Switching Power Supply Controller EMI Suppression

Solution Overview

Problem

Conventional frequency jittering control in switching power supplies increases conduction loss and electromagnetic radiation, leading to higher heat dissipation and reduced system efficiency, while also failing to effectively suppress electromagnetic interference (EMI) and address stability issues at low loads.

Innovation Solution

A controller for switching power supplies that utilizes an improved frequency-jittering control method, incorporating a frequency-jittering signal generating circuit and a superimpose circuit to adjust the inductor current sampling signal, ensuring the power transistor is turned on at optimal moments, thereby reducing conduction loss and EMI through variable conduction time and switching cycle adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional frequency jittering control is used to suppress conducted EMI, then EMI suppression is improved, but conduction loss increases and system efficiency deteriorates

Engineering Contradiction:

Improveconducted EMIVSAvoidconduction loss

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The patent changes the parameter being jittered from the system switching frequency to the inductor current sampling signal. By superimposing a frequency-jittering signal on the sampling signal rather than changing the switching frequency itself, the patent achieves EMI suppression while maintaining optimal switching timing, thus avoiding increased conduction loss

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary approach by using a frequency-jittering signal that is superimposed on the sampling signal through a superimpose circuit. This intermediary signal modifies the timing without directly altering the switching frequency, allowing EMI suppression while preserving efficient power transistor operation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If conventional frequency jittering control is used to suppress conducted EMI, then EMI suppression is improved, but electromagnetic radiation increases

Engineering Contradiction:

Improveconducted EMIVSAvoidelectromagnetic radiation

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent changes the parameter being jittered from the system switching frequency to the inductor current sampling signal. By superimposing a frequency-jittering signal on the sampling signal rather than changing the switching frequency itself, the patent achieves EMI suppression while maintaining optimal switching timing, thus avoiding increased conduction loss

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary approach by using a frequency-jittering signal that is superimposed on the sampling signal through a superimpose circuit. This intermediary signal modifies the timing without directly altering the switching frequency, allowing EMI suppression while preserving efficient power transistor operation

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If system switching frequency is varied to suppress EMI, then conducted EMI is suppressed, but power transistor turns on at non-ideal moments leading to higher conduction loss

Engineering Contradiction:

Improveconducted EMIVSAvoidconduction loss

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The patent introduces an intermediary approach by using a frequency-jittering signal that is superimposed on the sampling signal through a superimpose circuit. This intermediary signal modifies the timing without directly altering the switching frequency, allowing EMI suppression while preserving efficient power transistor operation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the parameter being jittered from the system switching frequency to the inductor current sampling signal. By superimposing a frequency-jittering signal on the sampling signal rather than changing the switching frequency itself, the patent achieves EMI suppression while maintaining optimal switching timing, thus avoiding increased conduction loss

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9966831B2Controller and controlling method of switching power supply

Publication Date: 2018.05.08 SILERGY SEMICON TECH (HANGZHOU) CO LTD

AI summary

The present disclosure relates to a controller and a controlling method of a switching power supply. The controller of the switching power supply is used for turning on and off a power transistor so that inductor current flows through an inductor which is connected in series with the power transistor. The controller includes a frequency-jittering signal generating circuit, a superimpose circuit and a first comparator. The frequency-jittering signal generating circuit generates a frequency-jittering signal variable over time. The superimpose circuit superimposes the frequency-jittering signal on a sampling signal of the inductor current to generate a superimposed signal. The first comparator compares the superimposed signal with a control voltage to generate an OFF signal for turning off the power transistor. The controller of the switching power supply reduces conducted electromagnetic interference by a frequency-jittering control on the sampling signal of the inductor current.