Abstract: Current limiting using capacitor charge measurement to limit the supply current or load current of a circuit, or the current flowing through a device or switch, to prevent the time average current in the switch from exceeding a certain safe level. A replica circuit is used to provide a scaled version of the current in the main switch. The current output of the replica circuit is used to charge a capacitor during the first period of the clock signal so that the capacitor voltage, at any time during the on time, is proportional to the time integral of the current output of the replica circuit, and thus, the time integral of the current in the main circuit. The capacitor voltage, in turn, is compared with a known voltage to determine whether the charge that has flowed through the main switch has exceeded a predetermined maximum. The output of the comparator may be used in various ways, including as a control of the clock duty cycle to limit the on time of the main switch. Various embodiments are disclosed.

Abstract: A method for generating, in a switching power supply, an output voltage from an input voltage. The method includes the step of closing a switch in the switching power supply to permit current from the input source to flow through the inductor and the capacitor of the switching power supply, thereby building up an inductor current through the inductor and increasing the output voltage across the capacitor. If a combination of the output voltage and inductor current is satisfactory at the start of an off-time of the oscillator signal, the method opens the switch. If a combination of the output voltage and inductor current is unsatisfactory at the start of an off-time of the oscillator signal, the inventive method preferably keeps the switch closed past the off time of the oscillator signal to continue building up the inductor current through the inductor and increasing the output voltage across the capacitor.

Abstract: A method for generating, in a switching power supply, an output voltage from an input voltage. The method includes the step of closing a switch in the switching power supply to permit current from the input source to flow through the inductor and the capacitor of the switching power supply, thereby building up an inductor current through the inductor and increasing the output voltage across the capacitor. If a combination of the output voltage and inductor current is satisfactory at the start of an off-time of the oscillator signal, the method opens the switch. If a combination of the output voltage and inductor current is unsatisfactory at the start of an off-time of the oscillator signal, the inventive method preferably keeps the switch closed past the off time of the oscillator signal to continue building up the inductor current through the inductor and increasing the output voltage across the capacitor.