Yungtaek Jang and Milan M. JovanoviÄ. Power Electronics ... AC. Bridge. Rectifier. Fig. 1. Conventional interleaved PFC boost converter. S2. S1. V O. +. D 1. VIN.
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37th IEEE Power Electronics Specialists Conference / June 18 - 22, 2006, Jeju, Korea
Interleaved PFC Boost Converter with Intrinsic Voltage-Doubler Characteristic Yungtaek Jang and Milan M. Jovanović Power Electronics Laboratory Delta Products Corporation P.O. Box 12173, 5101 Davis Drive Research Triangle Park, NC 27709 Abstract — A novel, two-inductor, interleaved PFC boost converter that exhibits voltage-doubler characteristic when it operates with a duty cycle greater than 0.5 is introduced. The voltage-doubler characteristic of the proposed converter makes it quite suitable for universal-line (90-264 VRMS) PFC applications. Because the proposed PFC boost rectifier operates as a voltage doubler at low line, its low-line range efficiency is greatly improved compared to that of its conventional counterpart. The performance of the proposed PFC rectifier was evaluated on an experimental 1.3-kW universal-line PFC prototype.
I. INTRODUCTION To comply with various worldwide specifications governing the harmonic limits of the line current in off-line power supplies, the front-end power-factor-corrected (PFC) boost converter has been used almost exclusively in off-line power supplies for computer and telecom applications. However, in universal-line (90-264 VRMS) PFC applications, the boost converter exhibits a significant degradation of performance over the line-voltage range, [1]. Specifically, the low-line (90 VRMS) operation of the boost rectifier is much less efficient than high-line (264 VRMS) operation. Generally, an improvement of the low-line efficiency of the conventional PFC boost rectifier can be obtained by configuring the rectifier to work as a voltage doubler at low line. Several boost voltage-doubler topologies have been introduced in [2] and [3]. However, the topologies described in [2] are not suitable for PFC applications in universalinput computer/telecom power supplies since they require the PFC stage output voltage to be at least twice that of the maximum line voltage, i.e., approximately 800 V. This increased voltage at the output of the PFC front end puts undue burden on the cost and performance of the downstream dc/dc converters. The boost PFC voltagedoubler circuit introduced in [3] can work in the entire universal-line range with an output voltage slightly higher than the maximum line voltage, i.e., around 400 V. However, the circuit requires a number of range-select switches to reconfigure the converter to the voltage doubler at low line. Generally, the employment of mechanical rangeselect switches is not allowed in server applications and electronic range-select switches are not desirable because of their detrimental effect on efficiency, as well as possible reliability issues and increased cost. In high-power applications, interleaving of two boost converters is very often employed to improve performance and reduce size of the PFC front end. Namely, because interleaving effectively doubles the switching frequency and also partially cancels the input and output ripples, the size of
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2006 IEEE.
the energy-storage inductors and differential-mode EMI filter in interleaved implementations can be reduced [4], [5]. This paper presents a two-inductor, interleaved, boost PFC converter with voltage-doubler characteristic that does not require any range-select switches and that can regulate the output voltage at around 400 V in the entire universalrange line voltage. II. ANALYSIS OF OPERATION The conventional interleaved PFC boost rectifier is shown in Fig. 1, whereas Fig. 2 shows the proposed interleaved PFC boost converter with voltage-doubler characteristic. As can be seen from Figs. 1 and 2, the proposed circuit is quite similar to the conventional interleaved PFC boost converter. Since the proposed rectifier also operates with interleaved gate signals, the input current waveform and the differential-mode EMI performance of the proposed circuit in Fig. 2 are nearly identical to those of the conventional interleaved PFC rectifier in Fig. 1. It should also be noted that the proposed boost converter shares similar characteristics with the highgain dc/dc boost converter circuit introduced in [6]. To facilitate the explanation of the circuit’s operation, Fig. 3 shows a simplified circuit diagram of the circuit in Fig. 2. Assuming that blocking capacitor CB and filter capacitor CF are large enough that the voltage ripples across them are small compared to their dc voltages, blocking capacitor CB and filter capacitor CF are modeled as voltage
L1 AC
V IN
L2
D1
+
Bridge Rectifier
CF S1
S2
RL
VO
D2
Fig. 1. Conventional interleaved PFC boost converter.
L1 AC
VIN
L2
D1
D2
+
Bridge Rectifier
VX
S1
S2
+
CF
RL
VO
CB
Fig. 2. Proposed interleaved PFC boost converter with voltage-doubler characteristics.
- 1888 -
V D1
i IN
L1
VIN
i L1
i S1
D1
L2
i D1
i L2
Ts
V D2
DTs
S1
D 2 i D2
off
on
VX =
VS1
i CB
VX
t
S2
VO
i S2
V S1 S V S2 S 1 2
VO - VX = VX = =
VD1
VO 2
VO
VO
VO - VX =
VD2 i L2
i L1
VIN S2
VO 2
(a) [T0 - T1 ]
(VIN -
t
VO )/L 2
t
VO )/L 2
t
(2VIN -
VIN L
i S2
i L2
i L1
t
VIN L
i S1 D1
i IN
t
VO 2
VO 2
(VIN -
VIN L
i L2
t
VO 2
VX =
VIN L
L 1 = L2 = L
i L1
VO S1
t
VO 2
VS2
Fig. 3. Simplified circuit diagram of the proposed circuit along with reference directions of key currents and voltages.
i IN
off
on
VO )/L 2
t
VO
V IN S1
S2
i D1
VO 2
(VIN -
i D2
(b) [T1 - T2 ]
t
VO )/L 2 (VIN -
VO )/L 2
t t
i CB i IN
i L1
t
i L2
VIN
VO S1
i IN
VO 2
S2
i IN = i L1+ i L2 T0
(c) [T2 - T3 ]
T1
T2
T3
T4
T5
t
Fig. 5. Key ideal waveforms (0.5≤D
