Average input current limit method and apparatus thereof

A voltage regulator circuit, comprising:

• a switching circuit having an input current;
• a current average circuit electrically coupled to said switching circuit to generate a signal indicative of the average value of said input current;
• and
• a current limit circuit electrically coupled to said switching circuit and said current average circuit to limit said average value of said input current to a value,
• wherein said switching circuit further comprises an input switch through which said input current flows;
• wherein said current average circuit comprises:
• a current sensing circuit electrically coupled to said input switch to sense said input current and generate a sensed current proportional to said input current;
• a first capacitor electrically coupled to said current sensing circuit and said current limit circuit;
• and
• a first switch electrically coupled across said first capacitor;
• wherein when said first switch is on, said first capacitor is charged by said sensed current and when said first switch is off, said first capacitor is discharged;
• wherein said first switch is turned on and off complementarily to said input switch;
• wherein said current limit circuit compares the voltage across said first capacitor with a threshold voltage and turns off said input switch when said voltage across said first capacitor and said threshold voltage fulfill a relationship;
• wherein said relationship is that said voltage across said first capacitor is larger than said threshold voltage;
• wherein said current limit circuit comprises:
• a comparing circuit, comparing the voltage across said first capacitor with said threshold voltage and generating a comparing signal, if the voltage across said first capacitor is larger than said threshold voltage, said comparing signal is valid, otherwise, it is invalid;
• and
• a control circuit, electrically coupled to said comparing circuit and said switching circuit, to receive said comparing signal and control the on and off function of the switches in said switching circuit;
• wherein when said comparing signal is valid, said control circuit turns off said input switch;
• wherein said comparing circuit comprises a second comparator, the non-inverting terminal of said second comparator is electrically coupled to said first capacitor to receive the voltage across it, the inverting terminal of said second comparator is electrically coupled to said threshold voltage, and the output terminal of said second comparator is coupled to said control circuit to output said comparing signal;
• and
• wherein said control circuit comprises:
• a feedback circuit, electrically coupled to said switch circuit, operable to sense a parameter of said switch circuit and generate a feedback signal;
• a third comparator, the non-inverting terminal of said third comparator is electrically coupled to said first capacitor to receive the voltage across it, the inverting terminal of said third comparator is electrically coupled to said feedback signal;
• and
• a flip-flop with two reset terminals and one set terminal, the set terminal of said flip-flop is coupled to a clock signal, one reset terminal of said flip-flop is electrically coupled to the output terminal of said second comparator, the other reset terminal of said flip-flop is electrically coupled to the output terminal of said third comparator, the output terminal of said flip-flop is used to control switches in said switching circuit.