Design Of PFM-type Primary-side Feedback Switching Power Supply Control Chip

There are many application fields of switching power supply,the market size is huge,and there is a development trend of portability,miniaturization and low cost.Primary-SideRegulation(PSR)is a new control technology that has appeared in recent years.Compared with the secondary-side feedback technology,the primary-side feedback technology removes the optical coupler,TL431,and some matching components.While improving the stability of the system,it also reduces the area of the circuit board and reduces the production cost.At present,the more mature type is the PWM switching power supply.The PWM switching power supply uses the PWM fixed switching frequency to regulate the conduction of the switch.In the standby state,the frequency hopping control method is used.The output ripple will be very large,so it is difficult to achieve low power.Consumption of switching power supply.The best solution to achieve low standby power consumption is to significantly reduce the switching frequency during standby,reduce transmission energy,and achieve the function of low standby power consumption.PFM switching power supply has unparalleled advantages,it is easier to achieve low power consumption and switch control,which has important research significance.This paper designs a PFM-type primary-side feedback switching power supply control chip for flyback switching power supply.The thesis first introduced the basic working principle and control mode of flyback switching power supply in detail,made sufficient theoretical preparations for the design of the chip,and then formulated the functional block diagram of the chip according to its application environment,and introduced the chip in detail according to the design requirements.Key technologies.The chip adopts constant current and constant voltage control mode.When the output voltage is low,the constant current mode is turned on.The output is quickly charged with a constant high current.The output voltage rises slowly.When the output voltage reaches a certain voltage,the constant voltage mode is turned on.The stream mode is turned off and the output is slowly full.According to the functions implemented by the chip,the thesis can be divided into five functional modules,namely the power module,constant voltage module,constant current module,primary peak current limit module and output driver.The main circuit modules include start-up circuits,internal low-voltage source generation circuits,sampling control circuits,error amplifier circuits,constant voltage control circuits,line loss compensation circuits,peak current detection circuits,constant current control circuits,leading-edge blanking circuits,and logic control.Circuit,etc.This paper uses Cadence’s Spectre tool to simulate the test of each sub-circuit module of the chip and gives the waveform data,so that the parameters meet the design requirements.The chip power module can provide a startup voltage of 5.5V and generate a voltage reference of 3.54 V to ensure the normal operation of each module of the chip.The chip can realize constant voltage and constant current control of the application-level circuit,so that the output voltage rises slowly until it stabilizes at 5V.Finally,use the layout editor tool of virtuoso to complete the layout design of the chip based on FMIC’s 1.5μm Bi CMOS process,and use calibre to complete the physical verification of the layout,including the layout graphic design rules and the consistency check of the layout and circuit,respectively DRC and LVS.Meet the chip’s tape-out requirements.