Semiconductor laser driving circuit

Abstract From the Canadian patent

The invention provides an improvement of the conventional laser driving circuit mainly including a control logic circuit, a reproducing power producing circuit, and a recording power producing circuit for preventing a recording film of a disk from being damaged by a laser in a reproducing mode. The improved respect is addition of a voltage monitoring circuit and a bypass transistor for an abnormal signal. The voltage monitoring circuit monitors a voltage drop caused in the control logic circuit and supplies a voltage abnormality indicating signal, thereby causing the bypass transistor to be conductive for allowing the abnormal signal to be flown therethrough.