EMI Suppression Regulator Circuit with Segmented Current Control
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Solution Overview
Problem
Current regulator circuits face challenges in reducing electromagnetic interference (EMI) noise due to high rate of change of current in power supply lines, which affects electromagnetic compatibility (EMC) and increases manufacturing costs, especially in environments with significant electromagnetic noise like automotive systems.
Innovation Solution
A regulator circuit with a controllable current source and capacitor, where the controller restricts the rate of change of the current source output, using feedback from the regulated power supply to manage both lower frequency and higher frequency current components, thereby reducing EMI noise more efficiently than existing solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant current source is used to raise the control voltage during no-load periods, then the transient response is improved and output voltage fluctuations are reduced, but the rate of change of current drawn by the current control element increases
Solution Approach 1:
The current source output is segmented into two distinct components: a low-frequency component (dc or slowly varying) and a high-frequency component (transient). The capacitor couples only the high-frequency transient current component to the output, while the low-frequency component passes through to the current control element. This segmentation allows each component to be optimized independently - the capacitor handles fast transient response without causing large di/dt in the power supply lines.
Solution Approach 2:
A capacitor is introduced as an intermediary element between the current source and the output. This capacitor acts as a mediator that selectively passes high-frequency transient current while blocking low-frequency components. The capacitor's impedance characteristics (low at high frequencies, high at low frequencies) enable it to facilitate transient current flow without transmitting large current changes to the power supply, thus reducing EMI noise while maintaining transient response performance.
2Reliability
If a large capacitor is used to suppress output voltage fluctuations, then the transient response is improved, but the device size and manufacturing cost increase
Solution Approach 1:
The total current requirement is segmented into frequency components, allowing a smaller capacitor to handle only the high-frequency transient portion rather than requiring a large capacitor to handle all current variations. This frequency-based segmentation enables the use of smaller, more compact capacitor values while achieving the same transient response performance.
Solution Approach 2:
Instead of using a large capacitor to provide all current during transients, the solution uses a smaller capacitor that provides only the necessary high-frequency transient current component. The low-frequency current component is supplied separately through the current control element, avoiding the need for excessive capacitance and reducing component size.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces EMI noise by limiting the rate of change of current, allowing for smaller capacitors and lower power dissipation, leading to improved EMC and reduced manufacturing costs while maintaining performance.
Implementation Method 1
a capacitor, the controllable current source circuit and the capacitor being coupled together such that an output of the controllable current source circuit can provide a lower frequency current part of the regulated power supply output, and such that the capacitor can supply a higher frequency current part of the regulated power supply output
Implementation Method 2
the controller being arranged to control the controllable current source circuit according to feedback from the regulated power supply output, and to restrict a rate of change of the output of the controllable current source circuit
Data Source
AI summary
A regulator circuit receives a power supply and provides a regulated power supply output suitable for integrated circuitry. It has a controllable current source circuit, a controller and a capacitor, such that an output of the controllable current source circuit can provide a lower frequency current part of the regulated power supply output, and the capacitor can supply a higher frequency current part of the regulated power supply output. The controllable current source circuit is controlled according to feedback from the regulated power supply output, and to restrict a rate of change of the output of the controllable current source circuit. The amount of EMI noise caused by high rate of change of current in power supply lines to the regulator circuit can be reduced. This can be done more efficiently or using a smaller capacitor than known arrangements.