CN101115334B - PWM control signal generating method of series multi-pixel LED lamp - Google Patents

Abstract

The invention provides a PWM control signal generation method of a series multi-pixel LED light. Firstly a content display transmission implement writes the drive parameters into a double ports RAM, then a drive parameters read module is started; the drive parameters read module reads the configured parameters from the double ports RAM and provides to all Counting units, and a PWM control output module is started; at last the PWM control output module generates the PWM control signal of the series LED pixel light. The drive parameters of the invention can be configured, the system structure is simple, the wires connected with the light are less (four wires), and the cost of pixel drive is low. By adopting the series multi-pixel light driven by a shift register, and the PWM control signal generated method with low costs and low complexity, the invention is applicable to the market requirements of the landscape lighting industry.

Description

The pwm control signal generation method of series multi-pixel LED lamp

Technical field

The present invention relates to a kind of pwm control signal generation method, specifically be meant the generation method that drives the series multi-pixel LED lamp pwm control signal.

Background technology

The conventional type of drive of LED lamp has current drives and pulsed drive, current drives needs the D/A conversion, circuit cost is very high, pulsed drive is divided into sub-field scan driving again and PWM drives, sub-field-sweep method effect religion is poor, and need clock frequency higher, and PWM drive to compare and does not have above shortcoming, is extensive use of.

At present, LED lamp PWM produces chip and mostly is parallel control, as the BHL2000 of Beijing North Huahong micro-system Co., Ltd and the PW19281 of Sony Corporation etc., the video data of each LED lamp is input to the internal storage unit of chip, counter and comparator by inside produce pwm signal, parallel drive LED shows, each LED needs a pin to drive, because the distance between chip for driving and the LED is unequal, the length of signal connecting line does not wait yet, the LED number that each chip drove simultaneously is many more, and needed signal connecting line is also many more, and therefore this type of drive causes very big difficulty to wiring.Common in the market LED fluorescent tube generally has 8 or 16 pixels, each pixel is divided into red, green, blue three basic colors (primary colours) LED lamp or primary-color LED lamp group (being about to a plurality of LED lamps with color connects together to increase brightness), primary-color LED is identical with the control mode of primary-color LED lamp group, it hereinafter is the example explanation with the primary-color LED, in large size city landscape lamp decoration system, used fluorescent tube is several thousand at least of several thousand used fluorescent tubes at least, up to ten thousand at most, spacing between the fluorescent tube reaches tens meters, if by parallel type of drive, each fluorescent tube is controlled with a chip for driving, so because such chip price costliness cost is too high, if a plurality of fluorescent tube is with a chip then the line between fluorescent tube and the fluorescent tube is very many, with 8 fluorescent tubes of each chip drives, 8 pixels of each fluorescent tube are calculated, and just need 8 * 8 * 3, i.e. 192 lines; High level and low duration that second defective of existing PWM generation chip is shift clock and latch signal can not be provided with, and the long Distance Transmission of a plurality of fluorescent tubes of signal process tends to take place to distort cause driving force to descend.

The shift LD chip for driving is present common LED chip for driving, as DM134,74HC595 etc., this chip can not produce pwm signal, but the content of outside input can be latched, driving LED shows that then the LED lamp is bright for the output high level, and low level then LED lamp is gone out, this chip generally has four control signal: clk, data, latch, enable; Data is the fluorescent tube content displayed, in the displacement of the rising edge of clk, when latch is high level data is latched into inner register, and enable drives fluorescent tube during for low level and shows.The chip price of the type is cheap, usually adopts in fluorescent tube.

Summary of the invention

The pwm signal generation method that the purpose of this invention is to provide the series multi-pixel lamp reduces the complexity of controlling cost with system.

Purpose of the present invention is achieved through the following technical solutions:

The pwm control signal generation method of series multi-pixel LED lamp comprises the steps:

(1) the displaying contents transmitter is written to driving parameters in the two-port RAM, starts the driving parameters read module then;

(2) the driving parameters read module reads driving parameters and offers each counting unit from two-port RAM, restarts PWM control output module;

(3) PWM control output module generates the pwm control signal of series multi-pixel LED lamp.

The driving parameters of described step (1) comprises grey level, shift clock high level lasting time, shift clock low duration, LATCH high level lasting time and the LATCH low duration of primary-color LED number, pixel.

The figure place of primary-color LED number is 10bits in the driving parameters of described step (1), writes at twice, writes low level earlier, writes a high position again; The figure place of the grey level of pixel, shift clock high level lasting time, shift clock low duration, LATCH high level lasting time and LATCH low duration is 8bits, write-once.

Described step (2) driving parameters read module reads configuration parameter and offers each counting unit and comprise the steps: from two-port RAM

(1) strobe pin of address multiplex module is set, address signal is changed to low level, the address wire of two-port RAM is connected with the driving parameters read module

(2) address is set, read driving parameters successively and output to each port, specifically be the number that reads primary-color LED successively, read grey level, read the shift clock high level lasting time, read the shift clock low duration, read the latch signal high level lasting time, read the latch signal low duration;

(3) reset the strobe pin of address multiplex module, the address wire of two-port RAM is connected with PWM control output module.

The pwm control signal that described step (3) PWM control output module generates series multi-pixel LED lamp comprises the steps:

(1) address ram is set to the count value of primary-color LED counter, reads the video data among the RAM;

(2) count value with video data and gray scale counter compares, if the former is greater than the latter, and PWM data output high level, otherwise output low level;

(3) the PWM clock signal is put high level, open public counter, high level lasting time is counted;

(4) the PWM clock signal is put low level, open public counter, low duration is counted;

(5) start the primary-color LED rolling counters forward once, judge that whether the LED counting arrives maximum, as for not, then gets back to step (1); As for being that then with the zero setting of LED count value, latch signal is put high level, opens public counter and counts latching high level lasting time; And latch signal put low level, open public counter and count latching low duration;

(6) start the densitometer rolling counters forward once, judge whether the gray scale counter count down to maximum, as for being, then with the zero setting of gray scale counter.

With respect to prior art, the present invention has following advantage and technique effect:

1. debugging is simple, driving parameters can outside be imported, be applicable to different shift LD chips and fluorescent tube requirement, the driving parameters that present existing PWM generates chip can't be revised, and driving parameters of the present invention can be written in the two-port RAM by the outside, read by the driving parameters read module, promptly driving parameters can be adjusted as required again;

2. with low cost, all use a PWM to generate chip controls with respect to each fluorescent tube, the present invention drives a plurality of fluorescent tubes simultaneously with a controller, and concrete data preferably are provided here, and on average the driving cost of each fluorescent tube greatly reduces;

3. simple in structure, few with the line of light fixture, PWM generates a plurality of fluorescent tubes of chip parallel drive relatively, has n pixel just to need 4n bar PWM control line, and is connected in series between PWM generation module of the present invention and the fluorescent tube, only needs 4 control lines.

Description of drawings

Fig. 1 is a PWM generation method exemplary construction formula intention of using series multi-pixel LED lamp of the present invention.

Fig. 2 is the overall structure schematic diagram of series multi-pixel LED lamp PWM control module.

Fig. 3 is the workflow block diagram of driving parameters read module.

Fig. 4 is the workflow block diagram of PWM control output module.

Embodiment

Below in conjunction with drawings and Examples the present invention is done to describe further.But embodiments of the present invention are not limited thereto.

Fig. 1 has provided the PWM generation method exemplary construction formula intention of using series multi-pixel LED lamp of the present invention.As shown in Figure 1, its circuit comprises displaying contents transmitter 1, programmable gate array (FPGA) 2 and the LED fluorescent tube 3 that has the shift LD chip for driving.The shift register model has DM134,74HC595 etc.Programmable gate array 2 one ends link to each other with content transmit control device 1, and the LED fluorescent tube that has the shift LD chip for driving 3 that the other end is connected with many groups respectively links to each other.After programmable gate array 2 receives the data of content transmit control device 1, be saved among its inner RAM, produce pwm control signal then, send fluorescent tube to.Content transmitter 1 can have data by ARM etc. and read with the chip and the module of write-in functions and form, as ARM720T, displaying contents can be read from storage chips such as SD card and send to FPGA by serial peripheral interface (SPI) again, also can data be sent from network interface by PC, use network interface card physical chip (as the RTL8201 of realtek) sends FPGA to by Media Independent Interface (MII) after receiving again.。Programmable gate array 2 can be by the FPGA of the cyclone series of altera company, and as EP2C5 etc., this devices use lookup table technology generates digital system according to user's schematic diagram or hardware description language, and its implementation procedure is as follows:

1, with VHDL (Very High Speed Integrated Circuit Hardware DescriptionLanguage, the hardware description language of very high speed integrated circuit) or schematic diagram circuit system is described;

2, the integrated circuit (IC) design integrated software Synplify with Synplicity company carries out comprehensively the hardware circuit that VHDL describes, and obtaining with the model of altera corp is the corresponding net meter file of FPGA of EP2C5;

3, the FPGA design with altera corp realizes that software QuartusII carries out placement-and-routing and extracts delayed data the net table that obtains;

4, the modelsim with mentor company carries out sequential emulation;

5, the FPGA design with altera corp realizes that software QuartusII downloads to hardware configuration information on the above-mentioned FPGA (model EP2C5).

Above-mentioned programmable gate array 2 is realized the function of a plurality of serially connected lamp tubes of control according to each module of the content generation PWM maker that downloads.Fig. 2 has provided the overall structure of series multi-pixel LED lamp PWM generation module, comprises two-port RAM 21, address multiplex module 22, and driving parameters read module 23, PWM controls output module 24, primary-color LED counter 25, gray scale counter 26 and public counter 27.Two-port RAM 21 is connected with driving parameters read module 23, address multiplex module 22 and PWM control output module 24 respectively; Driving parameters read module 23 also is connected with address multiplex module 22, gray scale counter 26 and primary-color LED counter 25 respectively; PWM control output module 24 also is connected with address multiplex module 22, public counter 27, gray scale counter 26 and primary-color LED counter 25 respectively.

Two-port RAM 21 is used for storing driver parameter and video data, two ports are arranged, all data can be write from two ports and to preserve and to read, content transmitter 1 writes video data from a port, PWM control output module 24 is read video data from another port and is produced pwm signal, and the two-port RAM chip id T7132 of its pin and function and American I DT company together; Displaying contents among the RAM is a unit with the pixel primary colours, by red (R), green (G), and the sequential loop of blue (B), promptly the data of R are deposited in first address, and the data of G are deposited in second address, the 3rd data that B is deposited in the address, by that analogy.Address multiplex module 22 is used for the gating of driving parameters read module 23 and PWM control output module 24 and two-port RAM address wire, its function and pin are with mux chip CD4053 together, gating is by 23 controls of driving parameters read module, during system works, driving parameters read module 23 is connected with the two-port RAM address, after parameter reads and finishes, PWM control output module 24 is connected with the two-port RAM address wire.

Primary-color LED counter 25 is down counters, is used for the number to primary-color LED, and promptly Yi Wei number of times is counted.Supposing n primary-color LED of maker band, at first export the data of n primary-color LED during displacement, is n-1 then, n-2 ... 1, this counter can be written into initial value, and the outside enables, and its function and pin and counter chip 8253 are similar.

The counting mode employing of gray scale counter 26 is successively decreased and incremental manner all can, adopt in this example and increase progressively counting mode, this counter is counted the gray-scale displayed rank, and count value offers PWM control output module, compares with displays content data, if the former is greater than the latter, PWM data output high level, otherwise output low level, this counter can be written into initial value, the outside enables, and its function and pin and counter chip 8253 are similar.

The counting mode employing of public counter 27 is successively decreased and incremental manner all can, adopt in this example and increase progressively counting mode, this counter is to high level and the low duration counting of requirement to being shifted and latching according to driving parameters, this counter can be written into initial value, the outside enables, its function and pin and 8253 similar.

In the present embodiment, the pwm control signal generation method of series multi-pixel LED lamp comprises the steps:

(1) the displaying contents transmitter is written to driving parameters in the two-port RAM, starts the driving parameters read module then;

(2) the driving parameters read module reads driving parameters and offers each counting unit from two-port RAM, restarts PWM control output module;

(3) PWM control output module generates the pwm control signal of series multi-pixel LED lamp.

Above-mentioned steps (1) displaying contents transmitter is written to driving parameters in the two-port RAM, is that the A port by two-port RAM writes driving parameters in order: primary-color LED number (figure place is 10bits), grey level (figure place is 8bits), shift clock high level lasting time (figure place is 8bits), shift clock low duration (figure place is 8bits), LATCH high level lasting time (figure place is 8bits), LATCH low duration (figure place is 8bits).Above driving parameters writes outer (write low level earlier, write a high position again) at twice except primary-color LED number figure place is 10bits, and all the other parameter bit number averages are 8bits, write-once.Driving parameters writes in strict accordance with said sequence, will start the driving parameters read module after finishing writing, and a period of time of delaying time then writes video data by the A port again, and time-delay length is greater than and runs through the required time span of driving parameters.

Fig. 3 has provided the workflow block diagram of driving parameters read module 23.As shown in Figure 3, above-mentioned steps (2) at first is provided with the strobe pin of address multiplex module, and address signal is changed to low level, makes the address wire of two-port RAM be connected (step 231) with the driving parameters read module; The address is set then, read driving parameters successively and output to each port, specifically be the number that reads primary-color LED successively, read grey level, read the shift clock high level lasting time, read the shift clock low duration, read the latch signal high level lasting time, read the latch signal low duration (step 232～237); After parameter reads and finishes, reset the strobe pin of address multiplex module, make the address wire of two-port RAM be connected (step 238) with PWM control output module.

Fig. 4 has provided the workflow block diagram of PWM control output module 24.As shown in Figure 4, the pwm control signal that above-mentioned steps (3) PWM control output module generates series multi-pixel LED lamp comprises the steps: that at first address ram is set to the primary-color LED count value, reads the video data (step 241) among the RAM; Count value with video data and gray scale counter compares then, if the former is greater than the latter, and PWM data output high level, otherwise output low level (step 242); Subsequently the PWM clock signal is put high level, open public counter,, again the PWM clock signal is put low level, open public counter, low duration is counted (step 244) high level lasting time counting (step 243); Start the primary-color LED rolling counters forward once, judge whether the primary-color LED counter arrives maximum,, then get back to step 241 as for not; As for being that then with the zero setting of primary-color LED count value, latch signal is put high level, opens public counter and counts (step 245～247) to latching high level lasting time; Subsequently latch signal is put low level, open public counter and count (step 248) latching low duration; Start the densitometer rolling counters forward once, judge whether the gray scale counter count down to maximum, as for being, then with the zero setting of gray scale counter (step 249～2410).

As mentioned above, just can realize the present invention preferably.

Claims (4)

1. the pwm control signal generation method of series multi-pixel LED lamp is characterized in that comprising the steps:

(1) the displaying contents transmitter is written to driving parameters in the two-port RAM, starts the driving parameters read module then;

(2) the driving parameters read module reads driving parameters and offers each counting unit from two-port RAM, restarts PWM control output module;

(3) PWM control output module generates the pwm control signal of series multi-pixel LED lamp; Concrete steps are:

A, address ram are set to the count value of primary-color LED counter, read the video data among the RAM;

B, relatively with the count value of video data and gray scale counter, if the former is greater than the latter, PWM data output high level, otherwise output low level;

C, the PWM clock signal is put high level, open public counter, high level lasting time is counted;

D, the PWM clock signal is put low level, open public counter, low duration is counted;

E, startup primary-color LED rolling counters forward once judge that whether the LED counting arrives maximum, as for not, then gets back to step a; As for being that then with the zero setting of LED count value, latch signal is put high level, opens public counter and counts latching high level lasting time; And latch signal put low level, open public counter and count latching low duration;

F, start the densitometer rolling counters forward once, judge whether the gray scale counter count down to maximum, as for being, then with the zero setting of gray scale counter.

2. the pwm control signal generation method of series multi-pixel LED lamp according to claim 1, the driving parameters that it is characterized in that described step (1) comprises grey level, shift clock high level lasting time, shift clock low duration, LATCH high level lasting time and the LATCH low duration of primary-color LED number, pixel.

3. the pwm control signal generation method of series multi-pixel LED lamp according to claim 2 is characterized in that the figure place of primary-color LED number in the driving parameters of described step (1) is 10bits, writes at twice, writes low level earlier, writes a high position again; The figure place of the grey level of pixel, shift clock high level lasting time, shift clock low duration, LATCH high level lasting time and LATCH low duration is 8bits, write-once.

4. the pwm control signal generation method of series multi-pixel LED lamp according to claim 1 is characterized in that described step (2) driving parameters read module reads configuration parameter and offers each counting unit and comprise the steps: from two-port RAM

(1) strobe pin of address multiplex module is set, address signal is changed to low level, the address wire of two-port RAM is connected with the driving parameters read module;

(2) address is set, read driving parameters successively and output to each port, specifically be the number that reads primary-color LED successively, read grey level, read the shift clock high level lasting time, read the shift clock low duration, read the latch signal high level lasting time, read the latch signal low duration;

(3) reset the strobe pin of address multiplex module, the address wire of two-port RAM is connected with PWM control output module.

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