Patent ID: 6982548

Claim:
A switched mode power supply comprising: a controllable switch ( 9 ) for connecting and disconnecting an inductive element ( 7 ) to a power source ( 5 ) in response to a control signal; a current sensor ( 10 ) for sensing a current through the inductive element ( 7 ) and generating a sensing signal corresponding to the current; a reference generator ( 11 ) for generating a reference signal; a comparator ( 12 ) for comparing the sensing signal with the reference signal and generating the control signal; and a compensation circuit ( 14 ) operative on the reference generator ( 11 ) or the current sensor ( 10 ) for adjusting the reference signal or the sensing signal to compensate for delayed disconnecting of the inductive element ( 7 ) by the controllable switch ( 9 ) due to circuitry delay times, wherein the compensation circuit comprises means ( 14 ) for correcting the reference signal or the sensing signal by means of a correction signal proportional to the gradient of the current through the inductive element ( 7 ). wherein the current sensor comprises a sensing resistor ( 17 ) connected in series with the inductive element ( 7 ), the sensing signal being a voltage across the sensing resistor ( 17 ), wherein the reference generator comprises a reference voltage source ( 18 ), the voltage of the reference voltage source being the reference signal, and wherein the compensation circuit comprises; a current mirror ( 19 ) having a current input terminal ( 20 ) and a current output terminal ( 21 ), a capacitor ( 16 ) coupling the voltage across the sensing resistor ( 17 ) to the current input terminal ( 20 ), a compensation resistor ( 15 ) in series with the reference voltage source ( 18 ), the current output terminal ( 21 ) being coupled to the compensation resistor ( 15 ) for causing a current flow through the compensation resistor ( 15 ) so as to form the correction signal.