CN102196622B - Backlight device - Google Patents

Abstract

The invention discloses a backlight device, which comprises a plurality of light emitting diode modules, wherein each light emitting diode module comprises a first pin group, a second pin group, a driving circuit, a first light emitting diode string and a second light emitting diode string. Each pin set has a first power pin, a second power pin, a first ground pin and a second ground pin, wherein the first and second power pins are coupled to each other, and the first and second ground pins are coupled to each other. Wherein the first ground pin of the first pin set is coupled to the first power pin of the second pin set. The driving circuit is used for providing a driving signal. Each LED string is respectively connected in series between the second power pin and the second ground pin of each pin set and receives the driving signal.

Description

backlight

technical field

The invention relates to a backlight device, and in particular to a backlight device of a light emitting diode.

Background technique

In today's liquid crystal display panel, a backlight device constructed by using light-emitting diodes is often used to construct. The backlight devices of these light-emitting diodes often have different designs in response to different requirements. For example, when the LED backlight device needs to display a high degree of display, it is necessary to use the design method of the so-called multi-circuit LED backlight. That is, a plurality of LED strings are used for design.

After increasing the number of LED strings, the derived problem is how to make each LED string emit light uniformly. In the design of the existing LED backlight device, each string of LEDs is driven by an independent driving circuit. And adjust according to the brightness difference generated when each driving circuit drives each corresponding LED string, so that each LED string can present similar brightness, and improve the brightness uniformity of the backlight device.

However, the design of this existing LED backlight device requires a lot of driving circuits and high circuit cost, and also requires accurate adjustment of each driving circuit so that the luminance of the corresponding LED strings is similar. The complicated and expensive technology greatly increases the cost of the conventional LED backlight device.

Contents of the invention

The invention provides a backlight device, which can effectively improve the luminous uniformity thereof.

The invention proposes a backlight device, which includes a plurality of LED modules, and each LED module includes first and second pin groups, a driving circuit, and first and second LED strings. Each pin group has a first power pin, a second power pin, a first ground pin and a second ground pin, the first and second power pins are coupled to each other, and the first and second ground pins are connected to each other. The feet are coupled to each other. Wherein the first ground pin of the first pin group is coupled to the first power pin of the second pin group. The driving circuit is coupled to the first power pin of the first pin group and the first ground pin of the second pin group to provide a driving signal. Each LED string is respectively coupled between the second power pin and the second ground pin of each pin group, and receives a driving signal.

In an embodiment of the present invention, each of the above LED modules further includes at least one third pin group and at least one third LED string. The third pin group has a first power pin, a second power pin, a first ground pin, and a second ground pin, and the third pin group is coupled to the drive circuit coupled to the first pin group coupled to the second pin group. The coupling path of the ground pin. Wherein, the first power pin of the third pin group is coupled to the first ground pin of the second pin group, and the first ground pin of the third pin group is coupled to the driving circuit. The third LED string is serially connected between the second power pin and the second ground pin of the third pin group to receive the driving signal.

In an embodiment of the present invention, the above-mentioned driving signal is a driving current.

In an embodiment of the present invention, the above driving circuit is a DC-to-DC power converter.

In an embodiment of the present invention, the above-mentioned DC-to-DC power converter includes an inductor, a semiconductor switch, a first diode, a voltage detection circuit and a controller. One end of the inductor receives the input voltage. A semiconductor switch is connected in series between the other end of the inductor and the reference voltage, and is controlled by a pulse width modulation signal. The anode of the first diode is commonly coupled with the inductor and the semiconductor switch, and the cathode thereof generates a driving signal. The voltage detection circuit receives the driving signal and generates an overvoltage detection signal according to the divided voltage driving signal. The controller receives the operating voltage, the feedback signal, the overvoltage detection signal, the enabling signal and the dimming signal, and generates a PWM signal according to the feedback signal and the dimming signal when the enabling signal is enabled. Wherein, the semiconductor switch may include a transistor switch and a crystal switch (MOS), and the present invention uses a crystal switch as a representative technical description.

In an embodiment of the present invention, the controller also stops generating the PWM signal when the driving circuit is over-voltaged according to the over-voltage detection signal.

In an embodiment of the invention, the backlight device further includes a voltage generator. The voltage generator is coupled to the driving circuit and used for generating the operating voltage according to the input voltage.

In an embodiment of the present invention, the above voltage generator includes a first current limiting resistor, a second current limiting resistor, a transistor, a voltage stabilizing capacitor and a diode. One end of the first and second current limiting resistors jointly receive the input voltage, the control end of the transistor is coupled to the other end of the first current limiting resistor, and the first end of the transistor is coupled to the other end of the second current limiting resistor. The voltage stabilizing capacitor is connected in series between the second terminal of the transistor and the reference voltage. The anode of the second diode receives the reference voltage and the cathode thereof is commonly coupled with the transistor and the first current limiting resistor.

Based on the above, the present invention makes use of changing the connection relationship between a plurality of light-emitting diode strings and the driving circuit of the backlight device, so that more strings of light-emitting diodes are connected in series, so as to reduce the number of driving circuits that need to be used, and further improve the backlight device. The uniformity of luminous brightness between.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail together with the accompanying drawings.

Description of drawings

FIG. 1 shows a schematic diagram of a backlight device 100 according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a backlight device 200 according to another embodiment of the present invention;

FIG. 3 shows the implementation of the driving circuit 211 according to the embodiment of the present invention.

[Description of main component symbols]

100, 200: backlight device

110, 120, 210, 220: LED module

114, 115, 215, 216, 217: LED strings

111, 211, 360, 380: drive circuit

112, 113, 212, 213, 214: Pin groups

320: voltage generator

311: Controller

312: Overvoltage protection circuit

313: Feedback circuit

D1, D2: Diodes

Q2: Semiconductor switches

Q1: Transistor

VIN1: input voltage

VIN: Voltage

GND: reference voltage

L1: Inductance

EA: enable signal

OVP: overvoltage detection signal

FB: feedback signal

VCC: operating voltage

R1, R2: resistance

R3, R4: feedback detection resistor

C3: capacitance

PI1, PI2, PI3, GI1, GI2, GI3: pins

D11～D1N, D21～D2N, D31～D3N: LED

Fuse: fuse

Detailed ways

Please refer to FIG. 1 below. FIG. 1 is a schematic diagram of a backlight device 100 according to an embodiment of the present invention. The backlight device 100 includes a plurality of LED modules 110 , 120 . Taking the LED module 110 as an example, the LED module 110 includes pin groups 112 and 113 , a driving circuit 111 and LED strings 114 and 115 . Wherein, the pin group 112 has a first power pin PI1 , a second power pin PI2 , a first ground pin GI1 and a second ground pin GI2 . Moreover, in the pin group 112 , the first power pin PI1 and the second power pin PI2 are connected to each other (short circuit), and the first ground pin GI1 and the second ground pin GI2 are connected to each other (short circuit). Similarly, the pin group 113 has a first power pin PI3 , a second power pin PI4 , a first ground pin GI3 and a second ground pin GI4 . In the pin group 113 , the first power pin PI3 and the second power pin PI4 are connected to each other (short circuit), and the first ground pin GI3 and the second ground pin GI4 are connected to each other (short circuit). In addition, in this embodiment, the first ground pin GI1 of the pin group 112 is directly connected to the first power pin PI3 of the pin group 113 .

The driving circuit 111 is coupled to the first power pin PI1 of the pin group 112 and the first ground pin GI3 of the pin group 113 , and the driving circuit 111 transmits the driving signal to the LED string 114 through the pin groups 112 and 113 , 115. The LED string 114 is composed of a plurality of LEDs D11-D1N connected in series (N LEDs, N is a positive integer), while the LED string 115 is composed of N LEDs D21-D2N connected in series . The anode of the first LED D11 in the LED string 114 is coupled to the second power pin PI2 of the pin group 112, and the cathode of the last LED D1N in the LED string 114 is coupled to the pin group. The second ground pin GI2 of 112 . Similarly, the anode of the first light-emitting diode D21 in the light-emitting diode string 115 is coupled to the second power pin PI4 of the pin group 113, and the cathode of the last light-emitting diode D2N in the light-emitting diode string 115 is coupled to to the second ground pin GI4 of the pin group 113 .

From the above description of the coupling relationship, it can be easily known that the drive circuit 111 is connected in series to the LED string 114 through the pin group 112, and then connected in series to the LED string 115 through the pin group 112 through the pin group 113, and finally Connect back to the drive circuit 111 to form an electrical loop. That is to say, the driving signal (taking the driving current as an example) provided by the driving circuit 111 will be transmitted to the LED string 114 through the first and second power supply pins PI1 and PI2 of the pin group 112 , and then passed through the pin group 112 The first and second grounding pins GI1 and GI2 of the pin group 113, and the first and second power pins PI3 and PI4 of the pin group 113 are transmitted to the LED string 115, and then passed through the first and second grounding pins of the pin group 113 The pins GI3 and GI4 are sent back to the driving circuit 111 .

In this way, the LED strings 114 and 115 will receive the same driving signal without attenuation. That is to say, the luminances of the LED strings 114 and 115 are the same.

Please note that in this embodiment, each set of driving circuits 111 can drive two LED strings 114 , 115 . In other words, in the backlight device 100, the number of driving circuits is half of the total number of LED strings, effectively reducing the number of driving circuits required.

Please refer to FIG. 2 below. FIG. 2 is a schematic diagram of a backlight device 200 according to another embodiment of the present invention. The backlight device 200 includes a plurality of LED modules 210 and 220 . Taking the LED module 210 as an example, the LED module 210 includes pin groups 212 , 213 and 214 , a driving circuit 211 and LED strings 215 , 216 and 217 . Wherein, the pin group 212 has a first power pin PI1 , a second power pin PI2 , a first ground pin GI1 and a second ground pin GI2 . Moreover, in the pin group 212 , the first power pin PI1 and the second power pin PI2 are connected to each other (short circuit), and the first ground pin GI1 and the second ground pin GI2 are connected to each other (short circuit). Similarly, the pin group 213 has a first power pin PI3 , a second power pin PI4 , a first ground pin GI3 and a second ground pin GI4 . In the pin group 213 , the first power pin PI3 and the second power pin PI4 are connected to each other (short circuit), and the first ground pin GI3 and the second ground pin GI4 are connected to each other (short circuit). The pin group 214 has a first power pin PI5 , a second power pin PI6 , a first ground pin GI5 and a second ground pin GI6 . In the pin group 214 , the first power pin PI5 and the second power pin PI6 are connected to each other (short circuit), and the first ground pin GI5 and the second ground pin GI6 are connected to each other (short circuit).

In addition, in this embodiment, the first ground pin GI1 of the pin group 212 is directly connected to the first power pin PI3 of the pin group 213, and the first ground pin GI3 of the pin group 213 is directly connected to Connected to the first power pin PI5 of the pin group 214 .

The driving circuit 211 is coupled to the first power pin PI1 of the pin group 212 and the first ground pin GI5 of the pin group 214 , and provides a driving signal.

The LED strings 215 - 217 are respectively formed by serially connecting a plurality of LEDs D11 - D1N, D21 - D2N, D31 - D3N. The LED strings 215 - 217 are respectively connected to the second power pins PI2 , PI4 and PI6 and the second ground pins GI2 , GI4 and GI6 of the pin groups 212 , 213 and 214 .

The difference from the previous embodiment is that in this embodiment, there is an additional pin group 214 coupled between the coupling paths of the driving circuit 211 and the first ground pin GI3 of the pin group 213 . An additional LED string 217 is connected between the second power pin PI6 and the second ground pin GI6 of the pin group 214 . That is to say, the driving signal provided by the driving circuit 211 will be transmitted to the LED string 215 through the pin group 212, then transmitted to the LED string 216 through the pin group 213, and transmitted to the LED string through the pin group 214. 217 , and finally transmit back to the driving circuit 211 through the second and first ground pins GI6 and GI5 of the pin group 214 .

Certainly, the driving signal (taking the driving current as an example) transmitted by the driving circuit 211 can be transmitted to the serially connected LED strings 215 , 216 and 217 without attenuation. That is to say, the luminance of the LED strings 215 , 216 and 217 will be more consistent. The brightness uniformity of the backlight device 200 is improved. Moreover, the number of driving circuits can be reduced to one-third of the number of LED strings, which further reduces the demand for driving circuits and reduces circuit costs.

It is worth mentioning that in the embodiment of the present invention, another pin group can be inserted between the pin group 214 and the driving circuit 211 , and the driving signal provided by the driving circuit 211 can be extended to pass through four LED strings connected in series. The luminance uniformity of the backlight device 200 is further improved, and the circuit cost is relatively reduced.

Next, please refer to FIG. 3 . FIG. 3 illustrates the implementation of the driving circuit 211 according to the embodiment of the present invention. Wherein, the driving circuit 211 includes an inductor L1, a semiconductor switch Q2, a diode D1, an over voltage protection circuit (OVP, Over Voltage Protection) 312, a feedback circuit 313 and a controller 311. One end of the inductor L1 receives the input voltage VIN1. The semiconductor switch Q2 is connected in series between the other end of the inductor L1 and the reference voltage GND, and the semiconductor switch Q2 is controlled by a pulse width modulation signal from the controller 311 . The anode of the diode D1 is commonly coupled with the inductor L1 and the semiconductor switch Q2, and the cathode thereof generates a driving signal. The overvoltage protection circuit 312 receives the driving signal and generates an overvoltage detection signal OVP according to the divided voltage driving signal. Wherein, the feedback circuit 313 is composed of feedback detection resistors R3 and R4. The controller 311 receives an operating voltage VCC, an overvoltage detection signal OVP, a feedback signal FB, a dimming signal Dimming, and an enable signal EA (Enable). The controller 311 generates a PWM signal according to the feedback signal FB and the dimming signal Dimming when the enable signal EA is enabled. The controller 311 stops generating the PWM signal when the driving circuit 211 is over-voltage according to the over-voltage detection signal OVP.

In this embodiment, the operating voltage VCC is generated by the voltage generator 320 according to the input voltage VIN1. The voltage generator 320 is coupled to the driving circuit 211 and includes current limiting resistors R1 , R2 , transistor Q1 , voltage stabilizing capacitor C3 and diode D2 . One terminal of the current limiting resistors R1 and R2 jointly receives the input voltage VIN1 , the control terminal of the transistor Q1 is coupled to the other terminal of the current limiting resistor R1 , and the first terminal thereof is coupled to the other terminal of the current limiting resistor R2 . The voltage stabilizing capacitor C3 is connected in series between the second terminal of the transistor Q1 and the reference voltage GND. The anode of the diode D2 receives the reference voltage GND and the cathode thereof is jointly coupled with the transistor Q1 and the current limiting resistor R1. The input voltage VIN1 is generated by the voltage VIN connected in series with the fuse Fuse, and is generated by the other end of the fuse Fuse.

Incidentally, the driving circuits 360 and 380 are implemented in the same manner as the driving circuit 211 to generate high-uniformity driving signals, and details of the implementation will not be repeated below.

To sum up, the present invention changes the number of LED strings connected in series with the driving circuit by changing the connection mode of each pin between the pin groups. The driving signal provided by a single driving circuit can be serially connected to a plurality of light-emitting diode strings to improve the brightness uniformity of the backlight device. And effectively reduce the required driving circuit quantity and reduce the circuit cost.

Although the present invention has been disclosed as above with the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the appended patent application.

Claims (8)

1. back lighting device is characterized in that comprising:

A plurality of light-emitting diode (LED) modules, respectively this light-emitting diode (LED) module comprises:

One first and second pin group, respectively this pin group all has the first power pin, second source pin, the first ground connection pin and the second ground connection pin, its first and second power pin couples mutually, and its first and second ground connection pin couples mutually, and wherein the first ground connection pin of this first pin group is coupled to the first power pin of this second pin group;

One drive circuit couples the first power pin of this first pin group and the first ground connection pin of this second pin group, drives signal in order to provide one; And

One first and second light-emitting diode string, respectively this light-emitting diode string is serially connected in respectively between the second source pin and the second ground connection pin of this pin group respectively, and receives this driving signal;

Wherein, this drive circuit comprises for the dc power converter that circulates, this DC-DC power supply converter always:

One inductance, the one termination is received an input voltage;

Semiconductor class switch is serially connected between the other end and a reference voltage of this inductance, is controlled by a pulse-width modulation signal;

One first diode, its anode and this inductance and this semiconductor type switch couple jointly, and its negative electrode produces this driving signal;

One voltage detecting circuit, receive this driving signal and according to this driving signal of dividing potential drop to produce an overvoltage detection signal; And

One controller receives an operating voltage, a feedback signal, this overvoltage detection signal, an activation signal and a dim signal, is under the state of activation at this enable signal, produces this pulse-width modulation signal according to this feedback signal and this dim signal.

2. back lighting device as claimed in claim 1 is characterized in that, respectively this light-emitting diode (LED) module also comprises:

At least one the 3rd pin group, have the first power pin, second source pin, the first ground connection pin and the second ground connection pin, the 3rd pin group is coupled in the coupling between the path of the first ground connection pin that this drive circuit couples this second pin group, wherein the first power pin of the 3rd pin group couples the first ground connection pin of this second pin group, and the first ground connection pin of the 3rd pin group couples this drive circuit; And

At least one the 3rd light-emitting diode string, the 3rd light-emitting diode string are serially connected between the second source pin and the second ground connection pin of the 3rd pin group, to receive this driving signal.

3. back lighting device as claimed in claim 1 is characterized in that, this driving signal is a drive current.

4. back lighting device as claimed in claim 1 is characterized in that, this controller more stops to produce this pulse-width modulation signal when the situation of this drive circuit generation overvoltage according to this overvoltage detection signal.

5. back lighting device as claimed in claim 1 is characterized in that, this semiconductor type switch is the transistor-like switch.

6. back lighting device as claimed in claim 1 is characterized in that, this semiconductor type switch is crystal class switch.

7. back lighting device as claimed in claim 1 is characterized in that, also comprises:

One voltage generator couples this drive circuit, in order to produce this operating voltage according to this input voltage.

8. back lighting device as claimed in claim 7 is characterized in that, this voltage generator comprises:

One first current-limiting resistance, the one termination is received this input voltage;

One second current-limiting resistance, the one termination is received this input voltage;

One transistor, its control end couples the other end of this first current-limiting resistance, and its first end couples the other end of this second current-limiting resistance;

One electric capacity of voltage regulation is serially connected between this transistorized the second end and this reference voltage; And

One second diode, its anode receives this reference voltage and its negative electrode and this transistor and this first current-limiting resistance couple jointly.

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