Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Patent
1997-12-03
1998-12-01
Hecker, Stuart N.
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
320166, H02M 542, H02J 700
Patent
active
058447920
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to supply circuits of the type having a storage capacitor, for supplying a load via a regulation circuit such as a switched-mode circuit.
At the present time, many devices electrically supplied from the mains include a switched-mode power supply. The power is extracted from the network in the form of short current peaks. These current peaks disturb the network efficiency. The effects resulting from these peaks worsen with the number of devices connected to the network and incorporating a switched-mode power supply. Consequently, electric distribution companies have imposed various standards to improve the power factor of the supplies.
FIG. 1 shows a conventional diagram of the providing of a d.c. power supply from the mains. Terminals X and Y of the a.c. power supply are connected to the input terminals of a rectifying bridge 1, the output terminals A and B of which are connected to a storage capacitor C1 and to a load L. It will be assumed that load L incorporates a regulation circuit, for example, a switched-mode power supply, connected to a load. Further, a resistor of low value r for limiting current surges from the system upon its starting is often to be found in series with capacitor C1.
FIG. 2A shows the rectified mains voltage V.sub.Xy and voltage V.sub.AB between terminals A and B (neglecting the effect of resistor r) as functions of time. It is here assumed that at an initial time t0, the voltage across capacitor C1 is higher than the mains voltage. Then, the voltage between terminals A and B corresponds to the voltage across capacitor C1 which progressively discharges into load L. From time t1 on, the rectified mains voltage becomes higher than the voltage across the capacitor and the mains supplies load L and recharges capacitor C1. From time t2 on, the voltage across the capacitor becomes higher than the mains voltage and the load is supplied again by the capacitor. This is repeated at times t3 and t4.
FIG. 2B shows the shape of the current extracted from the mains between times t1-t2 and t3-t4. Given that a sine generator supplies a load and a capacitor which are linear elements, the current is substantially sinusoidal and, more specifically, it corresponds to a sinusoid peak, that is, its shape is substantially parabolic. A characteristic of the current peaks thus is that they are symmetrical with respect to their maximum and that this maximum can be relatively high.
In prior art, several circuits for improving the power factor to reduce and widen these current peaks have been devised. A simple way of doing so is to limit the value of capacitor C1 so that it discharges relatively strongly during each phase when it supplies the load. Accordingly, time t1 will occur sooner in the period and time interval t1-t2 will be higher. Other circuits for improving the power factor provide that capacitor C1 and possibly other associated capacitors charge less, for example only to half the maximum voltage of the rectified mains. Then, time t2 occurs late in the period. However, in both cases, at least a portion of the current extracted from the mains is shaped as the symmetrical peak illustrated in FIG. 2B.
An object of the present invention is to provide a load supply circuit which limits the amplitude and increases the transition angle of the current peaks extracted from the mains.
Another object of the present invention is to provide such a supply circuit wherein the current peaks extracted from the mains are disymmetrical and preferably exhibit a maximum at the beginning of each peak.
The present invention also aims at providing a supply circuit wherein the charge current of the storage capacitor is controllable independently from the type of load supplied.
The present invention also aims at minimizing the consumption of the supply circuit.
The present invention further aims at providing such a circuit for supplying a load incorporating a regulation circuit of switched-mode power supply type, which minimizes the disturbances brought by the switched-mode power supply to th
REFERENCES:
patent: 5087871 (1992-02-01), Losel
patent: 5371667 (1994-12-01), Nakao et al.
patent: 5532572 (1996-07-01), Okamura
patent: 5619115 (1997-04-01), Kajita
patent: 5715154 (1998-02-01), Rault
Patent Abstract of Japan, vol. 018, No. 570 (E-1623), Oct. 31, 1994 & JP 06 209574 A, Jul. 26, 1994.
Hecker Stuart N.
SGS-Thomson Microelectronics S.A.
LandOfFree
Power supply circuit with a storage capacitor 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 supply circuit with a storage capacitor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power supply circuit with a storage capacitor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2400457