Switch controller, power supply device comprising the same, and driving method of the power supply device

A method of driving a power supply device, the method comprising:

• providing a power supply device comprising:
• a power switch having a first terminal and a second terminal, the first terminal receiving an input voltage, the input voltage having a rectified Alternating Current (AC) voltage component;
• a diode coupled between the second terminal of the power switch and a ground;
• and
• a sensing resistor coupled between the second terminal of the power switch and an inductor;
• generating a first reference having a first waveform including an AC component, the AC component of the first waveform having a phase synchronized with a phase of the rectified AC voltage component of the input voltage;
• generating a second reference having a second waveform including an AC component, the AC component of the second waveform having a phase synchronized with the phase of the rectified AC voltage component of the input voltage;
• comparing a modulation sensing voltage that is based on a sensing voltage generated by the sensing resistor with the first reference when an LED string is connected between the inductor and the ground;
• comparing the modulation sensing voltage with the second reference;
• detecting a zero crossing detection period based on the comparison of the modulation sensing voltage with the second reference;
• determining a zero crossing time point during the detected zero crossing detection period;
• determining a one set period of the input voltage using the zero crossing time point,
• generating a clock signal with edges corresponding to a reference number of times during the one set period of the input voltage;
• generating a first digital signal configured to be increased and reduced corresponding to the reference number of times based on the clock signal during the one set period of the input voltage;
• and
• generating a second digital signal configured to be increased and reduced corresponding to the reference number of times based on the clock signal during the one set period of the input voltage;
• and
• turning off the power switch based on the comparison of the modulation sensing voltage with the first reference and turning on the power switch based on the comparison of the modulation sensing voltage with the second reference,
• wherein the first reference and the second reference are references for controlling an upper limit and a lower limit of an LED current flowing through the LED string, respectively,
• wherein generating the first reference includes converting the first digital signal into a first analog voltage signal and generating the first reference using the first analog voltage signal, and
• wherein generating the second reference includes converting the second digital signal into a second analog voltage signal and generating the second reference using the second analog voltage signal.

A switch controller of a power supply device including a diode supplying a current to an LED string based on a switching operation of a power switch including a first terminal to which an input voltage is supplied, the diode being coupled between a second terminal of the power switch and a ground, the switch controller comprising:

• an inverting amplifier configured to invert-amplify a sensing voltage generated from a sensing resistor coupled to the second terminal of the power switch;
• an offset adder configured to add the offset voltage to an output of the inverting amplifier to generate a modulation sensing voltage;
• and
• a digital sine-wave generator configured to detect a period when the modulation sensing voltage is less than a second reference as a zero crossing detection period and further determine a zero crossing time point during the detected zero crossing detection period to set one period of the input voltage, the digital sine-wave generator being further configured to generate a first reference and a second reference based on a full-wave rectification sine-wave during the one set period of the input voltage,
• wherein a switching operation of the power switch is controlled based on the modulation sensing voltage, the first reference and the second reference,
• wherein the first reference and the second reference are to control an upper limit and a lower limit of an LED current flowing through the LED string, respectively,
• wherein the first reference has a first waveform including an AC component, the AC component of the first waveform having a phase synchronized with a phase of a rectified AC voltage component of the input voltage, and
• wherein the second reference has a second waveform including an AC component, the AC component of the second waveform having a phase synchronized with the phase of the rectified AC voltage component of the input voltage.