Power factor correction circuit with resonant snubber

Details Power factor correction circuit with resonant snubber Power factor correction circuit with resonant snubber

2002-07-19

2004-02-10

Riley, Shawn (Department: 2838)

Electricity: power supply or regulation systems

In shunt with source or load

Using choke and switch across source

C323S207000, C323S208000, C361S018000, C361S091700

Reexamination Certificate

active

06690143

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a power factor correction circuit with a snubber, which uses a resonant inductor, a resonant capacitor and two forward-biased diodes to form a passive snubber thereby increasing utility efficiency, decreasing switching loss and keeping voltage and current in phase.
2. Description of the Related Art
The same element function denotes the same reference number throughout the specification.
FIG. 1
shows a typical power factor correction circuit (hereinafter is referred to as PFC circuit). In
FIG. 1
, the PFC circuit comprises an input part
101
and a main part
104
. The input part
101
such as a bridge rectifier receives an AC voltage and outputs an uncontrolled DC voltage. The main part
104
such as a boost converter regulates the uncontrolled DC voltage and outputs a stable DC voltage to the load
105
. The main part
104
comprises a switch
106
such as MOSFET having a parasitic diode
110
a
and capacitor
110
b
connected in parallel therewith, an inductor
107
, a diode
108
, and an energy storage capacitor
109
. The load
105
means any possible apparatus or device which receives the DC voltage from the PFC circuit to operate. The load
105
may be indicated by the equivalent resistance ‘R’ of the apparatus or device, for brevity.
It is well known that the main part
104
can operate in three modes: (1) continuous conduction mode (C.C.M), (2) discontinuous conduction mode (D.C.M), and (3) boundary mode (B.M). Generally, the main part
104
operates in the C.C.M and the switch
106
turns on and off periodically in high frequency (usually 50~200 KHz).
FIG. 2
shows the voltage (Vd) and current (Id) waveforms of a MOSFET serving as the switch
106
in FIG.
1
. It is clear that the switch
106
(MOSFET) cannot turns on under zero voltage (or turns off under zero current), and therefore large switching loss is induced. Several way were proposed to reduce the switching loss. One is to make the main part
104
operate in the D.C.M or B.M. to minimize the turn-on or turn-off loss of the switch
106
. Additional active switch such as active snubber is required to reduce the switching loss. However, adding another active switch is not permitted for cost consideration.
FIG. 3
is a typical PFC circuit with a passive snubber. Compared to
FIG. 1
, a snubber
200
is added to the main part
104
, and connected in parallel with the diode
108
. Referring to
FIG. 3
, the snubber
200
comprises two capacitors
201
and
203
, two diodes
204
and
205
, and an inductor
202
which is connected between the cathode of the diode
204
and the anode of the diode
205
, wherein the anode of the diode
204
and the cathode of the diode
205
are respectively connected to the anode and cathode of the diode
108
.
Referring to
FIG. 3
, when the switch
106
is turn-on, the voltage (or charge) stored in the energy storage capacitor
109
charges the capacitors
203
and
201
. When the switch
106
is turn-off, the voltage (or charge) stored in the capacitors
203
and
201
is discharged to the energy storage capacitor
109
. The voltage increasing rate across the switch
106
while turning off depends on the discharge rate of the capacitors
203
and
201
. As such, the voltage across the switch
106
will increase slowly rather than suddenly become large during its transition from turn-on to turn-off. Consequently, the turn-off switching loss is less than that described in FIG.
1
.
FIG. 4
shows the voltage (Vd) and current (Id) waveforms of a MOSFET serving as the switch
106
in FIG.
3
. During each of the time interval Td in
FIG. 4
, it is clear that the switch
106
carries out turn-off operation and almost generates no switching loss.
However, the snubber
200
is charged by the energy storage capacitor
109
and discharged (pumped) to the same, and the charging and pumping currents from and to the energy storage capacitor
109
always cause more conduction loss.
SUMMARY OF THE INVENTION
Therefore, an object of the invention is to provide a PFC circuit with a passive snubber, which uses a resonant capacitor in conjunction with a resonant inductor and two diodes to make the voltage across the switch increase slowly when the switch becomes turn-off from a turn-on state so as to reduce the switch loss, increase power utility efficiency and keep voltage and current in phase.
To realize the above and other objects, the invention provides a PFC circuit with a passive snubber. The PFC circuit comprises: an input part with two output terminal for receiving a AC voltage and outputting a first DC voltage; and a main part for converting the first DC voltage to a second DC voltage, comprising a primary inductor with one terminal connected to one output terminal of the input part, a switch connected between the other terminal of the primary inductor and the other output terminal of the input part, a primary diode with an anode connected to the other terminal of the primary inductor, and an energy storage capacitor connected between a cathode of the primary diode and the other output terminal of the input part; and a snubber for ensuring the switch to operate in soft turn-on and soft turn-off, comprising a cascaded device with one terminal coupled to the output terminal of the input part which at least is composed of a first diode and a resonant inductor, a second diode connected between the other terminal of the cascaded device and the cathode of the primary diode, and a resonant capacitor connected between the anode of the second diode and the anode of the primary diode.


REFERENCES:
patent: 6236191 (2001-05-01), Chaffai
patent: 6525513 (2003-02-01), Zhao

Affiliated with

Also associated with

Rating

Power factor correction circuit with resonant snubber does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Power factor correction circuit with resonant snubber, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power factor correction circuit with resonant snubber will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3312480