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This article presents an improved optimum damping current-mode buck converter with fast-transient response and small-transient voltage using new current sensing circuits. The improved optimum-damping circuit, consisting of the dynamic slope generator and the proposed rail-to-rail current sensor, can stabilize the converter during the output current change and can accelerate the transient response to achieve better figure of merit performance. The dynamic slope generator can compensate the slope to prevent subharmonic oscillation issue and lower undershoot/overshoot without an extra slope compensator. The proposed rail-to-rail current sensor increases the input voltage range, accurately captures the inductor current information, and accelerates the transient response as the load current changes, because it eliminates spikes without the need for a sample-and-hold circuit in a conventional current-sensing circuit. The contributions of the proposed converter are listed in the following: 1) we have proposed a new current-sensing circuit without voltage divider, which can be operated rail-to-rail and improve the dynamic response; 2) the new current-sensing circuit consisted of no switches and therefore, without switching noises; 3) the new current-sensing circuit without voltage divider has a smaller chip area and a smaller path delay; 4) the proposed current-sensing circuit needs no sample-and-hold circuits to reduce current spikes; 5) the transient response and transient voltage of the proposed converter are better than others' works; and 6) we have designed and implemented a new optimum-damping current-mode buck converter with better performances compared with previous publications.

This article presents a hysteretic-current-controlled buck converter with constant-frequency-controlled and active-current-sensing (ACS) techniques. This converter used phase–frequency-locked techniques to achieve constant switching frequency. Even if the input voltage or output load current changes, the switching frequency will be as stable as possible at 1 MHz. The proposed ACS circuit will not generate sparks, so the current feedback loop does not need a sample-and-hold circuit, and that will reduce the transient response time. The proposed buck converter has been fabricated with TSMC 0.35 μ m CMOS 2P4M technology; the total area of the chip is 1.5 mm × 1.5 mm. The measurement results of this buck converter show that the maximum power efficiency is 90% when the output voltage is 2.5 V and the load current is 300 mA. The output voltage range is 2.5–1 V, and the maximum load current is 600 mA. When the load current varies between 100 and 500 mA, the load transient response is 2.6 μ s/2.2 μ s and undershoot/overshoot is 20 mV/30 mV. The switching frequency of this buck converter is locked at 1 MHz and the voltage error is within 1%.

This paper proposes a new and improved fast-transient-response low-transient-voltage boost converter with pseudo-current hysteresis-controlled techniques (PCHC). The converter uses the rail-to-rail current-sensing circuit to provide a hysteresis-controlled signal, helping to speed up the transient response and improve the overall efficiency. The proposed boost converter has been fabricated with TSMC $0.18~\mu \text{m}$ CMOS 1P6M technology, and the chip area is $1.18\times 1.18$ mm2 (include PADs). The measured results show that the input voltage range is from 0.5 V to 1 V, the output voltage is set as 1.8 V, and the output load current range is from 10 mA to 100 mA. When the output load current changes from 10 mA to 100mA and 100 mA to 10 mA, the transient responses are both 2 $\mu \text{s}$ , and peak power efficiency is 88.5% at the output load current of 75 mA.