Fast-transient techniques for high-frequency DC–DC converters

A 30 MHz voltage-mode controlled buck converter with fast transient responses is presented.An improved differential difference amplifier(DDA)-based Type-III compensator is proposed to reduce the settling times of the converter during load transients,and to achieve near-optimal transient responses with simple PWM control only.Moreover,a hybrid scheme using a digital linear regulator with automatic transient detection and seamless loop transition is proposed to further improve the transient responses.By monitoring the output voltage of the compensator instead of the output voltage of the converter,the proposed hybrid scheme can reduce undershoot and overshoot effectively with good noise immunity and without interrupting the PWM loop.The converter was fabricated in a 0.13μm standard CMOS process using 3.3 V devices.With an input voltage of 3.3 V,the measured peak efficiencies at the output voltages of 2.4,1.8,and 1.2 V are 90.7%,88%,and 83.6%,respectively.With a load step of 1.25 A and rise and fall times of 2 ns,the measured 1%settling times were 220 and 230 ns,with undershoot and overshoot with PWM control of 72 and 76 mV,respectively.They were further reduced to 36 and 38 mV by using the proposed hybrid scheme,and 1%settling times were also reduced to 125 ns.

Design of Readout Circuit Based on Probe Neural Biosensor

According to the characteristics of neural signal,a low-voltage and high-speed operational transconductance amplifier has been realized as a direct readout circuit. To reduce the size and cost of this chip, the amplifier uses feedforward compensation technique without Miller capacitor. Using capacitors as a closed-loop feedback not only amplifies the neural signal, but also reduces chip power consumption by replacing the feedback resistor. Simulations were carried out with 0.18m CMOS technology, and the simulation results satisfied the requirements of neural signal.

A learning-based flexible autonomous motion control method for UAV in dynamic unknown environments

This paper presents a deep reinforcement learning(DRL)-based motion control method to provide unmanned aerial vehicles(UAVs)with additional flexibility while flying across dynamic unknown environments autonomously.This method is applicable in both military and civilian fields such as penetration and rescue.The autonomous motion control problem is addressed through motion planning,action interpretation,trajectory tracking,and vehicle movement within the DRL framework.Novel DRL algorithms are presented by combining two difference-amplifying approaches with traditional DRL methods and are used for solving the motion planning problem.An improved Lyapunov guidance vector field(LGVF)method is used to handle the trajectory-tracking problem and provide guidance control commands for the UAV.In contrast to conventional motion-control approaches,the proposed methods directly map the sensorbased detections and measurements into control signals for the inner loop of the UAV,i.e.,an end-to-end control.The training experiment results show that the novel DRL algorithms provide more than a 20%performance improvement over the state-ofthe-art DRL algorithms.The testing experiment results demonstrate that the controller based on the novel DRL and LGVF,which is only trained once in a static environment,enables the UAV to fly autonomously in various dynamic unknown environments.Thus,the proposed technique provides strong flexibility for the controller.

Comparison of high-energy multi-pass Ti:sapphire amplifiers with a different Ti-dopant concentration

We experimentally compare the output abilities of lightly and heavily doped Ti：Sapphire（Ti：S） amplifiers with diameters as large as 150 mm. Although a lightly doped Ti：S is more favorable to overcome parasitic lasing（PL）and transverse amplified spontaneous emission（TASE）, the self-phase-modulation（SPM） effect becomes more pronounced when a longer crystal is used. Recompression of the amplified, stretched pulses can be seriously affected by the SPM effect. We then propose a temporal multi-pulse pump scheme to suppress PL and TASE in a thin, heavily doped Ti：S crystal. This novel temporal multi-pulse pump technique can find potential applications in 10 PW chirped-pulse amplification laser systems.