Driving device of LED tube

Abstract

The invention discloses a driving device of an LED tube. The method that a first direct-current voltage which can provide the working voltage of each LED light string of the LED tube is directly output by an AC-DC converter is applied to the driving device of the LED tube. The defects that after an existing AC-DC converter outputs a low direct-current voltage, a DC-DC boost converter is further needed so as to generate a high direct-current voltage which can be provided for the LED light string to enable the LED light string to work in the prior art are overcome. The driving device of the LED tube can reduce generated electromagnetic noise so as to reduce the design difficulty and the design cost of a needed electromagnetic noise interference suppression circuit. The driving device of the LED tube can further reduce the defect ratio of liquid crystal display products which are provided with the driving devices of the LED tubes in a factory and on the market so as to reduce the design cost of power sources of the liquid crystal display products. In addition, due to the fact that the existing DC-DC boost converter is not applied, a constant-current control circuit is adopted to ensure that each LED light string is in the constant-current state in the process of working. Besides, control over opening and closing of the constant-current circuit is used for controlling the average brightness provided by the LED tube. When the LED tube works and the detected voltage of the output end of the LED tube is larger than a protection point set valve, a dimming output port of the control circuit outputs a continuous low level signal to stop normal work of the constant-direct control circuit, the LED tube is finally switched off, and the purpose of protection is achieved.

Description

technical field [0001] The invention relates to a light source driving device, in particular to an LED lamp tube driving device which can be used in liquid crystal display products. Background technique [0002] Such as figure 1 Shown is a block diagram of a power supply system of an existing liquid crystal display product, the AC to DC (Alternating Current to Direct Current, AC-DC) converter 11 in the power supply system, the DC to DC (Direct Current to Direct Current, DC- A DC) step-up (boost) converter 12 and an LED lamp 13 constitute an LED lamp driving device, wherein the AC-DC converter 11 is, for example, an external power adapter. The AC power supply Vac for commercial use is input to the AC-DC converter 11, and a DC voltage Vdc1 of 12V-19V is generated after conversion. The DC voltage Vdc1 is input to the DC-DC boost converter 12 , and after being converted and boosted, a DC voltage Vdc2 that can provide the working voltage of the LED lamp 13 is generated. The DC...

AI Technical Summary

Problems solved by technology

[0004] The design and manufacture of the LED lamp drive device of the existing liquid crystal display products is relatively expensive and difficult

For example, the electromagnetic noise generated by components such as power transistors and boost rectifier diodes in the DC-DC boost converter 12 is relatively large, resulting in increased design difficulty and cost of the electromagnetic interference suppression circuit in the AC-DC converter 11

Moreover, the PWM control chip used to control the switching of the power transistor in the DC-DC boost converter 12 itself has a weak anti-static discharge (ElectroStatic Discharge, ESD) capability, which may easily cause the liquid crystal display products using this LED lamp tube driving device There is a certain rate of defective products in the factory and in the market

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