WO2011075881A1

WO2011075881A1 - Method for adjusting light of fluorescent lamp

Info

Publication number: WO2011075881A1
Application number: PCT/CN2009/075784
Authority: WO
Inventors: 邹高迪
Original assignee: Zou Gaodi
Priority date: 2009-12-21
Filing date: 2009-12-21
Publication date: 2011-06-30

Abstract

A method for adjusting light of a fluorescent lamp is used to adjust the light of the fluorescent lamp by an electronic ballast or an integral fluorescent lamp circuit. The electronic ballast and the integral fluorescent lamp circuit include a single-chip microcomputer, a D/A conversion circuit connected with the single-chip microcomputer and a high-frequency inversion circuit with the input end connected with the D/A conversion circuit. The input end of the single-chip microcomputer is connected with an APFC circuit having a constant working frequency to identify working current pulses. In the state of complete turnon, the number Ym of the working current pulses corresponds to the brightest state. The light adjusting control voltage signal is Xm in the state. The relation between the number Y of the working current pulse in the period of the one way pulse voltage and the light adjusting control voltage signal X is modified into a linear relation or a logarithmic relation. Thus the light adjusting control voltage signal X1 which will be sent to the high-frequency inversion circuit to adjust the light is generated.

Description

Fluorescent lamp dimming method

The invention relates to an electronic ballast for a fluorescent lamp or a dimming method for an integrated fluorescent lamp. Background technique

Fluorescent lamps are one of the most commonly used lighting sources. As people's demands for energy saving and lighting effects continue to increase, there has been a method of adjusting the brightness of fluorescent lamps to achieve different lighting effects according to different lighting requirements such as illumination brightness and lighting atmosphere.

As shown in FIG. 1 , the existing low-power ordinary electronic ballast or integrated fluorescent lamp circuit below 25 watts adopts sequentially connected EMI circuit 1 (Electro Magnetic Interference filter circuit), rectifier circuit 2, DC filter circuit 4 and The controllable high frequency inverter circuit 5 drives the fluorescent tube 6 by the high frequency inverter circuit 5.

As shown in FIG. 2, the existing high-power ordinary electronic ballast or integrated fluorescent lamp circuit of 25 watts or more adopts sequentially connected EMI circuit 1, rectifier circuit 2, passive power factor correction circuit PPFC (Passive Power Factor Correction Circuitry, Also known as passive power factor correction circuit) or active power correction circuit APFC (Active Power Factor Correction Circuitry), DC filter circuit 4 and tunable high frequency inverter circuit 5, The high frequency inverter circuit 5 drives the fluorescent tube 6.

As shown in FIG. 3, the existing dimming method for the fluorescent lamp by the medium-high power ordinary electronic ballast or the integrated fluorescent lamp circuit of 25 watts or more is: adding the order between the rectifier circuit 2 and the high-frequency inverter circuit 5 The connected buck shaping circuit 8 and the integrating and smoothing circuit 9 are provided with a fluorescent lamp current detecting circuit 7 between the fluorescent tube 6 and the high frequency inverter circuit 5. The fluorescent lamp current detecting circuit 7 detects the illuminating current of the fluorescent tube 6 and performs shaping and smoothing processing, and then outputs it to the high frequency inverter circuit 5; the buck shaping circuit 8 and the integrating and smoothing circuit 9 are connected before the EMI circuit 1 Before and after the phase-cut dimmer (not shown) is phase-adjusted and decompressed and rectified by the EMI circuit 1 and the rectifier circuit 2, the mains voltage is subjected to buck, shaping, integration, smoothing, etc., to obtain a The low voltage signal which is approximately proportionally changed with the effective value after inputting the phase cut of the alternating current is output to the high frequency inverter circuit 5, and the high frequency inverter circuit 5 is adopted. By means of frequency modulation, widening or voltage regulation, the luminous current of the fluorescent tube is controlled to be the same as the effective value of the input voltage after the phase-cut adjustment, so that the phase-cut dimmer is dimmed on the input line, and the brightness of the fluorescent tube is pressed. The dimming effect of the proportional change.

The existing dimming methods for low power and medium and high power fluorescent lamps have the following drawbacks:

1. Since no active or passive power correction circuit is provided, the low-power fluorescent lamp is susceptible to harmonic interference of the power grid, causing problems such as flickering of fluorescent lamps and unstable illumination;

2. For low-power fluorescent lamps, when the input voltage waveform is phase-cut, the transistor in the phase-cut dimmer is turned on or off instantaneously to generate a high-point pulse, which interacts with the capacitor and the inductor in the circuit to generate a shift. Phase and resonance will affect the stability of the operation of the latter stage circuit, and in extreme cases may cause the rear stage circuit to burn out;

3. For low-power fluorescent lamps, when the input voltage is phase-cut, the effective value is very low, and the fluorescent lamp is not started (ie, no load), a smooth proportional low-voltage signal cannot be obtained, resulting in the high-frequency inverter circuit failing to start. Work; The high-frequency inverter circuit must start working when the effective value of the input voltage reaches a certain height, so that the starting point of the whole ballast or integrated fluorescent lamp circuit is too high, resulting in a narrow dimming range, and the fluorescent lamp cannot be adjusted at low brightness. ;

4. For low-power fluorescent lamps and medium-high-power fluorescent lamps, since the input mains voltage is sinusoidal voltage, the phase-cut dimming process and the sinusoidal phase-cut voltage have a nonlinear relationship, and the final actual brightness adjustment of the fluorescent lamp is inevitable. It is non-linear, which causes the existing dimmer to adjust the brightness of the fluorescent lamp in the adjustment of the rear stage. Summary of the invention

The technical problem to be solved by the present invention is to provide a fluorescent lamp dimming method, which overcomes the flickering and illuminating instability of the fluorescent lamp dimming in the prior art, and the phase shifting and resonance of the fluorescent lamp circuit due to the phase-cut voltage spike, and the rear-stage circuit The stability of work is affected, the starting point of the ballast circuit is high, the dimming range is narrow, the fluorescent lamp cannot be adjusted at low brightness, and the brightness adjustment of the fluorescent lamp is nonlinear. The dimmer is adjusted in the rear stage, and the brightness of the fluorescent lamp is not adjusted. Obviously and other defects.

The technical solution adopted by the present invention to solve the technical problem thereof is: providing a fluorescent lamp dimming method, based on using a common phase-cut dimmer to perform fluorescent lamps on a fluorescent lamp electronic ballast or an integrated fluorescent lamp circuit Brightness adjustment: The fluorescent electronic ballast or integrated fluorescent lamp circuit comprises a sequentially connected EMI circuit, a rectifier circuit, an active power correction circuit, a DC filter circuit and a controllable high frequency inverter circuit, the high frequency inverter The circuit is connected to the fluorescent tube, and the fluorescent lamp illuminating current detecting circuit is further connected between the fluorescent tube and the high-frequency inverter circuit; and the method further includes a single-chip microcomputer and a digital-to-analog conversion circuit, wherein the output end of the single-chip microcomputer passes through a digital/analog conversion circuit connected to an input end of the high frequency inverter circuit, wherein the input end of the single chip is connected to the active power correction circuit to identify and count an operating current pulse of the circuit; The circuit operating frequency is fixed;

The dimming method includes:

Defining the number of working current pulses Y _m counted in the all-on state of the phase-cut dimmer corresponds to a maximum brightness state with a phase angle of 180 degrees, the maximum brightness state corresponding to the dimming control voltage signal being X _m ; Modifying the relationship between the required analog dimming control voltage signal X corresponding to adjusting the brightness of the fluorescent lamp and the number Y of counting the working current pulses in a rectified one-way ripple voltage period is a linear relationship or a logarithmic relationship;

And the digital/analog conversion circuit generates a dimming control voltage signal corresponding to the number of counts of the working current pulses when the phase-cut adjustment is performed according to the modified linear relationship or logarithmic relationship, and the The dimming control voltage signal is sent to the high frequency inverter circuit for dimming.

In the fluorescent lamp dimming method of the present invention, the linear relationship between the number Y of the operating current pulses in a one-way ripple voltage period and the required dimming control voltage signal X corresponding to the brightness of the fluorescent lamp is as follows Condition determination: In the all-on state, the counting number Y _{m of} the working current pulse corresponds to the maximum brightness state of the fluorescent lamp, and the corresponding dimming control voltage signal is X _m; the counting number of the working current pulse is two points One of the Y _m corresponds to the 50% brightness state of the fluorescent lamp, and the corresponding dimming control voltage signal is one-half X _m .

In the fluorescent lamp dimming method of the present invention, the logarithm of the number Y of the operating current pulses in a one-way ripple voltage cycle and the required dimming control voltage signal X corresponding to the brightness of the fluorescent lamp is The following conditions are determined: In the all-on state, the counting number Y _{m of} the working current pulse corresponds to the maximum brightness state of the fluorescent lamp, and the corresponding dimming control voltage signal is X _m .

In the fluorescent lamp dimming method of the present invention, the active power correction circuit operates in a boost mode. In the fluorescent lamp dimming method of the present invention, a digital circuit for frequency division is further included, an output end of the digital circuit is connected to an input end of the single chip, and an input end of the digital circuit is connected to the active power correction circuit The operating current pulse of the active power correction circuit is identified and divided, and the single chip counts the divided pulses.

In the fluorescent lamp dimming method of the present invention, the input end of the single chip is connected to the secondary winding of the boosted storage inductor L1 in the active power correction circuit, or the transistor Q1 in the active power correction circuit A resistor R is connected in series between the negative poles of the power supply, and the input end of the single chip is connected between the transistor Q1 and the resistor R.

In the fluorescent lamp dimming method of the present invention, the dimming control voltage signal is generated as follows: the digital-to-analog conversion circuit is a string and is connected to a group of resistors on a plurality of 10 ports of the single chip microcomputer. The set of resistors is coded and mixed to generate the dimming control voltage signal.

In the fluorescent lamp dimming method of the present invention, the dimming control voltage signal is generated as follows: the digital/analog conversion circuit is an integral filter circuit, and the single chip outputs a high frequency pulse width modulation signal via the integral filter The circuit performs integral filtering to generate the dimming control voltage signal. In the fluorescent lamp dimming method of the present invention, the dimming control voltage signal is generated as follows: the digital/analog conversion circuit can be externally connected by a D/A chip. At the output of the microcontroller or integrated in the microcontroller.

The fluorescent lamp dimming method embodying the present invention has the beneficial effects compared with the prior art:

1. Counting the operating current pulses detected by the active power correction circuit during a rectified one-way ripple voltage cycle, by modifying the dimming control voltage signal to the operating current pulse count detected with the active power correction circuit The number is linear or logarithmic, which realizes the full range of smooth dimming of fluorescent lamps, which can achieve the same dimming effect as incandescent lamps and tungsten halogen lamps;

2. Since the characteristics of the human eye are more sensitive to low brightness than high brightness, the logarithmic curve dimming is in line with the human eye's need for light sensitivity, so the dimming effect is smoother and more comfortable;

3. By using active power correction circuit (APFC circuit), the interference of power grid harmonics is eliminated. Ensure that the fluorescent lamp is stably illuminated; the APFC circuit ensures that the line voltage and the line current are in phase, avoiding the phenomenon of voltage spike phase shift after phase cutting, and is less prone to resonance, ensuring stable and safe operation of the rear stage circuit; when the APFC circuit is operated in boost mode, When the effective voltage is low after phase-cut adjustment, the fluorescent lamp can be normally lit, which solves the problem that the starting point of the existing fluorescent lamp is too high;

4. Use any existing front and rear edge-cut dimmer to adjust the brightness of the fluorescent lamp for full compatibility. DRAWINGS

The present invention will be further described with reference to the accompanying drawings and embodiments in which:

Figure 1 is a block diagram showing the structure of a conventional low-power ordinary electronic ballast or integrated fluorescent lamp within 25 watts.

Fig. 2 is a block diagram showing the structure of a conventional high-power ordinary electronic ballast or integrated fluorescent lamp of 25 watts or more.

Figure 3 is a block diagram of the conventional dimming method for a medium-high power common electronic ballast or integrated fluorescent lamp of 25 watts or more.

4 is a circuit diagram of an electronic ballast or an integrated fluorescent lamp of the fluorescent lamp dimming method of the present invention.

Fig. 5 is a view showing an embodiment of the detection of the working pulse signal of the active power correction circuit in the dimming method of the fluorescent lamp of the present invention.

Fig. 6 is another embodiment of detecting the working pulse signal of the active power correction circuit in the dimming method of the fluorescent lamp of the present invention.

Figure 7 is a block diagram showing the principle of the dimming method of the fluorescent lamp of the present invention.

Fig. 8 is a diagram showing voltage adjustment waveforms corresponding to a fluorescent lamp electronic ballast or an integrated fluorescent lamp circuit in the fluorescent lamp dimming method of the present invention.

Figure 9 is a comparison of the correction curve and the uncorrected curve of the relationship between the number Y of operating current pulses of the APFC circuit and the dimming control voltage signal X in the dimming method of the fluorescent lamp of the present invention.

10 is a fluorescent lamp corresponding to the dimming control voltage signal X corresponding to the dimming phase of the dimmer corresponding to the number of counts of the working current pulses of the APFC circuit in the dimming method of the fluorescent lamp of the present invention. The relationship between the corrected curve and the uncorrected curve as a function of the percentage of tube luminous flux. detailed description

The fluorescent lamp dimming method of the present invention performs fluorescence brightness adjustment based on an electronic ballast or an integrated fluorescent lamp circuit as shown in Fig. 7, and Fig. 4 shows a specific example.

As shown in FIG. 4 and FIG. 7, the fluorescent lamp electronic ballast or the integrated fluorescent lamp circuit includes a EMI circuit 1, a rectifying circuit 2, and an active power correcting circuit 3 (APFC circuit, as shown in FIG. 4, which are sequentially connected). The power correction circuit 3 includes a boosted energy storage inductor L1, a boost diode D, a transistor Q1, and an APFC driver chip 31 (such as NCP1653, Ucl854 series, etc.), and the function of the APFC driver chip can also be programmed by a single chip microcomputer. The corresponding peripheral circuit is replaced by), the DC filter circuit 4 and the tunable high frequency inverter circuit 5 (such as a half bridge inverter drive circuit), the high frequency inverter circuit 5 is connected to drive the fluorescent tube 6, and the EMI circuit 1 is connected at the input end. The phase cut dimmer 100 performs phase cut adjustment (as shown in Figure 8). A fluorescent lamp illuminating current detecting circuit 7 is further connected between the fluorescent tube 6 and the high frequency inverter circuit 5, and a single chip microcomputer 10 and a digital/analog conversion circuit are connected between the active power correcting circuit 3 and the high frequency inverter circuit 5. 11. The output end of the single chip microcomputer 10 is connected to the input end of the high frequency inverter circuit through the digital/analog conversion circuit 11, and the input end of the single chip microcomputer 10 is connected to the active power correction circuit 3 to perform the working current pulse of the active power correction circuit 3. Identify and count. The active power correction circuit 3 has a fixed operating frequency.

The detection mode of the working current pulse of the APFC circuit 3 includes but is not limited to:

As shown in FIG. 4, the operating current pulse of the APFC circuit 3 is detected by connecting the input terminal of the microcontroller 10 to the secondary winding of the boosting energy storage inductor L1 in the active power correcting circuit 3.

As shown in FIG. 5, by connecting the resistor R in series between the transistor Q1 and the negative pole of the power supply in the active power correction circuit 3, the input terminal of the microcontroller 10 is connected between the transistor Q1 and the resistor R, and the operation of the APFC circuit 3 is detected. Current pulse.

As shown in FIG. 6, by connecting the input end of the APFC driving chip 31 in the APFC circuit 3 to the rectified positive voltage positive electrode, the output end of the APFC driving chip 31 is connected to the driving end of the transistor Q1 and simultaneously connected to the input end of the single chip microcomputer. . The APFC driving chip 31 is configured to detect the presence or absence of a unidirectional ripple voltage. When there is a phase-cut voltage, a pulse is generated and output to the driving terminal of the transistor Q1 to generate an operating current. Therefore, this pulse is equivalent to the operating current pulse of the transistor Q1, and therefore, the microcontroller detects the operating current pulse of the transistor Q1 (i.e., the operating current pulse of the APFC circuit 3).

The fluorescent lamp dimming method of the present invention comprises:

The number of operating current pulses Y _m of the APFC circuit 3 that is counted in the fully-on state of the phase-cut dimmer corresponds to a maximum brightness state with a phase angle of 180 degrees, and the maximum brightness state corresponds to a dimming control voltage signal of X _{m .} .

The dimming control voltage signal X is modified as follows: The relationship between the dimming control voltage signal X corresponding to the brightness of the fluorescent lamp and the number Y of the working current pulse counted in a unidirectional pulsating voltage cycle after rectification is linear or Number relationship; that is, establish a Y=aX+b relationship or a Y=lo aX relationship. The dimming control voltage signal X uses an analog signal.

The single chip microcomputer 10 and the digital/analog conversion circuit 11 generate a dimming control voltage signal corresponding to the number of counts of the operating current pulses of the APFC circuit 3 in the phase-cut adjustment according to the modified linear relationship or logarithmic relationship, and then dim the dimming The control voltage signal is sent to the high frequency inverter circuit 5, and the fluorescent tube 6 is dimmed.

Defines the rise of the first operating current pulse during a rectified one-way ripple voltage cycle. The phase of the starting edge is 0 degrees, and the phase of the falling edge of the last operating current pulse is the final phase angle.

The 0 degree phase angle and the final phase angle defined above correspond to 0 degrees and 180 degrees in one unidirectional ripple voltage period after rectification. During a rectified one-way ripple voltage cycle, the number of pulses of the operating current pulse train of the APFC circuit 3 is Y _m , and the operating current of the single chip 10 to the APFC circuit 3 after phase-cut dimming according to the phase-cut dimmer 100 The linear relationship or logarithmic relationship between the number of pulses and the Y, X, can determine the corresponding phase-cut phase, that is, the phase-cut position of the phase-cut dimmer 100.

Figure 8 shows the waveform A of the segments A, B, C, D, E in the electronic ballast or integrated fluorescent lamp circuit before the phase cut of the phase-cut dimmer 100 and the waveform B after the phase-cut, transmitted to the EMI The waveform C after the circuit, the waveform D after rectification, the waveform E of the APFC circuit boosted by the DC filter, and the waveform F of the operating current pulse of the APFC circuit detected by the single chip, wherein Bi, d, indicate the front edge phase-cut dimming The corresponding voltage waveform is cut, and B ₂ , C ₂ , and D ₂ represent the corresponding voltage waveforms of the trailing edge phase-cut dimmer. E is the high voltage direct current VBUS formed by the DC filter 4 after the APFC circuit 3 is boosted, as The operating voltage of the high frequency inverter circuit 5 that can be regulated by the latter stage. The current pulse signal obtained from the secondary winding of the boosted storage inductor L1 is shown, and F ₂ represents the current pulse signal obtained from the transistor Q1 and the voltage negative series resistor R.

The manner in which the linear relationship of Y and X described above is determined includes but is not limited to:

1. In the all-on state, the counting number Y _{m of the} working current pulse corresponds to the maximum brightness state of the fluorescent lamp, and the corresponding dimming control voltage signal is X _m; the counting number of the working current pulse is one-half Y _m corresponding The 50% brightness state of the fluorescent lamp, corresponding to the dimming control voltage signal is one-half X _m , and the linear function Y=aX+b is determined according to the two-point condition.

2. In the all-on state, the number of working current pulses Y _m corresponds to the maximum brightness state of the fluorescent lamp, and the corresponding dimming control voltage signal is X _m; 0 voltage point in a unidirectional ripple voltage cycle after rectification The number of working current pulses is 0, corresponding to the off state of the fluorescent lamp, and the corresponding dimming control voltage signal is Y _Q , and the linear function Y=aX+b is determined according to the two conditions.

The logarithmic relationship of the above Y and X is determined as follows: In the all-on state, the count number Y _{m of the} working current pulse corresponds to the maximum brightness state of the fluorescent lamp, and the corresponding dimming control voltage signal is X _m , and is determined according to the condition. The logarithmic function Υ = ^ aX.

The APFC circuit 3 can be operated in a boost mode or in other modes, such as a buck mode or an isolated conversion mode.

When the recognition speed of the high-frequency working current pulse of the active power correction circuit cannot be kept up, the following manner can be adopted: setting a digital circuit for frequency division, the output end of the digital circuit is connected to the input end of the single chip 10, the number The input end of the circuit is connected to the active power correction circuit 3 to identify and divide the operating current pulse of the active power correction circuit 3, and the single chip microcomputer 10 counts the divided pulses.

The digital circuit divides the operating current pulse of the active power correction circuit 3 as needed, and if the frequency is divided by four, a satisfactory recognition and counting effect can be obtained.

The above digital/analog conversion circuit 11 can be externally connected to the output terminal of the single chip microcomputer 10 or integrated in the single chip microcomputer 10 to generate a dimming control voltage signal.

The dimming control voltage signal is generated according to, but not limited to, the following:

1. The digital/analog conversion circuit 11 adopts a string and is connected to one of the plurality of 10 ports of the single chip microcomputer 10. The group resistance is encoded and mixed by the set of resistors to generate a dimming control voltage signal.

2. The digital/analog conversion circuit adopts an integral filter circuit, and the single chip microcomputer 10 outputs a high frequency pulse width modulation signal to perform integral filtering through the integral filter circuit to generate a dimming control voltage signal.

Xl o

As shown in FIG. 9 and FIG. 10, the relationship between the dimming control voltage signal X and the number Y of the operating current pulse counts is modified to a relationship after a linear relationship or a logarithmic relationship, and an unmodified dimming control voltage signal X. Compared with the number Y of the working current pulse count, the modified corresponding dimming effect is in line with the characteristics that the human eye is sensitive to low brightness and insensitive to high brightness, so that the existing ordinary dimmer is used by using the present invention. Dimming the fluorescent lamp to achieve a smooth and comfortable dimming effect over the entire range.

Claims

Claim

1 . A fluorescent lamp dimming method, based on adjusting a brightness of a fluorescent lamp electronic ballast or an integrated fluorescent lamp circuit by using a common phase-cutting dimmer: the fluorescent electronic ballast or the integrated fluorescent lamp circuit comprises sequentially connected EMI a circuit, a rectifier circuit, an active power correction circuit (APFC:), a DC filter circuit, and a controllable high frequency inverter circuit, the high frequency inverter circuit is connected to a fluorescent tube, the fluorescent tube and the high frequency inverter A fluorescent lamp illuminating current detecting circuit is further connected between the circuits; and further comprising a single chip microcomputer and a digital/analog converting circuit, wherein an output end of the single chip microcomputer is connected to the high frequency inverter circuit through the digital/analog converting circuit The input end, the input end of the single chip is connected to the active power correction circuit to identify and count the working current pulse of the circuit; the working frequency of the active power correction circuit is fixed;

The dimming method includes:

2. The fluorescent lamp dimming method according to claim 1, wherein the number Y of the operating current pulses is counted in a one-way ripple voltage cycle and the required dimming control corresponding to the brightness of the fluorescent lamp is adjusted. The linear relationship of the voltage signal X is determined according to the following conditions: In the all-on state, the counting number Y _{m of} the working current pulse corresponds to the maximum brightness state of the fluorescent lamp, and the corresponding dimming control voltage signal is X _m; the operating current The number of pulses counted is one-half Y _m corresponding to the 50% brightness state of the fluorescent lamp, and the corresponding dimming control voltage signal is one-half X _m .

3. The fluorescent lamp dimming method according to claim 1, wherein the number Y of the operating current pulses is counted in a one-way ripple voltage period and the brightness of the fluorescent lamp is adjusted.

1 The logarithmic relationship of the required dimming control voltage signal X is determined according to the following conditions: In the all-on state, the counting number Y _{m of} the working current pulse corresponds to the maximum brightness state of the fluorescent lamp, and the corresponding dimming control voltage signal is x. _m .

4. The fluorescent lamp dimming method according to claim 1, wherein said active power correction circuit operates in a boost mode.

The fluorescent lamp dimming method according to claim 1, further comprising a digital circuit for frequency division, wherein an output end of the digital circuit is connected to an input end of the single chip, and an input end of the digital circuit is connected to the The active power correction circuit identifies and divides the operating current pulse of the active power correction circuit, and the single chip counts the divided pulses.

The fluorescent lamp dimming method according to claim 1, wherein the input end of the single chip is connected to a secondary winding of the boosted energy storage inductor L1 in the active power correction circuit, or the active A resistor R is connected in series between the transistor Q1 and the negative pole of the power supply in the power correction circuit, and the input end of the single chip is connected between the transistor Q1 and the resistor R.

The fluorescent lamp dimming method according to any one of claims 1 to 6, wherein the dimming control voltage signal is generated as follows: the digital/analog conversion circuit is a string, and is connected to the single chip microcomputer A set of resistors on the plurality of 10 ports are encoded and mixed by the set of resistors to generate the dimming control voltage signal Xi.

The fluorescent lamp dimming method according to any one of claims 1 to 6, wherein the dimming control voltage signal is generated as follows: the digital/analog conversion circuit is an integral filter circuit, and the single chip output A high frequency pulse width modulation signal is integrated and filtered by the integral filter circuit to generate the dimming control voltage signal.

The fluorescent lamp dimming method according to any one of claims 1 to 6, wherein the digital/analog conversion circuit can be externally connected to the output end of the single chip microcomputer or integrated in the D/A chip. In the microcontroller.

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