Patent ID: 6630858
Filing Date: 2003-10-07
Classification: G05F,H02J

Abstract:
A contactless interface circuit for application of a supply voltage to an internal circuit comprising:a supply voltage generating circuit which generates the supply voltage, said supply voltage generating circuit including a contactless circuit receiving an alternating voltage and having an output terminal; a reference voltage generating circuit connected directly to the output terminal of said supply voltage generating circuit, said reference voltage generating circuit generating a reference voltage determined by the supply voltage; a resistance circuit having a first end connected directly to the output terminal of said supply voltage generating circuit and a second end connected to a ground terminal, said resistance circuit consisting of first and second series-connected resistors having a constant fixed resistance value and a dividing point at which the supply voltage is divided, the voltage at said dividing point being identical to the reference voltage when the supply voltage is identical to a predetermined clamp voltage and being determined only by the supply voltage; a decision circuit which detects whether the voltage at the dividing point of said resistance circuit reaches the reference voltage; and a control circuit connected between the output terminal of said supply voltage generating circuit and said ground terminal, said control circuit responding to an output signal of said decision circuit so as to maintain the supply voltage at a value not exceeding a predetermined breakdown voltage, the supply voltage being controlled and supplied simultaneously to the internal circuit.