A single-inductor dual-output buck converter with self-adapted PCCM method

II. CIRCUIT ARCHITECTURE AND CONTROL STRATEGY
Fig. I shows the power stage of the proposed
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Yang Yang is the Ph. D student with the Institue of VLSI, Zhejiang University, Hangzhou, China. Email: yangyang@vlsLzj Sun Liang is the master student with the Institue of VLSI, Zhejiang University, Hangzhou, China. Wu Xiaobo is the professor with the Institue ofVLSI, Zhejiang University, Hangzhou , China.
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Advantage: drive large load with small ripple Disadvantage: cross regulation and hard compensation
DCM
Advantage: no cross regulation and easy compensation Disadvantage: large current ripple when drive large load
Fig. 2 Features of CCM and DCM.
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3.3V. And the conversion efficiency of 88% at 300mW is achieved. Keywords: sino, PCCM, Buck
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Sp. T1 and T2 are two complementary phases. During T1,
converter controller is presented, which operates in (PCCM) with adjustable de current levels. Freewheel switching control has been introduced to realize large load current with smaller current ripple, while cross regulation can be minimized. Furthermore, the de current level of subconverters can be adjusted according to each load. The controller was designed and fabricated in 1.5
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Fig. 1 Power stage of the timing diagram.
I. INTRODUCTION
It is important to minimize the power supply in
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smo buck converter and the
portable electronic equipments such as personal digital assistants (PDA), microprocessors, mobile phones, etc. Thus, the power supply with multiple and variable output voltage has got great attentions[I]. However, the conventional solutions usually use multiple inductors in it[2], which is huge in volume, costly and has weak immunity to electro magnetic interference (EMI). In this paper, a single-inductor dual-output buck converter controller is proposed. With a proposed freewheel switching control, the current of inductor maintains above zero as a CCM converter does to handle large current with smaller current ripple, and the cross regulation can be minimized also. Using current sensor and other functional circuits, the inductor de current of subconverters can be adjusted according to different loads, thus the self-adapted control strategy is realized.
PCCM (with a fixed dc level) Advantage: no cross regulation, easy compensation and small ripple when drive large load
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PCCM (with different dc levels) Advantage: no cross regulation, easy compensation, small ripple when drive large load and adapt to different loads Tsadrntar: crn nOf driy variiable iloadsi
A Single-Inductor Dual-Output Buck Converter with Self-Adapted PCCM Method
Yang Yang, Sun Liang, Wu Xiaobo
Abstract self-adapted A single-inductor dual-output (SmO) buck pseudo-continuous-conduction-mode buck converter and the timing diagram of it. The two outputs VOl and V02 share the inductor L and the switch
For dual-output converter with stable outputs, each output should be independently regulated. When load of one subconverter changes, the other output voltage will be affected, this is cross regulation. Due to the inductor current goes zero in each period in discontinuous conduction mode (DCM), the load variation in one output does not affect the other, thus the two outputs can be isolated in DCM, and cross regulation can be minimized. Furthermore, compensation is simple for DCM system because there is only one LHP pole in the gain transfer function of control-to-output. Unfortunately, DCM can only provide limited power to the load due to its zero de current. Ifheavy load current is required, the peak current will get high, and large current ripples will be introduced. These will cause large noises which will be coupled into the substrate of the chip. Hence, the freewheel switching technique and PCCM has been proposed to handle the large load current stress, and cross regulation will also be minimized. Considering different load current levels due to different loads and the change of loads, self-adapted de current levels of loads is proposed in the PCCM. Fig. 2 shows the features of the CCM, DCM, and Fig. 3 shows