Flyback Converter Standby Power System Using Comparator Control
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Solution Overview
Problem
Flyback converters experience high power consumption during standby mode due to the need for an active feedback loop, which is not effectively reduced by existing methods that focus on reducing IC current or shutting down functional blocks.
Innovation Solution
Implementing a standby power system with a comparator that powers down the feedback loop when a device is disconnected, using either a secondary-side or primary-side comparator to regulate the output voltage and control the power switch transistor, resulting in a low-duty cycle digital signal through an opto-coupler, thereby minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the feedback loop remains active to regulate output voltage during standby mode, then the output voltage is maintained, but the power consumption increases due to the error amplifier and loop filter consuming power
Solution Approach 1:
The feedback loop is segmented into two operational modes: normal mode with full feedback loop operation (error amplifier, loop filter) for precise voltage regulation, and standby mode with simplified comparator-based operation. This segmentation allows the system to use only the essential components (comparator, opto-coupler) during standby, reducing power consumption while maintaining basic voltage regulation capability.
Solution Approach 2:
The system changes the operational parameters of the feedback loop based on load conditions. During standby mode, the complex analog feedback path is disabled and replaced with a digital comparator-based control scheme. This parameter change transitions the system from continuous analog regulation to periodic digital regulation, significantly reducing power consumption while maintaining acceptable voltage regulation.
2Reliability
If the opto-coupler conducts continuous current to transmit control voltage, then the feedback signal is continuously transmitted, but the power loss increases
Solution Approach 1:
The opto-coupler operates in periodic pulses rather than continuous conduction. The comparator triggers brief current pulses through the opto-coupler only when voltage regulation is needed, rather than maintaining continuous current flow. This periodic operation dramatically reduces the average power loss in the opto-coupler while ensuring the feedback signal is transmitted sufficiently to maintain voltage regulation.
3Use of energy by moving object
If IC quiescent current is reduced by shutting down functional blocks, then the power consumption decreases, but the feedback loop cannot regulate voltage properly
Solution Approach 1:
The essential voltage regulation function is extracted from the complex feedback loop and implemented by a simple comparator during standby mode. The comparator, opto-coupler, and power switch form a minimal viable feedback system that maintains basic voltage regulation without requiring the error amplifier, loop filter, and other power-consuming functional blocks. This extraction allows shutdown of non-essential blocks while preserving core regulation capability.
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
The solution achieves 'zero standby power' consumption of 5 mW or less by powering down the feedback loop and optimizing the duty cycle of the opto-coupler signal, significantly reducing power consumption during standby mode.
Implementation Method 1
the opto-coupler then conducts a continuous current, which also increases loss
Data Source
AI summary
A standby power system for a flyback converter is disclosed. The flyback converter includes a primary-side, a secondary-side, an output terminal at the secondary-side, and a secondary-side controller, where the output terminal is configured to electrically connect to a load. The standby power system comprises a comparator at the secondary-side, an opto-coupler in signal communication with the primary-side, the secondary-side, and the comparator, and a cable detach detector (or load detector). The cable detach detector is configured to determine whether a device is electrically connected to the flyback converter through a charging cable and to set the flyback converter into a standby mode if the deice is disconnected from the charging cable.