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Digital Noninverting Buck-Boost Converter With Enhanced
Duty Cycle-Overlap Control
Abstract:
The non-ideal effects of the comparator and dead time in a
synchronous controlled dc–dc converter adversely affect the
stability of a four-switch noninverting buck-boost converter. The
pulse-skipping phenomenon occurs in the mode-transition
region near the boundary between the step-down and step-up
regions, and this phenomenon leads to an unstable output
voltage and an unpredictable output voltage ripple. However,
these two results may damage the entire power system and
application system. This paper proposes an enhanced Duty
Cycle-Overlap control technique for a digitally controlled
noninverting buck-boost converter. The proposed technique
offers two duty cycles limitations for various conditions in the
mode-transition region and ensures the stability of the digital
controller and output voltage. Moreover, this technique involves
combining the duty cycles of both step-down and step-up modes
for deriving an accurate value of the output voltage. The
experimental results derived from a digital controller
implemented through a field-programmable gate array (FPGA)based platform revealed that the output voltage of the
noninverting buck-boost converter was stable throughout the
transition region. The observed input voltage of the converter,
provided by a Li-ion battery, was 2.5–4.5 V and the output
voltage was typically 3.3 V, which is suitable for
communication systems, audio systems, and I/O pad power
supplies. The switching frequency was 1 MHz and the
maximum load current was 500 mA.
Existing system:
 Portable electronic products have recently become an
integral part of modern life and the consumer market. A Libased battery is the commonly used power source in such
products.
 However, the energy capacity of such a battery is limited.
Therefore, high-efficiency power management systems
have become a major requirement for portable devices.
Proposed system:
 In this study, we created a digitally controlled NIBB
converter involving enhanced duty cycle-overlap control
for providing a smooth and stable mode transition.
 Problems faced in digitally controlled buck-boost
converters, such as low efficiency and low output reliability
induced by pulse skipping, are overcome by using the
proposed control topology.
Block diagram:
Circuit diagram:
Advantages:
A digitally controlled system for converters offers numerous
advantages such as a low number of passive components and
simple integration with system-on-a-chip (SOC) devices.
Reference:
[1] Laird, "Intelligent BTv4.0 Dual-Mode Module," BT900
datasheet. Available:
httphttp://www.lairdtech.com/brandworld/library/Hardware%20
Integrati on%20Guide%20-%20BT900%20Module.pdf
[2] Nokia. Mobile Internet Battery Life: Challenges/Solutions.
Available: http://forumnokia.emea.acrobat.com/p41167344/
[3] SD Association. SD Specifications Part E1 SDIO Simplified
Specification version 3.00. Available:
https://www.sdcard.org/downloads/pls/simplified_specs/partE1_
300. pdf
[4] Texas Instruments, "Analog Fornt End Wideabns MixedSignal Transceiver," AFE7222 datasheet. Available:
http://www.ti.com/lit/ds/symlink/afe7222.pdf