High-Voltage Filter for AC-DC Power Supplies
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Solution Overview
Problem
Existing multivoltage AC-to-DC power supplies face challenges with high-voltage capacitors that are expensive and prone to leakage, as they need to handle peak voltages up to 350 volts, which is not efficiently managed by conventional filtering methods.
Innovation Solution
The proposed solution involves a high-voltage filter configuration with two capacitors in series, where a source follower transistor derives an intermediate voltage, and a Zener diode assembly provides a regulated reference voltage to manage the high-voltage DC, ensuring the inter-node voltage remains within safe limits for the capacitors, thereby reducing the risk of leakage and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single high-voltage capacitor is used to filter the high-voltage DC, then the filtering function is provided, but the capacitor becomes expensive and prone to leakage due to the high voltage rating requirement
Solution Approach 1:
The patent divides a single high-voltage capacitor into two lower-voltage capacitors connected in series. Each capacitor only needs to handle half the peak voltage (e.g., 175V instead of 350V), allowing the use of cheaper, more reliable lower-voltage capacitors while maintaining the same filtering function across the full voltage range.
2Reliability
If a voltage dividing network is used to manage high-voltage DC, then the voltage distribution is controlled, but the system complexity increases
Solution Approach 1:
The patent employs a source follower transistor configuration that automatically establishes the correct voltage distribution across the two series capacitors. The transistor's gate is connected to a reference voltage, and it self-regulates to maintain proper voltage balancing without requiring external control circuits or additional active management components.
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 configuration effectively filters high-voltage DC, maintaining stable output to the DC-DC converter with reduced ripple, even across varying AC input voltages, and ensures the capacitors do not exceed their voltage ratings, enhancing reliability and efficiency.
Implementation Method 1
A source follower transistor has a drain coupled to the high-voltage and a source coupled to the intermediate node, with gate coupled to a reference supply
Implementation Method 2
A first capacitor is coupled between the high-voltage DC and an intermediate node. A second capacitor is coupled between the intermediate node and the internal ground
Implementation Method 3
a rectifier providing an internal ground and a high voltage DC
Data Source
AI summary
A high-voltage filter for an alternating-current (AC) to direct current (DC) power adapter of the type having a rectifier providing an internal ground and a high voltage DC, the high voltage DC coupled to drive a DC-DC converter providing a power adapter output, the high voltage filter coupled to filter the high voltage DC, has a first capacitor coupled between the high-voltage DC and an intermediate node. A second capacitor is coupled between the intermediate node and the internal ground. A source follower transistor has a drain coupled to the high-voltage and a source coupled to the intermediate node, with gate coupled to a reference supply. In a particular embodiment, the reference supply has a resistor coupled between the high voltage DC and the gate of the source follower, and at least one zener diode coupled between the gate of the source follower and internal ground.