电压模式PFM升压DC-DC转换器设计

发布时间：2018-03-23 12:20

本文选题：升压型　切入点：PFM　出处：《哈尔滨工业大学》2014年硕士论文

【摘要】：现如今便携式电子产品正逐渐取代大体积的电子产品进入人们的日常生活、工作和学习中，这些便携式电子产品正常工作需要高性能的电源管理芯片。体积小、效率高、稳压范围宽、噪声小的开关电源，在便携式电子产品中得到了广泛的应用。论文针对市场需求日益增长的电源管理芯片，对电压模式PFM升压DC-DC转换器进行了研究。重点研究了基准电压源、比较器电路、频率可调环形振荡器、启动电路、限流保护电路等开关电源中必备的几个功能模块，并完成了整体电路设计和仿真。论文基于脉冲频率调制方式实现升压DC-DC转换，控制电路采样输出电压，根据输出电压的不同，产生频率可变的脉冲信号作用于功率开关管栅极，控制其导通与关断的时间，进而维持输出电压稳定。为了减小系统处于空载或轻负载时损耗，引入跳周期调制，使脉冲信号在负载较轻时跳过一定的周期，，功率开关管在这段时间内保持关断，使系统处于空闲状态。根据升压型DC-DC转换器输出电压高于输入电压并且稳定的特点，采用输出电压作为芯片中各个模块的电源电压，为了解决系统起始阶段输出电压较低，不能满足模块正常工作的问题，设计了基于电容自举原理的启动电路。为了给电路中电压比较器和迟滞比较器提供稳定的参考电压，设计了二阶曲率补偿带隙基准电路。为了实现脉冲频率可调，设计了可以产生两种频率的环形振荡器，通过控制其延迟单元尾电流的大小产生不同频率。为了根据输出电压的采样信号和基准电压大小，产生控制信号作用于振荡器使其产生不同的频率，设计了采用两级运算放大器和输出级构成电压比较器。当输出电压上升到一定值时，为了控制振荡器跨过一定的周期，设计了迟滞比较器。论文设计的电压模式PFM升压DC-DC转换器基于SMIC0.18μm工艺实现，在输入电压为1.8V，负载电流0~100mA范围内时，输出电压都基本稳定在3V，纹波小于50mV，输入电压允许范围达到了0.9V~2V，最大工作频率为400kHz。在轻负载时效率在90%以上，重载时效率也达到了80%。系统的允许温度工作范围为-30oC~100oC。
[Abstract]:Nowadays, portable electronic products are gradually replacing bulky electronic products in their daily life, working and studying. These portable electronic products need high-performance power management chips to work normally. Switching power supply with wide voltage range and low noise is widely used in portable electronic products. Aiming at the increasing market demand of power supply management chip, this paper studies the voltage-mode PFM boost DC-DC converter, focusing on the reference voltage source, comparator circuit, frequency adjustable ring oscillator, starting circuit, and so on. The circuit design and simulation are completed. Based on the pulse frequency modulation, this paper realizes the boost DC-DC conversion, and the output voltage of the control circuit is sampled. According to the different output voltage, the pulse signal with variable frequency acts on the gate of the power switch tube, and controls the time of its turn-on and turn-off. In order to reduce the loss when the system is under no load or light load, the hopping period modulation is introduced to make the pulse signal skip a certain period when the load is lighter, and the power switch tube remains off during this period. Keep the system idle. According to the characteristics that the output voltage of the boost DC-DC converter is higher than the input voltage and stable, the output voltage is used as the power supply voltage of each module in the chip, in order to solve the problem that the output voltage is low in the initial stage of the system, The starting circuit based on the principle of capacitive bootstrap is designed to provide a stable reference voltage for the voltage comparator and hysteresis comparator in the circuit. The second order curvature compensated bandgap reference circuit is designed. In order to realize the adjustable pulse frequency, a ring oscillator with two frequencies is designed. Different frequencies are generated by controlling the size of the tail current of the delay cell. In order to produce control signals acting on the oscillator to produce different frequencies according to the sampling signal of the output voltage and the magnitude of the reference voltage, A voltage comparator consisting of a two-stage operational amplifier and an output stage is designed. When the output voltage rises to a certain value, a hysteresis comparator is designed to control the oscillator to cross a certain period. The voltage-mode PFM boost DC-DC converter designed in this paper is based on SMIC0.18 渭 m technology. When the input voltage is 1.8 V and the load current is 0~100mA, The output voltage is basically stable at 3 V, the ripple is less than 50 MV, the input voltage is within 0.9V / 2 V and the maximum operating frequency is 400 kHz. The efficiency is over 90% at light load and 80% at heavy load. The allowable temperature range of the system is -30oC ~ (10) oC.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46

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