Search

Applying pulsewidth modulation (PWM) to control the gain in audio codecs for mobile applications leads to several advantages, such as the smooth control of tuning parameters, smaller silicon area, and lower power consumption, as compared with other tuning techniques using programmable gain amplifiers and zero crossing detectors. The PWM has to be embedded into the main signal path, preferably in a closed-loop control scheme, in order to exploit its benefits. However, the insertion of dithering and offset controls in a gain setting loop poses the problem of controlling their effects in all gain conditions. This paper reports a novel technique aimed at solving the associated issues and limitations, and provides the experimental proof of the concept through the implementation of a test-chip design on silicon. In particular, this paper reports the design and experimental results of a delta–sigma analog-to-digital converter featuring a click-free gain control technique, dithering insertion, and idle-tone shifting, which has been implemented in a 40-nm complementary metal–oxide–semiconductor technology for commercial telecom audio codec applications. [ABSTRACT FROM PUBLISHER]

Inductor current is an important feedback parameter in synchronous buck converters (SBCs). It is used for overcurrent protection, current sharing among interleaved modules, and current-mode feedback regulation, among others. While implementing a digital controller, inductor current is sensed and fed into the controller through a high sampling frequency analog to digital converter (ADC). As the switching frequency of the converter becomes higher, the need for an even higher sampling frequency ADC also goes up, which is a distinct disadvantage in terms of the overall cost. This paper discusses a simple current estimation technique that avoids use of any expensive current sensor and high sampling frequency ADCs. The paper shows that in a buck converter, inductor current can be estimated by tracking the width of the switch node voltage. Implementation and limitations of the proposed current estimation scheme are discussed in detail. The proposed method is validated using a 3.3 V–15 A SBC prototype and results show the estimation technique is accurate within 5% with a converter switching frequency of 800 kHz. In order to prove the effectiveness of the technique in feedback regulation, the current estimation technique is used to implement average current mode and hysteretic current mode control on a SBC. To prove the effectiveness of the proposed current estimation scheme, it is used in closed-loop control of the SBC to verify the dynamic responses, such as start-up transient, step change in load, and reference. [ABSTRACT FROM AUTHOR]

In this paper, a new method is applied to predict the average value of the phase currents of a two-level voltage source converter. The method uses a suitable model of the converter, the modulation method, and the measurement. The samples given by the analog-to-digital converter (ADC) are used to predict the time progress of the currents in every switching cycle and then calculate its average. This allows removal of the delay introduced by filtering and avoids aliasing in the measurements. The average prediction is contrasted with the pulsewidth modulation (PWM) synchronous sampling method and the sigma-delta ADC with a moving average filter. Applied to a load observer, the method effectively reduces its estimation error. The findings are verified experimentally. [ABSTRACT FROM AUTHOR]

Z-source inverter provides a competitive single-stage dc–ac power conversion with the capability of both buck and boost voltage regulation. In order to maximize voltage gain and to increase efficiency, this paper proposes an improved pulse-width modulation (PWM) strategy. By adjusting the shoot-through duty ratio of one-phase leg, it regulates the average value of intermediate dc-link voltage, which is the same as the instantaneous maximum of three-phase line voltage in one switching time period (Ts) . And the other two-phase legs maintain the fixed switching states. Thus, the equivalent switching frequency of power devices in the inverter bridge is reduced to 1/ 3fs (fs is the frequency corresponding to Ts). The operating principles and closed-loop controller design are analyzed and verified by simulation and experiments. Compared with the existing PWM strategies, the improved PWM (IPWM) strategy demonstrates higher efficiency under full operation range of low voltage gain (1.27-2) application. However, with the IPWM strategy, the inductor current and capacitor voltage contain six-time-line-frequency ripples, which consequently require large size of the passive components when the output frequency is very low. Thus, it is also suitable for 400–800-Hz medium frequency aircraft and vessel power supply system due to a relatively high output line frequency. Furthermore, the idea of IPWM strategy can be extended to other kinds of three-phase impedance network-based inverters. [ABSTRACT FROM PUBLISHER]

A generalized space-vector-based spread spectrum modulation scheme for multilevel inverters is proposed in this paper. The proposed scheme uses the principle of sigma–delta modulation as applied to analog-to-digital converters (ADCs), based on the view that a multilevel converter could be interpreted as an oversampling ADC. The principle of vector quantization is utilized for quantizing the instantaneous reference voltage space vector in the proposed space-vector-based sigma–delta converter. The switching vectors of the inverter are naturally selected without sector identification, ensuring optimum switching sequence under all conditions including the overmodulation region. As the sigma–delta converter results in a randomly varying switching frequency, the proposed scheme has spread spectrum characteristics. To avoid fractional arithmetic, a 60 ^\circ coordinate system is used to represent the space vector in this paper. The proposed scheme can be used for any general n-level inverter, and experimental results are presented for four-, five-, and six-level inverters, driving a 2-hp three-phase induction motor in an open-end winding configuration. The experimental results of the proposed scheme are compared with the space-vector pulsewidth modulation (PWM) scheme and random PWM scheme. [ABSTRACT FROM PUBLISHER]

A simple current sharing control technique for the switching power supply is presented herein, whose basic concept is that the control effort created from the voltage loop is finely tuned by the control effort created from the current sharing loop based on the proposed phase link so as not only to obtain the desired output voltage but also to make the load current distributed among phases as evenly as possible. Such a control method is not only without any current sharing bus as compared with the traditional current sharing methods, but also suitable for multiple phases under the condition that any one phase among multiple phases fails. Moreover, based on phase link, there is no divider used, as compared with the traditional average current method, and hence, the number of logic elements in the field-programmable gate array (FPGA) can be reduced. In this paper, the detailed basic operating principles, together with new mathematical deductions based on the superposition concept, are firstly described, and secondly some experimental results, based on the FPGA to realize the fully digitalized control of the overall system using one-comparator counter-based sampling without any analog-to-digital converter (ADC), are provided to verify the effectiveness of proposed control strategy. [ABSTRACT FROM PUBLISHER]

In this paper, a three-level three-leg ac–dc–ac converter for single-phase applications is investigated. The operating principles and control strategies for the topology are presented. It is shown that dc-link voltage balancing and its reduction are important objectives in the system design. The proposed pulsewidth modulation (PWM) strategy permits the dc-link capacitor voltage balance and also its reduction. The three-level converter is compared to the two-level converter in terms of rms switch currents, harmonic distortion, losses, and costs. Experimental and simulation results are presented to validate the theoretical studies. [ABSTRACT FROM PUBLISHER]

A method is developed to predict, at every sampling instant, the average value of the system variables in a power converter. To achieve this, a model of the converter is used, incorporating the modulation method and the type of analog-to-digital converter, either a conventional sample-and-hold or a sigma–delta converter. The measurement given by the analog-to-digital converter is used to predict the time progress of the system variables during the present switching period and then to evaluate its average value, even before the period is completed. The method allows us to obtain simultaneously the average value for currents and voltages, to get rid of the delay introduced by filtering, and to avoid aliasing in the measurement. An example is given based on the buck converter. It is also shown experimentally how different types of measuring methods influence the performance of the closed-loop control. [ABSTRACT FROM PUBLISHER]