Synchronous Rectifier Efficiency Characterization Testing

Overview of Technical Issues:

The control timing circuit insufficiently optimizes the turn-off and turn-on moments of the synchronous rectification switching element, causing harmful reverse conduction or unintended body diode conduction that generates excessive losses and degrades rectification efficiency below target levels; the goal is to characterize and achieve optimal efficiency through precise timing control that eliminates these harmful conduction modes.

Solution directions generated for this problem

Problem Direction 1 :

ImproveSwitching timing control precision
VS
ConstraintControl circuit complexity

Inspiration 1 : Cross-domain reference

Application Principle: #26 Copying
Cross-domain applicability Assess applicability
Virtual ground sensing circuitry and related devices, systems, and methods for crosspoint ferroelectric memory
Innovative Solution Refine solution

Predictive timing model using pre-characterized lookup table for synchronous rectification

Replace real-time sensing with predictive model
How to solve :
  • During factory calibration, sweep timing delays across full operating range (input voltage 10-15V, load current 0-10A in 0.5A steps, temperature 25-85°C) and measure efficiency at each point
  • store optimal timing values in non-volatile lookup table (256-entry EEPROM) indexed by voltage and current
  • During operation, sample input voltage and load current at 10kHz using existing ADC channels in the controller, retrieve pre-determined optimal timing from table via simple address calculation, eliminating sub-10ns real-time sensing circuits
  • Implement linear interpolation between table entries to achieve sub-5ns effective timing resolution: T_optimal = T_base + (ΔV × K_v) + (ΔI × K_i), where coefficients are pre-calculated during calibration
Expected Effect : Timing precision <5ns; circuit adds only 256-byte memory; efficiency improvement 2-4% vs fixed timing
Risk Control :
  • calibration accuracy across production units
  • lookup table memory retention over temperature
  • interpolation error accumulation

Problem Direction 2 :

ImproveSwitching timing control precision
VS
ConstraintTiming measurement precision requirement

Inspiration 1 : Cross-domain reference

Application Principle: #28 Mechanics substitution
Cross-domain applicability Assess applicability
Microcontroller architecture for power factor correction converters
Innovative Solution Refine solution

Magnetic flux sensing for sub-5ns synchronous rectification timing without high-speed electronics

Replace electrical voltage measurement with magnetic flux sensing for timing detection
How to solve :
  • Integrate miniature planar Rogowski coil (PCB trace, 3-turn, 2mm diameter) adjacent to synchronous rectifier drain pin to sense di/dt transitions with inherent sub-nanosecond response without amplifiers
  • Route coil output to standard comparator (LM393, 1.3μs propagation) comparing integrated flux signal against fixed 50mV threshold—coil self-integration converts GHz bandwidth current spike into slower voltage ramp detectable by low-cost components
  • Calibrate threshold voltage during factory test across input 10-15V and load 0-10A range, store single optimal value in resistor divider (±2% tolerance)—eliminates real-time adaptive circuits while achieving 3-4ns timing accuracy
Expected Effect : Timing precision 3-4ns; component cost +$0.15; no high-speed IC required
Risk Control :
  • PCB trace inductance variation ±15%
  • comparator offset drift with temperature
  • magnetic coupling interference from adjacent traces

Problem Direction 3 :

ImproveConduction loss reduction
VS
ConstraintControl circuit complexity

Inspiration 1 : Cross-domain reference

Application Principle: #22 Blessing in disguise
Cross-domain applicability Assess applicability
Direct AC power converting apparatus
Innovative Solution Refine solution

Self-indicating body diode conduction timing reference for synchronous rectification

Exploit body diode conduction as timing signal
How to solve :
  • Allow controlled 5-10ns body diode conduction at each transition, detect its 0.7V forward drop as zero-crossing reference without external high-speed sensors
  • Implement passive voltage threshold detector using Schottky diode (0.3V threshold) and fast comparator (LMV7219, 7ns delay) to sense body diode turn-on, trigger MOSFET gate within 3ns
  • Use detected body diode event to self-calibrate timing offset in 8-bit lookup table (input voltage 10-15V, load 0-10A grid), update every 100 cycles to track drift, achieving sub-5ns precision with 6-component circuit
Expected Effect : Timing precision <5ns; circuit adds only 6 components vs 30-50 in adaptive sensing; conduction loss reduced 85%; efficiency gain 2-3%
Risk Control :
  • body diode conduction duration control
  • comparator propagation delay variation with temperature
  • lookup table calibration accuracy across operating range
Patsnap Eureka Solution