LED driving circuit and control method thereof

Abstract

The application discloses an LED driving circuit and a control method thereof, wherein the circuit comprises a first field effect transistor, a drain of the first field effect transistor outputs a working current; a charging module is connected between a gate and a source of the first field effect transistor to provide the working current for the drain of the first field effect transistor, the charging module comprises a first control unit connected with the gate of the first field effect transistor, and the first control unit controls a variation slope of the output working current; an opening acceleration module is connected with the gate of the first field effect transistor to drive the gate voltage of the first field effect transistor to rapidly reach a threshold voltage; and a signal control module is connected with the charging module and the opening acceleration module, outputs a pulse width modulation signal, and controls the conduction and the shutdown of the charging module and the opening acceleration module according to the pulse width modulation signal. The LED driving circuit and the control method thereof ensure the consistency between the actual output working current width and the ideal pulse width modulation signal width.

Description

Technical Field

[0001] This invention relates to the field of chip technology, and in particular to an LED driving circuit and its control method. Background Technology

[0002] LED driver chips use an internal high-precision current source and corresponding driver stage circuits to convert the corresponding pulse width control signal (PWM signal) input from the front end into the required output current square wave to drive the external light-emitting beads (LEDs), thereby achieving control to produce the required different brightness levels.

[0003] Both direct-view LED systems and backlit LED systems have strict requirements regarding electromagnetic interference (EMI). The large current of the PWM square wave output by the LED driver chip in the system is the biggest contributor to EMI problems. To improve the EMI characteristics of the system, there are generally strict requirements on the rate of change of the output PWM current in the driver stage of the LED driver chip.

[0004] Traditional LED driver circuits typically use additional control circuits to control the rate of change of current. However, when a field-effect transistor (FET) is used as a switch in the driver circuit, it is affected by the threshold voltage of the FET's gate voltage during the turn-on process. When the gate voltage does not reach the threshold voltage, no working current is generated at the drain of the FET, which results in the actual output working current width and the ideal pulse width modulation (PWM) signal width not being exactly the same. Usually, the actual output working current width is smaller than the PWM signal width.

[0005] To address the issue of inconsistent grayscale widths, digitally adjustable compensation is typically introduced. This involves adjusting the input PWM signal based on the measured difference between the rising and falling edges, combined with the ideal current integral value, to ensure a consistent and linear final current integral, thus compensating for insufficient grayscale accuracy. However, this improvement is still limited, requiring frequent testing and calibration, sometimes even for each individual display, increasing overall costs. Furthermore, due to aging, temperature, and stress, the accuracy and effectiveness of this compensation cannot be guaranteed to remain constant, and grayscale inconsistencies may reappear after a period of time or when localized displays overheat.

[0006] Therefore, it is necessary to improve the existing technology to overcome the aforementioned defects. Summary of the Invention

[0007] The purpose of this invention is to provide an LED driving circuit and its control method to ensure the consistency between the actual output operating current width and the ideal pulse width modulation signal width.

[0008] To address the aforementioned technical problems, in a first aspect, the present invention provides an LED driving circuit, comprising:

[0009] The first field-effect transistor has a drain output operating current.

[0010] A charging module is connected between the gate and source of the first field-effect transistor to provide operating current to the drain of the first field-effect transistor. The charging module includes a first control unit connected to the gate of the first field-effect transistor, and the first control unit controls the slope of the output operating current.

[0011] The acceleration module is activated and connected to the gate of the first field-effect transistor, driving the gate voltage of the first field-effect transistor to quickly reach the threshold voltage.

[0012] The signal control module is connected to the charging module and the acceleration module, outputs a pulse width modulation signal, and controls the charging module and the acceleration module to turn on and off according to the pulse width modulation signal.

[0013] Preferably, the acceleration module includes:

[0014] A first error amplifier, wherein a threshold voltage is input to the first input terminal of the first error amplifier, and the second input terminal of the first error amplifier is connected to the gate of the first field-effect transistor;

[0015] A diode, wherein the anode of the diode is connected to the first output terminal of the first error amplifier, and the cathode of the diode is connected to the gate of the first field-effect transistor;

[0016] A first switch is connected in series with the diode, and the third input terminal of the first switch is connected to the signal control module.

[0017] Preferably, the charging module further includes a reference current unit, the reference current unit comprising:

[0018] The second field-effect transistor has its gate connected to the first reference voltage, its drain connected to the source of the first field-effect transistor, and its source grounded.

[0019] The second error amplifier has its fourth input terminal connected to the second reference voltage and its fifth input terminal connected to the drain of the second field-effect transistor.

[0020] The second switch is connected between the second output terminal of the second error amplifier and the gate of the first field-effect transistor, and the sixth input terminal of the second switch is connected to the signal control module.

[0021] Preferably, the first control unit includes a first adjustable resistor connected in series with the second switch, wherein the third input terminal of the first switch and the sixth input terminal of the second switch are turned on and turned off in response to a high-level signal and a low-level signal in the pulse width modulation signal.

[0022] Preferably, the first control unit includes a charging current source connected to the gate of the first field-effect transistor and a third switch connected in series with the charging current source, wherein the seventh input terminal of the third switch is connected to the signal control module.

[0023] Preferably, the signal control module includes:

[0024] The signal generator outputs a pulse width modulation signal;

[0025] The comparator has its eighth input terminal connected to the gate of the first field-effect transistor, and its ninth input terminal connected to the target voltage.

[0026] The first AND gate has its tenth input connected to the signal generator, its eleventh input connected to the third output of the comparator, its fourth output connected to the third input of the first switch and the seventh input of the third switch, and its eleventh input is an inverting input.

[0027] The second AND gate has its twelfth input connected to the third output of the comparator, its thirteenth input connected to the signal generator, and its fifth output connected to the sixth input of the second switch.

[0028] Preferably, the LED driving circuit further includes a discharge module connected to the gate of the first field-effect transistor. The discharge module includes a second adjustable resistor connected between the gate of the first field-effect transistor and ground, and a fourth switch connected in series with the second adjustable resistor. The fourteenth input terminal of the fourth switch is turned on in response to a low-level signal and turned off when a high-level signal is received in the pulse width modulation signal.

[0029] Preferably, the LED driving circuit further includes a discharge module connected to the gate of the first field-effect transistor. The discharge module includes a discharge current source connected between the gate of the first field-effect transistor and ground, and a fifth switch connected in series with the discharge current source. The fifteenth input terminal of the fifth switch is turned on in response to a low-level signal and turned off when a high-level signal is received in the pulse width modulation signal.

[0030] Preferably, the signal control module includes a NOT gate, the sixteenth input of which is connected to the pulse width modulation signal, and the sixth output of which is connected to the fifteenth input of the fifth switch.

[0031] Secondly, the present invention also proposes a control method for an LED driving circuit, comprising:

[0032] Configure the LED driving circuit as described in the first aspect;

[0033] Output pulse width modulation signal;

[0034] Compare the gate voltage and threshold voltage of the first field-effect transistor;

[0035] When the gate voltage is less than the threshold voltage, the acceleration module drives the gate voltage of the first field-effect transistor to quickly reach the threshold voltage.

[0036] When the gate voltage is greater than or equal to the threshold voltage, the charging module provides operating current to the drain of the first field-effect transistor.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] The LED driving circuit and control method of this invention include a first control unit in the charging module that controls the slope of the drain output current of the first field-effect transistor (FET). An acceleration module is added to this controllable output current rate LED driving circuit. At the instant the first FET turns on, the gate voltage of the first FET is rapidly driven to reach the threshold voltage, allowing the drain output current of the first FET to have an actual current output with a very short delay. The acceleration module and signal control module ensure a smooth transition between the acceleration module and the charging module, with the output current smoothly connected to the charging module control. Consistency between the actual output current and the ideal pulse width modulation signal width can be achieved without any digital compensation or correction. Furthermore, the acceleration module circuit is simple, requires no factory calibration, and has greater robustness to aging, temperature, and inter-chip differences, resulting in more reliable driving. It is also more accurate than traditional digital PWM compensation methods, thereby improving the low-grayscale accuracy of the LED driver. Attached Figure Description

[0039] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and are not intended to specifically limit the shapes and proportions of the components. Those skilled in the art, guided by the teachings of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances. In the drawings:

[0040] Figure 1 This is a schematic block diagram of the LED driving circuit in this invention;

[0041] Figure 2 This is a schematic diagram of the LED driving circuit in this invention;

[0042] Figure 3 This is a schematic diagram of the LED driving circuit in Embodiment 1 of the present invention;

[0043] Figure 4 This is a schematic diagram of the signal waveform of the LED driving circuit in Embodiment 1 of the present invention;

[0044] Figure 5 This is a schematic diagram of the circuit structure of the charging module, discharging module, and acceleration module in Embodiment 2 of the present invention;

[0045] Figure 6 This is a schematic diagram of the circuit structure of the signal control module in Embodiment 2 of the present invention;

[0046] Figure 7 A schematic diagram of the signal waveforms of the LED driving circuit in Embodiment 2 of the present invention;

[0047] Figure 8 This is a flowchart of the control method for the LED driving circuit in this invention;

[0048] Figure 9 This is a flowchart of the control method for the LED driving circuit in Embodiment 1 of the present invention;

[0049] Figure 10 This is a flowchart of the control method for the LED driving circuit in Embodiment 2 of the present invention. Detailed Implementation

[0050] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0051] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] like Figure 1 The LED driving circuit according to a preferred embodiment of the present invention includes a first field-effect transistor 1, a charging module 2 connected between the gate and source of the first field-effect transistor 1, a discharging module 3 connected to the gate of the first field-effect transistor 1, a turn-on acceleration module 4 connected to the gate of the first field-effect transistor 1, and a signal control module 5 connected to the charging module 2 and the turn-on acceleration module 4. The charging module 2 provides operating current to the drain of the first field-effect transistor 1, the discharging module 3 discharges the drain of the first field-effect transistor 1, the turn-on acceleration module 4 drives the gate voltage V1 of the first field-effect transistor 1 to quickly reach the threshold voltage Vth, and the signal control module 5 outputs a pulse width modulation signal and controls the conduction and turn-off of the charging module 2, the discharging module 3, and the turn-on acceleration module 4 according to the pulse width modulation signal. It should be noted that in this embodiment, the charging module 2 and the discharging module 3 alternately turn on and off according to the pulse width modulation signal, and the turn-on acceleration module 4 turns on and off synchronously with the charging module 2.

[0054] like Figure 2 As shown, the first field-effect transistor 1 serves as the switching transistor in the LED driving circuit. Preferably, a cascaded field-effect transistor (CAS_FET) is used, which can achieve lower switching voltage, lower power consumption, and a denser design. The charging module 2 includes a reference current unit 21 connected between the gate and source of the first field-effect transistor 1 and a first control unit 22 connected to the gate of the first field-effect transistor 1. The reference current unit 21 provides an output operating current IOUT to the drain of the first field-effect transistor 1. The first control unit 22 controls the slope of the output operating current IOUT at the drain of the first field-effect transistor 1. Furthermore, the first control unit 22 controls the rising slope of the output operating current IOUT.

[0055] The reference current unit 21 includes a second field-effect transistor (FET) 211, a second error amplifier 212, and a second switch 213. The gate of the second FET 211 is connected to a first reference voltage V2, and the drain of the second FET 211 is connected to the source of the first FET 1. The source of the second FET 211 is grounded. The fourth input terminal C1 of the second error amplifier 212 is connected to a second reference voltage V3, and the fifth input terminal C2 of the second error amplifier 212 is connected to the drain of the second FET 211. The second control terminal D2 of the second switch 213 is connected between the second output terminal C3 of the second error amplifier 212 and the gate of the first FET 1, and the sixth input terminal D1 of the second switch 213 is connected to the signal control module 5. The first reference voltage is a reference voltage corresponding to the desired output target current I1. When the reference current unit 21 is turned on, the second FET 211 provides the first FET with an output operating current IOUT that is a constant output target current I1. Furthermore, the drain voltage V4 of the second field-effect transistor 211 is loop-controlled with the second reference voltage V3. That is, the loop formed by the second error amplifier 212 and the first field-effect transistor 1 ensures that in the final steady state, the drain voltage V4 of the second field-effect transistor 211, which is the source voltage of the first field-effect transistor 1, is the same as the second reference voltage V3. This eliminates the channel modulation effect of the second field-effect transistor 211 as a current source reference and ensures that the current reference is more accurate.

[0056] When the gate voltage V1 of the first field-effect transistor 1 does not reach the threshold voltage Vth, there is no current output from the drain of the first field-effect transistor 1. However, the acceleration module 4 can drive the gate voltage V1 of the first field-effect transistor 1 to quickly reach the threshold voltage Vth. Specifically, the acceleration module 4 includes a first error amplifier 41, a diode 42, and a first switch 43. The first input terminal A1 of the first error amplifier 41 receives the threshold voltage Vth, and the second input terminal A2 of the first error amplifier 41 is connected to the gate of the first field-effect transistor 1. The threshold voltage Vth is the voltage obtained by sampling and matching a field-effect transistor of the same type as the first field-effect transistor 1 through a current-defined minimum current. The anode of the diode 42 is connected to the first output terminal A3 of the first error amplifier 41, and the cathode of the diode 42 is connected to the gate of the first field-effect transistor 1. The first switch 43 is connected in series with the diode 42. In this embodiment, the first control terminal B2 of the first switch 43 is connected between the first error amplifier 41 and the diode 42, and the third input terminal B1 of the first switch 43 is connected to the signal control module 5. When the acceleration module 4 and charging module 2 are synchronously turned on, due to the presence of the first control unit 22, the charging current of the charging module 2 to the first field-effect transistor 1 is relatively small, and the gate voltage V1 of the first field-effect transistor 1 is less than the threshold voltage Vth. At this time, the acceleration module 4 plays a dominant role. Utilizing the large unidirectional transient current driving capability of the first error amplifier 41, when the acceleration module 4 is first turned on, it directly drives the gate voltage V1 of the first field-effect transistor 1 to quickly reach the threshold voltage Vth through the error amplification generated by comparing the gate voltage V1 of the first field-effect transistor 1 with the threshold voltage Vth. However, when the gate voltage V1 of the first field-effect transistor 1 exceeds the threshold voltage Vth, due to the unidirectional effect of the diode 42, the acceleration module 4 will exit control, and the charging module 2 will continue to charge the first field-effect transistor 1 to a steady-state value.

[0057] When the discharge module 3 is turned on, the discharge module 3 discharges the gate of the first field-effect transistor 1. Similarly to the charging module 2, the discharge module 3 includes a second control unit connected to the gate of the first field-effect transistor 1. The second control unit controls the slope of the change of the drain output current IOUT of the first field-effect transistor 1. Furthermore, the first control unit 22 controls the downward slope of the output current IOUT.

[0058] To further illustrate the structure of the charging module 2 and the discharging module 3, a detailed description is provided below with reference to specific embodiments.

[0059] Example 1

[0060] like Figure 3As shown, based on the above-described LED driving circuit, the first control unit 22 includes a first adjustable resistor 221 connected in series with the second switch 213. In this embodiment, preferably, the first adjustable resistor 221 is connected between the second switch 213 and the second output terminal C3 of the second error amplifier 212. When the charging module 2 is turned on, the rising slope of the output operating current IOUT is determined by the voltage difference between the output voltage of the second error amplifier 212 and the gate voltage of the first field-effect transistor 1 divided by the resistance value of the first adjustable resistor 221. The rising slope of the output operating current IOUT can be adjusted by changing the resistance value of the first adjustable resistor 221.

[0061] Similarly, the second control unit includes a second adjustable resistor 311 connected between the gate of the first field-effect transistor 1 and ground, and a fourth switch 312 connected in series with the second adjustable resistor 311. Preferably, the fourth control terminal E2 of the fourth switch 312 is connected between the second adjustable resistor 311 and ground. When the discharge module 3 is turned on, the decreasing slope of the output operating current IOUT is determined by dividing the voltage difference between the gate voltage of the first field-effect transistor 1 and the reference low voltage by the resistance value of the second adjustable resistor 311. The decreasing slope of the output operating current IOUT can be adjusted by changing the resistance value of the second adjustable resistor 311.

[0062] The signal control module 5 includes a signal generator that outputs a pulse width modulation (PWM) signal. The first switch 43, the second switch 213, and the fourth switch 312 all respond to the PWM signal. Preferably, the third input terminal B1 of the first switch 43 and the sixth input terminal D1 of the second switch 213 are turned on and off when the PWM signal is high (PWM_ON) or low (PWM_OFF) in the PWM signal. Similarly, the fourteenth input terminal E1 of the fourth switch 312 is turned on and off when the PWM signal is low (PWM_OFF) or high (PWM_ON) in the PWM signal. It is understood that any existing drive circuit structure can be used to achieve the switching on / off of the high-level signal and the low-level signal, or vice versa, and no further limitations are imposed here.

[0063] like Figure 8 As shown, this embodiment also proposes a driving method based on the LED driving circuit structure of this embodiment, including:

[0064] S1: Configure the LED driving circuit in Embodiment 1;

[0065] S2: Output pulse width modulation signal;

[0066] S3: Compare the gate voltage V1 and threshold voltage Vth of the first field-effect transistor. When the gate voltage V1 is less than the threshold voltage Vth, the acceleration module 4 is turned on to drive the gate voltage of the first field-effect transistor 1 to quickly reach the threshold voltage. When the gate voltage V1 is greater than or equal to the threshold voltage Vth, the charging module 2 provides operating current to the drain of the first field-effect transistor 1.

[0067] like Figure 9 As shown, step S3 specifically includes:

[0068] S3-100: Determine whether the pulse width modulation signal is a high-level signal PWM_ON. If yes, proceed to step S3-110; otherwise, proceed to step S3-120.

[0069] S3-110: When the pulse width modulation signal is a high-level signal PWM_ON, the synchronous control turns on the acceleration module 4 and the charging module 2.

[0070] S3-111: Determine whether the gate voltage V1 of the first field-effect transistor is less than the threshold voltage Vth. If yes, proceed to step S3-112; otherwise, proceed to step S3-113.

[0071] S3-112: Enable acceleration module 4 to drive the gate voltage of the first field-effect transistor 1 to quickly reach the threshold voltage;

[0072] S3-113: The charging module 2 provides the working current to the drain of the first field-effect transistor 1, and the first adjustable resistor 221 controls the rising slope of the output working current IOUT.

[0073] S3-120: When the pulse width modulation signal is a low-level signal PWM_OFF, the discharge module 3 is turned on to discharge the first field-effect transistor 1, and the second adjustable resistor 311 controls the falling slope of the output operating current IOUT.

[0074] like Figure 4The diagram shows the signal waveforms of the LED driving circuit in this embodiment. From top to bottom, they are: the pulse width modulation signal (PWM) waveform, the gate voltage V1 signal waveform of the first field-effect transistor (FET) 1, and the drain output current IOUT signal waveform of the first FET 1. When the PWM signal changes from a low level to a high level, the gate voltage V1 of the first FET 1 simultaneously reaches the threshold voltage Vth (i.e., T0-T1). The drain of the first FET 1 immediately begins to output operating current IOUT. The charging module 2 continues to charge the first FET 1, and the gate voltage V1 of the first FET 1 continues to rise (i.e., T1-T2). The drain output current IOUT of the first FET 1 simultaneously continues to rise until it reaches a steady-state value (i.e., T2-T3). This steady-state value is the target output current I1 required by the drain of the first FET 1. When the PWM signal is low, the discharge module 3 discharges the first FET 1 (i.e., T3-T4) until the drain output current IOUT of the first FET 1 drops to zero. This LED driver circuit can achieve consistency between the actual output current IOUT and the pulse width modulation signal PWM pulse width control without any digital compensation or correction. The circuit for activating the acceleration module 4 is simple, requires no factory calibration, and has greater robustness to aging, temperature, and inter-chip differences, making the drive more reliable.

[0075] Example 2

[0076] This embodiment 2 is an equivalent embodiment of embodiment 1. The difference between it and embodiment 1 is that the circuit implementation structure of the charging module 2 and the discharging module 3 is different.

[0077] like Figure 5 As shown, based on the above LED driving circuit, the first control unit 22 includes a charging current source 222 connected to the gate of the first field-effect transistor 1 and a third switch 223 connected in series with the charging current source 222. Preferably, the third control terminal F2 of the third switch 223 is connected between the charging current source 222 and the gate of the first field-effect transistor 1, and the seventh input terminal F1 of the third switch 223 is connected to the signal control module 5. The charging current source 222 is a constant charging current source. When the first control unit 22 is turned on, the rising slope of the output working current IOUT is determined by the charging current of the charging current source 222. The larger the charging current, the faster the rate of change of the drain output working current IOUT of the first field-effect transistor 1 generated by the parasitic capacitance and part of the Miller effect, and finally realize that the rising rate of the LED output working current IOUT is linear and controllable.

[0078] Similarly, the second control unit includes a discharge current source 314 connected between the gate of the first field-effect transistor 1 and ground, and a fifth switch 313 connected in series with the discharge current source 314. Preferably, the fifth control terminal G2 of the fifth switch 313 is connected between the gate of the first field-effect transistor 1 and the discharge current source 314, and the fifteenth input terminal G1 of the fifth switch 313 is connected to the signal control module 5. The discharge current source 314 is preferably a constant discharge current source. When the second control unit is turned on, the discharge current source 314 discharges the gate of the first field-effect transistor 1. The rate of decrease of the output operating current IOUT is determined by the discharge current of the discharge current source 314. The larger the discharge current, the faster the rate of decrease of the drain output operating current IOUT of the first field-effect transistor 1 is generated by the parasitic capacitance and part of the Miller effect, and finally the linear and controllable rate of decrease of the LED output operating current IOUT is achieved.

[0079] Signal control module 5 includes a signal generator that outputs a pulse width modulation (PWM) signal. The first switch 43, the second switch 213, the third switch 223, and the fifth switch 313 all correspond to the PWM signal. The first switch 43 and the third switch 223 are synchronously turned on and off, the second switch 213 is turned on and off independently, and the fifth switch 313 is turned on and off independently. Preferably, they are executed alternately according to the following rules:

[0080] When the pulse width modulation signal PWM is a high-level signal, and the gate output working current IOUT of the first field-effect transistor 1 does not reach the target current I1, the first switch 43 and the third switch 223 are turned on synchronously, the second switch 213 is turned off, and the fifth switch 313 is turned off.

[0081] When the pulse width modulation signal PWM is a high-level signal, when the gate output operating current IOUT of the first field-effect transistor 1 reaches the target current I1, the first switch 43 and the third switch 223 are turned off synchronously, the second switch 213 is turned on, and the fifth switch 313 is turned off.

[0082] When the pulse width modulation signal PWM is low, the first switch 43 and the third switch 223 are turned off synchronously, the second switch 213 is turned off, and the fifth switch 313 is turned on.

[0083] The specific execution of the above rules can be achieved through a logic control circuit, such as... Figure 6As shown, the specific components include comparator 52, first AND gate 53, second AND gate 54, and NOT gate 55. The eighth input terminal H1 of comparator 52 is connected to the gate of the first field-effect transistor 1, and the ninth input terminal H2 of comparator 52 is connected to the target voltage V5. This target voltage is obtained by sampling and matching the gate voltage of a field-effect transistor of the same type as the first field-effect transistor 1 through a set final target output current. The tenth input terminal J1 of the first AND gate 53 is connected to a signal generator, the eleventh input terminal J2 of the first AND gate 53 is connected to the third output terminal H3 of comparator 52, and the fourth output terminal J3 of the first AND gate 53 is connected to the third input terminal B1 of the first switch 43 and the seventh input terminal F1 of the third switch 223. The fourth output terminal J3 outputs a first control signal PWM_PRE to control the synchronous conduction of the first switch 43 and the third switch 223. To control the on / off state, the eleventh input J2 of the first AND gate 53 is the inverting input; the twelfth input K1 of the second AND gate 54 is connected to the third output H3 of the comparator 52, the thirteenth input K2 of the second AND gate 54 is connected to the signal generator, the fifth output K3 of the second AND gate 54 is connected to the sixth input D1 of the second switch 213, and the fifth output K3 of the second AND gate 54 outputs the second control signal PWM_SEC to control the second switch 213 to turn on and off; the sixteenth input L1 of the NOT gate 55 is connected to the pulse width modulation signal, the sixth output L2 of the NOT gate 55 is connected to the fifteenth input G1 of the fifth switch 313, and the sixth output L2 of the NOT gate 55 outputs the third control signal PWM_OFF_1 to control the fifth switch 313 to turn on and off.

[0084] When the pulse width modulation signal PWM is a high-level signal PWM_ON, and the gate voltage V1 of the first field-effect transistor 1 is less than the target voltage V5, the third output terminal H3 of the comparator 52 outputs a low-level signal. At this time, the fourth output terminal J3 of the first AND gate 53 outputs a high-level signal PWM_PRE, controlling the first switch 43 and the third switch 223 to conduct synchronously. The fifth output terminal K3 of the second AND gate 54 outputs a low-level signal PWM_SEC, controlling the second switch 213 to turn off. The sixth output terminal L2 of the NOT gate 55 outputs a low-level signal PWM_OFF_1, controlling the fifth switch 313 to turn off.

[0085] When the gate voltage V1 of the first field-effect transistor 1 is greater than or equal to the target voltage V5, the third output terminal H3 of the comparator 52 outputs a high-level signal. At this time, the fourth output terminal J3 of the first AND gate 53 outputs the first control signal PWM_PRE as a low-level signal, controlling the first switch 43 and the third switch 223 to turn off synchronously. The fifth output terminal K3 of the second AND gate 54 outputs the second control signal PWM_SEC as a high-level signal, controlling the second switch 213 to turn on. The sixth output terminal L2 of the NOT gate 55 outputs the third control signal PWM_OFF_1 as a low-level signal, controlling the fifth switch 313 to turn off.

[0086] When the pulse width modulation signal PWM is a low-level signal PWM_OFF, the fourth output terminal J3 of the first AND gate 53 outputs the first control signal PWM_PRE as a low-level signal, controlling the first switch 43 and the third switch 223 to turn off synchronously. The fifth output terminal K3 of the second AND gate 54 outputs the second control signal PWM_SEC as a low-level signal, controlling the second switch 213 to turn off. The sixth output terminal L2 of the NOT gate 55 outputs the third control signal PWM_OFF_1 as a high-level signal, controlling the fifth switch 313 to turn on.

[0087] It is understood that the above logic circuit and its connection method are only a preferred embodiment. If the target voltage V5 and the gate voltage V1 of the first field-effect transistor 1 are interchanged, then under the same circumstances, the level signal output by the third output terminal H3 of the comparator 52 will also be interchanged accordingly, and the switches of the first AND gate 53 and the second AND gate 54 will also be interchanged accordingly.

[0088] To prevent the operating voltage of the drain of the first field-effect transistor 1 from ringing due to external noise or parasitic inductance, and to prevent false turn-on caused by charging the gate of the first field-effect transistor 1 through the parasitic capacitance of the first field-effect transistor 1, the discharge module 3 also includes a protection unit connected to the gate of the first field-effect transistor 1. The protection unit includes a sixth switch 321 connected between the gate of the first field-effect transistor 1 and ground. When the gate voltage V1 of the first field-effect transistor 1 is lower than the threshold voltage Vth, the sixth switch 321 can be turned on by a certain delay signal PWM_OFF_DLY, and the second control unit will switch to the protection unit for complete shutdown.

[0089] like Figure 8 As shown, this embodiment also proposes a driving method based on the LED driving circuit structure of this embodiment, including:

[0090] S1: Configure the LED driving circuit in Embodiment 2;

[0091] S2: Output pulse width modulation signal;

[0092] S3: Compare the gate voltage V1 and threshold voltage Vth of the first field-effect transistor. When the gate voltage V1 is less than the threshold voltage Vth, the acceleration module 4 is turned on to drive the gate voltage of the first field-effect transistor 1 to quickly reach the threshold voltage. When the gate voltage V1 is greater than or equal to the threshold voltage Vth, the charging module 2 provides operating current to the drain of the first field-effect transistor 1.

[0093] like Figure 10 As shown, step S3 specifically includes:

[0094] S3-200: Determine whether the pulse width modulation signal is a high-level signal PWM_ON. If yes, proceed to step S3-210; otherwise, proceed to step S3-220.

[0095] S3-210: Determine whether the gate voltage V1 of the first field-effect transistor 1 is less than the target voltage V5. If yes, proceed to step S3-211; otherwise, proceed to step S3-212.

[0096] S3-211: When the pulse width modulation signal PWM is a high-level signal PWM_ON and the gate voltage V1 of the first field-effect transistor 1 is less than the target voltage V5, the acceleration module 4 and the first control unit 22 are turned on. It is determined whether the gate voltage V1 of the first field-effect transistor is less than the threshold voltage Vth. If so, the acceleration module 4 is turned on to drive the gate voltage V1 of the first field-effect transistor 1 to quickly reach the threshold voltage Vth. Otherwise, the charging current source 222 of the first control unit 22 charges the gate of the first field-effect transistor 1, thereby providing the drain of the first field-effect transistor with the working current IOUT and controlling the rising slope of the output working current IOUT.

[0097] S3-212: When the pulse width modulation signal PWM is a high-level signal PWM_ON, and the gate voltage V1 of the first field-effect transistor 1 is greater than or equal to the target voltage V5, the reference current unit 21 is turned on, and the reference current unit 21 provides the first field-effect transistor 1 with an output operating current IOUT that is a constant output target current I1.

[0098] S3-220: When the pulse width modulation signal PWM is a low-level signal PWM_OFF, the discharge module 3 is turned on, and the discharge current source 314 of the second control unit discharges the first field-effect transistor 1, controlling the falling slope of the output operating current IOUT. During the discharge process, step S3-221 is executed synchronously.

[0099] S3-221: Determine whether the gate voltage V1 of the first field-effect transistor 1 is lower than the threshold voltage Vth. If so, control the second control unit to turn off and the protection unit to turn on through a certain delay control, and use a traditional strong pull-down transistor to completely shut down the first field-effect transistor; if not, keep the second control unit on.

[0100] like Figure 7 The diagram shows the signal waveforms of the LED driving circuit in this embodiment. From top to bottom, they are: the pulse width modulation signal PWM waveform, the gate voltage V1 signal waveform of the first field-effect transistor 1, the drain output operating current IOUT signal waveform of the first field-effect transistor 1, the first control signal PWM_PRE waveform controlling the acceleration module 4 and the first control unit 22, the second control signal PWM_SEC waveform controlling the reference current unit 21, the third control signal PWM_OFF_1 waveform controlling the second control unit, and the delay signal PWM_OFF_DLY waveform controlling the protection unit. When the pulse width modulation signal (PWM) transitions from a low level to a high level, the acceleration module 4 and the first control unit 22 are activated. The gate voltage V1 of the first field-effect transistor (FET) 1 synchronously reaches the threshold voltage Vth (T0-T1). The drain of the first FET 1 immediately begins outputting the operating current IOUT. When the PWM signal is high and the gate voltage V1 of the first FET 1 has not reached the target voltage V5 (T1-T2), the first control unit 22 is activated to charge the first FET 1. The gate voltage V1 of the first FET 1 continues to rise. The drain output current IOUT of the first field-effect transistor 1 increases synchronously and continuously. When the gate voltage V1 of the first field-effect transistor 1 reaches the target voltage V5 (i.e., T2-T3), the reference current unit 21 is turned on, and the drain output current IOUT of the first field-effect transistor 1 provides the reference current unit 21 with a steady-state output target current I1. When the pulse width modulation signal PWM is a low-level signal (i.e., T3-T4), the second control unit is turned on to discharge the first field-effect transistor 1, and the gate voltage V1 of the first field-effect transistor 1 decreases continuously, and the drain output current IOUT of the first field-effect transistor 1 decreases synchronously and continuously. This LED driving circuit can achieve consistency between the actual output current IOUT and the pulse width control of the pulse width modulation signal PWM without any digital compensation or correction. Moreover, the circuit for turning on the acceleration module 4 is simple, requires no factory calibration, and has greater robustness to aging, temperature, and inter-chip differences, making the drive more reliable.

[0101] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. An LED driving circuit, characterized in that, include: The first field-effect transistor has a drain output operating current. A charging module is connected between the gate and source of the first field-effect transistor to provide operating current to the drain of the first field-effect transistor. The charging module includes a first control unit connected to the gate of the first field-effect transistor, and the first control unit controls the slope of the output operating current. The acceleration module is activated and connected to the gate of the first field-effect transistor, driving the gate voltage of the first field-effect transistor to quickly reach the threshold voltage. A signal control module, connected to the charging module and the acceleration module, outputs a pulse width modulation signal and controls the charging module and the acceleration module to turn on and off according to the pulse width modulation signal. The charging module further includes a reference current unit, which includes: The second field-effect transistor has its gate connected to the first reference voltage, its drain connected to the source of the first field-effect transistor, and its source grounded. The second error amplifier has its fourth input terminal connected to the second reference voltage and its fifth input terminal connected to the drain of the second field-effect transistor. The second switch is connected between the second output terminal of the second error amplifier and the gate of the first field-effect transistor, and the sixth input terminal of the second switch is connected to the signal control module.

2. The LED driving circuit according to claim 1, characterized in that, The acceleration activation module includes: A first error amplifier, wherein a threshold voltage is input to the first input terminal of the first error amplifier, and the second input terminal of the first error amplifier is connected to the gate of the first field-effect transistor; A diode, wherein the anode of the diode is connected to the first output terminal of the first error amplifier, and the cathode of the diode is connected to the gate of the first field-effect transistor; A first switch is connected in series with the diode, and the third input terminal of the first switch is connected to the signal control module.

3. The LED driving circuit according to claim 2, characterized in that, The first control unit includes a first adjustable resistor connected in series with the second switch. The third input terminal of the first switch and the sixth input terminal of the second switch are turned on and turned off in response to a high-level signal and a low-level signal in the pulse width modulation signal.

4. The LED driving circuit according to claim 2, characterized in that, The first control unit includes a charging current source connected to the gate of the first field-effect transistor and a third switch connected in series with the charging current source. The seventh input terminal of the third switch is connected to the signal control module.

5. The LED driving circuit according to claim 4, characterized in that, The signal control module includes: The signal generator outputs a pulse width modulation signal; The comparator has its eighth input terminal connected to the gate of the first field-effect transistor, and its ninth input terminal connected to the target voltage. The first AND gate has its tenth input connected to the signal generator, its eleventh input connected to the third output of the comparator, and its fourth output connected to the third input of the first switch and the seventh input of the third switch. The eleventh input of the first AND gate is an inverting input. The second AND gate has its twelfth input connected to the third output of the comparator, its thirteenth input connected to the signal generator, and its fifth output connected to the sixth input of the second switch.

6. The LED driving circuit according to any one of claims 1-5, characterized in that, The LED driving circuit further includes a discharge module connected to the gate of the first field-effect transistor. The discharge module includes a second adjustable resistor connected between the gate of the first field-effect transistor and ground, and a fourth switch connected in series with the second adjustable resistor. The fourteenth input terminal of the fourth switch is turned on in response to a low-level signal and turned off when a high-level signal is received in the pulse width modulation signal.

7. The LED driving circuit according to any one of claims 1, 2, 4, or 5, characterized in that, The LED driving circuit further includes a discharge module connected to the gate of the first field-effect transistor. The discharge module includes a discharge current source connected between the gate of the first field-effect transistor and ground, and a fifth switch connected in series with the discharge current source. The fifteenth input terminal of the fifth switch is turned on in response to a low-level signal and turned off when a high-level signal is received in the pulse width modulation signal.

8. The LED driving circuit according to claim 7, characterized in that, The signal control module includes a NOT gate, the sixteenth input of which is connected to the pulse width modulation signal, and the sixth output of which is connected to the fifteenth input of the fifth switch.

9. A control method for an LED driver circuit, characterized in that, include: The LED driving circuit as described in any one of claims 1-8 is provided; Output pulse width modulation signal; Compare the gate voltage and threshold voltage of the first field-effect transistor; When the gate voltage is less than the threshold voltage, the acceleration module drives the gate voltage of the first field-effect transistor to quickly reach the threshold voltage. When the gate voltage is greater than or equal to the threshold voltage, the charging module provides operating current to the drain of the first field-effect transistor. When the gate voltage reaches the target voltage, the reference current unit is the drain output operating current of the first field-effect transistor.

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