Mode-changeable power supply circuit and smart card including the same

A smart card, comprising:

• an antenna configured to transmit and receive a radio frequency signal;
• a rectifier configured to rectify a signal received through the antenna, and to output a rectified voltage;
• a voltage regulator configured to stabilize a level of the rectified voltage;
• a regulator converter including a switch configured to provide the rectified voltage to the voltage regulator;
• a load modulator configured to vary a resistance of the antenna to perform a load modulation;
• and
• a clamp circuit configured to connect an output terminal of the rectifier to a ground according to whether the load modulator is activated or deactivated.

A smart card, comprising:

• an antenna configured to transmit and receive a radio frequency signal;
• a rectifier configured to rectify an AC voltage received from the antenna, and to output a rectified AC voltage;
• a voltage regulator including an input terminal connected to an output terminal of the rectifier through a first switch;
• a load modulator configured to vary a resistance of the antenna to perform a load modulation;
• and
• a clamp circuit configured to connect an output terminal of the rectifier to a ground through a second switch,
• wherein the first switch is turned off and the second switch is turned on when the load modulator is activated.