Patent ID: 6713979
Filing Date: 2004-03-30
Classification: H02P

Abstract:
A drive circuit for an actuator having an inductance, wherein the actuator is driven by causing a drive current to flow into the inductance, the drive circuit comprising:two pairs of output transistors, each pair including a power-side output transistor and a ground-side output transistor, the inductance of the actuator being connected to nodes formed between each pair of said power-side and ground-side output transistors; an overvoltage detection circuit for detecting whether voltages appearing at said nodes formed between each pair of said power-side and ground-side output transistors are higher than a supply voltage by a first predetermined level and whether said voltages are lower than a ground level by a second predetermined level; wherein an output from said overvoltage detection circuit activates one of the ground-side output transistors so that a voltage of the node connected to said around-side output transistor decreases when the voltage of the node connected to said ground-side output transistor exceeds the supply voltage by the first predetermined level, and an output from the overvoltage detection circuit activates one of the power-side output transistors so that a voltage of the node connected to said power-side output transistor increases when the voltage of the node connected to said power-side output transistor becomes lower than the ground level by the second predetermined level.