Feedback type active EMI filter optimization method suitable for PWM converter

Abstract

The invention provides a feedback type active EMI filter optimization method suitable for a PWM converter, and the method comprises the following steps: carrying out chaos spread spectrum modulation in the PWM converter, and obtaining a common-mode EMI frequency spectrum, which needs to be attenuated, of the PWM converter through a linear stable impedance network; analyzing a common-mode EMI path of the PWM converter, and designing parameters of an active EMI filter according to a principle topology of the active EMI filter; and according to the original and chaos modulated EMI amplitudes, determining a gain required by an operational amplifier, determining an effective bandwidth, and measuring a filtered common-mode EMI spectrum. According to the method provided by the invention, the characteristic that the EMI frequency spectrum is reduced by using chaos spread spectrum modulation is combined with the design of the active EMI filter, so that the operational amplifier gain required by the active EMI filter is reduced, the effective bandwidth of the active EMI filter is widened, and the high-frequency EMI suppression effect of the active EMI filter is improved.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to an optimal design method for the high-frequency filtering effect of a feedback-type active EMI filter applied in a PWM converter. Background technique [0002] With the rapid development of power electronic converters towards high power, small size, and high power density, their switching frequency has increased significantly, device density has continued to increase, and the spatial structure has become increasingly complex, resulting in more serious electromagnetic interference problems. In order to prevent it from affecting the normal operation of itself and other equipment and ensure its stable operation, it is generally necessary to install a common-mode EMI filter. The addition of the common-mode EMI filter composed of passive capacitive and inductive devices increases the volume and weight of the equipment and reduces the power density; while the active EMI filte...

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Problems solved by technology

[0004] 1. The high cost of components makes active EMI filters less popular in the industry than passive EMI filters. Among them, the cost of operational amplifier components and power amplifier transistor components that meet strict conditions is relatively high, resulting in the production of active EMI filters The cost may be several times that of a passive EMI filter of the same class

[0005] 2. Compared with passive EMI filters, active EMI filters are more prone to unstable problems

When the active EMI filter is unstable, the compensation circuit is prone to self-oscillation, further deteriorating the EMI level of the original circuit

[0006] 3. Due to the characteristics of active devices, the effect of high-frequency EMI suppression of active EMI filters will deteriorate

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