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DC Power Supply for Dimmable EHID Systems

IP.com Disclosure Number: IPCOM000201299D
Original Publication Date: 2010-Nov-10
Included in the Prior Art Database: 2010-Nov-10
Document File: 5 page(s) / 161K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

Electrodeless High Intensity Discharge (EHID) lamps come with the advantage of superior maintenance and the possibility of having even higher color rendering indices and higher efficacy than electroded HID lamps. Instead of using electrodes to couple the energy into the lighting plasma EHID lamps use couplers - sometimes referred to as applicators - to couple microwave power into the plasma. The microwave power is provided by a power amplifier or power oscillation unit, which is powered by a Direct Current (DC) power supply. In general, the efficiency of power supplies depends on the output power, and can only be optimized for one particular output power. Since EHID lamps can be dimmed over a wide range - a much wider range than electroded HID lamps - the efficiency of the power supply in most operating points is far from optimal. Especially for the maximum dimming level the decrease in efficiency is considerably, since most electronic control gears are optimized for maximum performance.

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DC Power Supply for Dimmable EHID Systems

Idea: Dr. Bernhard Sie├čegger, DE-Munich

Electrodeless High Intensity Discharge (EHID) lamps come with the advantage of superior maintenance and the possibility of having even higher color rendering indices and higher efficacy than electroded HID lamps. Instead of using electrodes to couple the energy into the lighting plasma EHID lamps use couplers - sometimes referred to as applicators - to couple microwave power into the plasma. The microwave power is provided by a power amplifier or power oscillation unit, which is powered by a Direct Current (DC) power supply. In general, the efficiency of power supplies depends on the output power, and can only be optimized for one particular output power. Since EHID lamps can be dimmed over a wide range - a much wider range than electroded HID lamps - the efficiency of the power supply in most operating points is far from optimal. Especially for the maximum dimming level the decrease in efficiency is considerably, since most electronic control gears are optimized for maximum performance.

At present, most EHID systems with dimming capabilities have a control unit (DL) by which the user is able to command the dimming level of the lamp. This command is converted by an interface (Infa) into a brightness command signal (Bcmd) which is fed into the control unit. The light sensor (BrMea) feeds a signal (Br) corresponding to the actual brightness into the control unit. The control unit compares the brightness command signal with the measured brightness. Based upon this, it generates a signal (Pcmd) which regulates the Amplifier (AMP). Such a system is depicted in figure 1. These systems normally come with the problem of low efficiency because of the reasons named above.

A novel solution to the problem described above is presented in the following. In order to boost the efficiency of an EHID lamp in dimming mode, a DC power supply consisting of at least two stages with paralleled outputs is proposed. Such a system is principally depicted in figure 2. When splitting the power supply into several smaller power supplies one of these is running all the time while a second, third, etc. is only activated when needed. The additional power supplies can be triggered by whether a change in the DC voltage, a change in the commanded microwave power or a combination of both. When additional supplies are turned on or off because of a change in the commanded microwave power the control unit is supposed to react before the dc voltage drops, in order to increase the dynamic performance of the EHID. In addition to activating further power supplies, the output voltage of all power supplies involved may be varied simultaneously based upon the loading of the amplifier stage and the commanded power.

Instead of combining the DC power of several supplies, the microwav...