Abstract:
A method for building a model of a multi-phase PWM-based converter is disclosed. The method includes the steps of: defining circuit diagrams and electronic characteristics of a circuit of the multi-phase PWM-based converter; defining configuration of a model of the multi-phase PWM-based converter, and defining characteristics of the model according to the circuit diagrams and the electronic characteristics; and building the model of the multi-phase PWM-based converter.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a method for building a model of a multi-phase PWM-based converter.  
         [0003]     2. General Background  
         [0004]     In recent years, with the development of performance of CPUs, it&#39;s urgent in demands for converters which have lower output voltage and higher output current. Furthermore, heat performance, electro magnetic interference, and load transient of the converters need to be improved urgently. Conventional single-phase PWM (pulse width modulation) based converters suffer from high total harmonic distortion and poor power factor. On the contrary, multi-phase PWM-based converters solve all problems that the CPUs bring.  
         [0005]     Usually, the multi-phase PWM-based converters, CPU, and other loads are assembled in a same printed circuit board. It&#39;s discommodious to complete aforehand performance evaluation experiments. Then it&#39;s more and more important to utilize simulation mode to evaluate performances of the multi-phase PWM-based converters. Cadence OrCAD Pspice (hereinafter “Pspice”) is a widely used simulation software during the period of designing the multi-phase PWM-based converters. A main problem solved by the Pspice software is accuracy and integrality of models&#39; parameters of the multi-phase PWM-based converters.  
         [0006]     However, accurate Pspice models of the multi-phase PWM-based converters are very difficult to design because of complicated inner circuit configuration of the multi-phase PWM-based converters.  
         [0007]     Therefore, what is needed is a method for building a model of a multi-phase PWM-based converter, by which the users can directly put the model into real circuits for simulation.  
       SUMMARY  
       [0008]     A method for building a model of a multi-phase PWM-based converter in accordance with a preferred embodiment of the present invention is provided. The method comprises the steps of: defining circuit diagrams and electronic characteristics of a circuit of a multi-phase PWM-based converter; defining configuration of the model, and defining characteristics of the model according to the defined circuit diagrams and the electronic characteristics; and building the model of the multi-phase PWM-based converter.  
         [0009]     Furthermore, a method for building a model of a multi-phase PWM-based DC/DC converter is provided. The method comprises the steps of: deconstructing a circuit of the multi-phase PWM-based DC/DC converter into a main PWM circuit and an assistant circuit; deconstructing the main circuit and the assistant circuit into a plurality of sub-circuits according to their functions; building models of the sub-circuits, and defining a configuration of a model of the multi-phase PWM-based DC/DC converter; and incorporating models of all the sub-circuits into the model of the multi-phase PWM-based DC/DC converter according to the configuration.  
         [0010]     Other advantages and novel features of the present invention will be drawn from the following detailed description of a preferred embodiment and preferred method with the attached drawings, in which:  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a schematic diagram of a single-phase PWM-based IC in accordance with a preferred embodiment of the present invention;  
         [0012]      FIG. 2  is a flowchart of a preferred method for building a model of a multi-phase PWM-based converter;  
         [0013]      FIG. 3  is a flowchart of a preferred method for building a model of a multi-phase PWM-based DC/DC converter;  
         [0014]      FIG. 4  is a schematic diagram of structure of an assistant circuit of  FIG. 3 ; and  
         [0015]      FIG. 5  is schematic diagram of structure of a main PWM circuit of  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]      FIG. 1  is a simple schematic diagram of a single-phase PWM-based IC (integrated circuit) in accordance with a preferred embodiment of the present invention. The single-phase PWM-based IC comprises a voltage error amplifier  1 , a PWM comparator  2 , an RS (reset and set) trigger  3  and a wave generator  4 .  
         [0017]     The voltage error amplifier  1  has four ports. The four ports include a negative input port, a positive input port, a V+ port, and an output port. The negative input port of the voltage error amplifier  1  inputs a feedback voltage  6 . The positive input port is connected with a positive port of a reference voltage  5 . The V+ port is directly connected with a ground line. The output port is connected with a negative input port of the PWM comparator  2 . A positive input port of the PWM comparator  2  is connected with an S input port of the RS trigger  3  through the wave generator  4 . An output port of the PWM comparator  2  is connected with an R input port of the RS trigger  3 . The RS trigger  3  outputs signals through a Q output port or a Q− output port. The positive input port of the PWM comparator  2  receives saw-tooth waves from the wave generator  4  for modulating pulse width. The S input port of the RS trigger  3  receives square waves from the wave generator  4  for triggering the RS trigger  3 .  
         [0018]      FIG. 2  is a flow chart of a preferred method for building a model of a multi-phase PWM-based converter. In step S 200 , a user defines circuit diagrams and electronic characteristics of a circuit of the multi-phase PWM-based converter by a computing device. The circuit diagrams are defined according to their functions. In step S 201 , the user defines configuration of the model, and defines characteristics of the model according to the defined circuit diagrams and the electronic characteristics. In step S 202 , the computing device builds the model of the multi-phase PWM-based converter according to the configuration and the characteristics of the model. After the model is successfully built, the user can put the model into a circuit for simulation, and optimize the model by comparing simulation results with testing results of the circuit.  
         [0019]      FIG. 3  is a flow chart of a preferred method for a building a model of a multi-phase PWM-based DC/DC converter. In step S 301 , a user deconstructs a circuit of the multi-phase PWM-based DC/DC converter into a main PWM circuit and an assistant circuit by a computing device. Then, the user defines electronic characteristics of the main PWM circuit and the assistant circuit. In step  302 , the user deconstructs the main PWM circuit and the assistant circuit into a plurality of sub-circuits respectively according to their functions, and defines electronic characteristics of each sub-circuit. In step S 303 , the computing device builds a model for each sub-circuit according to its electronic characteristics, and defines configuration of the model of the multi-phase PWM-based DC/DC converter. In step S 304 , the computing device incorporates models of all the sub-circuits into the model of the multi-phase PWM-based DC/DC converter according to the configuration.  
         [0020]      FIG. 4  is a schematic diagram of structure of the assistant circuit of  FIG. 3 . The assistant circuit comprises a droop amplifier  71 , a reference circuit  72 , a power good amplifier  73 , a current limit circuit  74 , and a voltage identification analog/digital (VID A/D) conversion circuit  75 . The droop amplifier  71  is used for protecting over voltage and under voltage. The reference circuit  72  is used for providing a reference voltage for the voltage error amplifier  1 . The power good amplifier  73  is used for outputting power good signals denoting that the circuit of the multi-phase PWM-based DC/DC converter begins to work. The current limit circuit  74  provides current protection functions. The VID A/D conversion circuit  75  is used for converting analog signals t to digital signals, or converting digital signals to analog signals.  
         [0021]      FIG. 5  is a schematic diagram of structure of the main PWM circuit of  FIG. 3 . The main PWM circuit comprises a multi-phase PWM IC  80  and a current sense amplifier  81 . The current sense amplifier  81  is used for assuring that output currents of all conversion channels are average. The multi-phase PWM IC  80  comprises a plurality of single-phase PWM ICs  800  (only one shown) and a clock generator  810 . Each single-phase PWM IC  800  comprises a voltage error amplifier  8010 , a PWM comparator  8020 , an RS trigger  8030 , and a driving circuit  8040 .  
         [0022]     Although the present invention has been specifically described on the basis of a preferred embodiment and preferred method, the invention is not to be construed as being limited thereto. Various changes or modifications may be made to the embodiment and method without departing from the scope and spirit of the invention.