Design of Step-Down Regulator Circuit with Wide Input Voltage

A buck regulator circuit with wide voltage input range was designed,into which buck pre-regulator circuit,pre-reference source and a linear regulator were integrated,to provide power supply for built-in low-voltage module in high-voltage current source IC.Based on 0.6 μm BCD model,the circuit was simulated for verification.Results showed that voltage drop of the buck pre-regulator circuit was less than 50 mV when low-voltage followed,and biasing and reference voltages only changed by 1.13 mV and 0.3 mV,respectively,for an input range from 6 V to 40 V.The linear regulator had a PSRR of-85 dB at low frequency.The analog power output changed by less than 24 mV and 46 mV,respectively,for 6 V and 40 V input at 1 MHz operating frequency,while the digital power output changed by less than 0.3 V and 0.8 V,respectively.The step-down regulator was successfully used in a high-voltage LED constant current source.