Optimum power-saving method for power MOSFET width of DC–DC converters

Chen, Ke-Horng; Chien, Chieh-Ching; Hsu, Ching-Hsun; Huang, Li-Ren

doi:10.1049/iet-cds:20050331

Cited by 31 publications

(21 citation statements)

References 6 publications

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“…1. The transfer efficiency in this paper is 97.5% at the rating output where output current is 100 mA and the transfer efficiency is higher than 90% in full load range (10 mA-250 mA), which is better than the reported results [8,9] . …”

Section: Dc-dc Converter's Start-up Process Is Shown Incontrasting

confidence: 71%

Design of a high efficiency boost DC-DC converter

Gao

Yao

et al. 2009

Trans. Tianjin Univ.

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Abstract：An accurate circuit of PWM/PFM mode converting and a circuit of auto-adaptively adjusting dimension of power transistor are described. The duty cycle of the signal when the control mode converts can be gained accurately by using ratios of currents and capacitances, and an optimal dimension of power transistor is derived with different loads. The converter is designed by 0.35 μm standard CMOS technology. Simulation results indicate that the converter starts work at 0.8 V input voltage. Combined with synchronized rectification, the transfer efficiency is higher than 90% with full load range, and achieves 97.5% at rating output. Keywords：control mode；power transistor；synchronized rectification；efficiency With the development of portable electronics, the high efficiency DC-DC converter is becoming a hot research subject [1][2][3] . The longevity of the battery is primarily determined by the power consumption and the transfer efficiency of the converter. Traditional pulse width modulation (PWM) DC-DC converter provides high stability and low output ripple with constant frequency, but the transfer efficiency reduces obviously with light load. Pulse frequency modulation (PFM) DC-DC converter provides high transfer efficiency with light load or even standby state with variable frequency, but the noise and electro magnetic interference (EMI) in converter is hard to filter [4,5] . An accurate circuit of PWM/PFM mode converting and a circuit of auto-adaptively adjusting dimension of power transistors are described in this paper. The converter works in PWM mode with heavy load while in PFM mode with light load, and this converter auto-adaptively adjusts the dimension of power transistor by estimating the load condition. Combined with synchronized rectification, the converter achieves high transfer efficiency during large load range.

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Section: Dc-dc Converter's Start-up Process Is Shown Incontrasting

confidence: 71%

Design of a high efficiency boost DC-DC converter

Gao

Yao

et al. 2009

Trans. Tianjin Univ.

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“…Figure 4 shows the converter's efficiency versus the effectively switched width W of the power MOSFETs at several switching frequencies f sw , when a light load consuming 20 mA of load current is supplied. The best suited value for b depends on the load current I load [8]. However, b is also a function of the switching frequency, since there is a trade-off between conduction losses and switching losses.…”

Section: Simulation Resultsmentioning

confidence: 99%

Light-load efficiency increase in high-frequency integrated DC–DC converters by parallel dynamic width controlling

Lorentz

Berberich

März

et al. 2009

Analog Integr Circ Sig Process

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A significant improvement of the light load conversion efficiency in integrated CMOS DC-DC converters using pulse-width modulation (PWM) at constant switching frequencies above 1 MHz can be obtained by implementing dynamic width controlling (DWC) of the power transistors. The parallel implementation of DWC uses equally sized power cells, each containing the power transistor and its gate driver stages. The power cells are connected together in a parallel arrangement to limit the propagation delays and to avoid the transmission gates used in serial implementations. Due to this, higher switching frequencies can be realized. Advanced simulations were performed with Cadence Spectre combined with Mathematica to investigate the conversion efficiency improvement potential offered by DWC. With DWC, an absolute increase of the light load conversion efficiency as high as 29% can be achieved for switching frequencies in the range 1-10 MHz. Further, a conversion efficiency higher than 80% can be provided over roughly two decades of load current for a DC-DC converter operating at a switching frequency of 10 MHz. Experimental results obtained from a synchronous buck converter designed in a 0.18 µm CMOS technology and switched at 2 MHz in continuous conduction mode (CCM) have demonstrated an improvement of the light-load conversion efficiency of about 25%

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“…To determine automatically which modulation provides the highest efficiency under the ongoing conditions, a sensor must monitor the current flowing through the power inductor L 1 . Another example is when DWC of the power MOSFETs is implemented [5,6], in which case a current sensor is needed for determining the best suited transistor width to be switched for achieving the highest power conversion efficiency. As a last example, for controlling the constant current charging phase of a lithium-ion battery, a current monitoring circuit is needed.…”

Section: Average Inductor Current Sensing Circuitmentioning

confidence: 99%

“…It can be used to detect the current range in DC-DC converters providing several modulation methods (e.g., PWM: pulse-width modulation, PFM: pulse-frequency modulation) to increase their light load power conversion efficiency [4]. It can be used to select the most suited transistor channel width when dynamic width controlling (DWC) of the power MOSFETs is used [5,6]. It can also be used to control the current during the constant current charging phase of a lithium-ion battery.…”

Section: Introductionmentioning

confidence: 99%

Lossless average inductor current sensor for CMOS integrated DC–DC converters operating at high frequencies

Lorentz

Berberich

März

et al. 2009

Analog Integr Circ Sig Process

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A novel average inductor current sensing circuit integrable in CMOS technologies is presented. It is designed for DC-DC converters using buck, boost, or buckboost topologies and operating in continuous conduction mode at high switching frequencies. The average inductor current value is used by the DC-DC controllers to increase the light load power conversion efficiency (e.g., selection of the modulation mode, selection of the dynamic width of the transistors). It can also be used to perform the constant current charging phase when charging lithium-ion batteries, or to simply detect overcurrent faults. The proposed average inductor current sensing method is based on the lossless sensing MOSFET principle widely used in monolithic CMOS integrated DC-DC converters for measuring the current flowing through the power switches. It consists of taking a sample of the current flowing through the power switches at a specific point in time during each energizing and de-energizing cycle of the inductor. By controlling precisely the point in time at which this sample is taken, the average inductor current value can be sensed directly. The circuit simulations were done with the Cadence Spectre simulator. The improvements compared to the basic sensing MOSFET principle are a lower power consumption because no high bandwidth amplifier is required, and less noise emission because the sensing MOSFET is no more switched. Additionally, the novel average inductor current sensing circuit overcomes the low bandwidth limitation previously associated with the sensing MOSFET principle, thus enabling it to be used in DC-DC converters operating at switching frequencies up to 10 MHz and above.

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Optimum power-saving method for power MOSFET width of DC–DC converters

Cited by 31 publications

References 6 publications

Design of a high efficiency boost DC-DC converter

Design of a high efficiency boost DC-DC converter

Light-load efficiency increase in high-frequency integrated DC–DC converters by parallel dynamic width controlling

Lossless average inductor current sensor for CMOS integrated DC–DC converters operating at high frequencies

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