Design and Implementation of a Voice-Coil Motor Servo Control IC for Auto-Focus Mobile Camera Applications

Jhih-Da Hsu, Ching-Lung Tsai, and Ying-Yu Tzou

Abstract

  This paper presents the design methodology to implement a fully digital control IC for the position control of the auto-focus (AF) lens module in applications to mobile phone camera using the field programmable gate array (FPGA). As compared with the conventional stepping motor control with a spring return fixture, the AF lens module is driven by a voice-coil motor (VCM) with a digital servo drive IC. The proposed digital servo drive IC includes a digital servo controller, a digital current controller, and a full-bridge dc-dc converter. The designed digital servo drive IC provides a total digital solution to the position control of the AF lens module in applications to high-performance light-weight slim-type mobile phone camera and video. The designed AF lens module can reach a control range of 0.6 mm within 30 ms with a control resolution less than 5 μm, a peak driving force of 30 mN, and a peak output current of 120 mA.


Digital Control of a Multi-Phase Interleaved PWM Inverter with Minimal Total Harmonic Distortion

Yu-Tzung Lin and Ying-Yu Tzou

Abstract

  This paper presents a digital repetitive control scheme for the minimization of output voltage total harmonic distortion (THD) of a PWM inverter under large unknown nonlinear load. The multi-phase interleaved PWM inverter has been adopted to enhance the effective switching frequency as well as to share the load current. The realization of a digital control for PWM inverter, such as sampling delay and quantization error, may introduce many nonlinear effects to distort its output waveforms. A systematic design procedure is developed to minimize selected range of harmonic spectrum by shaping the output impedance by so that its output voltage THD can be lower than a specified value with given design constraints. The proposed control scheme has been realized with fully digital design by using a single-chip FPGA implementation and verified by using co-simulation technique via a VHDL simulator Modelsim combined with a system-level block diagram oriented simulator Simulink.


Single-chip FPGA Implementation of a Sensorless Speed Control IC for Permanent Magnet Synchronous Motors

Yen-Chuan Chang and Ying-Yu Tzou

Abstract

  This paper presents a single-chip FPGA implementation of a speed sensorless control IC with flux-linkage estimation algorithm for permanent-magnet synchronous motors (PMSM) with sinusoidal flux distribution. By using hierarchical and modular realization strategy, each functional block for the digital sensorless IC is designed as a reusable IP with FPGA implementation. The digital sensorless IC is configurable with its modular blocks and is programmable with its control registers via a serial interface to fit various applications without complicated software programming as realized by using conventional DSP or microcontrollers. The sensorless algorithm implemented uses the incremental values of flux linkage, the normalized back-EMF voltage, and the estimated peak back-EMF value to estimate the incremental rotor position. An internal closed-loop correction mechanism within this algorithm can automatically correct the rotor position estimation drift, which could be resulted by the quantization error, circuit nonlinearities, and sampling noises. An initial rotor position detection scheme with ramping speed control has been developed for startup control. Experimental verification has been carried out on a sensorless spindle motor drive system for DVD applications.


Single-chip FPGA Implementation of a Sensorless Speed Control IC for Permanent Magnet Synchronous Motors

Yu-Tzung Lin, Yi-Chung Wang, and Ying-Yu Tzou

Abstract

  This paper presents the design and implementation of a singe-chip FPGA based digital VRM controller for multi-phase synchronous buck converters with interlaced current sampling and load current feed-forward compensation techniques. The sampling of the inductor current is synchronized with the middles of leading and trailing edges of the PWM signal of each synchronous buck converter for both turn-on and turn-off. The proposed sampling scheme has a high noise immunity to the common-mode switching noises induced by the switching of the MOSFET and its parasitic junction capacitances resulted by the heat sink. A true average current signal with minimum response time can be measured with accuracy within a switching period. The timing clocks for the digital controller and the digital PWM generator are interlaced with each other to achieve a minimum delay at a same sampling and switching frequency. A digital interface is designed for the connected microprocessor load to adjust the output voltage and provide feed-forward load current compensation according to its clock rate, loading factor, and pipeline scheduling. The realization scheme for the proposed digital VRM controller has been described. Simulation analysis and experimental verifications are given to illustrate the fast dynamic response control of VRM for advanced microprocessors.


Design of a Digital Servo Control IC for Permanent Magnet Synchronous Motors with Linear Hall Sensors

Yen-Chuan Chang and Ying-Yu Tzou

Abstract

  This paper presents the design and architecture implementation of a digital position control IC for permanent magnet synchronous motors (PMSMs) with sinusoidal flux distribution using linear Hall sensors for low-cost motion control applications. The absolute rotor position is calculated from the measured Hall sensor signals and a speed estimator is devised to generate speed feedback for the servo loop compensator. The developed digital servo control IC for PMSM motors with linear Hall sensors consists of three major control blocks: a servo loop controller, a position and speed estimator, and a field-oriented torque controller. The accuracy of positioning control resolution can be improved by a position error compensation table via external position calibration. All the control blocks are realized by using digital circuitry with configurable and reusable intellecture property (IP) blocks. Experiment results are presented to verify the performance and feasibility of the proposed IC.


Modeling and Design of a Voice-Coil Motor for Auto-Focusing Digital Cameras Using an Electromagnetic Simulation Software

Jhih-Da Hsu and Ying-Yu Tzou

Abstract

  This paper presents the modeling of a voice coil motor (VCM) used for the auto-focusing control of a digital camera in applications to high-performance mobile phones. The force constant and its associated back EMF constant of a VCM can be highly nonlinear with the mechanical structure. Conventional modeling technique using the derived flux distribution based on geometrical structure is quite involved and impractical to identify its equivalent parameters. A modeling procedure for a specially designed VCM is developed based on its mechanical structure and used material by using an electromagnetic simulation software - the Ansoft’s Maxwell 2D. An iterative optimal design process is then proposed to maximize the force constant of the VCM with a specified volume. Simulation results with experimental verification are given to illustrate that the proposed design procedure can achieve a satisfactory performance.


Load Current Adaptive Control of a Monolithic CMOS DC/DC Converter for Dynamic Power Management

Wei-Chi Su and Ying-Yu Tzou

Abstract

  This paper presents the design of a monolithic current-mode CMOS DC/DC converter with integrated power switches and an on-chip passive adaptive controller with the sensed average inductor current. The sensed switched current, combined with the integration of inductor voltage, and a voltage-controlled floating resistor, can be used for the adaptive control of a CMOS DC/DC converter. The nonlinear carrier control can adjust carrier according to input voltage to reduce the input disturbance. The proposed control scheme has been design and simulation verified based on the TSMC 0.35μm technology. The designed CMOS DC/DC switching regulator is based on a rated output current of 500mA with an adjustable output voltage from 1.0V to 1.8V. Simulation results shows the proposed adaptive control scheme can achieve a fast dynamic power on transient response as well as a robust voltage regulation against large loading current variation.


A New Sensorless Starting Method for Brushless DC Motors without Reversing Rotation

Yen-Chuan Chang and Ying-Yu Tzou

Abstract

  This paper presents a new sensorless starting method for brushless DC motors without reversing rotation for unidirectional applications. The method can detect the rotor position at standstill and a specific start-up method is then used to accelerate the motor up to a middle-speed where conventional sensorless control algorithms based on the back-EMF can work properly. The proposed scheme employs only one current sensor at DC-link side of the inverter, and can be applied to a motor without knowing its parameters and additional position sensors. As compared with previous approaches, the presented technique can simplify the sensorless position detection procedure and lower the cost. The proposed initial rotor position detection technique has a resolution of 30 electrical degrees, and does not cause any rotor vibration during the detection process. The sensorless starting scheme has been implemented on a single-chip DSP controller (TMS320LF2407A) and experimental results reveal that the starting procedure can work smoothly without temporarily reversing rotation.



台灣新竹交通大學電力電子晶片設計與DSP控制實驗室

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Last update: 2007/08/09
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