Advanced topologies Half-bridge, Full-bridge, Push-Pull, Cuk, SEPIC - PDF document

Mor M. Peretz, Switch-Mode Power Supplies [6-1] Advanced topologies Half-bridge, Full-bridge, Push-Pull, C’uk, SEPIC • C’uk • Sepic • Half-bridge • Symmetrical operation • Double power supply • Principle of operation , definition of D • Using bus capacitors – capacitive voltage division? • The concept of split bus capacitor • Component stress • Asymmetrical operation • Full-bridge • Operation • Stress • Reset • Push-pull [6-2] Mor M. Peretz, Switch-Mode Power Supplies Types of PWM converters C’uk and SEPIC C D Vo L1 Vin Co Ro L2 Q C’uk SEPIC V D V D o  o     V 1 D V 1 D in in 1

Mor M. Peretz, Switch-Mode Power Supplies [6-3] C’uk Converter L 1 C 1 L 2 V out Voltage V in R D C 2 V C1 V 2 V 1 of C 1  constant S OFF ON L 2 L 1 L 2 L 1 V out V out V in V in R R C 2 C 2 C 1 C 1     V V (buck) V V D 1 o o c 1 on      V ( V V ) D V V o in o on 2 in V D   o on   V V V V D c 1 in o in off [6-4] Mor M. Peretz, Switch-Mode Power Supplies C’uk with isolation L 2 L 1 C 1a C 1b V out V in C 2 R V 2 D S 1:n  Any polarity  Any voltage ratio V D   o on n V D in off 2

Mor M. Peretz, Switch-Mode Power Supplies [6-5] C’uk Converter Inductors on the same core L 1 C 1 L 2 V out V in R D C 2 V C1 V 2 V 1 S Can be done only if the voltage on the windings are equal [6-6] Mor M. Peretz, Switch-Mode Power Supplies C’uk advnatages and disadvantages Advantages  Continues input and output currents  Single switch  Step-up and step-down Disadvantages  Two inductors  Extra capacitor (of high rms current)  Difficult to stabilize V  V  High voltage on switch in out 3

Mor M. Peretz, Switch-Mode Power Supplies [6-7] SEPIC Converter L 1 C 1 D V x V out V in C 2 S L 2 R ON OFF L 1 C 1 C 1 L 1 V x V x D V in V in C 2 C 2 S S L 2 L 2 R R       V V D V D 0 V 0 x o off in on L 1  V D V 0  L 2 o on V D  V V in off C 1 in [6-8] Mor M. Peretz, Switch-Mode Power Supplies Half-bridge Vx Ton Q1 Ts HB, Ton Q2 symmetrical operation V n D 1 T1  o V n 2 in t Vx  on D T 2 s 4

Mor M. Peretz, Switch-Mode Power Supplies [6-9] Half-bridge What is the transformer voltage at off time Vx Ton Q1 Ts Ton Q2 T1 Vx [6-10] Mor M. Peretz, Switch-Mode Power Supplies Types of PWM converters HB –Capacitors to replace supplies +Vin Q1 C1 Vx n1 Q2 C2 5

Mor M. Peretz, Switch-Mode Power Supplies [6-11] Types of PWM converters HB -Concept of split bus capacitors +Vin Q1 C1 Vx n1 Q2 C2 [6-12] Mor M. Peretz, Switch-Mode Power Supplies Types of PWM converters Asymmetrical operation – synchronous rectifier +Vin Q1 C1 Vx n1 Q2 C2 Motivation to asymmetrical operation: Spikes and oscillations at the mid point an off time 6

Mor M. Peretz, Switch-Mode Power Supplies [6-13] Full-bridge V n D 1  o 2 2 V n in [6-14] Mor M. Peretz, Switch-Mode Power Supplies Push-pull V n D 1  Ton o 2 2 Q1 V n Ts in Ton Q2 7

Mor M. Peretz, Switch-Mode Power Supplies [6-15] Reset of Forward, HB, FB  Forward - auxiliary winding  HB,FB - Natural L V x V C V o C R C 1 S 1 T n V 2 T C 2 V 1 S 2 V C V T S 1 2 2 t on t T S V C t on  2 2 [6-16] Mor M. Peretz, Switch-Mode Power Supplies Forward, HB, FB, PP Switch Utilization I L ripple for same L Important consideration: V s (off), I s (on)  I  Forward: Assumption:  I  Same input and output power  HB, FB, PP: 2  Same input voltage I S I FW FORWARD t off t on t    V S D V 1 on   C   D off t 8

Mor M. Peretz, Switch-Mode Power Supplies [6-17] I S I HB =2I FW t off Waveforms t on t HB V S V C t I S I FB =I FW t off t on t FB V S V C t [6-18] Mor M. Peretz, Switch-Mode Power Supplies Types of PWM converters Comparison chart Converter Sw current Sw voltage Buck Io Vin Boost Io(Don/Doff) Vo Buck-Boost Io(Don/Doff) Vin+Vo C’uk Iin+Io Vin+Vo SEPIC Iin+Io Vin+Vo Forward Io*(n2/n1) Vin+Vrst Flyback Io*(n2/n1)(Don/Doff) Vin+Vo*(n1/n2) HB 2Io *(n2/n1) Vin FB Io *(n2/n1) Vin/2 PP Io *(n2/n1) 2Vin 9

Mor M. Peretz, Switch-Mode Power Supplies [6-19] [6-20] Mor M. Peretz, Switch-Mode Power Supplies 10

Mor M. Peretz, Switch-Mode Power Supplies [6-21] [6-22] Mor M. Peretz, Switch-Mode Power Supplies 11

Mor M. Peretz, Switch-Mode Power Supplies [5-23] 12