CN112020169B - Light modulation controller capable of receiving pulse width modulation signal and direct current signal and light modulation method - Google Patents

Abstract

The invention provides a dimming controller, which is suitable for dimming a light-emitting component, and includes a dimming input terminal, a signal recognizer, a selector and a DC-to-PWM converter. The dimming input receives a dimming signal, which is DC or PWM. The signal recognizer is connected to the dimming input end, and is used for identifying whether the dimming signal on the dimming input end is direct current or PWM. The selector is connected to the dimming input through different DC signal paths and PWM signal paths, controlled by the signal recognizer. The DC-to-PWM converter is coupled to the selector for converting the DC signal into a PWM signal for dimming the light-emitting component. When the signal recognizer thinks that the dimming signal is a direct current, the signal recognizer enables the selector to select a direct current signal path to connect the dimming input end to the DC to PWM converter. When the signal recognizer thinks that the dimming signal is PWM, the signal recognizer makes the selector select the PWM signal path to connect the dimming input end to the DC-to-PWM converter.

Description

Dimming controller capable of receiving pulse width modulation signal and DC signal and dimming method

technical field

The invention relates to a dimming controller and a related dimming method, in particular to a dimming controller capable of receiving different forms of dimming signals and a related dimming method.

Background technique

Good luminous efficiency, compact component size, and long component life make light-emitting diodes (LEDs) widely used in lighting or backlight industries. For example, most of the backlight modules in computer or TV screens have been converted from traditional cold cathode tube (Cold Cathode Fluorescent Lamp, CCFL) modules to LED modules.

LED modules often need to have the function of adjusting the brightness of the screen. Therefore, most LED modules have a dimming controller. Generally, there are two dimming methods in the industry: pulse-width-modulation (PWM) dimming (PWM dimming), and analog dimming (analog dimming). PWM dimming is also called digital dimming. PWM dimming uses a PWM signal that jumps between logic values 0 and 1 to determine the ratio of the LED module's light-emitting time to the entire cycle time, that is, the duty cycle (dutycycle); and during the light-emitting time, the LED module's The luminous brightness is a fixed value; during the non-luminous time other than the luminous time, the LED module generally does not emit light. In contrast, the LED module using analog dimming (also known as resistive dimming) emits light continuously, but its brightness is controlled by a direct-current (DC) signal. DC signals are also called analog (analog) signals.

Preferably, the dimming controller can receive a DC signal or a PWM signal, so that the dimming controller can be widely used.

Contents of the invention

An embodiment of the present invention provides a dimming controller suitable for dimming a light-emitting component. The dimming controller includes a dimming input terminal, a signal recognizer, a selector, and a DC-to-PWM converter. The dimming input terminal can receive a dimming signal, which can be DC or PWM. The signal recognizer is connected to the dimming input end, and is used for identifying whether the dimming signal on the dimming input end is direct current or PWM. The selector can be connected to the dimming input terminal through different DC signal paths and a PWM signal path, and is controlled by the signal recognizer. The DC-to-PWM converter is coupled to the selector for converting a DC signal into a PWM signal for dimming the light-emitting component. When the signal recognizer thinks that the dimming signal is DC, the signal recognizer makes the selector select the DC signal path to connect the dimming input end to the DC-to-PWM converter. When the signal recognizer considers the dimming signal to be PWM, the signal recognizer enables the selector to select the PWM signal path to connect the dimming input terminal to the DC-to-PWM converter.

An embodiment of the present invention provides a dimming method, which is suitable for dimming a light-emitting component. The dimming method includes: receiving a dimming signal, which can be DC or PWM; identifying whether the dimming signal is DC or PWM; providing a DC signal path and a PWM signal path; when the dimming signal is DC When the DC signal path is selected to generate a DC signal; when the dimming signal is PWM, the PWM signal path is selected to generate the DC signal; and the DC signal is converted to generate a PWM signal, It is used for dimming the light-emitting component.

Description of drawings

FIG. 1 shows a dimming controller implemented according to the present invention.

Figure 2 shows a dimming controller that can be used in Figure 1.

FIG. 3 shows a DC-to-digital PWM control conversion unit, for example showing the waveforms of the dimming signal S _DIM , the sawtooth wave S _SAW , and the PWM signal S _PWM .

FIG. 4 shows that the dimming signal _SDIM has two falling edges FA1 and FA2 and one rising edge RA1 .

FIG. 5 shows an example of the dimming method adopted by the dimming controller in FIG. 2 .

Figure 6 shows another dimming controller that can be used in Figure 1.

FIG. 7 shows an example of the dimming method adopted by the dimming controller in FIG. 6 .

Figure 8 shows another dimming controller that can be used in Figure 1.

FIG. 9 shows an example of the dimming method adopted by the dimming controller in FIG. 8 .

Figure 10 shows another dimming controller that can be used in Figure 1.

FIG. 11 shows an example of the dimming method adopted by the dimming controller in FIG. 10 .

List of reference signs

10, 10a, 10b, 10c, 10d: dimming controller

12: Signal Recognizer

14a, 14b: LED driver

15: Low pass filter

16, 16a: DC to PWM converter

17a, 17b: selector

18: Digital buffer

19: PWM to DC converter

20: Signal generator

22: Comparator

24: Operational amplifier

26:68c

28: Voltage level converter

30: Operational amplifier

31: constant current source

60a, 60b, 60c: dimming method

62, 64, 67, 68a, 68b, 68c, 70a, 70b, 70c, 70d, 72a, 72b, 74, 76: steps

C1: capacitance

CS: current detection terminal

DIM: dimming input

DRV: drive end

FA1, FA2: falling edge

GND: ground wire

I _SET : constant current

LT: light emitting component

MNDRV: power transistor

PTH _DC : DC signal path

PTH _PWM : PWM signal path

RA1: rising edge

RCS: current sense resistor

R1: Resistor

RDIM: variable resistor

SB _PWM : temporary PWM signal

SC _PWM : PWM signal

S _DC : DC signal

S _DIM : dimming signal

S _DIM-PWM : PWM signal

S _DRV : Drive signal

SD _DC : DC signal

_SDXX : output

S _PWM : PWM signal

S _SAW : sawtooth wave

S _SEL : select signal

T _DELAY : scheduled delay

V _CS : Current detection signal

V _DC : DC signal

V _REF , V _REF-L , V _REF-H : Reference voltage

Detailed ways

In this specification, there are some same symbols, which represent components with the same or similar structure, function, and principle, and can be deduced by those skilled in the art based on the teaching of this specification. For the sake of brevity in the description, components with the same symbols will not be repeated.

FIG. 1 shows a dimming controller 10 implemented according to the present invention, which is suitable for dimming a light-emitting component LT by controlling a power transistor MNDRV.

The power transistor MNDRV may be an NMOS transistor, and the light emitting element LT may be one or several light-emitting diodes (LEDs) connected in series or in parallel. The dimming controller 10 provides a driving signal S _DRV through the driving terminal DRV to control the power transistor MNDRV. The driving signal S _DRV may be a PWM signal or a DC signal. The current flowing through the light-emitting component LT passes through the current detection resistor RCS to generate a current detection signal V _CS , which is received by the dimming controller 10 through the current detection terminal CS. The dimming controller 10 receives a dimming signal _SDIM from a dimming input terminal DIM, and generates a driving signal S _DRV accordingly.

As shown in FIG. 1 , the dimming controller 10 can accept three different external signal input modes to perform dimming. The first one is that the outside provides a DC signal V _DC to the dimming input terminal DIM as the dimming signal S _DIM , and the voltage level of the DC signal V _DC represents the average brightness that the light emitting element LT should produce. The second is to connect a variable resistor RDIM between the dimming input terminal DIM and a ground wire GND. It will be explained later that the resistance value of the variable resistor RDIM will be converted into a voltage of a DC signal on the dimming input terminal DIM. Level, which represents the average brightness of the light emitting component LT. The third is that the outside provides the PWM signal _SDIM-PWM to the dimming input terminal DIM as the dimming signal _SDIM , and the duty cycle of the PWM signal SDIM _-PWM represents the average brightness of the light-emitting component LT.

In other words, the dimming signal _SDIM may be a DC signal or a PWM signal. The dimming signal _SDIM may be one of two forms, and these two forms are DC and PWM.

FIG. 2 shows a dimming controller 10a, which can be used as the dimming controller 10 in FIG. 1 in an embodiment. The dimming controller 10 a includes a signal recognizer 12 , a DC-to-PWM converter 16 , a selector 17 a, an LED driver 14 a, and a constant current source 31 .

The DC-to-PWM converter 16 is a form converter. If the dimming signal _SDIM is a DC signal, the DC-to-PWM converter 16 can convert it to provide a corresponding PWM signal S _PWM . In FIG. 2 , the DC-to-PWM converter 16 includes a signal generator 20 , an operational amplifier 24 , and a comparator 22 . Please also refer to Figure 3. Fig. 3 shows the dimming signal _SDIM— approximately a DC signal is converted into a digital PWM control conversion unit through a DC. For example, a commonly used circuit such as the operational amplifier 24 is structured as a Unity-Gain Buffer, which reproduces the voltage level of the dimming signal _SDIM to the non-inverting input terminal of the comparator 22 . The signal generator 20 generates a sawtooth wave S _SAW , which is provided to the inverting input terminal of the comparator 22 . The comparator 22 compares the dimming signal _SDIM with the sawtooth wave S _SAW to generate the PWM signal S _PWM , that is, the function as shown in FIG. 3 .

The signal recognizer 12 is connected to the dimming input terminal DIM for identifying whether the dimming signal _SDIM on the dimming input terminal DIM is DC or PWM, so as to generate a selection signal S _SEL , which controls the selector 17a. In the embodiment of FIG. 2, when the selection signal S _SEL is logically 1, it means that the signal recognizer 12 considers the dimming signal _SDIM to be a PWM signal; on the contrary, when the signal recognizer 12 considers the dimming signal _SDIM to be In the case of a DC signal, the selector 17a makes the selection signal S _SEL logic 0.

In one embodiment, the signal recognizer 12 determines the selection signal S _SEL according to the signal edge of the dimming signal _SDIM . Please refer to FIG. 4 , which shows that the dimming signal _SDIM has two falling edges FA1 and FA2 and one rising edge RA1 . The signal recognizer 12 can generate the selection signal according to whether there are enough falling edges and rising edges whose absolute values of slopes are greater than a predetermined value within a predetermined time. For example, if the signal recognizer 12 finds that there are more than 4 falling edges and rising edges in 8ms, and the absolute values of the slopes are greater than 0.1V/us, then it is determined that the dimming signal _SDIM is a PWM signal. The selection signal S _SEL is logically 1. On the contrary, if there are no more than 4 falling and rising edges whose slope absolute value is greater than 0.1V/us in 8ms, then it is determined that the dimming signal _SDIM is a DC signal, so that the selection signal S _SEL is logical 0.

For example, in FIG. 4 , the signal recognizer 12 regards the dimming signal _SDIM as falling below the reference voltage V _REF-H as the beginning of the falling edge FA1 . Then compare the dimming signal _SDIM after a predetermined delay T _DELAY with the reference voltage V _REF-L to determine whether the absolute value of the slope of the falling edge FA1 is greater than (V _REF-H −V _REF-L )/T _DELAY . In a similar manner, the signal recognizer 12 regards the dimming signal _SDIM as high as crossing the reference voltage V _REF-L as the beginning of the rising edge RA1 . Then compare the dimming signal _SDIM after a predetermined delay T _DELAY with the reference voltage V _REF-H to determine whether the absolute value of the slope of the rising edge RA1 is greater than (V _REF-H −V _REF-L )/T _DELAY . In another embodiment, the signal recognizer 12 can also recognize a falling edge according to whether the falling time of the dimming signal _SDIM from the reference voltage V _REF-H to the reference voltage V _REF-L is greater than the predetermined delay T _DELAY Is it steep enough to represent the falling edge of a PWM signal. Similarly, the signal recognizer 12 can also recognize whether a rising edge is steep enough according to whether the rising time of the dimming signal _SDIM from the reference voltage V _REF-L to the reference voltage V _REF-H is greater than the predetermined delay T _DELAY Represents the rising edge of a PWM signal.

The selector 17 a in FIG. 2 is controlled by the signal recognizer 12 and has two inputs for respectively receiving the PWM signal S _PWM and the dimming signal S _DIM . The selector 17 a includes a digital buffer 18 and a multiplexer (multiplexer) 26 . When the signal recognizer 12 considers the dimming signal _SDIM to be a DC signal, the selector 17a selects the PWM signal S _PWM and transmits it to the LED driver 14a. When the signal recognizer 12 considers the dimming signal _SDIM to be a PWM signal, the dimming signal _SDIM is transmitted to the multiplexer 26 through the digital buffer 18, selected by it and transmitted to the LED driver 14a. In other words, if the output of the multiplexer 26 is not the PWM dimming signal _SDIM , it is the PWM signal S _PWM representing the DC dimming signal _SDIM .

The selection signal S _SEL shown in FIG. 2 only controls the selector 17a, but the present invention is not limited thereto. For example, in one embodiment, when the signal recognizer 12 considers that the dimming signal _SDIM is a PWM signal, the signal recognizer 12 makes the DC-to-PWM converter 16 completely shut down by selecting the signal S _SEL , so as to save electrical energy. Similarly, when the signal recognizer 12 considers the dimming signal _SDIM to be a DC signal, the digital buffer 18 can also be selectively turned off to save unnecessary power consumption.

The LED driver 14 a controls the power transistor MNDRV according to the output of the multiplexer 26 , so as to control the current flowing through the light emitting element LT. When the output of the multiplexer 26 is logic 1, the voltage level converter 28 outputs the reference voltage V _REF , so the operational amplifier 30 controls the power transistor MNDRV so that the current of the light-emitting component LT is about V _REF /R _CS , where R _CS is the resistance value of the current detection resistor RCS. When the output of the multiplexer 26 is logic 0, the voltage level converter 28 outputs 0V, so that the current of the light emitting element LT is about 0.

The constant current source 31 provides a constant current I _SET , which flows through the dimming input terminal DIM and can be used to generate a DC dimming signal _SDIM . If there is a variable resistor RDIM between the dimming input terminal DIM and the ground wire GND, the constant current I _SET can flow through the variable resistor RDIM, and a DC voltage is generated at the dimming input terminal DIM as a dimming signal S _DIM . When the outside directly provides the DC signal V _DC or the PWM signal S _DIM-PWM as the dimming signal S _DIM , the constant current I _SET generally does not affect the DC signal V _DC or the PWM signal S _DIM-PWM .

FIG. 5 shows an example of a dimming method 60 a adopted by the dimming controller 10 a in FIG. 2 .

In step 62, the dimming controller 10a receives the dimming signal _SDIM through the dimming input terminal DIM, which can be a PWM signal or a DC signal.

Step 64 continues step 62 . The signal recognizer 12 recognizes whether the dimming signal _SDIM on the dimming input terminal DIM is DC or PWM, so as to generate a selection signal S _SEL , which controls the selector 17a.

Step 68a is continued after the signal recognizer 12 considers the dimming signal _SDIM to be a DC signal. The DC-to-PWM converter 16 converts the dimming signal _SDIM to provide a corresponding PWM signal S _PWM .

Step 70a follows step 68a. The selector 17a selects the PWM signal S _PWM and transmits it to the LED driver 14a for driving the light emitting element LT. At this moment, the signal path between the dimming signal _SDIM through the digital buffer 18 and the LED driver 14a is interrupted.

Step 72a is continued after the signal recognizer 12 considers the dimming signal _SDIM to be a PWM signal. The selector 17a selects the dimming signal _SDIM and transmits it to the LED driver 14a through the digital buffer 18 and the multiplexer 26 to drive the light emitting element LT. At this time, the selector 17a does not transmit the PWM signal S _PWM to the LED driver 14a.

The dimming controller 10a in FIG. 2 and the dimming method 60a in FIG. 5 have the following advantages. When the dimming signal _SDIM is a DC signal, a corresponding PWM signal S _PWM can be generated for the LED driver 14 a to drive the light emitting element LT. When the dimming signal _SDIM is a PWM signal, the dimming signal _SDIM is directly sent to the LED driver 14a, which can faithfully and accurately reflect the actual required dimming state. In other words, regardless of whether the dimming signal _SDIM is a DC signal or a PWM signal, the dimming controller 10a can properly drive the light emitting element LT.

FIG. 6 shows a dimming controller 10b, which can be used as the dimming controller 10 in FIG. 1 in an embodiment. The dimming controller 10b includes a signal recognizer 12 , a PWM-to-DC converter 19 , a selector 17b , an LED driver 14b , and a constant current source 31 . In FIG. 6 , some devices have been disclosed in FIG. 2 , and their operations can be known from the relevant explanations in FIG. 2 , and will not be repeated here.

The PWM-to-DC converter 19 is a form converter. If the dimming signal S _DIM is a PWM signal, the PWM-to-DC converter 19 can convert it to provide a corresponding DC signal S _DC . In FIG. 6 , the PWM-to-DC converter 19 includes a digital buffer 18 , a resistor R1 and a capacitor C1 . The digital buffer 18 reproduces the logic value of the dimming signal _SDIM and supplies it to the resistor R1. The resistor R1 and the capacitor C1 form a low-pass filter, which can generate a direct current signal S _DC , which roughly represents the duty cycle of the dimming signal _SDIM .

The selector 17b in FIG. 6 is controlled by the signal recognizer 12 and has two inputs for respectively receiving the DC signal S _DC and the dimming signal S _DIM . The selector 17 b includes an operational amplifier 24 and a multiplexer 26 . When the signal recognizer 12 considers that the dimming signal _SDIM is a DC signal, the operational amplifier 24, as a unity gain buffer, transmits the dimming signal _SDIM to the multiplexer 26, which then transmits the dimming signal _SDIM to the LED Driver 14b. When the signal recognizer 12 considers the dimming signal _SDIM to be a PWM signal, the selector 17b selects the DC signal S _DC and transmits it to the LED driver 14b. In other words, if the output of the multiplexer 26 is not the DC dimming signal _SDIM , it is the DC signal S _DC representing the PWM dimming signal _SDIM .

The LED driver 14b controls the power transistor MNDRV according to the output of the multiplexer 26, so as to control the current flowing through the light emitting element LT. For example, when the voltage level of the output of the multiplexer 26 is V _OUT , the operational amplifier 30 controls the power transistor MNDRV so that the current of the light emitting element LT is approximately V _OUT /R _CS .

FIG. 7 shows an example of a dimming method 60b adopted by the dimming controller 10b of FIG. 6 . Some steps of the dimming method 60b are the same as or similar to those of the dimming method 60a, which can be known from the previous description of the dimming method 60a or the dimming controller 10a, and will not be repeated here.

Step 72b is continued after the signal recognizer 12 considers the dimming signal _SDIM to be a DC signal. The selector 17b transmits the dimming signal _SDIM to the LED driver 14b, which drives the light emitting element LT accordingly.

Step 68b is continued after the signal recognizer 12 considers the dimming signal _SDIM to be a PWM signal. The PWM-to-DC converter 19 converts the dimming signal _SDIM to provide a corresponding DC signal S _DC .

Step 70b follows step 68b. The selector 17b selects the DC signal S _DC and transmits it to the LED driver 14b for driving the light emitting element LT. At this time, the signal path from the dimming signal _SDIM to the LED driver 14b via the operational amplifier 24 is interrupted.

The selection signal S _SEL shown in FIG. 6 only controls the selector 17b, but the present invention is not limited thereto. For example, in one embodiment, when the signal recognizer 12 considers the dimming signal _SDIM to be a PWM signal, the signal recognizer 12 disables or turns off the operational amplifier 24 by selecting the signal S _SEL to save electrical energy. Similarly, when the signal recognizer 12 considers the dimming signal _SDIM to be a DC signal, the digital buffer 18 can also be selectively turned off to save unnecessary power consumption.

The dimming controller 10b in FIG. 6 and the dimming method 60b in FIG. 7 have the following advantages. When the dimming signal _SDIM is a direct current signal, it can be directly transmitted to the LED driver 14 b faithfully to drive the light emitting component LT. When the dimming signal _SDIM is a PWM signal, the PWM-to-DC converter 19 generates a corresponding DC signal S _DC to the LED driver 14b for driving the light-emitting element LT. Therefore, regardless of whether the dimming signal _SDIM is DC or PWM, the dimming controller 10b can provide an appropriate DC signal to the LED driver 14b.

The present invention is not limited to only driving LEDs, and in other embodiments, other light emitting devices can also be driven.

FIG. 8 shows a dimming controller 10c, which can be used as the dimming controller 10 in FIG. 1 in an embodiment. The dimming controller 10c includes a signal recognizer 12 , a PWM-to-DC converter 19 , a selector 17b , a DC-to-PWM converter 16a , an LED driver 14a , and a constant current source 31 . In FIG. 8 , some devices have been disclosed in FIG. 2 and FIG. 6 , and their operations can be known from the previous explanations in FIG. 2 and FIG. 6 , and will not be repeated here.

The PWM-to-DC converter 19 is a form converter. If the dimming signal S _DIM is a PWM signal, the PWM-to-DC converter 19 can convert it to provide a corresponding DC signal S _DC . In FIG. 8 , the PWM-to-DC converter 19 includes a digital buffer 18 and a low-pass filter 15 . The digital buffer 18 reproduces the logic value of the dimming signal _SDIM to generate a temporary PWM signal SB _PWM , which is provided to the resistor R1. The low-pass filter 15 has a resistor R1 and a capacitor C1 for low-pass filtering the temporary PWM signal SB _PWM to generate a DC signal S _DC approximately representing the duty cycle of the dimming signal _SDIM .

The duty cycle of the temporary PWM signal SB _PWM is the same as the duty cycle of the dimming signal _SDIM , but the logic level of the logic "1" of the temporary PWM signal SB _PWM is not necessarily the same as the logic level of the dimming signal _SDIM . 1" logic level. For example, when the dimming signal _SDIM is logic “0”, its logic level is 0V; when the dimming signal _SDIM is logic “1”, its logic level may be 1V, 3V or 5V. The logic level of the logic "0" of the temporary PWM signal SB _PWM is 0V, and the logic level of the logic "1" must be the default 5V. Therefore, the digital buffer 18 can also be regarded as a level shifter, which can make the temporary PWM signal SB _PWM have a default logic level regardless of the logic level of the logic “1” of the dimming signal _SDIM .

The selector 17b in FIG. 8 is controlled by the signal recognizer 12 and has two inputs for respectively receiving the DC signal S _DC and the dimming signal S _DIM . The selector 17 b includes an operational amplifier 24 and a multiplexer 26 . When the signal recognizer 12 considers the dimming signal _SDIM to be a DC signal, the operational amplifier 24, as a unity gain buffer, transmits the dimming signal _SDIM to the multiplexer 26 as a DC signal SD _DC to the DC converter PWM converter 16a. When the signal recognizer 12 considers the dimming signal _SDIM to be a PWM signal, the selector 17b selects the DC signal S _DC as the DC signal SD _DC and transmits it to the DC-to-PWM converter 16a. In other words, if the output of the multiplexer 26 (the direct current signal SD _DC ) is not the direct current dimming signal _SDIM , it is the direct current signal S _DC representing the PWM dimming signal _SDIM .

The selector 17b is equivalently connected to the dimming input terminal DIM through different direct current signal paths PTH _DC and PWM signal paths PTH _PWM . The digital buffer 18 and the low-pass filter 15 in the PWM-to-DC converter 19 are both located on the PWM signal path PTH _PWM . When the signal recognizer 12 considers the dimming signal _SDIM to be DC, the signal recognizer 12 makes the selector 17b select the DC signal path PTH _DC to connect the dimming input terminal DIM to the DC-to-PWM converter 16a. When the signal recognizer 12 considers the dimming signal _SDIM to be PWM, the signal recognizer 12 makes the selector 17b select the PWM signal path PTH _PWM to connect the dimming input terminal DIM to the DC-to-PWM converter 16a.

The DC-to-PWM converter 16a is used to convert the DC signal SD _DC to provide a corresponding PWM signal SC _PWM . In FIG. 8 , the DC-to-PWM converter 16 a includes a signal generator 20 and a comparator 22 . The signal generator 20 generates a sawtooth wave S _SAW , which is provided to the inverting input terminal of the comparator 22 . The comparator 22 compares the DC signal SD _DC with the sawtooth wave S _SAW to generate the PWM signal SC _PWM , similar to the function shown in FIG. 3 . In this way, the frequency of the PWM signal SC _PWM is approximately a constant value, which has nothing to do with the original dimming signal _SDIM . Moreover, the logic level of the PWM signal SC _PWM , whether it is logically “0” or “1”, can be properly customized for the LED driver 14 a.

The LED driver 14a in FIG. 8 controls the power transistor MNDRV according to the PWM signal SC _PWM , so as to control the current flowing through the light emitting element LT.

FIG. 9 shows an example of a dimming method 60c adopted by the dimming controller 10c of FIG. 8 . Some steps of the dimming method 60c are the same as or similar to those of the dimming methods 60a and 60b, which can be known from the previous dimming methods 60a, 60b and related descriptions, and will not be repeated here.

Step 72b is continued after the signal recognizer 12 considers the dimming signal _SDIM to be a DC signal. The selector 17b selects the DC signal path PTH _DC to transmit the dimming signal _SDIM as the DC signal SD _DC .

Step 67 is continued after the signal recognizer 12 considers the dimming signal _SDIM to be PWM. The digital buffer 18 reproduces the logic value of the dimming signal _SDIM to generate a temporary PWM signal SB _PWM with a default logic level.

In FIG. 9, step 68b follows step 67, the low-pass filter 15 converts the temporary PWM signal SB _PWM to generate a corresponding DC signal S _DC .

In FIG. 9 , step 70c follows step 68b, and the selector 17b selects the DC signal S _DC as the DC signal SD _DC .

In step 74, the DC-to-PWM converter 16a converts the DC signal SD _DC to provide the PWM signal SC _PWM .

In step 76 , the LED driver 14 a controls the power transistor MNDRV according to the PWM signal SC _PWM , so as to control the current flowing through the light emitting element LT.

The dimming controller 10c of FIG. 8 and the dimming method 60c of FIG. 9 have the following advantages. Regardless of whether the dimming signal _SDIM is DC or PWM, the dimming controller 10c can generate a corresponding PWM signal SC _PWM with a fixed frequency and a fixed logic level to control the current flowing through the light emitting element LT.

The multiplexers 26 in the dimming controllers 10a, 10b and 10c are all used to select one of the two signals with the same form to output. The multiplexer 26 in the dimming controller 10a selects one of the two PWM signals for output. The multiplexer 26 in the dimming controllers 10b and 10c selects one of the two DC signals for output. But the present invention is not limited thereto. In some embodiments, the multiplexer 26 can select one of two signals of different forms to output.

FIG. 10 shows a dimming controller 10d, which can be used as the dimming controller 10 in FIG. 1 in an embodiment. The same and similar devices in the dimming controller 10d and the dimming controller 10c have been disclosed in FIG. 8 and the corresponding descriptions, and their operations can be known from the previous related explanations in FIG. 8 and FIG. 9 , and will not be repeated here. The dimming controller 10d may have the same functions and benefits as the dimming controller 10c.

The low-pass filter 15 in the dimming controller 10 c is connected between the multiplexer 26 and the digital buffer 18 . Different from the dimming controller 10c, the low-pass filter 15 in the dimming controller 10d is connected between the multiplexer 26 and the comparator 22 .

In FIG. 10, the selector 17b (including the operational amplifier 24 and the multiplexer 26) can select one of the dimming signal _SDIM and the temporary PWM signal SB _PWM according to the selection signal S _SEL output by the signal recognizer 12. One, as the output SD _XX , is sent to the low-pass filter 15 , which generates a direct current signal SD _DC .

When the signal recognizer 12 considers that the dimming signal _SDIM is DC, the selector 17 b uses the DC signal path PTH _DC to generate the DC signal SD _DC . At this time, although there may be a delay, the low-pass filter 15 does not affect the voltage level of the dimming signal _SDIM , and can faithfully generate a DC signal _SD having the same voltage level as the dimming signal SDIM _DC .

When the signal recognizer 12 considers that the dimming signal _SDIM is PWM, the selector 17 b uses the PWM signal path PTH _PWM to generate the DC signal SD _DC . At this time, the digital buffer 18 can be regarded as a level shifter, which can make the temporary PWM signal SB _PWM have a default logic level regardless of the logic level of the logic “1” of the dimming signal _SDIM . The low-pass filter 15 performs low-pass filtering on the temporary PWM signal SB _PWM to generate a corresponding DC signal SD _DC .

FIG. 11 shows an example of a dimming method 60d adopted by the dimming controller 10d of FIG. 10 . Some steps of the dimming method 60d are the same or similar to those of the dimming method 60c, which can be known from the previous dimming method 60c and related descriptions, and will not be repeated here.

Different from the dimming method 60c, in the dimming method 60d, step 70d follows step 67, and the selector 17b selects the temporary PWM signal SB _PWM as the output SD _XX .

Different from the dimming method 60c, in the dimming method 60d, step 68c follows steps 72b and 70d, and the low-pass filter 15 performs low-pass filtering on the temporary PWM signal SB _PWM to generate a corresponding DC signal SD _CS .

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (8)

1. A dimming controller adapted to dim a light emitting assembly, comprising:

the light modulation input end receives a light modulation signal, and the light modulation signal is direct current or PWM;

the signal identifier is connected to the dimming input end and used for identifying that the dimming signal positioned on the dimming input end is direct current or PWM;

the selector is connected to the dimming input end through different direct current signal paths and PWM signal paths and is controlled by the signal identifier; and

the direct current-to-PWM converter is coupled to the selector and used for converting a direct current signal into a PWM signal for dimming the light-emitting component;

when the signal identifier considers that the dimming signal is direct current, the signal identifier enables the selector to select the direct current signal path to connect the dimming input end to the direct current-to-PWM converter; and

when the signal identifier considers the dimming signal to be PWM, the signal identifier enables the selector to select the PWM signal path to connect the dimming input end to the direct current-to-PWM converter,

wherein, the dimming controller still contains:

the digital buffer is located on the PWM signal path and is used for generating a temporary PWM signal according to the dimming signal, wherein the temporary PWM signal has a specific logic level.

2. The dimmer controller of claim 1, comprising:

the PWM-to-DC converter is positioned on the PWM signal path and provides the DC signal according to the temporary PWM signal.

3. The dimmer controller of claim 1, further comprising:

the PWM-to-DC converter is connected between the output of the selector and the DC-to-PWM converter and generates the DC signal according to the dimming signal.

4. The dimmer controller of claim 1, the selector comprising:

the unit gain buffer is used for transmitting the dimming signal to the direct current-to-PWM converter when the dimming signal is direct current.

5. The dimming controller of claim 1, the dc-to-PWM converter comprising:

a signal generator for generating a periodic signal; and

the comparator is used for comparing the periodic signal with the direct current signal to generate the PWM signal.

6. A dimming method for dimming a light emitting assembly, comprising:

receiving a dimming signal, wherein the dimming signal is direct current or PWM;

identifying the dimming signal as direct current or PWM;

providing a direct current signal path and a PWM signal path;

when the dimming signal is direct current, selecting the direct current signal path to generate a direct current signal;

when the dimming signal is PWM, selecting the PWM signal path for generating the DC signal;

converting the direct current signal to generate a PWM signal for dimming the light emitting component;

when the dimming signal is PWM, generating a temporary PWM signal according to the dimming signal, wherein the temporary PWM signal has a default logic level; and

the temporary PWM signal is converted to provide the dc signal.

7. The dimming method of claim 6, wherein the step of converting the temporary PWM signal comprises:

the temporary PWM signal is low pass filtered to provide the dc signal.

8. The dimming method of claim 6, comprising:

and providing a unit gain buffer arranged on the direct current signal path and used for providing the direct current signal according to the dimming signal when the dimming signal is direct current.

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