CN2932912Y

CN2932912Y - Light tube driving circuit

Info

Publication number: CN2932912Y
Application number: CNU2006200030436U
Authority: CN
Inventors: 李亿胜; 林朝荣
Original assignee: Darfon Electronics Corp
Current assignee: Darfon Electronics Corp
Priority date: 2006-01-23
Filing date: 2006-01-23
Publication date: 2007-08-08
Anticipated expiration: 2016-01-23

Abstract

The utility model relates to a lamp driving circuit, comprising a transformer, wherein a secondary side coupling of the transformer is connected with an optical coupler, and the primary side coupling of the transformer is connected with an output end of a control circuit. When the optical coupler does not conduct, a return circuit protective circuit is started to make the output value of the control circuit reduce to realize the function of protecting the lamp driving circuit.

Description

Lamp tube drive circuit

Technical field

The utility model is relevant a kind of lamp tube drive circuit, refers to a kind of lamp tube drive circuit of the U of driving type pipe especially.

Background technology

Press, discharge lamp (Discharge Lamp) often is applied to Backlight For Liquid Crystal Display Panels (Backlight), for example: cold-cathode fluorescence lamp (Cold Cathode Fluorescent Lamp, CCFL) be wherein a kind of, its operating voltage can reduce immediately after this cold-cathode fluorescence lamp conducting, its operating voltage is about the size (being about 1000V) of trigger voltage 1/3, but its operating current is but very extensive, all can drive from 6mA to 500mA, and its operating frequency is about about 30KHz to 100KHz.

Above-mentioned discharge lamp has the characteristic of negative impedance, its equiva lent impedance can reduce along with the increase of input power, power supply or power are to the circuit of fluorescent tube, the stability that promptly so-called general converter (Inverter) must provide may command AC power and feedback circuit to come holding circuit also need have the function that load is adjusted on the other hand.

See also shown in Figure 1, it is the known circuit framework figure that utilizes Circuit Fault on Secondary Transformer to be connected with fluorescent tube, wherein in traditional circuit, cause the unbalanced phenomenon of fluorescent tube 12 two ends input currents because of parasitic capacitance, be 6mA for example in 13 received currents of fluorescent tube 12 first contacts, in 14 received currents of fluorescent tube 12 second contacts is 12mA, find that obviously first contact 13 and second contact 14 have the drop of 6mA and can get, the unbalanced problem of this contact will directly have influence on transformer, cause the phenomenon of excessive temperature differentials, simultaneously transformer 11 and other element are damaged easily.Simultaneously, if fluorescent tube 12, when especially the current difference at the two ends of U type pipe is excessive, very easily causes these fluorescent tube 12 brightness irregularities (being applied on the panel more obvious) and be easy to burn the variety of problems of (promptly representing the life-span of fluorescent tube also thereupon to shorten), therefore remain to be engaged in this journey dealer and overcome.

Summary of the invention

Based on the disappearance that solves the above prior art; the utility model is a kind of lamp tube drive circuit; main purpose is for to utilize optical coupler (Photo-coupler) to be coupled to the low-pressure end of two secondary sides of transformer; so that two low-pressure ends of secondary side form imaginary short; optical coupler couples open loop protection circuit (Open Loop Protection; OLP); when fluorescent tube forms open circuit; can cause open loop protection circuit current potential to be drawn high; the value of feedback that is sent to control circuit (controller) is reduced; the output valve of control circuit is reduced, to reach the function of guard lamp tube drive circuit.

For achieving the above object, first embodiment of lamp tube drive circuit of the present utility model, its framework comprises:

Transformer has primary side, first secondary side and second secondary side;

Optical coupler is coupled to this first secondary side and this second secondary side;

The open loop protection circuit couples optocoupler and device;

Fluorescent tube couples the high-pressure side of first primary side and second secondary side;

Control circuit has output and feedback end, and output couples the primary side of transformer, and feedback end then couples the open loop protection circuit;

When this not conducting of optical coupler, open loop protection circuit current potential is drawn high, and the output valve of control circuit output is reduced, to reach the function of guard lamp tube drive circuit.

For achieving the above object, second embodiment of lamp tube drive circuit of the present utility model, its framework includes:

Transformer, this transformer have primary side, first secondary side and second secondary side;

The protection transformer is coupled to this first secondary side and this second secondary side;

The open loop protection circuit couples the protection transformer;

Control circuit has output and feedback end, and output couples the primary side of transformer, and provides input signal to transformer, and feedback end couples the open loop protection circuit;

When the magnitude of voltage of the secondary side of protecting transformer reduced, open loop protection circuit current potential was drawn high, and the output valve of control circuit was reduced, to reach the function of guard lamp tube drive circuit.

For further the utility model being had more deep explanation, be that the Ji can be benefited in censorship to some extent to your juror by following diagram, figure number explanation and detailed description of the invention.

Description of drawings

Fig. 1 is the known circuit framework figure that utilizes Circuit Fault on Secondary Transformer to be connected with fluorescent tube.

Fig. 2 is first embodiment of lamp tube drive circuit of the present utility model.

Fig. 3 is second embodiment of lamp tube drive circuit of the present utility model.

[main element explanation]

11～transformer

12～fluorescent tube

L～fluorescent tube

13～the first contacts

14～the second contacts

20～lamp tube drive circuit

30～lamp tube drive circuit

21～transformer

22～optical coupler

23～resistance

24～diode

25～control circuit

26～open loop protection circuit

31～transformer

32～protection transformer

33～filter circuit

35～open loop protection circuit

36～control circuit

P～primary side

S1～secondary side

S2～secondary side

Embodiment

Now cooperate following graphic explanation detailed structure of the present utility model, and annexation, be beneficial to expensive careful committee and do a understanding.

See also shown in Figure 2ly, be first embodiment of lamp tube drive circuit of the present utility model, lamp tube drive circuit 20 comprises:

Transformer 21, this transformer 21 is for having primary side P, the first secondary side S1 and the second secondary side S2;

Optical coupler 22 is coupled to the low-pressure end of this first secondary side S1 and this second secondary side S2;

Open loop protection circuit 25 couples optocoupler and device 22;

Fluorescent tube L couples the high-pressure side of the first primary side S1 and the second secondary side S2;

Control circuit 25 has output (output) and feedback end FB, and output couples the primary side P of transformer 21, and feedback end FB couples open loop protection circuit 26;

When these optical coupler 22 not conductings, open loop protection circuit 25 current potentials are drawn high, and the output valve of control circuit are reduced, to reach the function of guard lamp tube drive circuit.

The motion flow of the lamp tube drive circuit of this first embodiment is:

The input voltage of transformer 21 primary sides is via two secondary side (S1; S2) after the induction; be converted into high voltage (being about 1000V); and optical coupler (Photocoupler) 22 is coupled to first secondary side S1 of transformer 21 and the low-pressure end of the second secondary side S2; resistance R 1 can be as the function of shunting and current limliting; in order to protect two light-emitting diode D1; therefore optical coupler 22 can be in positive half cycle of voltage and negative half period conducting respectively; to produce low-voltage AC; and enough become the switch of noncontact form with the receiving crystal pipe, and has buffer action by the light-emitting diode D1 of optical coupler 22.After optical coupler 22 conductings; can make A node voltage in the open loop protection circuit 26 near the magnitude of voltage of 5V; when open circuit (Open) situation appears in fluorescent tube L; the magnitude of voltage of open loop protection circuit 260 is drawn high; the output valve of control circuit 25 is reduced; and then reach the protection drive circuit, avoid causing and burn or the situation of other damage.

See also shown in Figure 3ly, be second embodiment of lamp tube drive circuit of the present utility model, lamp tube drive circuit 30 comprises:

Protection transformer 32 is coupled to this first secondary side S1 and this second secondary side S2;

Open loop protection circuit 35 couples protection transformer 32;

Control circuit 36 has output (output) and feedback end FB, and output couples the primary side P of transformer 21, and feedback end FB couples open loop protection circuit 26;

When the secondary side of protection transformer 32 was not sensed voltage, open loop protection circuit 25 current potentials were drawn high, and the output valve of control circuit 36 were reduced, to reach the function of guard lamp tube drive circuit.

The operating process of the lamp tube drive circuit of this second embodiment is: the framework that Fig. 3 disclosed is approximately identical with Fig. 2, and its difference framework is to be above-mentioned optical coupler 22 displacements becoming protection transformer 32, and utilizes resistance capacitance (R ₁, C ₁) institute's formation filter circuit 33; when the voltage of the secondary side of protecting transformer 32 reduces, the current potential of this open loop protection circuit 35 is drawn high, and then the output valve of control circuit 36 is reduced; and reach the guard lamp tube drive circuit, produce and burn or the situation of other damage.

By above-mentioned Fig. 2,3 exposure; can understand the utility model really can optical coupler or transformer, cooperates the open loop protection circuit, to reach the purpose of guard lamp tube drive circuit; avoid producing and burn or the situation of other damage, really have different traditional protection framework and have better protectiveness.

In sum, architectural feature of the present utility model and each embodiment disclose all in detail, and can fully demonstrate the utility model case all dark well-off progressive of executing on purpose and effect, the value that has industry, and be utilization not seen before on the market at present, spiritual described according to Patent Law, the utility model case meets the important document of patent of invention fully.

The above person only, it only is preferred embodiment of the present utility model, when can not with the scope implemented of qualification the utility model, promptly the equalization of being done according to the utility model claim scope generally changes and modifies, all should still belong in the scope that the utility model patent contains, sincerely asking your juror's explicit example for reference, and pray Hui Zhun, is that institute is to praying.

Claims

1. lamp tube drive circuit is characterized in that comprising:

Optical coupler is coupled to the low-pressure end of this first secondary side and this second secondary side;

Fluorescent tube couples the high-pressure side of this first secondary side and this second secondary side;

The open loop protection circuit couples this optical coupler; And

Control circuit has output and feedback end, and this output couples the primary side of transformer, and this feedback end couples this open loop protection circuit;

When this not conducting of optical coupler, the current potential of this open loop protection circuit is drawn high, and the output valve of this control circuit reduces, to reach the function of guard lamp tube drive circuit.

2. lamp tube drive circuit according to claim 1, wherein this fluorescent tube is a cold cathode fluorescent lamp.

3. lamp tube drive circuit according to claim 2, wherein this fluorescent tube is a U type pipe.

4. lamp tube drive circuit according to claim 1 wherein also comprises diode and resistance, this resistance and this diode parallel connection, and be coupled to this transformer between this optical coupler.

5. lamp tube drive circuit is characterized in that comprising:

Protect transformer, be coupled to the low-pressure end of this first secondary side and this second secondary side;

The open loop protection circuit couples this protection transformer; And

When this protected the voltage of the secondary side of transformer to reduce, this open loop protection circuit current potential was drawn high, and the output valve of this control circuit was reduced, to reach the function of guard lamp tube drive circuit.

6. lamp tube drive circuit according to claim 5, wherein this fluorescent tube is a cold cathode fluorescent lamp.

7. lamp tube drive circuit according to claim 6, wherein this fluorescent tube is a U type pipe.

8. lamp tube drive circuit according to claim 5 wherein also comprises filter circuit, and this filter circuit is coupled between this protection transformer and this open loop protection circuit.

9. lamp tube drive circuit according to claim 5, wherein this protection transformer is 1: 1 a transformer.