Flyback Converters v4
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Transcript of Flyback Converters v4
Development of SiC-Based PEBB 1000
May 1, 2023
PWM DC-DC Flyback Converters
Pedro Campos FernandesJun Wang
May 1, 2023 Development of SiC-Based PEBB 1000 2
1. One-Switch Flyback Converter
Advantages Simplicity: fewer semiconductor and magnetic components Low cost
Disadvantages Resonance caused by the leakage inductance and the device junction capacitances
High-frequency ringing and EMI
May 1, 2023 Development of SiC-Based PEBB 1000 3
2. Ideal One-Switch Flyback Converter
Circuit components:
Q: Ideal MOSFET Switch D: Ideal Rectifier Diode C: Output Capacitance RL: Load Resistance Vin: Input Voltage Source I1: Input Current (primary) LM: Magnetizing Inductance IM: Magnetizing Current I2: Diode Current (secondary) T: Ideal Flyback Transformer
May 1, 2023 Development of SiC-Based PEBB 1000 4
2. Ideal One-Switch Flyback Converter Simulation model:
May 1, 2023 5
2.1. CCM Operation2.1.1. First Stage: DTS
Q is ON D is OFF Energy from the DC sourceis stored in LM
Development of SiC-Based PEBB 1000
May 1, 2023 Development of SiC-Based PEBB 1000 6
2.1. CCM Operation2.1.2. Second Stage: (1-D)TS
Q is OFF D is ON Transformer voltage reversesforward-biasing the rectifier diodeand delivering energy to the output
May 1, 2023 Development of SiC-Based PEBB 1000 7
3. Non-Ideal One-Switch Flyback Converter
Circuit components:
Q: MOSFET Switch D: Rectifier Diode C: Output Capacitance RL: Load Resistance Vin: Input Voltage Source I1: Input Current (primary) LM: Magnetizing Inductance IM: Magnetizing Current I2: Diode Current (secondary) T: Flyback Transformer CJ: Diode Junction Capacitance CDS: Drain-Source Capacitance Lleak: Leakage Inductance
May 1, 2023 Development of SiC-Based PEBB 1000 8
3. Non-Ideal One-Switch Flyback Converter Simulation model:
May 1, 2023 9
3.1. CCM Operation3.1.1. First Stage: DTS
Subinterval 1: Q is switching from OFF to ON D is switching from ON to OFF Switch transient ringing
Development of SiC-Based PEBB 1000
May 1, 2023 10
3.1. CCM Operation3.1.1. First Stage: DTS
Subinterval 2: Q is effectively ON D is effectively OFF No switch transient ringing
Development of SiC-Based PEBB 1000
May 1, 2023 11
3.1. CCM Operation3.1.2. Second Stage: (1-D)TS
Subinterval 3: Q is switching from ON to OFF D is switching from OFF to ON Switch transient ringing
Development of SiC-Based PEBB 1000
May 1, 2023 12
3.1. CCM Operation3.1.2. Second Stage: (1-D)TS
Subinterval 4: Q is effectively OFF D is effectively ON No switch transient ringing
Development of SiC-Based PEBB 1000
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3.2. Ideal Case vs. Parasitic Case
May 1, 2023 Development of SiC-Based PEBB 1000 14
3.2. Ideal Case vs. Parasitic Case
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4. Two-Switch Flyback Converter
Advantages Maximum switch voltage is clamped to the DC input voltage Vin Leakage inductance energy is also clamped and recycled back to the DC
input source (improve efficiency) Reduced switching and conduction losses
May 1, 2023 Development of SiC-Based PEBB 1000 16
5. Non-Ideal Two-Switch Flyback Converter
Circuit components: Q1,2: Symmetrical MOSFET Switches D1,2: Symmetrical Clamping Diodes D: Rectifier Diode C: Output Capacitance RL: Load Resistance Vin: Input Voltage Source I1: Input Current (primary) LM: Magnetizing Inductance IM: Magnetizing Current I2: Diode Current (secondary) T: Flyback Transformer CJ: Diode Junction Capacitance CDS1,2: Drain-Source Capacitances Lleak: Leakage Inductance
May 1, 2023 Development of SiC-Based PEBB 1000 17
5. Non-Ideal Two-Switch Flyback Converter Simulation model:
May 1, 2023 18
5.1. CCM Operation5.1.1. First Stage: DTS
Subinterval 1: Q1, Q2 are switching from OFF to ON D is switching from ON to OFF D1, D2 are OFF Switch transient ringing
Development of SiC-Based PEBB 1000
May 1, 2023 19
5.1. CCM Operation5.1.1. First Stage: DTS
Subinterval 2: Q1, Q2 are effectively ON D is effectively OFF D1, D2 are OFF No transient ringing
Development of SiC-Based PEBB 1000
May 1, 2023 20
5.1. CCM Operation5.1.2. Second Stage: (1-D)TS
Subinterval 3: Q1, Q2 are switching from ON to OFF D is switching from OFF to ON D1, D2 are OFF Voltage spike
Development of SiC-Based PEBB 1000
May 1, 2023 21
5.1. CCM Operation5.1.2. Second Stage: (1-D)TS
Subinterval 4: Q1, Q2 are switching from ON to OFF D is effectively ON D1, D2 are ON Switch voltages VDS1, VDS2 are clamped to Vin
Development of SiC-Based PEBB 1000
May 1, 2023 22
5.1. CCM Operation5.1.2. First Stage: DTS
Subinterval 5: Q1, Q2 are switching from ON to OFF D is ON D1, D2 are switching from ON to OFF Switch transient ringing
Development of SiC-Based PEBB 1000
May 1, 2023 23
5.1. CCM Operation5.1.2. First Stage: DTS
Subinterval 6 Q1, Q2 are effectively OFF D is ON D1, D2 are effectively OFF No transient ringing
Development of SiC-Based PEBB 1000
May 1, 2023 Development of SiC-Based PEBB 1000 24
5.2. One-Switch vs. Two-Switch
May 1, 2023 Development of SiC-Based PEBB 1000 25
5.2. One-Switch x Two-Switch
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5.3. Component Mismatches
Real applications do not provide perfect symmetry between junction capacitances and gate driver signals
There are mismatches between these variables and they lead to different behaviors during the converter operation
May 1, 2023 Development of SiC-Based PEBB 1000 27
5.3. Component Mismatches
Two types of mismatch will be covered:
20% mismatch on drain-source capacitance of the low side MOSFET switch Q2 given the high side MOSFET switch Q1 as reference
5% delay (given the period as reference) on the gate driver of the low side MOSFET switch Q2
May 1, 2023 Development of SiC-Based PEBB 1000 28
5.3. Component Mismatches5.3.1. Capacitance Mismatch CDS1 = 120 pF and CDS2 = 144 pF
Q1 is clamped earlier than Q2, i.e.,D1 starts conducting earlier than D2 Q1, Q2 voltages reach different steady values after the ringing dies
May 1, 2023 Development of SiC-Based PEBB 1000 29
5.3. Component Mismatches5.3.2. Gate Drive Delay Mismatch DelayQ1 = 0 s and DelayQ2 = 0.17 us
Q2 turns ON later, so Q1 will be clamped earlier Q1 turns ON earlier, leading to another clamping action during the delayed turn ONof Q2
May 1, 2023 Development of SiC-Based PEBB 1000 30
5.3. Component Mismatches5.3.3. Merged Mismatch
May 1, 2023 Development of SiC-Based PEBB 1000 31
5.3. Component Mismatches
Possible Solutions
Design an integrated solution with complete control circuit and gate drive for both high side (Q1) and low side (Q2) switches
Work with safety margins so that the circuit can still present good performance for a certain percentage of mismatch
May 1, 2023 Development of SiC-Based PEBB 1000 32
6. Power Losses on Flyback Converters
Design considerations: Zero winding resistances (rprimary = rsecondary = 0) Zero leakage resistance The MOSFET switches and clamping diodes are considered
symmetrical to each other Two-Switch topology - switches model: IRF510
100 V, 5 A, ron,max = 0.85 Ω and CDS = 60 pF One-Switch topology - switch model: IRF840
500 V, 8 A, ron,max = 0.54 Ω and CDS = 120 pF Rectifier Diode model: MBR10100 100 V, 10 A, VF = 0.65 V and rF = 20 mΩ with CJ = 200 pF Clamping Diodes model: MBR10100
100 V, 10 A, VF = 0.65 V and rF = 20 mΩ with CJ = 0 F
May 1, 2023 Development of SiC-Based PEBB 1000 33
6. Power Losses on Flyback Converters
Losses presented by the design:
Conduction Losses
Forward Voltage Losses
Switching Losses
May 1, 2023 Development of SiC-Based PEBB 1000 34
6.1. Conduction Losses6.1.1. MOSFET Switches Q1, Q2 Since Q1, Q2 are symmetrical to each other, conduction losses will be given by:
6.1.2. Rectifier Diode D3
6.1.3. Clamping Diodes D1, D2 Since Q1, Q2 are symmetrical to each other, conduction losses will be given by:
And
May 1, 2023 Development of SiC-Based PEBB 1000 35
6.2. Forward Voltage Losses6.2.1. Rectifier Diode D3 The average power dissipated by the forward voltage across the ON stage rectifier
diode is given by:
6.2.2. Clamping Diodes D1, D2 The average power dissipated by the forward voltage across the ON stage
clamping diodes is given by:
And
May 1, 2023 Development of SiC-Based PEBB 1000 36
6.3. Switching Losses
Switching Losses on the MOSFET switches can be obtained by the simplified formulation presented on [4]:
And
May 1, 2023 Development of SiC-Based PEBB 1000 37
6.4. Total Power Loss
The total power loss of the circuit is given by:
With
May 1, 2023 Development of SiC-Based PEBB 1000 38
6.5. Results
Initial Considerations
The simulation time covered 0 to 0.05s
The samples were saved on a .mat file and a reused on a MATLAB script in order to compute the losses
The RMS and average currents were computed considering one switching cycle only at steady state
May 1, 2023 Development of SiC-Based PEBB 1000 39
6.5. Results
Condcution Losses Forward Voltage Losses
Switching Losses Total Losses Efficiency0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
10.
064
0.35
3 0.43
3
0.84
9
0.87
4
0.07
4
0.35
5
0.04
2
0.47
0
0.92
4
Power Losses at CCM (W)
One-Switch Two-Switch
May 1, 2023 Development of SiC-Based PEBB 1000 40
6.5. Results
Comparison of the performance of the converters in CCM:
The conduction losses slightly increased due to the presence of more components on the two-switch topology
The switching losses were drastically reduced
The efficiency increased 5 %
May 1, 2023 Development of SiC-Based PEBB 1000 41
6.5. Results
Conduction Losses Forward Voltage Losses Switching Losses Total Losses Efficency 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
10.
064
0.35
3
0.43
3
0.84
9
0.87
4
0.08
4
0.36
7
0.14
0
0.59
2
0.91
2
0.07
4
0.35
5
0.04
2
0.47
0
0.92
4
0.10
2
0.36
5
0.01
1
0.47
7
0.92
7
Power Losses at CCM and BCM (W)
One-Switch CCM One-Switch BCM Two-Switch CCM Two-Switch BCM
May 1, 2023 Development of SiC-Based PEBB 1000 42
6.5. Results
Comparison of the performance of the converters in CCM vs. BCM:
Higher conduction losses at BCM
Lower switching losses for both topologies at BCM
Higher efficiency for both topologies at BCM
May 1, 2023 Development of SiC-Based PEBB 1000 43
7. Conclusion
Does the Two-Switch Flyback Converter present a better performance when compared to the One-Switch topology?
Voltage across the MOSFET switches is clamped to Vin (no high-voltage spikes)
Lower ringing effect
Lower switching losses
Higher efficiency
May 1, 2023 Development of SiC-Based PEBB 1000 44
8. References
[1] “Improving the Performance of Traditional Flyback-Topology With Two-Switch –Approach”, J. Pesonen; Texas Instruments
[2] “Understand Two-Switch Forward/Flyback Converters”, Y. Xi, R. Bell; National Semiconductor
[3] “Hard-Switching and Soft-Switching Two-Switch Flyback PWM DC-DC Converters and Winding Loss due to Harmonics in High-Frequency Transformers”, D. M. Bellur, Wright State University
[4] “Two-Switch Flyback PWM DC-DC Converter in Continuous-Conduction Mode”, D. M. Bellur, M. K. Kazimierczuk, Wright State University
[5] “Fundamentals of Power Electronics”, R. W. Erickson, D. Maksimovic, University of Colorado Boulder
[6] “Characterization and Modeling of High-Switching-Speed Behavior of SiC Active Devices”, Zheng Chen; Virginia Polytechnic Institute and State University
[7] “AN-9010 MOSFET Basics”, Fairchild Semiconductor
[8] “Analysis of SiC MOSFETs under Hard and Soft-Switching”, M. R. Ahmed, R. Todd, A. J. Forsyth, The University of Manchester, UK
[9] “Power Electronics - A First Course”, N. Mohan, University of Minnesota
[10] “Development of an Isolated Flyback Converter Employing Boundary-Mode Operation and Magnetic Flux Sensing Feedback”, M. V. Kenia, Massachusetts Institute of Technology