| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent an unexpected turn-off of a high-side switch element during step-up mode in a step-up/step-down converter. <P>SOLUTION: The step-up/step-down converter in a power-supply circuit comprises: a high-side switch element Q1; and a low-side switch element Q2. A controller 10 realizes desired step-up operation by controlling the high-side switch element Q1 basically to an on state, and performing on/off control of the low-side switch element Q2 during a step-up mode. In addition, the controller 10 provides a forced off period Tfoff consisting of a predetermined short time length during an off period of the low-side switch element Q2 to temporarily turn off the high-side switch element Q1. This can charge a bootstrap capacitor C3, from which the electric charge continues to be discharged while the high-side switch element Q1 is controlled to the on state, during the off period Tfoff. <P>COPYRIGHT: (C)2012,JPO&INPIT |
