The effect of capacitor equivalent series inductance on DC-DC converter performance and stability

Abstract

Equivalent Series Inductance (ESL) is a parasitic inductance in tantalum and aluminum electrolytic capacitors. These capacitors are frequently used as the filter capacitors in DC-DC converters, because of their high ripple current capacity. The effect of ESL is usually neglected when the DC-DC converter performance is analyzed and evaluated. The trend for DC-DC converters is to increase the power density; this causes higher and higher ripple current to flow into the filter capacitors. As the ripple current increases, the effect of the ESL on the converter stability becomes quite significant. This paper discusses the effect of the filter capacitor ESL on converter stability, derives the open loop transfer function in closed form and verifies the model with experimental data.

Analytical multi‐parametric stability boundaries of DC‐DC buck converters under V1 control concept

“…which agrees with steady-state analysis on the basis of net volt-seconds assuming low ripple at the output voltage [1]. Hence, there is no need for solving the switching Equation In fact, the value of v i (0) = v i (T) is to be determined from the switching condition (19). From this condition, the integral variable v i (DT) at time instant DT is given by the following expression:…”

“…The matrix − e T is nonsingular because the integrator has been excluded from the vector of the state variables but has been included in the switching condition (19). Note that without excluding the integral variable from , the problem will be ill-posed and this matrix will be singular because the integral variable cannot reach a constant steady-state without closing the loop by the switching condition [16].…”

“…However, its value becomes significant at high switching frequencies. Details on accurate modeling of capacitors can be found in . While, traditionally, this parameter is neglected for stability analysis, it has been shown in that its effect cannot be ignored.…”

“…(19) to determine the operating duty cycle D in the presence of an integral action in the output voltage feedback loop such as in V 1 control. Note that there is an infinite number of solutions for v i (0) and equivalently v i (DT) if these values are to be determined from (20a) and (20b) because even if v o (0) is fixed, there are infinity of values of v o (DT) that will give v o (0) = v o (T) depending on the value of D or equivalently v ref .…”

Active cancellation of capacitor ESR and ESL effects for improving converter transient and steady-state response

“…The value of ' t is largely dependent on the value of C L . Thus, reducing the values of ESR and ESL can reduce the ESR drop and duration of the ESL spike [15]. Fig.…”