Current driving device for display screen

Abstract

The invention discloses a current driving device which is provided with an input channel and an output channel. The current driving device comprises a current source, a current mirror, an output enabling switch and a control circuit. The current source is arranged in the input channel. The current mirror is disposed between the input channel and the output channel, and is coupled to the current source. The output enabling switch is arranged in the output channel and is coupled to the current mirror. The control circuit is coupled between the input channel and the output channel for forming a feedback loop through the input channel.

Description

Technical Field

[0001] The invention relates to a current driving device, and in particular to a current driving device which can be used to drive a display screen. Background Art

[0002] Based on the demand for display quality, various display technologies have emerged, such as liquid crystal displays (LCD) and organic light emitting diodes (OLED) displays. In liquid crystal displays, the display of the picture is adjusted by adjusting the aperture ratio through liquid crystal molecules. It uses a backlight module to generate light and uses a color filter to determine the color of the display. The direct backlight module has become the mainstream backlight control method of the liquid crystal display panel because of its high contrast and low light leakage characteristics. The direct backlight module can realize local dimming operation to reduce power consumption. The direct backlight module includes a plurality of light emitting diode (LED) strings, which are arranged under the liquid crystal display pixel, wherein each light emitting diode string can be driven by a driving circuit. That is to say, the driving circuit provides current to the light emitting diode string of the backlight module to drive the light emitting diode to emit light, thereby generating the light source of the liquid crystal display.

[0003] In recent years, the resolution and refresh rate of liquid crystal display screens have gradually increased. Therefore, the current used to drive the light-emitting diodes of the backlight module is required to operate at a faster speed. In the driving circuit, an operational amplifier can be used to generate a driving current supplied to the light-emitting diode string. The operational amplifier is set to control an output component to enable and adjust the driving current to respond to the backlight control scheme required by the backlight module. However, the light-emitting diode string usually has a large number of light-emitting diodes throughout the entire panel, and these light-emitting diodes need to be able to generate high brightness, so the light-emitting diode string needs to receive a high voltage supply. In order to drive the high-voltage light-emitting diode string, the output component should be a high-voltage component, such as a high-voltage transistor. The high-voltage component can withstand the high supply voltage of the light-emitting diode string, but it needs to use additional process steps to manufacture, so it requires a higher circuit cost and has a larger load. Since the operational amplifier needs to be used to drive the high-voltage component, the response speed of the operational amplifier will be limited. Summary of the invention

[0004] Therefore, the main purpose of the present invention is to provide a new current driving device, which can be used to drive a display screen and solve the above problems.

[0005] An embodiment of the present invention discloses a current driving device having an input channel and an output channel. The current driving device includes a current source, a current mirror, an output enabling switch and a control circuit. The current source is disposed at the input channel. The current mirror is disposed between the input channel and the output channel and coupled to the current source. The output enabling switch is disposed at the output channel and coupled to the current mirror. The control circuit is coupled between the input channel and the output channel to form a feedback loop through the input channel.

[0006] Another embodiment of the present invention discloses a current driving device having an input channel and an output channel. The current driving device includes a current source, an input control transistor, a current mirror, an output enable switch and a first operational amplifier. The current source is disposed at the input channel. The input control transistor is disposed at the input channel and coupled to the current source. The current mirror is disposed between the input channel and the output channel and coupled to the input control transistor. The output enable switch is disposed at the output channel and coupled to the current mirror. The first operational amplifier includes a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the output channel, the second input terminal is coupled to the input channel, and the output terminal is coupled to the input control transistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 Schematic diagram of a two-stage current driving device.

[0008] Figure 2 Schematic diagram of a three-stage current driving device.

[0009] Figure 3 FIG. 1 is a schematic diagram of a current driving device according to an embodiment of the present invention.

[0010] Figure 4 A detailed implementation of the current driving device is shown.

[0011] Figure 5 Another detailed embodiment of the current driving device is shown.

[0012] Figure 6 Another detailed implementation of the current driving device is shown.

[0013] The reference numerals are described as follows:

[0014] 10. Dual-stage current driver

[0015] M1~M4 transistors

[0016] OP1, OP2 operational amplifiers

[0017] 102, 302 Current Source

[0018] 104, 310 LED load

[0019] CH_IN Input channel

[0020] CH_OUT Output channel

[0021] VDD Power supply voltage

[0022] I_REF Reference current

[0023] VREF reference voltage

[0024] I_LED drive current

[0025] V1, V2, VP, VG voltage

[0026] OUT_EN Output enable signal

[0027] VLED High power supply voltage

[0028] VOUT Output voltage

[0029] 20 Three-level current drive device

[0030] M5 output transistor

[0031] 30 Current drive device

[0032] 304 Current Mirror

[0033] 306 Output Enable Switch

[0034] 308 Control Circuit

[0035] 312, 612 Bias Generator DETAILED DESCRIPTION

[0036] There are two driving schemes for a current driving device to drive a light emitting diode (LED) string of a backlight module of a liquid crystal display (LCD): a two-stage scheme and a three-stage scheme. Figure 1 FIG. 1 is a schematic diagram of a dual-stage current driving device 10. The dual-stage current driving device 10 includes a current source 102, transistors M1 to M4, and operational amplifiers OP1 and OP2. A light-emitting diode load 104 driven by the dual-stage current driving device 10 is also shown in FIG. Figure 1For ease of explanation.

[0037] The dual-stage current driving device 10 includes an input channel CH_IN and an output channel CH_OUT, wherein a current source 102 and transistors M1 and M2 are located in the input channel CH_IN, and transistors M3 and M4 are located in the output channel CH_OUT. The current source 102 can receive a power supply voltage VDD to generate a reference current I_REF on the input channel CH_IN. The operational amplifier OP1 can appropriately control the operating voltage of the input channel CH_IN, such as controlling a voltage V1 of the input channel CH_IN to be equal to a reference voltage VREF. The transistors M2 and M3 can form a current mirror, and based on the control of the operational amplifier OP2, the current mirror can generate a driving current I_LED according to the reference current I_REF. More specifically, the output terminal of the operational amplifier OP2 is coupled to the gate terminal of the transistor M4, and the source terminal of the transistor M4 is further coupled to the negative input terminal of the operational amplifier OP2 to form a feedback loop. This feedback loop can control the voltage V2 to track the voltage V1, so that when the feedback loop is stable, the voltage V2 approaches the voltage V1. In this case, the current mirror formed by transistors M2 and M3 can be used to generate an accurate driving current I_LED. Through proper design of the current mirror, the driving current I_LED used to drive the LED load 104 can be accurately a specific multiple of the reference current I_REF.

[0038] In addition, the transistor M4 is also controlled by an output enable signal OUT_EN, which can be generated by a pulse width modulation (PWM) controller to turn on the output of the driving current I_LED by controlling a good duty cycle, thereby controlling the brightness of the LED string. The transistor M4 is coupled to the LED string in the LED load 104. Since the LED string receives a voltage supply of a high power supply voltage VLED (which is much higher than the power supply voltage VDD of the integrated circuit (IC) used for the dual-stage current driving device 10), the transistor M4 should be implemented by a high-voltage component that can withstand the high power supply voltage VLED of the LED load 104.

[0039] However, since transistor M4 is a high voltage component with a large load, it takes a long time for the feedback loop to stabilize, that is, the operational amplifier OP2 needs to use a lot of time to drive the voltage V2 to its target value. As mentioned above, the resolution and refresh rate of the liquid crystal display screen are gradually improved, and the improved resolution and / or refresh rate causes the available scanning time of each row of pixels to decrease, which means that the scanning speed requirement of each row of pixels increases. Since the operational amplifier OP2 of the dual-stage current driving device 10 is used to drive the high voltage transistor M4, the response speed of the operational amplifier OP2 may not be sufficient to support the increased scanning speed requirement.

[0040] Therefore, a three-level driving scheme can be used to solve this problem. Figure 2 Schematic diagram of a three-level current driving device 20. The circuit structure of the three-level current driving device 20 is similar to that of the two-level current driving device 10, so signals or components with similar functions are represented by the same symbols. The difference between the three-level current driving device 20 and the two-level current driving device 10 is that the three-level current driving device 20 further includes an output transistor M5 for coupling to the light-emitting diode load 104.

[0041] More specifically, in the three-stage current driving device 20, the output terminal of the operational amplifier OP2 is still coupled to the gate terminal of the transistor M4 to form a feedback loop through the transistor M4 and the output channel CH_OUT. The output transistor M5 is coupled between the transistor M4 and the light-emitting diode load 104, and an additional circuit stage can be formed to realize the three-stage structure. The output transistor M5 receives the control of the output enable signal OUT_EN to turn on the output of the driving current I_LED by controlling a good duty cycle. Since the output transistor M5 is coupled to the light-emitting diode load 104, it can be realized by a high-voltage component.

[0042] On the other hand, transistors M1-M4 can be implemented by low-voltage or medium-voltage components. In this case, the feedback loop formed by the operational amplifier OP2 and the transistor M4 does not need to face the huge light-emitting diode load 104, wherein the load of the transistor M4 is much smaller than the load of the high-voltage output transistor M5. Therefore, in the three-stage current driving device 20, the operational amplifier OP2 is used to stabilize the loop at a much faster speed than the two-stage current driving device 10. Since the feedback loop is quickly stabilized, the driving current I_LED on the output channel CH_OUT can quickly reach its target level.

[0043] In this example, the output transistor M5 is controlled by the output enable signal OUT_EN and acts as a simple switch. The output enable signal OUT_EN is a digital signal that can be quickly switched from a low level to a high level, so the turn-on speed of the output transistor M5 is faster than the turn-on speed of the transistor M4 in the dual-stage current driving device 10. For example, after the transistor M4 at the output end is turned on by the output enable signal OUT_EN, the dual-stage current driving device 10 needs one or several microseconds of processing time to make the driving current I_LED ready, while the three-stage current driving device 20 only needs hundreds of nanoseconds to make the driving current I_LED ready.

[0044] Although the three-stage current driving device 20 has a faster operating speed, it has one more transistor than the two-stage current driving device 10. In addition, when the current is output, the output voltage VOUT of the current driving device should be as low as possible to reduce the power consumption of the current driving device. In order to maintain the minimum operating voltage level of VOUT, the area of ​​transistors M4 and M5 in the three-stage current driving device 20 should be much larger than the area of ​​transistor M4 in the two-stage current driving device 10. To solve this problem, the present invention proposes a new type of current driving device, which has the benefits of both a two-stage current driving device and a three-stage current driving device. More specifically, in the current driving device of the present invention, the circuit area is smaller and equivalent to the circuit area of ​​the two-stage current driving device, and the operating speed is equivalent to or even faster than the speed of the three-stage current driving device.

[0045] Figure 3 3 is a schematic diagram of a current driving device 30 according to an embodiment of the present invention. The current driving device 30 includes a current source 302, a current mirror 304, an output enabling switch 306, a control circuit 308 and a bias generator 312. A light emitting diode load 310 driven by the current driving device 30 is also shown in FIG. Figure 3 For convenience of explanation. The LED load 310 may include one or more LED strings disposed in a display screen (such as a backlight module of a liquid crystal display screen). The current driving device 30 may be used to output a driving current I_LED to drive the LED load 310. In one embodiment, the driving current I_LED may be used as a sink current, which may flow through the LED string of the LED load 310, thereby controlling the LED to emit light.

[0046] Specifically, the current driving device 30 has an input channel CH_IN and an output channel CH_OUT. The current source 302 is disposed on the input channel CH_IN and is used to generate a reference current I_REF (or seed current) on the input channel CH_IN. In one embodiment, the current source 302 can be a constant current source for supplying an accurate and constant current.

[0047] The current mirror 304 is disposed between the input channel CH_IN and the output channel CH_OUT, and can generate a driving current I_LED according to the reference current I_REF. More specifically, the current mirror 304 can mirror the reference current I_REF to generate the driving current I_LED, and then output the driving current I_LED to the light emitting diode load 310. In one embodiment, the current mirror 304 can amplify the reference current I_REF by a specific ratio to generate the driving current I_LED.

[0048] The output enable switch 306 is disposed in the output channel CH_OUT and can be used to enable the driving current I_LED to be output to the LED load 310. Similarly, since the output enable switch 306 is used to drive the LED load 310 with a high power supply voltage VLED, it can be implemented by a high voltage component, such as a high voltage transistor.

[0049] The control circuit 308 is coupled between the input channel CH_IN and the output channel CH_OUT, and can be used to perform feedback control so that the current mirror 304 can generate an accurate driving current I_LED. In this example, the feedback end of the control circuit 308 is connected to the input channel CH_IN to form a feedback loop through the input channel CH_IN. The control circuit 308 can be implemented by an operational amplifier or any other circuit with feedback control function, and details can be found in the following paragraphs.

[0050] The bias generator 312 is coupled to the input channel CH_IN and is used to supply a reference voltage VREF to the input channel CH_IN. The bias generator 312 can be used to control the bias voltage of the input channel CH_IN so that the circuit components (including the current source 302 and the current mirror 304) on the input channel CH_IN can operate normally to generate an accurate reference current I_REF.

[0051] Figure 4A detailed implementation of the current driving device 30 is shown, and the current driving device 30 includes a current source 302, transistors M1-M4, and operational amplifiers OP1 and OP2. The current source 302 can receive a power supply voltage VDD to generate a reference current I_REF. Transistors M2 and M3 can be used to implement a current mirror 304. Transistor M4 is used to implement an output enable switch 306 (e.g., by receiving an output enable signal OUT_EN). Transistor M1 can be implemented on the input channel CH_IN and coupled between the current source 302 and the current mirror 304 to serve as an input control transistor. In addition, operational amplifier OP1 can be used to implement a bias generator 312, and operational amplifier OP2 can be used to implement a control circuit 308.

[0052] Specifically, the operational amplifier OP1 is coupled to the drain terminal of the input control transistor M1 to control the level of the drain terminal voltage VP of the transistor M1 according to the reference voltage VREF. Figure 4 As shown, the positive input terminal of the operational amplifier OP1 is coupled to the drain terminal of the transistor M1, the negative input terminal of the operational amplifier OP1 is coupled to a reference voltage source to receive the reference voltage VREF, and the output terminal of the operational amplifier OP1 is coupled to the transistors M2 and M3 in the current mirror 304. Under this circuit architecture, through the virtual short-circuit between the input terminals of the operational amplifier OP1, the operational amplifier OP1 can control the voltage VP to be substantially equal to the reference voltage VREF. It should be noted that the voltage VP of the input channel CH_IN cannot be too high, otherwise it will be compressed to the voltage headroom of the current source 302, causing the current source 302 to fail to operate normally to generate the required reference current I_REF. In this case, the level of the voltage VP should be well controlled by the operational amplifier OP1 using a suitable reference voltage VREF.

[0053] The current mirror 304 may be formed by a transistor M2 located at an input channel CH_IN and a transistor M3 located at an output channel CH_OUT, and is used to mirror a reference current I_REF on the input channel CH_IN to generate a driving current I_LED on the output channel CH_OUT. In the current mirror 304, the transistors M2 and M3 should have an appropriate width-to-length ratio (W / L ratio) to mirror the reference current I_REF to generate the required driving current I_LED. To ensure that the current mirror 304 can generate an accurate driving current I_LED, the voltages V1 and V2 at the drain terminals of the transistors M2 and M3 should be equal, and this equal voltage V1 and V2 can be achieved by an operational amplifier OP2.

[0054] like Figure 4As shown, the positive input terminal of the operational amplifier OP2 is coupled to the output channel CH_OUT, the negative input terminal of the operational amplifier OP2 is coupled to the input channel CH_IN, and the output terminal of the operational amplifier OP2 is coupled to the gate terminal of the input control transistor M1. Under this circuit architecture, the output terminal and the negative input terminal of the operational amplifier OP2 plus the transistor M1 form a feedback loop to control the voltage V1 of the input channel CH_IN to track the voltage V2 of the output channel CH_OUT.

[0055] Different from the feedback loop formed by the transistor M4 on the output channel CH_OUT in the two-stage current driving device 10 and the three-stage current driving device 20, in the embodiment of the present invention, the output terminal of the operational amplifier OP2 is coupled to the transistor M1 on the input channel CH_IN. In this case, the feedback loop of the operational amplifier OP2 can be formed through the input channel CH_IN to control the voltage V1 to track the voltage V2. Therefore, the voltage V1 can approach the voltage V2, and the levels of the voltages V1 and V2 are substantially equal when the feedback loop is stable. Since the load faced by the feedback loop is related to the transistor M1 through which the reference current I_REF flows, wherein the transistor M1 is a low-voltage or medium-voltage component, and the reference current I_REF is usually much smaller than the driving current I_LED, the response speed of the feedback loop in the current driving device 30 will be much greater than the feedback loop in the two-stage current driving device 10.

[0056] In addition, the transistor M4 is coupled to the output terminal of the current driving device 30 for outputting the driving current I_LED, and the output terminal is set to be coupled to the light-emitting diode load 310 on the display screen. Therefore, the transistor M4 should be implemented by a high-voltage transistor to withstand the high power supply voltage VLED of the light-emitting diode load 310. In this example, the transistor M4 can be controlled by receiving the output enable signal OUT_EN, which is a high-speed digital control signal. Therefore, the transistor M4 can be turned on at a faster speed, so that the current driving device 30 can quickly output the driving current I_LED.

[0057] When the transistor M4 is turned on, the driving current I_LED supplied by the current driving device 30 begins to flow through the light emitting diode load 310, causing the voltage V2 and the output voltage VOUT to drop, and the speed of the drop will be rapidly reduced. This is because the drain of the transistor M3 limits the source voltage during the operation of the current mirror 304, which can avoid the overshoot current on the output channel CH_OUT. Through the operation of the feedback loop formed by the operational amplifier OP2, the voltage V1 can track the falling voltage V2 and drop to the same level. Since the output end of the operational amplifier OP2 is coupled to the input channel CH_IN and has a smaller output load, the feedback loop can control the voltage V1 to quickly reach the level of the voltage V2, that is, the voltage V1 can track the voltage V2 and quickly stabilize. In this case, the driving current I_LED can also quickly reach its target level. When the voltages V1 and V2 reach a lower level, the gate voltage VG can be well controlled to turn on the transistors M2 and M3 to a certain extent, thereby generating the required driving current I_LED, which is equal to a certain multiple of the reference current I_REF.

[0058] It is worth noting that as long as the transistors M2 and M3 can be turned on normally to supply current, the output voltage VOUT of the current driving device 30 should be as low as possible, thereby reducing the power consumption of the current driving device 30. In one embodiment, the transistors M2 and M3 in the current mirror 304 can be designed to have a larger size so that they can still supply sufficient current under a low drain-to-source voltage.

[0059] In one embodiment, the driving current I_LED generated by the current mirror 304 is equal to M times the reference current I_REF. This current ratio can be achieved by properly designing the width-to-length ratio of the transistors M2 and M3 to be 1:M, where M can be any positive number.

[0060] It can be seen that the load of the operational amplifier OP2 in the current driving device 30 is determined by the transistor M1, which can be a low-voltage component or a medium-voltage component with a smaller load. Therefore, compared with the operational amplifier OP2 in the above-mentioned two-stage current driving device 10, the operational amplifier OP2 in the current driving device 30 has a faster response speed. That is to say, in the current driving device 30 of the present invention, the feedback loop of the operational amplifier OP2 can be quickly stabilized, so that the driving current I_LED can quickly reach the target value. In addition, the current driving device 30 of the present invention includes 4 transistors M1~M4, and there is no need to set an additional output transistor M5. Therefore, in terms of circuit cost, the current driving device 30 is superior to the above-mentioned three-stage current driving device 20. In this way, the current driving device of the present invention has the advantages of both a two-stage current driving device and a three-stage current driving device.

[0061] It is worth noting that the purpose of the present invention is to propose a new circuit structure of a current driving device, which can be used to supply driving current to the LED string in the display screen. Those skilled in the art can make modifications or changes accordingly, but are not limited to this. For example, the current driving device of the present invention can be applied to the LED string located in the backlight module of the liquid crystal display screen. In another embodiment, the LED string used to receive current from the current driving device of the present invention can also be a part of the LED pixels on the direct view LED panel, such as a mini-LED panel, a micro-LED panel, or an organic light emitting diode panel. Generally speaking, the LEDs in the backlight module of the liquid crystal display screen need to operate under ultra-high voltage (such as up to 60V), wherein the LED string usually has a large number of LEDs, and thus a large amount of current needs to pass, which is accompanied by a huge load, resulting in the operating speed of the current driving device being limited. Therefore, the current driving device of the present invention is more suitable for the application of the backlight module. However, it should be noted that the current driving device of the present invention can supply driving current to any component that uses current driving, thereby improving the system operation speed. The component driven by current may be any light-emitting component that emits light by current driving, and its application is not limited to the light-emitting diode string in the backlight module.

[0062] Also note that Figure 3 The circuit structure in the figure is only one exemplary embodiment of the present invention, and various variations of the current driving device of the present invention are described as follows.

[0063] Figure 5 Another detailed embodiment of the current driving device 30 is shown, and its circuit structure is similar to Figure 4 The circuit structures shown are similar, so signals or components with similar functions are represented by the same symbols. In this example, the operational amplifier OP1 is omitted, and the drain terminal of the input control transistor M1 (i.e., the current output terminal of the current source 302) is connected to the gate terminals of the transistors M2 and M3. This circuit implementation can be regarded as omitting the bias generator 312, or the bias generator 312 is realized by connecting the drain terminal of the transistor M1 and the gate terminals of the transistors M2 and M3 with a wire, which means that the reference voltage for VP can be supplied by the gate voltage VG of the transistor M2 or M3.

[0064] As described above, the purpose of the operational amplifier OP1 is to control the level of the voltage VP at the current output terminal of the current source 302 to prevent the margin of the current source 302 from being compressed so that the current source 302 can operate normally. On the other hand, the voltage VP can also be controlled without using an operational amplifier. Figure 5As shown, the voltage VP can be clamped to be equal to the gate voltage VG of transistors M2 and M3. As long as the dimensions of transistors M2 and M3 are well designed so that the gate voltage VG is always within an appropriate range, the voltage VP will not be too high and squeeze the space of the current source 302. Figure 5 The circuit architecture omits an operational amplifier, thereby achieving the benefit of reducing circuit cost.

[0065] In another embodiment, in order to further simplify the circuit structure and reduce the circuit cost, both the operational amplifiers OP1 and OP2 can be omitted. Figure 6 1 shows another detailed embodiment of the current driving device 30, which does not include any operational amplifier. More specifically, the operational amplifier OP2 of the control circuit coupled between the input channel CH_IN and the output channel CH_OUT is omitted, or equivalently, the control circuit can be regarded as being implemented by a wire connected between the gate terminals of the transistors M2 and M3 and the drain terminal of the input control transistor M1. In addition, the current driving device 30 may include a bias generator 612, which may be a voltage source, which can be used to supply a reference voltage VREF to the input control transistor M1 without using the operational amplifier OP1.

[0066] In an exemplary embodiment, the bias generator 612 can receive the voltage V2 of the output channel CH_OUT, and output the reference voltage VREF according to the voltage V2 to control the voltage V1. In the above-mentioned embodiment, the drain terminals of the transistors M2 and M3 are respectively coupled to the two input terminals of the operational amplifier OP2, so that the voltage V1 can track the voltage V2 through the feedback loop generated by the operational amplifier OP2 and finally equal to the voltage V2. In contrast, in Figure 6 In the circuit structure of FIG. 1 , the bias generator 612 can control the voltage V1 to track the voltage V2 by any suitable means, such as voltage correction and / or digital control, which is not limited to feedback control of an operational amplifier.

[0067] In the above embodiment, the voltage V1 can be controlled to be equal to the voltage V2, so as to generate the required driving current I_LED through the current mirror 304, wherein the current amplification ratio of the current mirror 304 can be determined according to the width-to-length ratio of the transistors M2 and M3. In another embodiment, the voltage V1 of the input channel CH_IN can be controlled to track the voltage V2 of the output channel CH_OUT so that the ratio of the voltage V2 to the voltage V1 is fixed at a specific value, that is, the value V2 / V1 is constant. For example, please refer back to Figure 3, the voltages V1 and V2 can be controlled to have a fixed ratio, and the control circuit 308 can be implemented in any appropriate manner to control the ratio of the voltages V1 and V2, thereby determining the driving current I_LED according to the reference current I_REF and the ratio of V2 / V1. In this example, the transistors M2 and M3 can be operated in a linear region, and their behavior is equivalent to a resistor, so the value of the driving current I_LED can be accurately controlled by the value V2 / V1. In other words, the reference current I_REF can be amplified and the amplification ratio is determined by the value V2 / V1 to generate the required driving current I_LED value.

[0068] In summary, the present invention proposes a circuit structure of a current driving device, which can be used to output current to drive a light-emitting diode string. The current driving device can be composed of a current mirror controlled by an operational amplifier, and the operational amplifier can control the voltage of the current mirror to generate an accurate driving current on the output channel according to the reference current on the input channel. The output end of the operational amplifier is coupled to the input control transistor on the input channel, and then coupled to the negative input end of the operational amplifier to form a feedback loop through the input channel. Therefore, the feedback loop will not face the huge load of the output transistor (which is a high-voltage component) located at the output end of the current driving device. This connection method can improve the response speed of the feedback loop, thereby improving the operating speed of the current driving device outputting the driving current.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A current driving device having an input channel and an output channel, characterized in that: The current driving device comprises: a current source, disposed in the input channel; a current mirror, disposed between the input channel and the output channel and coupled to the current source; an output enabling switch, disposed in the output channel and coupled to the current mirror; and A control circuit is coupled between the input channel and the output channel to form a feedback loop through the input channel.

2. The current driving device according to claim 1, characterized in that: The control circuit is used for controlling a first voltage of the input channel to track a second voltage of the output channel.

3. The current driving device according to claim 2, characterized in that: The first voltage is substantially equal to the second voltage.

4. The current driving device according to claim 2, characterized in that: The ratio of the second voltage to the first voltage is fixed at a specific value.

5. The current driving device according to claim 1, characterized in that: The current source is used to generate a reference current on the input channel.

6. The current driving device according to claim 5, characterized in that: The current mirror is used for generating a driving current according to the reference current.

7. The current driving device according to claim 6, characterized in that: The output enable switch is used to enable the output of the drive current.

8. The current driving device according to claim 1, characterized in that: The output enable switch includes a high voltage transistor.

9. The current driving device according to claim 1, characterized in that: The current mirror includes: a first transistor disposed in the input channel; and A second transistor is disposed in the output channel.

10. The current driving device according to claim 1, characterized in that: Also includes: an input control transistor, disposed in the input channel and coupled between the current source and the current mirror; as well as A bias generator is coupled to the input control transistor.

11. The current driving device according to claim 10, characterized in that: The bias generator is used for supplying a reference voltage to the input control transistor.

12. The current driving device according to claim 10, characterized in that: The bias generator comprises: an operational amplifier, comprising: a first input terminal coupled to the input control transistor; a second input terminal coupled to a reference voltage source; and An output terminal is coupled to the current mirror.

13. The current driving device according to claim 12, characterized in that: The first input terminal of the operational amplifier is coupled to a drain terminal of the input control transistor.

14. The current driving device according to claim 1, characterized in that: The control circuit includes an operational amplifier.

15. The current driving device according to claim 14, characterized in that: The operational amplifier comprises: a first input terminal coupled to the output channel; a second input terminal coupled to the input channel; and An output terminal is coupled to the input channel.

16. A current driving device having an input channel and an output channel, characterized in that: The current driving device comprises: a current source, disposed in the input channel; an input control transistor, disposed in the input channel and coupled to the current source; a current mirror disposed between the input channel and the output channel and coupled to the input control transistor; an output enabling switch, disposed in the output channel and coupled to the current mirror; and a first operational amplifier, comprising: a first input terminal coupled to the output channel; a second input terminal coupled to the input channel; and An output terminal is coupled to the input control transistor.

17. The current driving device according to claim 16, characterized in that: The first operational amplifier is used for controlling a first voltage of the input channel to track a second voltage of the output channel.

18. The current driving device according to claim 17, characterized in that: The first voltage is substantially equal to the second voltage.

19. The current driving device according to claim 17, characterized in that: The ratio of the second voltage to the first voltage is fixed at a specific value.

20. The current driving device according to claim 16, characterized in that: The current source is used to generate a reference current on the input channel.

21. The current driving device according to claim 20, characterized in that: The current mirror is used for generating a driving current according to the reference current.

22. The current driving device according to claim 21, characterized in that: The output enable switch is used to enable the output of the drive current.

23. The current driving device according to claim 16, characterized in that: The output enable switch includes a high voltage transistor.

24. The current driving device according to claim 16, characterized in that: The current mirror includes: a first transistor disposed in the input channel; and A second transistor is disposed in the output channel.

25. The current driving device according to claim 16, characterized in that: Also includes: A bias generator is coupled to the input control transistor.

26. The current driving device according to claim 25, characterized in that: The bias generator is used for supplying a reference voltage to the input control transistor.

27. The current driving device according to claim 25, characterized in that: The bias generator includes: a second operational amplifier, including: a first input terminal coupled to the input control transistor; a second input terminal coupled to a reference voltage source; and An output terminal is coupled to the current mirror.

28. The current driving device according to claim 27, characterized in that: The first input terminal of the second operational amplifier is coupled to a drain terminal of the input control transistor.

29. The current driving device according to claim 16, characterized in that: The output terminal of the first operational amplifier is coupled to a gate terminal of the input control transistor.

30. The current driving device according to claim 16, characterized in that: The first operational amplifier is used to form a feedback loop through the input channel.

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