (neglecting diode voltage drop), the voltage at two ends of the inductance is as follows, and the inductance current is linearly reduced:
V Loff = V out -V in
also according to the inductance basic characteristic equation:
V Loff = L * dI off / dT off
from the law of inductive voltage volt-second balance:
V Lon * T on = V Loff * T off
assuming that the DC-DC controller is known to output a PWM drive signal with a duty cycle D:
D = T on /( T on+ T off )
by combining the formulas, the BOOST topology circuit voltage output: v (V) out = V in *D /(1-D)。
When the duty ratio is D>At 0.5, vout>Vin, the BOOST circuit now exhibits BOOST, when the duty cycle is D<At 0.5, V out At this point the boost circuit appears to step down. The larger the duty cycle D, the higher the output voltage, and conversely the lower the output voltage.
When V is out After the establishment, the LED lamp bead D2 is driven, and meanwhile, the voltage drop V is established on the R1 R 。
LED lamp bead current can be represented by formula I led = V R R1 calculation.
An AD component is arranged in the singlechip U1, and the voltage at the two ends of the R1 is sampled in real time and the current value I of the LED lamp bead is calculated led Will I led And comparing with the set value.
If the set value is less than I led Then the PWM duty ratio D is reduced to make the output voltage V out And the working current of the LED lamp bead D2 is reduced.
If the set value is > I led Then the PWM duty ratio D is increased to output the voltage V out And the working current of the LED lamp bead D2 is increased.
The LED lamp bead current is continuously sampled through the AD, and the PWM output duty ratio D value is adjusted in real time, so that the LED lamp bead current always floats in a small range, and LED constant current driving is realized. The pearl attenuation risk and the thermal runaway risk of the LED lamp are effectively reduced.
Meanwhile, according to a BOOST type topological circuit voltage output formula V out = V in * D/(1-D) as the battery voltage V in When falling, the output voltage V can also be made by adjusting the value of the space ratio D out And the voltage is kept stable, so that flexible control of output voltage and output current is realized.
The invention directly constructs the booster circuit and the constant current drive circuit by utilizing the PWM component, the comparator component and the AD component in the MCU, samples the working current of the LED, compares the working current with the working current set in the program, and dynamically adjusts the duty ratio of PWM output pulse according to the comparison result, thereby adjusting and controlling the working voltage at two ends of the LED, and achieving the purpose of adjusting the working current.
The foregoing is merely illustrative of specific embodiments of the present invention, and the scope of the invention is not limited thereto, but any changes or substitutions that do not undergo the inventive effort should be construed as falling within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope defined by the claims.
Claims (10)
1. A low-voltage program-controlled LED constant current driving circuit based on a singlechip is characterized in that: the circuit comprises:
MOS tube Q1 with source connected to input power supply V in The drain electrode is connected with one end of the energy storage inductance L1, thereby the input power V in Current-controlled flow direction output V out ;
One end of the energy storage capacitor C3 is connected with the drain electrode of the MOS tube Q1, and the other end of the energy storage capacitor C is grounded to play a role in energy storage, so that continuous energy supply of a load is ensured;
the other end of the energy storage inductor L1 is connected with the anode of the freewheeling diode D1, energy is stored when the MOS tube Q1 is turned on, and continuous current is provided for a load when the MOS tube Q1 is turned off;
freewheel diode D1 with its cathode connected to output V out The MOS transistor Q1 is used for providing a loop for the inductive current when the MOS transistor Q1 is turned off, so that current reverse filling is prevented;
the singlechip U1 is connected with the MOS tube Q1 and used for controlling the on and off of the MOS tube Q1 and detecting and controlling the output voltage and the output current.
2. The low-voltage program-controlled LED constant current driving circuit based on the single chip microcomputer according to claim 1, wherein the low-voltage program-controlled LED constant current driving circuit is characterized in that: when the PWM driving MOS Q1 is turned on, the voltage across the inductor L1 is: v (V) Lon =V in At this time, according to the basic equation of inductance: v (V) Lon = L * dI on / dT on The inductor current will rise linearly.
3. The low-voltage program-controlled LED constant current driving circuit based on the single chip microcomputer according to claim 1, wherein the low-voltage program-controlled LED constant current driving circuit is characterized in that: when the PWM driving MOS Q1 is turned off, the voltage across the inductor L1 is: v (V) Loff = V out -V in At this time, electricityThe induced current decreases linearly and is based on the basic characteristic equation of inductance: v (V) Loff = L * dI off / dT off 。
4. The low-voltage program-controlled LED constant current driving circuit based on the single chip microcomputer according to claim 1, wherein the low-voltage program-controlled LED constant current driving circuit is characterized in that: according to the law of inductive voltage volt-second balance: v (V) Lon * T on = V Loff * T off And the duty cycle of the PWM drive signal output by the known DC-DC controller is D, then: d=t on /( T on+ T off )。
5. The low-voltage program-controlled LED constant current driving circuit based on the single chip microcomputer according to claim 4, wherein the low-voltage program-controlled LED constant current driving circuit is characterized in that: the voltage output of the BOOST topology is: v (V) out = V in * The larger the duty cycle D, the higher the output voltage, and conversely the lower the output voltage.
6. The low-voltage program-controlled LED constant current driving circuit based on the single chip microcomputer according to claim 1, wherein the low-voltage program-controlled LED constant current driving circuit is characterized in that: when V is out After the establishment, the LED lamp bead D2 is driven, and meanwhile, the voltage drop V is established on the R1 R Wherein the LED lamp bead current can pass through formula I led = V R R1 calculation.
7. The low-voltage program-controlled LED constant current driving circuit based on the single chip microcomputer according to claim 6, wherein the low-voltage program-controlled LED constant current driving circuit is characterized in that: the singlechip U1 utilizes the AD component contained therein to sample the voltages at the two ends of the R1 in real time and calculate the current value I of the LED lamp bead led And comparing the PWM output duty ratio D value with the set value, thereby adjusting the PWM output duty ratio D value.
8. The low-voltage program-controlled LED constant current driving circuit based on the single chip microcomputer as claimed in claim 7, wherein: and uninterrupted sampling is carried out on the LED lamp bead current through the AD component, and the PWM output duty ratio D value is adjusted in real time.
9. The singlechip-based optical fiber according to claim 5The low-voltage program-controlled LED constant-current driving circuit is characterized in that: according to a BOOST type topological circuit voltage output formula V out = V in * D/(1-D), when the battery voltage V in When falling, the output voltage V can be made by adjusting the duty ratio D value of PWM output out And remains stable.
10. The low-voltage program-controlled LED constant current driving circuit based on the single chip microcomputer according to claim 1, wherein the low-voltage program-controlled LED constant current driving circuit is characterized in that: the model of the singlechip U1 is STC8G1K08A.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311416176.0A CN117336920A (en) | 2023-10-27 | 2023-10-27 | Low-voltage program-controlled LED constant current driving circuit based on singlechip |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311416176.0A CN117336920A (en) | 2023-10-27 | 2023-10-27 | Low-voltage program-controlled LED constant current driving circuit based on singlechip |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117595067A (en) * | 2024-01-18 | 2024-02-23 | 深圳市吉斯迪科技有限公司 | Constant-current power supply circuit of capacitor energy-storage pulse laser |
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2023
- 2023-10-27 CN CN202311416176.0A patent/CN117336920A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117595067A (en) * | 2024-01-18 | 2024-02-23 | 深圳市吉斯迪科技有限公司 | Constant-current power supply circuit of capacitor energy-storage pulse laser |
| CN117595067B (en) * | 2024-01-18 | 2024-04-02 | 深圳市吉斯迪科技有限公司 | Constant-current power supply circuit of capacitor energy-storage pulse laser |
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