| 摘要 |
PROBLEM TO BE SOLVED: To provide a piezoelectric transformer-inverter for driving cold cathode tube and a liquid crystal indicator by which a cold cathode tube can be turned on appropriately, in accordance with use condition. SOLUTION: While the tube current is kept uniform and stable, when an input voltage Vi' to a tube current adjusting circuit 10 drops, a voltage which is generated in a voltage-dividing circuit (not shown) in the circuit 10 becomes larger than ever, so that a load current detection voltage Vri is changed into a larger value, and an error amplification circuit 5 outputs such a positive voltage to a voltage control oscillation circuit 6 that is resulted by comparing the load current detection voltage Vri with a reference voltage Vref. As a result, the tube current of the cold cathode tube 2 (load current detection voltage Vri) begins to decrease. Then, when the tube current (load current detection voltage Vri) and the reference voltage Vref reach the same value, the tube current is kept almost constant. |
