Power factor correction circuit having bottom skip controller
A power factor correction circuit includes: an ON time setting unit, which sets an ON time period of the switching element based on the output voltage; a bottom detection unit, which detects a bottom when a voltage between both ends of the switching element is damped-oscillated while the switching element is being turned off; and a bottom skip controller, which causes the switching element to perform quasi-resonant if a ratio of the ON time period set by the ON time setting unit to a regeneration period of a current flowing through the reactor while the switching element is being turned off is less than or equal to a predetermined value, and turns on the switching element at a timing when a next bottom is reached after one bottom skipped from an initial bottom if the ratio is greater than the predetermined value.
1. A power factor correction circuit, which is capable of rectifying an AC voltage into a DC voltage, switching the DC voltage through a series circuit of a reactor and a switching element, and obtaining a predetermined output voltage by rectifying and smoothing regeneration energy of the reactor, comprising:
an ON time setting circuit, which sets an ON time period of the switching element based on the predetermined output voltage;
a bottom detection circuit, which detects a bottom when a voltage between both ends of the switching element is damped-oscillated while the switching element is being turned off; and
a bottom skip controller, which
causes the switching element to perform quasi-resonant if a ratio of the ON time period set by the ON time setting circuit to a regeneration period of a current flowing through the reactor while the switching element is being turned off is less than or equal to a predetermined value, and
turns on the switching element at a timing when a next bottom is reached after one bottom skipped from an initial bottom if the ratio is greater than the predetermined value.
2. The power factor correction circuit according to claim 1 , further comprising
a light load determination circuit, which determines whether or not a load is a light load, based on the predetermined output voltage,
wherein the bottom skip controller turns on the switching element at a timing when a next bottom is reached after one bottom skipped from an initial bottom if the light load determination circuit determines that the load is a light load.
3. The power factor correction circuit according to claim 1 , further comprising
a light load determination circuit, which determines whether or not a load is a light load, based on the predetermined output voltage,
wherein the bottom skip controller turns on the switching element at a timing when a next bottom is reached after plural bottoms skipped from an initial bottom if the light load determination circuit determines that the load is a light load and the ON time period is greater than the regeneration period of the current flowing through the reactor.