This section may contain an excessive amount of intricate detail that may interest only a particular audience. The two circuit configurations of a buck converter: on-state, when the switch is closed; and off-state, when the switch is open (arrows indicate current according to the direction conventional current model). An effective way to ensure low noise while controlling power loss is to eliminate the post-regulator LDO from your power-supply design and use a low-noise DC/DC buck converter.

A buck converter or step-down converter is a DC-to-DC converter which decreases voltage, while increasing current, from its input ( supply) to its output ( load).

This assumption is acceptable because an inductor is made of one long wound piece of wire, so it is likely to exhibit a non-negligible parasitic resistance ( R L). Like the buck and boost converters, the operation of the buck-boost is best understood in terms of the inductor's " reluctance" to allow rapid change in current. From this, it can be deduced that in continuous mode, the output voltage does only depend on the duty cycle, whereas it is far more complex in the discontinuous mode.

The term T V i L {\displaystyle \scriptstyle {\frac {T\,V_{i}}{L}}} is equal to the maximum increase of the inductor current during a cycle; i. DC/DC buck switching regulators with ultra-low-standby quiescent current increase light-load efficiency and extend battery life in portable and battery-operated applications.

while in the Off-state, the inductor is connected to the output load and capacitor, so energy is transferred from L to C and R. A higher switching frequency allows for use of smaller inductors and capacitors, but also increases lost efficiency to more frequent transistor switching. To reduce voltage ripple, filters made of capacitors (sometimes in combination with inductors) are normally added to such a converter's output (load-side filter) and input (supply-side filter). In a physical implementation, these switches are realized by a transistor and a diode, or two transistors (which avoids the loss associated with the diode's voltage drop). The limit between discontinuous and continuous modes is reached when the inductor current falls to zero exactly at the end of the commutation cycle.

Therefore, the locus of the limit between continuous and discontinuous modes is given by 1 2 | I o | D ( 1 − D ) = 1 {\displaystyle \scriptstyle {\frac {1}{2\left|I_{o}\right|}}D\left(1-D\right)=1} . the output voltage can vary continuously from 0 to − ∞ {\displaystyle \scriptstyle -\infty } (for an ideal converter). As I o lim {\displaystyle \scriptstyle I_{o_{\text{lim}}}} is the current at the limit between continuous and discontinuous modes of operations, it satisfies the expressions of both modes. Disconnect the source and use the inertia of the current in the inductor to provide more current than the source delivers ("off" in fig. The output capacitor has enough capacitance to supply power to the load (a simple resistance) without any noticeable variation in its voltage.This current, flowing while the input voltage source is disconnected, when appended to the current flowing during on-state, totals to current greater than the average input current (being zero during off-state).

If the switch is opened while the current is still changing, then there will always be a voltage drop across the inductor, so the net voltage at the load will always be less than the input voltage source.Output voltage ripple is one of the disadvantages of a switching power supply, and can also be a measure of its quality. The Flyback Converter Archived 2017-08-30 at the Wayback Machine - Lecture notes - ECEN4517 - Department of Electrical and Computer Engineering - University of Colorado, Boulder.