| 摘要 |
PURPOSE: To synchronize the operation of a chopper transistor with a horizontal scanning frequency by responding to a synchronous input signal at frequency related with a deflection frequency while using a transformer having two winding wires, and periodically supplying a low impedance between both the ends of the 2nd winding wire through 2nd switching connected to the 2nd winding wire. CONSTITUTION: A switching transistor Q4 is connected between both the ends of a secondary winding wire W3 at a transformer T1 through a diode D400 and a current limit resistor R400 having a low resistance value. While transistors Q1 and Q2 are conducted, the transistor Q4 is turned on, and the transistor Q4 is turned by a flyback pulse VH at horizontal frequency extracted from a horizontal deflection circuit. Thus, the transistor Q4 applies the low impedance, with which load is applied to the transformer T1, between both the end of the winding wire W3 and generates stepwise increase in a collector current i1 of the transistor Q1. Thus, the timing of switching in a switch mode power source 300 is synchronized with the horizontal scanning frequency. |
