Accurate Feedback Sampling in Switching Power Supply Controllers
Here’s PatSnap Eureka !
Summary
Problems
Switching power supply controllers with on-chip switches face inaccuracies in feedback signals due to parasitic resistance between the chip ground and external ground nodes, which are beyond the designer's control, affecting the accuracy of output voltage regulation.
Innovation solutions
The implementation of a selective feedback sampling circuit, such as a sample and hold (S/H) or track and hold (T/H) circuit, that samples the feedback signal only during specific portions of the switching cycle to mitigate voltage drops caused by parasitic resistance, allowing for accurate output voltage regulation.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If separate power and analog grounds are used to obtain accurate feedback measurement, then feedback signal accuracy is improved, but device complexity and pin count increase
Why choose this principle:
The patent samples the feedback signal at a predetermined time during the switching cycle (when the low-side switch is off and current through parasitic resistance is minimal) before the harmful voltage drop occurs. This preliminary sampling action captures the accurate feedback signal without being affected by subsequent parasitic resistance effects, resolving the contradiction without additional pins.
Principle concept:
If waveform approximation is provided to estimate voltage drop, then feedback accuracy is improved, but knowledge of parasitic resistance value is required which is beyond designer control
Why choose this principle:
The patent extracts only the necessary portion of the feedback signal waveform by sampling at a specific moment when the signal is accurate (when low-side switch is off). Instead of trying to estimate or compensate for the entire waveform including the distorted portion, the solution takes out only the clean, undistorted segment for regulation purposes, eliminating the need to know parasitic resistance values.
Application Domain
Data Source
AI summary:
The implementation of a selective feedback sampling circuit, such as a sample and hold (S/H) or track and hold (T/H) circuit, that samples the feedback signal only during specific portions of the switching cycle to mitigate voltage drops caused by parasitic resistance, allowing for accurate output voltage regulation.
Abstract
A switching power supply controller which includes at least one switching element, and controls a switching cycle during which the switching elements are switched on and off to regulate the power supply's output voltage. The controller has a feedback signal which represents the output voltage, and a circuit node which conducts a current that is higher during a second portion of the switching cycle than it is during a first portion, such that the feedback signal varies with the current conducted by the node. To overcome feedback signal inaccuracies, a sampling circuit samples a signal which varies with the feedback signal only during the first portion of the switching cycle; the controller then regulates the output voltage in response to the sampled signal. The sampling circuit may be further arranged to produce an output which approximates the portion of the feedback signal waveform which is not sampled.