Analysis and Design of a Low-Power Integrated Controllable High-Voltage Start-Up Current Source

A low-power integrated controllable high-voltage start-up current source for an off-line switched-model power supply chip is presented. The proposed structure features a thick gate oxide MOSFET which is controlled by a voltage sensor. In the supply voltage range of 100-400 V, the sensor can output a steady high voltage. The optimized total area is 0.025 mm$^{2}$, less than 1 % of a 12 W SPMS chip. Under a 100 V supply voltage, the initial charging time and recharging time are 0.12 s and 0.08 s, with the load of a 10 $\mu$ F capacitor in parallel with $\mathrm{a}20 \mathrm{k}\Omega$ resistor, respectively.