Study And Design Of Constant-Voltage Push-Pull DC-DC Converter Driver Control IC

At present,power management chips appear frequently in many scenarios such as communication base stations,new energy vehicles,LED lighting,medical electronics,and consumer electronics.With the continuous development of wearable electronic devices,the market has put forward higher requirements for the size,efficiency and safety of DC-DC power management chips.Therefore,it is of great practical significance to design an isolated,high-current,high-performance DC-DC power management chip.Based on Taiwan’s NUVOTON 0.35μm 60～80V BCD process,this thesis designs a constant-voltage push-pull DC-DC converter drive control chip,which integrates a low-temperature drift bandgap reference circuit and a high-voltage circuit without off-chip capacitors.LDO circuit,oscillator circuit,leading edge blanking circuit and drive circuit,etc.The working voltage of the chip is 4～24V,and the maximum output power can reach 10 W when it is used to drive the constant voltage push-pull DC-DC converter.By using a tapped transformer to isolate the input and output,adjust the turns ratio of the transformer to output different voltages.The chip integrates an 80 V high-voltage power device with an on-resistance of 320mΩ,which can withstand the impact of 80 V voltage when driving a transformer,effectively improving the reliability of the chip.In this thesis,the highly symmetrical drive circuit design can minimize the magnetic bias phenomenon of the push-pull topology;the design of the soft-start circuit can prevent the power system from outputting an instantaneous large current when the chip is started and damage the chip and other components in the system.And it can ensure that the chip starts with full load in constant current mode.In addition,the design of the over-current protection circuit can temporarily stop the drive circuit when the output current is greater than 2.2A to prevent damage to the power device;the design of the over-temperature protection circuit enables the chip to enter a sleep standby state when the temperature Automatically resume work when it drops below a set threshold.The design of soft-start and over-temperature protection circuit significantly improves system reliability.Using the Cadence Specter simulation environment,the system simulation of the constant voltage push-pull DC-DC converter drive control chip and its application designed in this thesis is carried out.The simulation results show that in the 4～24V voltage working range,the temperature drift coefficient of the bandgap reference is21.3ppm/℃,the high-voltage LDO can stably output 5V voltage to supply power to the internal low-voltage devices,the oscillator frequency is 800 k Hz,and the driving output switching frequency is 400 k Hz.The soft start time is 4ms,and the maximum output power of the converter is 10 W.The simulation results of the constant voltage push-pull DC-DC converter drive control chip designed in this thesis can meet the design index requirements.