2nd Generation of PFC Solutions
Temesi Ernö, Michael Frisch, Tyco Electronics / Power Systems, Sept. 04
To achieve higher efficiency is one of the highest priorities in all power electronic applications. With the new standards active power factor correction is a must in many applications. The additional power dissipation for the electronic components might increa the size of the heat sink and the whole application. The target is to reduce the loss to a minimum without an increa of the costs
Introduction
The standard EN61000-3-2 is mandatory for power applications connected with the public power grid. For many applications the
4岁儿子生日简单说说additional function of an active PFC have to be integrated additional to the existing functions. The size of such applications is often defined by the heat sink which have to dissipate the power loss. To keep the heat sink as small as possible by integration of the additional function of PFC is a important target. Power loss are generated in the
miconductors and in the choke. To optimize the circuit with the right lection of
components in respect of lower loss is a must. With the new idea of a high efficiency PFC the loss of 2 of the 4 input rectifiers are eliminated at all, the loss of 1 miconductor junction per half-wave is eliminated.
Standard PFC-Boost-Topology
In most cas the boost topology is ud for active power factor correction. The current have to pass here at least 3 miconductor junction layer additional to the output load per
half-wave.
The input rectifier convert the AC voltage into a puld DC-voltage. The PFC-circuit boost both half waves to the DC-output voltage.
Function of High Efficiency PFC
The PFC choke is split into 2 inductors with half of the inductance. Eliminating the input rectifier for each half-wave a boost stage is now necessary. But the current have to pass a
total of only 2 miconductors per half-wave.
Simulation Results
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In theory this new topology em to be a efficient alternative to reduce loss in active PFC applications. But the next step is to check theory with simulation.
The following circuit is ud for the simulation:天爷洞
The results are deflating:菠菜怎么炒好吃
All output signals of the PFC circuit are oscillating with the PWM frequency relative to the input.
The problem is systematic, the reason is the connection of both input lines to an PFC-choke. The outcome of this is the floating of the output with high frequency relative to input source. Due to that is not possible to solve the EMI problem with external filtering.
The DC-output and the circuit connected oscillate with high frequency relative to the public power grid. The conquential high EMC emission is not acceptable for most applications. The design of applications with isolated transformer will be very difficult with this topology. Applications without transformer as motor drive are completely impossible. New Topologies
Due to this disappointing result, new possibilities were evaluated to get a high efficiency PFC solution without the disadvantage of EMC emission.
Dual Boost Topology
A new topology invented by Tyco Electronics does solve the problem. Different to the 1st idea the choke is not split, here 2 chokes with the same inductance as in the standard boost topology are req
uired. But only 1 inductor is ud per half wave. The other one is bypasd
by additional rectifiers.
With this solution the output does not oscillate with high frequency relative to the AC-input or GND. The behavior is identical to the standard boost topology. But the loss of the input rectifiers ud in the standard boost topology are cut into halves.
1. The 1st half wave is boosted with one
PFC-circuit to DC-output voltage. The
2nd choke is bypasd by the 1st
rectifier.
2. During the 2nd half wave the 2nd
PFC-circuit boost the input to DC-
output voltage. Here the 1st choke is
bypasd.
Bi-directional Boost Topology
With a 2nd topology it is possible to get the benefit of the high efficiency PFC with only 1
choke:
Here the current flow in the PFC-choke is bi-directional.英文杂志文章
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1. The positive half wave is boosted with
the low side switch and the high side boost diode. The low side rectifier builds the return path.如何开通微信
2. The negative half wave is boosted with
the high side switch and the low side boost diode. The high side rectifier builds the return path.
Also with this topology the loss of the input rectifiers ud in the standard boost topology are cut into halves. This circuit has the
advantage of using the identical PFC-choke as in the standard boost topology.怎样写请柬
Efficiency Advantage with HE-Topology In a system with 230V AC input voltage the rectifier loss of the new HE-PFC are ca. 0.5% of the total input power (at V out = 400V DC , P out = 6kW). In a 110V AC system, the rectifier loss of the new HE-PFC are ca. 1% (at V out = 400V DC , P out
= 3kW).
The efficiency of the miconductors in the 230V system are: 97.4% (at V out = 400V DC , P out = 6kW, f PWM = 80kHz). The efficiency
advantage is ca. 0.5%.
The efficiency of the miconductors in a 110V AC system are: 94.8% (at V out = 400V DC , P out = 3kW, f PWM = 80kHz). The efficiency advantage is ca. 1%.
In both cas 110V AC and 230V AC input, the miconductor loss are about 19% reduced compared with the standard boost topology.
Module Solutions
Tyco Electronics offer modules supporting both
topologies.
flow PFC 0 – HE
The Tyco Electronics module flow PFC 0 – HE supports the new dual boost topology: Features:
• up to 4,5kW at 100kHz
• all power miconductors for dual
boost stage integrated
• integrated capacitor for low inductive
output
• shunt resistor for current nsing • temperature nsor
fast PACK 0 – PFC
The Tyco fast PACK 0 – PFC module in H-Bridge configuration supports the new high
efficient bi-directional boost topology.
Features:
• up to 6kW
• all power miconductors for bi-directional boost stage are integrated. • the pinning supports the low inductive
connection of external snubber capacitors at the DC-output • temperature nsor
Summary
The new topologies are able to achieve a loss reduction in the miconductors of ca. 19%. Tyco Electronics Power & Switches offer
products for the 2 high efficiency topologies for active PFC.
