Patent ID: 7352162

Claim:
A pulse width modulation (PWM) boost system, comprising: a boost circuit comprising a boost inductor, wherein said boost circuit increases a first voltage to generate a DC output voltage; a voltage dividing circuit configured to generate a feedback voltage with said DC output voltage; a comparator configured to compare a reference voltage with said feedback voltage in a PWM period to generate an error voltage; a PWM circuit configured to receive said error voltage to generate a PWM signal to control said boost circuit; a pre-oscillator configured to generate a pre-oscillation signal to said PWM circuit in a pre-oscillation period; and a current limit circuit configured to control an inductor current flowing through said boost inductor; wherein a pre-oscillation period is a period when said DC output voltage is lower than a first predetermined voltage, and wherein a PWM period is a period when said DC output voltage is higher than said first predetermined voltage.