Patent ID: 8878499

Claim:
A Power Factor Correction (PFC) boost converter for generating a power to a voltage converter, the PFC boost converter comprising: a PFC converter unit configured to adjust power outputted to the voltage converter according to a pulse width modulation (PWM) signal; and a control unit, coupled to the PFC converter unit, configured to modulate a frequency of the PWM signal according to at least one of an output load current and an output load voltage of the PFC converter unit; wherein, the control unit comprises: a current detection circuit configured to generate a first detection signal responsive to the output load current of the PFC converter unit; a voltage detection circuit configured to generate a second detection signal responsive to the output load voltage of the PFC converter unit; and a control circuit, coupled to the current detection circuit and the voltage detection circuit, configured to modulate the frequency of the PWM signal according to at least one of the first detection signal and the second detection signal; wherein the voltage detection circuit comprises: a first resistor having a first end coupled to the control circuit; a first comparator having a non-inverting input terminal coupled to a second end of the first resistor and an inverting input terminal coupled to an output terminal of the first comparator; a second resistor having a first end coupled to the output terminal of the first comparator; a second comparator having a non-inverting input terminal coupled to a second end of the second resistor, the non-inverting input terminal of the second comparator coupled to an output terminal of the second comparator through a third resistor and the output terminal for outputting the second detection signal; a fourth resistor coupled between an inverting input terminal of the second comparator and a first end of a first capacitor and a second end of the first capacitor coupled to a ground; a fifth resistor coupled between an operating voltage and a cathode terminal of a programmable voltage regulator, an anode of the programmable voltage regulator coupled to the ground and a reference terminal of the programmable voltage regulator coupled to the cathode terminal of the programmable voltage regulator, wherein a junction of the fourth resistor and the first capacitor coupled to the cathode of the programmable voltage regulator; a second capacitor coupled between the non-inverting input terminal of the first comparator and the inverting input terminal of the first comparator; and a third capacitor coupled between the non-inverting input terminal of the second comparator and the ground; wherein, when either the output load current or the output load voltage of the PFC converter unit increases, the control unit increases the frequency of the PWM signal; when either the output load current or the output load voltage of the PFC converter unit decreases, the control unit reduces the frequency of the PWM signal.