Flyback Secondary-Side Power Supply Switching to Cut LDO Loss
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Solution Overview
Problem
Conventional flyback power converters experience reduced power conversion efficiency due to increased electrical power consumption by secondary side circuits, particularly under light load conditions, as the voltage drop across low-dropout linear regulators (LDOs) in synchronous rectification and protocol chips increases, leading to inefficient power supply operations.
Innovation Solution
Implementing a flyback power converter with a first and second lossless voltage conversion circuit and LDOs that convert secondary side winding voltage in a lossless fashion, generating operation voltages that are shunted to a common node, replacing lower efficiency voltages with higher efficiency ones when the threshold is exceeded, ensuring unidirectional power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional LDOs are used to supply power to secondary side circuits, then the circuits can operate with simplified power supply design, but the voltage drop across LDOs increases electrical power consumption and reduces power conversion efficiency
Solution Approach 1:
The power supply system is segmented into multiple independent LDOs (first LDO, second LDO) that can operate independently. Each LDO has its own control switch that can be selectively enabled or disabled based on operating conditions, allowing the system to optimize power conversion efficiency by choosing the most efficient LDO for the current load condition while maintaining simplified overall design.
Solution Approach 2:
The power supply system dynamically switches between different LDOs based on operating conditions (light load vs. heavy load). The control circuit monitors the operating state and selectively enables the first LDO for light loads or the second LDO for heavy loads, making the power supply adaptive to changing conditions to minimize energy loss.
2Device complexity
If a single power supply circuit is used for all load conditions, then the circuit design is simpler, but the power conversion efficiency deteriorates under light load conditions
Solution Approach 1:
The power supply system uses multiple LDOs that can serve different functions under different operating conditions. The first LDO is optimized for light load conditions while the second LDO handles heavy load conditions, making each component universal in its ability to operate across different scenarios while being specialized for optimal performance in its designated range.
Solution Approach 2:
The system changes operating parameters by switching between different LDOs based on load conditions. When the load changes from light to heavy or vice versa, the control circuit changes which LDO is active, effectively changing the power supply parameters to match the current operating conditions and maintain high efficiency.
3Loss of energy
If multiple LDOs are implemented with selective switching, then power conversion efficiency is improved across varying load conditions, but the device complexity increases
Solution Approach 1:
Multiple LDOs are merged into a single integrated power supply system with unified control. The first LDO and second LDO share common components such as the power transformer secondary winding, rectification circuitry, and control logic, allowing the system to achieve improved efficiency across load ranges while minimizing the increase in overall complexity through shared resources.
Solution Approach 2:
A control circuit acts as an intermediary between the multiple LDOs and the load. This intermediary monitors operating conditions and selectively enables or disables specific LDOs, managing the complexity of having multiple power supply paths while ensuring that only the appropriate LDO is active at any given time, thus reducing the practical complexity burden.
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
Enhances power conversion efficiency at the secondary side by reducing electrical power consumption and maintaining efficient power supply operations across varying load conditions.
Implementation Method 1
the power transformer TR1 converts an input voltage Vin to an output voltage Vout via electromagnetic induction
Implementation Method 2
a first lossless voltage conversion circuit, which is configured to operably convert a secondary side winding voltage across the secondary side winding in a lossless fashion, to generate a first lossless conversion voltage
Implementation Method 3
the first LDO is configured to operably and linearly convert the first lossless conversion voltage to a first operation voltage
Data Source
AI summary
A flyback power converter includes a power transformer, a first lossless voltage conversion circuit, a first low-dropout linear regulator and a secondary side power supply circuit. The first low-dropout linear regulator (LDO) generates a first operation voltage as power supply for being supplied to a sub-operation circuit. The secondary side power supply circuit includes a second lossless voltage conversion circuit and a second LDO. The second LDO generates a second operation voltage. The first operation voltage and the second operation voltage are shunted to a common node. When a first lossless conversion voltage is greater than a first threshold voltage, the second LDO is enabled to generate the second operation voltage to replace the first operation voltage as power supply supplied to the sub-operation circuit; wherein the second lossless conversion voltage is lower than the first lossless switching voltage.