Comparison of Small Signal Characteristics in Current Mode Control Schemes for Point-of-Load Buck Converter Applications

Yan, Yingyi; Lee, F. C.; Mattavelli, Paolo

doi:10.1109/tpel.2012.2224673

Cited by 86 publications

(30 citation statements)

References 18 publications

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“…In the PSFB converter, flux bias in the transformer is generated because of the differences between the devices [24]. This problem affects the proper operation of the converter.…”

Section: The Proposed Closed Loop Control Systemmentioning

confidence: 99%

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High Efficiency Variable-Frequency Full-Bridge Converter with a Load Adaptive Control Method Based on the Loss Model

Zhao

Liu

et al. 2015

Energies

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Abstract:In this paper, a load adaptive control method to improve the efficiency and dynamic performance of the Phase-Shifted Full-Bridge (PSFB) converter which works under a wide range of load conditions is presented. The proposed control method can be used as a battery charger since this application demands a wide range of load conditions. The composition of the PSFB converter's losses and the loss analysis model are both discussed. According to this model, the optimum switching frequency which results in minimum power loss is adopted to improve the efficiency. The relationship between switching frequency and power loss is formulated over a wide load range. Indicated by this kind of relationship, the proposed controller adjusts the switching frequency at different load currents. Moreover, an adaptive gain adjustment controller is applied to replace the traditional controller, with the aim to improve the dynamic performance which is influenced by the changes of the switching frequency and load current. In addition, the experimental results show that the maximum improvement of efficiency is up to 20%. These results confirm the effectiveness of the proposed load adaptive control method.

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“…In the PSFB converter, flux bias in the transformer is generated because of the differences between the devices [24]. This problem affects the proper operation of the converter.…”

Section: The Proposed Closed Loop Control Systemmentioning

confidence: 99%

“…Peak current mode control (PCMC) is an effective way to solve this problem. This approach can balance the transformer flux in an isolated converter, improve the dynamic response and simplify the controller design [24][25][26]. PCMC has been widely adopted in switch mode power supplies.…”

Section: The Proposed Closed Loop Control Systemmentioning

confidence: 99%

High Efficiency Variable-Frequency Full-Bridge Converter with a Load Adaptive Control Method Based on the Loss Model

Zhao

Liu

et al. 2015

Energies

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“…This is because, for these modulations, the addi- . This is in contrast with [20], where a comparison of the small-signal characteristics of several modulations is carried out. In [20], a conclusion is that constant on-time can be preferable in applications with small duty cycles because a higher bandwidth can be achieved.…”

Section: )mentioning

confidence: 99%

Improved transient response of controllers by synchronizing the modulator with the load step: application to v2ic

Cortés

Šviković

Alou

et al. 2015

IEEE Trans. Power Electron.

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Abstract-V2 I C is a ripple-based control with an excellent performance for load transients and reference voltage tracking because it exhibits a feedforward of the load current and the error of the output voltage. However, if V 2 I C is modulated with constant frequency, constant on-time or constant off-time, its dynamic response is hindered by delays in the response. This paper proposes a technique that synchronizes the clock of the converter to initialize the duty cycle when a worst-case load transient occurs using the current through the output capacitor to detect load transients. It is exemplified on a V 2 I c control but it is applicable to most of controllers as it only acts on the modulator.Index Terms-Clock synchronization, dynamic voltage scaling, load transient, point of load, V 2 I C .

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“…Therefore, COT control double poles have little impact at half the switching frequency. The bandwidth of the control loop was designed to not exceed one-third the switching frequency following that presented by Yan [11]. This allows a proper gain and phase margin for the controller, which makes it stable.…”

Section: Specification Of the Proposed Convertermentioning

confidence: 99%

Constant ON-time 3-level buck converter for low power applications

Cassidy

2015

2015 IEEE Energy Conversion Congress and Exposition (ECCE)

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Smart cameras operate mostly in sleep mode, which is light load for power supplies.Typical buck converter applications have low efficiency under the light load condition, primarily from their power stage and control being optimized for heavy load. The battery life of a smart camera can be extended through improvement of the light load efficiency of the buck converter.This thesis research investigated the first stage converter of a car black box to provide power to a microprocessor, camera, and several other peripherals. The input voltage of the converter is 12 V, and the output voltage is 5 V with the load range being 20 mA (100 mW) to 1000 mA (5000 mW). The primary design objective of the converter is to improve light load efficiency.A valley current mode controlled 3-level buck converter proposed by Reusch was adopted for the converter in this thesis. A 3-level buck converter has two more MOSFETs and one more capacitor than a synchronous buck converter. Q1 and Q2 are considered the top MOSFETs, while Q3 and Q4 are the synchronous ones. The extra capacitor is used as a second power source to supply the load, which is connected between the source of Q1 and the drain of Q2 and the source of Q3 and the drain of Q4. The methods considered to improve light load efficiency are: PFM (pulse frequency modulation) control scheme with DCM (discontinuous conduction mode) and use of Schottky diodes in lieu of the synchronous MOSFETs, Q3 and Q4.The 3-level buck converter operates in CCM for heavy load above 330 mA and DCM for light load below 330 mA. The first method uses a COT (constant on-time) valley current mode controller that has a built in inductor current zero-crossing detector. COT is used to implement PFM, while the zero-crossing detector allows for DCM. The increase in efficiency comes from reducing the switching frequency as the load decreases by minimizing switching and gate driving loss. The second method uses an external current sense amplifier and a comparator to detect when to shut down the gate drivers for Q3 and Q4. Schottky diodes in parallel with Q3 and Q4 iii carry the load current when the MOSFETs are off. This increases the efficiency through a reduction in switching loss, gate driving loss, and gate driver power consumption.The proposed converter is prototyped using discrete components. LTC3833 is used as the COT valley current mode controller, which is the center of the control scheme. The efficiency of the 3-level buck converter was measured and ranges from 82% to 95% at 100 mW and 5000 mW, respectively. The transient response of the converter shows no overshoot due to a 500 mA load step up or down, and the output voltage ripple is 30 mV. The majority of the loss comes from the external components, which include a D FF (D flip-flop), AND gate, OR gate, current sense chip, comparator, and four gate drivers. The proposed converter was compared to two offthe-shelf synchronous buck converters. The proposed converter has good efficiency and performance when compared to the other converters, desp...

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Comparison of Small Signal Characteristics in Current Mode Control Schemes for Point-of-Load Buck Converter Applications

Cited by 86 publications

References 18 publications

High Efficiency Variable-Frequency Full-Bridge Converter with a Load Adaptive Control Method Based on the Loss Model

High Efficiency Variable-Frequency Full-Bridge Converter with a Load Adaptive Control Method Based on the Loss Model

Improved transient response of controllers by synchronizing the modulator with the load step: application to v2ic

Constant ON-time 3-level buck converter for low power applications

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