Optimization

Circuit Optimization Strategies 

 This page covers practical strategies for optimizing your VIC circuit design using the calculator. Learn how to achieve specific goals like maximizing Q, hitting a target frequency, or optimizing voltage magnification. 

 Optimization Goals 

 Different applications may prioritize different characteristics: 

 Goal 

 Optimize For 

 Trade-offs 

 Maximum Voltage 

 High Q, matched resonance 

 Narrower bandwidth, critical tuning 

 Stable Operation 

 Moderate Q, wide bandwidth 

 Lower peak voltage 

 Frequency Flexibility 

 Lower Q, broader response 

 Reduced magnification 

 Energy Efficiency 

 Minimize losses (DCR, R sol ) 

 May require larger components 

 Strategy 1: Maximizing Q Factor 

 Q determines voltage magnification and selectivity. To maximize Q: 

 Reduce Choke DCR: 

 

 

 Use larger wire gauge (lower AWG number) 

 Use copper instead of aluminum 

 Minimize wire length (fewer turns with higher-μ core) 

 Consider Litz wire for high frequencies 

 

 

 Reduce Solution Resistance: 

 

 

 Increase water conductivity slightly (add small amount of electrolyte) 

 Increase electrode area 

 Decrease electrode gap (but watch capacitance change) 

 Ensure good electrode contact 

 

 

 Increase L or Decrease C: 

 

 Higher L/C ratio raises Z₀ = √(L/C) 

 Q = Z₀/R, so higher Z₀ means higher Q 

 Must maintain same f₀ = 1/(2π√LC) 

 

 Q Factor Relationships: 

 Q = 2πf₀L/R = Z₀/R = √(L/C)/R 

 To double Q: halve R, or quadruple L (while quartering C to maintain f₀) 

 Strategy 2: Hitting Target Frequency 

 When you need a specific resonant frequency: 

 Approach A: Fixed L, Adjust C 

 

 

 Design or select choke for desired L 

 Calculate required C: C = 1/(4π²f₀²L) 

 If C wfc ≠ required C:

 Add parallel capacitor if C wfc is too low 

 Modify electrode geometry if adjustment is large 

 

 

 

 Approach B: Fixed C, Adjust L 

 

 

 Measure or calculate WFC capacitance 

 Calculate required L: L = 1/(4π²f₀²C) 

 Design choke for that inductance 

 

 

 Approach C: Adjust Both 

 

 Start with practical component ranges 

 Use calculator to explore L/C combinations 

 Choose combination that also optimizes Q 

 

 Fine-Tuning Frequency 

 Adjustment 

 Effect on f₀ 

 Typical Range 

 Add parallel capacitor 

 Decreases f₀ 

 1-50 nF typical 

 Adjust core gap (if gapped) 

 Changes L → changes f₀ 

 ±20% L adjustment 

 Add/remove turns 

 Changes L significantly 

 L ∝ N² 

 Change water level 

 Changes C → changes f₀ 

 Proportional to area 

 Strategy 3: Matching Primary to Secondary 

 For maximum energy transfer, align primary and secondary resonances: 

 Exact Match (f₀ pri = f₀ sec ): 

 

 

 Maximum voltage transfer at resonance 

 Narrow combined response 

 Requires precise tuning 

 

 

 Slight Offset (5-10% difference): 

 

 

 Broader frequency response 

 More tolerant of drift 

 Slightly reduced peak transfer 

 

 

 Calculator Approach: 

 

 Design secondary (L2 + WFC) first—this is usually more constrained 

 Calculate secondary f₀ 

 Select C1 to tune primary to match: C1 = 1/(4π²f₀²L1) 

 Verify with simulation 

 

 Strategy 4: Optimizing for Available Components 

 When working with existing components: 

 Step 1: Characterize What You Have 

 

 

 Measure L of available chokes 

 Measure C of your WFC 

 Note DCR values 

 

 

 Step 2: Calculate Natural Resonance 

 f₀ = 1/(2π√LC) 

 This is where your circuit wants to resonate. 

 Step 3: Evaluate Performance 

 

 

 Is f₀ in your driver's range? 

 Is Q acceptable at this frequency? 

 Are there SRF issues? 

 

 

 Step 4: Adjust as Needed 

 

 Add tuning capacitor if f₀ is too high 

 Consider different choke if f₀ is way off 

 Accept the natural f₀ if performance is good 

 

 Sensitivity Analysis 

 Understanding how sensitive your design is to variations: 

 Parameter Change 

 Effect on f₀ 

 Effect on Q 

 L +10% 

 f₀ -5% 

 Q +5% 

 C +10% 

 f₀ -5% 

 Q -5% 

 R +10% 

 No change 

 Q -10% 

 Temperature +10°C 

 f₀ +2% (due to ε r drop) 

 Q +5% (R sol drops) 

 Common Optimization Mistakes 

 ❌ Chasing Extreme Q 

 Very high Q makes the circuit sensitive to drift and hard to tune. Q of 50-100 is often more practical than Q > 200. 

 ❌ Ignoring SRF 

 A design that works on paper fails if operating frequency is too close to SRF. Always check this! 

 ❌ Forgetting Water Resistance 

 Solution resistance often dominates losses. Pure distilled water has higher resistance than you might expect. 

 ❌ Not Accounting for Parasitics 

 Real circuits have stray inductance and capacitance. Leave margin for these effects. 

 ❌ Over-constraining the Design 

 If you fix too many parameters, you may have no degrees of freedom for optimization. 

 Optimization Checklist 

 

 ☐ Define your primary optimization goal 

 ☐ Identify fixed constraints (available components, frequency range) 

 ☐ Calculate baseline performance 

 ☐ Identify largest loss contributor (DCR vs R sol ) 

 ☐ Make targeted improvements to dominant loss 

 ☐ Verify SRF is >3× operating frequency 

 ☐ Check that primary/secondary are reasonably matched 

 ☐ Run simulation to verify improvements 

 ☐ Consider sensitivity to variations 

 ☐ Document final design parameters 

 

 Remember: Optimization is iterative. The calculator makes it easy to try variations quickly. Don't expect to find the optimal design on the first try—explore the design space! 

 Next: Interpreting Calculation Results →