TWI697255B - Dimming controllers and related dimming methods capable of receiving pulse-width-modulation signal and direct-current signal - Google Patents

Abstract

Disclosure provides a dimming controller suitable for the use of dimming a light emitting device. The dimming controller has a dimming node, a signal-type identifier, a selector and an DC-to-PWM converter. The signal-type identifier is connected to the dimming node, a dimming signal on which is of either PWM or DC, to tell whether the dimming signal is of PWM or of DC. The selector is capable of coupled to the dimming node via DC and PWM signal paths. The DC-to-PWM converter converts a DC signal into a PWM signal for dimming the light emitting device. When the signal-type identifier deems the dimming signal as of DC, the signal-type identifier makes the selector select the DC path to connect the dimming node to the DC-to-PWM converter. When the signal-type identifier deems the dimming signal as of PWM, the signal-type identifier makes the selector select the PWM path to connect the dimming node to the DC-to-PWM converter.

Description

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

The invention relates to a dimming controller and related dimming method, in particular to a dimming controller and related dimming method that can receive different types of dimming signals.

Good luminous efficiency, streamlined component size, and long component life have made light-emitting diodes (LEDs) widely used in the lighting or backlight industry. For example, most backlight modules in computers or television 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, so most of the LED modules have dimming controllers. There are two general dimming methods in the industry: pulse-width-modulation (PWM) dimming (PWM dimming) and analog dimming (analog dimming). PWM dimming is also known as digital dimming. PWM dimming uses a PWM signal that jumps between logic values 0 and 1 to determine the ratio of the LED module to the light-emitting time to the entire cycle time, that is, the duty cycle; and during the light-emitting time, the LED The light emitting brightness of the module is a fixed value; the LED module does not emit light during the non-lighting time outside the light emitting time. In contrast, LED modules that use analog dimming (also called resistive dimming) have a continuous light emission Intermittent, but its brightness is controlled by a direct-current (DC) signal. DC signals are also called analog signals.

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

An embodiment of the present invention provides a dimming controller, which is suitable for dimming a light-emitting element. The dimming controller includes a dimming input terminal, a signal identifier, a selector, and a DC converter. The dimming input terminal can receive a dimming signal, which can be DC or PWM. The signal identifier is connected to the dimming input terminal, and is used for identifying whether the dimming signal on the dimming input terminal is DC or PWM. The selector can be connected to the dimming input through a different DC signal path and a PWM signal path, controlled by the signal identifier. The DC-to-PWM converter is coupled to the selector to convert the DC signal into a PWM signal for dimming the light-emitting element. When the signal recognizer considers the dimming signal to be DC, the signal recognizer causes the selector to select the DC signal path to connect the dimming input to the DC-to-PWM converter. When the signal recognizer considers the dimming signal to be PWM, the signal recognizer causes the selector to select the PWM signal path to connect the dimming input to the DC-to-PWM converter.

An embodiment of the present invention provides a dimming method, which is suitable for dimming a light-emitting element. 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 Select the DC signal path to generate a DC signal; when the dimming signal is PWM, select the PWM signal path to generate the DC signal; and, The DC signal is converted to generate a PWM signal for dimming the light-emitting element.

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

12‧‧‧Sign 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‧‧‧Multiplexer

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‧‧‧

C1‧‧‧Capacitance

CS‧‧‧current detection terminal

DIM‧‧‧Dimming input

DRV‧‧‧Drive

FA1, FA2‧‧‧falling edge

GND‧‧‧Ground wire

I _SET ‧‧‧ Constant current

LT‧‧‧Lighting element

MNDRV‧‧‧Power Transistor

PTH _DC ‧‧‧DC signal path

PTH _PWM ‧‧‧PWM signal path

RA1‧‧‧Rising edge

RCS‧‧‧Current detection resistor

R1‧‧‧Resistance

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

SD _XX ‧‧‧ output

S _PWM ‧‧‧PWM signal

S _SAW ‧‧‧Sawtooth wave

S _SEL ‧‧‧selection signal

T _DELAY ‧‧‧Scheduled delay

V _CS ‧‧‧ Current detection signal

V _DC ‧‧‧DC signal

V _REF , V _REF-L , V _REF-H ‧‧‧ reference voltage

Figure 1 shows a dimming controller implemented in accordance with the present invention.

Figure 2 shows a dimming controller that can be applied to Figure 1.

Figure 3 shows the control conversion unit that has been converted to digital PWM all the time. Examples show the waveforms of dimming signal S _DIM , sawtooth wave S _SAW , and PWM signal S _PWM .

Figure 4 shows that the dimming signal S _DIM has two falling edges FA1 and FA2, and one rising edge RA1.

Figure 5 shows an example of the dimming method used by the dimming controller of Figure 2.

Figure 6 shows another dimming controller that can be applied to Figure 1.

Figure 7 shows an example of the dimming method used in the dimming controller of Figure 6.

Figure 8 shows another dimming controller that can be applied to Figure 1.

Figure 9 shows an example of the dimming method used in the dimming controller of Figure 8.

Figure 10 shows another dimming controller that can be applied to Figure 1.

Figure 11 shows an example of the dimming method used in the dimming controller of Figure 10.

In this specification, there are some same symbols, which represent components with the same or similar structure, function, and principle, and those with general knowledge in the industry can infer according to the teaching of this specification. For the sake of brevity of the manual, elements with the same symbol will not be restated.

Figure 1 shows a dimming controller 10 implemented according to the present invention The power transistor MNDRV is suitable for dimming the light emitting element LT.

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 element 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 the dimming signal S _DIM from the dimming input terminal DIM, and accordingly generates the driving signal S _DRV .

As shown in FIG. 1, the dimming controller 10 can accept three different signal input methods from the outside to perform dimming. The first is to provide 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 line GND. The resistance value of the variable resistor RDIM will be converted into a voltage of the DC signal on the dimming input terminal DIM later. Level, which represents the average brightness of the light emitting element LT. The third is that the external provides the PWM signal S _DIM-PWM to the dimming input terminal DIM as the dimming signal S _DIM , and the duty cycle of the PWM signal S _DIM-PWM represents the average brightness of the light emitting element LT.

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

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

The DC-to-PWM converter 16 is a type converter. If the dimming signal S _DIM 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. Figure 3 shows that the dimming signal S _{DIM is} approximately a DC-to-DC signal conversion control unit after DC-to-DC conversion. For example, a common circuit such as an operational amplifier 24 is constructed as a Unity-Gain Buffer, and the voltage level of the dimming signal S _DIM is reproduced at the non-inverting input terminal of the comparator 22. The signal generator 20 generates a sawtooth wave S _SAW and provides it to the inverting input of the comparator 22. The comparator 22 compares the dimming signal S _DIM and the sawtooth wave S _SAW to generate the PWM signal S _PWM , which is the function shown in FIG. 3.

The signal identifier 12 is connected to the dimming input terminal DIM to identify whether the dimming signal S _DIM located on the dimming input terminal _DIM is DC or PWM, and accordingly generates a selection signal S _SEL , which controls the selector 17 a. In the embodiment of FIG. 2, when the selection signal S _SEL is logically 1, it indicates that the signal recognizer 12 considers the dimming signal S _{DIM to} be a PWM signal; on the contrary, when the signal recognizer 12 considers the dimming signal S _DIM In the case of a DC signal, the selector 17a sets the selection signal S _SEL to a logical 0.

In one embodiment, the signal identifier 12 determines the selection signal S _SEL according to the signal edge of the dimming signal S _DIM . Please refer to FIG. 4, which shows that the dimming signal S _DIM has two falling edges FA1 and FA2, and one rising edge RA1. The signal identifier 12 can generate the selection signal according to whether there are enough falling edges and rising edges within a predetermined time, and the absolute value of the slope is greater than a predetermined value. For example, if the signal recognizer 12 finds that there are more than 4 falling edges and rising edges in 8ms, and the absolute value of the slope is greater than 0.1V/us, then it is considered that the dimming signal S _DIM is a PWM signal, The selection signal S _SEL is logically 1. On the contrary, if there are no more than 4 falling edges and rising edges whose absolute value of slope is greater than 0.1V/us in 8ms, then the dimming signal S _DIM is regarded as 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 S _DIM low to cross the reference voltage V _REF-H as the start of the falling edge FA1. Then, the dimming signal S _DIM after the predetermined delay T _DELAY and the reference voltage V _REF-L are compared 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 . Similarly, the signal recognizer 12 regards the dimming signal S _DIM high to cross the reference voltage V _REF-L as the start of the falling edge RA1. Then, the dimming signal S _DIM after the predetermined delay T _DELAY and the reference voltage V _{REF-H are} compared 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 dimming signal S _DIM changes from the reference voltage V _REF-H to the reference voltage V _REF-L during the falling time greater than a predetermined delay T _DELAY Whether it is 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 according to whether the rise time of the dimming signal S _DIM from the reference voltage V _REF-L to the reference voltage V _REF-H is greater than a predetermined delay T _DELAY It is sufficient to represent the rising and falling edges of a PWM signal.

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

The selection signal S _SEL shown in FIG. 2 only controls the selector 17a, but the present invention is not limited to this. For example, in one embodiment, when the signal recognizer 12 considers the dimming signal S _{DIM to} be a PWM signal, the signal recognizer 12 turns off the DC-to-PWM converter 16 entirely through the selection signal S _SEL to save Electrical energy. Similarly, when the signal recognizer 12 considers the dimming signal S _{DIM to} be a DC signal, the digital buffer 18 can also be selectively turned off to save unnecessary power consumption.

The LED driver 14a controls the power transistor MNDRV according to the output of the multiplexer 26, thereby controlling the current flowing through the light emitting element LT. When the output of the multiplexer 26 is logically 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 element LT is approximately 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 logically zero, the voltage level converter 28 outputs 0V, so that the current of the light emitting element LT is approximately zero.

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 S _DIM . If there is a variable resistor RDIM between the dimming input terminal DIM and the ground line GND, a constant current I _SET can flow through the variable resistor RDIM to generate a DC voltage at the dimming input terminal DIM as the dimming signal S _DIM . When the DC signal V _DC or the PWM signal S _DIM-PWM is directly provided by the outside world as the dimming signal S _DIM , the constant current I _SET does not substantially affect the DC signal V _DC or the PWM signal S _DIM-PWM .

FIG. 5 shows an example of the dimming method 60a used by the dimming controller 10a of FIG.

In step 62, the dimming controller 10a receives the dimming signal S _DIM through the dimming input terminal _DIM , which may be a PWM signal or a DC signal.

Step 64 follows step 62. Identification signal recognizer 12 positioned on the modulation dimming input DIM _DIM optical signal S DC is PWM, a selection signal is generated according to S _SEL, which controls the selector 17a.

Step 68a continues after the signal recognizer 12 considers the dimming signal S _{DIM to} be a DC signal. The DC-to-PWM converter 16 converts the dimming signal S _DIM to provide a corresponding PWM signal S _PWM .

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

Step 72a continues after the signal recognizer 12 considers the dimming signal S _{DIM to} be a PWM signal. The selector 17a selects the dimming signal S _DIM and transmits it to the LED driver 14a through the digital buffer 18 and the multiplexer 26 for driving the light emitting element LT. At this time, the selector 17a does not pass the PWM signal _SPWM to the LED driver 14a.

The dimming controller 10a of FIG. 2 and the dimming method 60a of FIG. 5 have the following advantages. When the dimming signal S _DIM is a DC signal, a corresponding PWM signal S _PWM can be generated to the LED driver 14a for driving the light emitting element LT. When the dimming signal S _DIM is a PWM signal, the dimming signal S _{DIM is} directly sent to the LED driver 14a, which can faithfully and accurately reflect the dimming state that is really needed. In other words, regardless of whether the dimming signal S _DIM 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. In an embodiment, it can be used as the dimming controller 10 in FIG. The dimming controller 10b includes a signal identifier 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 exposed in Fig. 2, the operation of which can be known from the previous explanations in Fig. 2. Tell me again.

The PWM-to-DC converter 19 is a type 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 S _DIM and supplies it to the resistor R1. The resistor R1 and the capacitor C1 form a low-pass filter, which can generate a DC signal S _DC , which approximately represents the duty cycle of the dimming signal S _DIM .

The selector 17b in FIG. 6 is controlled by the signal recognizer 12 and has two inputs, respectively receiving a DC signal S _DC and a dimming signal S _DIM . The selector 17b includes an operational amplifier 24 and a multiplexer 26. When the signal recognizer 12 considers the dimming signal S _{DIM to} be a DC signal, the operational amplifier 24 acts as a unity gain buffer to transfer the dimming signal S _DIM to the multiplexer 26, which in turn transfers the dimming signal S _DIM to the LED Drive 14b. When the signal recognizer 12 considers the dimming signal S _{DIM 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 S _DIM , it is the DC signal S _DC representing the PWM dimming signal S _DIM .

The LED driver 14b controls the power transistor MNDRV according to the output of the multiplexer 26, thereby controlling 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 the dimming method 60b used in the dimming controller 10b of FIG. Some steps of the dimming method 60b are the same as or similar to the dimming method 60a, which can be known from the description of the previous dimming method 60a or the dimming controller 10a, and will not be repeated here.

Step 72b continues after the signal recognizer 12 considers the dimming signal S _{DIM to} be a DC signal. The selector 17b transmits the dimming signal S _DIM to the LED driver 14b, which drives the light emitting element LT accordingly.

Step 68b continues after the signal recognizer 12 considers the dimming signal S _{DIM to} be a PWM signal. The PWM-to-DC converter 19 converts the dimming signal S _DIM 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 between the dimming signal S _DIM through the operational amplifier 24 and the LED driver 14b is interrupted.

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

The dimming controller 10b of FIG. 6 and the dimming method 60b of FIG. 7 have the following advantages. When the dimming signal S _DIM is a DC signal, it can be directly transmitted to the LED driver 14b approximately faithfully for driving the light emitting element LT. When the dimming signal S _DIM 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 S _DIM is DC or PWM, the dimming controller 10b can provide an appropriate DC signal to the LED driver 14b.

The invention is not limited to driving only LEDs, in other embodiments, it can also drive Move other light-emitting devices.

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 identifier 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 exposed in Fig. 2 and Fig. 6, the operation of which can be known from the related explanations of Fig. 2 and Fig. 6, and will not be repeated here.

The PWM-to-DC converter 19 is a type 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 S _DIM to generate the temporary PWM signal SB _PWM and supplies it 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 , which approximately represents the duty cycle of the dimming signal S _DIM .

The duty cycle of the temporary PWM signal SB _PWM will be the same as the duty cycle of the dimming signal S _DIM , but the logic level of the logic "1" of the temporary PWM signal SB _PWM may not necessarily be the same as the logic level of the dimming signal S _DIM The logic level of 1" is the same. For example, when the dimming signal S _DIM is logic "0", the logic level is 0V; when the dimming signal S _DIM is logic "1", the 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 preset 5V. Therefore, the digital buffer 18 can also be regarded as a level shifter, _regardless of the logic level of the logic "1" of the dimming signal S _DIM , the temporary PWM signal SB _{PWM can} have a preset logic level Bit.

The selector 17b in FIG. 8 is controlled by the signal recognizer 12 and has two inputs, respectively receiving the DC signal S _DC and the dimming signal S _DIM . The selector 17b includes an operational amplifier 24 and a multiplexer 26. When the signal recognizer 12 considers the dimming signal S _{DIM to} be a DC signal, the operational amplifier 24 acts as a unity gain buffer and transfers the dimming signal S _DIM 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 S _{DIM 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 (DC signal SD _DC ) is not the DC dimming signal S _DIM , it is the DC signal S _DC representing the PWM dimming signal S _DIM .

The selector 17b is equivalently connected to the dimming input terminal DIM through different DC 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 located on the PWM signal path PTH _PWM . When the signal recognizer 12 considers the dimming signal S _{DIM to} be DC, the signal recognizer 12 causes the selector 17b to 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 S _{DIM to} be PWM, the signal recognizer 12 causes the selector 17b to 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 16a includes a signal generator 20 and a comparator 22. The signal generator 20 generates a sawtooth wave S _SAW and provides it to the inverting input 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 fixed value, which has nothing to do with the original dimming signal S _DIM . In addition, the logic level of the PWM signal SC _PWM , whether it is a logical "0" or "1", can be appropriately customized for the LED driver 14a.

The LED driver 14a in FIG. 8 manufactures a power transistor MNDRV based on the PWM signal SC _{PWM to} control the current flowing through the light emitting element LT.

FIG. 9 shows an example of the dimming method 60c used in the dimming controller 10c of FIG. 8. There are some steps in the dimming method 60c that are the same as or similar to 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 continues after the signal recognizer 12 considers the dimming signal S _{DIM to} be a DC signal. The selector 17b selects the DC signal path PTH _DC and passes the dimming signal S _DIM as the DC signal SD _DC .

Step 67 continues after the signal recognizer 12 considers the dimming signal S _{DIM to} be PWM. The digital buffer 18 reproduces the logic value of the dimming signal S _DIM to generate a temporary PWM signal SB _PWM with a preset logic level.

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

In FIG. 9, after step 70c continues after step 68b, 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 14a manufactures a power transistor MNDRV according to the PWM signal SC _{PWM 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 S _DIM 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 used to select one of two signals with the same type. The multiplexer 26 in the dimming controller 10a outputs one of two PWM signals. The multiplexer 26 in the dimming controllers 10b and 10c outputs one of two DC signals. However, the present invention is not limited to this. In some embodiments, the multiplexer 26 may output one of two different types of signals.

FIG. 10 shows a dimming controller 10d. In one embodiment, it can be used as the dimming controller 10 in FIG. In the dimming controller 10d and the dimming controller 10c, the same and similar devices have been disclosed in FIG. 8 and the corresponding description, and their operation can be known through the related explanations in FIG. 8 and FIG. 9, and no longer Exhaustively. 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 10c is connected between the multiplexer 26 and the digital buffer 18. Unlike 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 both the dimming signal S _DIM 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 transmitted to the low-pass filter 15, which generates the DC signal SD _DC .

When the signal recognizer 12 considers the dimming signal S _{DIM to} be DC, the selector 17b 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 S _DIM , and can faithfully generate a DC signal SD having the same voltage level as the dimming signal S _{DIM DC} .

When the signal recognizer 12 considers the dimming signal S _{DIM to} be PWM, the selector 17b 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, _regardless of the logic level of the logic "1" of the dimming signal S _DIM , the temporary PWM signal SB _{PWM can} have a preset logic level Bit. 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 the dimming method 60d used in the dimming controller 10d of FIG. There are some steps in the dimming method 60d that are the same as or similar to 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 is continued after step 67, and the selector 17b selects the temporary PWM signal SB _PWM as the output SD _XX .

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

The above are only the preferred embodiments of the present invention, and all changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the present invention.

10c‧‧‧ dimming controller

12‧‧‧Sign Recognizer

14a‧‧‧LED driver

15‧‧‧Low-pass filter

16a‧‧‧DC to PWM converter

17b‧‧‧selector

18‧‧‧Digital buffer

19‧‧‧PWM to DC converter

20‧‧‧Signal generator

22‧‧‧Comparator

24‧‧‧Operational amplifier

26‧‧‧Multiplexer

31‧‧‧Constant current source

C1‧‧‧Capacitance

CS‧‧‧current detection terminal

DIM‧‧‧Dimming input

DRV‧‧‧Drive

I _SET ‧‧‧ Constant current

PTH _DC ‧‧‧DC signal path

PTH _PWM ‧‧‧PWM signal path

R1‧‧‧Resistance

SB _PWM ‧‧‧Temporary PWM signal

S _DC ‧‧‧DC signal

S _DIM ‧‧‧ dimming signal

S _DRV ‧‧‧ drive signal

SD _DC ‧‧‧DC signal

SC _PWM ‧‧‧PWM signal

S _SAW ‧‧‧Sawtooth wave

S _SEL ‧‧‧selection signal

V _CS ‧‧‧ Current detection signal

Claims (8)

A dimming controller suitable for dimming a light-emitting element, including: a dimming input terminal, which can receive a dimming signal, which can be DC or PWM; a signal identifier, connected to the dimming The input terminal is used to identify whether the dimming signal on the dimming input terminal is DC or PWM; a selector can be connected to the dimming input terminal through a different DC signal path and a PWM signal path. The selector is controlled by the signal recognizer; a direct current PWM converter, coupled to the selector, is used to convert the direct current signal into a PWM signal for dimming the light emitting element; and a PWM converter The DC converter is connected between one output of the selector and the DC-to-PWM converter, and generates the DC signal according to the dimming signal; wherein, when the signal recognizer considers the dimming signal to be DC, the The signal identifier causes the selector to select the DC signal path to connect the dimming input to the PWM-to-DC converter; and when the signal identifier considers the dimming signal to be PWM, the signal identifier enables the selection The controller selects the PWM signal path to connect the dimming input to the PWM-to-DC converter. For example, the dimming controller of the first patent application scope includes: a digital buffer located on the PWM signal path for generating a temporary PWM signal according to the dimming signal, which has a specific logic criterion Bit, the temporary PWM signal is input as one of the selectors. If the dimming controller of item 1 of the patent application scope, the selector includes: A unity gain buffer is used to transfer the dimming signal to the DC-to-PWM converter when the dimming signal is DC. As for the dimming controller of claim 1, the DC-to-PWM converter includes: a signal generator for generating a periodic signal; and a comparator for comparing the periodic signal and the DC signal To generate the PWM signal. A dimming method suitable for dimming a light-emitting element, including: 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, select the DC signal path to make the dimming signal pass a PWM to DC converter to generate a DC signal; when the dimming signal is PWM, select the The PWM signal path allows the dimming signal to pass through the PWM-to-DC converter to generate the DC signal; and converts the DC signal to generate a PWM signal for dimming the light-emitting element. For example, the dimming method of claim 5 of the patent scope includes: when the dimming signal is PWM, a temporary PWM signal is generated according to the dimming signal, which has a predetermined logic level; and converting the Temporary PWM signal to provide the DC signal. For example, the dimming method of claim 6, wherein the step of converting the temporary PWM signal includes: performing low-pass filtering on the temporary PWM signal to provide the DC signal. For example, the dimming method in item 5 of the patent application scope includes: A unity gain buffer is provided on the DC signal path. When the dimming signal is DC, it is used to provide the DC signal according to the dimming signal.

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