Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Patent
1996-09-06
1998-03-17
Wong, Peter S.
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
363 95, H02J 300, H02M 324
Patent
active
057294453
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The invention relates to a regulated power supply unit with an electronic transformer.
Electronic transformers have been commercially available for a number of years. An "electronic transformer" essentially contains the following assemblies. A first assembly in the form of a full-wave rectifier which, in the case of a normal mains AC voltage of, for example, 230 V and 50 Hz, emits at its output a voltage of about 230 V and 100 Hz. A free-running oscillator forms a second assembly, which normally oscillates at a frequency of about 40 KHz depending on the manufacture of the electronic transformer. An AC voltage of about 230 V is now present at a frequency of 40 KHz and modulated at 100 Hz. A third assembly is formed by a conventional transformer. Because of the high-frequency input voltage, the latter need be only very small in comparison with 50 Hz transformers, and supplies a relatively high power with very high efficiency. For example, an AC voltage of 12 V and 40 KHz is present at the output of the transformer, and is modulated at 100 Hz. A fourth assembly is formed by a phase gating control circuit and/or a phase chopping control circuit. This circuit defines the period of oscillation of the oscillator within the mains oscillation period, and thus the transformed, root-mean-square power. In order to control the period of oscillation of the oscillator, the phase gating control circuit is connected to a potentiometer, on which the root-mean-square value of the oscillator voltage, and thus the output voltage of the electronic transformer, can be set.
The peak value of the output voltage of the electronic transformer is determined by the amplitude of the higher-frequency AC voltage. This peak value changes relatively little with respect to the phase gating control. However, in the adjustment range towards relatively low voltages, difficulties arise with respect to fluctuations in the supply voltage on the primary side of the electronic transformer, and these fluctuations are not regulated out.
If such an electronic transformer is used to supply power to a lighting device which includes, for example, a halogen lamp, then the brightness of the lighting device can be adjusted with the aid of the potentiometer, which is connected to the circuit for phase gating control. It has been found that mains voltage fluctuations are transferred more than proportionally to the load current in the lower, weak brightness region. This is disadvantageous for relatively demanding applications of a lighting device, for example in the case of a microscope.
Power supply units are available which have very good current or voltage stabilization. However, these power supply units are complex and costly.
SUMMARY OF THE INVENTION
The object of the invention is to develop a regulated power supply unit of a generic type such that the output magnitude can be kept as constant as possible over the entire adjustment range, virtually independently of fluctuations in the supply voltage for the power supply unit.
This object is achieved in the case of a power supply unit by the features specified.
A conventional, commercially available electronic transformer, in which the magnitude of the output voltage is controlled by changing a resistance value, can be used in an advantageous manner with the power supply unit according to the invention. This resistance value is normally set with the aid of a potentiometer, according to the prior art.
A basic idea of the invention is to use a transistor as the variable resistor, which is controlled by a regulator such that the output magnitude of the power supply unit is kept as constant as possible, irrespective of mains voltage fluctuations. According to the invention, the actual value for this regulator, the supply voltage for the active components of the regulator, and the formation of the reference value are obtained simultaneously by outputting the higher-frequency AC voltage components on the load side of the regulated power supply unit according to the invention.
One particular advanta
REFERENCES:
patent: 3578914 (1971-05-01), Simonelli
patent: 4506318 (1985-03-01), Nilssen
patent: 5159245 (1992-10-01), Nilssen
patent: 5289360 (1994-02-01), Canova
92/93!, sales brochure of Insta Elektro GmbH & Co. KG. for Low-Voltage Halogen Lamps!, The Electronics Manual from berker GmbH & Co., vol. 4.
Leica Mikroskopie und Systeme GmbH
Vu Bao Q.
Wong Peter S.
LandOfFree
Regulated power supply unit with an electronic transformer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Regulated power supply unit with an electronic transformer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Regulated power supply unit with an electronic transformer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-963750