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This section may be written in a style that is too abstract to be readily understandable by general audiences. When we do this, we see the AC current waveform flowing into and out of the output capacitor (sawtooth waveform). This section may contain an excessive amount of intricate detail that may interest only a particular audience. By continuing your navigation on this site, you must accept the use and writing of Cookies on your connected device.
A two-switch buck-boost converter can be built with two diodes, but upgrading the diodes to FET switches doesn't cost much extra while efficiency improves due to the lower voltage drop. In some cases, the amount of energy required by the load is small enough to be transferred in a time smaller than the whole commutation period. The load current I o {\displaystyle I_{o}} is equal to the average diode current ( I D {\displaystyle I_{D}} ).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. That means that the current I L {\displaystyle I_{\text{L}}} is the same at t = 0 {\displaystyle t=0} and at t = T {\displaystyle t=T} (figure 4). 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. A different control technique known as pulse-frequency modulation can be used to minimize these losses.
The simplified analysis above, does not account for non-idealities of the circuit components nor does it account for the required control circuitry. During on-state, the source may need to momentarily provide more current than its rating for constant load allows, but the on-time is too short for the source to take damage.Devices with built-in EMI reduction technologies reduce design time while helping with compliance to difficult standards such as CISPR 25 Class-5. The voltage across the inductor is V L = − V o {\displaystyle V_{\text{L}}=-V_{\text{o}}} (neglecting diode drop).
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). A mechanical analogy for a buck converter would be to pedal a bicycle in single, strong bursts (Force ~ Voltage), and let the bicycle roll in between (inertia ~ inductor). Furthermore, in discontinuous operation, the output voltage not only depends on the duty cycle, but also on the inductor value, the input voltage and the output current. Static power losses include I 2 R {\displaystyle I
As can be seen in figure 4, t on = D T {\displaystyle t_{\text{on}}=DT} and t off = ( 1 − D ) T {\displaystyle t_{\text{off}}=(1-D)T} . A higher switching frequency allows for use of smaller inductors and capacitors, but also increases lost efficiency to more frequent transistor switching. Both of them can produce a range of output voltages, ranging from much larger (in absolute magnitude) than the input voltage, down to almost zero. So, in steady state operation of the converter, this means that | I o | {\displaystyle \scriptstyle \left|I_{o}\right|} equals 0 for no output current, and 1 for the maximum current the converter can deliver. But with the industry's best noise and ripple performance, TPS62912 and TPS62913 allow you to remove that low-noise LDO in most applications, saving PCB area and overall cost while improving system efficiency.
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