Capacitive Voltage Divider Power Supply for Microcontrollers

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Solution Overview

Problem

Existing power supply systems for low-power microelectronic devices, such as those in 'Smart Outlets' and 'Smart Grids', face challenges in efficiently providing low voltage DC power from AC mains due to the large size and susceptibility to interference of traditional cap dropper circuits, which are not suitable for microelectronic devices where space and reliability are critical.

Innovation Solution

A power supply system that includes a capacitive voltage divider with a controller to selectively charge a second capacitor at different rates based on voltage thresholds, using a switch to bypass the first capacitor and provide additional power when needed, leveraging normally wasted CPU cycles and pins for improved efficiency and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a cap dropper circuit is used to provide power to low-power controllers, then the circuit can be simple and low-cost, but the component size becomes large and susceptibility to interference increases

Engineering Contradiction:

Improvecircuit simplicityVSAvoidsusceptibility to interference

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The power supply circuit is divided into two distinct paths: a first path through a capacitor for normal low-power operation, and a second path through a switch for high-power modes. This segmentation allows the system to optimize for different operating conditions, reducing interference susceptibility while maintaining simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between two power supply paths based on power requirements. The controller activates the switch during high-power modes (such as RF transmission) and uses the capacitor path during low-power modes, making the power supply adaptive to changing conditions and reducing interference susceptibility.

Inventive Principle:

Principle #15Dynamics

2Ease of manufacture

If a cap dropper circuit is used to provide power to low-power controllers, then the circuit can be simple and low-cost, but the component size becomes large

Engineering Contradiction:

Improvecircuit simplicityVSAvoidcomponent size

Core Design Contradiction:

Ease of manufactureVSVolume of moving object

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the electrical parameters (impedance, power delivery capability) by switching between two different power supply paths. The capacitor path provides high impedance for low-power operation, while the switch path provides low impedance for high-power modes, optimizing both size and performance.

Inventive Principle:

Principle #35Parameter changes

3Power

If the controller needs additional power for high-power modes, then the power supply capability must be increased, but the circuit complexity increases

Engineering Contradiction:

Improvepower supply capabilityVSAvoidcircuit complexity

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The invention merges two power supply approaches (capacitor dropper and switch-based) into a single unified circuit. The switch can connect to either the capacitor path or directly to the AC input, combining the benefits of both approaches without requiring separate circuits for different power modes.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The switch serves multiple functions: it can bypass the capacitor for high-power modes, connect to different AC input phases for power factor correction, and provide surge protection. This multi-functionality increases power capability without proportionally increasing circuit complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution enables efficient, reliable, and cost-effective provision of low DC power to microcontrollers with reduced component size and susceptibility to interference, allowing for improved power management and surge protection.

Implementation Method 1

a rectifier configured to convert the input AC power into rectified DC power

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

a capacitive voltage divider including a first capacitor and a second capacitor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

a switch selectively coupled across the first capacitor, and configured to selectively bypass the first capacitor

Methodology Applied

Scientific EffectElectrical switching:

Data Source

PatentEP2820753B1Method for providing low voltage DC power from ac mains power

Publication Date: 2018.10.17 SCHNEIDER ELECTRIC IT CORP

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AI summary

According to one aspect, embodiments of the invention provide a power supply system comprising an input line configured to receive input AC power, a first capacitor coupled to the input line, a second capacitor, a controller, a rectifier having an input coupled to the first capacitor and an output coupled to the second capacitor, the second capacitor further coupled to the controller, and a switch selectively coupled across the first capacitor, and configured to selectively bypass the first capacitor, wherein the controller is configured to detect a voltage across the second capacitor, operate the switch to charge the second capacitor at a first rate if the voltage is above a predetermined threshold, and operate the switch to charge the second capacitor at a second rate if the voltage is below a predetermined threshold.