Design Of A 45V Dual H-bridge DC Brush Motor Driver Chip

The development of modern power electronic technology and BCD technology makes the power transmission system increasingly intelligent and miniaturized.As a typical application of power transmission circuit,DC motor drive circuit is widely used in many important fields of today’s national economy.Therefore,the research on the integration of the DC motor drive circuit is of great significance.In this thesis,a DC brush motor driver chip with an input voltage of 8.2V～45V is designed using the CSMC 0.25μm 60 V BCD process.The chip integrates two sets of Hbridges with three protection circuits for under-voltage,over-temperature,and over-current.A single H-bridge can support a continuous current output of 2.5A,and supports three current decay modes: fast,slow and mixed decay.The chip uses pin multiplexing and built in four sets of driving logic,which can realize independent or parallel driving of two sets of H bridges,which can meet the needs of different application scenarios.The key modules designed in this thesis are charge pump,drive circuit and overcurrent protection circuit.The charge pump adopts a cross-coupling structure and is controlled by non-overlapping clock signals,which eliminates the punch-through current during operation and improves the efficiency.The drive circuit prevents the pass-through of the high and low-side power mos of the half-bridge through the gate sampling circuit and the dead zone generation circuit.The overcurrent protection circuit is realized by detecting the conduction voltage drop of the power mos.Aiming at the problem that the open-loop system cannot achieve precise current control,a scheme of sampling the motor drive current through resistance and combining DAC and comparator to achieve precise control of the motor current is used.In the mixed decay mode,the preset current can be achieved within 5% of the preset current.control accuracy.After completing the circuit and layout design,the chip was verified by tape-out.The test results show that: 1)the standby current of the chip is 15μA,and the quiescent current is 6m A;2)the charge pump pumping voltage is 5.7V;3)the chip can work normally in both slow decay and mixed decay modes under a wide input voltage of 8V～30V.However,when the chip works in high current and fast decay mode,there is a negative voltage of more than0.7V at the output point OUT of the H bridge.The negative voltage of OUT will turn on the parasitic NPN inside the chip and extract the charge of the surrounding nodes,as a result,the high-side power mos has a conduction delay in the fast decay mode,and the overcurrent protection is triggered incorrectly,which affects the normal operation of the chip.Aiming at the above problems,this thesis analyzes at the end,proposes an improvement plan,and confirms the correctness of the plan through FIB.