Design And Verification Of Asynchronous Boost DC-DC Converter XD1728

With the rapid development of electronic technology,various types of equipment have been constantly updated in recent years.However,the supporting power management equipment still can’t meet the requirements.The size of portable device has been reduced,but the capacity of battery is still limited.The core control module of modern device has been upgraded,but the anti-noise interference capability and output voltage ripple of power supply still can’t meet the standard.The equipment has become lighter,but the traditional power equipment is too cumbersome.What is more,with widely application of power chips,it has great need for larger load range which is still limited.That’s why efficiency,small size,low ripple,wide load range have become the key research of DC-DC converter.This paper starts with the demand of high performance power IC and is supported by CAD lab of Xi’an University.This paper adopts a boost DC-DC converter as its research object.It systematically studies the basic principle and key technology of DC-DC converter and designs a widely applied,with fast transient response,high integrated and efficient power IC.In the aspect of structure,this paper uses the way of asynchronous rectification to reduce the layout area and simplify the control mode.It uses the method of pulse width modulation to increase the range of load current.And it uses peak current mode control as its loop control pattern to improve the transient response of XD1728.In the aspect of stability,this paper puts forward a compensatory scheme which includes current loop and voltage loop to ensure the stability of boost DC-DC converter.It designs a slope compensation circuit to avoid sub-harmonic oscillation when the converter works at the situation of large duty cycle.And it contrives a Type-II compensation circuit to increase the low-frequency gain and compensate the whole loop.At the same time,this paper puts forward a simplified model to verify this compensation circuit.In the aspect of sub-module design,this paper puts forward an E/D NMOS voltage reference which has high power supply rejection ratio,low quiescent current and wonderful temperature coefficient to improve the performance of the converter.In the aspect of test and verification,this paper designs a printed circuit board to test the research result of this paper.This test PCB uses the technique of a single point of common ground to overall arrange and wire it.This test PCB can effectively reduce the high frequency noise which is caused by parasitic inductance and capacitance and it can reduce the power consumption which is generated by the large current during the trace.So that the PCB can also improve the stability and overall efficiency of the converter.The chip of XD1728 integrates over temperature protection,over current protection,under voltage locked out protection and other protection modules to ensure its safety and stability.XD1728 uses TSOT25 as its package which makes the size of chip small.And the package can also simple the external circuit of the converter.The chip can be used in wireless communications systems,wireless devices,digital cameras et al.The chip of XD1728 adopts 0.5μm 6V/40 V BCD process for its design and tape-out.And it uses Cadence,Spectre and other EDA tools to design,simulate and verify the circuit.It adopts Tektronix,Gwinster,Rigol and other companies’ tools of oscilloscope,power supply,digital multimeter to test.The test result shows that the circuit function meets the design expectation and the performance of the chip satisfies the corresponding index.There still have lots of disadvantage with the chip of XD1728 which needs to be improved.For example,the quiescent current of the chip can be lower,the efficiency and transient response of the chip can be improved better,the uprush and undershoot voltage of the chip can be reduced smaller and he fixed frequency of the chip can be improved higher.