提出一种可根据负载变化在脉冲宽度调制(pulse width modulation,PWM)和脉冲频率调制(pulse frequency modulation,PFM)两种工作模式间自动切换的降压DC-DC芯片的设计法,推导出临界切换状态下的负载电流值表达式,在此基础上设计了一种PW...提出一种可根据负载变化在脉冲宽度调制(pulse width modulation,PWM)和脉冲频率调制(pulse frequency modulation,PFM)两种工作模式间自动切换的降压DC-DC芯片的设计法,推导出临界切换状态下的负载电流值表达式,在此基础上设计了一种PWM/PFM自动切换的DC-DC芯片.该系统在较大的负载变化范围内均具有较高效率.展开更多
In this paper,a single-switch two-stage DC-DC conversion circuit is proposed for an off-grid solar power application.A photovoltaic(PV)panel powers the load and a storage unit(battery)via the proposed circuit.The batt...In this paper,a single-switch two-stage DC-DC conversion circuit is proposed for an off-grid solar power application.A photovoltaic(PV)panel powers the load and a storage unit(battery)via the proposed circuit.The battery is designed to balance the supply and the demand of power under different irradiation situations.Based on conventional cascaded DC-DC converters,the proposed design is developed with the single switch technique reducing size,cost and power loss.The control scheme in this design is pulse width modulation(PWM)with pulse frequency modulation(PFM).The PWM module is similar to conventional design except its ramp signal with a variable frequency is provided by a resettable integrator.As a result,the PWM and PFM modules regulate the two stages of the proposed circuit separately with the same switching control signal.In this paper,the modes of operation of the circuit are discussed as well as the control schemes.The design process is described along with the circuit analysis and comparisons with conventional design are made as well.A prototype has been built to verify the proposed circuit with simulation and experimental results.展开更多
<span style="font-family:Verdana;">This paper investigates the behaviors of Boost DC Chopper used in Photovoltaic energy systems where the solar irradiation changes during the day time causing current ...<span style="font-family:Verdana;">This paper investigates the behaviors of Boost DC Chopper used in Photovoltaic energy systems where the solar irradiation changes during the day time causing current and voltage changes. Varying the solar irradiation causes output chopper voltage changes in order to keep working at maximum extracted solar power. The chopper voltage changes leading to variable duty cycle operation of chopper switch and causes </span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">significant change in switch losses in terms of the dissipated power. In addition to that the chopper behaviors are studied when the chopper voltage is boosting up to a predetermined reference value leading to </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">significant change in chopper current, voltage, duty cycle and occurred losses. A mathematical model for chopper performances and switch losses </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> derived, and a simulation model using Matlab/ Simulink platforms is conducted to follow the chopper behaviors. Simulation results for concreteSUNPOWER panel type SPR-315E-WHT-D with 315 Watts peak indicates that during the daylight time transistors</span></span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">are exposed to complicated change</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> in their current, voltage and dissipated power. Furthermore changing the output voltage according to load requirements causes heavy stress on the transistor in terms of current, oscillations and losses as well. Simulation results show that there are optimized values of irradiation, chopper voltage and duty cycle where the transistor losses are minimized. In addition to that, projecting the transistor losses over the daylight time</span></span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">at </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">given</span></span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">irradiation rate shows how these losses vary among the year, and the amount of energy dissipated across the main chopper switch which is around 2970 Whr/yr for</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> the</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> present case. Furthermore, the conducted simulation also shows the occurred in the transistor behaviors when solar irradiation changes, and can be serving for further studies.</span></span></span>展开更多
文摘提出一种可根据负载变化在脉冲宽度调制(pulse width modulation,PWM)和脉冲频率调制(pulse frequency modulation,PFM)两种工作模式间自动切换的降压DC-DC芯片的设计法,推导出临界切换状态下的负载电流值表达式,在此基础上设计了一种PWM/PFM自动切换的DC-DC芯片.该系统在较大的负载变化范围内均具有较高效率.
文摘In this paper,a single-switch two-stage DC-DC conversion circuit is proposed for an off-grid solar power application.A photovoltaic(PV)panel powers the load and a storage unit(battery)via the proposed circuit.The battery is designed to balance the supply and the demand of power under different irradiation situations.Based on conventional cascaded DC-DC converters,the proposed design is developed with the single switch technique reducing size,cost and power loss.The control scheme in this design is pulse width modulation(PWM)with pulse frequency modulation(PFM).The PWM module is similar to conventional design except its ramp signal with a variable frequency is provided by a resettable integrator.As a result,the PWM and PFM modules regulate the two stages of the proposed circuit separately with the same switching control signal.In this paper,the modes of operation of the circuit are discussed as well as the control schemes.The design process is described along with the circuit analysis and comparisons with conventional design are made as well.A prototype has been built to verify the proposed circuit with simulation and experimental results.
文摘<span style="font-family:Verdana;">This paper investigates the behaviors of Boost DC Chopper used in Photovoltaic energy systems where the solar irradiation changes during the day time causing current and voltage changes. Varying the solar irradiation causes output chopper voltage changes in order to keep working at maximum extracted solar power. The chopper voltage changes leading to variable duty cycle operation of chopper switch and causes </span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">significant change in switch losses in terms of the dissipated power. In addition to that the chopper behaviors are studied when the chopper voltage is boosting up to a predetermined reference value leading to </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">significant change in chopper current, voltage, duty cycle and occurred losses. A mathematical model for chopper performances and switch losses </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> derived, and a simulation model using Matlab/ Simulink platforms is conducted to follow the chopper behaviors. Simulation results for concreteSUNPOWER panel type SPR-315E-WHT-D with 315 Watts peak indicates that during the daylight time transistors</span></span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">are exposed to complicated change</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> in their current, voltage and dissipated power. Furthermore changing the output voltage according to load requirements causes heavy stress on the transistor in terms of current, oscillations and losses as well. Simulation results show that there are optimized values of irradiation, chopper voltage and duty cycle where the transistor losses are minimized. In addition to that, projecting the transistor losses over the daylight time</span></span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">at </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">a </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">given</span></span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">irradiation rate shows how these losses vary among the year, and the amount of energy dissipated across the main chopper switch which is around 2970 Whr/yr for</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> the</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> present case. Furthermore, the conducted simulation also shows the occurred in the transistor behaviors when solar irradiation changes, and can be serving for further studies.</span></span></span>
