A kind of LED display cell board driving circuitTechnical field
The utility model relates to a kind of driving circuit, especially relates to the driving circuit of low electromagnetic in a kind of LED display cell board.
Background technology
Light emitting diode (LED; Light Emitting Diode), be a kind of solid-state semiconductor devices, it can directly be converted into light to electricity; Owing to possess high illumination efficiency, long-lasting and small size, LED has obtained application more and more widely.The white light LEDs of the low-power consumption of about 0.1W just is being widely used on the backlight and keyboard illumination of light emitting diode LCD display panel at present, also can bring higher brightness as application such as temporary lighting or flashlamp through connecting many LEDs certainly.The High Power LED LED of 1W then is applied in camera function or the home-use illumination of supporting in the high-resolution shooting mobile phone in the dark surrounds.Except that white light LEDs, RGB (red, green, blue) light LED also often is used to strengthen color sense, and accurately suitably mixed through three kinds of colors, RGB (red, green, blue) light LED can create rich and varied color.
The application of LED more and more widely, simultaneously the type of drive of LED is also more and more abundanter.Existing nowadays, high refresh rate, high gray scale, high brightness etc. are all pursued in order to cater to market by numerous LED display manufacturer.This has just caused the drive circuit works frequency of LED display higher, thereby causes very strong electromagnetic interference (EMI), has increased the inhibition difficulty of Electro Magnetic Compatibility (EMC, Electro Magnetic Compatibility).
The utility model content
To the higher apparent in view shortcoming of electromagnetic interference (EMI) that causes of the drive circuit works frequency of traditional LED display, the utility model proposes the driving circuit of low electromagnetic in a kind of LED display cell board.
The utility model adopts following technical scheme to realize: the driving circuit of low electromagnetic in a kind of LED display cell board, and it comprises: power interface; The chip for driving of a plurality of parallel connections, the control end of each chip for driving a plurality of LED that are connected in parallel; Be used to import the data-interface of LED display video data; Be used for output shows signal, clock signal and the latch signal buffering of data-interface output are exported to each chip for driving, will control the data buffer that letter export metal-oxide-semiconductor to according to the row of interface output, output terminal, output terminal that its input end connects data-interface connect each chip for driving and metal-oxide-semiconductor respectively; Collector connects the dc power output end of power interface, the output terminal that grid connection data buffer is used to export row control letter, the metal-oxide-semiconductor that emitter connects each LED.
Wherein, be connected in series current-limiting resistance between the output terminal of the output terminal of data-interface and data buffer.
Wherein, be connected in series filter capacitor between the output terminal of data-interface and the signal ground.
Wherein, connect each chip for driving behind the dc power output end of the power interface serial connection schottky diode.
Wherein, between the anode of schottky diode and signal ground, be connected filter capacitor.
Wherein, said driving circuit is arranged between the multi-layer PCB board, and the top layer of this pcb board and bottom all select to be set to the stratum, and stratum and signal ground are through the electric capacity bridge joint, and the stratum connects the cabinet shell of LED display cell board.
Compared with prior art, the utlity model has following beneficial effect:
The utility model in driving circuit, used highly refresh, the LED chip for driving of high gray shade scale; Guaranteeing under the high prerequisite that refreshes with high gray scale; Reduced clock signal frequency as far as possible, selected suitable magnetic bead, resistance and electric capacity that signal is carried out filtering reduction noise to the unlike signal circuit through calculating and testing; And data buffer is selected 74VHC245 for use, and the voltage of its output does not receive the influence of IC supply voltage, and electromagnetic radiation is quite low; In the circuit board at driving circuit place, select to be set to the stratum in top layer and the bottom floor file, stratum and signal ground cause the LED cabinet shell with the stratum then through the electric capacity bridge joint, can reduce the electromagnetic exposure that driving circuit produces.Therefore, the driving circuit of the utility model has reached the requirement of low electromagnetic, and have circuit structure simple, realize the low advantage of cost.
Description of drawings
Fig. 1 is the circuit diagram of the utility model.
Embodiment
As shown in Figure 1; The utility model proposes the driving circuit of low electromagnetic in a kind of LED display cell board; This driving circuit comprises: the data-interface J1 that is used to import the LED display video data; Its 4 output terminals are connected in series respectively exports shows signal (SIGNAL), clock signal (CLK), latch signal (SDI) and row control signal (ROWGATE) behind current-limiting resistance R1, R2, R3 and the R4 respectively to data buffer U1, and 4 current-limiting resistance R1, R2, R3 and R4 are connected signal ground after being connected in series 4 filter capacitor C1, C2, C3 and C4 respectively; It is the chip of 74VHC245 that impact damper U1 adopts model; After shows signal (SIGNAL), clock signal (CLK), row control signal (SDI) and latch signal (ROWGATE) cushioned respectively; Its 3 output terminals will show that respectively signal (SIGNAL), clock signal (CLK) and latch signal (SDI) export the LED array of display to, and in addition 1 output terminal will be gone control signal (ROWGATE) and exported the grid of metal-oxide-semiconductor U2 to; Cooperate with row control signal (ROWGATE) controlling by metal-oxide-semiconductor U2 from the LED power supply of power interface J2 output.
Wherein, the LED array of display comprises several parallelly connected chip for driving U3 .., Un, the control end of each LED chip for driving several LEDs that are connected in parallel.
Wherein, power interface J2 has 4 output terminals, and its dc power output end output 5V direct supply is to the collector of metal-oxide-semiconductor U2, and emitter connects the anode of each LED in the LED array of display.When row control signal (ROWGATE) was high level, metal-oxide-semiconductor U2 conducting made the 5V direct supply of power interface J2 output power supply is provided for each LED, makes each LED luminous.
In addition, because each chip for driving U3 .., Un are adopted different voltage branch feedings, thus connect each chip for driving U3 .., Un behind diode D1 of the 5V dc power output end of power interface J2 serial connection, and diode D1 selects schottky diode for use.Between the anode of schottky diode D1 and signal ground, be connected filter capacitor C2.Form coupling path owing to producing distributed capacitance between the big pressure reduction circuit, so select schottky diode (about step-down 0.3V).
And; The LED display cell board is handled when the PCB layout; In the multi-layer PCB at driving circuit place, top layer and bottom select to be set to the stratum, and stratum and signal ground are through the electric capacity bridge joint; And the stratum connects the cabinet shell of LED display cell board, can reduce the electromagnetic exposure that driving circuit produces with this.
To sum up; The utility model in driving circuit, used highly refresh, the LED chip for driving of high gray shade scale; Guaranteeing under the high prerequisite that refreshes with high gray scale; Reduced clock signal frequency as far as possible, selected suitable magnetic bead, resistance and electric capacity that signal is carried out filtering reduction noise to the unlike signal circuit through calculating and testing; And data buffer is selected 74VHC245 for use, and the voltage of its output does not receive the influence of IC supply voltage, and electromagnetic radiation is quite low.Therefore, the driving circuit of the utility model has reached the requirement of low electromagnetic.
The above is merely the preferred embodiment of the utility model; Not in order to restriction the utility model; Any modification of being done within all spirit and principles at the utility model, be equal to replacement and improvement etc., all should be included within the protection domain of the utility model.