Abstract
This paper presents a new technique that adjusts the hysteresis window depending on the variations in load current caused by a voltage-mode circuit to reduce the voltage and current ripples. Moreover, a compact current-sensing circuit is used to provide an accurate sensing signal for achieving fast hysteresis window adjustment. In addition, a zero-current detection circuit is also proposed to eliminate the reverse current at light loads. As a result, this technique reduces the voltage ripple below 8.08 mVpp and the current ripple below 93.98 mApp for a load current of 500 mA. Circuit simulation is performed using 0.18 μm CMOS process parameters.
Highlights
DC-DC buck converters are widely used in portable devices like cellular phones, laptop computers, and digital cameras etc
These circuits are composed of a current-sensing circuit, a continuous conduction mode (CCM) and discontinuous conduction mode (DCM) selection circuit, a CCM load-dependent hysteresis circuit, a DCM switching frequency control circuit, and an analog switch circuit
It automatically operates in the DCM or CCM according to the variation in the load current through the proposed zero-current detection (ZCD) circuit without their selection circuit
Summary
DC-DC buck converters are widely used in portable devices like cellular phones, laptop computers, and digital cameras etc. To obtain the effective power conversion, these converters must satisfy several key specifications, such as wide load current range, low voltage and current ripples, fast transient response, high power efficiency, stable operation, and simplicity. For such conversion, hysteresis DC-DC buck converters have been studied as a core technology [1,2,3,4,5,6,7,8]. To improve the power efficiency, a hysteresis DC-DC buck converter was proposed [9] This converter is based on an adaptive window control circuit to reduce the voltage and current ripples.
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