Switching control circuit

A switching control circuit configured to prevent overcurrent through a transistor that is switched to provide an output voltage at a target level, the switching control circuit comprising:

• a resistor connected between a source terminal of the transistor and an input voltage;
• a reference voltage generating circuit configured to generate a first reference voltage indicative of a reference current and that varies inversely with the output voltage when the output voltage is between a first voltage level and a second voltage level, wherein the first reference voltage is constant when the output voltage is below the first voltage level and above the second voltage level;
• a comparing circuit that compares a voltage at the source of the switching transistor with the first reference voltage, wherein the voltage at the source electrode of the transistor is indicative of an output current through the transistor;
• and
• a driving circuit configured to:
• turn on/off the transistor based on a feedback voltage corresponding to the output voltage and a second reference voltage corresponding to the target level so that the output voltage reaches the target level, when the comparing circuit determines that the output current is smaller than the reference current, and
• turn off the transistor when the comparing circuit determines that the output current is greater than the reference current.

A method of forming a switching control circuit that prevents overcurrent through a transistor that is switched to provide an output voltage at a target level, the method comprising:

• forming a resistor connected between a source terminal of the transistor and an input voltage;
• forming a reference voltage generating circuit to generate a first reference voltage indicative of a reference current and that varies inversely with the output voltage when the output voltage is between a first voltage level and a second voltage level, wherein the first reference voltage is constant when the output voltage is below the first voltage level and above the second voltage level;
• forming a comparing circuit to compare a voltage at the source of the switching transistor with the first reference voltage, wherein the voltage at the source electrode of the transistor is indicative of an output current through the transistor;
• and
• forming a driving circuit configured to:
• turn on/off the transistor based on a feedback voltage corresponding to the output voltage and a second reference voltage corresponding to the target level so that the output voltage reaches the target level, when the comparing circuit determines that the output current is smaller than the reference current, and
• turn off the transistor when the comparing circuit determines that the output current is greater than the reference current.