1 v 1 concept: designing a voltage mode control as current mode with near time-optimal response for Buck-type converters Jorge Cort´ es, Student Member IEEE, Vladimir ˇ Svikovi´ c, Student Member IEEE, Pedro Alou, Member IEEE, Jes´ us A. Oliver, Member IEEE and Jos´ e A. Cobos, Senior Member IEEE Centro de Electr´ onica industrial Universidad Polit´ ecnica de Madrid Madrid, Spain jorge.cortes@upm.es, vladimir.svikovic@upm.es, pedro.alou@upm.es, jesusangel.oliver@upm.es, ja.cobos@upm.es Abstract—This article introduces the v 1 concept, that explains how by only measuring the output voltage, designers have infor- mation about almost every signal of the power stage. Following the v 1 concept, it is explained how to design a traditional type-III voltage mode control to behave like a current mode control with near time-optimal response under load transients. The work is validated in simulations and experimentally on a 300kHz Buck converter. Index Terms—v1, v2, v2ic, voltage mode, current mode, capacitor current, optimal, buck, POL I. I NTRODUCTION Applications with highly demanding load steps and dynamic voltage scaling (DVS) such as Point-of-Load converters and Voltage Regulator Modules (VRMs) need very fast controls in order to comply with the dynamic requirement and still maintain an output capacitor as small as possible. Ripple-based controls are one popular solution to achieve a fast dynamic response. They are composed by a fast feedback (FFB) path and a slow feedback (SFB) path. The fast feedback path is a rippled signal with information about the power stage and it is responsible of the modulation of the duty cycle and the dynamic behavior of the control. The slow feedback path is an integrator designed to have a very low bandwidth and it is responsible to regulate the output voltage in steady state. The v 2 control [1, 2] only uses the output voltage, but it behaves properly only with high ESR output capacitors [3]. In [4, 5], the inductor current is added to the v 2 control to stabilize it. On the other hand, [6], proposed in 2011, instead, to add the capacitor current information using only the output voltage, which allows the control to behave almost optimally under load transients [7, 8]. This control is named v 2 i c (or This work has been partially supported by Spanish Government Innovation and Science Office (MCINN), under research grant no. DPI- 2010-20096, “FAST” project. This work has been partially supported by EU FP7-ICT-2011-8 – Power- SWIPE – Project no.: 318529 “current-mode control of the output capacitor current” in a previous version from 2010 [9]). Using the capacitor current to improve the dynamic response is not a new concept since it dates back at least to 1986 [10], but [6] improves the idea by using a simple lossless sensor of the capacitor that only measures the output voltage and that takes into account the ESL of the output capacitor. In 2013, [11] proposed the same concept with a different implementation of the sensor of the current. Later in 2014, Google TM filed a patent including the same concept as in [9] but with a different sensor of the capacitor current [12]. Another approach for fast dynamic response are the min- imum time controls [13–20] which pre-calculate the control action to achieve a time-optimal response or a near-optimal response with current limit. These controls are digitally imple- mented and behave in open-loop during transient responses so their correct behavior is not guaranteed under pulsating loads. Also, adaptive controls [21–29] are a trending topic in the area of improving the dynamic response of converter. These controls change parameters of the control (ramp, hysteretic band, ...) according to the conditions of the system. This approach can improve the robustness of the control and/or its dynamic response compared to its non-adaptive counterpart. Yet, this advantage comes at the expense of a more complex control system. As seen, in the scientific literature, a wide variety of controls appear to provide a fast dynamic response. However, from the point of view of the industry, low-cost simple solutions to control the converter are needed. This paper shows how by only measuring the output voltage and just with a type-III controller, an extremely fast reaction under load steps can be achieved, if designed correctly. The article is structured as follows. Section II reviews the funda- mental behavior of ripple-based controls and proposed control topologies. Section III introduces the v 1 concept and shows the