TWI222336B - Low noise light source operation circuit and method - Google Patents

Abstract

A low noise light source operation circuit and method comprises synchronous pulse width modulator, zero point signal picked circuit, light source driving circuit, light source and feedback signal picked circuit. Zero point signal picked circuit picks the zero points of light source driving circuit, and send the synchronous control signal with the output according these zero points. Synchronous pulse width modulator controls the duty cycle of the duty cycle signal according synchronous control pulse and feedback signal, and send the duty cycle signal to light source driving circuit.

Description

^ 2336 V. Description of the invention ^ f-’Avoid-§——Technical double one ^ and especially ^, it is about a light source operation circuit and its operation method. It is about a low noise light source operation circuit and its operation method. (IiK3iquid Crystal Display) in the early 1970s was used in electronic computers and electronic clocks. Later, due to how much power was spent discovering and driving the technology, it has the advantages of low power consumption, low-profile, lightweight, and low-voltage driving. It has now been widely used in video, mobile phones, and notebook computers. The LCD display should rely on a light source to transmit uniformly through the backlight, and then the distortion of the molecules in the past makes it possible to display the daylight on the LCD panel. Therefore, the quality of the board light source has become a very important key. At present, the backlight board light sources that have been compared include cold-cathode fluorescent tubes and backlight board light sources such as light-emitting diodes. Normally, when the light source of a backlight board is operated stably, the power supply required is a sine wave in a certain working frequency range and does not contain DC components. The stable operation of the lamp is almost constant, and the brightness of the lamp is determined by passing the lamp. In the known technology, the driving current waveform of the light source of the backlight will also be affected, and the brightness of the light source, and the driving current close to the sine wave has a higher luminous efficiency. However, the waveform with a high content of harmonic components is because it falls in the operating frequency band: out of: so: the luminous efficiency also causes the overall luminous efficiency to be low. At the same time, these harmonics are also detrimental to the life of the light source. influences. Please refer to Section 1 ®, which shows the conventional backlight light source circuit block in green

1222336 _ case number 92123867_ year month day _ amendment __ 5. Description of the invention (2) Figure. A conventional backlight board light source circuit includes a pulse width modulator (PWM) 110, a backlight board light source driving circuit 120, a backlight board light source 130, and a feedback signal detection circuit 14o. The PWM 1 10 series is coupled to the backlight board driving circuit 120, and includes a reference voltage generator internally, and its surface is connected to the triangle wave generator 112. The positive terminal of the error amplifier 113 is coupled to the reference voltage generator 111, and the negative input terminal is coupled to the output of the feedback signal detection circuit 140. The negative terminal pin of the comparator 114 is connected to the output terminal of the error amplifier 113, and its positive terminal pin is coupled to the triangle wave generator 112 ', and its output terminal is coupled to the backlight board driving circuit 120. The transistor switch circuit 21 in the back / board driving circuit 120 is coupled to the output terminal of the comparator 14 and the other end is coupled to the oscillator circuit 122. The transistor shutdown circuit 121 is also connected to an external DC power source VDD. The oscillator circuit 122 L is coupled to the input terminal of the protective capacitor 1 2 3 to the edge of the backlight board 130, and the output terminal of the backlight source 130 is coupled to the feedback signal detection circuit 14o. According to the above-mentioned conventional technology, the AC output of the oscillator 1 2 2 is independently independent of the switching frequency of the on-off switching of the transistor-off circuit 1 2 1, and may cause the phenomenon of frequency difference interference of the entire backlight module. Due to \, the optimal operating frequency of the source will usually be between one operating frequency band, and the driving current harmonics operating outside the operating frequency range will have poor luminous efficiency ^, and it will generate extra heat to damage the life of the light source. Severe very serious light source flicker, affecting user's eye health. Will make the invention. In view of this, the object of the present invention is to provide a low noise source.

1222336 Amendment No. 921238B7 Five. Description of the invention (3) Operating circuit and method of operation. The off frequency and the output frequency of the oscillator can make the switching of the transistor switching circuit interfere. And because of the whole; the life is broken and the visual noise is improved. The first noise is low, which makes the stability of the system to achieve the above purpose. According to the present invention, the light source operating circuit includes an electric drive circuit for operating a low noise light source, a zero signal detection circuit, a light source output circuit. End-coupled: device. Among them, the output of the parent galvanic current m drives the light source. The second person t loses the input and is used to generate the source control signal to the source of the two-phase electric signal. And send this duty cycle signal to the light source driving circuit. In the first embodiment of the press-production ii invention, the synchronous pulse width modulator includes a reference electric comparator stepped triangular wave generator, a reverse error integrator, and the first US second middle school. The synchronous triangle wave generator is connected to the aforementioned zero signal detection circuit, and generates a synchronous triangle wave signal according to the synchronous control pulse. The input of the reverse error integrator is respectively coupled to the aforementioned feedback signal detection circuit and the reference voltage generator. , After comparing the feedback signal from the feedback signal detection circuit ^ with the reference voltage generated by the reference voltage generator, you will get 11888twfl.ptc Page 8 122233 6 _Case No. 92123867_ Year, Month, and Day Amendment__ 5. Description of the Invention (4) The average error of the feedback signal is sent to the first comparator. The first comparator then compares the synchronous triangle wave signal with the average error of the feedback signal , The work cycle signal will be sent to the light source drive circuit. The work cycle signal is an integer multiple of the operating frequency of the light source, and the size of the work cycle signal period will change with the average error of the light source current. The duty cycle of the pulse width modulator is reduced, the average error is smaller than the reference voltage, and the duty cycle of the synchronous pulse width modulator is increased. In the first embodiment of the present invention, the zero signal detection circuit includes a hysteresis comparator and a buffer. Device, rising edge detection circuit, falling edge detection circuit and OR gate. The hysteresis comparator has a first input terminal and a second input terminal. The first input terminal is coupled to a first resistor and a second resistor. The second resistor is connected in parallel, the other end of the first resistor is coupled to the input end of the light source to receive the AC voltage signal of the light source, and the other end of the second resistor is coupled to the second output. Terminal, after the AC voltage signal is divided by the first resistor and the second resistor, a sine wave signal is obtained and sent to the first input terminal. The second input terminal is coupled to the output terminal of the buffer, and the input terminal of the buffer receives the reference After the voltage and reference voltage pass through the buffer, the DC reference potential is obtained and sent to the second input terminal of the hysteresis comparator. The sine wave signal and the DC reference potential pass through the hysteresis comparator to obtain the pulse wave signal, and then pass the rising edge detection. Synchronous control pulses are obtained at the exit loop, falling edge detection loop, and OR gate. In the first embodiment of the present invention, the synchronous triangle wave generator includes a second comparator, a third comparator, an invertor gate, and a flip-flop. One input terminal of the second comparator receives the triangular wave peak reference potential, the other terminal is coupled to one of the input terminals of the third comparator, and the other input terminal of the third comparator is connected to

11888twf1.ptc Page 9 Month Said-^^ 2123867 V. Description of the invention (5) Reference to the dihedral wave trough reference gate, anti-or gate and other-wheel. The output of the first comparator is switched to the invertor output and the third comparator 1 = receives the synchronous control pulse, and the number of the inverse OR gate and the output of the third comparator are connected to the invertor, the The falling edge of the output signal is synchronously controlled / the output signal passes through the flip-flop, so that in the embodiment of the triangular wave, the synchronous | balanced scale 1 generates a synchronous triangular wave. Made in this. An angular wave generator operates at twice the frequency of the light source in another circuit of the present invention, the light source drives Thunder II. The present invention describes a circuit for detecting the zero point signal in addition to the light source and the feedback signal detector. And synchronous pulse width modulation control pulse, and transparently ^: stylized phase-locked loop, its input terminal receives the synchronous input signal, and generates the program control input sent by your 控制 type control input device to the synchronous pulse width modulation = = the synchronous signal of vibration , Synchronous Diagonal Wave Generator in Tailu Riri Beta Dual Device. It is used for Do, 75 Ρ 1. One purpose is to provide a low-noise light source operation method. A suitable triangle triangle circuit includes a driving circuit triangle operation. I: Method with the same package: =: production = dagger = for electrical capture. The rectification is converted into a feedback signal. Test, Ray = get the average error of the synchronization signal and compare with the same = diagonal wave, get the duty cycle signal. Finally, a stable AC voltage is generated according to the first cycle number and output to the light. In the preferred embodiment of the present invention, the method of generating a synchronous triangle wave is as follows: first: detecting the resonance frequency of the light source and the driving circuit to zero = generating a synchronization control pulse. Mix the synchronization control pulse with the triangle wave. most

11888twfl.ptc Page 10 1222336 _Case No. 92123867_ Year Modified_ V. Description of the invention (6) After the falling edge of the triangle wave is synchronized by the synchronization control pulse, a synchronous triangle wave is generated. In the present invention, a zero-point signal detection circuit is provided to generate a synchronization control pulse, so that the input and output frequencies of the light source driving circuit are synchronized, so the interference of the difference frequency in the circuit is reduced. In order to make the above-mentioned and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below in conjunction with the accompanying drawings to describe in detail the following implementation. Please refer to FIG. 2, which A block diagram of a low-noise light source operating circuit according to the first embodiment of the present invention is shown. This light source operating circuit includes, for example, a light source of the fluorescent lamp 24 0 used in this embodiment, a feedback signal detection circuit 2 50, a light source driving circuit 2 3 0, a zero signal detection circuit 2 2 0, and a synchronous pulse width modulation. Transformer 210. Among them, the output terminal of the light source driving circuit 230 is coupled to the input terminal of the fluorescent lamp 240; and the zero signal detection circuit 220 is also coupled to the input terminal of the fluorescent lamp 240, and its output terminal is coupled to Synchronous pulse width modulator 2 1 0. The input terminal of the feedback signal detection circuit 2 50 is coupled to the output terminal of the fluorescent lamp 240; and the output terminal thereof is coupled to the synchronous pulse width modulator 2 10. Please continue to refer to Figure 2. The light source driving circuit 2 2 0 will generate a stable AC voltage output to drive the fluorescent lamp 2 4 0. At the same time, the zero signal detection circuit 2 2 0 will detect multiple zeros of this AC voltage output, and according to these zeros, the corresponding output of the zero signal detection circuit 2 2 0 will send the corresponding synchronization control pulse to the synchronous pulse width modulation.器 210。 210. The feedback signal detection circuit 250 converts the operating current of the fluorescent lamp 240 into a feedback signal and sends it to the synchronous pulse width modulation

11888twfl.ptc Page 11 1222336 _, No. 92123867_ Cr π: V. Description of the invention (7) Device 210. Synchronous pulse width modulator 210. Control the length of the duty cycle of the duty cycle signal outputted by the synchronous control pulse and the feedback signal, and send this duty cycle signal to the light source driving circuit 230. As shown in FIG. 2, a comparative embodiment of the synchronous pulse width modulator 2 10 includes a reference voltage generator 211, a synchronous triangle wave generator 212, a reverse error integrator 213, and a comparator 214. In the synchronous pulse width modulator 210, the synchronous triangle wave generator 212 is coupled to the zero signal detection circuit 220. The input terminals of the reverse error integrator 213 are respectively coupled to the feedback signal detection circuit 250 and the reference voltage generator 211, and the input terminals of the comparator 214 are respectively coupled to the synchronous triangle wave generator 212 and the inverse error integrator 213. 〇 Please also refer to FIG. 8, which shows a flowchart of a method for operating a low-noise light source according to a preferred embodiment of the present invention. As shown in step S8 丨 〇, the feedback signal detection circuit 2 50 rectifies the working current of the fluorescent lamp 2 40 into a feedback signal and sends it to the synchronous pulse width modulator 21 Inverting error integrator 213. As shown in step S820, after the feedback signal is compared with the reference voltage generated by the reference voltage generator 211, the error is integrated back to time to obtain the average error of the feedback signal and send it to the comparator 214. On the other hand, as shown in step S840, the synchronous triangle wave generated by the synchronous triangle wave generator 212 will also be sent to the other input terminal of the comparator. As shown in step g 8 3 〇, the comparator 214 compares the synchronous triangle wave with the average error of the feedback signal, and obtains a duty cycle signal from the output of the comparator 2 1 4. This duty cycle signal is then sent to the light source driving circuit 2 3 0. The duty cycle signal can be an integer multiple of the operating frequency of the fluorescent lamp 2 40, and since the duty cycle signal is a base

11888twfl.ptc Page 12 1222336

:: 3 The average error of t number is compared with the synchronous triangle wave. Therefore, when the working week is in the middle, and the sentence error is greater than the reference voltage, the synchronous pulse width modulator will refer to the voltage λ1 on the day of the week 2 signal. The duty cycle is reduced; and when the average error ratio f is considered, the duty cycle output from the synchronous pulse width modulator increases and the "Lei Zhou * period" signal will push the transistor switch of the light source drive circuit 2 3 0 Electricity 'causes it to send the external DC power source VDD to the oscillator circuit 2 3 2' This is how it is—the oscillator circuit 2 32 can generate a stable parent stream output to the fluorescent lamp 2 4 as shown in step S 850. . According to the above steps, when the fluorescent lamp 240 is started, its working current is zero two, and the over-feedback signal detection circuit 250 outputs a feedback signal to the inverse error integrator 2 1 3 'to compare the feedback signal with the reference voltage The post-inverse integration results in the average error of the feedback signal at the electrical f level. The feedback signal of this higher voltage level = 1, and the difference is sent to the comparator 2 丨 4. Please refer to Figure 3 at the same time, which plots the timing diagram of the average error of the feedback signal and the synchronous triangle wave. The average error of the high-voltage level feedback signal is compared with the synchronous triangle wave. Because of the higher voltage level, a larger duty cycle signal will be obtained to promote the electric crystal switch circuit, so that the oscillator circuit 2 3 2 will generate AC voltage output to start fluorescent lamp 240. After the fluorescent lamp 240 is started, the operating current is converted into a feedback signal by the feedback signal detection circuit 250, and after passing through the inverse error integrator 213, an average error of the feedback signal at a lower voltage level will be generated. The voltage level of the average error of the feedback signal generated by the inverting error integrator 213 will gradually decrease as the operating current of the fluorescent lamp 240 increases. At this time, the comparator 2 1 4 will also generate a job with a smaller duty cycle D 2

11888twfl.ptc Page 13 1222336

Corrected to make the oscillator circuit lamp 240 operate stably at the period λΛ to push the parent current output of the transistor switching circuit 2312 gradually smaller. Finally, a certain working current. Tang Guang Please refer to Figure 4A. The edge of the basin shows the signal detection circuit of the ηα signal and its hysteresis comparison within the zero point 2 2 0 of the second preferred embodiment of the control pulse ^ 21U clock diagram. The zero signal detected electricity 223, Leiyang 999 also respectfully connected the resistor 2 22 of the positive wheel input end to the resistor Λ Ϊ resistor 223 in series, and the other end of resistor 222 was connected to the input of fluorescent 1 ^ 'for Receives an AC voltage signal vac from a fluorescent lamp. The resistor ίIt is connected to the negative input of the hysteresis comparator. The hysteresis comparator m is coupled to the output of the buffer 224 and its negative input.

The positive input terminal of the kicker m receives the reference voltage Vref. The output of the hysteresis comparator 221 is simultaneously coupled to the input of the rising edge detection circuit 2 2 6. Or close one of the inputs of 22 7 ::! The output of the rising edge detection circuit 2 2 5 is coupled to the other input terminal of the falling edge detection circuit 226.

Please continue to refer to FIG. 4A. After the AC voltage signal VAC is divided by the resistors 2 2 2 and 2 2 3, the obtained sine wave signal is sent to the positive input terminal of the hysteresis comparator 221. After the reference voltage yref passes through the buffer 224, a DC reference potential is obtained and sent to the second input terminal of the hysteresis comparator 2 2 1. The sine wave signal and the DC reference potential pass through the hysteresis comparator 2 2 1 to obtain the pulse wave signal, and then pass through the rising edge detection circuit 2 2 5 and OR gate 2 2 7 to obtain the synchronization control pulse. Please refer to FIG. 4B, which shows another zero signal detection circuit and its clock diagram of the present invention. The positive input of comparator 2 3 1 receives the AC voltage signal.

11888twfl.ptc Page 14 1222336 _ Case No. 921238fi7 V. Description of the invention (10) VAC ′ Its negative input terminal receives the reference voltage Vrefi. The positive input of the comparator 232 receives the reference voltage Vref2, and its negative input receives the AC voltage signal VAC. When the AC voltage signal VAC is compared with the reference voltage Vrefl, the result of the comparison is sent to the rising edge detection circuit 2 3 5 to obtain the output of the pulse signal. When the AC voltage signal VAC is compared with the reference voltage Vref2, the comparison result is sent to the falling edge detection circuit 2 3 6 and the pulse signal output is also obtained. The outputs of the rising edge detection circuit 2 3 5 and the falling edge detection circuit 2 3 6 are respectively coupled to the OR gate 2 3 8 to obtain synchronous control pulses. Preparation, * ift FIG. 5 ′, which shows the synchronous triangle wave generator and the synchronous three 2¾ comparator 11 and the ratio in the synchronous triangle wave generator 212

Sim One input terminal is coupled to each other, and comparator 11 has another input peak reference potential vt, while the other input of comparator 12 is connected to the reference potential „The output end of comparator n is connected to ϊ Detection core 2 2 to receive the inverse or OR gate 2: 3: an input terminal is coupled to the output of the zero comparator 12 and is connected in one step. The output of the OR gate 13 is connected to the conduction between the switch 16 and the switch 15 No: f 51 One U out-end control Vo. Please also see the output of the 8th angle wave at the same time. After T1, the synchronous control pulse has not sent the lamp and its driving power, the zero detection circuit 220 will fluoresce. The synchronization control pulse and the triangular wave are mixed and synchronized to generate synchronization == a gate step angle wave generated by the synchronous control pulse at the falling edge of the second skin. In this embodiment, the synchronous triangle wave ^

1222336 Case No. 92123867 Amendment V. Description of the Invention (11) The generator is operated at twice the frequency of the glare lamp. Please refer to FIG. 6A, which shows a block diagram of an inversion error integrator according to a preferred embodiment of the present invention. The positive signal terminal of the operational amplifier (Operational Amplifier) 21 receives the feedback signal Vfb, and the negative signal terminal is connected in series with the resistor 23 and receives the reference voltage Vref. The capacitor 22 is connected between the negative signal terminal and the output terminal. Now assume that the resistor 2 The resistance value of 3 is r, and the capacitance value of capacitor 22 is C. Please refer to FIG. 6B for the output signal, which shows a block diagram of another inversion error integrator according to a preferred embodiment of the present invention. Operational transduction amplifier

The negative signal terminal of Trans conductance Amplifier (OTA) 24 receives the feedback signal Vfb, while the positive signal terminal receives the reference voltage Vref, and the output terminal is coupled to the capacitor 25 to ground. Now assuming that the transduction value of OTA is Gm, the capacitance value of capacitor 25 is C, and the output signal is v0, the average error of the feedback signal can be obtained in the above two embodiments. Please refer to FIG. 7, which shows a block diagram of a low-complexity light beam according to a second embodiment of the present invention. This embodiment adds a programmable phase-locked loop 261 to the circuit of the first embodiment. Its input signal detection circuit 2 2 0 is used to receive the same step, which is coupled to the zero point F f M2 #, and the program control input signal sent by the program control input device 2 6 2 is at the oscillation frequency. The synchronous writing number s is sent to the synchronous triangle wave generator 212 as soon as Niu Wu borrows money from the company. Page 16 1222336 _Case No. 92123867_ Year Month Day Amendment _ V. Description of the Invention (12) In the above two embodiments, the zero signal detection circuit synchronizes the output of the oscillator circuit with the switching frequency of the transistor switching circuit. Therefore, the difference frequency interference phenomenon is reduced. Especially in the second embodiment, because the programmable phase-locked loop can control the input signal through the program, a synchronization signal with an arbitrary multiple of the oscillation frequency can be obtained, so that the interference phenomenon is greatly reduced. Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes and retouch without departing from the spirit and scope of the present invention. The scope of protection of the invention shall be determined by the scope of the attached patent application.

11888twf1.ptc Page 17 1222336 _ Case No. 92123867_ Year Month and Day _i ±± _ Brief Description of Drawings Figure 1 is a block diagram of a conventional light source circuit. Fig. 2 is a block diagram showing an operation circuit of a low-noise light source according to the first comparative embodiment of the present invention. Figure 3 is a timing diagram showing the average error of the feedback signal and the synchronous triangle wave. Figure 4A is a clock diagram of a zero signal detection circuit and its synchronous control pulses according to a preferred embodiment of the present invention. Fig. 4B is a diagram showing another zero signal detection circuit and its clock diagram of the present invention. Figure 5 shows the synchronous triangle wave generator and the synchronous triangle wave clock.

Illustration. Figure 6A is a block diagram of an inversion error integrator according to a preferred embodiment of the present invention. FIG. 6B is a block diagram of another inversion error integrator according to a preferred embodiment of the present invention. FIG. 7 is a block diagram showing an operation circuit of a low-noise light source according to a second embodiment of the present invention. FIG. 8 is a flowchart of a method for operating a low-noise light source according to a preferred embodiment of the present invention. Schematic markup description

11, 12, 114, 214, 231, 232: Comparator 13: Invertor OR gate 14: Flip-flop 15, 16: Switch

11888twfl.ptc Page 18 1222336 _Case No. 92123867_Year Month_Modified illustration of simple diagram 21: Operational amplifiers 22, 25, 123: Capacitors 23, 222, 223: Resistor 110: Pulse width modulator 111, 21 1 : Reference voltage generator 112 triangle wave generator 113 error amplifier 120 light source driving circuit 121, 2 3 1: transistor switching circuit 122, 2 3 2: oscillator circuit 130: i light source 140 丨, 250: feedback signal detection power 210 Synchronous pulse width modulator 212 Synchronous triangle wave generator 213 Inverting error integrator 220 Zero signal detection circuit 221 Hysteresis comparator 224 Buffer 2 2 5, ， 235: Rising edge detection circuit 2 2 6 ， 236: Falling edge detection circuit 2 2 7! 238: OR gate 230 Light source driving circuit 240 Fluorescent lamp 261 Programmable phase-locked loop

11888twfl.ptc Page 19 1222336 Case No. 92123867_ Year, month and day correction diagram Brief description 262: Program control input device S 8 1 0 ~ S 8 50 0: Flow of a method for operating a low-noise light source in a preferred embodiment of the present invention ili 11888twfl.ptc Page 20

Claims (1)

1222336 _ Case No. 92123867_ Year, Month and Day Amendment _ 6. Application for patent scope 1. A low-noise light source operating circuit, including: a light source; a feedback signal detection circuit, coupled to the output end of the light source, for The working current of the light source is converted into a feedback signal; a light source driving circuit, an output end is coupled to the input end of the light source to generate an AC voltage output to drive the light source; a zero signal detection circuit, coupled Connected to the input end of the light source for detecting multiple zeros of the light source driving circuit, and sending a corresponding one of the synchronization control pulses from the output end according to the zeros; and a synchronous pulse width modulator coupled to the The output terminal of the zero signal detection circuit controls the length of a work cycle signal according to the synchronization control pulse and the feedback signal, and sends the work cycle signal to the light source driving circuit. 2. The low-noise light source operating circuit according to item 1 of the scope of patent application, the synchronous pulse width modulator includes: a reference voltage generator for generating a reference voltage; a synchronous triangle wave generator, coupled To the zero signal detection circuit, a synchronous triangle wave signal is generated according to the synchronous control pulse; a reverse error integrator, the input end is respectively coupled to the feedback signal detection circuit and the reference voltage generator, and the feedback signal After comparing the signal with the reference voltage, an average error of the feedback signal is obtained; and a first comparator, the input terminal is respectively coupled to the synchronous triangle wave generator and the reverse error integrator, and compares the synchronous triangle wave signal with the feedback The average error of the signal is obtained to obtain the duty cycle signal. 11888twf1.ptc Page 21 1222336 _Case No. 92123867_ Month and Day __ VI. Patent application scope 3. As described in the patent application scope of the low-noise light source operating circuit, the zero signal detection circuit includes: a The hysteresis comparator has a first input terminal and a second input terminal, and an output terminal outputs a pulse wave signal; a buffer, the input terminal receives the reference voltage, and the reference voltage passes through the buffer to obtain a DC reference potential. And the output terminal is coupled to the second output terminal of the hysteresis comparator; a rising edge detection circuit is coupled to the output terminal of the hysteresis comparator; a falling edge detection circuit is coupled to the hysteresis An output terminal of the comparator; and an OR gate, the input terminals are respectively coupled to the rising edge detection circuit and the falling edge detection circuit, and output the synchronization control pulse; wherein the first input terminal is coupled to a first A resistor and a second resistor, the first resistor is connected in series with the second resistor, and the other end of the first resistor is coupled to the input end of the light source to receive an AC voltage signal of the light source, and the second resistance another End is coupled to the second input terminal. 4. The operation circuit of the low-noise light source according to item 2 of the scope of the patent application, the synchronous triangle wave generator includes: a second comparator, an input terminal of which receives a triangle wave peak reference potential; a third comparator, One input terminal receives a triangular wave valley reference potential, the other input terminal is coupled to the other input terminal of the second comparator; an inverting OR gate, one input terminal is coupled to the output terminal of the second comparator, and the other An input terminal receives the synchronization control pulse; and 11888twf1.ptc Page 22 1222336 _ Case No. 92123867 Sixth, the scope of patent application is to amend a flip-flop, one input end is connected to the output terminal of the invertor gate, and the other input end is coupled to the third comparator The output side generates the synchronous triangle wave. 5. According to the low-noise light source operating circuit described in item 4 of the patent application scope, the synchronous triangle wave generator operates at twice the frequency of the light source. 6. The low-noise light source operating circuit as described in item 1 of the scope of patent application, the low-noise light source operating circuit further includes: a programmable phase-locked loop, the input receiving the synchronization control pulse, and controlling according to a program The input signal generates a synchronization signal; and a program control input device, the output end is coupled to the programmable phase-locked loop, and the program control input signal can be generated. 7. —A method for operating a low-noise light source, which is suitable for a light source operating circuit. The light source operating circuit includes a driving circuit and a synchronous triangle wave generator. The synchronous operating method includes the following steps: Passing the working current of the light source through Rectify and convert into a feedback signal; compare the feedback signal with a reference voltage and integrate the comparison result to get the average error of the feedback signal; the synchronous triangle wave generator will generate a synchronous triangle wave; average the feedback signal After comparing the error with the synchronous triangle wave, a duty cycle signal is obtained; and the AC voltage generated according to the duty cycle signal is output to the light source. 8 · The method of operating a low-noise light source as described in item 7 of the scope of the patent application, wherein the method of generating the synchronous triangle wave includes the following steps: generating the light source together with the zero detection of the resonant frequency of the driving circuit 11888twf1.ptc Page 23 1222336 Case No. 92123867 Amendment VI. Patent application step control pulse; and mixing the synchronous control pulse with a triangular wave, wherein the falling edge of the triangular wave is synchronized by the synchronous control pulse to generate the synchronous triangular wave . 11888twf1.ptc Page 24