Receive Circuit Design For Isolated Gate Driver

As precision electronic equipment is more and more widely used in life and precision industry,more and more electronic equipment work in harsh environments,and more and more attention is paid to the reliability and safety of circuits.The function of the isolator is to physically isolate the low-voltage domain from the high-voltage domain of the system.Signals or energy can be transmitted between the two voltage domains by coupling,which greatly improves the reliability and security of the system.With the widespread application of isolator,the working environment of the isolators may be very harsh,and extremely high requirements are put forward for the ability of the isolators to resist common mode interference.Based on the application scenarios of on-chip capacitance and isolated gate driver,this paper designs a receiver circuit suitable for capacitive isolation and adopts on-off keying modulation,which improves the common-mode transient immunity of the isolator.Firstly,this paper takes the isolated drive system as an example to discuss the importance of isolation and common-mode transient immunity in the isolated gate driver system,then the advantages and disadvantages of the isolation capacitor and the commonly used modulation and demodulation methods of the isolator are introduced,subsequently,the principle of the effect of common-mode transient events on the receiver circuit of an isolator using on-chip capacitors is analyzed,and five possible solutions to improve the common-mode transient immunity of the receiver circuit are proposed.In order to improve the common-mode transient immunity of the receiver circuit,the frequency band of the receiver circuit is adjusted according to the proposed scheme to make it have band-pass and amplification capabilities,and a common-mode transient suppression circuit is added.Then the performance parameters and circuit functions of each sub-module are verified by cadence spectre,and then the layout matching requirements of the receiver circuit are given,and complete the layout design and post-simulation verification.Finally,a test environment is set up to verify and test the tape-out isolated gate driver.The test results show that the maximum delay of the rising edge of the isolated gate driver is 120 ns,the delay of the falling edge is about 115 ns,the filtering time is about 60 ns,the withstand voltage of each pin is greater than 30 V,and the common mode transient immunity is greater than 150V/ns.The test result of isolation withstand voltage is greater than 4k V,the result of surge withstand voltage test is greater than 6k V.The test results show that all parameters and functions meet the design requirements.Compared with similar products with a withstand voltage of 1200 V and a common-mode transient immunity of100V/ns,the product designed in this article has a greater improvement in both withstand voltage and common-mode transient immunity.