TWM400069U - Light-emitting diode (LED) driving circuit with dimming sequence control - Google Patents

Description

M400069 V. New description: [New technology field] [(五)〇1] This creation is about a kind of light-emitting diode (Light-Emitting)

Diode (LED) drive circuit, and in particular to an LED drive circuit with dimming timing control [Prior Art] [0002] FIG. 1 is a circuit diagram of a conventional LED drive circuit. Please refer to FIG. 1 'LED driving circuit 1 for driving LED lamp 4, wherein LED string 4 has input 41 and output 42 'LED string 4 includes a plurality of LEDs DL1 DLDL connected in series with the input Between end 41 and output 42, η is an integer greater than one. LED driver circuit lgfell 驰 l^fffeack) converter•V··:··. - . Ά,·':./·Bu V 〆u, feedback circuit I2 and dimmer switch %〆[0003] flyback The converter 11 includes a transformer Τ1, a transistor Q1 as a switch, a rectifying diode D1, and a capacitor C1. The transformer Τ1 is provided with a primary coil Νρ on its primary side and a secondary winding Ns on its secondary side. The flyback converter 11 is configured to control the switching of the transistor Q1 according to the control signal CTRL in the form of Pulse-Width Modulation (PMW), and convert the DC input voltage V iη into a DC output voltage Vout. To the input 41 of the LED string 4 to provide the required operating voltage of the LED string 4. [0004] The feedback circuit 12 includes an auxiliary winding Na, a rectifying diode D2, a capacitor C2, a resistor R1, and a PWM controller U1 provided on the primary side of the transformer T1. The feedback circuit 12 is configured to pass the induced current of the auxiliary coil Na (which is related to the current of the coil Νρ and the secondary coil Ns) through the rectifying diode D2, the capacitance meter number A0101, page 4/22 pages [ 0005] The rectifier C2 and the resistor R1 are rectified and filtered to generate a feedback signal fb to be output to the feedback terminal of the PWM controller U1, and the PWM controller U1 further controls the switching of the transistor Q1 according to the feedback signal output control signal CTRL. The output voltage Vout provided by the chirp converter 11 is stabilized. The dimmer switch 13 includes a transistor Q2 that is used as a switch. The first end of the dimming % off 13 (ie, the extreme end of the transistor Q2) consumes the output 42 of the LED string 4, and the second end of the dimmer switch 13 (ie, the source terminal of the transistor Q2) is grounded, dimming The control terminal of the switch 13 (i.e., the gate terminal of the transistor Q2) receives the dimming signal DIM1 in the form of a low frequency PWM. Each switching period T of the dimming signal DIM1 includes an on period Ton and a off period Toff, and the duty cycle (duty) of the dimming signal DIM1 is the ratio of the period Ton to the switching period T, wherein the switching period Sinking! Wanted: Designed to be solid. 3⁄4 unchanged. [0006] During the on period Ton, the dimming switch 13 is turned on, the LED string 4 has a current passing through and is illuminated (bright) ^ in the off period To ff, the dimming switch 13 is worn, and the LED string 4 has no current passing through Luminous (dark). By properly designing the switching period T to take advantage of the human eye to temporarily hold the phenomenon, let the eyes not feel it. > * To the LED light string 4, light up the darkness, only the house: feel a certain brightness, this brightness It is related to the ratio of light to dark time. Therefore, the brightness of the LED string 4 can be changed by the human eye by changing the duty cycle of the dimming signal DIM1. This dimming mode is called PWM dimming or burst mode dimming. [0007] In the conventional LED driving circuit 1, for example, when the dimming switch 13 is controlled by the dimming signal DIM1, the output current of the flyback converter 11 becomes zero, and the feedback circuit 12 cannot pass the auxiliary coil Na. Inductive current is generated to minimize the feedback signal FB, so that the duty cycle of the control signal form number A0101 outputted by the PWM controller U1 is increased, thereby causing the transmission & voltage Vout to rise rapidly. Until the PWM controller U1 detects that the output voltage Vout is too high and activates the overvoltage protection or the dimming switch 13 is controlled by the dimming signal DIΜ1, the output voltage Vout starts to drop, so the output voltage Vout has an overshoot (overshoot) The phenomenon occurs, which shortens the service life of the circuit components and the LED string 4. [New content] [0008] In view of this, the purpose of this creation is to propose an LED driving circuit with dimming timing control, which can eliminate the overshoot of output voltage and current during PWM dimming. The present invention proposes a dimming and stimulating circuit for receiving a dimming signal with a low frequency pwm form and a period of each conduction period and a cutoff period to drive the LED string to emit light during conduction and during the cutting period. Does not shine. The LED drive circuit with dimming timing control includes a switching power converter, a PWM controller, a dimmer switch, and a dimming timing control circuit. The switched power converter is coupled to the input of the LED string for providing an output voltage to the input of the LED string during the on period according to a control signal having a high frequency PWM form and not providing an output voltage during the off period. The PWM controller is coupled to the switched power converter for outputting a control signal during the on period and stopping the output of the control signal during the off period. The first end of the dimmer switch is coupled to the output end of the LED string, and the second end of the dimming switch is grounded. The dimming timing control circuit is coupled to the control end of the dimming switch and the PWM controller for receiving the dimming signal, and controlling the PWM controller to start outputting the control signal after the dimming switch is turned on first during the on-period, and entering During the cut-off period, the PW Μ controller stops outputting the control signal and then the dimmer switch is opened. The form number Α 0101 δ page / total 22 pages is cut off. In an embodiment of the present invention, the dimmer switch is turned "on" when its control terminal receives a logic and level signal and is turned off when its control terminal receives a logic low level signal. The dimming timing control circuit includes a time delay circuit, a switch, and an isolation circuit. The input of the time delay circuit receives the dimming signal. The first end of the switch is coupled to the power supply voltage and the control end of the dimming switch, the second end of the switch is grounded, and the control end of the switch is coupled to the output end of the time delay circuit. The switch is turned on when the control terminal receives the logic high level signal. And it is turned off when the control terminal receives the logic low level signal. The input end of the isolation circuit receives the dimming signal, and the output end of the isolation circuit is coupled to the feedback end of the pWM controller. In an embodiment of the present invention, the delay circuit 4 includes a first resistor, a second resistor, and a capacitor. The i-th resistor: the first end of the first resistor is coupled to the input end of the time delay circuit, and the second end of the first resistor is coupled to the output end of the time delay circuit. The first end of the second resistor is coupled to the second end of the first resistor, and the second resistor is grounded. The first end of the capacitor is coupled to the second end of the first resistor, and the second end of the capacitor is grounded. % In an embodiment of the present invention, the "on" switch includes an NPN bipolar junction transistor or an N-channel field effect transistor. In an embodiment of the present invention, the isolation circuit includes an optical coupler including a light-emitting element disposed at an input end of the isolation circuit and a light-detecting element disposed at an output end of the isolation circuit, wherein the light-emitting element includes a light-emitting diode, The light detecting element includes a photoelectric crystal. In another embodiment, the isolation circuit includes an isolation transformer including a primary coil disposed at an input of the isolation circuit and a secondary coil disposed at an output of the isolation circuit. Page 7 of 22 Form No. A0101 M400069 This design uses the dimming timing control circuit to control the dimming switch to turn on and the PWM controller starts to output the control signal when it enters the conduction period, and controls the PWM control when entering the off period. After the output control signal is stopped, the dimming switch starts to cut off, which can eliminate the overshoot of the output voltage and current during PWM dimming, and avoid shortening the service life of circuit components and LED strings. The above and other objects, features, and advantages of the present invention will become more apparent from the description of the appended claims. [Embodiment] FIG. 2 is a circuit diagram of an embodiment of an LED driving circuit of the present invention. Referring to FIG. 2, the LED driving circuit is in the form of a dimming signal DIM2 with a conducting period 涧Toff to drive the LED string to emit light during the on period Ton and not to emit light during the off period to realize PWM dimming. . In the present embodiment, the LED light string is exemplified by the LED light string 4 shown in FIG. 1, but is not limited thereto. [0010] The LED driving circuit 2 includes a switching power converter, a feedback circuit, a dimming switch, and a dimming timing control circuit, wherein the feedback circuit includes a PWM controller. In the present embodiment, the switching power converter is exemplified by the flyback converter 11 shown in FIG. 1, but is not limited thereto. For example, it can be changed into a buck, a boost, a lift. Switching power converters for bulk-boost, forward, half-bridge or full-bridge converters. The feedback circuit is exemplified by the feedback circuit 12 of the primary side control shown in Fig. 1, but is not limited thereto. For example, it can be changed to a feedback circuit using a secondary side error amplifying circuit and an optical coupler. The dimmer switch is exemplified by the dimmer switch 13 shown in Fig. 1, but is not limited thereto. Dimming Timing Control Circuit Form No. A0101 Page 8 of 22 [0011] The circuit is exemplified by the dimming timing control circuit 24 shown in FIG. 2, but is not limited thereto. The flyback converter 11 and the feedback circuit 12 are not limited thereto. The configuration and coupling relationship of the dimming switch 〖3 will not be described here, but the control end of the dimming switch 13 does not directly receive the dimming signal as shown in FIG. 1, but is changed to the dimming timing control. The circuit 24 receives the dimming signal DIM2. [0012] The dimming timing control circuit 24 is coupled to the control end of the dimming switch 13 and the feedback end of the PWM controller U1 of the feedback circuit 12. The dimming timing control circuit 24 is configured to receive the dimming signal DIM2, and control the dimming switch 13 to be turned on after the in-conduction period τ〇n is turned on, and then the output control CTRL is turned on to enable the flyback converter nrflW to supply money| The voltage ^ut, when entering the off-period Toff, the PWM control wheel outputs a control signal to CTRL, so that the flyback converter U stops providing the output voltage v〇ut, and then the dimming switch 13 is turned on. Since the seasoning sequence control (four) way (10) turns on the dimming switch 13 to form a path for the wheel of the LED string 4 to be grounded, and then causes the flyback converter U to start supplying the output voltage v〇ut, the output current There is no overshoot phenomenon. H. Since the dimming timing control circuit 24 first causes the flyback converter n to stop providing the wheeling voltage, the dimming switch 13 is turned off and the output terminal 42 of the LED string 4 is formed to the ground. The circuit is broken, so there is no overshoot in the output battery Vout. 3 is a circuit diagram of an embodiment of a dimming timing control circuit of the LED driving circuit of the present invention. Referring to FIG. 3, the dimming timing control circuit 24 includes an input terminal 311 including a time delay circuit 31, a _32 and a _ circuit ^ time delay circuit 3 接收, receives the dimming signal _2, and delays the dimming signal IHM2 for a period of time. From its output (1) to the dimmer switch

Form No. A010I Page 9 of 22 M400069 1 3 Control Terminal u In the present embodiment, the time delay circuit 31 includes a first resistor Rb1, a second resistor Rb2, and a capacitor C3. The first end of the first resistor Rb1 is coupled to the input end 311 of the time delay circuit 31, and the second end of the first resistor Rb1 is coupled to the output end 312 of the time delay circuit 31. The first end of the second resistor Rb2 is coupled to the second end of the first resistor Rb2, and the second end of the second resistor Rb2 is grounded. The first end of the capacitor C3 is coupled to the second end of the first resistor Rb1, and the second end of the capacitor C3 is grounded. [0014] If the dimmer switch 13 is designed to be turned off when the control terminal receives the logic high level signal and is turned off when the control terminal receives the logic low level signal, and the dimming signal DIM2 adopts a negative logic design, the switch 32 The design decision to use the logic high-level signal receiving terminal to receive the logic low-level signal at its control end is determined by the NPN dual-carrier junction transistor Q3 or the Ν channel field effect transistor. The first end 321 of the switch 32 (such as the collector terminal of the transistor Q3) is coupled to the supply voltage Vccl (such as 5V) as a logic high level signal and the control end of the dimming switch 13 through the resistor Rcl, and the second end of the switch 32. The terminal 322 (e.g., the emitter terminal of the transistor Q3) is coupled to ground as a logic low level signal, and the control terminal 323 of the switch 32 (e.g., the base terminal of the transistor Q3) is coupled to the output terminal 312 of the time delay circuit 31. The input terminal 331 of the isolation circuit 33 receives the dimming signal DIM2, and the output terminal 332 of the isolation circuit 33 is coupled to the feedback terminal of the PWM controller U1. In the present embodiment, the isolation circuit 33 includes a photocoupler U2 and resistors Rc2 and Rc3. The photocoupler U2 includes a light-emitting element (e.g., light-emitting diode IR) disposed at the input end 331 of the isolation circuit 33 and a light-detecting element (e.g., photo-electric crystal PT) disposed at the output end 332 of the isolation circuit 33. [0016] When entering the on period Ton, the dimming signal DIM2 is at a logic low level. Form No. A0101 Page 10 of 22 M400069

[0017]

When the form number A0101 U 0, the capacitor of the delay circuit 31 is delayed by discharge for a period of (four) time to control φ open 'loading' the control terminal of the money dimming switch ^ 3 receives the logic high level provided by the supply voltage Vecl The signal is turned on. In addition, the 'dimming signal _ logic low level signal can not provide illumination

The required operating voltage of the diode IR, the light-emitting diode ir does not emit light, so that the photoelectric crystal PT is not blocked by the detection of light, so that the isolation circuit outputs no signal 332 to the PWM controller w. Just controller III has to customize from the previous period during the cut-off period, f f stop output control signal CTRL becomes normal operation and output control signal CTRL takes a long time, thus realizing the dimmer switch when entering the on-time Ton 13 After the first PWM controller υ 1 starts to input, the electric control signal Ctrl. >· During the period of entering the wear period Toff蛘丨:, Saiguang sets kDIM2 to logic high level • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The time control switch 3 2 is turned on, and then the control end of the dimming switch 13 is turned off by receiving the logic low level signal provided by the ground. In addition, the dimming signal DIM2 is a logic high level signal and can be provided through the resistor rc2. The required operating voltage of the LED of the light-emitting diode, the light-emitting diode IR will emit light, so that the photoelectric crystal PT is turned on by detecting the light, so that the power supply voltage Vcc2 (such as 16V) generates a large current signal from the isolation circuit 33 through the resistor Rc3. The output terminal 332 outputs to the feedback terminal of the PWM controller U1, causing the PWM controller U1 to immediately stop outputting the control signal CTRL due to the excessive feedback signal FB, thus realizing the PWM controller ϋ 1 before entering the off period To ff The dimming switch 13 is turned off after the output control signal CTRL is stopped. Fig. 4 is a circuit diagram showing another embodiment of the dimming timing control circuit of the LED driving circuit of the present invention. Please refer to FIG. 4 'dimming timing control circuit page 11 / 22 pages [0018] [0019] [0020] [0024] [0024] [0025] 24 only FIG. 3 The photocoupler U2 in the non-dimming timing control circuit 24 is replaced by an isolation transformer T2. The isolation transformer T2 includes a primary winding Νρ' provided at the input terminal 431 of the isolation circuit 43, and a secondary winding Ns' provided at the output terminal 432 of the isolation circuit 43. In summary, the present invention uses the dimming timing control circuit 24, 24, or 24" to control the dimming switch 13 to turn on after the conduction to the conduction period τ〇n, the PWM controller υι starts to output the control signal CTRL, and enters During the off period Tof f, the PWM controller ui stops outputting the control signal CTRL and the dimming switch 13 starts to cut off, which can eliminate the overshoot phenomenon of the output voltage and current during PWM dimming. 'To avoid shortening the service life of the circuit components and the LED string 4 . Although this creation has been used in a better way, it is not intended to limit the creation of 'any kind of money that is within the spirit and scope of the creation'. When it is possible to make some changes and decorations, the scope of protection of this creation is attached. The scope defined in the scope of application for patent application shall prevail. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit diagram of a conventional LED driving circuit. 2 is a circuit diagram of an embodiment of the LED driving circuit of the present invention. Fig. 3 is a circuit diagram showing an embodiment of a dimming timing control circuit of the LED driving circuit of the present invention. Fig. 4 is a circuit diagram showing another embodiment of the dimming timing control circuit of the LED driving circuit of the present invention. [Description of main component symbols] 1, 2: LED drive circuit Form No. A0101 Page 12 of 22 [0026] M400069 [0028] [0029] [0032] [0032]

[0038] [0038] [0038] [0038]

[0044] [0044] [0044] 11: flyback converter 12: feedback circuit 1 3: dimmer switch .24, 24', 24 ": dimming timing control circuit 31: Time delay circuit 311: Input terminal 312 of the time delay circuit: Output terminal 32 of the time delay circuit: Switch 321: The first end of the switch is:: 322: The second end of the switch: ': 323: Control of the switch Terminals 33, 43: isolation circuits 331, 431: input of the isolation circuit $ C - .i I .... 332, 432: output of the isolation circuit 4: LED string 41: input 42 of the LED string: LED string Outputs C1 to C3: Capacitors D1, D2: Rectifier Diode Form No. A0101 Page 13 of 22 M400069 [0045] DL1-DL η: Light Emitting Diode [0046] Q1~ Q3: Transistor [0047] R1, Rcl~Rc3: Resistor [0048] Rbl: First Resistor [0049] Rb2: Second Resistor [0050] ΤΙ : Transformer [0051] Na : Auxiliary Coil of Transformer [0052] Np : Primary of Transformer Coil [0053] Ns : secondary winding of transformer; [0054] T2 : 2: · Isolation transformer [0055] Np, : primary winding of isolation transformer [ 0056] Ns, : Secondary winding of isolation transformer 溷 [0057] U1 : PWM controller [0058] U2 : Light absorbing device [0059] IR : Light-emitting diode of optical coupler [0060] PT : Optical coupler Photoelectric crystal [0061] Vccl, Vcc2: supply voltage [0062] Vin: input voltage [0063] Vout: output voltage

Form No. A0101 Page 14 of 22 M400069 [0064] CTRL: Control Signal [0065] DIM1, DIM2: Dimming Signal [0066] T: Switching Period of Dimming Signal [0067] Ton: Conduction Period of Dimming Signal [0068] Toff: OFF period of the dimming signal [0069] FB: feedback signal

Form No. A0101 Page 15 of 22

Claims (1)

Sixth, the scope of application for patents: 1. A light-emitting diode driving circuit with dimming timing control for receiving a dimming signal with a low-frequency pulse width modulation and each switching period including an on period and an off period The light-emitting diode driving circuit with the dimming timing control includes: a switching power converter coupled to the light-emitting diode for driving a light-emitting diode string to emit light during the conducting period and not emitting light during the turning-off period An input end of the polar body light string, configured to provide an output voltage to the input end of the light emitting diode string according to a control signal having a high frequency pulse width modulation during the conducting period, and not provided during the off period The output voltage; a pulse width modulation controller coupled to the bad converter for outputting the control signal during the conduction period, and outputting the control signal intermittently; % applying a dimmer switch 'the dimming switch' One end is coupled to the output end of the LED string, the second end of the dimmer switch is grounded; and a dimming timing control circuit is coupled to the control end of the dimmer switch and the pulse width modulation control And receiving the dimming signal, and controlling the pulse width modulation controller to start outputting the delta control signal after the dimming switch is turned on first when entering the conducting period, and the pulse width is obtained when entering the off period The dimming controller first stops outputting the control signal, and the dimmer switch starts to be loaded. 2 · The dimming diode driving circuit with dimming timing control as described in claim 1 of the patent application The switch is turned on when its control terminal receives the logic high level signal and is turned off when the control terminal receives the logic low level signal. The dimming timing control circuit includes: a time delay circuit, the input end of the time delay circuit receives the tone光信099220559 Form No. 1010101 Page 16 of 22 Page 0992063388-0 M400069; - Switch's first-end city __ supply voltage and the control end of the dimmer switch, the second end of the switch is grounded, the switch The control terminal consumes the output of the time delay circuit 'the switch is turned on when its control terminal is purely logic high level signal and is turned off when its control terminal receives the logic low level signal; An isolation circuit, the input end of the isolation circuit receives the dimming signal, and the output end of the isolation circuit is coupled to the feedback end of the pulse width modulation controller. The illuminating diode driving circuit with dimming timing control according to claim 2, wherein the time delay circuit comprises: a first resistor, wherein the first end of the first resistor λ is connected to the Time delay ....., τ. The input end of the circuit, the first resistor 吟 second Sister is connected to the output of the inter-peak delay circuit; a second resistor, the first of the second resistor The end is coupled to the second end of the first resistor, the second end of the second resistor is grounded; and a capacitor, the first end of the capacitor is consuming the second end of the first resistor The second end of the capacitor is grounded. The illuminating diode driving circuit with dimming timing control according to claim 2, wherein the switch comprises a ΝρΝ double carrier junction transistor. The illuminating diode driving circuit with dimming timing control according to claim 2, wherein the switch comprises a Ν channel field effect transistor. The illuminating diode driving circuit with dimming timing control according to claim 2, wherein the isolating circuit comprises an optical coupler, and the optical coupler comprises a light emitting element not at the input end of the 泫 isolating circuit. And a light detecting element disposed at an output end of the isolation circuit. 099220559. A light-emitting diode with a dimming timing control as described in claim 6 of the scope of claim 2, 0992063388-0, a form number Α0101, a seventh page, a total of 22 pages of a M400069 body drive circuit, wherein the light-emitting element comprises a light-emitting diode . 8. The light-emitting diode driving circuit with dimming timing control according to claim 6, wherein the light detecting element comprises a photoelectric crystal. 9. The LED driving circuit with dimming timing control according to claim 2, wherein the isolation circuit comprises an isolation transformer, the isolation transformer comprising a primary coil disposed at an input end of the isolation circuit A primary coil disposed at the output of the isolation circuit. 099220559 Form No. A0101 Page 18 of 22 0992063388-0