A novel constant on-time current-mode control scheme to achieve adaptive voltage positioning for DC power converters

Chen, Yung-Jen; Cogălniceanu, Dan; Lin, Yu-Cheng; Chen, Ching-Jan; Wang, Chien-Hui

doi:10.1109/iecon.2012.6388690

Cited by 22 publications

(15 citation statements)

References 12 publications

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“…A low-pass filter, consisting of R LPF and C LPF network, is used to obtain the output voltage offset information to be included in the feedback to correct the offset in the output voltage V o . Equation (1) can be obtained [2]. It can be seen from (1), the R LL provides desirable load line effect for AVP application.…”

Section: Introductionmentioning

confidence: 96%

“…In reality, multiple pulses may occur. is no longer small compared to V droop signal and cannot be approximated as a constant [2]. In this paper, a time-domain approach is used.…”

Section: Introductionmentioning

confidence: 99%

“…In that case, both CMCOT and Ripple-Based COT (RBCOT) were discussed but without an OC circuit and only for continuousconduction mode (CCM) operation. In reference [2], an OCCMCOT configuration was considered, but for CCM only. It was originally thought that DCM operation is always stable but it is not so from experimental observation.…”

Section: Introductionmentioning

confidence: 99%

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The DCM stability issue of voltage regulators using a current-mode constant on-time controller control

Lin

Cogălniceanu

Chen

2013

2013 IEEE Energy Conversion Congress and Exposition

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In recent years, constant on-time (COT) controllers for voltage regulators have received much attention because of their characteristics of high conversion efficiency under light-load conditions. Among the varieties of COT controllers, the currentmode version in combination with a DC output voltage offset correction (OC) circuit is considered in this paper. In the past, discontinuous-conduction mode (DCM) operation has been considered trivial and there was no stability problem under such a condition. But it was observed, in practice, instability can occur under such a condition. And it is critically important to have a rigorous stability analysis because the converter is usually in DCM operation under light-load condition. Describing function approach was usually used to obtain the stability behavior of the converter in which the duty cycle modulator is ripple-based, but it is infeasible under DCM operation. In this paper, a different approach, a time-domain analysis, is used to establish the stability criterion. The criterion is verified and proven to be useful for minimizing the controller chip area of the RC filter in the OC circuit.

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Section: Introductionmentioning

confidence: 96%

“…In reality, multiple pulses may occur. is no longer small compared to V droop signal and cannot be approximated as a constant [2]. In this paper, a time-domain approach is used.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The DCM stability issue of voltage regulators using a current-mode constant on-time controller control

Lin

Cogălniceanu

Chen

2013

2013 IEEE Energy Conversion Congress and Exposition

Self Cite

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“…The popular PFM method being researched and used by industry in recent years is constant on-time control or constant off-time control [14], [8]. Both schemes allow the switching frequency to vary, while a one-shot timer block generates constant on or off pulses.…”

Section: Constant On-time Controlmentioning

confidence: 99%

A two-phase buck converter with optimum phase selection for low power applications

Yeago¹,

Hyun²,

Ha³

et al. 2015

2015 IEEE Energy Conversion Congress and Exposition (ECCE)

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Power consumption of smart cameras varies significantly between sleep mode and active mode, and a smart camera operates in sleep mode for 80 -90% of time for typical use. To prolong the battery life of smart cameras, it is essential to increase the power converter efficiency for light load, while being able to manage heavy load. The power stage of traditional buck converter is optimized for maximum load, at the cost of light-load efficiency. Wei proposed a multiphase buck converter incorporating the baby-buck concept and optimum number of phases (ONP) control. This thesis research investigated Wei's multiphase buck converter to improve the light-load efficiency for smart cameras as the target application.The proposed two-phase buck converter aims to provide power for microprocessors of smart cameras. The input voltage of the converter is 5 V DC, and the output voltage is 1.2 V DC with power dissipation range of 25 mA (30 mW) for light load and 833 mA (1 W) for heavy load. Three methods are considered to improve light-load efficiency: adopting baby-buck concept, adapting ONP control for low-power range, and implementing a pulse frequency modulation (PFM) control scheme with discontinuous conduction mode (DCM) to lower switching frequency. The first method is to adopt the baby-buck concept through power stage design of each phase to optimize efficiency for a specific load range. The baby-buck phase is optimized for light load and the heavyload phase is designed to handle the processors maximum power consumption. The second method performs phase selection from sensed load current information. Rather than have all phases active for heavy-load as in ONP control, optimum phase selection (OPS) control is introduced to adaptively select between phases based on load current. Due to low-power constraints, OPS is more efficient for the medium to heavy-load range. The transition between phases due to load iii change is also investigated. The third and final method implements PFM control with DCM to lower switching frequency and reduce switching and driving losses under light load. PFM is accomplished with a constant on-time (COT) valley current mode controller, which uses the inductor current information and output voltage to generate switching signals for both the top and bottom switches. The baby-buck phase enters DCM to lower switching frequency under very light load, while the heavy-load phase remains in continuous conduction mode (CCM) throughout its load range.The proposed two-phase buck converter is designed and prototyped using discrete components. Efficiency of the two-phase converter and a power loss breakdown for each block in the control scheme were measured. The efficiency ranges from 64% to 81% for light load ranging of 30 mW to 200 mW, and the efficiency ranges from 81% to 88% for heavy load ranging from 200 mW to 1 W. The majority loss is due to controllers, which are responsible for 37 % (8.6 mW) for light load of 60 mW and for 10.9 % (9 mW) for heavy load of 600 mW. The gate driver loss is consider...

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“…The schematic of buck-boost converter with AVP control technique is illustrated in Figure 3(a) [11,12]. By transforming the sensed inductor current This paper takes buck-boost converter for example to study the design and stability analysis with AVP control.…”

Section: Small Signal Model Of Buck-boost Convertermentioning

confidence: 99%

Design and Stability Analysis of Buck-Boost Converter Applied with Adaptive Voltage Positioning Technique

Deng¹,

Xie²,

Cheng³

2014

IJCA

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A novel constant on-time current-mode control scheme to achieve adaptive voltage positioning for DC power converters

Cited by 22 publications

References 12 publications

The DCM stability issue of voltage regulators using a current-mode constant on-time controller control

The DCM stability issue of voltage regulators using a current-mode constant on-time controller control

A two-phase buck converter with optimum phase selection for low power applications

Design and Stability Analysis of Buck-Boost Converter Applied with Adaptive Voltage Positioning Technique

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