DC-DC power converter with a modified control scheme to improve load transient response

Abstract

A modified control scheme is presented in this paper to improve the load transient response of DC-DC power converter by utilizing a previously proposed auxiliary circuit which is capable of operating in both boost mode to discharge the output capacitor during load step down transient, and in buck mode to charge the output capacitor during load step up transient. The proposed modified control scheme for the auxiliary circuit is based on the output voltage peak detection, preset thresholds and zero crossing time information. This scheme achieves significant improvement in load transient response while eliminating the controller performance sensitivity to component values tolerances and complex calculations that could result in undesired transient response. A simulation model is built in MATLAB®/SIMULINK® software package to validate the functionalities and advantages of the proposed control scheme.

Output Impedance Correction Circuit (OICC): A New Concept to Improve the Dynamic Response of DC/DC Converters with Additional Energy Path

“…The AEP should inject a current at the output in a controlled manner, thus reducing the risk of high and potentially damaging currents and increasing robustness on the input voltage deviation as implemented in solutions [33]- [35], [39]- [40], [44], [50]- [56]. This issue is mainly related to the systems where AEP is implemented as auxiliary converter.…”

“…To ensure the current sharing, usually a Current Mode Control (CMC) is employed. The SoA solutions that are implemented with VMC [33]- [43], [45]- [47], [49]- [56], [60], [61] are limited to a single stage implementation, while solutions which are not interacting with main converter [44], [62] or which are employing CMC of the main converter stage [48], [57]- [59] can be easily extended to multiphase converter systems.…”

“…1. The Constant Current Injection (CCI): in this approach, the AEP injects a constant current at the output with the mean value equal to half of the load-step amplitude [46], [47], [50]- [56] and 2. The capacitor current mimicking: in this approach, the AEP inject a current in a open loop which imitates the capacitor current of the system without the AEP [48], [49], [57]- [61].…”

“…Nonetheless, the proposed approach has been further developed in [53] and [54] where the concept has been extended to AVP operation and the whole control has been implemented in a digital controller. Moreover, in order to reduce the switching frequency of the AEP boost converter and related losses, in [55] and [56], it is proposed that the AEP converter operates in a boundary CCM/DCM condition where the peak value is equal to the load-step amplitude. Doing so, the mean value of the auxiliary current is again equal to half of the load-step, while the converter switching losses are reduced since the switching frequency is reduced and the high-side switch is not turned-on with a full input voltage (the switching node starts to oscillate).…”

“…2) The AEP should be activated nearly instantaneously to prevent bigger output voltage deviation. To achieve near instantaneous activation, the converter system can be informed by the load prior to the load-step [46], [47], [60]- [62] or the system can observe the output capacitor current, which is the first system state variable that reacts on the load current perturbation [38], [50]- [56]. In this manner, the AEP is turned on with near zero output voltage error, providing smaller output voltage deviation.…”