Contactless card clamp circuits that compensate for regulator reference voltage fluctuations

摘要

A contactless card includes an inductive circuit configured to send and receive signals, a rectifier circuit coupled to the inductive circuit and configured to generate a DC voltage from an AC voltage generated by the inductive circuit, a clamp circuit configured to limit the DC voltage, a regulator circuit configured to regulate the DC voltage and a control circuit configured to selectively enable and disable the clamp circuit and the regulator circuit.

主权项

1. A clamp circuit comprising:
a voltage divider circuit configured to produce a plurality of voltages from a DC voltage; a reference current generation circuit configured to generate a reference current based on a first voltage of the plurality of voltages; a current-to-voltage conversion circuit configured to convert the reference current into a clamp start signal responsive to the reference current and a second voltage of the plurality of voltages; a logic gate circuit configured to perform a logic operation on the clamp start signal output from the current-to-voltage conversion circuit and a control signal received from a controller; and a shunt circuit configured to limit a magnitude of the DC voltage responsive to the clamp start signal.