Failure detection method of circuit with LCD screen backlight power supply structure

Abstract

The invention discloses a failure detection method with an LCD screen backlight power supply structure, which comprises a frequency modulation control IC, lamp loop current feedback, a detection loop of lamp failure electric parameters, a power converting loop and a lamp; the frequency modulation control IC generates lamp operating frequency, the frequency is used for stabilizing the current thereof according to the adjustment of the lamp loop current feedback, and simultaneously, the detection loop of lamp failure electric parameters samples the lamp loop electric parameters for failure judgment; the power converting loop works at the frequency generated by the frequency modulation control IC to complete the conversion of energy required when the lamp works. The invention adopts the method of sampling the variation value of electric parameters corresponding to the different operating conditions of frequency under two or a plurality of operating conditions of frequency for alternative judgment; in the specific application, the converter is led to be at another preset operating frequency regularly or irregularly by the instructions of the control loop, and the electric parameters (including voltage, current or the dispersion thereof) with sensitive change at the operating frequency are sampled and whether the electric parameters exceed the set value is judged, thus being capable of more accurately detecting the variation of the electric parameters which are difficult to be discriminated when the failure of weak electric arc occurs at the normal operating frequency; therefore, the accuracy of failure recognition is improved and the safety is greatly promoted.

Description

technical field [0001] The invention relates to the technical field of CCFL multi-lamp power supply, in particular to a fault detection method for a backlight power supply circuit of a multi-lamp LCD screen by adopting series capacitors to balance current. Background technique [0002] When the LCD screen uses CCFL backlight power supply, due to the complex negative resistance characteristics of the CCFL lamp tube, the drive circuit must be matched with a high-impedance output. The common method is to connect the loop with a series capacitor or inductor (including the inductor that exists in the structure leakage inductance mode). Such as figure 1 As shown, a typical circuit series capacitor method, from the circuit principle and mathematical calculations, it can be known that in normal operation, the impedance of the series capacitor should reach more than 1.5 times the impedance of the lamp tube, in order to obtain a better impedance neutralization effect, thereby reducing...

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Problems solved by technology

like figure 1 As shown, a typical circuit series capacitor method, from the circuit principle and mathematical calculations, it can be known that in normal operation, the impedance of the series capacitor should reach more than 1.5 times the impedance of the lamp tube, in order to obtain a better impedance neutralization effect, thereby reducing the The influence of the complex negative resistance characteristics of CCFL lamps on the driving circuit also provides better current balance conditions for CCFL multiple lamps to share one drive circuit; The degree of change in electrical physical quantities caused by this is also weakened. This situation is particularly prominent when multiple CCFL lamps share a drive circuit, and the fault detection samples the electrical physical quantities of the main drive circuit or the partial loop after the summary of some branches, resulting in some In the weak arc fault state caused by leakage state, corona discharge and tin crack, etc., the detection circuit cannot distinguish, and the safety is poor

[0003] The existing method of independent sampling and detection of each branch of CCFL lamps has the advantages of accurate identification in the fault state and good safety, but the disadvantages are high cost and complicated circuits, which are suitable for occasions with a small number of lamps

Or detect and sample the electrical physical quantities of the main drive circuit or the partial loop after the summary of some branches. Its advantage is that it simplifies the circuit and is suitable for occasions with a large number of lamp tubes. After the number of lamp tubes increases, when one of the branches has faults such as leakage state, corona discharge and weak arc, the high impedance of the series capacitor reduces the reflection of the fault signal at the detection end, causing some fault protection circuits to fail to identify

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