CN1691870A - Dimmer for cold cathode fluorescent tube - Google Patents
Dimmer for cold cathode fluorescent tube Download PDFInfo
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- CN1691870A CN1691870A CN 200410037574 CN200410037574A CN1691870A CN 1691870 A CN1691870 A CN 1691870A CN 200410037574 CN200410037574 CN 200410037574 CN 200410037574 A CN200410037574 A CN 200410037574A CN 1691870 A CN1691870 A CN 1691870A
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- fluorescent tube
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- 238000005516 engineering process Methods 0.000 claims description 7
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- 238000006243 chemical reaction Methods 0.000 abstract description 7
- 230000000737 periodic effect Effects 0.000 abstract 2
- 238000000034 method Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000005669 field effect Effects 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 208000031361 Hiccup Diseases 0.000 description 2
- 230000005284 excitation Effects 0.000 description 2
- 206010034703 Perseveration Diseases 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 230000009931 harmful effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
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Abstract
The invention discloses a light modulation apparatus for cold cathode fluorescent lamp tube, and discloses an apparatus which combines with frequency conversion and impulse width change, it adjust the brightness of the cold cathode fluorescent lamp tube through changing the output current and voltage of the piezo-electric transformer; the invention uses a PWM controller to adjust work periodic time, and uses a frequency to control the IC to work in different work periodic time, so to drive the resonant frequency of the piezo-electric transformer, by this to adjust the output current and voltage of the piezo-electric transformer, and then provides a light modulation apparatus which can adjust the brightness of the cold cathode fluorescent lamp tube and improve the age limit of the piezo-electric transformer.
Description
Technical field
The present invention relates to a kind of light modulating device of fluorescent tube, particularly a kind of by changing the type of drive of piezoelectric transformer, and then change the device that its output voltage and electric current reach the brightness of adjustment cathode fluorescent tube.
Background technology
The piezoelectric ceramics transformer was proposed by C.A.Rosen at first in 1956.Its operation principle is with different by the magnetic transformer of electromagnetic energy conversion, and piezoelectric transformer is to convert electromotive force to mechanical energy (this transfer process is called inverse piezoelectric effect) earlier, mechanical energy is converted to electric energy (this transfer process is called direct piezoelectric effect) again.
Because the development of magnetic transformer and piezoelectric transformer makes us can produce the transducer of high efficiency, small size.Compare with piezoelectric transformer, may be thicker, heavier and efficient is lower at a given power level magnetic transformer, but that it has a cost is low, and the advantage that can under wideer loading condition, work.All the time, needed high driving voltage of cathode fluorescent tube and high excitation voltage are that Wound-rotor type magnetic transformer by high turn ratio provides.But because the development of piezoelectric transformer for its application provides better advantage, comprises advantages such as efficient is higher, volume is littler, electromagnetic noise is lower, available excitation voltage is higher, not flammable and sinusoidal operation.
Traditional Switching Voltage Regulator (switching mode regulator) is by the switching time of adjusting power circuit, obtains different output voltages and electric current.Its basic operation principle is to come ON/OFF one power switch by a controller, and element commonly used is that golden oxygen is partly led field-effect transistor (MOSFET).By the action of control switch, we can obtain required voltage and electric current.
The most frequently used control method is a position standard of directly or indirectly comparing an output voltage and a triangular wave, with the length of decision ON/OFF time, also is so-called pulse wave width modulation method (PWM, pulse width modulation).It is punctual also promptly to be higher than (or being lower than) certain position in the position of triangular wave standard, and the golden oxygen that just will be connected to the top of power supply is partly led field-effect transistor and opened; Otherwise then because inductor rectifier has the effect that electric current is continued, electric current can be via the electric current channel circulation of below.The golden oxygen of top is partly led the time scale of opening of field-effect transistor, is referred to as the work period.The regulative mode of Switching Voltage Regulator just is to change voltage by changing the work period basically.
In the patent of No. the 504101st, approved TaiWan, China patent, disclosed a kind of " high-brightness fluorescent lamp tube drive device ", it mainly is by a high-frequency generator, pulse-width regulating device, first and second power switchs, and piezoelectric transformer constitutes, it produces high frequency ac signal by high-frequency generator, convert it to the pulse wave width modulation resonant frequency signal by a pulse-width regulating device again, utilize the positive half period and the negative half-cycle of this pulse wave width modulation resonant frequency signal to drive two power switchs respectively, distinguish two inputs of the primary coil of drive pressure piezoelectric transformer again, so that piezoelectric transformer produces the voltage that is enough to promote cathode fluorescent tube; Provide a kind of cathode fluorescent tube drive unit with this with high conversion efficiency and high voltage step-up ratio.In brief, this known patented technology is to utilize the mode of pulse-width modulation, with high frequency decide frequency signal drive pressure piezoelectric transformer, come the power controlling switch by the DCM of deciding frequency; And this method usually be higher than the frequency that naked eyes can discover (＞100Hz) control the average current of fluorescent tube by the break-make of modulation duty cycle, and its frequency is changeless.
Also have in addition and a kind ofly be called prominent punch die formula (burst mode) or the pattern (hiccup mode) or omit the technology of cyclic pattern of claiming to have the hiccups by what Philips proposed.When load descended suddenly, control loop required to shorten ON time T
On, under the situation of some loads, the control circuit of pulse mode begins to prevent ON time T
OnReduce, also begin periodically to cover simultaneously the pulse of Wave-wide regulation controlled electric then.Power supply can cover Cycle Length by reducing burst width or increase, and is issued to the purpose of saving energy in different loads.This technology has two obvious defects, be exactly the low-frequency disturbance meeting and cover the cycle together resonance occur, and the flip-flop of load also can cause the output voltage bust; Particularly utilize this kind power supply control model drive pressure piezoelectric transformer, can make piezoelectric transformer continually be recharged or the situation of cutting off the electricity supply fully under perseveration, for piezoelectric transformer, will influence its useful life.
Summary of the invention
The invention discloses a kind of light modulating device of cathode fluorescent tube, particularly a kind of device in conjunction with frequency conversion and pulse wave width modulation changes the output voltage and the electric current of piezoelectric transformer, and then reaches the light modulating device of the brightness of adjusting cathode fluorescent tube.
The present invention utilizes a resonance frequency control unit dynamically to change its resonance frequency in order to the drive pressure piezoelectric transformer, be exactly the voltage gain (gain) that changes piezoelectric transformer by the mode of dynamic frequency-conversion in brief, and then reach output voltage and the electric current of adjusting piezoelectric transformer, and then reach the purpose of the brightness of adjusting cathode fluorescent tube.
Another object of the present invention is to provide a kind of output voltage and the electric current that can adjust piezoelectric transformer, and can be to not causing dysgenic power control its useful life.
The present invention also utilizes a PWM control unit, with the control mode of pulse wave width modulation in conjunction with aforesaid dynamic frequency-conversion control mode, but utilize the constant resonance frequency of frequency conversion amplitude to adjust the voltage gain of piezoelectric transformer, and the mode of duty ratio, reach the output voltage of change piezoelectric transformer and the purpose of electric current.And according to the present invention disclosed device, with the operation that can not charge continually or stop fully charging piezoelectric transformer, therefore, with respect to traditional prominent punch die formula, or pure pulse wave width modulation control mode, device of the present invention also helps to prolong the useful life of piezoelectric transformer.
Description of drawings
Fig. 1 is the circuit framework figure of first kind of preferred embodiment of the present invention;
Fig. 2 is the circuit framework figure of another kind of preferred embodiment of the present invention;
Fig. 3 is the voltage gain of piezoelectric transformer and the graph of a relation of resonance frequency;
Fig. 4 is the oscillogram of pulse-width modulation control signal;
Fig. 5 is the oscillogram corresponding to the high frequency ac signal S2 of pulse-width modulation control signal among Fig. 4;
Fig. 6 is corresponding to the voltage oscillogram of Fig. 5 medium-high frequency AC signal S2 in the secondary electrode output of piezoelectric transformer;
Fig. 7 is when turning down the brightness of cathode fluorescent tube, the oscillogram after the pulse-width modulation control signal of earlier figures 4 changes; And
Fig. 8 is corresponding to the voltage oscillogram of the pulse-width modulation control signal among Fig. 7 in the secondary electrode output of piezoelectric transformer.
Embodiment
Relevant preferred embodiment of the present invention and detailed technology content now are described with reference to the accompanying drawings as follows.
At first, see also Fig. 1, for first kind of preferred embodiment of the present invention, can be understood by the circuit framework among the figure, the light modulating device that is applied to cathode fluorescent tube 10 comprises:
One power supply unit 20 drives the required DC power supply (specification on cathode fluorescent tube 10 decide, is generally 0 volt of DC power supply to three ten-day period of hot season spy voltage) of cathode fluorescent tube 10 in order to provide;
One PWM control unit 30 with the technology export one pulse wave signal S1 of pulse-width modulation, and contains work period T with 20 outputs one of pulse wave signal S1 control power supply unit
OnAnd T
OffThe pulse-width modulation control signal, be exactly to utilize DC power supply (DC) that this pulse wave signal S1 changes power supply unit 20 outputs in brief in 0 volt (V) duty ratio with full width of cloth output (as 3.3V), its output waveform can be with reference to figure 4;
One resonance frequency control unit 40 is a kind of FREQUENCY CONTROL IC, and the pulse-width modulation control signal that power supply unit 20 is exported is tuned as a high frequency ac signal S2, and this resonance frequency control unit 40 can be in the different operating period T of pulse-width modulation control signal
OnAnd T
OffProducing high frequency ac signal S2 with different frequency f1, f2 (its output waveform can with reference to figure 5) respectively, in order to change the voltage gain of follow-up piezoelectric transformer 50, in brief, is exactly the different operating period T in the pulse-width modulation control signal
OnAnd T
OffIn automatically change the frequency f 1 of high frequency ac signal S2, f2;
One piezoelectric transformer 50, its primary electrode 51 are connected in the high frequency ac signal S2 of resonance frequency control unit 40 outputs, and high frequency ac signal S2 gain is the needed high output voltage V of driving fluorescent lamp pipe
OutWith output current I
Out, and then from secondary electrode 52 outputs, this high output voltage V
OutWith output current I
OutBe connected in the high voltage side electrode 11 of cathode fluorescent tube 10, and then it is shinny to drive cathode fluorescent tube 10; And be taken from the voltage signal of the low-voltage side electrode 12 of cathode fluorescent tube 10, and can be fed back to PWM control unit 30, the mode of the pulsewidth by adjusting pulse wave signal S1 is so that regulate the luminous intensity of cathode fluorescent tube 10.
And another feasible preferred embodiment then is to be taken from the voltage signal of the low-voltage side electrode 12 of cathode fluorescent tube 10, is fed back to resonance frequency control unit 40 (see figure 2)s, by changing high frequency ac signal S2 in the different operating period T
OnAnd T
OffIn frequency f 1, the mode of f2 so that the brightness of cathode fluorescent tube 10 is regulated.
Because the voltage gain of piezoelectric transformer 50 is except relevant with its structure (as the individual layer or the piezoelectric transformer of lamination structure), the voltage gain of its output more can be adjusted (as shown in Figure 3) by the frequency that changes its high frequency ac signal S2, for example: if when the frequency of its high frequency ac signal S2 is 54kHz its yield value 100, represent that then output voltage values from its secondary electrode 52 output will be 100 times of input voltage value of primary electrode 51, if input voltage is 3.3V in brief, then its output voltage will reach 330V;
Otherwise, if after changing the frequency of its high frequency ac signal S2 and being 58kHz, its yield value reduces to 10, represent that then output voltage values from its secondary electrode 52 output will be 10 times of input voltage value of primary electrode 51, in brief, if input voltage is 3.3V, then its output voltage will reach 33V; Therefore utilize this characteristic, the present invention to utilize the different operating period T of a resonance frequency control unit 40 in the pulse-width modulation control signal
OnAnd T
OffProduce high frequency ac signal S2 respectively with different frequency f1, f2, utilize 50 work of this high frequency ac signal S2 drive pressure piezoelectric transformer again, by adjusting the output voltage gain of piezoelectric transformer 50, and then provide a kind of under the condition of the amplitude that does not change the pulse-width modulation control signal, change the output voltage and the electric current of piezoelectric transformer 50, and then reach the purpose of the brightness of adjusting cathode fluorescent tube 10.
Traditional pulse wave width modulation control method, mainly be under fixing resonance frequency, by adjusting the duty ratio of pulse wave width modulation signal, and the tube current in the means of the amplitude of the resonance frequency control cathode fluorescent tube, and then reach the purpose of the brightness of adjusting cathode fluorescent tube, this method with the frequency that is higher than naked eyes and can discovers (＞100Hz) control the average current of cathode fluorescent tube by modulation duty cycle, thereby cathode fluorescent tube is worked under total current always.Though this mode can reach the purpose of light modulation, but can make piezoelectric transformer under charging or the situation of not charging fully, switch continually, have bad influence this useful life for piezoelectric transformer.
Shown in Fig. 4～6, being device according to the present invention carries out the working waveform figure of light modulation process to cathode fluorescent tube 10, is example with the voltage of DC power supply between 0V～3.3V.
At first, suppose cathode fluorescent tube 10 under a certain brightness, wherein the duty ratio by the pulse-width modulation control signal of resonance frequency control unit 40 output is 60%, and (that is, 60% time is for opening T as shown in Figure 4
OnBe pass T with 40% time
Off); At work period T
OnWhen (magnitude of voltage of DC power supply is 3.3V), resonance frequency control unit 40 is made as frequency f 1 frequency values (the being assumed to be 54kHz) (see figure 5) with higher voltage gain automatically, this frequency f 1 time, if the yield value 100 of piezoelectric transformer 50, represent that then output voltage values from its secondary electrode 52 output will be 100 times of input voltage value of primary electrode 51, in brief, at work period T
OnInput voltage be 3.3V, then its output voltage will reach 330V (operating voltage of cathode fluorescent tube is high more a lot of than the voltage of other light source, needs 300 to 800 volts of alternating currents usually, and depends on the length of lamp), but at work period T
OffThe time (magnitude of voltage of DC power supply is 0V), resonance frequency control unit 40 changes among the high frequency ac signal S2 automatically at work period T
OffThe frequency values with lower voltage gain (the being assumed to be 58kHz) (see figure 5) of frequency f 2, also will reduce in the relevant voltage of secondary electrode 52 outputs of piezoelectric transformer 50, its waveform as shown in Figure 6.
In the time will turning down the brightness of cathode fluorescent tube 10, can reach the purpose of turning down brightness by changing the duty ratio of pulse-width modulation control signal, (that is, 40% time is for opening T for example to change the duty ratio 40% of pulse-width modulation control signal
OnBe pass T with 60% time
Off) or other duty ratio all can reach identical effect; Its oscillogram sees also Fig. 7, and this moment at the waveform of the relevant voltage of secondary electrode 52 output of piezoelectric transformer 50 as shown in Figure 8.
In addition, the disclosed device according to the present invention can also be by changing resonance frequency f1, the f2 of different operating in the cycle, again in conjunction with the device of pulse wave width modulation, at work period T
OnAnd T
OffIn by adjusting the mode of resonance frequency f1, f2, the gain that changes piezoelectric transformer 50 is to adjust its output voltage V
OutWith output current I
OutAnd then reach the effect of the brightness (being exactly light modulation in brief) of adjusting cathode fluorescent tube 10, especially according to device of the present invention, wherein at work period T
OffThe time still have a lower high frequency ac signal S2 drive pressure piezoelectric transformer 50, cause piezoelectric transformer 50 still under the situation of charging, to operate, and can be to not causing harmful effect the useful life of piezoelectric transformer 50, in addition, it is simple also to have framework, and the wide advantage of dimming scope.
The above is the preferred embodiments of the present invention only, is not limited to the present invention, and for a person skilled in the art, the present invention can have various changes and variation.Within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within the claim scope of the present invention.
Claims (4)
1. the light modulating device of a cathode fluorescent tube (10) is characterized in that the light modulating device of described cathode fluorescent tube comprises:
One power supply unit (20) drives the required DC power supply of described cathode fluorescent tube (10) in order to provide;
One PWM control unit (30) with technology export one pulse wave signal (S1) of pulse-width modulation, and is controlled described power supply unit (20) output one with described pulse wave signal (S1) and is contained work period (T
On) and (T
Off) the pulse-width modulation control signal;
One resonance frequency control unit (40) is tuned as a high frequency ac signal with described pulse-width modulation control signal, and described resonance frequency control unit (40) is at described different operating cycle (T
On) and (T
Off) produce a high frequency ac signal (S2) respectively with different frequency (f1, f2);
One piezoelectric transformer (50) is the needed high output voltage (V of driving described cathode fluorescent tube (10) with described high frequency ac signal (S2) gain
Out) and output current (I
Out), and then it is shinny to drive described cathode fluorescent tube (10).
2. the light modulating device of cathode fluorescent tube according to claim 1 (10), the duty ratio that it is characterized in that described pulse-width modulation control signal is a type variable, in order to adjust the brightness of described cathode fluorescent tube (10).
3. the light modulating device of cathode fluorescent tube according to claim 1 (10) is characterized in that described high frequency ac signal (S2) is at different work period (T
On) and (T
Off) frequency (f1, f2) can make described piezoelectric transformer (50) have different voltage gains.
4. the light modulating device of cathode fluorescent tube according to claim 1 (10) is characterized in that described piezoelectric transformer (50) is at described work period (T
On) frequency (f1) under voltage gain, greater than at described work period (T
Off) frequency (f2) under voltage gain.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2004100375742A CN100551199C (en) | 2004-04-28 | 2004-04-28 | The light modulating device of cathode fluorescent tube |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2004100375742A CN100551199C (en) | 2004-04-28 | 2004-04-28 | The light modulating device of cathode fluorescent tube |
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| CN1691870A true CN1691870A (en) | 2005-11-02 |
| CN100551199C CN100551199C (en) | 2009-10-14 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101018439B (en) * | 2006-02-10 | 2010-08-04 | 鸿富锦精密工业（深圳）有限公司 | Discharge lamp driving device |
| CN101052259B (en) * | 2006-03-31 | 2011-09-21 | 优志旺电机株式会社 | Inert gas fluorescent lamp lighting apparatus |
| CN102760411A (en) * | 2011-04-26 | 2012-10-31 | 佛山市南海平板显示技术中心 | Piezoelectric transformer drive circuit |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102246699A (en) * | 2011-07-11 | 2011-11-23 | 北京林业大学 | Application of CCFL (cold cathode fluorescent lamp) in plant tissue culture |
-
2004
- 2004-04-28 CN CNB2004100375742A patent/CN100551199C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101018439B (en) * | 2006-02-10 | 2010-08-04 | 鸿富锦精密工业（深圳）有限公司 | Discharge lamp driving device |
| CN101052259B (en) * | 2006-03-31 | 2011-09-21 | 优志旺电机株式会社 | Inert gas fluorescent lamp lighting apparatus |
| CN102760411A (en) * | 2011-04-26 | 2012-10-31 | 佛山市南海平板显示技术中心 | Piezoelectric transformer drive circuit |
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| Publication number | Publication date |
|---|---|
| CN100551199C (en) | 2009-10-14 |
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Granted publication date: 20091014 Termination date: 20120428 |