Patent ID: 8737947

Claim:
A transponder power supply for providing a supply current based on an antenna input signal, the transponder power supply comprising: an emergency circuit comprising a charging circuit, an emergency capacitor, and an output stage; wherein the charging circuit is configured to charge the emergency capacitor based on the antenna input signal; wherein the output stage comprises a step down converter circuit configured to provide a contribution to the supply current using a charge of the emergency capacitor; wherein the output stage comprises an output control circuit; wherein the step down converter circuit comprises a first converting stage and a second converting stage coupled in parallel between the emergency capacitor and a common VDD node; wherein the output control circuit is configured to generate a non-overlapping clock signal controlling the first converting stage and the second converting stage, such that in a first state the contribution to the supply current is provided at the common VDD node by the first converting stage, and such that in a second state the contribution to the supply current is provided at the common VDD node by the second converting stage; and wherein the output control circuit is configured to compare a signal derived from a supply voltage at the common VDD node with an internal voltage of the first converting stage and an internal voltage of the second converting stage, and to control a frequency or a duty cycle of the non-overlapping clock signal based on the comparisons of the internal voltages with the signal derived from the supply voltage, such that a supply voltage VDD at the common VDD node is in a predetermined range.