| As the core equipment of integrated circuit manufacturing,lithography machine is known as the "pearl on the crown of semiconductor industry".It integrates the top technologies in the fields of optics,hydrodynamics and polymer physics.It has become an important symbol to measure the level of scientific and technological development of a country.The wafer stage is the key subsystem of the lithography machine,and its performance directly affects the characteristic dimensions,overlay and throughput of lithography machine.The planar motor and power amplifier(converter),as the core components of the wafer stage,together with the controller and optical sensor,constitute a ultra-precision motion system with multi-degree of freedom.The current nonlinear distortion of power amplifier causes motion trajectory error and positioning error of planar motor,affect the ultra precision motion and positioning performance of wafer stage,and restrict the manufacturing process of lithography machine.Therefore,the power amplifier needs to meet the requirements of high dynamic and low nonlinear distortion.On the basis of summarizing the advantages and disadvantages of existing power amplifier topology and related technologies,a resonant pole-based dual buck soft-switching power amplifier(RPDBSPA)scheme is proposed in this thesis,then the model establishment of dual buck soft-switching topology,analysis and control of nonlinear voltage error,suppression of cross coupling error and compensation of back EMF disturbance are researched.Firstly,this thesis introduces the topology and operation mechanism of resonant pole-based dual buck soft-switching circuit.The state space average and resonant commutated model of the soft-switching topology are established.Based on the resonant model of soft-switching topology,the sequential mode of soft-switching is analyzed,the modal equations of each state are derived,and the condition and boundary of soft-switching mode conversion are obtained.Based on sequential mode of soft-switching topology,the effects of auxiliary resonant branch circuit parameters on soft-switching conditions and current stress are analyzed.The effects of parasitic parameter loop on voltage stress of auxiliary branch switches are researched,and the duty cycle boundary of the main switching device under different load conditions is derived.In addition,according to the current cycling path of soft-switching topology,the influence of circulating current on the system is analyzed.In order to achieve low nonlinear distortion current,the topology of RPDBSPA should have high linear output characteristics,and its nonlinear voltage error should be analyzed and suppressed.Therefore,the nonlinear voltage error related to inductor current and the voltage error of soft-switching resonant commutation with its control method are researched.Firstly,by analyzing the discontinuous conduction mode(DCM)and continuous conduction mode(CCM)of inductance current,the expression of switching-node voltage are obtained,and the mechanism of current zero crossing distortion caused by nonlinear voltage in discontinuous conduction mode is revealed.The effects of two zero crossing distortion suppression methods by injecting bias current on current harmonics are compared and analyzed.Secondly,the softswitching resonant branch introduces nonlinear ramp voltage and zero voltage error at the switching-node,and the zero voltage time is the key factor affecting the nonlinear voltage error of resonant commutation.Based on the resonant equivalent model under unbalanced voltage sharing,the expression of zero voltage time is derived,and the influence of unbalanced voltage sharing on the key modes and zero voltage time of soft-switching is analyzed.On this basis,a nonlinear voltage error suppression method based on zero voltage time control is proposed.Considering the difference between the mathematical model established under ideal circuit conditions and the actual physical model,the current nonlinear distortion of dual buck soft-switching topology under non-ideal circuit conditions is researched in this thesis.Firstly,the mathematical model of dual buck soft-switching topology under non-ideal circuit conditions is established,and the expressions of bias current and output current are derived.It is revealed that incomplete current decoupling will introduce cross coupling error under non-ideal circuit conditions.Secondly,the current error characteristics under cross phase modulation and in-phase modulation are compared and analyzed theoretically.Compared with in-phase modulation,the current error under cross phase modulation is smaller and the current can achieve lower nonlinear distortion.Then,the influence of cross coupling error on output current under non-ideal circuit conditions is summarized,and and a coupling error suppression method based on gain parameter optimization under cross phase modulation is proposed.The establishment and analysis of topological mathematical model under non-ideal circuit conditions reveal the influence mechanism of cross coupling error on output current,and provide theoretical guidance and basis for the selection of circuit components.After analyzing and summarizing the above researches,in order to achieve the output current of low nonlinear distortion,it is necessary to research the closed loop control strategy of power amplifier.Firstly,the LC filter can optimize the output current harmonic characteristics of the system and LCL link is formed in circuit topology,which makes the pole position of the system shift and affects the stability of the system.Therefore,this thesis analyzes the active damping compensation method based on harmonic current feedback to improve the stability of the system,and compares the suppression effect of different damping degree on the resonance peak.Secondly,considering the back EMF induced by load,the influence of back EMF on the output current is analyzed.A back EMF compensation strategy based on bias current decoupling is proposed to suppress the influence of back EMF on current harmonics.Then,according to the performance requirements of the system,a prototype of RPDBSPA with DC bus voltage of 500 V,switching frequency of 100 k Hz and output current of 12.5A is established.The performance indicators are as follows:current loop bandwidth >5k Hz,peak current is 12.5A,total harmonic distortion(THD)<0.070%. |
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