CN101868111A - Light emitting module capable of compensating current - Google Patents

Abstract

The invention discloses a light emitting module capable of compensating current, and the light emitting module can be dimmed through a dimming circuit. The light emitting module comprises a light emitting unit and a compensation circuit. The light emitting unit comprises a voltage source, a load impedance and a level unit. Wherein the level unit has a level voltage and is changed with the dimming circuit. The compensation circuit comprises a first resistor, a first switch and a judgment unit. The first resistor is coupled to a voltage source. The first switch is coupled to the first resistor and the light emitting unit. The judging unit is coupled to the level unit and the first switch. When the level voltage is lower than the preset voltage, the judgment unit enables the first switch to be conducted, and the first resistor is connected with the load impedance in parallel.

Description

But the light emitting module of offset current

Technical field

But the invention relates to a kind of light emitting module of offset current, particularly about the undercurrent of the thyristor of the light adjusting circuit that can judge front end, and then the light emitting module that carries out the current compensation operation.

Background technology

The dimmer that can adjust lamplight brightness is all arranged on the market, in order to adjust the light and shade of light with user's demand at present.But,,, can produce the situation generation of flicker when electric current during less than certain value if when present dimmer is used in cathode fluorescent tube.When the situation of flicker when often taking place,, may make in addition the life-span that reduces cathode fluorescent tube except allowing the user feels under the weather.

Therefore, but the invention reside in the light emitting module that a kind of offset current is provided, when its light adjusting circuit that can detect front end is supplied to the undercurrent of thyristor, and then light adjusting circuit is carried out the operation of current compensation.Thus, promptly can avoid thyristor because the fluorescent tube flicker that undercurrent causes abnormal beating (bouncing) to be caused.

Summary of the invention

But the present invention discloses a kind of light emitting module of offset current, and light emitting module can carry out light modulation by light adjusting circuit.Light emitting module comprises luminescence unit and compensating circuit.Luminescence unit comprises voltage source, load impedance and level-cell.Wherein level-cell has level voltage, and can change along with light adjusting circuit.Compensating circuit comprises first resistance, first switch and judging unit.First resistance couples voltage source.First switch couples first resistance and luminescence unit.Judging unit is coupled to the level-cell and first switch.Wherein when level voltage during less than predetermined voltage, judging unit makes first switch conduction, makes first resistance in parallel with load impedance.

Compared to known technology, but the light emitting module of offset current of the present invention, and its light adjusting circuit that can detect front end is supplied to the undercurrent phenomenon of thyristor, and then light adjusting circuit is carried out the operation of current compensation.Thus, promptly can avoid thyristor because undercurrent is closed, but be opened the scintillation that during this switch, is produced by voltage triggered.

Can be about the advantages and spirit of the present invention by following detailed Description Of The Invention and appended graphic being further understood.

Description of drawings

But Fig. 1 is the calcspar that illustrates according to the light emitting module of the offset current of a specific embodiment of the present invention.

Fig. 2 is the circuit diagram that illustrates the light adjusting circuit among Fig. 1.

Fig. 3 is the internal circuit schematic diagram that illustrates the luminescence unit among Fig. 1.

Fig. 4 is the internal circuit schematic diagram that illustrates the compensating circuit among Fig. 1.

[main element label declaration]

3: light emitting module 32: luminescence unit

322: rectification circuit 323: drive circuit

324: transformer 325: fluorescent tube

326: level-cell 34: compensating circuit

342: the first resistance of 341: the first switches

343: 3431: the one MOSFET of judging unit

3432: the second resistance I ₃₁, I ₄₁: electric current

4: light adjusting circuit Z ₁, Z ₂, Z _Total: impedance

T41: exchange thyristor VL: level voltage

A, B, C, D: contact

Embodiment

See also Fig. 1.But Fig. 1 is the calcspar that illustrates according to the light emitting module 3 of the offset current of a specific embodiment of the present invention.As shown in Figure 1, light emitting module 3 is connected to light adjusting circuit 4, and light emitting module 3 can carry out light modulation by light adjusting circuit 4.In other words, light adjusting circuit 4 can be adjusted the light that light emitting module 3 sent and control light and shade.Wherein light emitting module 3 comprises luminescence unit 32 and compensating circuit 34.And light emitting module 3 has impedance Z _TotalLuminescence unit 32 has impedance Z ₁, compensating circuit 34 has impedance Z 2.

In this embodiment, luminescence unit 3 comprises load impedance Z ₁, voltage node N ₁, rectification circuit 322, drive circuit 323, transformer 324, fluorescent tube 325 and level-cell 326.

Rectification circuit 322 couples voltage node N ₁, drive circuit 323 and level-cell 326.Drive circuit 323 is coupled to transformer 324.Transformer 324 is coupled to fluorescent tube 325.Wherein drive circuit 323 can be used to produce pulse width modulation (Pulse Width Modulation, PWM) signal.Transformer 324 can be with pulse width modulating signal being converted to string ripple signal.

Especially, fluorescent tube 325 can comprise cold cathode fluorescent lamp (Cold Cathode Fluorescence Lamp, CCFL), still, the cold cathode fluorescent lamp that fluorescent tube 325 comprised does not limit its external form, quantity, length etc. especially, is to be ordered according to its hobby voluntarily by the designer fully.In addition, compensating circuit 34 is coupled to rectification circuit 322 and level-cell 326.

Please consult Fig. 1 again and consult Fig. 2, Fig. 3 and Fig. 4 in the lump.Fig. 2 is the circuit diagram that illustrates the light adjusting circuit 4 among Fig. 1.Fig. 3 is the internal circuit schematic diagram that illustrates the luminescence unit 32 among Fig. 1.Fig. 4 is the internal circuit schematic diagram that illustrates the compensating circuit 34 among Fig. 1.As Fig. 1, Fig. 2, Fig. 3 and shown in Figure 4, light adjusting circuit 4 comprises interchange thyristor T ₄₁, and exchange thyristor T ₄₁On have electric current I ₄₁Especially, the A of Fig. 2 point and B point are to be connected with A point and the B point of Fig. 3.And exchange thyristor T ₄₁Can be used to change the angle of flow (fire angle) that inputs to luminescence unit 32.

The rectification circuit 322 of luminescence unit 32 can be a bridge rectifier, but not especially as limit.And rectification circuit 322 has electric current I ₃₁, and electric current I ₃₁This equals electric current I haply ₄₁Level-cell 326 can be a resistance, but not especially as limit.

In this embodiment, compensating circuit 34 comprises first switch 341, first resistance 342 and judging unit 343.First switch 341 couples first resistance 342.First switch 341 can be MOSFET, but not especially as limit.First resistance 342 couples voltage node N ₁Wherein, first resistance 342 can comprise at least more than one the parallel with one another or series connection of resistance, but not especially as limit, the purpose of the resistance that is comprised in first resistance 342 being carried out serial or parallel connection is the heat energy that is to disperse the resistance generation.

In this embodiment, judging unit 343 is to be coupled to C point and D point among Fig. 3 respectively by C point and D point, and in other words, judging unit 343 is coupled to the level-cell 326 and first switch 341.In addition, judging unit 343 comprises a MOSFET 3431 and second resistance 3432.The one MOSFET3431 is electrically connected to level-cell 326 and second resistance also 3432.Second resistance 3432 is electrically connected to reference power supply V ₁Especially, reference power supply V ₁Can be 15 volts, but not as limit.

Above-mentioned with the annexation of each block functional diagram of the present invention, also have each interior important spare part of its calcspar and the annexation between each spare part to be described in detail.And following will be especially at the circuit operation of reality of the present invention and be described in detail.

Please consult Fig. 1, Fig. 2, Fig. 3 and Fig. 4 more in the lump, what at first will describe is electric current I ₃₁(for example: 0.075A) be greater than the situation of predetermined value.The flow through electric current I of level-cell 326 ₃₁Can produce level voltage VL, work as electric current I ₃₁During greater than predetermined value (for example 0.075A), level voltage VL can make first switch 341 keep closed condition.When first switch 341 cut out, first resistance 342 was can any influence and effect not arranged to entire circuit.In other words, the impedance Z of light emitting module 3 _TotalCan equal the impedance Z of luminescence unit ₁

Then, will be at electric current I ₃₁Operational circumstances little, the circuit when predetermined value is discussed.Work as electric current I ₃₁Be subjected to the angle of flow influence of light adjusting circuit 4 and during less than 0.075A (please note once more, be not defined as 0.075A especially), and then make level voltage VL also and then diminish.Therefore, when level voltage VL diminishes, just across the voltage decreases of a MOSFET 3431.If the value of level voltage VL is not enough to allow a MOSFET 3431 conductings, then a MOSFET 3431 is closed.After a MOSFET 3431 is closed, the switch 341 of winning is switched on.In other words, first switch 341 is opened exactly.Therefore, first resistance 342 is and voltage node N ₁Produce in parallel.

See also Fig. 1, as shown in Figure 1, when first resistance 342 has had and voltage node N ₁During in parallel effect, can regard compensating circuit 34 as compensating resistance Z is provided ₂Therefore, the load impedance Z of luminescence unit 32 ₁Will with compensating resistance Z ₂In parallel.And by Z _TotalBe defined as light emitting module 3 total impedances.So can learn, in the case, Z _TotalBe load impedance Z ₁Shunt compensation resistance Z ₂Then as can be known, the total impedance Z of light emitting module 3 by Ohm's law _TotalCan be less than load resistance Z ₁Therefore calculate according to Ohm's law again, when voltage fixedly the time, resistance decreasing then electric current can become big.So can learn electric current I ₃₁Promptly can increase.Electric current I ₃₁During increase, can thyristor T will be made ₄₁Maintain the state of normal unlatching, can not produce beat (bouncing), and then make fluorescent tube can not produce scintillation.

Compared to known technology, but the light emitting module of offset current of the present invention, and it can detect the not enough phenomenon of electric current of light adjusting circuit, and then light adjusting circuit is carried out the operation of current compensation.Promptly can avoid thyristor because the upset operation that undercurrent produced so once.

By the above detailed description of preferred embodiments, be to wish to know more to describe feature of the present invention and spirit, and be not to come category of the present invention is limited with above-mentioned disclosed preferred embodiment.On the contrary, its objective is that hope can contain in the category of claim scope of being arranged in of various changes and tool equality institute of the present invention desire application.

Claims (6)

1. A light-emitting module capable of compensating current, the light-emitting module can be dimmed through a dimming circuit, and the light-emitting module includes: A lighting unit having a load impedance, the lighting unit comprising: light tube; voltage nodes; and A level unit, wherein the level unit has a level voltage, and the level voltage changes with the dimming circuit; Compensation circuit, including: a first resistor coupled to the voltage node; a first switch coupled to the first resistor; and a judging unit, coupled to the level unit and the first switch; Wherein when the level voltage is lower than the predetermined voltage, the judging unit turns on the first switch, so that the first resistor is connected in parallel with the load impedance. 2. The current-compensable light-emitting module according to claim 1, the light-emitting unit further comprising: a rectifier circuit, coupled to the voltage node and the level unit; a drive circuit, coupled to the rectification circuit, for generating a pulse width modulation signal; and a transformer, coupled to the drive circuit and the lamp tube; 3. The current-compensated light-emitting module according to claim 2, wherein the lamp comprises a cold cathode lamp. 4. The current-compensated light-emitting module according to claim 1, wherein the level unit is a resistor. 5. The current-compensable light-emitting module according to claim 1, wherein the judging unit comprises: a second resistor electrically connected to the reference power supply; and The first MOSFET is electrically connected to the level unit and the second resistor. 6. The current-compensated light-emitting module according to claim 1, wherein the dimming circuit comprises an AC silicon-controlled rectifier for changing the conduction angle input to the light-emitting unit.

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