A user friendly boost DC DC converter topology


Posted on Feb 5, 2014

In battery-powered applications, like cell phones, PDAs, digital cameras, etc. , an integrated dc-dc converter circuit solution offers several advantages in terms of cost, size, and design complexity. A critical hurdle in obtaining a fully integrated solution is the frequency compensation circuit, which has to be designed based on the values of external passive filter components


A user friendly boost DC DC converter topology
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(L-C) and associated parasitic elements, like the capacitor equivalent series resistance (ESR). The values of these off-chip components vary due to manufacturing tolerances, parameter drift, and design requirements. Capacitor ESR can vary by orders of magnitude, based on whether the capacitor is electrolytic or ceramic, not to mention its variation across temperature. As such, it is required to have a DC-DC controller IC that can provide fast control and stable operation with widely varying passive component values. In hysteretic control for buck converters, the regulated output voltage includes inductor current ripple information sensed indirectly through capacitor ESR, thus simplifying the loop characteristics. This circuit displays an inherently stable performance and any change in L-C values is accommodated through a change in the converter switching frequency, maintaining stable operation without the use of frequency compensation circuits [1-2]. However, in boost converters, which are used for stepping up single or dual-cell battery voltages for 3. 3 or 5 V applications, the technique is not readily applicable because the inductor current cannot be determined entirely from the output voltage. A strategy that overcomes this limitation in boost converters is presented in Figure 1 [3]. The inductor current, which cannot be determined completely through the capacitor voltage ripple, is independently sensed and regulated...




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