Input Voltage Sensing via Startup Charging Current
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Solution Overview
Problem
Traditional voltage dividers consume power when used to detect input line voltage, leading to inefficiency and increased standby consumption in control circuitry.
Innovation Solution
Systems and methods that utilize the charging current from a startup circuit to sense input line voltage without a power-consuming voltage divider, employing transconductance amplifiers, comparators, and transistors to detect voltage without a direct path to ground, thereby reducing power loss and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional voltage divider is used to detect input line voltage, then voltage detection is achieved, but power is continuously consumed
Solution Approach 1:
The patent extracts the voltage detection function from the continuous power-consuming voltage divider by utilizing the existing startup circuit charging current. The detection is performed by monitoring the voltage at the VCC pin during the startup phase without requiring a continuous power path through resistors to ground.
Solution Approach 2:
The startup circuit's charging current, which naturally flows to initialize the controller, is repurposed to perform voltage detection. The same current that serves to power up the system is utilized to sense the input voltage level, eliminating the need for separate detection circuitry that would consume additional power.
2Loss of information
If a voltage divider is used to sense input voltage, then voltage information is obtained, but standby consumption increases
Solution Approach 1:
The startup circuit is designed to serve multiple functions: it provides the charging current necessary to initialize the controller and simultaneously serves as the detection mechanism for input voltage sensing. This multi-functionality eliminates the need for separate standby detection circuits.
Solution Approach 2:
Voltage detection is performed periodically during the startup phase rather than continuously. The system utilizes the natural charging cycle of the startup circuit to obtain voltage information only when necessary, reducing continuous power consumption during standby operations.
3Device complexity
If a direct path from startup resistor to ground through another resistor is provided, then voltage division is simplified, but power loss increases
Solution Approach 1:
The VCC pin of the controller serves as an intermediary node for voltage detection. Instead of creating a direct resistive path to ground, the system uses the VCC pin voltage during startup as the intermediary signal that indicates the input voltage level, avoiding direct power loss through ground-path resistors.
Data Source
AI summary
This document discusses, among other things, systems and methods for detecting a charging current from a startup circuit to a controller without power loss from a voltage divider, and for providing information representative of the charging current to the controller.