Radiant energy is used in a variety of manufacturing processes to treat surfaces, films, and coatings applied to a wide range of materials. Specific processes include, but are not limited to, curing (i.e., fixing, polymerization), oxidation, purification, and disinfection. Processes using radiant energy to polymerize or effect a desired chemical change is rapid and often less expensive in comparison to a thermal treatment. The radiation can also be localized to control surface processes and allow preferential curing only where the radiation is applied. Curing can also be localized within the coating or thin film to interfacial regions or in the bulk of the coating or thin film. Control of the curing process is achieved through selection of the radiation source type, physical properties (for example, spectral characteristics), spatial and temporal variation of the radiation, and curing chemistry (for example, coating composition).
A variety of radiation sources are used for curing, fixing, polymerization, oxidation, purification, or disinfections due to a variety of applications. Examples of such sources include, but are not limited to, photon, electron, or ion beam sources. Typical photon sources include, but are not limited to, arc lamps, incandescent lamps, electrodeless lamps and a variety of electronic (i.e., lasers) and solid-state sources.
An apparatus for irradiating a surface with ultraviolet light includes a lamp (e.g., a modular lamp, such as a microwave-powered lamp having a microwave-powered bulb (e.g., tubular bulb) with no electrodes or glass-to-metal seals), the lamp having reflectors to direct light (photons) on to the surface. The source of microwave power is conventionally a magnetron, the same source of microwaves typically found in microwave ovens. The microwave-powered bulb typically receives microwaves generated by the magnetron through an intervening waveguide.
Conventional power supplies for magnetrons include a variety of designs. A typical design used for powering microwave ovens includes a one step-up resonant laminated transformer, a high voltage diode, and a high voltage capacitor. The transformer/capacitor combination takes a 50 Hz/60 Hz line voltage and outputs a 50/60 Hz half wave pulsed DC voltage or a 100% ripple DC voltage. It has the advantage of low cost, but includes the disadvantages of being large and heavy with a single level of output power.
A second design employs a silicon-controlled rectifier (SCR) to control an amount of phase of an input power sine waveform that may be applied to a laminated transformer. The output windings of the laminated transformer steps up the input voltage which is applied to a full diode bridge. The output is a 50 HZ/60 Hz full wave rectified pulsed DC voltage or 100% ripple DC voltage.
A third possible design is a switching mode power supply which provides a high power DC voltage with low ripple. Conventional high voltage, switching mode power supplies suffer from a number of problems. Because of a high working frequency (>20 KHz), a high frequency, high power single output winding ferrit transformer is needed, along with a small number of high voltage, fast recovery diodes arranged in a diode bridge. The small number of high power, high frequency diodes dissipate a large amount of power. As a result, it is necessary to employ a ferrit transformer with multiple secondary windings coupled to a large number of diode bridges, each comprising 2 or 4 lower voltage diodes as shown in FIG. 1.
Referring now to FIG. 1, a portion of a high voltage switching mode DC power supply 10 includes an AC pulsed input source 12 feeding a primary winding of a multiple output winding laminated transformer 14. The multiple output windings 16a-16l feed a plurality of full-wave rectified diode bridge circuits 18a-18l (also labeled DB1-DB12) requiring a total of 64 diodes. A rippled approximate DC output voltage is smoothed and high frequency components from the switching power supply are removed by a plurality of filter circuits 20a-20l each comprising at least a capacitor and an inductor, labeled C1-C12 (references 22a-22l) and L1-L12 (references 24a-24l), respectively.
Since there is typically a long cable between a power supply and a magnetron in a UV curring lamp assembly, the outputs of the secondary windings 16a-16l of the multiple winding transformer 14 include a high level of high frequency components. For the power supply 10 to drive a magnetron with low frequency DC power with a long transmission cable (not shown), it is necessary to employ a large number of inductors 24a-24l and capacitors 22a-22l, as well as 12 RC snubbers (not shown) employed as filters to remove high frequency components. Thus, a large number of diodes, inductors and capacitors need to be employed, which is expensive, consumes a large amount of board space, and reduces reliability.
Accordingly, what would be desirable, but has not yet been provided, is an inexpensive high voltage and power output DC power supply having a low component count.