EE 136 Project PresentationThe Diagonal Half-Bridge Flyback ConverterCircuit Analysis for Half-Bridge Flyback ConverterSchematic Diagram for Half-Bridge Flyback ConverterThe Circuit Diagram When Switches ‘On’ & ‘Off’ and Voltage and Current WaveformSchematic Diagram Voltage and Current waveforms (using Simplorer Software)Advantages of this converterSelf-oscillating flyback converterFrequency variation as a function of load Non-isolated self-oscillating flyback converterCircuit Diagram of non-isolated flyback converterBase drive current waveform of self-oscillating converterSchematic and waveforms using Simplorer softwareIsolated self-oscillating flyback converterNon-isolated self oscillating circuitThe wave form of Q1 and Q2Simulation resultAdvantagesConclusionEE 136 Project Presentation• The Diagonal Half-Bridge Flyback Converter• Non-isolated Self-Oscillating Flyback Converter with Primary Current-Mode Control• Isolated Self-Oscillating Flyback Converter with Primary Current-Mode Control• Presented By: Latt M. Tee Naw Sandar ShweThe Diagonal Half-Bridge Flyback Converter– This converter is suitable for power FETs operation– Same design procedure applies as a single-ended flyback converterCircuit Analysis for Half-Bridge Flyback Converter• Switches is driven by control circuit, both “on” and “off” together• Flyback action takes place during “off” period• Cross-connected diodes D1 and D2 return excess flyback energy to supply lines• D1 and D2 eliminates the need of an energy recovery winding or large snubbing components.Schematic Diagram for Half-Bridge Flyback ConverterThe Circuit Diagram When Switches ‘On’ & ‘Off’ and Voltage and Current WaveformD1D2D8D4D5D6C1C2TFR1P2W1C3 R1V1S1S2D1D2D8D4D5D6C1C2TFR1P2W1D3C3 R1V1TRAPEZ1TRIANG1Schematic DiagramVoltage and Current waveforms (using Simplorer Software)S1S2D1D2D8D4D5D6C1C2TFR1P2W 1D3C3 R1V1TRAPEZ1TRIANG1D6.I [A] 1e-036-1.3e-018D5.I [A] 1.3e-018-1e-036TFR1P2W1.V1 [V] 1p-3pTFR1P2W1.I1 [A] 2.9e-017-1.2e-018t [s] 0 4n0.5n 1n 1.5n 2n 2.5n 3n 3.5nAdvantages of this converter•Using the diodes D1 and D2 is good for over-voltage stress. •Flyback action returns the stored energy to the supply line.•Do not need bifilar-wound energy recovery winding •Reduce the cost and eliminate unreliable source.Self-oscillating flyback converter•Low component count without loss of performance•Widely used in low power applications such as computers, video display terminals and so onFrequency variation as a function of loadNon-isolated self-oscillating flyback converter•Type C operation•Variable ‘on’ time, ‘off’ time, and repetition rate (freq.)•Has a more desirable characteristicCircuit Diagram of non-isolated flyback converterBase drive current waveform of self-oscillating converterSchematic and waveforms using Simplorer softwareR1R2R3R7R5R6R 4R8R9R10C1C2E1D1BJT1BJT2TWTTWT1D2C3+-OPV51TFR 1P11D3D4C4E2BJT1.I [A] t [s] 2.8m00.5m1m1.5m2m0 0.4m50u 0.1m 0.15m 0.2m 0.25m 0.3mR2.I [A] t [s] 0-2.8m-2m-1.5m-1m-0.5m0 0.4m50u 0.1m 0.15m 0.2m 0.25m 0.3mIsolated self-oscillating flyback converter•The input and output voltage does not depend on each other•Optocoupler is used as a feedback loop•Transistor Q2 and R4 control the current-mode•Input voltage +300 V DC and output voltage +12V is applied to the circuit for self-oscillatingNon-isolated self oscillating circuitThe wave form of Q1 and Q2•Q1 Ic increase Ie increase•Vbe 0.6V Q2 turn onSimulation resultC1C2C3C4C5C6D1D2R1D3Diod e601L1R2R3R4R5R6R7R8TWTTWT1Diod e602R9D4R11R12E2R10C7R5.V [V] t [s] 0.1k-0.25k0-0.15k-0.1k-500 9.5m1m 2m 3m 4m 5m 6m 7m 8mNPN61NPN63NPN62THY41NPN61.VBE t [s] 4k01k1.5k2k2.5k3k0 9.5m1m 2m 3m 4m 5m 6m 7mNPN63.IC t [s] 0.3-50m50m0.10.150.20 9.5m1m 3m 5m 7mNPN63.I_B t [s] 0.14-20m20m40m60m80m0.10 9.5m1m 3m 5m 7mAdvantages•The system as if the primary is a high-impedance current source.•Results in a first order transfer function.•The control circuit may have high frequency response.•Line ripple rejection and stability improved.•Primary current limiting is provided.Conclusion•Low cost•Fewer components need•Widely used in low power