Abstract:
A programmable photo-coupler-isolated wide band modulator for high voltage power supply is disclosed, which utilizes a high voltage module to step up the input voltage and utilizes a wide band modulator connected with the high voltage module to modulate the high voltage output from the high voltage module for outputting a wide band high voltage, wherein the wide band modulator receives a modulator signal generated by a computer for modulating.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to power supplies and, more particularly, to a programmable photo-coupler-isolated wide band modulator for high voltage power supply which can be applied to many fields, such as capillary electrophoresis power or hybrid electric field power in biomedical field, photomltiplier tubes or avalanche photodiodes in electro-optical field, solid state detectors or ion pumps in electric field.  
           [0003]    2. Description of Related Art  
           [0004]    A conventional power supply can only supply fixed voltage or current and does not have a modulation capability. There are a number of commercially available waveform generators capable of generating waveforms. However, an output voltage of the waveform generator is typically limited to be less than or equal to 15 V. Further, some available high voltage modulators can only output fixed voltage or have a small modulation capability, i.e., have narrow modulation bandwidth or no wide band modulation capability.  
           [0005]    Currently, high voltage (e.g., up to several tens KV) and wide band modulation are required in many applications such as radar sets, X-ray devices, semiconductor machines, etc. However, the prior art power supply, as stated above, does not have the desired capability.  
           [0006]    Therefore, it is desirable to provide a novel power supply capable of supplying high voltage and having a wide band modulation capability in order to mitigate and/or obviate the aforementioned problems.  
         SUMMARY OF THE INVENTION  
         [0007]    An object of the present invention is to provide a programmable photo-coupler-isolated wide band modulator for high voltage power supply. The power supply has the advantages of programmable control, wide band modulation and continuous adjustment.  
           [0008]    To achieve the object, the present invention provides a programmable power supply comprising a low voltage power supply unit providing at least one low voltage; an frequency converter unit for receiving the low voltage and converting it into a high frequency low AC voltage; a high voltage module for receiving the AC voltage and increasing the AC voltage; and a wide band modulation module coupled to the high voltage module for converting the AC voltage into a DC voltage and receiving an external modulated signal, the modulated signal being activated to switch the DC voltage for generating and outputting a wide band modulated DC voltage.  
           [0009]    Other objects, advantages, and novel features of the invention will become more apparent from the detailed description when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a block diagram of a wide band modulator for high voltage power supply according to the invention;  
         [0011]    [0011]FIGS. 2 a  and  2   b  are circuit diagrams of transformer isolator, optical coupler isolator and high voltage switch assembly showing single and double polarity outputs respectively; and  
         [0012]    [0012]FIGS. 3 a ,  3   b ,  3   c  and  3   d  are waveforms showing 30 KV of DC (direct current) output, modulated 30 KV, modulated −5 KV, and modulated 5 KV and −5 KV respectively. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    With reference to FIG. 1, there is shown a modulation device for high voltage power supply in accordance with the invention comprising a low voltage power supply unit  11 , an frequency converter unit  13 , a high voltage module  14  including a high voltage switch assembly  141 , a wide band modulation module  15  including a transformer isolator circuit  151  and an photo-coupler-isolated circuit  152  including a plurality of optical couplers  1521 , a logic IO (input/output) interface  16 , a protection module  17 , and a gate driver module  18 . Each component is described in detail below.  
         [0014]    An input voltage of the low voltage power supply unit  11  is 110 V AC (alternating current). A plurality of outputs of low DC voltage are generated by the low voltage power supply unit  11 . For example, 5 V DC or 15 V DC are two exemplary voltage outputs for normal operation of other components. The frequency converter unit  13  receives one voltage output from the low voltage power supply unit  11  and converts it into a high frequency low AC voltage which is in turn sent to the high voltage module  14  for increasing voltage. The protection module  17  is coupled to the high voltage module  14 , the logic IO interface  16 , and the gate driver module  18  respectively. As such, a PC (personal computer)  12  can control the protection module  17  via the logic IO interface  16  and control the high voltage module  14 , the gate driver module  18 , and the frequency converter unit  13  via the protection module  17  for protection against over current, over voltage, etc.  
         [0015]    The high voltage module  14  increases the high frequency low AC voltage by its internal booster circuit and rectifier circuit for supplying a constant high voltage such as several tens KV or preferably 50 KV. The high voltage is then fed to the high voltage switch assembly  141 . With reference to FIG. 2 a , operations of the transformer isolator circuit  151 , the photo-coupler-isolated circuit  152 , and the high voltage switch assembly  141  are illustrated in which a single polarity output is obtained. In detail, the transformer isolator circuit  151  can isolate low voltage input side from high voltage output side and store electrical energy. In the embodiment, the low voltage input is a low AC voltage which is supplied by a small power supply (not shown) or the low voltage power supply unit  11 . The low AC voltage is fed to a primary coil of a transformer  1511 . Next, a plurality of voltage outputs are generated at a secondary coil of the transformer  1511 . The voltage outputs are then rectified and regulated by respective pairs of diode  1512  and voltage regulator  1513  sequentially for generating a constant voltage which is fed to the corresponding optical coupler  1521  of the photo-coupler-isolated circuit  152 . The photo-coupler-isolated circuit  152  is interconnected between the transformer isolator circuit  151  and the high voltage switch assembly  141  for switching (i.e., controlling) the on/off of each high voltage switch  1411  of the high voltage switch assembly  141  and providing a feedback compensation to the modulate device. Each optical coupler  1521  receives a modulated signal from the PC  12 . The modulated signal is switched to provide a wide band modulated DC voltage (e.g., at about 100 KHz) and have a high bandwidth to period ratio. The high voltage switch  1411  is implemented as a transistor capable of permitting a voltage input of several hundred volts such as 800V in the embodiment. High voltage input of the high voltage switch assembly  141  is Va. A continuous modulated high voltage from about 0V to about 30 KV is outputted at Vo. With reference to FIG. 2 b , there is shown a modification of the FIG. 2 a  circuit. In detail, the circuitry of the high voltage switch assembly  141  is changed in which Va and Vb are positive and negative high voltage inputs respectively and Vo is double polarity high voltage output (e.g., 15 KV or −15 KV). The PC  12  can effect a programmable control on the modulated voltage waveforms for generating high or low voltage waveforms and display voltage outputs. Also, the PC  12  can replace a programmable single chip or a signal generator capable of modulating signal waveforms.  
         [0016]    With reference to FIGS. 3 a ,  3   b ,  3   c , and  3   d  there are shown waveforms of 30K VDC output, modulated 30K VDC modulated by the PC  12 , modulated −5 KV, and modulated 5 KV and −5 KV respectively.  
         [0017]    Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.