TWM294095U - Switching LED driver - Google Patents

Description

• M294095 - VIII, new description: [New technical field] This creation is about a light-emitting diode driving device, especially a device for controlling the brightness of the light-emitting diode. [Prior Art] The illuminating effect of a light-emitting element such as a light emitting diode (LED) is determined by the magnitude of current flowing through the light-emitting diode, and a high current flowing through the light-emitting diode will obtain high luminance. The light effect is reversed. Conversely, if the current flowing through the light-emitting diode is reduced, the brightness of the light-emitting diode will be relatively weakened. However, continuous supply of high current reduces the life of the light-emitting diode and wastes a lot of power. The first figure is a first embodiment of a conventional light emitting diode driving circuit. The adjustable voltage source 1〇 is transmitted through the resistor 15 for providing the light-emitting diode current ILm flowing through the light-emitting diodes 2〇, 21-25, and can be obtained by the following formula (1): • wherein Vf2〇 Vf21...Vf25 are the forward voltage drops of the light-emitting diodes 20, 21...25, respectively; R15 is the resistance value of the resistor 15. In the first embodiment, the main disadvantage of the conventional light-emitting diode driving circuit is that the forward voltage drop of the light-emitting diodes 2〇, 21 25 is not a fixed value, and is affected by mass production and temperature variation. Light-emitting diode current ILED; at the same time resistor 15 will cause power loss of the circuit. The second figure is a second embodiment of a conventional light emitting diode driving circuit. In the second embodiment, the voltage source 3 is used to provide a fixed power for the light-emitting diodes 2, 2, and .25. The light-emitting effects of the light-emitting diodes 2〇, 21··· 25 can be adjusted by the current source 35. However, in this control mode, since the voltage source ^ M294095 -30 is a high voltage, the voltage drop of the light-emitting diodes 20, 21...25 is a low voltage, so the current source 35 generates a great power loss. [New content] In view of the above, the present invention provides a switching type LED driving device for controlling the brightness of a light emitting diode. The light-emitting diode driving device of the present invention comprises an energy conversion component, the energy conversion component has a first coil coupled to the light-emitting diode in series, and the energy conversion component can be an inductor or a transformer; a switching switch is connected in series to the first coil of the LED and the energy conversion component, the switch is used to control the LED current; a first resistor is coupled in series to the switch, the first The resistor detects the current of the LED and outputs a current signal; a control circuit handle is connected to the first coil of the energy conversion component, the first resistor and the switch, and the control circuit rotates from the energy The switching component obtains a reflection and obtains a current signal from the first resistor for outputting a control signal to the switch; a diode is coupled in parallel to the energy conversion component and the LED, a light emitting diode for discharging the stored energy of the energy conversion element. * The control signal controls the switch and the LED current. When the current signal is greater than a first threshold, the switch is turned off. When the stored energy of the energy conversion element is completely discharged, and after an adjustable delay time, the switch is turned on. Moreover, the first threshold value varies according to the reflected signal of the energy conversion element. The amplitude value of the reflected signal is the forward voltage of the light-emitting diode, and the forward voltage of the light-emitting diode is related to the temperature of the light-emitting diode. Therefore, this creation is to adjust the LED current to compensate for the chr〇maticity and luminosity of the LED as a function of temperature. The above summary and the following detailed description are exemplary in order to further illustrate the scope of the patent application for this creation • M294095. The purpose and advantages of Benedict & Gan ^ Q ^ t will be explained in the following explanations and illustrations. [Embodiment] ^ The eleventh chapter of the stalk of the stalk of the light-emitting diodes of the eleventh forest. The creative switching type LED driving device uses an energy conversion element 5 第一 one of the first coils is serially coupled to the illuminating two tiles 20 to 25, the first line _ is an inductor, and the energy conversion element 50 can be For example, the switch 70 is connected in series to the light-emitting diodes 2〇25 and the first coil of the energy conversion element 50. The switch 150 is used to control the light-emitting diode current. A first resistor is connected in series to the switch 70. The first resistor turns the LED current W to output a current to the control circuit 100. When the current signal is higher than a first threshold value R of the control circuit, the switch 7G is turned off to limit the light-emitting diode current. The maximum value of the light-emitting diode current & can be known by the following formula (2): ^50

, T0N (2) In the upper formula (2), 'l5G denotes the dependence of the energy conversion element 5G; (10) denotes the on-time of the switching switch ;; VF20, VF21...VF25 are the light-emitting diodes 20, 21. respectively. The forward pressure drop of .25. The control circuit HK) is further transmitted through the resistors 57, 58 _ 转换 conversion element 5G - the second coil 2 is used to receive - reflect "VD. The _ diode is connected in parallel to the energy conversion element % 盥 light dipole 2 〇 ~ 25. When the changeover switch 70 is turned off, the energy stored on the energy conversion element 50 is increased. At the city gate _, the illuminating voltage of the polar body 20 to 25 is reflected from the first coil of the energy conversion element % to the second coil n2 of the energy surface element 50. 7 0 M294095 - Therefore, the reflected signal VD obtained by the second coil N2 of the 'energy conversion element 50' can exhibit the forward voltage of the light-emitting diodes 20 to 25. Here, the forward voltage of the light-emitting diodes 2 〇 25 is related to the temperature of the light-emitting diodes 20 to 25, and the temperature is increased when the forward voltage is decreased, whereas the temperature is decreased when the forward voltage is increased. Therefore, the reflected signal 乂〇 can exhibit a change in temperature of the light-emitting diodes 2 to 25 . Further, when the energy stored in the energy conversion element 5 is completely discharged, the reflected signal Vd is lowered to zero. Once the energy stored on the energy conversion element 5〇 has been completely discharged, the control circuit 1 detects the reflected signal Vd that has fallen to zero, and turns on the switch 7〇 after a delay time τ〇. Please refer to the fourth A and fourth B diagrams for the current waveform of the LED. The maximum value 65 of the first critical value VR limits the peak value of the waveform 6〇 of the light-emitting diode current lLm), and the maximum value 65 of the first critical value Vr determines the average value of the light-emitting diode current. Therefore, the average value of the light-emitting diode current is controlled to be a fixed value and does not change with the inductance value of the energy conversion element 5A. However, the delay time TD can be adjusted to control the amplitude value of the light-emitting diode and the light-emitting luminance of the light-emitting diodes 20 to 25. The control circuit 100 draws the light-emitting diode current Iled, and The reflected signal VD is obtained from the energy conversion element %, and at the same time, the control circuit excites the switching signal according to the reflected signal % and the LED current - to generate - control the signal 虎, the control signal % wire controls the switching action of the switch 7 Further, the light-emitting diode current ILED is adjusted. In order to maintain the chromaticity and the brightness of the light-emitting diodes 2 to 25, the light-emitting diodes 20 to 25 must take into consideration the influence of the temperature of the light-emitting diodes 20 to μ. However, it is necessary to adjust the size of the light-emitting diode current ILED with temperature. In the present creation, the first-threshold value Vr and the anti-secret number% are related to the illuminating two-reduction current and the temperature. The first-threshold value VJ varies according to the reflection. The signal Vd, the first threshold value Vr is used to compensate the color of the (8) 8 M294095 light-emitting diode 2G~25. In addition, the present invention can be used in advance for the characteristics of various LEDs. The second resistor 59 is in the control The survey is used to determine an adjustment slope. The adjustment slope indicates the relative relationship between the change of the first threshold value Vr and the change of the reflected signal %. Please refer to the fifth figure for the circuit diagram of the control circuit of the present invention. In the control circuit excitation, when the current signal Vs is greater than the __threshold value Vr, the control signal % is 剌, and the switch 270 is turned off. In the control circuit 1 ,, when the reflected signal % is smaller than - second The threshold value is such that the control signal VG is turned on by _, and the switch 70 is turned on. A first control circuit includes an idle 18 〇, an inverter 131 and a flip flop 14 〇, and the first control circuit is delayed. The signal surface and the coincidence signal vF are used to output the control signal Vg. The output of the gate 180 is lightly connected to the flip-flop 14〇, and the control signal VG# is generated from the output of the flip-flop 14G. The circuit 115 is in contact with the flip-flop 140. When the current signal vs is greater than the first threshold VR, the second control circuit 115 disables the control signal vG through the flip-flop 14. The delay circuit 200 is coupled through the inverter 131. Connected to the first input of the gate 180, delaying the electricity The road 200 outputs a delay signal having a delay time Td to the first input terminal of the gate 180 when the control signal Vg is inactive. Thus, the control signal Vg is stopped during the delay time τ〇. A sampling circuit 300 is coupled to the second coil of the energy conversion element 5 through the resistors 57 and 58. The sampling circuit 300 is configured to output a first sampling signal Vhi and a second sampling signal according to the reflected signal VD. Vm and an overvoltage signal 0VP. The overvoltage signal 0VP is transmitted to the second input terminal of the AND gate 180 for deactivating the control signal VG for overvoltage protection of the LEDs 20-25. An adjustment circuit 600 is coupled to the sampling circuit 300 and a certain current IR. The adjustment circuit 600 receives the first sampling signal Vhi, the second sampling signal Vm and the constant current Ir for adjusting the amplitude value of the first threshold 乂11. M294095' A watchdog timer 500 is coupled to the output of the flip-flop 140 and the sampling circuit 300. The watchdog timer 500 outputs a reset signal rsT according to the control signal VG, and resets the signal RST. It is sent to the sampling circuit 3〇〇 to reset the sampling circuit 3〇〇. A comparison circuit ho is coupled to the third input end of the AND gate 180, and is configured to output a uniform energy signal VF according to the reflected signal Vd being less than the second threshold value, and the enable signal Vf is coupled to the gate 180 The three-input terminal can enable the control signal Vq 0. Please refer to the sixth figure, which is a schematic circuit diagram of the delay circuit of the present invention. In the delay circuit 2 (8), a certain current source 250 is coupled to the input terminal IN of the control circuit 1 , and the control circuit 1 is coupled to one end of a resistor (not labeled) through the input terminal IN. The other end of the device can be coupled to a ground reference terminal, or the input terminal IN can be coupled to a control voltage Vcnt, which can be used to adjust the delay time 'TD, thereby controlling the brightness of the LEDs 20-25. . A voltage/current conversion circuit includes an operational amplifier 21A, a resistor, and a transistor 220, 230, 23. The voltage/current conversion circuit is generated in the transistor 231 Ji according to the voltage on the resistor minus the input terminal m. -recharging current. In the delay circuit 2, a capacitor is further coupled to the transistor 231 and the transistor 270. The transistor 27 is controlled by the control signal %. When the control signal VG# is used to turn off the transistor 270. The charging current generated on the transistor 231 immediately charges the capacitor 26, but when the transistor 27 is turned on, the voltage on the capacitor 26 is discharged through the transistor 27. - Inverting the input of 1 § 280 The terminal is lightly connected to the capacitor 26〇, and the inverter 28〇 generates the delay signal INh according to the voltage established on the capacitor 26〇. Please refer to the seventh figure, which is a schematic circuit diagram of the sampling circuit of the present invention. The pulse generator 350 is configured to generate a first pulse SMP1 and a first pulse SMP2 according to the deactivation and reflection signal % of the control signal %. With the eighth figure, the signal waveform of the creation control circuit is indicated. .M294095', wherein the first pulse SMP1 is generated after the control signal VG is deactivated by the first delay time τ〇ι. The first delay time Tdi is ensured before the first pulse SMP1 is enabled. , the reflected signal VD is stable The second pulse SMP2 is generated before the reflected signal VD drops to zero, and the second delay time τΜ ensures that the second pulse SMP2 is generated before the reflected signal vD falls to zero. The first pulse SMP1 and the first pulse The two-pulse SMP2 controls the on or off of the changeover switches 31〇, 311, respectively. The switch 310, 311 respectively samples the reflected signal VD, and respectively establishes a “^” sampling signal Vhi and a first on the capacitors 315 and 317. ^Sampling the far Vh2. Therefore, the first sampling signal VH1, the second sampling signal Vh: 2 is based on one of the first current and the second current flowing through the light emitting diodes 20 to 25, respectively The first forward voltage and the second forward voltage of the pole body 20 to 25. The sampling circuit 300 further includes a transistor 316 coupled to the capacitor 315, and the transistor 316 is controlled by a reset signal RST. The capacitor 315 is discharged. A comparison circuit 320 is coupled to the capacitor 315. The comparison circuit 320 compares the first sampling voltage Vm with a threshold voltage Vr2. When the first sampling voltage vH1 is greater than the threshold voltage Vr2, an overvoltage signal 〇VP is generated. Refer to the ninth A schematic diagram of the watchdog timer of the present invention. In the watchdog timer 500*, a reset circuit includes a capacitor 562, a transistor 56, a current source 560, an inverter 525, and resistors 531, 532. The reset circuit generates a power-on reset signal according to the activation of the power source Vcc. A timer 51 receives the control signal % through an inverter 52, and the control signal VG is deactivated by more than one. After the (time_〇ut) period, the timer 5 generates a timeout signal output. The gate 580 is coupled to the reset circuit and the timer 510, and the gate 58 receives the power-on reset signal and the time-out signal to generate the reset signal RST output. Please refer to the tenth figure for the circuit diagram of the current adjustment circuit of the creation. In the current adjustment circuit 6A, a differential circuit includes an operational amplifier 61〇, 611 and a resistor 62〇, 62, a differential circuit connection 11 M294095, a first sampling signal VH丨 and a second sampling signal Vm, and Output - voltage difference at the output of the differential circuit. The output end of the differential circuit, that is, the output end of the operational amplifier 610 is connected to the input terminal of an operational amplifier 615. The operational amplifier 615, the transistors 630 to 635, and a resistor are divided into another voltage/current conversion circuit. The further circuit generates currents 1633, 1635 based on the resistance values of the wire and the second resistor 59. Resistor 650 is coupled to constant current IR, current 1633, and & to produce a first threshold VR. The value of the first threshold value ^ can be effectively adjusted by adjusting the current value of the current ^^.

The first sampling signal VH1# second sampling signal VH2 is obtained by the following formulas (3), (4):

Vm

R 58 X- 'T2 xVl (3) In the plane a (3), (4), 'Ντ1, Ντ2 respectively represent the line-to-number of the first coil & and the second coil N2; respectively, R58 is the resistor 57 The % resistance values ^, % are the first forward voltage and the second forward voltage, respectively. The forward direction voltage VI and the second forward voltage V2 correspond to the first hair diode current and the second hair body current 12, the first light emitting current, and the second light emitting diode current 12 They are obtained by the following formulas (5) and (6): (5) (6) — IoXe"丨ντ

72 ^1〇XeVVVT in formula (5),

In <1 (6), VT can be obtained by the formula (7): (7) In the formula (7), TemP can be obtained by the formula (8): 12 M294095

Temp = i,nzI2 (§) in

UJ In the above equations (5) to (8), 'k is a Boltzmann's s c〇nstant; q is the amount of electron charge; and Temp is the absolute temperature. In summary, the light-emitting diode driving device can accurately obtain the temperature of the light-emitting diodes 20 to 25 by using the reflected signal, and adjust the current flowing through the light-emitting diodes 2 to 25 by using the temperature. To compensate for the chromaticity and lumen of the light-emitting diodes 20 to 25. 'However, as described above, it is only a detailed description and drawing of the specific embodiment of one of the best creations of the present invention. Anyone familiar with the art can easily think of changes or repairs in the field of the creation. Covered in the following patent scope of this case.

13 • M294095 . [Simple Description of the Drawings] The first figure is a first embodiment of a conventional light-emitting diode control circuit; the second figure is a second embodiment of a conventional light-emitting diode control circuit; The circuit diagram of the switching type LED driving device of the present invention; the fourth A picture and the fourth B picture are schematic diagrams of the current waveform flowing through the light emitting diode; the fifth picture is a circuit diagram of the control circuit of the creation The sixth diagram is a circuit diagram of the delay circuit of the creation; • The seventh diagram is a circuit diagram of the sampling circuit of the creation; the eighth diagram is a schematic diagram of the signal waveform of the creation control circuit; Schematic diagram of the circuit; and * * The tenth figure is the circuit diagram of the current adjustment circuit of the creation. [Main component symbol description] Convention: LED (20, 21...25) Voltage source 10 Resistor 15 LED current Led Voltage source 30 Current source 35 Creation: Energy conversion component 50 First coil Fandi Two coils n2 Light-emitting diodes 20~25 Switching switch 70 Light-emitting diode current Ii^ed First resistor 75 Current signal Vs Control signal VG Reflected signal VD Control circuit 100 Resistor 57, 58 14 4 M294095 Diode 55 Power supply Vcc control voltage VcNT current Ieed waveform 60 maximum value of the first threshold VR 65 ^ 一 threshold value Vjh and gate 180 inverter 131 flip-flop 140 delay signal INH enable signal Vp second circuit 115 delay circuit 200 first Sample signal Vm second sample signal Vh2 over voltage signal OVP adjustment circuit 600 constant current Ir_ watchdog timer 500 reset signal RST comparison circuit 110 enable signal VF first threshold VR sampling circuit 300 constant current source 250 operation amplifier 210 resistor 205 second resistor 59 transistor 220, 230, 23 270 capacitor 260 inverter 280 pulse generator 350 first pulse SMP1 second pulse SMP2 first delay TD1 延迟2 delay time Td2 switch 310, 311 capacitor 315, 317 transistor 316 comparison circuit 320 capacitor 562 transistor 561 current source 560 inverter 525 15 / 15 M294095 resistor 53 532 inverter 520 operation amplifier 610, 611 Operational Amplifier 615 Current 633, 635 Timer 510 and Gate 580 Resistor 620, 621 Transistor 630~635 Resistor 650

16 8

Claims (1)

, M294095. IX. Patent application scope: 1. A light-emitting diode driving device for driving a light-emitting diode, comprising: an inductor having a first coil and a second coil, the first a coil is coupled in series to the light emitting diode; a switch is coupled in series to the light emitting diode and the first coil, and the switching relationship controls a light emitting diode current, the light emitting diode current system a current flowing through the light-emitting diode; a first resistor coupled in series to the switch, the first resistor detecting the LED current, # and outputting a current signal; a control circuit coupled In the second coil, the first resistor and the switch, the control circuit obtains a -reflection signal from the inductor and obtains the current signal from the first resistor, and outputs a control signal to the switch; - 2 minus 'and _ connected to the electricity « and the return light triode, the Wei luminescent diode discharges the stored energy of the inductor; and a second resistor coupled to the control circuit; The The control signal controls the switch and the LED current. When the current signal is greater than the -th threshold, the switch is turned off; t the stored energy of the inductor is completely discharged, and after an adjustable delay time, The switch is turned on. 2. The hair-emitting diode driving device of claim 1, wherein the first critical value follows the reflection signal. 3. The method of claim 1, wherein the control circuit comprises: a delay circuit for outputting a delay 汛旒 when the control signal is turned off, the delay signal having 17 M294095 - the adjustable delay time; a comparison circuit that outputs a uniform energy signal when the reflected signal is less than a second threshold; a first control circuit receives the delayed signal and the enable signal, and enables the a second control circuit that disables the control signal when the current signal is greater than the first threshold; and a sampling circuit coupled to the second coil of the inductor, the sampling circuit is followed The reflected signal, and outputs a first sampled signal and a second sampled signal. The illuminating diode driving device of claim 3, wherein the first sampling signal and the second sampling signal are based on a first illuminating diode current and a second The light-emitting diode currents respectively indicate a first forward voltage of the light-emitting diode and a second forward voltage of the light-emitting diode. The light-emitting diode driving device according to claim 1, wherein the inductor is a transformer. The invention relates to a light-emitting diode driving device for driving a light-emitting diode, which comprises: a January b-switching component, which is connected in series to the light-emitting diode and outputs a reflected signal; a switch, the string is connected to the light emitting diode and the energy conversion component, the switch controls a light emitting diode current, and the light emitting diode current is a current flowing through the light emitting diode, and a control circuit Subtracting the energy conversion component and the switch, the control circuit obtains the reflected signal and the LED current, and outputs a control signal, and a diode, which is paralleled to the energy conversion component and the light The diode discharges the stored energy of the energy conversion element through the light emitting diode; wherein the control signal outputted by the control circuit controls the switch and the light emitting diode 18 M294095 - when When the current signal is greater than a first threshold, the switch is turned off. The illuminating diode driving device of claim 6, wherein the first critical value follows the reflected signal. The light-emitting diode driving device of claim 6, further comprising: a first resistor coupled in series to the switch, the first resistor detecting the light-emitting diode And outputting a current signal to the control circuit; and φ a second resistor coupled to the control circuit. The illuminating diode driving device of claim 6, wherein the control circuit comprises: a delay circuit that outputs a delay signal when the control signal is turned off, the delay signal Having an adjustable delay time; a comparison circuit for outputting a uniform energy signal when the reflected signal is less than a second threshold; a first control circuit receiving the delayed signal and the enable signal, and enabling The control signal is: a second control circuit that disables the control signal when the current signal is greater than the first threshold; and a sampling circuit coupled to the energy conversion component, the sampling circuit follows the reflection And outputting a first sampled signal and a second sampled signal. The illuminating diode driving device of claim 9, wherein the first sampling signal and the sampling signal are based on a first LED current and a second LED The polar body current represents a first forward voltage of the light emitting diode and a second forward voltage of the light emitting diode, respectively. Cs)