CN201256476Y - Multi-lamp tube driving device - Google Patents

Abstract

The utility model provides a be applied to many fluorescent tubes drive arrangement of high pressure input for drive many fluorescent tubes. The multi-lamp driving device comprises a DC-AC converter, an isolation/step-down transformer, a plurality of step-up transformers and a plurality of resonant circuits. The DC-to-AC converter receives a DC voltage signal, converts the DC voltage signal into an AC voltage signal and outputs the AC voltage signal. The primary side coil of the isolation/step-down transformer is coupled to the output of the dc-to-ac converter. The primary side coils of all the step-up transformers are connected in series and then bridged with the secondary side coils of the isolation/step-down transformers. Each resonant circuit is coupled between the secondary side coil of the corresponding step-up transformer and the corresponding lamp tube. The utility model discloses can improve the condenser and need be able to bear or endure extremely high pressure and be difficult to choose for use, transformer secondary side coil's wire winding line footpath rather than producing and be used in resonant circuit's leakage inductance's matching problem, and the voltage signal's of drive fluorescent tube wave form can not the distortion.

Description

Multi-lamp driver

technical field

The utility model relates to a lamp tube driving device, in particular to a multi-lamp tube driving device.

Background technique

For transmissive or transflective liquid crystal displays, since the liquid crystal panel itself does not have luminous properties, it is necessary to add a backlight for lighting on the liquid crystal panel. Currently, cold cathode fluorescent lamps (CCFL) It is the most common choice as the backlight source of the LCD panel. As the application scope of LCD gradually expands from portable small and medium-sized products (such as mobile phones) to large panels (such as TVs), and even towards ultra-large video applications, the backlight area required by LCD panels also increases accordingly. , the trend of using multiple lamps is inevitable.

FIG. 1 is a circuit diagram of a conventional multi-lamp driving device, wherein the lamps are, for example, cold cathode fluorescent lamps (CCFL). Please refer to FIG. 1 , the multi-lamp driving device 100 includes a DC-to-AC converter 110 , a step-up transformer 120 , a resonant circuit 130 and four isolation transformers 141 - 144 . The DC voltage signal V _DC is input to the DC-to-AC converter 110 . The DC-to-AC converter 110 may be, for example, a full-bridge inverter (inverter), which converts the DC voltage signal V _DC into an AC square wave voltage signal V _RECT and then inputs it to the primary side coil 120p of the step-up transformer 120 . By designing the turn ratio of the primary side coil 120p and the secondary side coil 120s of the step-up transformer 120 to be 1:n, the voltage signal output from the secondary side coil 120s is n of the voltage signal input from the primary side coil 120p times, n is greater than 1. The AC square wave voltage signal V _RECT is boosted by the step-up transformer 120 and then input into the resonant circuit 130 .

The resonant circuit 130 is a structure of series resonance and parallel load, that is, the inductor 131 and the capacitor 132 are coupled in series and then connected across the secondary side coil 120s of the step-up transformer 120, and the capacitor 132 is coupled to the load in parallel. In this embodiment The medium load is four lamp tubes 401-404. The capacitor 132 is coupled in parallel to the four lamp tubes 401-404 by connecting the primary side coils 141p-144p of the four isolation transformers 141-144 in series and then connecting them across the capacitor 132, while the four isolation transformers 141 The secondary coils 141 s - 144 s of - 144 are respectively coupled to the respective lamp tubes 401 - 404 , wherein the turn ratio of the isolation transformers 141 - 144 is 1:1. The resonant circuit 130 can provide the high starting voltage and stable lamp current required for starting the lamp tubes 401-404, wherein the capacitor 132 can also filter the voltage signal, so that the waveform of the AC square wave voltage signal V _RECT becomes An AC sine wave voltage signal V _AC that approximates a sine wave.

FIG. 2 is a circuit diagram of another conventional multi-lamp driving device. Please refer to FIG. 1 and FIG. 2 at the same time. The biggest difference between the multi-lamp driving device 100 shown in FIG. 1 and the multi-lamp driving device 200 shown in FIG. 2 lies in the transformer. The driving device 100 first uses the turn ratio (1:n) of the step-up transformer 120 to boost the voltage, and then uses the resonant circuit 130 to resonate the working voltage required by the lamp tubes 401-404, and then through the series isolation transformers 141-144 to drive the lamp tubes 401-404 while providing isolation. The driving device 200 first uses the isolation transformer 220 to provide isolation, and then uses the resonant circuit 130 to resonate a voltage, and then the voltage is boosted to the lamp by the turn ratio (1:n) of the step-up transformers 241-244. The working voltage required by tubes 401-404.

Although these existing driving devices 100 and 200 can be applied to high-voltage input multi-lamp devices, they still have some disadvantages. Taking the driving device 100 as an example, since the working voltage required by a cold cathode fluorescent lamp (CCFL) is hundreds of volts, the voltage required for lighting is as high as more than 1,000 volts, and the primary side coils of the isolation transformers 141-144 141p-144p are connected in series, so the voltage across the capacitor 132 is equal to the sum of the working voltages required by the four lamp tubes 401-404, which is about 1,000 to 4,000 volts. A certain degree of difficulty arises in the selection, especially when more lamp tubes are driven, the higher the voltage across the capacitor 132 will be.

In the case of the drive device 200, since the resonant circuit 130 resonates, the current of the secondary side coil 220s of the isolation transformer 220 will increase, so the winding diameter of the secondary side coil 220s of the isolation transformer 220 should not be too large when designing. Small. If the inductor 131 in the resonant circuit 130 is not an external inductor, but is provided by the leakage inductance of the secondary side of the isolation transformer 220, then the inductance value of the resonant circuit 130 to the inductor 131 (that is, the isolation transformer 220 Secondary side leakage inductance) requirements will meet the requirements of the secondary side coil 220s of the isolation transformer 220 that the diameter of the winding wire used can not be too small, and there will be certain difficulty; moreover, the AC sine wave across the capacitor 132 The voltage signal V _AC directly drives the lamp tubes 401-404 after being boosted by the step-up transformers 241-244. However, since the step-up transformers 241-244 use a high turn ratio to achieve the step-up function, an excessively high turn ratio will cause Due to certain leakage inductance and stray capacitance, the waveforms of the voltage signals directly output to the lamp tubes 401 - 404 may be distorted, causing the distortion factor of the lamp tubes to increase.

Contents of the invention

The purpose of this utility model is to propose a multi-lamp drive device, which is suitable for multi-lamp devices with high-voltage input, can improve the problem that the aforementioned capacitor needs to withstand extremely high voltage and is not easy to select, and also improve the aforementioned secondary side of the transformer. The winding wire diameter of the coil matches the leakage inductance generated and used in the resonant circuit, and the waveform of the voltage signal driving the lamp will not be distorted.

In order to achieve the above and other objectives, the utility model provides a multi-lamp driving device for driving multiple lamps, such as CCFLs. The multi-lamp driving device includes a DC to AC converter, an isolation/step-down transformer, multiple step-up transformers and multiple resonant circuits. The DC-to-AC converter receives a DC voltage signal, converts the DC voltage signal into an AC voltage signal, and outputs it. The primary coil of the isolation/step-down transformer is coupled to the output of the DC-to-AC converter. The primary side coils of all step-up transformers are coupled in series and connected across the secondary side coil of the isolation/step-down transformer. Each resonant circuit is coupled between the corresponding secondary coil of the step-up transformer and the corresponding lamp.

Compared with the prior art, the multi-lamp driving device of the present invention uses an isolation/step-down transformer to provide isolation/step-down, and then boosts the voltage through a plurality of step-up transformers coupled in series, so there is no isolation / The matching problem of the winding wire diameter of the secondary side coil of the step-down transformer and the leakage inductance used in the resonant circuit. Furthermore, these step-up transformers are respectively coupled to the corresponding resonant circuits and then coupled to the corresponding lamp tubes, so there will be no problem of distortion of the AC signal driving the lamp tubes, and there will be no need for capacitors in the resonant circuits. It is not easy to choose the problem of extremely high pressure resistance.

Description of drawings

Fig. 1 is a kind of circuit diagram of existing multi-lamp driving device;

Fig. 2 is the circuit diagram of another kind of existing multi-lamp driving device;

3 is a circuit diagram of a multi-lamp driving device according to an embodiment of the present invention;

Fig. 4 is an equivalent circuit diagram of a step-up transformer, a resonant circuit and a lamp in the multi-lamp drive device shown in Fig. 3;

FIG. 5 is a circuit diagram of adding a power factor correction circuit to the front end of the multi-lamp driving device shown in FIG. 3 .

Explanation of reference signs: 100, 200-multi-lamp driving device; 110-DC to AC converter; 120-step-up transformer; 120p-primary side coil of step-up transformer; 120s-secondary side coil of step-up transformer; 130-Resonant circuit; 131-Inductor; 132-Capacitor; 141, 142, 143, 144-Isolation transformer; 141p, 142p, 143p, 144p-Primary coil of isolation transformer; 141s, 142s, 143s, 144s-Isolation transformer 220-isolation transformer; 220p-primary side coil of isolation transformer; 220s-secondary side coil of isolation transformer; 241, 242, 243, 244-boost transformer; 300-multi-lamp drive device; 310-DC to AC converter; 320-isolation/step-down transformer; 320p-primary side coil of isolation/step-down transformer; 320s-secondary side coil of isolation/step-down transformer; 331, 332, 333, 334-liter Voltage transformer; 331p, 332p, 333p, 334p- primary side coil of step-up transformer; 331s, 332s, 333s, 334s- secondary side coil of step-up transformer; 341, 342, 343, 344- resonant circuit; 401, 402 , 403, 404-light tube; 510-mains; 520-bridge rectifier; 530-power factor correction circuit; V _DC -DC voltage signal; V _RECT , V _RECT -AC voltage signal (square wave); V _AC , V _AC1 , V _AC2 , V _AC3 , V _AC4 - AC voltage signal (sine wave); L - inductance value; C - capacitance value; R _L - lamp resistance value.

Detailed ways

The above-mentioned and other technical features and advantages of the present utility model will be described in more detail below in conjunction with the accompanying drawings.

3 is a circuit diagram of a multi-lamp driving device according to an embodiment of the present invention. This driving device is suitable for use in multi-lamp devices requiring high voltage input such as large-sized liquid crystal displays, where the lamps are, for example, cold Cathode fluorescent lamp (CCFL), but not limited thereto; for example, the lamp can also be a metal halide lamp or a sodium vapor lamp, etc. Referring to FIG. 3 , the multi-lamp driving device 300 includes a DC-to-AC converter 310 , an isolation/step-down transformer 320 , multiple step-up transformers 331 - 334 and multiple resonant circuits 341 - 344 .

The DC-to-AC converter 310 receives a DC voltage signal V _DC and converts the DC voltage signal V _DC into an AC voltage signal V _RECT for output. Generally speaking, the waveform of the AC voltage signal V _RECT is a square wave. There are many implementations of the DC-to-AC converter 310 , such as full-bridge, half-bridge or push-pull (push-pull) inverters, but not limited thereto.

The isolation/step-down transformer 320 has a primary coil 320p and a secondary coil 320s, and the primary coil 320p is coupled to the output of the DC-to-AC converter 310 (ie, the AC voltage signal V _RECT ). In addition, the isolation/step-down transformer 320 can be designed as an isolation transformer or a step-down transformer as required. For example, the turn ratio of the two coils 320p and 320s of the isolation/step-down transformer 320 is m:1, m is greater than or equal to 1, if m is equal to 1, it is an isolation transformer; if m is greater than 1, it is a step-down transformer. This is because when the number of lamp tubes driven by the multi-lamp tube driving device 300 is small, the required voltage signal on the secondary side of the isolation/step-down transformer 320 will be _relatively small. The provided voltage signal will be too large and the converted AC voltage signal V _RECT will be too large, so the isolation/step-down transformer 320 is required to step down the AC voltage signal V _RECT .

Each step-up transformer 33i has a primary coil 33ip and a secondary coil 33is, i can be 1, 2, 3 or 4; for example, the boost transformer 331 has a primary coil 331p and a secondary coil 331s. The primary-side coils 331p-334p of all step-up transformers 331-334 are connected in series and connected across the secondary-side coil 320s of the isolation/step-down transformer 320, so the secondary side of the isolation/step-down transformer 320 The AC voltage signal V _RECT output by the coil 320s will be divided to the primary side coils 331p - 334p of the step-up transformers 331 - 334 . By designing the turn ratio of the step-up transformers 331-334 to be 1:n, each voltage signal output from the secondary coil 33is is n times the voltage signal input from the primary coil 33ip.

Each resonant circuit 34i is coupled between the secondary side coil 33is of a corresponding step-up transformer 33i and the corresponding lamp tube 40i; for example, the resonant circuit 341 is coupled to the secondary side coil 331s of the step-up transformer 331 and the lamp between tube 401. Here, the resonant circuit 34i can be designed as the resonant circuit 130 shown in FIG. The secondary coil 33is of the step-up transformer 33i, and wherein the capacitor is coupled to the corresponding lamp tube 40i; for example, the resonant circuit 341 includes an inductor and a capacitor, and the inductor and the capacitor are coupled in series connected to and across the secondary coil 331s of the step-up transformer 331 , and wherein the capacitor is coupled to the light tube 401 . The resonant circuit 34i can provide the high start-up voltage and stable lamp current required when the lamp 40i is started, and the capacitor therein also has the function of filtering the voltage signal, which can make the AC voltage received by the resonant circuit 34i The waveform of the signal changes from a square wave to an AC voltage signal V _ACi that approximates a sine wave.

FIG. 4 is an equivalent circuit diagram of the step-up transformers 331 - 334 , the resonant circuits 341 - 344 and the lamps 401 - 404 in the multi-lamp driving device 300 shown in FIG. 3 . Please refer to FIG. 4 , assuming that the step-up transformers 331-334 are all the same, so the primary side coils 331p-334p are all the same, and the turn ratio of the two coils 33ip and 33is of each step-up transformer 33i is 1:n; In addition, it is assumed that the resonant circuits 341-344 all include an inductor (with an inductance of L) and a capacitor (with a capacitance of C), and the resistances of the lamps 401-404 are _RL . Since the primary side coils 331p-334p are all the same, the AC voltage signal V _RECT' will be equally distributed to these primary side coils 331p-334p, that is, the cross voltage of each primary side coil 33ip is V _RECT /4. Furthermore, the inductance value of the resonant circuits 341-344 viewed from the primary side of the step-up transformers 331-334 is L/n ² , the capacitance value is C×n ² , and the resistance value of the lamp tubes 401-404 is R _L /n ² . Therefore, for each lamp tube 40i, its equivalent circuit is shown in the right diagram of FIG. 4 .

Since the rated power of a large-sized LCD panel must be higher than 75W, it must comply with specific power current harmonic specifications, such as EN61000-3-2 for European regulations, IEEE519 for American regulations, and so on. The power factor correction technology can eliminate the low-frequency current harmonics generated by the AC-to-DC converter at the front end of the power supply, reduce the starting current surge, fundamentally improve the use efficiency of electric energy and reduce power pollution, and then meet the specific power current Harmonic Specifications. Please refer to FIG. 5, which is to add a bridge rectifier 520 and a power factor correction circuit 530 between the multi-lamp driving device 300 and the mains 510 shown in FIG. Pollution, thereby complying with specific mains current harmonic specifications.

To sum up, because the multi-lamp driving device of the present invention uses the isolation/step-down transformer to provide isolation and/or step-down, and then boosts the voltage through a plurality of step-up transformers coupled in series, there will be no current problems. There is a problem of matching the winding wire diameter of the secondary side coil of the medium transformer with the leakage inductance generated and used in the resonant circuit. Furthermore, these step-up transformers are respectively coupled to the corresponding resonant circuits and then coupled to the corresponding lamp tubes, so there will be no problem of distortion of the AC signal driving the lamp tubes in the prior art, and there will be no existing problems. The capacitor in the medium resonant circuit needs to withstand extremely high voltage and is not easy to choose.

The above description is only illustrative of the present utility model, rather than restrictive. Those of ordinary skill in the art understand that many modifications and changes can be made without departing from the spirit and scope defined by the following appended claims. , or equivalent, but all will fall within the protection scope of the present utility model.

Claims (8)

1. A multi-lamp driving device for driving multiple lamps, characterized in that it includes: A DC-to-AC converter for receiving a DC voltage signal, and converting the DC voltage signal into an AC voltage signal for output; An isolation/step-down transformer having a primary side coil and a secondary side coil, the primary side coil of the isolation/step-down transformer is coupled to the output of the DC-to-AC converter; A plurality of step-up transformers, each step-up transformer has a primary side coil and a secondary side coil, the primary side coils of the plurality of step-up transformers are coupled in series and connected across the secondary side of the isolation/step-down transformer coils; and A plurality of resonant circuits, each resonant circuit is coupled between the corresponding secondary side coil of the step-up transformer and the corresponding lamp tube. 2. The multi-lamp driving device according to claim 1, wherein each resonant circuit comprises an inductor and a capacitor, the inductor and the capacitor are coupled in series and connected across the corresponding boost voltage The secondary coil of the transformer, and the capacitor is coupled to the corresponding lamp tube. 3. The multi-lamp driving device according to claim 2, wherein the inductor is an external inductor. 4. The multi-lamp driving device according to claim 2, wherein the inductor is the leakage inductance of the secondary side coil of the corresponding step-up transformer. 5. The drive device for multiple lamp tubes according to claim 1, wherein the lamp tubes are CCFL tubes. 6. The multi-lamp driving device according to claim 1, wherein the DC-to-AC converter is a full-bridge inverter. 7. The multi-lamp driving device according to claim 1, wherein the DC-to-AC converter is a half-bridge inverter. 8. The multi-lamp driving device according to claim 1, wherein the DC-to-AC converter is a push-pull inverter.

Images