Synchronous Rectifier Offset Voltage Compensation
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Solution Overview
Problem
DC-to-DC converters using synchronous rectification mode face efficiency issues due to backward current flow through the low-side switch when the current is small, leading to reduced power efficiency.
Innovation Solution
Incorporating a low-side controller with a first detector and an offset canceller to detect and compensate for offset voltages, ensuring accurate detection of zero-crossing currents and preventing backward current flow by synchronizing the high-side and low-side switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the low-side switch is turned off based on detected current to prevent backward current flow, then power efficiency is improved, but offset voltage in current detection causes inaccurate zero-crossing detection
Solution Approach 1:
The patent applies preliminary anti-action by detecting and compensating for offset voltage in the current detection circuit before making zero-crossing detection decisions. The controller measures the offset voltage component and subtracts it from the detected current signal, ensuring accurate zero-crossing detection even in the presence of detection circuit imperfections
Solution Approach 2:
The patent introduces an intermediary offset voltage detection and compensation mechanism between the current detection circuit and the control decision logic. This intermediary layer measures the offset voltage separately and uses it to correct the current detection signal, improving the accuracy of zero-crossing and backward current detection
Data Source
AI summary
According to one embodiment, a DC-to-DC converter includes a high-side switch, a low-side switch, a high-side controller, and a low-side controller. The low-side switch is connected to the high-side switch in series. The high-side controller is configured to control the high-side switch. The low-side controller includes a first detector and an offset canceller. The first detector is configured to detect a current of the low-side switch. The offset canceller is configured to hold an output of the first detector as an offset voltage when the low-side switch is off and compensate an output of the first detector by the offset voltage when the low-side switch is on. The low-side controller is configured to compare a compensated output of the first detector with a reference voltage and turn off the low-side switch.