| 摘要 |
When a main switching transistor (Q3) of a zero voltage switching power supply (100) is conductive, a voltage (VR1112) is developed in a current sensing resistor (R12) coupled in series with the transistor. The voltage in the current sensing resistor is coupled to a control terminal (base) of a comparator transistor (Q2). During a given conduction interval of the main switching transistor, the comparator transistor is turned on when the current sensing resistor voltage is sufficiently large to turn on the comparator transistor. An output of the comparator transistor (VGS) is coupled to the control terminal of the main switching transistor for controlling the turn off instant of the main switching transistor on a current pulse-by-current pulse basis. A resonant voltage pulse (IC6) developed at a main current conducting terminal of the main switching transistor is capacitively coupled to the control terminal of the comparator transistor for maintaining the comparator transistor turned on, during a transition interval of the resonant voltage pulse. <IMAGE> |
