Summary of the invention
The technical problem to be solved is to provide a kind of LED backlight light adjusting system, and the light modulation of this LED backlight isSystem can realize stepless and constant-current dimming, and reliability is high.
The technical solution of invention is as follows:
A kind of LED backlight light adjusting system, examines including MCU, MMI module, PWM light-adjusting module, multiselect one analog switch and electric currentSlowdown monitoring circuit；MCU is microprocessing unit, and MMI is human-machine interface module；
LED backlight has multiple LED, and multiple LED are divided into N group, forms the N bar lamp string of series connection, based on N bar lamp string shapeBecome N number of light emitting module；N is the integer more than or equal to 2；
Current detection circuit includes measuring resistance Rx and voltage detection module；
Multiselect one analog switch has N number of passage, is provided with N number of channel branch IO end and a public IO end；Multiselect one simulation is openedPass is additionally provided with channel selecting end；Described channel selecting end is connected with the I/O port of MCU；MCU outputs signals to channel selecting endControl any one channel conductive；
MCU output pwm pulse is to PWM light-adjusting module；The public IO of output termination multiselect one analog switch of PWM light-adjusting moduleEnd；The positive terminal of N number of light emitting module connects multiselect one analog switch respectively and has N number of channel branch IO end；Bearing of N number of light emitting moduleExtreme all by measuring resistance Rx ground connection；
The data-in port of the output termination MCU of voltage detection module.
N is 2 or 4.
Light emitting module is the LED light module with energy-storage function；Light emitting module includes LED string, energy storage inductor and continuesStream diode；LED string is connected with energy storage inductor and is formed luminous branch road；Fly-wheel diode and described luminous branch circuit parallel connection.
Voltage detection module is in series by amplifier and A/D converter；The input termination of amplifier measures resistance Rx, A/The output termination MCU of D transducer.
PWM light-adjusting module is constant-current driven chip.
MCU is provided with intervalometer and channel selecting number generation unit；It is suitable that channel selecting number generation unit produces between 1-NSequence integer or immediately integer；Intervalometer is for producing a timing between 1-30 minute.Sequentially integer refers to first be sequentially generated1,2,3 ..., N, after arriving N, the next one is 1;The preferred value of timing is 5 minutes, 10 minutes, 15 minutes.
MMI module is button or touch screen.
MCU is DSP, arm processor, single-chip microcomputer, FPGA or CPLD.
Realize the stepless constant-current dimming of LED backlight according to the following steps:
Step 1: initialize；
Being set as 1 including by channel selecting number, the dutycycle of pwm pulse is set to 0.5；
Step 2: start intervalometer；
Step 3: when being timed to, MCU produces channel selecting number；
Step 4: multiselect one analog switch selects, based on channel selecting number, riches all the way optical module；
Step 5: input based on MMI instruction produces pwm pulse；
The input instruction of MMI is used for setting dutycycle, and MCU produces pwm pulse according to the dutycycle set, it is achieved stepless dimming；
Step 6: current constant control
Using the electric current of current detection circuit detection light emitting module, MCU electric current based on detection adjusts the dutycycle of pwm pulse,Work as controller, then MCU stops output pwm pulse, it is achieved LED constant current controls and overcurrent protection.
Beneficial effect:
The LED backlight light adjusting system of the present invention, has the following characteristics that
1. reliability is high；
Multiple LED are divided into N group, rotation startup and switch operating, it is to avoid some lamp caloric value that works long hours is big and damageBad LED, therefore, reliability is high.
2. current constant control:
By the operating current of current detection circuit detection LED, this current value, as feedback signal, coordinates controller (such as PIDController, fuzzy control etc.), high-precision current constant can be realized；Additionally the employing of inductance and fly-wheel diode is the most veryDetermine electric current, it is to avoid LED flickering, it is provided that stable light efficiency.
3. overcurrent protection
Being equally based on current detection circuit and realize over-current detection and protection, threshold value is the current value to LED infringement, as used pole0.95 times of limit value as threshold value.
4. circuit is simple, it is easy to implement.
Multiway analog switch, light modulation chip, current detection circuit and MCU are mature modules, it is easy to implement.
5. use PWM light modulation mechanism, stepless dimming can be realized；
In sum, this LED backlight light adjusting system feature richness, reliability is high, it is easy to implements, is skillfully constructed.
Embodiment 1: such as Fig. 1 to 3, a kind of LED backlight light adjusting system, including MCU, MMI module, PWM light-adjusting module, multiselectOne analog switch and current detection circuit；MCU is microprocessing unit, and MMI is human-machine interface module；
LED backlight has multiple LED, and multiple LED are divided into N group, forms the N bar lamp string of series connection, based on N bar lamp string shapeBecome N number of light emitting module；N is the integer more than or equal to 2；
Current detection circuit includes measuring resistance Rx and voltage detection module；
Multiselect one analog switch has N number of passage, is provided with N number of channel branch IO end and a public IO end；Multiselect one simulation is openedPass is additionally provided with channel selecting end；Described channel selecting end is connected with the I/O port of MCU；MCU outputs signals to channel selecting endControl any one channel conductive；
MCU output pwm pulse is to PWM light-adjusting module；The public IO of output termination multiselect one analog switch of PWM light-adjusting moduleEnd；The positive terminal of N number of light emitting module connects multiselect one analog switch respectively and has N number of channel branch IO end；Bearing of N number of light emitting moduleExtreme all by measuring resistance Rx ground connection；
The data-in port of the output termination MCU of voltage detection module.
N is 2 or 4.
Light emitting module is the LED light module with energy-storage function；Light emitting module includes LED string, energy storage inductor and continuesStream diode；LED string is connected with energy storage inductor and is formed luminous branch road；Fly-wheel diode and described luminous branch circuit parallel connection.
Voltage detection module is in series by amplifier and A/D converter；The input termination of amplifier measures resistance Rx, A/The output termination MCU of D transducer.
PWM light-adjusting module is constant-current driven chip.
MCU is provided with intervalometer and channel selecting number generation unit；It is suitable that channel selecting number generation unit produces between 1-NSequence integer or immediately integer；Intervalometer is for producing a timing between 1-30 minute.Sequentially integer refers to first be sequentially generated1,2,3 ..., N, after arriving N, the next one is 1;The preferred value of timing is 5 minutes, 10 minutes, 15 minutes.
MMI module is button or touch screen.
MCU is DSP, arm processor, single-chip microcomputer, FPGA or CPLD.
Realize the stepless constant-current dimming of LED backlight according to the following steps:
Step 1: initialize；
Being set as 1 including by channel selecting number, the dutycycle of pwm pulse is set to 0.5；
Step 2: start intervalometer；
Step 3: when being timed to, MCU produces channel selecting number；
Step 4: multiselect one analog switch selects, based on channel selecting number, riches all the way optical module；
Step 5: input based on MMI instruction produces pwm pulse；
The input instruction of MMI is used for setting dutycycle, and MCU produces pwm pulse according to the dutycycle set, it is achieved stepless dimming；
Step 6: current constant control
Using the electric current of current detection circuit detection light emitting module, MCU electric current based on detection adjusts the dutycycle of pwm pulse,Work as controller, then MCU stops output pwm pulse, it is achieved LED constant current controls and overcurrent protection.