Synchronous Rectifier Control for Low-Load Power Efficiency
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Solution Overview
Problem
Power converter circuits with synchronous rectifier output stages face inefficiencies at low loads due to switching losses, and existing solutions do not effectively manage power consumption under no-load or very light load conditions.
Innovation Solution
A power converter circuit that uses a switched mode power supply configuration with a transformer and a synchronous rectifier control circuit to modulate a transistor on the secondary side, inhibiting synchronous rectification at low loads and using a diode at no-load conditions to reduce power losses, while employing feedback circuitry and pulse width modulation to regulate output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If synchronous rectifier is activated continuously, then high load efficiency is maintained, but no-load power consumption increases
Solution Approach 1:
The patent extracts the synchronous rectifier from continuous operation and selectively activates it only when needed. By removing the synchronous rectifier from the always-on configuration and instead gating its operation based on load conditions, the system eliminates unnecessary power consumption during no-load or light-load periods while preserving high efficiency during heavy-load operation.
Solution Approach 2:
The control circuit automatically monitors load current and self-regulates the synchronous rectifier's operation without external intervention. When load current exceeds the threshold, the system automatically enables synchronous rectification; when it drops below, the system automatically switches to diode rectification, making the system self-adjusting to load conditions.
2Use of energy by moving object
If diode rectification is used, then no-load power consumption is reduced, but efficiency at high loads decreases
Solution Approach 1:
The patent segments the rectification function into two distinct pathways: diode rectification for light-load conditions and synchronous rectifier operation for heavy-load conditions. This segmentation allows each rectification method to operate in its optimal performance range, with the diode handling no-load and light-load scenarios efficiently, and the synchronous rectifier taking over when high current demands require its superior efficiency.
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 enhances efficiency by activating synchronous rectification only at higher load currents, reducing power losses under low-load conditions, and maintaining high efficiency across varying load levels by dynamically switching between diode and transistor operation based on load current monitoring.
Implementation Method 1
A transformer in an AC to DC power converter may have primary and secondary windings. A pulse width modulation (PWM) circuit on the primary side of a transformer may generate pulses of current that pass through the primary winding of the transformer.
Implementation Method 2
On the secondary side of the transformer, a diode may be used to rectify the output of the secondary winding.
Implementation Method 3
SR output stages include a metal-oxide-semiconductor field-effect transistor (MOSFET). The MOSFET is driven so as to rectify the output waveform from the transformer in the same way that the diode is used in other power converter designs while avoiding high diode voltage drops when conducting current.
Implementation Method 4
A pulse width modulation (PWM) circuit on the primary side of a transformer may generate pulses of current that pass through the primary winding of the transformer.
Data Source
AI summary
A power converter circuit may convert alternating current signals into direct current signals. A load may be powered from output terminals that are provided with the direct current signals. The power converter circuit may have a transformer with primary and secondary sides. A transistor on the primary side may be controlled using a pulse width modulation controller. A diode may be coupled in series with the secondary side of the transformer and the load. To improve efficiency at larger load currents, a synchronous rectifier control circuit may modulate a transistor on the secondary side that is coupled in parallel with the diode. The synchronous rectifier control circuit may monitor voltage pulses on the transistor on the secondary side or may make direct load current measurements to ascertain how much load current is flowing. Under low or no load conditions, synchronous rectification can be inhibited to improve efficiency.