Patent ID: 7141896
Filing Date: 2006-11-28
Classification: H02M,H03K

Abstract:
1. A signal generator ( 2 ) for generating a pulse width modulated signal, comprising: matched reference ( 4 ) and modulation ( 6 ) ramp circuits, each including a current source ( 8 , 32 ), a capacitance ( 10 ) arranged to be charged by the current output from the current source ( 8 , 32 ), a switch ( 24 ) for discharging the capacitance, and a voltage detector ( 18 ) for detecting a predetermined charge on the capacitance; wherein the output ( 22 ) of the voltage detector ( 18 ) of the reference ramp circuit ( 4 ) controls the switch ( 24 ) of both the reference ( 4 ) and the modulation ramp circuits ( 6 ), wherein the current source of the reference ramp circuit is a fixed current constant current source and the current source of the modulation ramp circuit is a modulated current source having a control input for controlling an output constant current, and in turn for controlling a percentage of time the output current is on; and the output ( 32 ) of the voltage detector ( 18 ) of the modulation ramp circuit ( 6 ) is connected to an output ( 30 ) for providing the pulse width modulated signal.