Vivanco UNIVERSAL SWITCHMODE AC TO DC MAINS ADAPTERS WITH USB CHARGING FUNCTION Uživatelská příručka stáhnout pdf (Strana 47)

Hardware Design

EQUATION 2-31:

Therefore, the total capacitor ripple current is 1.7 Arms. Another important design

consideration for the bulk capacitors is the transient load requirements, so low

ESR/ESL parts are required to meet the specification (see Reference 12 in Appendix

C. “References”). Two Rubycon 10ZL1500M10X23 1500 μF, 10V electrolytic

capacitors, plus four 10 μF, 16V multi-layer ceramics in parallel were selected. The

electrolytic capacitors are each rated to 2.15 Arms at 105ºC, which can easily handle

the ripple current on their own.

2.4 THREE-PHASE SYNCHRONOUS BUCK CONVERTER

Multiple synchronous Buck converters can be connected in parallel to increase the

power handling of a step-down voltage stage. Performance improvements and a

reduction in output capacitor size can be achieved by phase-shifting the PWM

modulation in each stage. In this reference design, a Three-Phase Synchronous Buck

converter has been designed. The power circuit is shown in Figure 2-12 and illustrates

the switching cycle 120 degree PWM phase-shifting in the output choke currents.

FIGURE 2-12: THREE-PHASE SYNCHRONOUS BUCK CONVERTER

cap

VBUS

VOUT

1 2 ... 42 43 44 45 46 47 48 49 50 51 52 ... 117 118

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Vivanco UNIVERSAL SWITCHMODE AC TO DC MAINS ADAPTERS WITH USB CHARGING FUNCTION Uživatelská příručka Strana 47