Research On Noise Separation And Suppression Technology Of Digital Isolator

In the communication between large-scale power systems and control terminals,the ever-increasing demand for isolation has caused a research boom in related fields such as drives based on electrical isolation.As a core indicator that reflects the reliability and safety of isolators working in complex environments,there are The ability to suppress mode noise has therefore attracted much attention.In this regard,this article takes the magnetic coupling isolation gate driver based on the on-chip transformer as the goal,and focuses on the separation and suppression of common-mode noise related technologies.First of all,this article studies the noise suppression technology of the core isolation component on-chip transformer,analyzes its signal transmission characteristics through modeling,and combines the existing anti-noise design scheme to give a design model.The designed transformer adopts a differential structure with Ground Shielding layer.The inductances of the primary and secondary coils at 200 MHz are 65 n H and20 n H.In a comparative analysis with the common-mode signal transmission of other structures,the peak of the induced electric field of this structure at 200 MHz is reduced by an order of magnitude,and the common-mode signal transmission coefficient is reduced by 18 dB.Secondly,the noise separation and suppression methods of the transformer peripheral modulation and demodulation circuit are studied.At the meantime,this article optimizes the circuit's power consumption,delay and other indicators,and proposes current bipolar modulation technology and digital filter demodulation technology.In the current bipolar modulation technology,the high-frequency oscillation circuit and delay circuit are optimized.The designed symmetrical delay circuit maintains the distortion ratio within 10% in the 1.3 times pulse width delay,which is better than the distortion of the traditional circuit by more than 35%.In addition,the circuit around the transformer always works in current mode under this technology,and the delay from the primary coil driving current to the signal output by the pre-amplifier circuit is about 1.1 ns.When it is used in an overall circuit with 100 kV/?s common mode noise suppression capability,the peak drive current of the transformer primary coil is less than 20 m A,which is 30% of the traditional voltage mode.In the digital filter demodulation technology,a current detection circuit with differential negative feedback,a differential current amplifier circuit with level shift output,a high-speed pre-amplifier circuit and a digital filter demodulation circuit are designed.The specially designed level shift signal combined with the original current sensing signal produces a pair of high-level complementary signals.This article proposes a digital method of OOK demodulation through them.Compared with the traditional diode detection method,it has the advantages of low delay,low pulse width distortion and simple circuit implementation.At the same time,this article proposes a digital method of common-mode noise suppression on this basis,which effectively shields the 100 kV/?s common-mode noise signal in the simulation results.Finally,this article studies the noise suppression methods of other key modules of the isolator,and designs the LDO and output drive circuit with high noise suppression capability.The output voltage fluctuation of the LDO is less than 5.5% under the noise of 100 kV/?s,and the output control signal is not affected.In addition,this article also built a complete half-bridge isolation drive circuit based on the Cadence and ANSYS platforms and performed hybrid simulation verification.The obtained transformer peak drive current is less than 19 m A(Cadence)and 18.5 m A(ANSYS),the transmission delay is 5.2 ns(Cadence)and 5.5 ns(ANSYS),and both have reached 100 kV/?s common mode noise suppression capability.