Patent ID: 7619909

Claim:
A control circuit for adjusting leading edge blanking time, applied to a power converting system, the control circuit adjusting a leading edge blanking time according to a feedback signal relative to a load connected to an output terminal of the power converting system to make an over-current protection mechanism of the power converting system disabled within the leading edge blanking time, the control circuit comprising: a variable charging current generating circuit, for generating a charging current proportional to a voltage value of the feedback signal according to the feedback signal; a capacitor; a charge/discharge switch, coupled to the capacitor, wherein when a power switch of the power converting system is turned on, the charge/discharge switch is turned off to make the charging current charge the capacitor, and when the power switch is turned off, the charge/discharge switch is turned on to make the capacitor discharge; and a first comparator, having an input terminal coupled to the capacitor and the charge/discharge switch, wherein when a voltage of the capacitor reaches a reference voltage of the first comparator, an output signal of the first comparator makes the power converting system enable the over-current protection mechanism; wherein a time interval from the time the power switch is turned on until the time the voltage of the capacitor reaches the reference voltage of the first comparator is the leading edge blanking time.