| 摘要 |
PURPOSE:To protect a horizontal output transistor(TR) while keeping a high voltage correction by providing a high voltage stop control circuit which detects a switching signal, stops the operation of a switching regulator at the changeover of a horizontal synchronizing signal to cause the opening state thereto on the output circuit. CONSTITUTION:A high voltage stop control circuit 10 detects a switching signal generated from a changeover control circuit 9 at the changeover of a horizontal synchronizing signal. The circuit 10 upon the detection of the switching signal stops the operation of a voltage step-down type switching regulator 1 to cause the open state thereto thereby stopping production of a horizontal output pulse Vcp from a horizontal output TR Q1. A pulse Vcp at the changeover of the horizontal synchronizing signal is zero, no high voltage HV is produced and a CRT is not discharged. Thus, no discharge in the CRT is caused at the changeover of the horizontal synchronizing signal, then the TR Q1 is protected from destruction resulting from the TR Q1 exceeding the permissible safe operating region. Since the TR Q1 is protected in this way, a voltage difference HB2-HB3 between the input and the output of a series regulator 2 is set to be a sufficiently large value thereby keeping the high voltage HV correction of the regulator 2. |
