Patent ID: 8736187

Claim:
A system for adjusting brightness of one or more cold-cathode fluorescent lamps, the system comprising: a voltage selector configured to receive a dimming voltage and a first threshold voltage and generate an output voltage, the output voltage being selected from a group consisting of the dimming voltage and the first threshold voltage; an oscillator coupled to a first capacitor and configured to generate a ramp signal with the first capacitor; a signal generator configured to receive the ramp signal and the output voltage and generate a first signal, the first signal corresponding to a lamp brightness level; a brightness detector configured to receive the first signal and output a second signal, the second signal indicating whether the lamp brightness level is higher than a threshold brightness level; a logic component configured to output a third signal; an open-loop detector configured to receive at least the second signal and the third signal and generate a fourth signal in response to at least the second signal and the third signal; a protection component configured to receive the fourth signal and generate a protection signal based on at least information associated with the fourth signal; an error amplifier coupled to a second capacitor and configured to receive the first signal and a sensing voltage and to generate a fifth signal based on at least information associated with the first signal and the sensing voltage; and a gate driver configured to receive the protection signal and the fifth signal and generate a drive signal; wherein the open-loop detector is further configured to: receive the sensing voltage, the sensing voltage being associated with a lamp current flowing through at least one cold-cathode fluorescent lamp; process information associated with the second signal and the third signal; if the second signal satisfies one or more predetermined first conditions and the third signal satisfies one or more predetermined second conditions, determine whether the cold-cathode fluorescent lamp is associated with an open circuit based on at least information associated with the sensing voltage and output the fourth signal indicating whether the cold-cathode fluorescent lamp is associated with the open circuit; if the second signal does not satisfy the one or more predetermined first conditions, output the fourth signal regardless of the sensing voltage, the fourth signal indicating that the cold-cathode fluorescent lamp is not associated with the open circuit; and if the third signal does not satisfy the one or more predetermined second conditions, output the fourth signal regardless of the sensing voltage, the fourth signal indicating that the cold-cathode fluorescent lamp is not associated with the open circuit.