A 900mA 93% efficient 50&amp;#x00B5;A quiescent current fixed frequency hysteretic buck converter using a highly digital hybrid voltage- and current-mode control

Khan, Qadeer; Elshazly, Amr; Rao, Sachin; Inti, Rajesh; Hanumolu, Pavan Kumar

doi:10.1109/vlsic.2012.6243850

Cited by 10 publications

(12 citation statements)

References 3 publications

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“…When a system operates under ultralight load conditions, hysteretic control and constant on-time control mechanisms can be automatically operated in a pulse frequency modulation (PFM) mode to reduce switching loss and improve light load efficiency. Among ripple-based control techniques, hysteretic control approaches [1]- [8] demonstrate the fastest dynamic response in both step-up and step-down load transients.…”

Section: Introductionmentioning

confidence: 99%

A Fixed-Frequency Quasi-<formula formulatype="inline"><tex Notation="TeX">${\rm V}^{2}$</tex></formula> Hysteretic Buck Converter With PLL-Based Two-Stage Adaptive Window Control

Lin

Tsai

2015

IEEE Trans. Circuits Syst. I

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This paper proposes a fast transient quasifixed-frequency hysteretic buck converter designed and fabricated using TSMC 2P4M 0.35-CMOS process. The proposed converter can achieve fixed frequency switching through a novel phase-locked-loop-based two-stage adaptive window control. Under ultralight load conditions, the proposed converter operates in a pulse frequency modulation mode to reduce the switching loss and improve light load efficiency. A quasi-technique is applied for obtaining inductor current information without relying on an output capacitor with a high equivalent series resistance; therefore, the output voltage ripple can be reduced. The experimental results show that the proposed converter can operate at a load current ranging from 18 to 700 mA, a supply voltage ranging from 2.7 to 4.2 V, and an output voltage of 1.2 V. The off-chip inductor and output capacitor are 2.2 and 10 , respectively. Through the PLL control, the switching frequency is maintained at 1 MHz. The transient response time is approximately 5 , and the highest efficiency registered is 95.6%. Index Terms-Adaptive window control, fast-transient, fixed-frequency, hysteretic control.1549-8328

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Section: Introductionmentioning

confidence: 99%

A Fixed-Frequency Quasi-<formula formulatype="inline"><tex Notation="TeX">${\rm V}^{2}$</tex></formula> Hysteretic Buck Converter With PLL-Based Two-Stage Adaptive Window Control

Lin

Tsai

2015

IEEE Trans. Circuits Syst. I

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“…This is considered a major drawback as it results in a variable and unpredictable switching noise, which not only can degrade the load performance significantly, but also the performance of other circuits that may share the input and ground rails with the converter [3]. This drawback has been traditionally circumvented by introducing various flavors of frequency control loops [3][4][5][6][7][8][9][10][11][12][13][14] such as the one shown in Fig. 1(c), which forces a constant switching frequency in order to produce a predictable well-defined switching noise spectrum.…”

Section: Introductionmentioning

confidence: 99%

Variable switching noise mitigation in hysteretic power converters using spur-free control

Nashed

Fayed

2015

2015 IEEE Applied Power Electronics Conference and Exposition (APEC)

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This paper introduces a control scheme for hysteretic power converters that results in a spur-free switching noise spectrum irrespective of the actual switching frequency of the converter. The proposed control scheme enables powering noisesensitive loads directly from hysteretic converters without requiring the rather complicated switching frequency control loops that have been traditionally employed within hysteretic power converters in order to maintain a constant and predictable switching frequency and switching noise spectrum. Therefore, the key advantages of hysteretic power converters, i.e. simple design, cost-effective implementation and fast transient response, can be preserved by eliminating any additional frequency control overhead. A step-down buck converter is used to demonstrate the proposed control scheme.

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“…Through those two procedures, f SW can be coincided with f CLK and then the FFC maintains f SW with a fixed R SEN2 as long as only one rising edge of f SW is in between the f CLK edges. This FFC control loop is separated from the voltage regulation loop so that the output voltage regulation is not affected by the FFC path [4]. As measured, the switching frequency is fixed within 0.2% of the reference frequency 1MHz along with I O from 0 to 700mA range at a typical voltage V IN =3.7V.…”

mentioning

confidence: 96%

“…Another issue with the hysteretic converter is its variable switching frequency, which leads to difficulty in designing an EMI filter [2]. To overcome these limitations, several state-of-the-art hysteretic converters have been reported that provide fast transient response and fixed switching frequency [2][3][4][5]. However, they suffer from noise due to the differentiator for amplifying ripple voltage [2], or need a large external or internal capacitor [3,4], or generate high switching loss in the converter [5].…”

mentioning

confidence: 99%

“…To overcome these limitations, several state-of-the-art hysteretic converters have been reported that provide fast transient response and fixed switching frequency [2][3][4][5]. However, they suffer from noise due to the differentiator for amplifying ripple voltage [2], or need a large external or internal capacitor [3,4], or generate high switching loss in the converter [5]. In this paper, we present an area-efficient quasi-current-mode hysteretic buck converter with fixed switching frequency.…”

mentioning

confidence: 99%

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12.1 A 0.518mm<sup>2</sup> quasi-current-mode hysteretic buck DC-DC converter with 3μs load transient response in 0.35μm BCDMOS

Lee

Bang

Yoon

et al. 2015

2015 IEEE International Solid-State Circuits Conference - (ISSCC) Digest of Technical Papers

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As more features have been added to mobile devices, it has become necessary to integrate more DC-DC converters into the power-management IC. Consequently, there is a growing need for an area-efficient and simple controller design for DC-DC converters. A simple hysteretic control without any additional component for compensation is a very attractive solution because it is not only cost-effective, but also immediately responds to load change. However, a conventional current-mode hysteretic controller with low-ESR output capacitor, shown in Fig. 12.1.1, has an inherent trade-off between transient response and RC network time constant for emulating inductor current [1]. For instance, at a switching frequency less than several MHz, which is widely used in industry, the RC network occupies a relatively large die area because the capacitance C SEN of the network can be up to 100pF at a switching frequency of 1MHz. Another issue with the hysteretic converter is its variable switching frequency, which leads to difficulty in designing an EMI filter [2]. To overcome these limitations, several state-of-the-art hysteretic converters have been reported that provide fast transient response and fixed switching frequency [2][3][4][5]. However, they suffer from noise due to the differentiator for amplifying ripple voltage [2], or need a large external or internal capacitor [3,4], or generate high switching loss in the converter [5]. In this paper, we present an area-efficient quasi-current-mode hysteretic buck converter with fixed switching frequency. By employing a quasi inductor current emulator (QICE) with reset operation, the controller only uses a total internal capacitance of 3pF and provides fast transient response.

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A 900mA 93% efficient 50µA quiescent current fixed frequency hysteretic buck converter using a highly digital hybrid voltage- and current-mode control

Cited by 10 publications

References 3 publications

A Fixed-Frequency Quasi-<formula formulatype="inline"><tex Notation="TeX">${\rm V}^{2}$</tex></formula> Hysteretic Buck Converter With PLL-Based Two-Stage Adaptive Window Control

A Fixed-Frequency Quasi-<formula formulatype="inline"><tex Notation="TeX">${\rm V}^{2}$</tex></formula> Hysteretic Buck Converter With PLL-Based Two-Stage Adaptive Window Control

Variable switching noise mitigation in hysteretic power converters using spur-free control

12.1 A 0.518mm<sup>2</sup> quasi-current-mode hysteretic buck DC-DC converter with 3μs load transient response in 0.35μm BCDMOS

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A 900mA 93% efficient 50&#x00B5;A quiescent current fixed frequency hysteretic buck converter using a highly digital hybrid voltage- and current-mode control

Cited by 10 publications

References 3 publications

A Fixed-Frequency Quasi-<formula formulatype="inline"><tex Notation="TeX">${\rm V}^{2}$</tex></formula> Hysteretic Buck Converter With PLL-Based Two-Stage Adaptive Window Control

A Fixed-Frequency Quasi-<formula formulatype="inline"><tex Notation="TeX">${\rm V}^{2}$</tex></formula> Hysteretic Buck Converter With PLL-Based Two-Stage Adaptive Window Control

Variable switching noise mitigation in hysteretic power converters using spur-free control

12.1 A 0.518mm<sup>2</sup> quasi-current-mode hysteretic buck DC-DC converter with 3&#x03BC;s load transient response in 0.35&#x03BC;m BCDMOS

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A 900mA 93% efficient 50µA quiescent current fixed frequency hysteretic buck converter using a highly digital hybrid voltage- and current-mode control

12.1 A 0.518mm<sup>2</sup> quasi-current-mode hysteretic buck DC-DC converter with 3μs load transient response in 0.35μm BCDMOS