CN112235908A - Constant current LED drive control circuit suitable for outdoor instrument - Google Patents

Abstract

The invention discloses a constant current LED drive control circuit suitable for an outdoor instrument in the technical field of integrated circuits, which comprises: a power-on reset module; the control module is connected to the power-on reset module; a constant current control module connected to the control module; a cathode drive module connected to the constant current control module and the control module; according to the invention, all parts are integrated into a single IC, the cost is low, the PCB design difficulty is simplified, a control interface is simplified after the single IC is integrated, the IO (input/output) resource of a main control device is saved, the whole machine program development difficulty is reduced, the SEG port outputs constant current, the LED brightness is not influenced by external conditions, the display effect is excellent, and the shadow eliminating module capable of being automatically closed is designed at the COM port, so that the power consumption is reduced.

Description

Constant current LED drive control circuit suitable for outdoor instrument

Technical Field

The invention relates to the technical field of integrated circuits, in particular to a constant-current LED drive control circuit suitable for an outdoor instrument.

Background

An LED is a common light emitting device, and is widely used in lighting, indicator lights, displays, and the like. In general, in the control of LED display devices used indoors, logic circuits such as 74HC138, 74HC164, 74HC273 and the like are used as controls, and buffer chips such as 74HC245 and the like which are normally driven in a smaller way are used in a driving stage. When the LED is used for outdoor instrument equipment, due to the factors such as high illumination intensity of outdoor environment and the like, high-current driving is needed, so that the LED is in a high-brightness state to ensure that the display effect is clear, and at the moment, the buffer chip with conventional small driving, such as 74HC245, can not meet the requirement of driving current.

The existing device adopts discrete devices to form a control logic, a power triode is controlled by small driving devices such as 74HC138 and the like to be used as an LED common end for driving, a power MOS tube is controlled by small driving devices such as 74HC164 and 74HC273 and the like to be used as the other end bit of an LED for driving, when the device is used, A, B, C is used as an input signal, one signal in COM 1-8 is selected to be output through 74HC138, then a CP is used as a control signal, a signal required to be output is input through a D end, and a serial D port input signal is converted into parallel data through 74HC164 groups; and then taking the E as a control signal, locking and storing an output signal of the 74HC164 group into the 74HC273 group, controlling a power tube to output and drive an LED by the output signal of the 74HC273 group, connecting a 10K omega resistor to a reference 0 potential at each port of the COM 1-8 for eliminating the shadow of the drive signal, and resetting the circuits of the 74HC164 and 74HC273 by an input signal of the port R to prevent an uncontrolled output state from being generated at the COM and SEG ports at the moment when the system starts to work.

However, the conventional device has many discrete devices, high cost, complex PCB circuit, many interfaces, many occupied main control resources, is not beneficial to the development of the whole machine program, the COM/SEG output current cannot be actively controlled, the brightness of the driving LED is influenced by the quantity and the power supply voltage of the LED which are simultaneously lightened, the display effect is poor, the shadow eliminating function is realized by discrete resistors, and current consumption and high energy consumption always exist when an effective high-level signal is output corresponding to a COM port.

Disclosure of Invention

The invention aims to provide a constant-current LED drive control circuit suitable for outdoor instruments, and aims to solve the problems that the conventional device proposed in the background art has many discrete devices, high cost, complex PCB circuits, many interfaces, more occupied main control resources, and inconvenience for whole machine program development, COM/SEG output current cannot be actively controlled, the brightness of the drive LED is influenced by the number of simultaneously lighted LEDs and power supply voltage, the display effect is poor, the shadow eliminating function is realized through discrete resistors, and current consumption and high energy consumption always exist when an effective high-level signal is output corresponding to a COM port.

In order to achieve the purpose, the invention provides the following technical scheme: a constant current LED drive control circuit suitable for outdoor instrument includes:

a power-on reset module;

a control module connected to the power-on reset module, the control module comprising:

a shift register module;

the control logic module is connected to the shift register module;

a data register set connected to the shift register module and the control logic module;

a constant current control module connected to the control module;

a cathode drive module connected to the constant current control module and the control module;

an anode drive module connected to the control module.

Preferably, the shift register module includes a plurality of first reset-end-carrying D flip-flops, a data input end of one of the first reset-end-carrying D flip-flops is connected to the DI port, and a data input end of another one of the first reset-end-carrying D flip-flops is connected to an output end of the last first reset-end-carrying D flip-flop, and then the data input ends are sequentially connected in series.

Preferably, the control logic module comprises a second D flip-flop with a reset terminal.

Preferably, the data register set includes a plurality of third D flip-flops with reset terminals.

Preferably, the cathode driving module includes:

a control circuit;

and the power NMOS tube is connected to the control circuit.

Preferably, the anode driving module includes:

a module for detecting the falling edge and outputting pulse;

the shadow eliminating control module is connected to the detection falling edge output pulse module;

and the power PMOS tube is connected with the detection falling edge output pulse module and the shadow elimination control module in parallel.

Compared with the prior art, the invention has the beneficial effects that: the invention integrates all components into a single IC, has low cost, simplifies PCB design difficulty, simplifies control interfaces after single integration, saves IO resources of main control equipment, reduces the difficulty of whole machine program development, outputs constant current at the SEG port, ensures that the LED brightness is not influenced by external conditions, has good display effect, designs a shadow eliminating module which can be automatically closed at the COM port, and reduces power consumption.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a circuit diagram of a power-on reset module according to the present invention;

FIG. 3 is a schematic diagram of a control module according to the present invention;

FIG. 4 is a signal control diagram of a control module according to the present invention;

FIG. 5 is a schematic structural diagram of a cathode driving module according to the present invention;

FIG. 6 is a schematic structural diagram of an anode driving module according to the present invention.

In the figure: the device comprises a 100 power-on reset module, a 200 control module, a 210 shift register module, a 220 control logic module, a 230 data register group, a 300 constant current control module, a 400 cathode driving module, a 410 control circuit, a 420 power NMOS tube, a 500 anode driving module, a 510 falling edge output pulse detection module, a 520 shadow elimination control module and a 530 power PMOS tube.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a constant current LED drive control circuit suitable for outdoor instruments, integrate all parts into a single IC, with low costs, simplify the PCB design difficulty, simplify the control interface after the single integration, save master control equipment IO resources, reduce the whole procedure development difficulty, SEG port constant current output, make LED luminance not influenced by external condition, there is high-quality display effect, design the module of shadow elimination that can close automatically in COM port, reduce the power consumption, please refer to figure 1, including: the power-on reset module 100, the control module 200, the constant current control module 300, the cathode driving module 400 and the anode driving module 500;

referring to fig. 1-2, a power-on reset module 100 is used to replace the function of the R port in the prior art, and generates a reset signal after power-on, resets the states of a shift register and a data latch, and avoids the state that the COM/SEG port is not controlled at the moment of power-on of the system, and because the LED array of an outdoor instrument consumes a large amount of power and interferes with the power supply very significantly, the power-on reset module is required to have higher reliability;

referring to fig. 1, 3 and 4, the control module 200 is connected to the power-on reset module 100, and the control module 200 includes:

the shift register module 210 is composed of a plurality of first D flip-flops with reset terminals, clock signals of all the first D flip-flops with reset terminals are short-circuited and controlled by a CLK port of a chip, reset signals of all the first D flip-flops with reset terminals are short-circuited and controlled by the power-on reset module 100, a data input end of a first D flip-flop with reset terminals is connected with a DI port of the chip, a data input end of a second D flip-flop with reset terminals is connected with an output of the first D flip-flop with reset terminals, and a data input end of a third D flip-flop with reset terminals is connected with an output of the second D flip-flop with reset terminals, and then the data input ends are sequentially connected in series;

the control logic module 220 is connected to the shift register module 210, the control logic module 220 includes a second D flip-flop with a reset terminal, the control logic module 220 generates a control signal by using DI and CLK signals of the chip, the control data register group 230 latches data of the shift register module 210, a clock terminal of the second D flip-flop with the reset terminal is controlled by the DI of the chip, a data terminal of the second D flip-flop with the reset terminal is controlled by the CLK of the chip, and a reset terminal of the second D flip-flop with the reset terminal is controlled by the power-on reset module 100;

the data register group 230 is connected to the shift register module 210 and the control logic module 220, the data register group 230 is composed of a plurality of third D flip-flops with reset terminals, the number of the third D flip-flops with reset terminals is the same as that of the first D flip-flops with reset terminals, the data terminal of each third D flip-flop with reset terminals in the data register group 230 is provided by the output of one shift register, clock signals of all the third D flip-flops with reset terminals in the data register group 230 are short-circuited and are controlled by the CLK port of the chip, reset signals of all the third D flip-flops with reset terminals are short-circuited and are controlled by the power-on reset module 100, based on the above modules, only 2-bit signal lines are needed to complete the LED display control, and the control mode is as follows:

1) writing the DATA DATA into the shift register by the rising edge of CLK;

2) when CLK is high, DATA appears rising;

a. loading the data of the shift register into a secondary latch;

b. according to the data of the secondary latch, the COM output, the SEG output and the constant current are modified;

3) with CLK low, DATA rising:

a. exiting the latch mode, and maintaining the latch data unchanged by the secondary latch;

b. shift writing of the second frame data may be started;

4) the data latch is divided into 3 groups, one of the data latch is used for controlling the switch of the COM port, the other two of the data latch is used for controlling the switch of the SEG port, and the other three of the data latch is used for controlling the magnitude of current output when the SEG port is opened;

each group is provided with a plurality of bits as required, for example, in the circuit shown in the embodiment, there are 64 choices of output currents of 8 COM ports, 16 SEG ports, and then the data latch needs at least 32 bits, where 8 bits are used for controlling a COM switch, 16 bits are used for controlling an SEG switch, and 8 bits are used for controlling the magnitude of the output current when the SEG port is opened;

referring to fig. 1 and fig. 3 again, the constant current control module 300 is connected to the control module 200, the constant current control module 300 is controlled by the output signal of the data latch group 230 and outputs a signal to control the current output by the cathode, the data latch group 230 outputs 4-bit data to the constant current control module as a selection signal, and different data combinations correspondingly control the SEG ports to output different fixed currents when the SEG ports are opened;

referring to fig. 1, 3 and 5, the cathode driving module 400 is connected to the constant current control module 300 and the control module 200, and the cathode driving module 400 includes:

the control circuit 410 is connected to the constant current control module 300 and the set of data latches 230;

the power NMOS 420 is connected to the control circuit 410, the cathode driving module 400 receives the output signal of the constant current control module 300 and the output signal of the data latch set 230, each bit of the data latch set 230 controls one SEG port, when receiving a logic "1", the power NMOS 420 is controlled to be turned on, when receiving a logic "0", the power NMOS 420 is controlled to be turned off, and the output signal of the constant current control module 300 passes through the control circuit 410 and is used for outputting current when the power NMOS 420 is turned on;

referring to fig. 1, 3 and 6, the anode driving module 500 is connected to the control module 200, and the anode driving module 500 includes:

the detect falling edge output pulse module 510 is connected to the set of data latches 230;

the shadow elimination control module 520 is connected to the detection falling edge output pulse module 510;

the power PMOS transistor 530 is connected to the data latch group 230, the power PMOS transistor 530 is connected in parallel to the falling edge detection output pulse module 510 and the shadow elimination control module 520, the anode driving module 500 receives the output of the data latch group 230, each data latch controls one COM port, when receiving a logic "1", the power PMOS transistor 530 is controlled to be opened, when receiving a logic "0", the power PMOS transistor 530 is controlled to be closed, when receiving a change from a logic "1" to a logic "0", the falling edge detection output pulse module 510 detects a falling edge and outputs a pulse signal of a fixed time, the shadow elimination control module 520 is controlled to operate logically, assuming that the time width of the output pulse is t, the effective time of shadow elimination is equal to the time t, the shadow control logic is closed in other times, and no power consumption exists, this part replaces the existing resistor connected between the COM port and the reference ground potential, compared with the method using the resistor in the prior art, the shadow eliminating module has the advantages of short working time and less power consumption.

While the invention has been described above with reference to an embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the various features of the embodiments disclosed herein may be used in any combination, provided that there is no structural conflict, and the combinations are not exhaustively described in this specification merely for the sake of brevity and conservation of resources. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (6)

1. The utility model provides a constant current LED drive control circuit suitable for outdoor instrument which characterized in that: the method comprises the following steps:

a power-on reset module (100);

a control module (200), the control module (200) being connected to the power-on-reset module (100), the control module (200) comprising:

a shift register module (210);

a control logic module (220), said control logic module (220) being coupled to said shift register module (210);

a set of data registers (230), the set of data registers (230) connected to the shift register module (210) and the control logic module (220);

a constant current control module (300), the constant current control module (300) being connected to the control module (200);

a cathode drive module (400), the cathode drive module (400) being connected to the constant current control module (300) and the control module (200);

an anode drive module (500), the anode drive module (500) being connected to the control module (200).

2. The constant-current LED driving control circuit suitable for the outdoor instrument according to claim 1, characterized in that: the shift register module (210) comprises a plurality of first D flip-flops with reset terminals, wherein a data input end of one of the first D flip-flops with reset terminals is connected to a DI port, and a data input end of another one of the first D flip-flops with reset terminals is connected to an output end of the last one of the first D flip-flops with reset terminals, and then the data input ends are sequentially connected in series.

3. The constant-current LED driving control circuit suitable for the outdoor instrument according to claim 1, characterized in that: the control logic module (220) comprises a second D flip-flop with a reset terminal.

4. The constant-current LED driving control circuit suitable for the outdoor instrument according to claim 1, characterized in that: the data register set (230) comprises a plurality of third reset-ended D flip-flops.

5. The constant-current LED driving control circuit suitable for the outdoor instrument according to claim 1, characterized in that: the cathode driving module (400) includes:

a control circuit (410);

a power NMOS transistor (420), wherein the power NMOS transistor (420) is connected to the control circuit (410).

6. The constant-current LED driving control circuit suitable for the outdoor instrument according to claim 1, characterized in that: the anode drive module (500) comprises:

a detect falling edge output pulse module (510);

a vanishing control module (520), the vanishing control module (520) being connected to the detected falling edge output pulse module (510);

a power PMOS transistor (530), wherein the power PMOS transistor (530) is connected in parallel with the detection falling edge output pulse module (510) and the shadow elimination control module (520).

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