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KR-102963379-B1 - CONSTANT CURRENT DRIVIER AND METHOD FOR CURRENT CORRECTION THEREOF

KR102963379B1KR 102963379 B1KR102963379 B1KR 102963379B1KR-102963379-B1

Abstract

The present embodiment provides a technology for precisely controlling the LED driving current using microcurrent correction data stored in memory in LED driving.

Inventors

  • 김지환
  • 김장수

Assignees

  • 주식회사 엘엑스세미콘

Dates

Publication Date
20260512
Application Date
20211203

Claims (15)

  1. A reference current source that supplies a reference current; A memory that stores microcurrent correction data determined by the difference between the target current and the output current before correction via a memory access signal; and A current control circuit that is controlled via a circuit control signal, generates an output current corresponding to the reference current, and supplies a corrected output current to a channel based on the microcurrent correction data stored in the memory; The above current control circuit includes a current mirror that receives the reference current and generates a mirroring current, and a fine correction circuit that corrects the mirroring current based on fine current correction data received from the memory. The current mirror comprises a first switch for applying a reference current, a first transistor connected in series with the first switch and having a reference current applied to its gate terminal, a second transistor interconnected with the first transistor and its gate terminal, a second switch disposed between the gate terminal of the first transistor and the gate terminal of the second transistor, and a capacitor connected between the second switch and the gate terminal of the second transistor. A constant current driving device in which the first switch and the second switch are switched by the circuit control signal, and the second transistor supplies output current to the channel.
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  4. In paragraph 1, The above current mirror further comprises a third transistor disposed between the first switch and the first transistor, a fourth transistor connected in series to the channel side of the second transistor, and an operational amplifier that receives a voltage formed between the first transistor and the third transistor and a voltage formed between the second transistor and the fourth transistor and outputs it to the gate terminal of the fourth transistor.
  5. In paragraph 1, A constant current driving device that corrects the mirroring current by adjusting the current of the first variable current source and the current of the second variable current source based on the micro-current correction data, wherein the above-mentioned fine correction circuit includes a first variable current source and a second variable current source.
  6. In paragraph 5, The first variable current source and the second variable current source are controlled digitally, and The above microcurrent correction data is a digital code for controlling the first variable current source and the second variable current source, a constant current driving device.
  7. In paragraph 1, The above memory access signal is a constant current driving device comprising a data signal, a clock signal, a flag signal indicating start and end, and an enable signal.
  8. In paragraph 1, The above current control circuits are k in number, corresponding to k channels (k is a natural number greater than or equal to 2), and The above memory is a constant current driving device that stores microcurrent correction data corresponding to each of k channels.
  9. In paragraph 8, A constant current driving device in which the memory access signal and the circuit control signal are input through all or part of the k common pins corresponding to the k channels.
  10. In Paragraph 9, A constant current driving device that operates in normal mode, wherein a circuit control signal is applied to one of the k common pins, and a current control circuit corresponding to the common pin to which the circuit control signal is applied sets the output current.
  11. In Paragraph 10, A constant current driving device that operates in memory access mode and writes microcurrent correction data corresponding to each of the k channels to the memory through the memory access signal input to n common pins (where n is an integer greater than or equal to 1 and less than or equal to k) among the k common pins.
  12. In Paragraph 11, A constant current driving device wherein the above k common pins include a first common pin to a fourth common pin, wherein a data signal is input to the first common pin, a clock signal is input to the second common pin, a start and end flag signal is input to the third common pin, and a write enable signal is input to the fourth common pin.
  13. A data loading step for loading microcurrent correction data stored in memory into a current control circuit; An output current measurement step for measuring the output current output to the channel based on the above microcurrent correction data; An output current determination step for determining whether the above output current is the same as the target current; and When the output current is not equal to the target current, the method includes a microcurrent correction data writing step of writing microcurrent correction data determined by the difference between the target current and the output current to the memory; A microcurrent correction method for a constant current driving device, which repeats the microcurrent correction data entry step, the data loading step, the output current measurement step, and the output current determination step until the output current and the target current are the same.
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  15. In Paragraph 13, For k channels (where k is a natural number greater than or equal to 2), a first channel correction step in which microcurrent correction data is determined for a first channel among the k channels and microcurrent correction is completed; and A method for microcurrent correction of a constant current driving device, comprising: a remaining channel correction step of sequentially performing microcurrent correction on other channels among the k channels for which microcurrent correction has not been completed.

Description

Constant Current Driver and Method for Current Correction Thereof The present invention relates to a constant current driving device and a current correction method thereof. An LED (Light Emitting Diode) is a semiconductor device that emits light through the electroluminescence effect when forward voltage is applied. It is used in a wide variety of applications due to its long lifespan and ability to generate large amounts of light energy with low power consumption. LEDs can be used for various purposes. For example, LEDs can be utilized as backlights for liquid crystal displays (LCDs). In this case, since the brightness of the LED used as a backlight is nearly linearly proportional to the current flowing through it, a precise constant current must be supplied to the LED to obtain a constant brightness. However, the non-uniform device characteristics of LEDs and current fluctuations in the boundary regions of LED operation limit the supply of a precise constant current. Unlike volatile memory, where stored data evaporates when the power is cut off, non-volatile memory retains data even when the power is cut off. Types of non-volatile memory include ROM, flash memory, and magnetic memory. Recently, NAND flash memory, which offers relatively high speed and high integration density, has become widely used. FIG. 1 is a drawing showing a constant current driving device according to one embodiment of the present invention. Figure 2 is a diagram showing the output current according to the reference current and circuit control signal of Figure 1. Figure 3 is a diagram showing the current control circuit of Figure 1. Figure 4 is a diagram showing an example of the current mirror of Figure 3. Figure 5 is a diagram showing another example of the current mirror of Figure 3. Figure 6 is a diagram showing the fine correction circuit of Figure 3. Figure 7 is a diagram showing an example of the fine correction circuit of Figure 6. Figure 8 is a diagram showing the memory, memory access signal, and microcurrent correction data of Figure 1. Figure 9 is a diagram showing an example of the reference current, circuit control signal, output current, and memory access signal of Figure 1. FIG. 10 is a drawing showing another example of a constant current driving device according to one embodiment of the present invention. FIG. 11 is a diagram showing a common pin to which the memory access signal and circuit control signal of FIG. 10 are input. Figure 12 is a diagram showing one of the current control circuits of Figure 10. FIG. 13 is a diagram showing an example of the output current of each channel according to the common pin input of FIG. 12. Figure 14 is a diagram showing the memory, common pin, and microcurrent correction data of Figure 11. FIG. 15 is a diagram showing an example of the output current of each channel according to the common pin input of FIG. 12. Figure 16 is a diagram showing another example of the output current of each channel according to the common pin input of Figure 12. FIG. 17 is a diagram showing an example of a microcurrent correction method for a constant current driving device according to another embodiment of the present invention. FIG. 18 is a diagram showing another example of a microcurrent correction method for a constant current driving device according to another embodiment of the present invention. Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. FIG. 1 is a drawing showing a constant current driving device according to one embodiment of the present invention. Referring to FIG. 1, a constant current driving device (100) may include a reference current source (110) that supplies a reference current (Iref), a memory that stores microcurrent correction data (FCTD) determined by the difference between a target current (TI) and an output current (Io) before correction via a memory access signal (MAS), and a current control circuit (130) that is controlled via a circuit control signal (CCS), generates an output current (Io) corresponding to the reference current (Iref), and supplies a corrected output current (Io) to a channel (CH) based on the microcurrent correction data (FCTD) stored in the memory (120). The reference current (Iref) is a current that serves as a reference for generating the output current (Io), and the constant current driving device (100) can generate a high output current (Io) when the reference current (Iref) is increased, and a low output current (Io) when the reference current (Iref) is decreased. The constant current driving device (100) can determine the power supplied to the load (300) by changing the reference current (Iref). If the load (300) is a light source element, the brightness can be adjusted by controlling the reference current (Iref). Data—for example, microcurrent correction data—can be stored in the memory (120). The memory device that stores the data can be classified as a volatile m