Power factor correction circuit with high-voltage...

Details Power factor correction circuit with high-voltage... Power factor correction circuit with high-voltage...

2003-08-01

2004-11-16

Abraham, Fetsum (Department: 2826)

Electricity: power supply or regulation systems

In shunt with source or load

Using choke and switch across source

C323S207000, C323S208000, C315S291000, C315S295000, C315S226000, C315S247000

Reexamination Certificate

active

06819089

ABSTRACT:

TECHNICAL FIELD
The present invention concerns the use of semiconductor compensation devices in power factor correction circuits.
BACKGROUND OF THE INVENTION
Such semiconductor devices are also known as compensation devices. Such compensation devices are, for example, n- or p-channel MOS field effect transistors, diodes, thyristors, GTOs, or other components. In the following, however, a field effect transistor (also referred to briefly as “transistor”) is assumed as an example.
There have been various theoretical investigations spread over a long period of time concerning compensation devices (cf. U.S. Pat No. 4,754,310 and U.S. Pat. No. 5,216,275) in which, however, specifically, improvements of the on-resistance RDS(on) but not of stability under current load, such as, in particular, robustness with regard to avalanche and short circuit in the high-current operation with high source-drain voltage, are sought.
Compensation devices are based on mutual compensation of the charge of n- and p-doped areas in the drift region of the transistor. The areas are spatially arranged such that the line integral above the doping along a line running vertical to the pn-junction in each case remains below the material-specific breakdown voltage (silicon: approximately 2×10
12
cm
−2
). For example, in a vertical transistor, as is customary in power electronics, p-and n-columns or plates, etc. may be arranged in pairs. In a lateral structure, p- and n-conductive layers may be stacked on each other laterally alternating between a groove with a p-conductive layer and a groove with an n-conductive layer (cf. U.S. Pat. No. 4,754,310).
By means of the extensive compensation of the p- and n-doping, the doping of the current-carrying region (for n-channel transistors, the n-region; for p-channel transistors, the p-region) can be significantly increased, whereby, despite the loss in current-carrying area, a clear gain in on-resistance R
DS
(on) results. The blocking capability of the transistor depends substantially on the difference between the two dopings. Since, because of the reduction of the on-resistance, a doping higher by at least one order of magnitude of the current-carrying area is desirable, control of the blocking voltage requires controlled adjustment of the compensation level, which can be defined for values in the range ≦±10%. With a greater gain in on-resistance, the range mentioned becomes even smaller. The compensation level is then definable by
(p-doping-n-doping)
-doping
or by
charge difference/charge of one doping area.
Other definitions are, however, possible. Power factor correction circuits are used within switching power supplies and require special features within the switching element to provide high efficiency. Semiconductor switches according to the prior art usually generate a certain amount of heat through switching losses which require the use of heat sinks and, thus, don't allow for small housings of the switching power supply.
SUMMARY OF THE INVENTION
The present invention to provide a switching power supply including a robust semiconductor component of the kind initially mentioned, to be firstly distinguished by a high “avalanche” ruggedness and high current load capacity before and/or during breakdown and secondly simple to produce with reproducible properties in view of technological latitudes of fluctuation of manufacturing processes. Thus, a very low on resistance can be guaranteed and, therefore, only a minimum of heat is generated in such a circuit. This allows for the use of a semiconductor switch without the requirement of a heat sink or at least a heat sink with only a small footprint.
A power factor correction circuit, thus, uses a semiconductor component of the kind initially mentioned, wherein the regions of the first and second types of conductivity are so doped that charge carriers of the second conductivity type predominate in regions near the first surface and charge carriers of the first conductivity type in regions near the second surface.
Preferably, the regions of the second conductivity type do not extend as far as up to the second zone, so that between said second surface and the second zone, a weakly doped region of the first conductivity type remains. It is possible, however, to allow the width of this region to go to “zero.” The weakly doped region, however, provides certain advantages, such as enhancement of the barrier voltage, “smooth” profile of the electrical field strength, or improvement of commutation properties of the inverse diode.
In another refinement, it is provided that between the first and second surfaces, a degree of compensation effected by the doping is so varied that atomic residues of the second conductivity type dominate near the first surface and atomic residues of the first conductivity type near the second surface. In other words, there are sequences of p, p
−
, n
−
, n or n, n
−
, p
−
, p layers between the two surfaces.
A switching power supply including a power factor correction circuit comprises a rectifier having a positive and a negative output terminal, an inductor having a first and a second terminal, said first terminal being coupled with said positive output terminal, a semiconductor switch having a semiconductor body comprising a blocking pn junction, a gate electrode, a source zone of a first conductivity type connected to a first electrode and bordering on a zone forming the blocking pn junction of a second conductivity type complementary to the first conductivity type, and a drain zone of the first conductivity type connected to a second electrode, the side of the zone of the second conductivity type facing the drain zone forming a first surface, and in the region between the first surface and a second surface located between the first surface and the drain zone, areas of the first and second conductivity type nested in one another, wherein the areas of the first and second conductivity type are variably so doped that near the first surface doping atoms in the area of the second conductivity type predominate over those in the area of the first conductivity type, and near the second surface doping atoms in the area of the first conductivity type predominate over those in the area of the second conductivity type, wherein said second electrode is coupled to said second terminal of said inductor and said first electrode is coupled with the negative output terminal of said rectifier, a diode having an anode and a cathode, the anode being coupled with the second terminal of said inductor, a capacitor having a first and second terminal, said first terminal being coupled with the cathode of said diode and the second terminal being coupled with the first electrode of said semiconductor switch, an input current sensor generating a signal proportional to an input current, and a control unit having a first input and a second input and a control output coupled with said gate electrode, wherein said first input receives said signal from said current sensor and said second input is coupled with the first terminal of said capacitor.
Between the first and second surface the electrical field may have a rising course starting from both surfaces. A degree of compensation effected by means of the doping in the areas of the first and second conductivity types may have a monotonic course between the first and second surface. The degree of compensation can also have a stepped course. The first conductivity type can be the n-conductivity type. The areas of the first and second conductivity type can be arranged vertically in the semiconductor body. In the areas of the second conductivity type a degree of compensation effected by means of doping can be varied such that near the first surface acceptor impurities dominate and near the second surface donor impurities dominate. The areas of the second conductivity type may have a roughly circular cross-section in a section parallel to the first surface and to the second surface and assume hexagonal surface packing. The areas of t

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