A circuit for controlling load switch, applied to a load circuit, which includes a load inductor, a load switch, and at least a working element, wherein the load inductor is electrically connected to the load switch and the working element and generates an inductor current as the load switch is conducted, the circuit for controlling load switch being utilized for controlling the load switch under a continuous conduction mode (CCM) and comprising:
- a first comparator, having a first comparing input, a second comparing input, and a first comparing output, the first comparing input being electrically connected to the load inductor for receiving the inductor current, the second comparing input being utilized for receiving a default average current, and the first comparing output transmitting a first conduction signal as the inductor current reaches the default average current;
- a second comparator, having a third comparing input, a fourth comparing input, and a second comparing output, the third comparing input being electrically connected to the load inductor for receiving the inductor current, the fourth comparing input being utilized for receiving a default ripple current, which is greater than the default average current, and the second comparing output being utilized for transmitting a second conduction signal as the inductor current reaches the default ripple current;
- a first switch, having a gate electrically connected to the first comparing output and a drain electrically connected to a first constant current source, and being conducted when receiving the first conduction signal;
- a second switch, having a gate electrically connected to the second comparing output, a source electrically connected to a second constant current source, and a drain electrically connected to a source of the first switch, and being conducted when receiving the second conduction signal;
- a first controlled capacitor, having one end electrically connected to the source of the first switch and the drain of the second switch and another end grounded to store a capacitor voltage;
- a third comparator, having a fifth comparing input, a sixth comparing input, and a third comparing output, the fifth comparing input being utilized for receiving a variable voltage, which gradually increases as the load switch is turned off, the sixth comparing input being electrically connected to the source of the first switch and the drain of the second switch for receiving the capacitor voltage, and the third comparing output transmitting a re-conduction signal as the variable voltage reaches the capacitor voltage;
- and
- a processing module, electrically connected to the first comparing output and the second comparing output, for turning off the load switch when receiving either the first conduction signal or the second conduction signal, and for conducting the load switch when receiving the re-conduction signal;
- wherein, as the first switch is conducted, the first constant current source charges the first controlled capacitor, as the second switch is conducted, the second constant current source discharges the first controlled capacitor;
- as the load switch is conducted, the inductor current gradually increases, and after the inductor current reaches the default ripple current, the second switch is conducted and the load switch is turned off by the processing module to trigger the variable voltage to increase;
- and as the variable voltage reaches the capacitor voltage, the processing module receives the re-conduction signal to re-conduct the load switch.