Switch control circuit and switch control method thereof
A switch control circuit and switch control method are provided. The switch control circuit and switch control method compensate an error of a load current that occurs because of the changing of a slope of an inductor current based on the increase and decrease of an input voltage. The switch control circuit includes a current compensation device that adjusts a gate on time based on a RC resistor and a control signal that senses a gate terminal of a control switch. The current compensation device compensates an error that occurs due to a signal delay to a gate terminal by increasing or decreasing a reference voltage or a sensing voltage, according to an increase or a decrease of an input voltage.
1 . A switch control method, comprising:
determining a change in an input voltage;
changing a reference voltage that is compared with a sensing voltage of a sensing resistor based on the determined change in the input voltage, wherein the reference voltage is decreased when the input voltage increases, and wherein the reference voltage is increased when the input voltage decreases; and
compensating an error of an inductor current by changing a state of a control signal from ‘high’ to ‘low’, by comparing the sensing voltage with the changed reference voltage,
wherein after the input voltage is changed, during a period when the control signal maintains a ‘high’ state for a first time, a gate on-time is adjusted by sensing a gate terminal of a control switch.
2 . The method of claim 1 ,
wherein the switch control is performed in a switch control circuit of a quasi-resonant (QR) buck converter.
3 . The switch control method of claim 1 ,
wherein the gate on-time decreases when the input voltage increases, and the gate on-time increases when the input voltage decreases.
4 . The switch control method of claim 3 ,
wherein after the input voltage is changed, from a period when the control signal maintains a ‘high’ state for a second time, a gate on-time is constantly maintained.
5 . The switch control method of claim 4 ,
wherein when the input voltage increases, the reference voltage decreases, and
wherein when the input voltage decreases, the reference voltage increases.
6 . A switch control method, comprising:
determining a change in an input voltage;
changing a sensing voltage of a sensing resistor that is compared with a reference voltage based on the determined change in the input voltage, wherein the sensing voltage is increased when the input voltage increases, and wherein the sensing voltage is decreased when the input voltage decreases; and
compensating an error of an inductor current by changing a state of a control signal from ‘high’ to ‘low’, by comparing the changed sensing voltage with the reference voltage,
wherein after the input voltage is changed, during a period when the control signal maintains a ‘high’ state for a first time, a gate on-time is adjusted by sensing a gate terminal of a control switch.
7 . The method of claim 6 ,
wherein the switch control is performed in a switch control circuit of a quasi-resonant (QR) buck converter.
8 . The switch control method of claim 6 ,
wherein the gate on-time decreases when the input voltage increases, and the gate on-time increases when the input voltage decreases.
9 . The switch control method of claim 8 ,
wherein after the input voltage is changed, from a period when the control signal maintains a ‘high’ state for a second time, a gate on-time is constantly maintained.
10 . The switch control method of claim 9 ,
wherein when the input voltage increases, the sensing voltage increases, and
wherein when the input voltage decreases, the sensing voltage decreases.