Backlight control circuit

Abstract

The present invention discloses a backlight control circuit, comprising: a voltage supply circuit for receiving an input voltage and generating an output voltage under control by a control signal; at least one voltage comparison path respectively coupled to at least one light emission device path; a voltage operative amplifier circuit for generating the control signal according to a lowest voltage on the at least one voltage comparison path; and at least one under current detection circuit for detecting whether a corresponding one of the at least one light emission device path is in an under current status, whereby when anyone of the under current detection circuits detects the under current status, it sends an exclusion signal excluding a corresponding one of the at least one voltage comparison path from being an effective input of the voltage operative amplifier.

1 . A backlight control circuit, comprising:
 a voltage supply circuit, under control by a control signal, for receiving an input voltage and generating an output voltage;   a plurality of voltage comparison paths respectively coupled to a plurality of light emission device paths;   a voltage operative amplifier circuit for generating the control signal according to a lowest voltage on the plurality of voltage comparison paths; and   a plurality of under current detection circuits for detecting whether corresponding one or more of the plurality of light emission device paths are in an under current status, whereby when any said under current detection circuit detects the under current status, it sends an exclusion signal excluding a corresponding one of the plurality of voltage comparison paths from being an effective input of the voltage operative amplifier,   wherein when both or all of the under current detection circuits generate exclusion signals, the exclusion signals are neglected and the voltage supply circuit voltage generates the output voltage according to the control signal from the operative amplifier circuit which generates the control signal according to a lowest voltage on the plurality of voltage comparison paths; and when at least one of the under current detection circuits does not generate the exclusion signal, any generated exclusion signal is not neglected and the generated exclusion signal exclude a corresponding one of the plurality of voltage comparison paths from being an effective input of the voltage operative amplifier.   
     
     
         2 - 52 . (canceled) 
     
     
         53 . The backlight control circuit of  claim 1 , further comprising a start-up shielding circuit for generating a shielding signal to shield at least one exclusion signal from at least one of the plurality of under current detection circuits, wherein the shielding signal is generated according to a signal relating to circuit initialization, and the shielding signal ends when a signal relating to the end of circuit initialization is received. 
     
     
         54 . The backlight control circuit of  claim 1 , further comprising a start-up shielding circuit for generating a shielding signal to shield at least one exclusion signal from at least one of the plurality of under current detection circuits, wherein the shielding signal is generated according to a signal relating to circuit initialization, and the shielding signal ends after a predetermined time period. 
     
     
         55 . The backlight control circuit of  claim 1 , further comprising a start-up shielding circuit for generating a shielding signal to shield at least one exclusion signal from at least one of the plurality of under current detection circuits, wherein the shielding signal is generated according to a signal relating to circuit initialization, and the shielding signal ends when one of the light emission device paths leaves the under current status. 
     
     
         56 . The backlight control circuit of  claim 1 , further comprising a logic circuit coupled to the plurality of under current detection circuits, the logic circuit operating on the exclusion signals generated by the under current detection circuits such that when both or all of the under current detection circuits generate exclusion signals, the logic circuit allowing at least one of the plurality of voltage comparison paths to be a valid input of the voltage operative amplifier circuit and not to be excluded by its corresponding exclusion signal. 
     
     
         57 . A backlight control circuit, comprising:
 a voltage supply circuit, under control by a control signal, for receiving an input voltage and generating an output voltage;   a plurality of voltage comparison paths respectively coupled to a plurality of light emission device paths;   a voltage comparison and amplifier circuit for generating the control signal by comparing a lowest one of its input voltages with a reference voltage, wherein the input voltages of the voltage comparison and amplifier circuit include voltages on the plurality of voltage comparison paths; and   a plurality of under current detection circuits for detecting whether corresponding one or more of the plurality of light emission device paths are in an under current status, whereby when any said under current detection circuit detects the under current status, it sends an exclusion signal excluding a corresponding one of the plurality of voltage comparison paths from being an effective input of the voltage comparison and amplifier circuit,   wherein when both or all of the under current detection circuits generate exclusion signals, the exclusion signals are neglected and the voltage supply circuit voltage generates the output voltage according to the control signal from the voltage comparison and amplifier circuit which generates the control signal according to a lowest one of its input voltages; and when at least one of the under current detection circuits does not generate the exclusion signal, any generated exclusion signal is not neglected and the generated exclusion signal exclude a corresponding one of the plurality of voltage comparison paths from being an effective input of the voltage comparison and amplifier circuit.   
     
     
         58 . The backlight control circuit of  claim 57 , further comprising a start-up circuit having an output, wherein the input voltages of the voltage comparison and amplifier circuit include voltages on the plurality of voltage comparison paths and the output of the start-up circuit, and wherein when both or all of the under current detection circuits generate exclusion signals, the voltage comparison and amplifier circuit generates the control signal according to the output of the start-up circuit, and when none of the under current detection circuits generate exclusion signals, the voltage comparison and amplifier circuit does not generate the control signal according to the output of the start-up circuit. 
     
     
         59 . The backlight control circuit of  claim 57 , further comprising a start-up shielding circuit for generating a shielding signal to shield at least one exclusion signal from at least one of the plurality of under current detection circuits, wherein the shielding signal is generated according to a signal relating to circuit initialization, and the shielding signal ends when a signal relating to the end of circuit initialization is received. 
     
     
         60 . The backlight control circuit of  claim 57 , further comprising a start-up shielding circuit for generating a shielding signal to shield at least one exclusion signal from at least one of the plurality of under current detection circuits, wherein the shielding signal is generated according to a signal relating to circuit initialization, and the shielding signal ends after a predetermined time period. 
     
     
         61 . The backlight control circuit of  claim 57 , further comprising a start-up shielding circuit for generating a shielding signal to shield at least one exclusion signal from at least one of the plurality of under current detection circuits, wherein the shielding signal is generated according to a signal relating to circuit initialization, and the shielding signal ends when one of the light emission device paths leaves the under current status. 
     
     
         62 . The backlight control circuit of  claim 57 , further comprising a logic circuit coupled to the plurality of under current detection circuits, the logic circuit operating on the exclusion signals generated by the under current detection circuits such that when both or all of the under current detection circuits generate exclusion signals, the logic circuit allowing at least one of the plurality of voltage comparison paths to be a valid input of the voltage operative amplifier circuit and not to be excluded by its corresponding exclusion signal. 
     
     
         63 . A method for controlling light emission devices, comprising:
 providing a plurality of light emission device paths connected in parallel, each path including at least one light emission device;   supplying an output voltage to a node where the plurality of light emission device paths are coupled to;   extracting a voltage signal from each of the plurality of light emission device paths;   detecting whether each of the plurality of light emission device paths is in an under current status;   if all of the light emission device paths are in the under current status, supplying the output voltage and neglecting the detection of the under current status; and   if any of the light emission device paths is not in the under current status, selecting the lowest one of the extracted voltages from the plurality of light emission device paths which are not in the under current status, and controlling the output voltage according to the selected lowest voltage.