High voltage start-up circuit for zeroing of standby power consumption and switching mode power supply having the same

A switching mode power supply (SMPS) comprising:

• a high voltage terminal configured to supply a high voltage;
• a junction field-effect transistor (JFET) configured to clamp the high voltage to an intermediate voltage;
• and
• a high voltage start-up circuit configured to receive the intermediate voltage from a source of the JFET and outputting a power voltage for driving SMPS in response to the received intermediate voltage,
• wherein the high voltage start-up circuit comprises
• a power supply terminal configured to supply the intermediate voltage,
• a latch unit connected to the power supply terminal and comprising a first P-type Metal-Oxide Semiconductor (PMOS) transistor, a first N-type Metal-Oxide Semiconductor (NMOS) transistor connected to the first PMOS transistor, a second PMOS transistor, and a second NMOS transistor connected to the second PMOS transistor, wherein the first PMOS transistor and the first NMOS transistor, and the second PMOS transistor and the second NMOS transistor, form a latch structure;
• a charge sharing unit comprising a first capacitor configured to supply a first voltage to a drain of the second PMOS transistor and a second capacitor configured to supply a second voltage to a drain of the first PMOS transistor, and
• a switching unit configured to form a current path that charges an external capacitor using a voltage supplied from the power supply terminal as a power voltage, based on the first voltage and the second voltage.

A high voltage start-up circuit comprising:

• a high voltage input terminal configured to receive a high voltage from an outside source;
• a converter configured to output the received high voltage to a DC voltage;
• a latch unit connected to an output terminal of the converter;
• a charge sharing unit connected to the latch unit, comprising a pull-up capacitor and a pull-down capacitor;
• and
• a switching unit connected to the latch unit and the charge sharing unit, configured to charge an external capacitor with a power voltage.