TWI727868B - Dimming device and dimming system - Google Patents

Abstract

A dimming system includes N light-emitting units connected in series, a pulse wave generating circuit, a logic control circuit, and a hysteresis comparison circuit. The first light-emitting unit receives an output current with an original pulse wave width, and the pulse wave generates The circuit is electrically connected to the light-emitting units and outputs N pulse signals, the logic control circuit is electrically connected to the pulse wave generating circuit, and the hysteresis comparison circuit is electrically connected to the logic control circuit and the light-emitting units. When at least one of the pulse waves is The voltage level of the signal is logic 1, and the hysteresis comparison circuit is controlled to provide the output current to the light-emitting units. When the voltage levels of the pulse signals are all logic 0, the hysteresis comparison circuit is controlled to not provide the output Electric current flows to the light-emitting units.

Description

Dimming device and dimming system

The invention relates to a control device and a control system, in particular to a dimming device and a dimming system for controlling the brightness of a light-emitting diode.

Refer to Figure 1, which shows the existing Shunt Dimming system. The dimming circuit drives multiple light-emitting diodes to emit light with a hysteresis power supply (SMPS: Switch Mode Power Supply). The power supply mechanism is as follows: Referring to FIG. 2, when the induced current I _{L of the} inductor 101 is greater than a first reference voltage REF1, _{the voltage level of the output signal V g} of the hysteresis comparator 102 is switched to logic 0. When the induced current I _{L of the} inductor 101 is less than a first reference voltage REF1, When the reference voltage REF2 is two, the voltage level of the output signal V _g of the hysteresis comparator 102 is switched to logic 1, thereby _{controlling the induced current IL of the} inductor 101 between the first reference voltage REF1 and the second reference voltage REF2 , So that the overall average current value is the average value of the first reference voltage REF1 and the second reference voltage REF2, and then a plurality of switches M ₁ ~M _N are controlled to be turned on/off from the outside according to actual requirements. The control signals PWM ₁ ~PWM _N control multiple light-emitting diodes LED ₁ ~ LED _{N to} present corresponding dimming.

With reference to Figure 3, generally speaking, the induced current I _L is not a stable value. Its waveform is a ripple that varies with the switching frequency. When high brightness is required, the control signals PWM ₁ ~PWM _N The duty cycle is greater than _{the multiple cycles of the induced current I L.} Therefore, although the cycles of the externally provided control signals PWM ₁ ~PWM _N are different from the induced current I _L cycle, that is, the opening time of the _{switches M 1} ~M _{N is different from that of the induced current I L.} The switching frequency of the hysteresis power supply is asynchronous, but the difference has very little effect on the overall average current, that is _{, the average difference of the induced current I L} corresponding to each cycle of the control signal is very small, which is very small for the human brain. As far as the visual effect is concerned, it is not easy to detect the flickering of the light-emitting diode due to the different receiving current.

When the required brightness becomes lower, the duty cycle of the dimming signal becomes smaller (for example, close to 0%). Because the duty cycle of the control signal PWM ₁ ~ PWM _N (PWM ₁ and PWM _{2 are used} for example) is shorter than the induction A cycle of the current I _{L is shown in the two periods of △t 1} and △t ₂ as shown in Figure 3. At this time, the proportion of the non-synchronized difference rises sharply, that is, in the two periods, PWM ₁ and PWM ₂ correspond to The average value of the induced current I _L is different, which will make the output current I _{LED1 received by the light-emitting diode LED1 in the two periods of △t 1} and △t ₂ , or the light-emitting diode LED2 at △t ₁ , △t _{2 The output current I LED2} received during the two periods of time is different, which causes the brightness to change, and the human brain visually feels the effect of the light-emitting diode flickering due to the different received current. Therefore, the existing dimming system needs to be improved. .

Therefore, an object of the present invention is to provide a dimming device that can improve the shortcomings of the prior art.

Therefore, the dimming device of the present invention is suitable for generating an output current to N light-emitting units connected in series, and each light-emitting unit is controlled to switch to one of a light-emitting state and a non-light-emitting state. N≧2, the dimming device It includes a pulse wave generating circuit, a logic control circuit, and a hysteresis comparison circuit.

The pulse wave generating circuit is electrically connected to the light-emitting units and outputs N pulse wave signals, each of which has a pulse wave width. The pulse wave generating circuit controls each of the light-emitting units according to the pulse wave signals. Switch to one of the light-emitting state and the non-light-emitting state.

The logic control circuit is electrically connected to the pulse wave generating circuit, and generates corresponding output signals according to changes in the amplitude of the pulse wave signals.

The hysteresis comparison circuit is electrically connected to the logic control circuit and the light-emitting units. The hysteresis comparison circuit generates a corresponding induced current according to the change of the output signal of the logic control circuit, and generates the output current according to the induced current in a controlled manner. The light-emitting units and the hysteresis comparison circuit output one of a first logic signal and a second logic signal to the logic control circuit according to the change of the induced current. .

When at least one of the voltage levels of the pulse signals is logic 1, and the hysteresis comparison circuit outputs the first logic signal, the logic control circuit controls the hysteresis comparison The circuit provides the output current to the light-emitting units, and one of the corresponding light-emitting units switches to the light-emitting state.

When the voltage levels of the pulse signals are all logic 0, the logic control circuit controls the hysteresis comparison circuit not to provide the output current to the light-emitting units, and the light-emitting units switch to the non-light-emitting state.

Moreover, another object of the present invention is to provide a dimming system that can improve at least one of the disadvantages of the prior art.

Therefore, the dimming system of the present invention includes N light-emitting units connected in series, a pulse wave generating circuit, a logic control circuit, and a hysteresis comparison circuit.

The first light-emitting unit among the N light-emitting units receives an output current, and each light-emitting unit is controlled to switch to one of a light-emitting state and a non-light-emitting state, N≧2.

The pulse wave generating circuit is electrically connected to the light-emitting units and outputs N pulse wave signals, each of which has a pulse wave width. The pulse wave generating circuit controls each of the light-emitting units according to the pulse wave signals. Switch to one of the light-emitting state and the non-light-emitting state.

The logic control circuit is electrically connected to the pulse wave generating circuit, and generates corresponding output signals according to changes in the amplitude of the pulse wave signals.

The hysteresis comparison circuit is electrically connected to the logic control circuit and the light-emitting units, and the hysteresis comparison circuit generates an output signal according to the change in the output signal of the logic control circuit. Corresponds to the induced current, and generates the output current to the light-emitting units according to the induced current in a controlled manner, and the hysteresis comparison circuit outputs a first logic signal and a second logic signal according to the change of the induced current. One to the logic control circuit.

When at least one of the voltage levels of the pulse signals is logic 1, and the hysteresis comparison circuit outputs the first logic signal, the logic control circuit controls the hysteresis comparison circuit to provide the output current to the light-emitting units, and A corresponding light-emitting unit is switched to the light-emitting state.

When the voltage levels of the pulse signals are all logic 0, the logic control circuit controls the hysteresis comparison circuit not to provide the output current to the light-emitting units, and the light-emitting units switch to the non-light-emitting state.

The effect of the present invention is that the logic control circuit controls the output current of the hysteresis comparison circuit according to the voltage levels of the pulse signals, and when the voltage levels of the pulse signals are all logic 0, the hysteresis The comparison circuit does not output the output current to the light-emitting units. When at least one of the voltage levels of the pulse wave signals is logic 1, the hysteresis comparison circuit synchronously outputs the output current to the light-emitting units so that the The average value of the output current received by the light-emitting unit in the on state is the same without changing the brightness.

101: Inductance

REF1: the first reference voltage

REF2: second reference voltage

M ₁ ~M _N : switch

LED ₁ ~LED _N : Light-emitting diode

I _L : induced current

I _LED : output current

2: Light-emitting unit

21: Load switch

22: luminous parts

3: Pulse wave generating circuit

31: Microcontroller

32: reverser

4: Logic control circuit

41: The first logic gate

42: The second logic gate

5: Hysteresis comparison circuit

51: Control switch

52: Inductance

53: Diode

54: Voltage source

55: Hysteresis comparator

The other features and effects of the present invention will be described with reference to the drawings. Figure 1 is a circuit diagram illustrating the existing dimming system; Figure 2 is a timing diagram illustrating the corresponding relationship between the output current of an inductor of the dimming system and the output signal of a hysteresis comparator; Fig. 3 is a timing diagram illustrating the corresponding relationship between the output current of the inductor and the output current of the driving light-emitting diode of the dimming system, and the pulse wave signal; Fig. 4 is a circuit diagram illustrating the dimming system of the present invention An embodiment; and FIG. 5 is a timing diagram illustrating the corresponding relationship between the output current of an inductor, the pulse signal, the output signal of a logic control circuit 4, and the output current of driving the light-emitting diodes of this embodiment.

Referring to FIG. 4, an embodiment of the dimming system of the present invention includes N light-emitting units 2 connected in series, a pulse generation circuit 3, a logic control circuit 4, and a hysteresis comparison circuit 5.

The first of the N light-emitting units 2 receives an output current I _LED , and each light-emitting unit 2 is controlled to switch to one of a light-emitting state and a non-light-emitting state, N≧2, the light-emitting units 2 Each light-emitting element 22 includes a load switch 21 and a light-emitting element 22, and each light-emitting element 22 is connected in parallel with each load switch 21.

The pulse wave generating circuit 3 is electrically connected to the light-emitting units 2 and outputs N pulse wave signals. Each pulse wave signal has a pulse wave width. The pulse wave generating circuit 3 controls the pulse wave signals respectively according to the pulse wave signals. The light-emitting unit 2 is switched to one of the light-emitting state and the non-light-emitting state. The pulse wave generating circuit 3 includes a microcontroller 31 and N inverters 32. The microcontroller 31 generates the N pulse wave signals. Each inverter 32 has a receiving terminal for receiving each pulse signal, and an output terminal electrically connected to one of the light-emitting units 2, more specifically, the output terminal of each inverter 32 is connected to Each load switch 21 is electrically connected, and each inverter 32 performs a logical transition of the received pulse signal and outputs it from the output terminal to the corresponding load switch 21. It should be added that the aforementioned light-emitting The switching of unit 2 to the light-emitting state means that when the receiving end of one of the inverters 32 receives a pulse signal with a voltage level of logic 1, its output end outputs a pulse signal of logic 0, so the corresponding load of the light-emitting unit 2 The switch 21 receives the pulse signal of logic 0 and does not turn on, and the light emitting element 22 of the light emitting unit 2 receives the output current I _LED from the hysteresis comparison circuit 5 and turns on and emits light. The non-light emitting state is received by the inverter 32 When the terminal receives a pulse signal whose voltage level is logic 0, its output terminal outputs a pulse signal of logic 1, so the load switch 21 of the corresponding light-emitting unit 2 receives the pulse signal of logic 1 and is turned on, and the light-emitting unit 2 The light emitting element 22 does not receive the output current I _LED from the hysteresis comparison circuit 5 and does not turn on. A more detailed light emitting mechanism of the light emitting units 2 will be described later.

The logic control circuit 4 is electrically connected to the pulse wave generating circuit 3, and generates corresponding output signals according to the amplitude changes of the pulse wave signals. Specifically, the logic control circuit 4 includes a first logic gate 41 and a The second logic gate 42. The first logic gate 41 is an OR gate, which has N receiving terminals for receiving the pulse signals, and an output terminal. The second logic gate 42 is an AND gate, which has A first receiving terminal electrically connected to the output terminal of the first logic gate 41, a second receiving terminal electrically connected to the hysteresis comparison circuit 5 to receive one of the first logic signal and the second logic signal, and an electrical Connected to the output terminal of the hysteresis comparison circuit 5, the hysteresis comparison circuit 5 generates a corresponding induced current I _L according to the change of the output signal of the logic control circuit 4, and generates the output current I _LED according to the induced current I _L to the Wait for the light-emitting unit 2 and the hysteresis comparison circuit 5 outputs one of a first logic signal and a second logic signal to the logic control circuit 4 _{according to the change of the induced current IL.}

In addition, the hysteresis comparison circuit 5 also outputs one of a first logic signal and a second logic signal to the logic control circuit 4 _{according to the change of the induced current IL. In more detail, the first logic signal} The voltage level of the second logic signal is logic 1, and the voltage level of the second logic signal is logic 0. In this embodiment, the hysteresis comparison circuit 5 is a hysteresis step-down DC-DC converter, which includes a control switch 51, a Inductor 52, a diode 53, a voltage source 54, and a hysteresis comparator 55. The control switch 51 has a control terminal electrically connected to the output terminal of the second logic gate 42 and a second terminal electrically connected to the inductor 52. One end, and a second end electrically connected to the voltage source 54, the control switch 51 operates in a conducting state and a non-conducting state according to the output signal of the output end of the second logic gate 42 received by its control end One, the inductor 52 has a first end electrically connected to the first end of the control switch 51, and a second end electrically connected to the first one of the N light-emitting units 2, and the inductor 52 is used according to the The operating state of the switch 51 is controlled to generate the induced current I _L , and then the output current I _{LED is provided} to the light-emitting units 2, the diode 53 has a cathode terminal electrically connected to the first terminal of the inductor 52, and An anode terminal electrically connected to the Nth light-emitting unit 2, the voltage source 54 has an anode terminal electrically connected to the second terminal of the control switch 51, and a cathode terminal electrically connected to the anode terminal of the diode 53 , The hysteresis comparator 55 is electrically connected to the second receiving end of the second logic gate 42 and the inductor 52, and outputs the first logic signal and the second logic signal _{according to the induced current IL of the inductor 52} One of them (that is, the logic change of the signal 55_OUT in FIG. 5) goes to the second receiving end of the second logic gate 42.

When at least one of the voltage levels of the pulse signals is logic 1, and the hysteresis comparison circuit 5 outputs the first logic signal whose voltage level is logic 1, at this time, the first logic gate 41 is from its output terminal The output signal of logic 1 is output (corresponding to the timing change of 41_OUT in FIG. 5), the first receiving end of the second logic gate 42 receives the output signal, and the second receiving end of the second logic gate 42 receives the first Logic signal, and the second logic gate 42 outputs the output signal of logic 1 from its output terminal (corresponding to the timing change of 42_OUT in FIG. 5), the logic control circuit 4 controls the hysteresis comparator circuit 5 to provide the output current to the light emitting Unit 2, one of the corresponding light-emitting units 2 is switched to the light-emitting state, that is, the control switch 51 operates in the conductive state, the corresponding load switch 21 is switched to non-conductive, and the induced current _{IL of} the inductor 52 flows to the corresponding light-emitting state. Component 22 to form the output current I _LED ; when the voltage levels of the pulse signals are all logic 0, the logic control circuit controls the hysteresis comparison circuit not to provide the output current to the light-emitting units, and the light-emitting units Switching to the non-luminous state, the load switches 21 are switched to the conducting state according to the signals output by the inverters 32 of the pulse generating circuit 3, and the first logic gate 41 outputs a logic 0 output signal from its output terminal, The first receiving terminal of the second logic gate 42 receives the output terminal of the first logic gate 41 to receive the output signal, and the second logic gate 42 outputs a logic 0 output signal from its output terminal, the control switch 51 According to the output signal of the output terminal of the second logic gate 42 to operate in the non-conducting state, the induced current I _{L of} the inductor 52 flows to the diode 53 through the load switches 21, so no output current I _LED flows through the Wait for the light-emitting unit 2.

To further explain _{the corresponding relationship between the induced current IL of} the inductor 52 and the voltage of the voltage source 54 when the control switch 51 is on/off, when the control switch 51 is on, the voltage source 54 charges the inductor 52, The corresponding relationship between the induced current I _{L of} the inductor 52 and the voltage change of the voltage source 54 is I _L =(V _IN -V _OUT )/L, where L is the inductance value of _{the inductor 52, and V IN is} the value received by the inductor 52 Input voltage, V _{OUT is} the output voltage of the inductor 52; when the control switch 51 is not turned on, the inductor 52 starts to discharge, _{and the corresponding relationship between the induced current I L of} the inductor 52 and the voltage change of the voltage source 54 is I _L = -(V _OUT -0.7)/L, where 0.7 is the voltage drop of the diode 53.

Refer to FIG. 5 in conjunction with FIG. 4, and then explain the _{mechanism of generating the induced current I L} and the output current I _LED in this embodiment: the hysteresis comparator 55 samples the current generated by the inductor 52, and in the period of _{Δt 1} , When at least one of the voltage levels of the pulse signals is logic 1 (in this embodiment, the pulse signals PWM1 and PWM2 corresponding to the first light-emitting element 22 and the second light-emitting element 22 are taken as an example) When the control switch 51 is turned on and the hysteresis comparator 55 outputs the first logic signal, the second logic gate 42 outputs a logic 1 output signal from its output terminal. The control switch 51 is continuously turned on, and the inductor 52 senses The current I _L increases. At this time, the first load switch 21 corresponding to the first light-emitting element 22 and the second load switch 21 corresponding to the second light-emitting element 22 are both non-conducting, and the remaining load switches 21 Therefore, the output current I _LED flows to the first light-emitting element 22 and the second light-emitting element 22 to form currents I _LED1 and I _LED2 . When the pulse signal PWM1 corresponding to the first light-emitting element 22 is switched to logic 0, Then the current I _LED1 correspondingly changes to zero. At this time, because the first logic gate 41 continues to output a logic 1 signal, and the hysteresis comparator 55 outputs the first logic signal _{according to the induced current I L, the second logic gate} 42 outputs a logic 1 output signal from its output terminal to control the control switch 51 to turn on. When the induced current _{IL is} greater than a first reference voltage REF1, the hysteresis comparator 55 outputs the second logic signal. At this time, the The second logic gate 42 outputs a logic 0 output signal from its output terminal to control the control switch 51 to be non-conductive, so the induced current _IL begins to decrease, and the current I _LED2 flowing to the second light emitting element 22 decreases accordingly. Until the induced current _{IL is} lower than a second reference voltage RREF2 that is less than the first reference voltage REF1, the hysteresis comparator 55 outputs the first logic signal. At this time, the second logic gate 42 is based on the first logic Signal, and the pulse signal PWM2 outputs a logic 1 output signal from its output terminal to control the control switch 51 to turn on, so the induced current _IL starts to increase, and the current I _LED2 flowing to the second light emitting element 22 follows it. Increment, and then when the pulse signal PWM2 switches to logic 0, the first logic gate 41 outputs a logic 0 signal, so the second logic gate 42 outputs a logic 0 output signal from its output terminal to control the control switch 51 No conduction, at this time the induced current I _L begins to drop to zero, the current I _LED2 correspondingly changes to zero, and the hysteresis comparator 55 continues to output the first logic signal until the Δt ₂ period, the first logic gate 41 When the pulse signals PWM1 and PWM2 are received again, the induced current I _{L is} again generated in a controlled manner, and the currents I _LED1 and I _{LED2 are} re-provided to the corresponding light-emitting elements 22. The operation principle is the same as the above and will not be repeated. It is mentioned that in this embodiment When the pulse signals received by the first logic gate 41 are all logic 0, the second logic gate 42 is forced to output a logic 0 output signal, so that the induced current I _L decreases to zero. When the gate 41 receives the pulse signal of logic 1 again, the induced current I _L is generated synchronously with the pulse signal. Therefore, in each period when the pulse signal is logic 1, the average value of the _{corresponding output current I LED can be made} All the same.

In summary, the logic control circuit 4 forces the pulse signal of logic 1 to be _{output synchronously with the induced current IL of} the inductor 52. Therefore, the pulse signal of each logic 1 corresponds to the output current I during the conduction period. _{The average value of the LEDs} are all the same, that is to say, the current I _LED flowing through the light-emitting diode is fixed, and there will be no brightness change, so that the human brain can visually feel the brightness of the light-emitting diode and does not flicker. Therefore, it can indeed achieve the purpose of the invention.

However, the above are only examples of the present invention. When the scope of implementation of the present invention cannot be limited by this, all simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the content of the patent specification still belong to Within the scope covered by the patent of the present invention.

2: Light-emitting unit

21: Load switch

22: luminous parts

3: Pulse wave generating circuit

31: Microcontroller

32: reverser

4: Logic control circuit

41: The first logic gate

42: The second logic gate

5: Hysteresis comparison circuit

51: Control switch

52: Inductance

53: Diode

54: Voltage source

55: Hysteresis comparator

Claims (10)

A dimming device suitable for generating an output current to N light-emitting units connected in series, each light-emitting unit is controlled to switch to one of a light-emitting state and a non-light-emitting state, N≧2, the dimming device includes: A pulse wave generating circuit is electrically connected to the light-emitting units and outputs N pulse wave signals. Each pulse wave signal has an on-pulse width. The pulse wave generating circuit controls the light-emitting units respectively according to the pulse wave signals. Each unit is switched to one of the light-emitting state and the non-light-emitting state; A logic control circuit, electrically connected to the pulse wave generating circuit, and generating corresponding output signals according to changes in the amplitude of the pulse wave signals; A hysteresis comparison circuit electrically connected to the logic control circuit and the light-emitting units, the hysteresis comparison circuit generates a corresponding induced current according to the change of the output signal of the logic control circuit, and generates the output current according to the induced current in a controlled manner To the light-emitting units, and the hysteresis comparison circuit outputs a first logic signal and one of a second logic signal to the logic control circuit according to the change of the induced current, When at least one of the voltage levels of the pulse signals is logic 1, and the hysteresis comparison circuit outputs the first logic signal, the logic control circuit controls the hysteresis comparison circuit to provide the output current to the light-emitting units, and A corresponding light-emitting unit is switched to the light-emitting state, When the voltage levels of the pulse signals are all logic 0, the logic control circuit controls the hysteresis comparison circuit not to provide the output current to the light-emitting units, and the light-emitting units switch to the non-light-emitting state. The dimming device according to claim 1, wherein the logic control circuit includes a first logic gate and a second logic gate, The first logic gate has N receiving terminals for receiving the pulse wave signals respectively, and an output terminal, The second logic gate has a first receiving terminal electrically connected to the output terminal of the first logic gate, and a second receiving terminal electrically connected to the hysteresis comparison circuit to receive one of the first logic signal and the second logic signal , And an output terminal electrically connected to the hysteresis comparison circuit, When the voltage level of at least one of the pulse signals is logic 1, and the hysteresis comparison circuit outputs the first logic signal, the first logic gate outputs a logic 1 output signal from its output terminal, and the second logic The first receiving terminal of the gate receives the output terminal of the first logic gate and the output terminal receives the output signal, the second receiving terminal of the second logic gate receives the first logic signal, and the second logic gate is from its output terminal The output signal of logic 1 is output, and the hysteresis comparison circuit provides the output current to the light-emitting units according to the output signal of the output terminal of the second logic gate. The dimming device according to claim 2, wherein the hysteresis comparison circuit includes a control switch, an inductor, a diode, a voltage source, and a hysteresis comparator, The control switch has a control terminal electrically connected to the output terminal of the second logic gate, a first terminal electrically connected to the inductor, and a second terminal electrically connected to the voltage source. The output signal of the output terminal of the second logic gate operates in one of a conducting state and a non-conducting state, The inductor has a first end electrically connected to the first end of the control switch, and a second end electrically connected to the first one of the N light-emitting units. The inductor is used to change the control switch according to the operating state of the control switch. Generate the induced current and provide the output current to the light-emitting units, The diode has a cathode terminal electrically connected to the first terminal of the inductor, and an anode terminal electrically connected to the Nth light-emitting unit, The voltage source has an anode terminal electrically connected to the second terminal of the control switch, and a cathode terminal electrically connected to the anode terminal of the diode, The hysteresis comparator is electrically connected to the second receiving end of the second logic gate and the inductor, and outputs the first logic signal and one of the second logic signals to the second logic signal according to the induced current of the inductor The second receiving end of the logic gate, When at least one of the voltage levels of the pulse signals is logic 1, and the hysteresis comparator outputs the first logic signal, the control switch operates in the on state, and the inductor receives the voltage from the voltage source to generate the induction Current and provide the output current, When the voltage levels of the pulse signals are all logic 0, the control switch operates in the non-conducting state, the inductor does not receive voltage from the voltage source, does not generate the induced current, and does not provide the output current. The dimming device according to claim 3, wherein when the pulse signal voltage levels are all logic 0, the first logic gate outputs a logic 0 output signal from its output terminal, and the second logic gate The first receiving terminal receives the output terminal of the first logic gate to receive the output signal, and the second logic gate outputs an output signal of logic 0 from its output terminal, and the control switch is based on the output signal of the output terminal of the second logic gate And operate in the non-conducting state. The dimming device according to claim 1, wherein the pulse wave generating circuit includes a microcontroller and N inverters, The microcontroller generates the N pulse wave signals, Each inverter has a receiving terminal for receiving each pulse signal, and an output terminal electrically connected to one of the light-emitting units. Each inverter performs logic transitions on the received pulse signal and automatically This output is output. The dimming device according to claim 1, wherein the voltage level of the first logic signal is logic 1, and the voltage level of the second logic signal is logic 0. A dimming system, including: N light-emitting units connected in series, the first light-emitting unit receives an output current, and each light-emitting unit is controlled to switch to one of a light-emitting state and a non-light-emitting state, N≧2; A pulse wave generating circuit is electrically connected to the light-emitting units and outputs N pulse wave signals. Each pulse wave signal has an on-pulse width. The pulse wave generating circuit controls the light-emitting units respectively according to the pulse wave signals. Each unit is switched to one of the light-emitting state and the non-light-emitting state; A logic control circuit, electrically connected to the pulse wave generating circuit, and generating corresponding output signals according to changes in the amplitude of the pulse wave signals; and A hysteresis comparison circuit is electrically connected to the logic control circuit and the light-emitting units. The hysteresis comparison circuit generates a corresponding induced current according to the change of the output signal of the logic control circuit, and generates the output current to the output currents according to the induced current. A light emitting unit, and the hysteresis comparison circuit outputs one of a first logic signal and a second logic signal to the logic control circuit according to the change of the induced current, When at least one of the voltage levels of the pulse signals is logic 1, and the hysteresis comparison circuit outputs the first logic signal, the logic control circuit controls the hysteresis comparison circuit to provide the output current to the light-emitting units, and A corresponding light-emitting unit is switched to the light-emitting state, When the voltage levels of the pulse signals are all logic 0, the logic control circuit controls the hysteresis comparison circuit not to provide the output current to the light-emitting units, and the light-emitting units switch to the non-light-emitting state. The dimming system according to claim 7, wherein the logic control circuit includes a first logic gate and a second logic gate, The first logic gate has N receiving terminals for receiving the pulse wave signals respectively, and an output terminal, The second logic gate has a first receiving terminal electrically connected to the output terminal of the first logic gate, and a second receiving terminal electrically connected to the hysteresis comparison circuit to receive one of the first logic signal and the second logic signal , And an output terminal electrically connected to the hysteresis comparison circuit, When the voltage level of at least one of the pulse signals is logic 1, and the hysteresis comparison circuit outputs the first logic signal, the first logic gate outputs a logic 1 output signal from its output terminal, and the second logic The first receiving terminal of the gate receives the output terminal of the first logic gate and the output terminal receives the output signal, the second receiving terminal of the second logic gate receives the first logic signal, and the second logic gate is from its output terminal The output signal of logic 1 is output, and the hysteresis comparison circuit provides the output current to the light-emitting units according to the output signal of the output terminal of the second logic gate. The dimming system according to claim 8, wherein the hysteresis comparison circuit includes a control switch, an inductor, a diode, a voltage source, and a hysteresis comparator, The control switch has a control terminal electrically connected to the output terminal of the second logic gate, a first terminal electrically connected to the inductor, and a second terminal electrically connected to the voltage source. The output signal of the output terminal of the second logic gate operates in one of a conducting state and a non-conducting state, The inductor has a first end electrically connected to the first end of the control switch, and a second end electrically connected to the first one of the N light-emitting units. The inductor is used to change the control switch according to the operating state of the control switch. Generate the induced current and provide the output current to the light-emitting units, The diode has a cathode terminal electrically connected to the first terminal of the inductor, and an anode terminal electrically connected to the Nth light-emitting unit, The voltage source has an anode terminal electrically connected to the second terminal of the control switch, and a cathode terminal electrically connected to the anode terminal of the diode, The hysteresis comparator is electrically connected to the second receiving end of the second logic gate and the inductor, and outputs the first logic signal and one of the second logic signals to the second logic signal according to the induced current of the inductor The second receiving end of the logic gate, When at least one of the voltage levels of the pulse signals is logic 1, and the hysteresis comparator outputs the first logic signal, the control switch operates in the on state, and the inductor receives the voltage from the voltage source to generate the induction Current and provide the output current, When the voltage levels of the pulse signals are all logic 0, the control switch operates in the non-conducting state, the inductor does not receive voltage from the voltage source, does not generate the induced current, and does not provide the output current. The dimming system of claim 9, wherein when the voltage levels of the pulse signals are all logic 0, the first logic gate outputs a logic 0 output signal from its output terminal, and the second logic gate The first receiving terminal receives the output terminal of the first logic gate to receive the output signal, and the second logic gate outputs an output signal of logic 0 from its output terminal, and the control switch is based on the output signal of the output terminal of the second logic gate And operate in the non-conducting state.

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