Power Converter Controller Jitter Generation for EMI Reduction
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Solution Overview
Problem
In the constant current mode of power converters, generating jitters in the switching period of the power switch is challenging due to the negative feedback loop that eliminates such jitters, making it difficult to achieve the desired control over the switching period.
Innovation Solution
A controller and method that include a current pin, an auxiliary pin, a constant current control unit, and a control signal generation unit, which adjust the period of the gate control signal based on the primary side voltage, discharge time, and a reference voltage with a predetermined range of jitter voltage, using an oscillator to determine the oscillation frequency and adjust the gate control signal period accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative feedback loop is used to control the switching period, then the average output current converges to a predetermined constant current, but the jitter voltages of the primary side are eliminated and jitters of the switching period cannot be generated
Solution Approach 1:
The controller is divided into separate functional modules: a constant current control unit that maintains stable output current through negative feedback, and a control signal generation unit that introduces jitter to the gate control signal period. This segmentation allows the feedback loop to ensure reliability while the jitter module reduces electromagnetic interference peak power.
Solution Approach 2:
The patent applies asymmetry by adding controlled irregularity (jitter) to the gate control signal period while maintaining symmetric stable operation in the constant current control loop. The jitter voltage is superimposed on the reference voltage to create intentional periodic variations that reduce EMI without disrupting the average current control.
2Measurement precision
If jitter voltages are eliminated by the negative feedback loop, then constant current control is achieved, but it becomes difficult to generate jitters of the switching period for reducing electromagnetic interference
Solution Approach 1:
A jitter voltage signal acts as an intermediary between the constant current control unit and the control signal generation unit. This intermediary signal introduces the desired periodic variations to the gate control signal period, enabling EMI reduction while the constant current control unit maintains precise current control through its feedback mechanism.
Solution Approach 2:
The patent employs periodic action by introducing a jitter voltage that creates controlled periodic variations in the gate control signal period. This periodic modulation reduces the peak power of electromagnetic interference by spreading the spectral energy, while the underlying constant current control maintains measurement precision.
Data Source
AI summary
A controller for generating jitters in a constant current mode of a power converter includes a current pin, an auxiliary pin, a constant current control unit, and a control signal generation unit. The current pin is used for receiving a primary side voltage determined according to a resistor and a primary side current flowing through the power converter. The auxiliary pin is used for receiving a voltage corresponding to an auxiliary winding of the power converter. The constant current control unit is used for generating an adjustment signal according to the primary side voltage, a discharge time corresponding to the voltage, and a reference voltage. The reference voltage has a predetermined range jitter voltage. The control signal generation unit is used for adjusting a period of a gate control signal according to the adjustment signal.