Linear Charger Thermal Regulation for Stable Shutdown Temperature
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing linear chargers face issues with thermal regulation, where modulating voltages at the amplifier terminals can lead to variable shutdown temperatures and nonlinear current estimation due to offset voltages, especially at high temperatures, causing potential chip damage.
Innovation Solution
A linear charger with a thermal regulation circuit that modulates both the thermal regulation current and amplifier reference voltage with temperature, ensuring a consistent shutdown temperature and linear current estimation across different setting resistor values, by coupling the thermal regulation circuit to the output and negative terminal of a transconductance amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If only the voltage of the positive terminal of the amplifier is modulated with temperature, then the shutdown temperature may change with different values of the setting resistor, but the circuit structure remains simple
Solution Approach 1:
The thermal regulation function is segmented into two independent parts: modulating the positive terminal voltage through a first transistor and modulating the negative terminal voltage through a second transistor. This segmentation allows each terminal to be controlled independently, ensuring that the shutdown temperature remains consistent regardless of setting resistor values while maintaining a manageable circuit structure.
Solution Approach 2:
The solution transitions from one-dimensional temperature modulation (only positive terminal) to two-dimensional temperature modulation (both positive and negative terminals). By adding the negative terminal modulation dimension, the system achieves temperature-independent shutdown characteristics without excessive complexity increase.
2Reliability
If only the voltage of the negative terminal of the amplifier is modulated with temperature, then the power stage may not be turned off at high temperature due to offset voltage, but the modulation becomes nonlinear
Solution Approach 1:
The thermal regulation is segmented such that the negative terminal modulation handles the power stage shutdown guarantee through offset voltage compensation, while the positive terminal modulation handles the linear charging current estimation. This segmentation allows each function to be optimized independently.
Solution Approach 2:
The patent introduces intermediate calculation circuits that use temperature coefficients to calculate and compensate for offset voltages. These intermediary calculations enable accurate shutdown temperature prediction and linear current estimation by mediating between the nonlinear physical effects and the control objectives.
3Reliability
If the modulation of voltage at the negative terminal of the amplifier with temperature is used, then the power stage can be turned off at high temperature, but the charging current magnitude estimation becomes difficult
Solution Approach 1:
The patent implements feedback mechanisms where the temperature-dependent voltage modulation at the negative terminal is compensated by corresponding feedback signals. This feedback allows the system to maintain accurate charging current estimation despite the nonlinear temperature effects, ensuring both reliable shutdown and precise measurement.
Data Source
AI summary
A linear charger includes a constant current charging circuit and a thermal regulation circuit. The constant current charging circuit is arranged to generate a charging current, and includes a first transconductance amplifier, wherein the first transconductance amplifier has a positive terminal, a negative terminal, and an output terminal. The thermal regulation circuit is coupled to the output terminal and the negative terminal of the first transconductance amplifier, and is arranged to generate and modulate a thermal regulation current and an amplifier reference voltage with temperature, and transmit the thermal regulation current and the amplifier reference voltage to the output terminal and the negative terminal of the first transconductance amplifier, respectively.