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Hybrid Buck–Boost Feedforward and Reduced Average Inductor Current Techniques in Fast Line Transient and High-Efficiency Buck–Boost Converter

This paper presents a buck-boost converter with high efficiency and small output ripple to extend the battery life of portable devices. Besides, the hybrid buck-boost feedforward (HBBFF) technique is integrated in this converter to achieve fast line response. The new control topology minimizes the switching and conduction losses at the same time even when four switches are used. Therefore, over a wide input voltage range, the proposed buck-boost converter with minimum switching loss like the buck or boost converter can reduce the conduction loss through the use of the reduced average inductor current (RAIC) technique. Moreover, the HBBFF technique minimizes the voltage variation at the output of error amplifier. Consequently, a fast line transient response can be achieved with small dropout voltage at the output. Especially, the converter can offer good line and load regulations to ensure a regulated output voltage without being affected by the decreasing battery voltage. Experimental results show that the output voltage is regulated over a wide battery lifetime, and the output ripple is minimized during mode transition. The peak efficiency is 97% and the transient dropout voltage can be improved substantially.

Power-Tracking Embedded Buck–Boost Converter With Fast Dynamic Voltage Scaling for the SoC System

A power-tracking embedded buck-boost converter with a fast dynamic voltage scaling (F-DVS) function is proposed to power the system-on-a-chip (SoC) system. To meet the power request of the SoC for different operation functions, fast up/down-tracking is implemented to achieve the F-DVS function. Recycling energy is also derived to minimize power dissipation during the down-tracking period. In addition, the peak current control and valley current control methods are utilized in the buck and boost operations, respectively, to minimize the effect of switching noise in high switching operation for compact solution. Moreover, the self-tuning pulse skipping mechanism extends the effective duty cycle to achieve voltage regulation and improves efficiency when the input voltage is close to that of the output. Through F-DVS, the tracking speed from 3 to 2 V and vice versa are 15 and 20 μs, respectively, with a high switching frequency of 5 MHz.

Fast Transient DC-DC Converter with On-Chip Compensated Error Amplifier

A novel fast transient DC-DC converter with on-chip compensated error amplifier is presented in this paper. The error amplifier uses on-chip current-mode Miller capacitor to replace a large off-chip capacitor. Only three transistors and one voltage follower are used to implement this novel architecture. Not only on-chip compensated error amplifier is implemented without off-chip components and I/O pins, but also it can have fast transient response. Furthermore, we accurately decrease the transient response time without suffering from the oscillation issue. Experimental results demonstrate the stability and the fast transient response of the DC-DC converters.

On-Chip Compensated Error Amplifier for Fast Transient DC-DC Converters

A novel on-chip compensated error amplifier for fast transient response of DC-DC converters is presented in this paper. The error amplifier uses on-chip current-mode Miller capacitor to replace a large off-chip capacitor. We only use three transistors and one voltage follower to implement this novel on-chip compensated error amplifier for fast transient DC-DC converters. Owing to the current-mode implementation, we can redirect the equivalent current to charge or discharge the output capacitor of the error amplifier to improve the transient response time. Not only on-chip compensated error amplifier is implemented without off-chip components and I/O pins, but also it can have fast transient response. The analytic equations guarantee the compensated correctness of the proposed circuit. With the proposed error amplifier, the transient response of DC-DC converters is improved significantly. Simulation results demonstrate the stability and the fast transient response of the DC-DC converters

High efficiency and smooth transition buck-boost converter for extending battery life in portable devices

This paper presents a high-efficiency and smoothtransition buck-boost (BB) converter to extend the battery life of portable devices. Owing to the usage of four switches, the BB control topology needs to minimize the switching and conduction losses at the same time. Therefore, over a wide input voltage range, the proposed BB converter consumes minimum switching loss like the basic operation of buck or boost converter. Besides, the conduction loss is reduced by means of the reduction of the inductor current level. Especially, the proposed BB converter offers good line/load regulation and thus provides a smooth and stable output voltage when the battery voltage decreases. Simulation results show that the output voltage drops is very small during the whole battery life time and the output transition is very smooth during the mode transition by the proposed BB control scheme.

Dithering skip modulator with a novel load sensor for ultra-wide-load high-efficiency DC-DC converters

Dithering skip mode with a novel load sensor for DC-DC converters is proposed to maintain a high efficiency over a wide load range. Due to the efficiency drop of the transition from the pulse-width modulation (PWM) to pulse-frequency modulation (PFM), a novel dithering skip modulation (DSM) is introduced to smooth the efficiency curve. Importantly, DSM mode can dynamically skip the number of gate driving pulses, which is inverse proportional to load current. Besides, a novel proposed load sensor can automatically select the optimum modulation method from these three modulation methods without an external selection pin. Simulation results shows DSM can maintain the efficiency of converters as high as about 89% over a wide load current range from 3mA to 500mA

High efficiency buck-boost converter with reduced average inductor current (RAIC) technique

This paper presents a buck-boost converter with high-efficiency and smooth-transition to extend the battery life of portable devices. The new control topology minimizes the switching and conduction losses at the same time even four switches are used. Therefore, over a wide input voltage range, the proposed buck-boost converter with minimum switching loss like the buck or boost converter can reduce the conduction loss through the use of the reduced average inductor current (RAIC) level. Especially, the converter offers good line/load regulation and thus provides a smooth and stable output voltage without being affected by the decreasing battery voltage. Experimental results show that the output voltage is regulated for the whole battery life time and the output transition is very smooth during mode transition. Besides, the output voltage ripple and the average inductor current are effectively minimized by the proposed control scheme. The peak efficiency is 97% and output voltage ripple is reduced from 100mV to within 10mV.

Ditherng Skip Modulator with a Width Controller for Ultra-wide-load High-Efficiency DC-DC Converters

This paper proposes a temperature-independent load sensor to decide the optimum power MOSFET width for power saving of DC-DC converters. Besides, it also can decide the optimum modulation technique in tri-mode operation, which is composed of pulse-width modulation (PWM), pulse-frequency modulation (PFM), and a new proposed dithering skip modulation (DSM). An efficiency-improving DSM operation is introduced to raise the efficiency drop because of transition from PWM to PFM. Importantly, DSM mode can dynamically skip the number of gate driving pulses, which is inverse proportional to load current. Simplistically and qualitatively stated, the novel load sensor can automatically select the optimum modulation method and optimum power MOSFET width to achieve high efficiency over a wide load range. Experimental results show the tri-mode operation can have high efficiency about 89% over a wide load current range from 3mA to 500mA. Owing to the effective mitigation of the switching loss contributed by large power MOSFET, the novel width controller not only achieves high efficiency about 95% but also extends this high efficiency to a lower load current range about 0.1mA

Ratio buck-boost (RBB) converter with feed-forward technique for achieving fast line response

A ratio buck-boost (RBB) converter with feed-forward (FF) technique is proposed for regulating output voltage with fast line response. Owing to the ratio control technique, RBB converter can achieve high conversion efficiency due to only two turn-on switches within a switching period for all operation modes, which contains buck, boost, and buck-boost modes. Besides, feed-forward technique minimizes the voltage variations at the output of error amplifier. Thus, a fast line transient response can be achieved with small dropout voltage at the output. The proposed RBB converter with FF-technique is designed by TSMC 0.35 um 2P4M process. Simulation results demonstrate the correction and performance of RBB converter with FF-technique. The transient dropout voltage can be decreased from 80 mV to 3 mV.

Optimum Power-Saving Method for Power MOSFET Width of One-Cycle Control DC-DC Converters

An optimum power MOSFET width technique is proposed in this paper for enhancing the efficiency characteristics of switching DC-DC converters. By implementing a one-cycle buck DC-DC converter, we demonstrate that the dynamic power MOSFET width controlling technique has much improvement in power reduction when the load current is light or heavy. The maximum efficiency of the buck converter is about 92% with 3% efficiency improvement for the heavy load condition. Besides, the efficiency can be enormously improved about 16% for light load condition as a result of the power reduction from the large power MOSFET transistors. Meanwhile, we also propose a new error correction loop circuit (ECL) to get a better load regulation than that of the previous designs. Furthermore, as compared to the adaptive gate driver voltage technique, the optimum power MOSFET width can achieve a great improvement on power saving. It is a better power-saving technique than the low-voltage-swing MOSFET gate drive technique for switching DC-DC converters.