| 摘要 |
An open lamp protection circuit is provided to reduce manufacturing cost and error by detecting an open state of a lamp and simplifying the open lamp protection circuit. An open lamp protection circuit includes a transistor(51), a detection terminal(52), and a plurality of transformers(53). The plurality of transformers(53) provides an inverting voltage to a lamp used in a backlight. A forward-inverse signal generation unit sums forward signals outputted from the in-phase transformers(53) having the same polarity among the plurality of transformers(53) and inverse signals outputted from the inverse phase transformers(53) having opposite polarity among the plurality of transformers(53). The forward-inverse signal generation unit outputs a forward-inverse signal at each of feedback channels of each lamp. By inputting a predetermined detection voltage to a collector of the transistor(51) and inputting the forward-inverse signal to a base, the transistor(51) is switched off when the forward-inverse signal is a zero level, and the transistor(51) is switched on when the forward-inverse signal is not a zero level. The detection terminal(52) outputs a detection voltage by switching off the transistor(51) when the forward-inverse signal inputted to the base is the zero level by connecting an emitter of the transistor(51) to a detection voltage node. |
