Universal Digital Controller for Boost CCM Power Factor Correction Stages Based on Current Rebuilding Concept

Victor M Lopez,Angel De Castro,Francisco J Azcondo,Regan Zane

doi:10.1109/tpel.2013.2280077

Victor M Lopez, Angel De Castro + Show 2 more

Open Access

https://doi.org/10.1109/tpel.2013.2280077

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Abstract

Continuous conduction mode power factor correction (PFC) without input current measurement is a step forward with respect to previously proposed PFC digital controllers. Inductor volt-second (vs L ) measurement in each switching period enables digital estimation of the input current; however, an accurate compensation of the small errors in the measured vs L is required for the estimation to match the actual current. Otherwise, they are accumulated every switching period over the half-line cycle, leading to an appreciable current distortion. A vs L estimation method is proposed, measuring the input (v g ) and output voltage (v o ). Discontinuous conduction mode (DCM) occurs near input line zero crossings and is detected by measuring the drain-to-source MOSFET voltage v ds . Parasitic elements cause a small difference between the estimated voltage across the inductor based on input and output voltage measurements and the actual one, which must be taken into account to estimate the input current in the proposed sensorless PFC digital controller. This paper analyzes the current estimation error caused by errors in the ON-time estimation, voltage measurements, and the parasitic elements. A new digital feedback control with high resolution is also proposed. It cancels the difference between DCM operation time of the real input current, (T DCM g ) and the estimated DCM time (T DCM reb ). Therefore, the current estimation is calibrated using digital signals during operation in DCM. A fast feedforward coarse time error compensation is carried out with the measured delay of the drive signal, and a fine compensation is achieved with a feedback loop that matches the estimated and real DCM time. The digital controller can be used in universal applications due to the ability of the DCM time feedback loop to autotune based on the operation conditions (power level, input voltage, output voltage...), which improves the operation range in comparison with previous solutions. Experimental results are shown for a 1-kW boost PFC converter over a wide power and voltage range.

Highlights

Some advantages that motivate the use of digital control in power factor correction (PFC) stages include: reduction of discrete components, reduction of size, reduction of sensitivity to parameter tolerances, ease of controller implementation and extension of its performance limits
HIGH RESOLUTION FEEDBACK LOOP Recent works [19]-[22] avoid the input current measurement and propose a PFC digital control that includes the measurement of the parasitic elements (RL, VD, RD, Ron) and applies a duty cycle command d, according to these elements, or neglects their influence
The output voltage reference is 400 Vdc with an input voltage ranging from 85 Vrms to 250 Vrms

Summary

INTRODUCTION

Some advantages that motivate the use of digital control in PFC stages include: reduction of discrete components, reduction of size, reduction of sensitivity to parameter tolerances, ease of controller implementation and extension of its performance limits. For PFC applications, several works have been presented to avoid sensors or ADC chips in the converter, simplifying the control circuit. Approaches such as [6], [7] eliminate the voltage sensor in the input or output voltage, [8] uses the diode current as a variable to compute the duty cycle, and [9] and [10] avoid the use of an ADC chip in the current acquisition, but a current sensor is used.

DIGITAL CURRENT ESTIMATION WITHOUT CURRENT SENSOR

DIGITAL CORRECTION OF THE CURRENT ESTIMATION ERRORS

Ls ireb vdig on-off

DISCONTINUOUS CONDUCTION AUXILIARY DETECTION CIRCUIT

HIGH RESOLUTION FEEDBACK LOOP

VIII. CONCLUSION