As mentioned previously, the proximity of the load curve (Fig. 7.3) of a passive VtoI converter (Fig. 7.1) in the voltage range below 50% of the opencircuit voltage is sufficiently close to the CCS; it can be suitable for some LD-powering applications. The primary condition of a stable current output of a LDD without current feedback is the stability of the LDD input voltage. If the LDD is powered by a battery (the voltage of which varies during operation more than two times), then a conventional switch-mode boost-type converter is required to provide a stable voltage Vdc to the LDD input (Fig. 8.1). A Vdc at least 10% higher than the maximum battery voltage Vbat is sufficient for the boost converter operation. Methods of achieving softswitching in a boost-type converter are described later in this chapter.
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