Backlight control circuit
A technology of backlight control and circuit, which is applied in the field of start-up circuit, and can solve the problems of low error-proof function, failure, voltage supply circuit 11 to increase the supply voltage, etc.
Active Publication Date: 2010-06-23
RICHTEK TECH
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Problems solved by technology
Although these multiple backlight control circuits 10 can be combined and manufactured in the same integrated circuit, it is obviously not an economical way
[0011] Additionally, if using image 3 shown in the known backlight control circuit 20, which constitutes as Figure 5 Although the series-parallel circuit of LEDs shown can expand the number of LEDs connected, it also has the aforementioned disadvantages: if one of the LEDs in series is faulty and disconnected, the minimum voltage selection circuit 21 will malfunction, causing the voltage supply circuit to 11 Constantly increasing supply voltage
therefore, Figure 5 The circuit shown has a limited range of applications and a low level of error proofing
Method used
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[0073] Please refer to Figure 6 , wherein one of the embodiments of the invention is shown as a schematic circuit diagram. As shown in the figure, in addition to the voltage supply circuit 11, the error amplifier circuit 13, the lowest voltage selection circuit 21, and the current sources CS1-CSN (represented by circuit blocks), the backlight control circuit 30 of this embodiment also includes There is an under current detection circuit (Under Current Detection, UCD) 31-3N. The function of the low current detection circuit 31-3N is to detect whether the current is too low or no current occurs on the parallel paths 101-10N of the light emitting diodes. (The LED path 101-10N refers to the entire path from the node of the output voltage Vout to the ground.) When the current is not too low or no current occurs, the voltage signal on the LED parallel path 101-10N will pass through The low current detection circuit 31 - 3N transmits to the corresponding voltage comparison path 11...
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The invention proposes a backlight control circuit which comprises a voltage supply circuit which receives an input voltage and is controlled by a control signal to generate an output voltage; at least one current source circuit which controls the current on the route of at least one corresponding illumination component and the current source circuit comprises of an operational amplifier, a transistor controlled by the output of the operational amplifier and a resistor; at least one voltage acquisition node that corresponds to the route of at least one illumination component; and a voltage comparison amplification circuit which generates the control signal according to the lowest voltage of at least one voltage acquisition node. The amplification circuit of the current source circuit has a first reference voltage input and the voltage comparison amplification circuit has a second reference voltage input. In addition, the first reference voltage input and the second reference voltage input have functional relationship.
Description
technical field [0001] The invention relates to a backlight control circuit (Backlight Control Circuit) and a starting circuit used in the backlight control circuit. Background technique [0002] In the liquid crystal display device, the backlight control circuit is used to control the light-emitting diodes to emit light from the back of the liquid crystal screen, so that users can watch the images on the screen. [0003] In the early days, since LED backlights were only used in small-sized screens, the required backlight brightness did not need to be too strong, so all LEDs could be connected in series or in parallel. Taking full series as an example, such as figure 1 As shown, the backlight control circuit 10 in the prior art includes a voltage supply circuit 11 for providing an output voltage Vout to the LEDs L1-LN connected in series. At the same time, a resistor R is provided on the path of the LEDs connected in series. By extracting the voltage at the node Vsense1 an...
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IPC IPC(8): G02F1/133H05B33/08H05B44/00
Inventor 刘景萌
Owner RICHTEK TECH