TWI436689B - Lighting apparatus and control method thereof - Google Patents

Description

Light emitting device and control method thereof

The present invention relates to a light emitting device and a control method therefor.

The light-emitting diode is a current-driven light-emitting device, and the brightness of the light-emitting diode can be adjusted by controlling the current flowing through the light-emitting diode. Generally, the brightness of the light emitting diode is adjusted by means of continuous current dimming or pulse width modulation dimming. Compared with continuous current dimming, the use of pulse width modulation dimming has the advantages of lower dimming depth and smaller color change, and is currently widely used dimming method. However, according to different characteristics of the LED and the difference of the power supply, it is important to provide a stable current amplitude output of the LED when pulse width modulation dimming is used.

In order to achieve the above object, a light-emitting device according to the present invention comprises a light-emitting unit having at least one light-emitting diode and a switch connected in series with the light-emitting diode; a conversion circuit having an output end electrically connected to the light-emitting unit And driving a light emitting unit; a sampling circuit comprising a sampling component for indirectly detecting a current flowing through the light emitting diode and outputting a feedback signal; and a current control circuit receiving a current amplitude reference, a feedback signal, and a The external dimming command sends a dimming control signal to the lighting unit and a current control signal to the conversion circuit to control the current amplitude flowing through the LED.

In order to achieve the above object, a control method for a light-emitting device according to the present invention, wherein the light-emitting device comprises a light-emitting unit, a conversion circuit, a current control circuit and a sampling circuit, the light-emitting unit has at least one light-emitting diode, and the control method comprises The following steps: indirectly sensing a current flowing through the light emitting diode by the sampling circuit, and generating a feedback signal; receiving an external dimming command, generating a dimming control signal to control the current of the LED; and receiving A current amplitude reference, and according to the dimming control signal, the current amplitude reference and the feedback signal, generates a current control signal to control the current amplitude flowing through the light emitting diode.

According to the above, a light-emitting device and a control method thereof according to the present invention can indirectly measure the current of the light-emitting diode by setting a sampling circuit at different positions in the light-emitting device circuit. Compared with the direct measurement method for directly measuring the current of the LED branch circuit, the present invention can avoid the constant current amplitude flowing through the light-emitting diode during the dimming process, and can avoid the startup process. The overshoot current flows after the light-emitting diode is turned on; the second is to prevent a current surge at the sampling resistor when the output terminal of the conversion circuit is short-circuited, thereby damaging the device device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a light-emitting device according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings, wherein the same elements will be described with the same reference numerals.

Please refer to FIG. 1 , which is a schematic diagram of a light emitting device according to a preferred embodiment of the present invention.

The light-emitting device 2 is configured to drive a light-emitting unit 22, and the light-emitting unit 22 has at least one light-emitting diode LED. In the embodiment, the light-emitting device 2 includes a conversion circuit 21, a current control circuit 23, and a sampling circuit 24. The conversion circuit 21 is electrically connected to the light emitting unit 22 and drives the light emitting diode LED. The current control circuit 23 is electrically connected to the conversion circuit 21, the sampling circuit 24, and the light-emitting unit 22. The sampling circuit 24 indirectly senses the current I _LED flowing through the light emitting diode and generates a feedback signal I _av . The current control circuit 23 receives a current amplitude reference I _ref , a dimming command Dim and a feedback signal I _av , and sends a dimming control signal D _dim through a first driver Dr1 to the light emitting according to the received signal. The polar LED adjusts the brightness of the LED and generates a current control signal D _{con that is} sent to the conversion circuit 21 to control the magnitude of the current flowing through the light emitting diode. The current amplitude reference I _ref can be generated internally by the illumination device 2 or externally. It should be noted that the conversion circuit 21 of the light-emitting device 2 can be a flyback converter, and of course, a buck converter, a boost converter, or a boost converter. Buck-Boost converter, forward converter, half bridge converter, and full bridge converter are not used to limit this. invention.

Please refer to FIG. 2A, which is a detailed schematic diagram of a light-emitting device 2a according to a first preferred embodiment of the present invention. As shown in FIG. 2A, the conversion circuit 21a is a flyback converter, and includes a buffer circuit 213, a transformer 212, a switch Q2, and a diode D2. The buffer circuit 213 is connected in parallel with the primary side of the transformer 212 and in series with the switch Q2. One end of the secondary side of the transformer 212 is electrically connected to the anode of the diode D2, and the other end of the secondary side of the transformer 212 and an output of the conversion circuit 21a. The terminal is electrically connected, and the cathode of the diode D2 is electrically connected to the other output of the conversion circuit 21a. The snubber circuit 213 includes a resistor R1, a capacitor C2 and a diode D1 for absorbing the leakage inductance generated by the transformer 212 when the switch Q2 is turned off. The resistor R1 is connected in parallel with the capacitor C2 and connected in series with the diode D1. The switch Q2 is usually a MOSFET or a transistor. The switch Q2 has three ends. One end is electrically connected to one end of the transformer 212, one end is electrically connected to a second driver Dr2, and the last end is electrically connected. One input terminal of the sexual connection conversion circuit 21a, the other end of the primary side of the transformer 212 is electrically connected to the other input terminal of the conversion circuit 21a.

It should be noted that, in this embodiment, the input signal of the conversion circuit 21a is a direct current signal, and the direct current signal includes a signal generated by a battery, a battery or an alternating voltage via a rectifying circuit. If the input signal is an AC signal, for example, it can be a commonly known commercial power, that is, an AC power of 90V to 250V, or an AC signal outputted through power conversion, and the front stage of the conversion circuit 21a needs an AC/DC. The converter receives the input signal (not shown), and a detailed embodiment will be described in the third preferred embodiment.

In this embodiment, the light emitting unit 22 is electrically connected to the output end of the conversion circuit 21a, and includes at least one light emitting diode LED, and a switch Q1 connected in series with the light emitting diode LED. By controlling the on and off of the switch Q1, the current flowing through the LED of the LED is controlled, thereby adjusting the brightness of the LED of the LED. The switch Q1 has three ends, one end is electrically connected to the LED of the LED, one end is electrically connected to a first driver Dr1, and the last end is electrically connected to the output end of the conversion circuit 21a. In addition, a capacitor C1 is connected in parallel to the light-emitting unit 22.

In this embodiment, the sampling circuit 24a includes a sampling component 242a and a sampling signal converter 241a. The sampling component 242a is connected in series with the parallel circuit of the light emitting unit 22 and the capacitor C1, and the parallel circuit of the sampling component 242a and the light emitting unit 22 and the capacitor C1. One end of the connection is electrically connected to the sampling signal converter 241a, and the other end is connected to the output terminal of the conversion circuit 21a. The sampling signal converter 241a indirectly obtains the current sampling signal of the LED of the LED in the illumination unit 22 through the sampling element 242a, and generates a feedback signal I _av . The sampling element 242a is a passive component, such as a resistor. As shown in FIG. 2A, if the other end of the sampling element 242a is connected to the output terminal of the conversion circuit 21a and grounded, the sampling signal converter 241a is a filter.
In addition, in the present embodiment, the current control circuit 23a includes a signal converter 231, a pulse width modulation signal generator 232, and a regulator 233.

The pulse width modulation signal generator 232 receives a dimming command Dim, and outputs a dimming control signal D _dim to control the first driver Dr1 to drive the switch Q1 in the light emitting unit 22 to be turned on and off, thereby adjusting the brightness of the LED. . The waveform diagram in FIG. 2A is the current waveform on the LED flowing through the light-emitting unit 22, where T _dim is a period, I _{LED_P} is the current amplitude flowing through the LED, and I _{LED_AV} is the current average value flowing through the LED.

The signal converter 231 receives a current amplitude reference I _ref and converts the output current average reference I _av-ref according to the dimming control signal D _dim output from the pulse width modulation signal generator 232 .

The regulator 233 outputs a current control signal D _con to the second driver Dr2 according to the feedback signal I _av and the current average reference I _av-ref to adjust the output of the conversion circuit 21 a , thereby controlling the current flowing through the LED of the LED Amplitude I _{LED_P} .

Please refer to FIG. 3A at the same time, which is a detailed circuit diagram of the first preferred embodiment of the signal converter 231. The signal converter 231 includes a switch Q11, a resistor R12, and a filter circuit 2311. One end of the switch Q11 is input with the current amplitude reference I _{ref of the} light-emitting diode, one end is input with the dimming control signal D _dim , and the last end is electrically connected with the resistor R12 and the filter circuit 2311 . The filter circuit 2311 can be composed of a resistor R11 connected in series with a capacitor C11, which is not used to limit the present invention. Here, the dimming control signal D _dim is an exemplary periodic wave having a period T _dim , a peak V _cc , and a duty cycle D for driving MOSFET switches of different design requirements. Q11, and the dimming control signal D _dim can be generated by the pulse width modulation signal generator 232 converting the dimming command Dim. In short, the signal converter 231 drives the switch Q11 by the dimming control signal D _dim to convert the current amplitude reference I _{ref of the} light-emitting diode, and then one end of the switch Q11 is output to the filter circuit 2311 for current signal. Processing, the final filter circuit 2311 outputs a current average reference I _av-ref . Therefore, the signal amplitude converter 231 can convert the current amplitude reference I _ref into a current average reference I _av-ref , and the current amplitude reference I _ref is an external input value. As for the dimming control signal D _dim generated by the pulse width modulation signal generator 232, in addition to being transmitted to the signal converter 231, it is also transmitted to the light emitting unit 22 to drive the switch Q1 to operate in the switching state by the first driver Dr1.

Referring again to FIG. 3B, it is a second preferred embodiment of the signal converter 231. Different from FIG. 3A, the signal converter 231 directly filters the dimming control signal D _dim through the filtering circuit 2311 , and outputs a current average value I _av-ref , and the current amplitude of the LED that flows through the LED is referenced by I _{ref .} The internal voltage signal peak value V _{cc of the} device 2a is determined.

Preferably, the regulator 233 is electrically connected to a comparison circuit 234. The comparison circuit 234 can be implemented by using an amplifier or the like, which is not used to limit the present invention, and the comparison circuit 234 is used to compare the current average reference I _av-ref. And the feedback signal I _av difference result, the regulator 233 generates a current control signal D _con according to the difference result of the comparison, and transmits the current control signal D _con to the second driver Dr2 to adjust the output of the conversion circuit 21a to control the current amplitude flowing through the LED. I _{LED_P} . As for the dimming control signal D _dim , its duty ratio D can be changed by the external dimming command Dim to trigger the pulse width modulation signal generator 232.

Please refer to FIG. 2B, which is a schematic diagram of a light-emitting device 2b according to a second preferred embodiment of the present invention. The difference from FIG. 2A is that the composition, the connection relationship, and the setting position of the sampling circuit 24b are different. The other circuit elements, their setting manners, and the input signals are the same as those of FIG. 2A. For the sake of clarity, only the sampling circuit will be described herein. 24b. In this embodiment, the sampling circuit 24b includes a sampling component 242a and a sampling signal converter 241b. The sampling component 242a is connected in series with the switch Q2, and one end electrically connected to the switch Q2 is electrically connected to the sampling signal converter 241b, and the other end is connected. The input terminals of the conversion circuit 21a are electrically connected. The sampling signal converter 241b indirectly obtains the sampling signal of the light-emitting diode LED in the light-emitting unit 22 through the sampling element 242a, and generates a feedback signal I _av . The sampling element 242a is a passive component, such as a resistor. As shown in FIG. 2B, if the other end of the sampling element 242a is electrically connected to the input terminal of the conversion circuit 21a and grounded, the sampling signal converter 241b is a calculator. Therefore, the sampling circuit 24b and the light-emitting unit 22 are respectively located on the primary side and the secondary side of the transformer 212 to form an isolated circuit.

Please refer to FIG. 2C, which is a schematic diagram of a light-emitting device 2c according to a third preferred embodiment of the present invention. The switch circuit 21b of the light-emitting device 2c is a buck converter, and includes a switch Q2, an inductor L1 and a diode D2. The switch Q2 has three ends, one end and one end of the inductor L1. The cathode of the diode D2 is electrically connected, one end is electrically connected to a second driver Dr2, and the last end forms an input end of the step-down converter with the anode of the diode. The second driver Dr2 receives the current control signal D _con outputted by the current control circuit 23a to control the turning on and off of the switch Q2, thereby controlling the current amplitude I _{LED_P} flowing through the light emitting diode. One end of the inductor L1 is electrically connected to one end of the switch Q2 and the cathode of the diode D2, and the other end and the anode of the diode D2 form an output end of the buck converter. The cathode of the diode D2 is electrically connected to one end of the switch Q2, and the anode is grounded and the same end of the inductor L1 is the output end of the conversion circuit 21b. In addition, in this embodiment, as shown in FIG. 2C, the input signal of the conversion circuit 21b is an alternating current signal, which may be a commonly known commercial power, that is, an alternating current of 90V to 250V, or may be output through power conversion. AC power. Therefore, the front stage of the conversion circuit 21b further includes an AC/DC converter 11 for converting the input AC signal into a DC signal and outputting it to the input end of the conversion circuit 21b. One end of the output of the AC/DC converter 11 is electrically connected to the switch Q2, the other end is grounded, and is electrically connected to the anode of the diode D2. If the input signal is a constant current signal, the signal is connected to the input terminal of the conversion circuit 21b without setting the AC/DC converter 11 in the front stage.

The remaining circuit components, including the sampling circuit 24a and its arrangement, are the same as in FIG. 2A and will not be repeated here. It should be particularly noted that in the embodiment and the first preferred embodiment, the conversion circuit is respectively a step-down converter and a flyback converter. However, in practical applications, the conversion circuit can be A boost converter, a l/b converter, a forward converter, a half bridge converter, or a full bridge converter.

Please refer to FIG. 2D, which is a schematic diagram of a light-emitting device 2d according to a fourth preferred embodiment of the present invention. It differs from FIG. 2C in the current control circuit 23b, and the current control circuit 23b in this embodiment includes a digital controller 235. The digital controller 235 performs an internal operation according to a current amplitude reference I _ref , a feedback signal I _{av ,} and a dimming command Dim , and issues a dimming control signal D _{dim to} adjust the brightness of the LED of the LED by the first driver Dr1. And generating a current control signal D _{con is} transmitted to the conversion circuit 21b to control the current amplitude I _{LED_P} flowing through the light emitting diode. The remaining circuit components and input signals, including the sampling circuit 24a and its arrangement, are the same as in Figure 2C.

Please refer to FIG. 2E and FIG. 2F, which are schematic diagrams of the light-emitting devices 2e, 2f of the fifth and sixth preferred embodiments of the present invention. The difference from FIG. 2C is that the sampling circuit 24b, 24c is different in composition, connection relationship and setting position. The other circuit components, their setting modes and input signals are the same as those in FIG. 2C. For the sake of clarity, only the description will be described herein. Sampling circuits 24b, 24c.

As shown in FIG. 2E, the sampling circuit 24b includes a sampling component 242a and a sampling signal converter 241b. The sampling component 242a is connected in series with the diode D2 in the conversion circuit 21b, and the end electrically connected to the diode D2 is also sampled. The signal converter 241b is electrically connected, and the other end is electrically connected to an input terminal of the conversion circuit 21b and a circuit in which the light-emitting unit is connected in parallel with the capacitor C1. The sampling signal converter 241b indirectly obtains the current sampling signal of the LED of the LED in the illumination unit 22 through the sampling element 242a, and generates a feedback signal I _av . The sampling element 242a is a passive component, such as a resistor. As shown in FIG. 2E, if the other end of the sampling element 242a is electrically connected to the input terminal of the conversion circuit 21b and the circuit in which the light-emitting unit 22 is connected in parallel with the capacitor C1, the sampling signal converter 241b is a calculator.

As shown in FIG. 2F, the sampling circuit 24c includes a sampling component 242a and a sampling signal converter 241b. One end of the sampling component 242a is electrically connected to the input end of the conversion circuit 21b and the sampling signal converter 241b, and the other end and the conversion circuit 21b. The anode of the diode D2 and the light-emitting unit 22 are electrically connected to the parallel circuit of the capacitor C1 and grounded. The sampling signal converter 241b indirectly obtains the current sampling signal of the LED of the LED in the illumination unit 22 through the sampling element 242a, and generates a feedback signal I _av . The sampling element 242a is a passive component, such as a resistor. As shown in FIG. 2F, the sampling signal converter 241b is a calculator.

Please refer to FIG. 2G, which is a schematic diagram of a light-emitting device 2g according to a seventh preferred embodiment of the present invention. The difference from FIG. 2C is that the composition, the connection relationship and the setting position of the sampling circuit 24d are different. The remaining circuit elements, their setting modes and input signals are the same as those of FIG. 2C. For the sake of clarity, only the sampling circuit will be described herein. 24d. The sampling circuit 24d includes a sampling component 242b and a sampling signal converter 241b. One end of the sampling component 242b is electrically connected to the sampling signal converter 241b and inductively coupled to the inductor L1. The sampling signal converter 241b indirectly obtains the sampling signal of the light-emitting diode LED in the light-emitting unit 22 through the sampling element 242b, and generates a feedback signal I _av . The sampling element 242b is a passive component, such as a winding. As shown in FIG. 2G, if the other end of the sampling element 242b is grounded, the sampling signal converter 241b is a calculator.

In the above embodiment, the sampling component in the sampling circuit 24a, 24b, 24c, 24d may also be a current transformer, and the sampling signal converter indirectly obtains the current signal of the LED in the light emitting unit 22 through the current transformer, and generates a feedback signal. I _av .

In addition, please refer to FIG. 4A, which is a flow chart of a method for controlling a light-emitting device according to the present invention. The illuminating device comprises a illuminating unit, a converting circuit, a current control circuit and a sampling circuit, and the illuminating unit has at least one illuminating diode. The connection relationship of the light-emitting device and its structural change are as described above and will not be repeated here. The control method comprises the steps of: indirectly sensing a current flowing through the light emitting diode by the sampling circuit, and generating a feedback signal (S10); receiving an external dimming command to generate a dimming control signal to control the light emitting The current of the polar body (S20); receiving a current amplitude reference, and generating a current control signal according to the dimming control signal, the current amplitude reference and the feedback signal, and controlling the current amplitude flowing through the light emitting diode (S30) ).

In a preferred embodiment, as shown in FIG. 4B, step S30 may further include the following substep: adjusting the current amplitude reference to a current average reference according to the dimming control signal generated by the external dimming command (S31) Comparing the feedback signal with the current average reference to form a difference (S32); and generating a current control signal according to the difference, controlling the current amplitude flowing through the LED (S33). Further, in the present embodiment, the current amplitude reference may be generated internally by the light-emitting device or externally.

In summary, according to the illuminating device and the control method thereof according to the present invention, the current of the illuminating diode can be indirectly measured by setting a sampling circuit at different positions in the illuminating device circuit. Compared with the direct measurement method for directly measuring the current of the LED branch circuit, the present invention can avoid the constant current amplitude flowing through the light-emitting diode during the dimming process, and can avoid the startup process. The overshoot current flows after the light-emitting diode is turned on; the second is to prevent a current surge at the sampling resistor when the output terminal of the conversion circuit is short-circuited, thereby damaging the device device.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

11. . . AC/DC converter

2, 2a, 2b, 2c, 2d, 2e, 2f, 2g. . . Illuminating device

21, 21a, 21b. . . Conversion circuit

212. . . transformer

213. . . Buffer circuit

twenty two. . . Light unit

23, 23a, 23b. . . Current control circuit

231. . . Signal converter

2311. . . Filter circuit

232. . . Pulse width modulated signal generator

233. . . Regulator

234. . . Comparison circuit

235. . . Digital controller

24, 24a, 24b, 24c, 24d. . . Sampling circuit

241a, 241b. . . Sampled signal converter

242a, 242b. . . Sampling component

Dr1. . . First drive

Dr2. . . Second drive

L1. . . inductance

C1, C2, C11. . . capacitance

R11, R12. . . resistance

Q1, Q2, Q11, S. . . switch

D1, D2. . . Dipole

I _LED . . . Light-emitting diode current

I _{LED_P} . . . Current value of light-emitting diode

I _LED-AV . . . Current average of the light-emitting diode

I _ref . . . Current amplitude reference

I _av-ref . . . Current average reference

I _av . . . Feedback signal

Dim. . . Dimming command

D _con . . . Current control signal

D _dim . . . Dimming control signal

V _cc . . . Peak

T _dim . . . cycle

D. . . Duty cycle

S10~S30, S31~S33. . . step

1 is a schematic view of a preferred light emitting device in accordance with the present invention;
2A to 2G are schematic views of a light-emitting device according to first to seventh preferred embodiments of the present invention;
3A and FIG. 3B are schematic circuit diagrams of a preferred signal converter according to the present invention; and FIGS. 4A and 4B are flow diagrams showing a control method of a preferred light-emitting device according to the present invention.

2. . . Illuminating device

twenty one. . . Conversion circuit

twenty two. . . Light unit

twenty three. . . Current control circuit

twenty four. . . Sampling circuit

Dr1. . . First drive

Q1. . . switch

I _LED . . . Light-emitting diode current

I _ref . . . Current amplitude reference

I _av . . . Feedback signal

Dim. . . Dimming command

D _con . . . Current control signal

D _dim . . . Dimming control signal

Claims (21)

A light emitting device comprising:
a light emitting unit having at least one light emitting diode and a switch connected in series with the light emitting diode;
a conversion circuit, the output end of which is electrically connected to the light emitting unit and drives the light emitting unit;
a sampling circuit comprising a sampling component for indirectly detecting a current flowing through the LED and outputting a feedback signal; and a current control circuit for receiving a current amplitude reference, the feedback signal and an external dimming command And transmitting a dimming control signal to the light emitting unit and a current control signal to the converting circuit to control a current amplitude flowing through the light emitting diode. The illuminating device of claim 1, wherein the current amplitude reference is generated internally by the illuminating device or externally. The illuminating device of claim 1, wherein the conversion circuit is a flyback converter, a buck converter, a boost converter, a l/b converter, and a positive Converter, half bridge converter or a full bridge converter. The illuminating device of claim 1, wherein the current control circuit comprises:
a pulse width modulation signal generator, which receives an external dimming signal and outputs the dimming control signal to the light emitting unit;
a signal converter that receives the current amplitude reference and converts it into a current average reference according to the dimming control signal; and a regulator that generates a current according to the current average reference and the feedback signal The control signal is transmitted to the conversion circuit. The illuminating device of claim 4, wherein the current control circuit further comprises:
A comparison circuit is electrically connected to the regulator and outputs a current difference value compared to the current average reference and the feedback signal. The illuminating device of claim 1, further comprising a capacitor connected in parallel with the illuminating unit; the sampling circuit further comprising a sampling signal converter. The illuminating device of claim 6, wherein the sampling component in the sampling circuit is connected in series with the parallel circuit of the illuminating unit and the capacitor, and the sampling element and one end of the illuminating unit and the capacitor parallel circuit are connected in series. It is also electrically connected to the sampling signal converter, and the other end is electrically connected to the output of the conversion circuit. The illuminating device of claim 7, wherein the other end of the sampling element is electrically connected to the output of the conversion circuit and grounded, and the sampling signal converter is a filter. The illuminating device of claim 8, wherein the conversion circuit is a flyback converter, a buck converter, a boost converter, a liter/step converter, and a positive Converter, half bridge converter or a full bridge converter. The illuminating device of claim 9, wherein the current control circuit is a digital controller. The illuminating device of claim 6, wherein the conversion circuit is a flyback converter, including a snubber circuit;
a transformer, the primary side of the transformer is connected in parallel with the snubber circuit;
a switch, the switch is connected in series with the buffer circuit and the parallel circuit formed on the primary side of the transformer, the switch is turned on and off according to the current control signal sent by the current control circuit; and a diode, the diode The body is connected in series with the secondary side of the transformer;
The sampling component in the sampling circuit is connected in series with the switch, and one end electrically connected to the switch is also electrically connected to the sampling signal converter, and the other end is electrically connected to the input end of the conversion circuit. The light-emitting device of claim 11, wherein the other end of the sampling element is electrically connected to the input end of the conversion circuit and grounded, and the sampling signal converter is a calculator. The illuminating device of claim 6, wherein the conversion circuit is a buck converter, including a switch;
a diode, a cathode of the diode is electrically connected to one end of the switch, an anode is grounded, and an inductor is electrically connected to one end of the switch and the cathode of the diode, and the other end is opposite to the second An anode of the polar body forms an output of the buck converter;
The other end of the switch and the anode of the diode form an input end of the buck converter, and the switch performs an on and off operation according to the current control signal output by the current control circuit. The illuminating device of claim 13, wherein the sampling element is connected in series with the diode in the buck converter, and an end electrically connected to the diode is further electrically connected to the sampling signal converter. The other end is electrically connected to the input end of the buck converter and the parallel circuit of the light emitting unit and the capacitor. The illuminating device of claim 14, wherein the other end of the sampling component is electrically connected to the buck converter input end and the parallel circuit of the illuminating unit and the capacitor, and the sampling signal converter is a calculator. The illuminating device of claim 13, wherein one end of the sampling element is electrically connected to the anode of the diode and the parallel circuit of the illuminating unit and the capacitor in the buck converter, and is grounded. One end is electrically connected to the buck converter input and the sampling signal converter, and the sampling signal converter is a calculator. The illuminating device of claim 13, wherein the sampling element is inductively coupled to the inductance of the buck converter, and the sampling signal converter is a calculator. The illuminating device of claim 7, wherein the sampling element is a resistive element or a current transformer. A method for controlling a light-emitting device, wherein the light-emitting device comprises a light-emitting unit, a conversion circuit, a current control circuit and a sampling circuit, the light-emitting unit having at least one light-emitting diode, the control method comprising the following steps:
The current flowing through the light emitting diode is indirectly sensed by the sampling circuit, and a feedback signal is generated;
Receiving an external dimming command, generating a dimming control signal to control the current of the LED; and receiving a current amplitude reference, and according to the dimming control signal, the current amplitude reference, and the feedback signal, A current control signal is generated to control the magnitude of the current flowing through the light emitting diode. For example, the control method described in claim 19 of the patent scope further includes:
And adjusting the current amplitude reference to a current average reference according to the dimming control signal generated by the external dimming signal;
Comparing the feedback signal with the current average reference to form a difference; and according to the difference, generating the current control signal to control a current amplitude flowing through the LED. The control method described in claim 19 or 20 of the patent application further includes:
The current amplitude reference is generated internally by the illumination device or externally.