Abstract
Thee peak-current-mode (PCM) control strategy is widely adopted in pulse width-modulated (PWM) DC-DC converters. However, the converters always involve a sub-harmonic oscillating state or chaotic state if the active duty ratio is beyond a certain range. Hence, an extra slope signal in the inductor-current loop is used to stabilize the operation of the converter. This paper presents a new technique for enlarging the stable range of PCM-controlled DC-DC converters, in which the concept of utilizing unstable period-1 orbit (UPO-1) of DC-DC converters is proposed and an implementation scenario based on the parameter-perturbation method is presented. With the proposed technique, perturbations are introduced to the reference current of the control loop, and the converters operating in a chaotic state can be tracked, and thus be stabilized to the target UPO-1. Therefore, the stable operating range of the converters is extended. Based on an example of a PCM-controlled boost converter, simulations are presented as a guide to a detailed implementation process of the proposed technique, and comparisons between the proposed technique and techniques in terms of ramp compensation are provided to show the differentiation in the performance of the converter. Experimental results in the work confirm the effectiveness of the proposed technique.
Highlights
Pulse width-modulated (PWM) DC-DC converters are typical piecewise-smooth dynamical systems [1], and an external control loop is required for them to produce a precise and stable output voltage
A wide variety of nonlinear dynamic phenomena, such as bifurcations and chaos, have been observed in these converters [6,7,8,9,10,11,12,13], which could deteriorate the performances of the converters, and are undesired in practice
According to analysis works on PCM-controlled DC-DC converters with CCM operation, when the active duty ratio is beyond the range of (0, 1/2), the quality factor, Q, of the control-to-inductor transfer function is negative [24,25]
Summary
Pulse width-modulated (PWM) DC-DC converters are typical piecewise-smooth dynamical systems [1], and an external control loop is required for them to produce a precise and stable output voltage. According to analysis works on PCM-controlled DC-DC converters with CCM operation, when the active duty ratio is beyond the range of (0, 1/2), the quality factor, Q, of the control-to-inductor transfer function is negative [24,25]. It means that the eigenvalues of the converters distribute on the right half of the S plane, and the converters are in an unstable state. A new technique based on the parameter-perturbation method [30] is proposed, which can make PCM control work in a wider duty ratio range without using ramp compensation.
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