CN202887673U

CN202887673U - High-precision LED screen-display constant-current drive circuit

Info

Publication number: CN202887673U
Application number: CN2012203558656U
Authority: CN
Inventors: 胥锐; 冉建桥; 郭灿
Original assignee: SINOTECH MIXIC ELECTRONICS CO Ltd
Current assignee: SINOTECH MIXIC ELECTRONICS CO Ltd
Priority date: 2012-07-23
Filing date: 2012-07-23
Publication date: 2013-04-17
Anticipated expiration: 2022-07-23
Also published as: CN103578406B; CN103578406A

Abstract

The utility model discloses a high-precision LED screen-display constant-current drive circuit. The utility model relates to a drive circuit structure and specifically relates to an LED screen-display drive circuit. An output terminal of a 16-bit shifting register circuit is connected with a 16-bit latch circuit. The 16-bit shifting register circuit converts serial input data to parallel data and inputs into the 16-bit latch circuit. An input signal IN1 of the 16-bit shifting register circuit is the serial input data from an LED screen-display main control chip and fits a clock signal IN2. An output terminal of the 16-bit latch circuit is connected with a current output drive circuit. The 16-bit latch circuit inputs the signal to the current output drive circuit. The current output drive circuit is connected with a constant-current control circuit. The constant-current control circuit is connected with a current trimming circuit. The utility model aims to provide the high-precision LED screen-display constant-current drive circuit that adopts standard SSOP24 packaging and is used for substituting a universal drive device used for a single- double-color LED screen.

Description

High precision LED screen display constant-current drive circuit

Technical field

The utility model relates to driving circuit structure, is specifically related to LED screen display driving circuit.

Background technology

Single dual-colored LED display screen now, the luminous common employing of driving LED be general-purpose chip 74HC595,74HC595 has 8 and latchs, the functions such as string and shift register and ternary output, electric current maximum output in every road can reach 35mA, shown in Fig. 1.It is simple to have circuit structure with 74HC595 as led drive circuit, the advantage such as data rate is fast.But its shortcoming is obvious too, and at first interchannel output current differs greatly and do not possess constant current function, has affected the display effect of LED screen and the serviceable life of LED.Its subchannel output current can not be adjusted, and does not also possess high voltage performance.Because chip output current can not adjust, the overall brightness of LED screen can't be adjusted, simultaneously because the normally independent 5V Power supply of chip, lack support to high pressure will limit on the output channel can series LED number.

The utility model content

The utility model provides a kind of high precision LED screen display constant-current drive circuit, the purpose of this utility model provides a kind of high precision LED screen display constant-current drive circuit, the SSOP24 encapsulation of employing standard is in order to replace the general driving device that uses at single dual-colored LED screen at present.

The utility model proposes a kind of circuit design technique and realize that high-precision LED constant current drives, this technology is included in to be introduced electric current and trims circuit and constant-current control circuit in traditional driving chip.Electric current trims circuit and can minimize so that flow through the current difference of any two LED on the screen, constant-current drive technology can guarantee that electric current that the every LEDs on the screen flows through is not with external environment (supply voltage when opening, temperature etc.) change and change, by an outer meeting resistance, output current can also arrange arbitrarily between 3mA-45mA simultaneously.

For addressing the above problem, the utility model adopts following technical scheme: high precision LED screen display constant-current drive circuit, it is characterized in that, comprise that electric current trims circuit (110), constant-current control circuit (120), electric current output driving circuit (130), 16 latch circuits (140) and 16 bit shift register circuit (150); 16 bit shift register circuit (150) output terminals connect 16 latch circuits (140), 16 bit shift register circuit (150) are converted to parallel data with serial input data, be input to 16 latch circuits (140), the input signal IN1 of 16 bit shift register circuit (150) is the serial input data from LED screen display main control chip, cooperates clock signal IN2; 16 latch circuits (140) output terminal connects electric current output driving circuit (130), and 16 latch circuits (140) input to electric current output driving circuit (130) with signal; Electric current output driving circuit (130) connects constant-current control circuit (120), and constant-current control circuit (120) connects electric current and trims circuit (110).

The utility model is 16 high precision LED constant-current drive circuit chips, its technical characterstic is as follows: 1. the difference that proposes to reduce by the mode that the chip internal electric current trims output current between chip and the chip, and designed a kind of electric current and trimmed circuit (Fig. 2), this circuit can be proofreaied and correct output current in 10% scope, proofread and correct output current deviation that chip later can guarantee any passage of any chip less than 3% by test, promoted greatly luminous consistance and the display effect of display screen.2. design a kind of constant-current control circuit (Fig. 3), when this circuit can guarantee that driving passage opens, the current constant that flows through the LED lamp was constant.3. design one based on 16 passage high precision LED constant-current driven chips (Fig. 4) of technical scheme 1 and technical scheme 2, adopt the SSOP24 encapsulation of standard to substitute original general-purpose chip take 74HC595 as representative with this chip.

Description of drawings

Fig. 1 is the circuit diagram of background technology scheme;

Fig. 2 is the utility model block diagram;

Fig. 3 is that electric current trims circuit diagram among Fig. 2;

Fig. 4 is constant-current control circuit figure among Fig. 2.

Symbol description among the figure: high precision LED screen display constant-current drive circuit 100, electric current trim circuit 110, constant-current control circuit 120, electric current output driving circuit 130,16 latch circuits 140,16 bit shift register circuit 150.

Embodiment

The below is described in detail the utility model with best embodiment.

As shown in Figure 2, high precision LED screen display constant-current drive circuit comprises that electric current trims circuit (110), constant-current control circuit (120), electric current output driving circuit (130), 16 latch circuits (140) and 16 bit shift register circuit (150); 16 bit shift register circuit (150) output terminals connect 16 latch circuits (140), 16 bit shift register circuit (150) are converted to parallel data with serial input data, be input to 16 latch circuits (140), the input signal IN1 of 16 bit shift register circuit (150) is the serial input data from LED screen display main control chip, cooperates clock signal IN2; The input signal IN3 of 16 latch circuits (140) and IN4 are respectively latch clock signal and the enable signal from main control chip; 16 latch circuits (140) output terminal connects electric current output driving circuit (130), 16 latch circuits (140) input to electric current output driving circuit (130) with signal, and output channel is opened or closed to the signal that electric current output driving circuit (130) provides according to latch; Electric current output driving circuit (130) connects constant-current control circuit (120), and constant-current control circuit (120) connects electric current and trims circuit (110); Constant-current control circuit (120) guarantees that the electric current of opening passage keeps constant, and electric current trims circuit (110) and guarantees that the channel current deviation reduces to minimum between chip and the chip.

As shown in Figure 3, the resistor network that four resistance (R1, R2, R3, R4) consist of has consisted of electric current with amplifier (AMP0) and has trimmed circuit (110), four resistance (R1, R2, R3, R4) parallel connection, switch of each resistance series connection, switch ground connection; The parallel connected end of four resistance connects the input end of amplifier (AMP0); Parallel resistance (R0) between the input and output side of amplifier (AMP0).

The input signal of this circuit is from the reference voltage that self produces, i.e. BANDGAP circuit among Fig. 3.Output signal is as the input signal VREF1 of constant-current control circuit.When chip testing, can adjust the conducting cut-off state of switch S 1-S4 by the output current sampling to chip, thereby change the voltage of VREF1.VREF1 will react on the output current of chip as the input voltage of constant current control, thereby realize trimming output current.

As shown in Figure 4, described constant-current control circuit (120) comprises four amplifiers (AMP1, AMP2, AMP3, AMP4); Resistance (R5) connects amplifier (AMP1) input end and ground wire; The output terminal of amplifier (AMP1) is connected NMOS4 by semiconductor (PMOS1) with semiconductor) connection amplifier (AMP2) input end, semiconductor (NMOS4) contact resistance (R5); Amplifier (AMP2) output terminal connects respectively the input end of amplifier (AMP3) and amplifier (AMP4) by semiconductor (PMOS3), and semiconductor (PMOS2) is connected PMOS3 with semiconductor) connect; Amplifier (AMP3) is connected AMP4 with amplifier) output terminal connect respectively three semiconductors (NMOS1, NMOS2, NMOS3), semiconductor (NMOS1) connects semiconductor (PMOS3).

The input signal of this circuit trims the output VREF1 of circuit from electric current.Because the clamping action of amplifier AMP1, added voltage is VREF1 on the resistance R 5, and the electric current that flow through resistance R 5 this moment is I=VREF1/R5.PMOS1 and PMOS2 consist of classical current-mirror structure, because the clamping action of amplifier AMP2, the grid leak step voltage of PMOS2 equals the drain-to-gate voltage of PMOS1, and the electric current that flows through so PMOS2 that is to say the electric current of resistance R 5 with regard to being equal to the electric current that flows through PMOS1, and this electric current flows through NMOS1 simultaneously.NMOS1 and NMOS2 consist of again classical current-mirror structure, simultaneously because the effect of amplifier AMP3 and AMP4, the drain voltage of NMOS1 and NMOS2 falls and is equal to VREF2, the electric current that flows through so NMOS2 then depends on the ratio of the breadth length ratio of NMOS2 and NMOS1 fully, the ratio of the breadth length ratio of the relative NMOS1 of breadth length ratio of setting NMOS2 is K, and the electric current that flows through so NMOS2 that is to say that the output current of passage equals: Iout=VREF1*K/R5.NMOS3 has adopted the high-voltage MOS pipe structure, and the voltage endurance capability that has both promoted chip output has also guaranteed the constant current ability of passage simultaneously.In order to obtain higher precision, R5 adopts outer meeting resistance, and the value that simultaneously changes as can be known resistance R 5 by the output current formula can also be adjusted the size of output current.

It should be noted that at last: obviously, above-described embodiment only is for the utility model example clearly is described, and is not the restriction to embodiment.For those of ordinary skill in the field, can also make other changes in different forms on the basis of the above description.Here need not also can't give all embodiments exhaustive.And the apparent variation of being amplified out thus or change still are among the protection domain of the present utility model.

Claims

1. high precision LED screen display constant-current drive circuit, it is characterized in that, comprise that electric current trims circuit (110), constant-current control circuit (120), electric current output driving circuit (130), 16 latch circuits (140) and 16 bit shift register circuit (150); 16 bit shift register circuit (150) output terminals connect 16 latch circuits (140), 16 bit shift register circuit (150) are converted to parallel data with serial input data, be input to 16 latch circuits (140), the input signal IN1 of 16 bit shift register circuit (150) is the serial input data from LED screen display main control chip, cooperates clock signal IN2; 16 latch circuits (140) output terminal connects electric current output driving circuit (130), and 16 latch circuits (140) input to electric current output driving circuit (130) with signal; Electric current output driving circuit (130) connects constant-current control circuit (120), and constant-current control circuit (120) connects electric current and trims circuit (110), and described high precision LED screen display constant-current drive circuit adopts the SSOP24 encapsulation of standard.

2. high precision LED screen display constant-current drive circuit as claimed in claim 1, it is characterized in that, the resistor network that N, the second resistance, the 3rd resistance, the 4th resistance consist of has consisted of electric current with amplifier (AMP0) and has trimmed circuit (110), the first resistance, the second resistance, the 3rd resistance, the parallel connection of the 4th resistance, switch of each resistance series connection, switch ground connection; The parallel connected end of four resistance connects the input end of amplifier (AMP0); Parallel resistance the 6th resistance between the input and output side of amplifier (AMP0).

3. high precision LED screen display constant-current drive circuit as claimed in claim 1 is characterized in that described constant-current control circuit (120) comprises the first amplifier, the second amplifier, the 3rd amplifier, the 4th amplifier; The 5th resistance connects the first amp.in and ground wire; The output terminal of the first amplifier is connected NMOS4 by the first semiconductor with semiconductor) connect the second amp.in, semiconductor (NMOS4) connects the 5th resistance; The second amplifier out connects respectively the input end of the 3rd amplifier and the 4th amplifier by the 3rd semiconductor, and the second semiconductor connects with the 3rd semiconductor; The output terminal of the 3rd amplifier and the 4th amplifier connects respectively the 4th semiconductor, the 5th semiconductor, the 6th semiconductor, and the 4th semiconductor connects the 3rd semiconductor.