Voltage Ripple Cancellation in Buck Converter based on Hybrid Structured Connection

Active current ripple cancellation in parallel connected buck converter modules

“…Owing to the unaccounted components losses in the PMs, the δ m is adjusted to 28.4% for the correct output voltage. With the practical inductances L m and L x of 28 and 8 μF, respectively, from (18), the δ x( − ) that produced the desired (d/dt)I x(net − ) is calculated to be 7.9% and from (19), the δ x( + ) that produces the desired (d/dt)I x(net + ) is calculated to be 36.5%. Owing to the extra current from the ripple cancellation, the δ m is reduced to 28%, or with a gain of 0.986.…”

“…By rearranging (16) and (17) in terms of the ratio between the two inductors, L m /L x , and the substitution of V o by (12), the relationship between δ m , δ x , and L m /L x for the main PM onand off-period are obtained in (18) and (19), respectively (for a given L m ) is selected based on (18) which is plotted in region 1 (Fig. 5).…”

“…Therefore δ m and the ripple reduction factor p (difference in current ripples between the two PMs) determine the minimum f sx . Using (18) and (19) with f sm selected to be 30 kHz, the minimum frequency ratio f sx /f sm for 1 ≤ p ≤ 3 are shown in Fig. 8.…”

“…Instead of increasing the capacitance, ripple cancellation techniques [14] may be utilised. Over time, numerous current ripple cancellation techniques have been developed for cancelling the input current ripple [15,16] or the output current ripple [17,18]. In passive ripple cancellation techniques [15], the current ripple in the filter inductor is reflected to the secondary inductor that is coupled in anti-parallel to the filter inductor.…”

“…The setback of this scheme is the size of the required filter and also, since the coupled inductor is fixed at the design stage, it is sensitivity to parameter drift. In active ripple cancellation techniques [16][17][18], current is first sensed using a current transformer or Rogowski coil, it is then amplified to the correct amplitude by a linear amplifier for injection back into the converter. The system complexity is higher in this scheme, but they have however been shown to have a higher ripple attenuation at the low frequency range, and with closed-loop control these methods are robust against parameter drift.…”