Patent ID: 8749997

Claim:
A switching mode power supply, comprising: a power switch configured to be turned ON and OFF under the control of a switching control signal; an energy storage component configured to store energy when the power switch is turned ON, and to release the stored energy when the power switch is turned OFF; a current sense circuit configured to sense a current flowing through the energy storage component, and wherein based on sensing the current flowing through the energy storage component, the current sense circuit generates a current sense signal; a reference signal generator having an input terminal and an output terminal, wherein the input terminal is configured to receive the switching control signal, and wherein based on the switching control signal, the reference signal generator generates a reference signal at the output terminal, wherein the relationship between the reference signal (V limit ) and an ON time (t onp ) is expressed as an equation: V limit = K × t onp t onp + t d wherein in the equation, the ON time (t onp ) is defined as the time period when the power switch of the power supply is ON, and K is a predetermined value, and t d is a shut down delay of the switching control signal; and a comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the output terminal of the reference signal generator to receive the reference signal, the second input terminal is coupled to the current sense circuit to receive the current sense signal, and wherein based on the reference signal and the current sense signal, the comparator generates a comparison signal at the output terminal.