Output impedance considerations for switching regulators with current-injected control

Abstract

The output impedance of current-injected controlled (CIC) buck regulators can be significantly reduced by deriving the current control signal from the output capacitor instead of the inductor. This technique is shown to be mathematically equivalent to CIC with loadcurrent feedforward. Performance comparisons with normally implemented CIC and voltage control are given.

Fast control technique based on peak current mode control of the output capacitor current

“…The proposed control is based on the capacitor currentinjected control described in [5] but using a non-invasive output capacitor current sensor [4]. The advantages of this control are: 1) constant switching frequency, 2) fast dynamic response, since it behaves as a feed-forward of the load current, and 3) low sensitivity to parasitic effects and mismatches due to slope compensation.…”

“…The control proposed and analyzed in this paper is based on the peak current mode control of the output capacitor current [5] of a Buck converter (Fig. 4).…”

“…The control proposed in this paper avoids these problems. It is based on the capacitor current-injected control described in [5] but using a non-invasive output capacitor current sensor [4]. With the proposed control the dynamic response is fast and the required bandwidth in the voltage loop is low.…”

Adaptive Output Current FeedforwardControl in VR Applications

“…This approach is particularly useful in VR applications, in which the output current has large and fast transients that need to be tracked, while the bandwidth of the feedback loop is limited by the switching frequency of the converter through a stability constraint [4]. Output current feedforward had been reported earlier as a way of improving the output impedance of a DC-DC converter [5], [6].…”

V²I<inf>C</inf> control: A novel control technique with very fast response under load and voltage steps

“…The fast control technique proposed in [6] and implemented in [7] with the capacitor current estimator of [5] provides good transient response with constant switching frequency and low sensitivity to parasitic effects. Since it is based on the peak current mode control of the output capacitor current and it works as a feed-forward of the load current [8], it achieves fast dynamic response under load steps.…”