| 摘要 |
PROBLEM TO BE SOLVED: To reduce waveform distortion caused when reduction of a trapezoidal wave load current is started. SOLUTION: A clamp circuit 23 is provided between a source of a transistor Q11 acting like a high side switch and an output node n2 of an operational amplifier configuring an error amplifier circuit 31. When a drive command signal changes from an H level to an L level, transistors Q18, Q17 are turned on and a voltage Vn2 at a node n2 having increased up to a boosting voltage Vcp is decreased to a Zener voltage Vz of a Zener diode D11 by using a level VL of a load terminal 20 as a reference level. The Zener voltage Vz is a value higher than a threshold voltage Vt of the transistor Q11 and close to the threshold voltage Vt. Thus, gate electric charges of the transistor Q11 are extracted through a transistor Q16 and a load current IL immediately decreases according to a trapezoidal waveform signal Sb.
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