Key Laboratory of High Speed Circuit Design and EMC

Xi’an, China

Key Laboratory of High Speed Circuit Design and EMC

Xi’an, China

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Yuan B.,Xidian University | Yuan B.,Key Laboratory of High Speed Circuit Design and EMC | Lai X.,Xidian University | Lai X.,Key Laboratory of High Speed Circuit Design and EMC | And 6 more authors.
2016 International Symposium on Integrated Circuits, ISIC 2016 | Year: 2016

A switch size control circuit for voltage-mode DC-DC buck converter is presented. By detecting the average load current, the circuit not only achieves hybrid mode of PWM and PFM operation, but also changes the power switch size according to the load conditions. Both the high-side and low-side switch currents are fully sensed by detecting the filtered smooth voltage of the switch node. The generated digital signal maintains a substantially constant mode and switch size changing point. A monolithic DC-DC buck converter using the proposed circuit has been fabricated with a 0.5μm CMOS process for validation. The switch size is 1/3 of the maximum value in PFM operation and changes to full size in PWM operation. High efficiency over a wide load current from 0.001 to 5A is achieved. The measurement result shows that the switch size control circuit has good performance and agrees well with the theoretical analysis. © 2016 IEEE.


Yuan B.,Xidian University | Yuan B.,Key Laboratory of High Speed Circuit Design and EMC | Lai X.-Q.,Xidian University | Lai X.-Q.,Key Laboratory of High Speed Circuit Design and EMC | And 3 more authors.
IEEE Transactions on Microwave Theory and Techniques | Year: 2013

Considering the tradeoff between efficiency and output ripple over a wide load range, a monolithic dc-dc buck converter with switch-on-demand modulation (SODM) and switch size control (SSC) is presented in this paper. SODM achieves a hybrid mode of pulse skip and pulse width modulation (PWM) without mode detection circuit. The converter's on time is adaptively adjusted with the load demand, achieving low output voltage ripple. Detecting the output of the error amplifier by a comparator, the SSC circuit can select appropriate switch size according to load current for reducing switching loss in a light load. The threshold level of the comparator varies with respect to the amount of slope compensation, which maintains a substantially constant switch size changing point. Experimental results show that the fabricated converter with the proposed scheme achieves high efficiency from 83% to 96% over a wide load range from 10 mA to 5 A. The switch size is 1/4 of the maximum value when load current is below 1 A with 0.5-A hysteresis. Also, the measured maximum output ripple is less than 10 mV. © 1963-2012 IEEE.


Zhang Y.-L.,Xidian University | Zhang Y.-L.,Henan Polytechnic University | Lou S.-T.,Xidian University | Lou S.-T.,Key Laboratory of High Speed Circuit Design and EMC | Zhang W.-T.,Xidian University
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2011

The underdetermined mixture matrix in blind source separation can be obtained by canonical decomposition of the three-order tensor. In order to overcome the flaw of high computational complexity and long running time of existing canonical decomposition algorithm, the tensor is compressed as lower order core one using tucker decomposition. The factor of tucker decomposition can be obtained by left singular value of the original tensor's mode-3 matrix. The mixture matrix can be estimated by the alternating least square based canonical decomposition of the core tensor. Simulation results show that the proposed algorithm has much lower computational complexity with no performance loss and its operation time reduces 46.44%~76.28% compared with the existing algorithm.


Yuan B.,Xidian University | Yuan B.,Key Laboratory of High Speed Circuit Design and EMC | Lai X.,Xidian University | Lai X.,Key Laboratory of High Speed Circuit Design and EMC | And 5 more authors.
2013 IEEE International Conference of Electron Devices and Solid-State Circuits, EDSSC 2013 | Year: 2013

A soft-start circuit with soft-recovery function for DC-DC converters is presented in this paper. The soft-start strategy is based on a linearly ramped-up reference and an error amplifier with minimum selector implemented with a three-limb differential pair skillfully. The soft-recovery strategy is based on a compact clamp circuit. The ramp voltage would be clamped once the feedback voltage is detected lower than a threshold, which could control the output to be recovered slowly and linearly. A monolithic DC-DC buck converter with proposed circuit has been fabricated with a 0.5μm CMOS process for validation. The measurement result shows that the ramp-based soft-start and soft-recovery circuit have good performance and agree well with the theoretical analysis. © 2013 IEEE.


Shi L.-F.,Xidian University | Shi L.-F.,Key Laboratory of High Speed Circuit Design and EMC | Zhang F.,Xidian University | Zhang F.,Key Laboratory of High Speed Circuit Design and EMC | And 4 more authors.
Analog Integrated Circuits and Signal Processing | Year: 2015

This paper presents a temperature-compensated CMOS current reference with low line regulation current mirror. The circuit is based on a bandgap reference voltage that achieves the temperature compensation of resistor by the negative temperature coefficient (TC) of a high-resistance polysilicon (HR poly) resistor with the positive TC of an n-well resistor. The low line regulation current mirror is implemented by using a negative feedback connected operational amplifier. Prototypes of 1 μA current reference from 0.35 μm CMOS process show a maximum temperature coefficient of 139 ppm/°C for a temperature range of 0–80 °C. The line regulation is reduced to 0.5 %/V for supply voltage of 3.5 to 5.5 V. © 2015 Springer Science+Business Media New York


Liu C.,Xidian University | Liu C.,Key Laboratory of High Speed Circuit Design and EMC | Lai X.-Q.,Xidian University | Lai X.-Q.,Key Laboratory of High Speed Circuit Design and EMC | And 2 more authors.
IEICE Electronics Express | Year: 2015

An AC-mains voltage compensation technology for variable load multiple-string LED drivers is presented. By forming a closed loop control of the multiple reference voltages and by introducing an external compensation resistor, the output luminance is well compensated in case of line voltage variations. The proposed technology along with the accompanied AC-direct multiple-string LED driver were integrated in an 1 μm trenchisolated BCD process and tested with a three-string prototype. With very few external components used, the line regulation character of the LED driver is highly optimized by the proposed technology. The experimental results show that within 15% AC-mains voltage tolerance, the output luminance deviation is restrained to 2.0% (1.5%) under 10W, 110V/AC (220V/AC), 50 Hz conditions. © IEICE 2015.


Zhang Y.,Xidian University | Zhang Y.,University of Science and Technology of China | Lou S.,Xidian University | Lou S.,Key Laboratory of High Speed Circuit Design and EMC | And 2 more authors.
Shuju Caiji Yu Chuli/Journal of Data Acquisition and Processing | Year: 2011

The accuracy of estimated score function is an important factor that influences the convergent speed and stability of the natural-gradient-based blind source separation (BSS) algorithm. A new estimating score function approach based on the method of function approximation is proposed. In this approach, score function is approximated by the linear combination of a set of orthogonal polynomials. The accuracy of approximation is measured by mean square error(MSE).Using the property of score function, coefficients of the linear combination can be obtained by adaptively minimizing MSE. The new BSS algorithm is developed by substituting the estimated score function into natural gradient iterative formula. Experimental results show that, compared with the traditional one, the stability and convergent speed of the new algorithm is improved.

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