Ripple current calculation buck converter

Learn more. Ripple current Buck converter Ask Question. Asked 3 years, 11 months ago. Active 3 years, 11 months ago. Viewed 6k times. Reading the datasheet I found this calculation: It shows inductor ripple of mA with given values.

EDIT: Added layout and explained application more. So this is my schematic for this buck: The filament voltage was rated 0. Willy Wonka. Willy Wonka Willy Wonka 6 6 silver badges 18 18 bronze badges. Add a comment. Active Oldest Votes. Adam Lawrence Adam Lawrence Would this be fine for it?

You can lower the ripple current by Layout is also very important, so feel free to post your layout for a review when it's done. Sign up or log in Sign up using Google. Sign up using Facebook.

Sign up using Email and Password. Post as a guest Name. The waveform shows an inductor current operating at CCM. When the drive signal is high, the power switch of a buck converter will close. The current will flow from the input via the power switch going to the inductor and to the load.

During this time, the inductor current will rise linearly. When the PWM signal is low, the power switch will turn off. The inductor voltage reverses in polarity because it will resist to a sudden change in current. As a result, the diode will conduct. Then, the current path is described below. In my designs, I always use the RMS value to compute the component stress and power dissipation. Therefore, I can guarantee ample margin. This is the easiest part! Switching voltage waveform shown as in Figure 1 b is pulsating rectangular.

After LC filtering, assuming corner frequency of LC is much lower than switching frequency, output voltage appears almost pure dc.

It can be understood the higher the inductance L is, the lower the capacitance C leads the same output voltage ripple. However, too big inductor causes high volume and high cost. While too low inductance causes big output capacitor. It is not purely a design trade-off problem.

When power switch is at ON state, the voltage across inductor is voltage difference between input and output voltage. When power switch is at OFF state, inductor voltage is the same output voltage with negative polarity. Form volt-sec balance of a inductor voltage 1 and 3 , one can get the voltage transfer ratio easily,. Duty cycle, D, is defined as the switch turn-on time oven the entire switching period.

Figure 2 shows the inductor current waveform. Because voltage waveform of inductor is pulsating rectangular, the inductor current will be triangular with certain dc level. When ripple factor is less than 2, the converter operates in continuous conduction mode C. M , otherwise discontinuous conduction mode D. Thus, only C. For a fixed inductor, the higher the input voltage, the higher ripple factor is. For a fixed input voltage, ripple factor is higher when the inductance is less.

Higher ripple factor means more ripple current flows though capacitor. If same ripple voltage is required, bigger capacitor is necessary. As described above, the inductor will store energy during switch turn-on period, and release energy while switch turns off. Conceptually, the load current should pass through the inductor, such that enough area of winding wire is necessary. If lower ripple factor or higher inductance is designed, more winding turns is necessary, which leads to bigger size of inductor.

An index for measuring the inductor size called Area Product is introduced, which is the product of effective cross-section area of the core and area of winding window. The unit becomes m 4 rather than m 3 in volume.