CN105827112B - 一种buck变换器 - Google Patents

一种buck变换器 Download PDF

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CN105827112B
CN105827112B CN201610367298.9A CN201610367298A CN105827112B CN 105827112 B CN105827112 B CN 105827112B CN 201610367298 A CN201610367298 A CN 201610367298A CN 105827112 B CN105827112 B CN 105827112B
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detection circuit
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error amplifier
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CN105827112A (zh
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明鑫
李要
何烨
王卓
张波
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/157—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators with digital control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0032—Control circuits allowing low power mode operation, e.g. in standby mode
    • H02M1/0035—Control circuits allowing low power mode operation, e.g. in standby mode using burst mode control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

本发明属于电子技术领域，涉及一种BUCK变换器。本发明的电路在中等负载及重负载情况下，系统工作于PWM模式；在轻载情况下，系统工作在DCM模式；在超轻载情况下，系统自动切换到休眠模式，在休眠模式下，系统关闭芯片不必要的模拟电路，将静态功耗降低到最低。

Description

一种BUCK变换器
技术领域
本发明属于电子技术领域，涉及一种具有低功耗特性的BUCK变换器。
背景技术
近年来，随着中国经济的发展和电子行业的兴起，消费类电子产品，特别是便携式电子设备的快速普及，电源管理半导体产品市场近期呈现快速增长趋势，BUCK变换器在计算机、通信、工业自动化、电子或电工仪器等领域应用更加广泛，低功耗、高效率、小尺寸的功率转换系统需求量越来越大，便携式电子产品功能越来越多样化，如移动电话已经集成了照相机，摄像机，多媒体播放器、视频通话等诸多功能。随着这些功能的提高，其对功耗的要求也在不断提高，节约功耗越来越重要。这些要求已经集中体现在电源设计上，最终归结为系统的工作电流和待机电流。众所周知，在便携式电子产品正常运行时，许多功能都处于关闭和待机状态，而如何实现在待机状态下的低功耗，延长电池使用时间和寿命，成为电源系统设计者的严峻挑战。
发明内容
本发明所要解决的，就是针对上述问题，提出一种适用于Buck变换器的节约系统功耗电路，在较轻载情况下，系统自动切换到休眠模式，在休眠模式下，系统关闭芯片不必要的模拟电路，将静态功耗降低到最低，提高效率。
本发明的技术方案是：如图1所示，一种具有低功耗特性的BUCK变换器，包括驱动模块、PMOS功率管、NMOS功率管、采样电路、误差放大器、PWM比较器、过零检测电路、睡眠模式检测电路、第一逻辑运算模块和第二逻辑运算模块；PMOS功率管的源极接电源，NMOS功率管的漏极接PMOS功率管的漏极，NMOS功率管的源极接地；PMOS功率管漏极和NMOS功率管漏极的连接点为BUCK变换器输出端，PMOS功率管栅极和NMOS功率管栅极接驱动模块的输出端；采样电路接BUCK变换器输出端，误差放大器的反相输入端接采样电路的输出端，误差放大器的同相输入端接第一基准电压，误差放大器的输出端接睡眠模式检测电路的输入端；过零检测电路的输入端接BUCK变换器的输出端，过零检测电路的输出端接第一逻辑运算模块的一个输入端，第一逻辑运算模块的另一个输入端接睡眠模式检测电路的输出端，第一逻辑运算模块的输出端接第二逻辑运算模块的一个输入端，第二逻辑运算模块的另一个输入端接PWM比较器的输出端；PWM比较器的反相输入端接加法器的输出端，PWM比较器的同相输入端接第二基准电压；加法器的一个输入端接采样电路输出端，加法器的另一个输入端接斜坡信号；所述睡眠模式检测电路在误差放大器输出信号的控制下输出睡眠信号，睡眠信号用于控制系统是否进入休眠模式；所述第一逻辑运算模块用于在过零检测电路输出有效信号的条件下输出睡眠信号；所述第二逻辑模块用于在睡眠信号有效的情况下输出数据信号到驱动模块，在睡眠信号无效的情况下输出PWM信号到驱动模块。
本发明的有益效果为，在中等负载及重负载情况下，系统工作于PWM模式；在轻载情况下，系统工作在DCM模式；在超轻载情况下，系统自动切换到休眠模式，在休眠模式下，系统关闭芯片不必要的模拟电路，将静态功耗降低到最低。
附图说明
图1为本发明的系统架构图；
图2为DCM模式下系统的输出波形图；
图3为超轻载判断实际电路图；
图4为数字逻辑处理模块；
图5为休眠模式下系统的输出波形图。
具体实施方式
下面结合附图，详细描述本发明的技术方案：
本发明的Buck变换器系统架构如图1所示，包括驱动模块、PMOS功率管、NMOS功率管、采样电路、误差放大器、PWM比较器、过零检测电路、睡眠模式检测电路、第一逻辑运算模块和第二逻辑运算模块；PMOS功率管的源极接电源，NMOS功率管的漏极接PMOS功率管的漏极，NMOS功率管的源极接地；PMOS功率管漏极和NMOS功率管漏极的连接点为BUCK变换器输出端，PMOS功率管栅极和NMOS功率管栅极接驱动模块的输出端；采样电路接BUCK变换器输出端，误差放大器的反相输入端接采样电路的输出端，误差放大器的同相输入端接第一基准电压，误差放大器的输出端接睡眠模式检测电路的输入端；过零检测电路的输入端接BUCK变换器的输出端，过零检测电路的输出端接第一逻辑运算模块的一个输入端，第一逻辑运算模块的另一个输入端接睡眠模式检测电路的输出端，第一逻辑运算模块的输出端接第二逻辑运算模块的一个输入端，第二逻辑运算模块的另一个输入端接PWM比较器的输出端；PWM比较器的反相输入端接加法器的输出端，PWM比较器的同相输入端接第二基准电压；加法器的一个输入端接采样电路输出端，加法器的另一个输入端接睡眠模式检测电路的输出端；所述睡眠模式检测电路在误差放大器输出信号的控制下输出睡眠信号，睡眠信号用于控制系统是否进入休眠模式；所述第一逻辑运算模块用于在过零检测电路输出有效信号的条件下输出睡眠信号；所述第二逻辑模块用于在睡眠信号有效的情况下输出数据信号到驱动模块，在睡眠信号无效的情况下输出PWM信号到驱动模块。
本发明的工作原理是：
首先是Vout经过电阻分压产生VFB，EA模块是误差放大器，用来比较FB与REF1的电压大小，在中等负载及重负载情况下，系统工作于PWM模式，睡眠模式信号一直为是低电平，系统不会进入睡眠模式；在轻载情况下，系统工作在DCM模式，系统的输出波形如图2所示，睡眠模式信号也是一直为低电平，系统不会进入睡眠模式；在超轻载情况下，误差放大器的输出会发生翻转，进而导致睡眠检测模块翻转，由于在轻载下会触发过零，过零检测信号也会翻转，最终睡眠模式信号就会翻转，系统进入睡眠模式，在睡眠模式下，系统关闭芯片不必要的模拟电路以及主开关管和同步整流管以降低静态功耗与开关损耗。
判断系统是否进入超轻载模式的实际电路图如图3所示，对于Buck变换器，当负载变轻时，输出电压的纹波会变大，就会使误差放大器输出低电平，即A处电压为低电平，MP1开启，恒定电流源I1对电容C1充电，B处电压慢慢上升，充电一段时间后，B处电压达到施密特触发器Smit1的阈值电压，就会使误差放大器输出翻转，误差放大器输出变为高电平。可以求出使施密特触发器翻转所需要的时间，则有：
I1·t＝C1·Vth_Smit
根据上述分析，在超轻载模式下，误差放大器输出低电平，如果VFB在t时间段内都是大于VREF1的，也就是说误差放大器输出在t时间段都是低电平，误差放大器输出就会翻转为高电平。误差放大器输出变为高电平就会使系统进入休眠模式，系统关闭芯片大部分的模拟电路，除了误差放大器和PWM比较器还工作，将静态功耗降低到最低，其逻辑控制模块如图4所示，Ctrl1在系统正常工作时为高电平，Ctrl2为低时开上功率管，为高时开下功率管，由于在超轻载模式下，会发生过零，过零检测信号会变高，反相器Inv1输出为高，一旦误差放大器输出变为高电平就会使睡眠模式信号变为高电平，系统进入睡眠模式，进入休眠模式后，系统会关闭除了误差放大器和PWM比较器外的大部分的模拟电路，关断主功率管和同步整流管，从而可以降低系统静态功耗和开关损耗，提高效率。
在休眠模式下系统的输出波形如图5所示，由上述分析可以得到，在轻载变轻时，开关周期比较长，在这阶段保持低功耗变得很重要，由于负载很轻，当触发过零后，上下功率管都关闭，输出电压靠负载慢慢放电，这段时间会很长，所以我们希望在超轻载情况下系统进入休眠模式，系统关闭芯片不必要的模拟电路以及主开关管和同步整流管以降低静态功耗与开关损耗。根据我们对图3和图4的分析可以得到，在超轻载情况下，一旦误差放大器输出变为高电平就会使睡眠模式信号变为高电平，系统进入睡眠模式，T1时间内，系统进入睡眠模式，在T1时间段系统会关闭除了误差放大器和PWM比较器外的大部分的模拟电路，降低系统静态功耗；当VFB降到VREF1时，误差放大器输出会立刻变为低电平，会使睡眠模式信号从高电平变为低电平，系统退出睡眠模式，系统重新正常工作。EA模块的基准参考电压VREF1比PWM比较器基准参考电压VREF大，从图5中可以看出，VFB碰到VREF1时就会退出休眠模式，离碰到VREF还要一段时间，VREF1比VREF大5mv左右比较合适，相当于预留一段时间使关闭的模块重新正常工作，当VFB碰到VREF时，会开启下一周期，系统重新正常工作。
本发明的有益效果是设计出一种基于COT模式Buck变换器的节约系统功耗电路，在中等负载及重负载情况下，系统工作于PWM模式；在轻载情况下，系统工作在DCM模式；在超轻载情况下，系统自动切换到休眠模式，在休眠模式下，系统会关闭除了误差放大器和PWM比较器外的大部分的模拟电路，关断主功率管和同步整流管，从而可以降低系统静态功耗和开关损耗，提高效率。

Claims (1)

1.一种BUCK变换器，包括驱动模块、PMOS功率管、NMOS功率管、采样电路、误差放大器、PWM比较器、过零检测电路、睡眠模式检测电路、第一逻辑运算模块和第二逻辑运算模块；PMOS功率管的源极接电源，NMOS功率管的漏极接PMOS功率管的漏极，NMOS功率管的源极接地；PMOS功率管漏极和NMOS功率管漏极的连接点为BUCK变换器输出端，PMOS功率管栅极和NMOS功率管栅极接驱动模块的输出端；采样电路接BUCK变换器输出端，误差放大器的反相输入端接采样电路的输出端，误差放大器的同相输入端接第一基准电压，误差放大器的输出端接睡眠模式检测电路的输入端；过零检测电路的输入端接BUCK变换器的输出端，过零检测电路的输出端接第一逻辑运算模块的一个输入端，第一逻辑运算模块的另一个输入端接睡眠模式检测电路的输出端，第一逻辑运算模块的输出端接第二逻辑运算模块的一个输入端，第二逻辑运算模块的另一个输入端接PWM比较器的输出端；PWM比较器的反相输入端接加法器的输出端，PWM比较器的同相输入端接第二基准电压；加法器的一个输入端接采样电路输出端，加法器的另一个输入端接斜坡信号；所述睡眠模式检测电路在误差放大器输出信号的控制下输出睡眠信号，睡眠信号用于控制系统是否进入休眠模式；所述第一逻辑运算模块用于在过零检测电路输出有效信号的条件下输出睡眠信号；所述第二逻辑模块用于在睡眠信号有效的情况下输出数据信号到驱动模块，在睡眠信号无效的情况下输出PWM信号到驱动模块。
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