Abstract: A PWM comprises a voltage transformation module, a voltage-sensing module and a timer. The voltage transformation module is configured to transform an input voltage into an output voltage. The voltage-sensing module is coupled to the voltage transformation module and configured to detect a voltage of a first terminal, wherein the voltage of the first terminal is proportional to the output voltage. The timer is configured to measure the time duration for which the voltage of the first terminal is lower than a reference voltage, wherein the timer initiates a short circuit signal when the time duration is greater than a predetermined value.

Abstract: A PWM comprises a voltage transformation module, a voltage-sensing module and a timer. The voltage transformation module is configured to transform an input voltage into an output voltage. The voltage-sensing module is coupled to the voltage transformation module and configured to detect a voltage of a first terminal, wherein the voltage of the first terminal is proportional to the output voltage. The timer is configured to measure the time duration for which the voltage of the first terminal is lower than a reference voltage, wherein the timer initiates a short circuit signal when the time duration is greater than a predetermined value.

Abstract: A feedback signal sensing method includes the steps of: providing a pulse width modulation (PWM) signal having a period; charging a capacitor by a current source during a pulse duration of the period, so as to form an equivalent slope compensation ramp signal; conducting an inductor current flowing from a boost inductor to flow through an equivalent resistor during the pulse duration of the period, so as to form an equivalent inductor current signal; and using a coupling characteristic of the capacitor together with the equivalent slope compensation ramp signal and the equivalent inductor current signal to form a feedback signal.

Abstract: A dimming method for light emitting diodes (LEDs), which is applied in a pulse width modulation boost circuit system, includes the following steps: (a) equally dividing a cycle into a plurality of intervals; (b) providing a plurality of control signals having the cycle and a pulse duration, wherein the pulse duration of each of the control signals is sequentially generated in the cycle; and (c) using the plurality of control signals to control a plurality of corresponding switches for dimming the LEDs connected to the switches.

Abstract: A feedback signal sensing method includes the steps of: providing a pulse width modulation (PWM) signal having a period; charging a capacitor by a current source during a pulse duration of the period, so as to form an equivalent slope compensation ramp signal; conducting an inductor current flowing from a boost inductor to flow through an equivalent resistor during the pulse duration of the period, so as to form an equivalent inductor current signal; and using a coupling characteristic of the capacitor together with the equivalent slope compensation ramp signal and the equivalent inductor current signal to form a feedback signal.