Patent ID: 9685868
Date: 2017-06-20
CPC Classifications: H02M,Y02B

Claim:
1. A method for digitally controlling a synchronous rectifier within a switch mode power supply for monitoring a demagnetization mode of operation and determining a polarity of an inductor current within the switch mode power supply for controlling an operational state of a switching section of the switch mode power supply such that the inductor current becomes approximately zero amperes at the end of a demagnetization phase of operation, the method comprising the steps of: determining when the switch mode power supply is entering the continuous current mode demagnetization phase of operation; setting a delay time to its base delay based on a delay code; sensing an Inductor input voltage signal indicating a level of the voltage present at an input of a filter section of the switch mode power supply; examining a current sinking switch to determine if it has been deactivated after a period of time; when the current sinking switch is deactivated, determining if the sensed inductor input voltage signal is greater than or less than a reference voltage level; when a current sinking switch is deactivated, incrementing or decrementing a delay counter based on a polarity of the inductor current; programing a delay circuit with an output of the delay counter; activating a discontinuous current demagnetization signal at an activation of a continuous current demagnetization signal indicating that the current sinking switch is making the current discontinuous; initiating the delay circuit to determine the delay time; and at the end of the delay time, deactivating the discontinuous current demagnetization signal to indicate that the current sinking switch is to be deactivated and the inductor current is approximate a zero amp level.