CN100531487C - LED driver - Google Patents

Abstract

The invention relates to a light emitting diode driving device which is used for controlling the brightness of a light emitting diode. The invention comprises an energy conversion element and a change-over switch which are coupled in series with a light-emitting diode and used for controlling the current of the light-emitting diode. The diode is coupled to the energy conversion element, has a flywheel function, and discharges energy stored on the energy conversion element through the light emitting diode. The control circuit outputs a control signal according to the current of the light emitting diode to control the switch. The voltage signal obtained from the light emitting diode is related to the temperature of the light emitting diode, and the magnitude of the voltage signal can adjust the current of the light emitting diode. Therefore, the temperature of the light emitting diode can adjust the current of the light emitting diode.

Description

LED driver

technical field

The invention relates to a light-emitting diode driving device, in particular to a device for controlling the brightness of the light-emitting diode by a control circuit.

Background technique

The luminous effect of light-emitting components, such as light-emitting diodes (LEDs), is determined by the magnitude of the current flowing through the light-emitting diodes. High currents flowing through the light-emitting diodes will obtain high-brightness luminous effects. On the contrary, if the current of the light-emitting diodes is reduced , the brightness of the light-emitting diode will be relatively weakened. But continuously supplying high current will reduce the lifetime of the LED and waste a lot of power. FIG. 1 is a first embodiment of a conventional LED driving circuit. The adjustable voltage source 10 provides the LED current I _LED flowing through the LEDs 20 , 21 .

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; led</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 20</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 25</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 15</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

V _F20 , V _F21 . . . V _F25 are the forward voltage drops of the LEDs 20 , ₂₁ .

In the first embodiment, the main disadvantage of the existing LED driving circuit is that the forward voltage drop of the LEDs 20, 21...25 is not a fixed value, and the LED current I _LED will be affected by the variation of mass production and temperature. ; At the same time, the resistor 15 will cause the power loss of the circuit.

FIG. 2 is a second embodiment of a conventional LED driving circuit. In the second embodiment, the voltage source 30 is used to provide a fixed power for the LEDs 20 , 21 . . . 25 . The luminous effects of the light emitting diodes 20 , 21 . . . 25 can be adjusted by the current source 35 . However, in this control mode, since the voltage source 30 is high voltage, the voltage drops of the light emitting diodes 20, 21...25 are low voltage, so the current source 35 will generate a huge power loss.

Contents of the invention

The technical problem to be solved by the present invention is to provide a switchable LED driving device to control the brightness of a LED.

In order to achieve the above object, the present invention provides a light-emitting diode driving device, which is used to drive a light-emitting diode, which is characterized in that it includes: a transformer, coupled in series to the light-emitting diode; a switch, coupled in series to the light-emitting diode The diode and the transformer, the switch is used to control the current of a light emitting diode; a first resistor, coupled in series with the light emitting diode, the first resistor detects the current of the light emitting diode, and is used to output a current signal; a control circuit, coupled to the light emitting diode, the first resistor and the switch, the control circuit obtains a voltage signal from the light emitting diode and the current signal from the first resistor, and outputs a A control signal is sent to the switching switch; a diode is coupled in parallel with the transformer and the light-emitting diode, and the diode is used to discharge the stored energy of the transformer through the light-emitting diode; and a second resistor is coupled to the control The circuit is used to determine an adjustment slope, and the adjustment slope represents the relative relationship between the change of a first critical value and the change of the light emitting diode current; wherein, the control signal controls the switching switch and the light emitting diode current, when the current signal When it is greater than the first critical value, the control signal turns off the switch, and the first critical value changes with the voltage signal; when the current signal is smaller than a second critical value, the control signal is passed through an adjustable delay time After that, to turn on the toggle switch conduction.

The above light emitting diode drive device is characterized in that the control circuit includes: a delay circuit, which is used to output a delay signal according to the cut-off of the control signal, and the delay signal has an adjustable delay time, wherein the control signal is in the The adjustable delay time is disabled during this period; a comparison circuit is used to output an enable signal according to the current signal being less than the second critical value; a first control circuit is used to output the enable signal according to the delay signal and the enable signal to enable the control signal; a second control circuit for disabling the control signal according to the current signal being greater than the first critical value; and a sampling circuit coupled to the light emitting diode, the sampling circuit according to the voltage signal , for outputting a first sampling signal and a second sampling signal; wherein, the first sampling signal and the second sampling signal are used for adjusting the first critical value.

The above LED driving device is characterized in that the first sampling signal and the second sampling signal respectively represent a first sequence of the LED according to the first current of the LED and the second current of the LED. forward voltage and a second forward voltage of the LED.

The present invention also provides a light emitting diode driving device, which is used to drive a light emitting diode, which is characterized in that it includes: a transformer, coupled in series with the light emitting diode; a switch, coupled in series with the light emitting diode and the transformer The switch is used to control the current of a light emitting diode; a first resistor is coupled in series with the light emitting diode, and the first resistor detects the current of the light emitting diode to output a current signal; a control circuit is coupled to the light emitting diode diode, the first resistor and the switch, the control circuit obtains a voltage signal from the light emitting diode and the current signal from the first resistor, and outputs a control signal to the switch according to the voltage signal and the current signal a switch; and a diode, coupled in parallel to the transformer and the light-emitting diode, the diode is used to discharge the stored energy of the transformer through the light-emitting diode; wherein, the control signal controls the switching switch and the light-emitting diode current, When the current signal is greater than a first critical value, the control signal turns off the switching switch; when the current signal is smaller than a second critical value, the control signal turns on the switching switch.

The characteristic of the LED driving device above is that the first critical value varies with the voltage signal.

The above-mentioned light-emitting diode driving device is characterized in that the control circuit includes: a delay circuit for outputting a delay signal according to the cut-off of the control signal, and the delay signal has an adjustable delay time; a comparison circuit for outputting a delay time according to the current The signal is smaller than the second critical value to output an enable signal; a first control circuit is used to enable the control signal according to the delay signal and the enable signal; a second control circuit is used to enable the control signal according to the current signal greater than the The first threshold is used to disable the control signal; and a sampling circuit is coupled to the light emitting diode, and the sampling circuit is used to output a first sampling signal and a second sampling signal according to the voltage signal; wherein, The first sampling signal and the second sampling signal are used to adjust the first threshold.

The above LED driving device is characterized in that the first sampling signal and the second sampling signal respectively represent a first sequence of the LED according to the first current of the LED and the second current of the LED. forward voltage and a second forward voltage.

The present invention also provides a light emitting diode driving device, which is used to drive a light emitting diode, which is characterized in that it includes: a transformer, coupled in series with the light emitting diode; a switch, coupled in series with the light emitting diode and the transformer The changeover switch is used to control the current of a light emitting diode; a control circuit is coupled to the light emitting diode, obtains a voltage signal from the light emitting diode, and the control circuit outputs a control signal according to the voltage signal and the current of the light emitting diode; and a diode, coupled in parallel to the transformer and the light emitting diode, and the diode is used to discharge the stored energy of the transformer through the light emitting diode; wherein, the control signal controls the switching switch and the light emitting diode current, and the light emitting diode The diode current passes through a resistor to generate a current signal, and when the LED current is greater than a first critical value, the control signal turns off the switching switch.

The characteristic of the LED driving device above is that the first critical value varies with the voltage signal.

The above-mentioned light-emitting diode driving device is characterized in that the control circuit includes: a delay circuit for outputting a delay signal according to the cut-off of the control signal, and the delay signal has an adjustable delay time; a comparison circuit for outputting a delay time according to the current The signal is smaller than the second critical value to output an enable signal; a first control circuit is used to enable the control signal according to the delay signal and the enable signal; a second control circuit is used to enable the control signal according to the current signal greater than the The first threshold is used to disable the control signal; and a sampling circuit is coupled to the light emitting diode, and the sampling circuit is used to output a first sampling signal and a second sampling signal according to the voltage signal; wherein, The first sampling signal and the second sampling signal are used to adjust the variation of the first threshold value.

The above LED driving device is characterized in that the first sampling signal and the second sampling signal respectively represent a first sequence of the LED according to the first current of the LED and the second current of the LED. forward voltage and a second forward voltage.

The LED driving device of the present invention can accurately obtain the temperature of the LED through the voltage signal VD, and use the temperature to adjust the current of the LED to compensate the chromaticity and lumen of the LED.

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, but not as a limitation of the present invention.

Description of drawings

Fig. 1 is the first embodiment of the existing LED control circuit;

Fig. 2 is the second embodiment of the existing LED control circuit;

3 is a schematic circuit diagram of a switchable light-emitting diode driving device of the present invention;

4A and 4B are schematic diagrams of current waveforms flowing through a light-emitting diode according to the present invention;

Fig. 5 is the circuit schematic diagram of the control circuit of the present invention;

Fig. 6 is the circuit schematic diagram of the delay circuit of the present invention;

Fig. 7 is the circuit diagram of sampling circuit of the present invention;

Fig. 8 is a schematic diagram of the signal waveform of the control circuit of the present invention; and

FIG. 9 is a schematic circuit diagram of the current regulation circuit of the present invention.

Among them, reference signs:

20, 21...25: LED 10: Voltage source

15: Resistor I _LED : LED current

30: Voltage source 35: Current source

50: Energy conversion element 20 to 25: Light emitting diode

70: Toggle switch I _LED : LED current

75: first resistor V _S : current signal

V _G : Control signal V _D : Voltage signal

100: Control circuit 59: Second resistor

55: Diode T _D : Delay time

V _CNT : Control voltage 60: Current I _LED waveform

65: the maximum value of the first critical value _VR V _TH : the second critical value

180: AND gate 131: Inverter

140: flip-flop INH: delayed signal

V _F : enabling signal 115: second control circuit

200: delay circuit V _H1 : first sampling signal

V _H2 : Second sampling signal 600 : Current adjustment circuit

I _R : constant current 110: comparison circuit

_VR : first critical value 300: sampling circuit

250: Constant current source 210: Operational amplifier

205: Resistors 220, 230, 231, 270: Transistors

260: Capacitor 280: Inverter

350: Pulse generator SMP1: First pulse

SMP2: second pulse T _D1 : first delay time

T _D2 : second delay time 310, 311: switching switch

315, 317: Capacitors

610, 611, 615: operational amplifiers

620, 621, 59, 650: Resistors

630~635: transistor I ₆₃₃ , I ₆₃₅ : current

Detailed ways

Please refer to FIG. 3 , which is a schematic circuit diagram of the switching LED driving device of the present invention. The switchable LED driving device of the present invention uses an energy conversion element 50 coupled in series with the LEDs 20-25, and the energy conversion element 50 can be a transformer. A switch 70 is coupled in series with the LEDs 20 - 25 and the energy conversion element 50 , and the switch 70 is used to control the LED current I _LED flowing through the LEDs 20 - 25 . A first resistor 75 is coupled to the LEDs 20 - 25 , the first resistor 75 detects the LED current I _LED , and outputs a current signal V _S to a control circuit 100 . The control circuit 100 is further coupled to the LED 25 to receive a voltage signal V _D , and the voltage signal V _D is the forward voltage of the LED 25 . A diode 55 is coupled to the energy conversion element 50 and the LEDs 20 - 25 .

When the current signal V _S is higher than a first critical value _VR in the control circuit 100 , the switch 70 is turned off, thereby limiting the LED current I _LED . The maximum value of the light-emitting diode current I _LED can be obtained by the following formula (2):

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; led</span>}}{<span\; class="notranslate">\; (</span>}_{\mathrm{<span\; class="notranslate">\; MAX</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; IN</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 20</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 25</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="50"\; label="L"\; filenames="C20051002306400171.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 50</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; ON</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

_In the above formula (2), L ₅₀ represents the inductance value of the energy conversion element ₅₀ ; T _ON represents the conduction time of the switch ₇₀ ; drop.

When the switch 70 is turned off, the energy stored in the energy conversion element 50 will be discharged through the diode 55 and the LEDs 20 - 25 . During the energy discharge of the energy conversion element 50 , the control circuit 100 simultaneously detects the value of the forward voltage of the LED 25 . According to the characteristics of the LED 25 , the forward voltage of the LED 25 is inversely proportional to its temperature. Therefore, the temperature of the LED 25 can be known from the voltage signal V _D detected by the LED 25 .

Please refer to FIG. 4A and FIG. 4B , which are schematic diagrams of the current waveform of the light emitting diode of the present invention. Wherein, the maximum value 65 of the first critical value _VR limits the peak value of the waveform 60 of the LED current I _LED . When the current signal V _S is smaller than a second threshold V _TH , the switch 70 is turned on after a delay time T _D for establishing the LED current I _LED . The maximum value 65 of the first critical value V _R can determine the average value of the LED current I _LED , therefore, the average value of the LED current I _LED is controlled to be a fixed value, and will not vary with the inductance of the energy conversion element 50 value changes. In addition, the delay time T _D can be adjusted to adjust the amplitude of the LED current I _LED and the brightness of the LEDs 20 - 25 .

The control circuit 100 obtains the LED current I _LED , and obtains the voltage signal V _D from the LED 25 , and at the same time, the control circuit 100 generates a control signal V _G according to the voltage signal V _D and the operating current I _LED of the LED 25 . The control signal V _G is used to control the switching action of the switch 70 to further adjust the LED current I _LED . In order to keep the chromaticity and lumens of the LEDs 20-25 stable, the LEDs 20-25 must consider the influence of the temperature of the LEDs 20-25, and the LED current _ILED needs to be adjusted according to the temperature.

In the present invention, the first critical value V _R and the voltage signal V _D are respectively related to the LED current I _LED and the temperature. The variation of the first critical value V _R is based on the voltage signal V _D , and the variation of the first critical value _VR can compensate the chromaticity and lumens of the LEDs 20 - 25 . In addition, in order to adapt to the characteristics of various light emitting diodes, the present invention can further use a second resistor 59 coupled to the control circuit 100 to determine an adjustment slope (slope), the adjustment slope represents the first critical value _VR The relative relationship between the change and the change of the voltage signal V _D.

Please refer to FIG. 5 , which is a schematic circuit diagram of the control circuit of the present invention. In the control circuit 100, when the current signal V _S is greater than the first critical value _VR , the control signal V _G will be disabled, so that the switch 70 is turned off. In the control circuit 100 , when the current signal V _S is smaller than a second critical value V _TH , the control signal V _G is enabled by an enable signal V _F , thereby controlling the switch 70 to be turned on. In the control circuit 100 , this voltage signal V _D is obtained from the light emitting diode 25 .

In the control circuit 100, a first control circuit includes an AND gate 180, an inverter 131, and a flip-flop 140. The first control circuit is used to output the control signal according to a delay signal INH and the enable signal _VF . Signal V _G . The output terminal of the AND gate 180 is coupled to the flip-flop 140 , and the control signal V _G is generated from the output terminal of the flip-flop 140 . A second control circuit 115 is coupled to the flip-flop 140 , and when the current signal V _S is greater than the first threshold _VR , the second control circuit 115 disables the control signal V _G through the flip-flop 140 .

A delay circuit 200 is coupled to the first input terminal of the AND gate 180 through the inverter 131, and the delay circuit 200 outputs a delayed signal INH with a delay time T _D to the AND gate 180 under the control signal V _G disabled state. the first input terminal of . Thus, the control signal V _G is disabled during the delay time T _D . A sampling circuit 300 is coupled to the LED, and the sampling circuit is used to output a first sampling signal V _H1 and a second sampling signal V _H2 according to the voltage signal V _D . A current adjustment circuit 600 is coupled to the sampling circuit 300 and a constant current I _R , the current adjustment circuit 600 receives the first sampling signal V _H1 , the second sampling signal V _H2 and the constant current I _R to adjust the first critical value V _R amplitude value. A comparison circuit 110 is coupled to the second input terminal of the AND gate 180, and is used to output an enable signal V _F according to the current signal V _S being smaller than a second critical value V _TH , and the enable signal V _F is coupled to the AND gate. The second input terminal 180 can enable the control signal V _G .

Please refer to FIG. 6 , which is a schematic circuit diagram of the delay circuit of the present invention. In the delay circuit 200, a certain current source 250 is coupled to the input terminal IN of the control circuit 100, and the control circuit 100 is coupled to one end of a resistor (not shown) through the input terminal IN, and the other end of the resistor can be coupled to Connected to a ground reference terminal, or the input terminal IN can also be coupled to a control voltage V _CNT , which can be used to adjust the delay time T _D and further control the brightness of the LEDs 20 - 25 .

A voltage/current conversion circuit includes an operational amplifier 210 , a resistor 205 and a transistor 220 , 230 , 231 . The voltage/current conversion circuit generates a charging current on the transistor 231 according to the voltage on the resistor coupled to the input terminal IN. The delay circuit 200 also uses a capacitor 260 coupled to the transistor 231 and a transistor 270, and the transistor 270 is controlled by the control signal V _G . When the control signal V _G is disabled so that the transistor 270 is turned off, the charging current generated on the transistor 231 immediately charges the capacitor 260 , however when the transistor 270 is turned on, the voltage on the capacitor 260 is discharged through the transistor 270 . An input terminal of an inverter 280 is coupled to the capacitor 260 , and the inverter 280 generates the delayed signal INH at the output terminal according to the voltage established on the capacitor 260 .

Please refer to FIG. 7 , which is a schematic circuit diagram of the sampling circuit of the present invention. In the sampling circuit 300, a pulse generator 350 is used to generate a first pulse SMP1 and a second pulse _SMP2 according to the disabling of the control signal _VG and the current signal VS. In conjunction with FIG. 8 , it is a schematic diagram of signal waveforms of the control circuit of the present invention. Wherein, the first pulse wave SMP1 is generated after a first delay time T _D1 after the control signal V _G is disabled, and the first delay time T _D1 can ensure that the voltage signal V _D is a steady state. The second pulse wave SMP2 is generated before the current signal V _S drops to zero, and the second delay time T _D2 can ensure that the second pulse wave SMP2 is generated before the current signal V _S drops to zero. The first pulse SMP1 and the second pulse SMP2 respectively control the switching on or off of the switches 310 and 311 . The switching switches 310 and 311 respectively sample the voltage signal V _D , and respectively establish a first sampling signal V _H1 and a second sampling signal V _H2 on the capacitors 315 and 317 . Therefore, the first sampling signal V _H1 and a second sampling signal V _H2 respectively represent a first forward direction of the LEDs 20-25 according to a first current and a second current flowing through the LEDs 20-25. The voltage V1 and a second forward voltage V2.

Please refer to FIG. 9 , which is a schematic circuit diagram of the current adjustment circuit of the present invention. In the current regulation circuit 600 , a differential circuit includes operational amplifiers 610 , 611 and resistors 620 , 621 . The differential circuit receives the first sampling signal V _H1 and the second sampling signal V _H2 , and outputs a voltage difference at an output terminal of the differential circuit. The output terminal of the differential circuit, that is, the output terminal of the operational amplifier 610 is coupled to the input terminal of an operational amplifier 615 . The operational amplifier 615, the transistors 630-635 and the resistor 650 form another voltage/current conversion circuit. The other voltage/current conversion circuit generates currents I ₆₃₃ , I ₆₃₅ according to the voltage difference and the resistance of the second resistor 59 . The resistor 650 is coupled to the constant current I _R , the currents I ₆₃₃ and I ₆₃₅ to generate the first threshold V _R . The value of the first critical value _VR can be effectively adjusted by adjusting the current values of the currents I ₆₃₃ and I ₆₃₅ .

According to the above description, the first sampling signal V _H1 and a second sampling signal V _H2 respectively represent the first sequence of the light emitting diodes 20-25 according to a first current and a second current flowing through the light-emitting diodes 20-25. The forward voltage V1 and the second forward voltage V2.

The first forward voltage V1 and the second forward voltage V2 correspond to the first LED current I ₁ and the second LED current I ₂ , and the first LED current I ₁ and the second LED current I ₂ can be obtained by the following formula (3), (4) get it:

I ₁ =I _O ×e ^V1/VT (3)

I ₂ =I _O ×e ^V2/VT (4)

In formulas (3) and (4), VT can be obtained from formula (5):

$\mathrm{<span\; class="notranslate">\; VT</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Temp</span>}}{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In formula (5), Temp can be obtained from formula (6):

$\mathrm{<span\; class="notranslate">\; Temp</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; q</span>}}{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; V</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; V</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

In the above formulas (3) to (6), k is Boltzmann's constant (Boltzmann's constant); q is the electronic charge; Temp is the absolute temperature; Io is the reverse saturation current of the diode.

To sum up, the LED driving device of the present invention can accurately obtain the temperature of the LEDs 20-25 through the voltage signal VD, and use the temperature to adjust the LED current to compensate the chromaticity and lumens of the LEDs 20-25.

Of course, the present invention can also have other various embodiments, and those skilled in the art can make various corresponding changes and deformations according to the present invention without departing from the spirit and essence of the present invention, but these corresponding Changes and deformations should all belong to the protection scope of the claims of the present invention.

Claims (11)

1. A light-emitting diode driving device, used to drive a light-emitting diode, is characterized in that, comprising: a transformer, coupled in series with the LED; a switch, coupled in series with the light emitting diode and the transformer, the switch is used to control the current of a light emitting diode; A first resistor, coupled in series with the light emitting diode, the first resistor detects the current of the light emitting diode to output a current signal; A control circuit, coupled to the light emitting diode, the first resistor and the switch, the control circuit obtains a voltage signal from the light emitting diode and the current signal from the first resistor, and according to the voltage signal and the current signal for outputting a control signal to the switch; a diode coupled in parallel to the transformer and the light emitting diode, the diode is used to discharge the stored energy of the transformer through the light emitting diode; and A second resistor, coupled to the control circuit, is used to determine an adjustment slope, the adjustment slope represents the relative relationship between the change of a first critical value and the change of the LED current; Wherein, the control signal controls the switching switch and the LED current, when the current signal is greater than the first critical value, the control signal turns off the switching switch, and the first critical value changes with the voltage signal; when the When the current signal is less than a second critical value, the control signal turns on the switching switch after an adjustable delay time. 2. The LED driving device according to claim 1, wherein the control circuit comprises: a delay circuit for outputting a delay signal according to the cut-off of the control signal, the delay signal has an adjustable delay time, wherein the control signal is disabled during the adjustable delay time; a comparator circuit for outputting an enabling signal according to the current signal being smaller than the second critical value; a first control circuit, used to enable the control signal according to the delay signal and the enable signal; a second control circuit for disabling the control signal based on the current signal being greater than the first threshold; and a sampling circuit, coupled to the light emitting diode, the sampling circuit is used to output a first sampling signal and a second sampling signal according to the voltage signal; Wherein, the first sampling signal and the second sampling signal are used to adjust the first threshold. 3. The LED driving device according to claim 2, wherein the first sampling signal and the second sampling signal respectively represent the A first forward voltage of the LED and a second forward voltage of the LED. 4. A light-emitting diode driving device for driving a light-emitting diode, characterized in that it comprises: a transformer, coupled in series with the LED; a switch, coupled in series with the light emitting diode and the transformer, the switch is used to control the current of a light emitting diode; A first resistor, coupled in series with the light emitting diode, the first resistor detects the current of the light emitting diode to output a current signal; A control circuit, coupled to the light emitting diode, the first resistor and the switch, the control circuit obtains a voltage signal from the light emitting diode and the current signal from the first resistor, and according to the voltage signal and the current signal for outputting a control signal to the switch; and a diode, coupled in parallel to the transformer and the light emitting diode, the diode is used to discharge the stored energy of the transformer through the light emitting diode; Wherein, the control signal controls the switching switch and the LED current, when the current signal is greater than a first critical value, the control signal turns off the switching switch; when the current signal is smaller than a second critical value, the control signal Turn on the toggle switch to conduct. 5. The light emitting diode driving device according to claim 4, wherein the first critical value varies with the voltage signal. 6. The LED driving device according to claim 4, wherein the control circuit comprises: A delay circuit is used to output a delay signal according to the cut-off of the control signal, and the delay signal has an adjustable delay time; a comparator circuit for outputting an enabling signal according to the current signal being smaller than the second critical value; a first control circuit, used to enable the control signal according to the delay signal and the enable signal; a second control circuit for disabling the control signal based on the current signal being greater than the first threshold; and a sampling circuit coupled to the light emitting diode, the sampling circuit is used to output a first sampling signal and a second sampling signal according to the voltage signal; Wherein, the first sampling signal and the second sampling signal are used to adjust the first threshold. 7. The light emitting diode driving device according to claim 6, wherein the first sampling signal and the second sampling signal represent respectively according to the first current of the light emitting diode and the second current of the light emitting diode A first forward voltage and a second forward voltage of the LED. 8. A light-emitting diode driving device for driving a light-emitting diode, characterized in that it comprises: a transformer, coupled in series with the LED; a switch, coupled in series with the light emitting diode and the transformer, the switch is used to control the current of a light emitting diode; A control circuit, coupled to the light emitting diode, obtains a voltage signal from the light emitting diode, and the control circuit outputs a control signal according to the voltage signal and the current of the light emitting diode; and a diode, coupled in parallel to the transformer and the light emitting diode, the diode is used to discharge the stored energy of the transformer through the light emitting diode; Wherein, the control signal controls the switching switch and the LED current, the LED current passes through a resistor to generate a current signal, and when the LED current is greater than a first critical value, the control signal turns off the switching switch. 9. The light emitting diode driving device according to claim 8, wherein the first critical value varies with the voltage signal. 10. The LED driving device according to claim 8, wherein the control circuit comprises: A delay circuit is used to output a delay signal according to the cut-off of the control signal, and the delay signal has an adjustable delay time; a comparator circuit for outputting an enabling signal according to the current signal being smaller than the second critical value; a first control circuit, used to enable the control signal according to the delay signal and the enable signal; a second control circuit for disabling the control signal based on the current signal being greater than the first threshold; and a sampling circuit, coupled to the light emitting diode, the sampling circuit is used to output a first sampling signal and a second sampling signal according to the voltage signal; Wherein, the first sampling signal and the second sampling signal are used to adjust the variation of the first critical value. 11. The light emitting diode driving device according to claim 10, wherein the first sampling signal and the second sampling signal represent respectively according to the first current of the light emitting diode and the second current of the light emitting diode A first forward voltage and a second forward voltage of the LED.

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