Introduction

This interactive simulation allows you to explore the behavior of a ZETA converter, a DC-DC power converter that can step up or step down voltage with non-inverted output polarity. The ZETA converter provides continuous input current and excellent input-output isolation with unique energy transfer characteristics.

Key Characteristics

• Non-Inverted Output: Output voltage has same polarity as input
• Continuous Input Current: Input current is continuous, reducing EMI
• Buck-Boost Operation: Can step up or step down input voltage
• Voltage Gain: Vout/Vin = D/(1-D), where D is duty cycle
• Input-Output Isolation: Ground isolation between input and output
• Unique Topology: Coupling capacitor in series with load circuit

Circuit Components

• Input Inductor (L1): Provides continuous input current
• Output Inductor (L2): Stores energy and smooths output current
• Coupling Capacitor (C1): Energy transfer element (in series with load)
• Output Capacitor (C2): Filters output voltage ripple
• MOSFET Switch: Controls energy storage and transfer
• Rectifier Diode: Provides current path during energy transfer

Operation Principles

Switch ON (Duty Cycle):

• L1 stores energy from input source
• L2 and C1 supply energy to the load
• C1 discharges through the load and L2
• Diode is reverse biased

Switch OFF:

• L1 releases energy through the diode
• L1 charges C1 and supplies L2
• Energy transfers from L1 to output circuit
• C2 maintains output voltage

Design Equations

• Output Voltage: Vout = Vin × D/(1-D)
• Voltage Gain: M = Vout/Vin = D/(1-D)
• Input Current: Iin = Iout × D/(1-D)
• Critical Inductance: Lcrit = R(1-D)²/(2f)
• Coupling Capacitor Voltage: Vc1 = Vout

Advantages

• Continuous input current (low input ripple)
• Non-inverted output polarity
• Input-output ground isolation
• Wide input voltage range capability
• Good EMI characteristics
• Can operate in buck or boost mode
• Lower component stress compared to some topologies

Disadvantages

• More complex than basic buck or boost converters
• Requires two inductors and two capacitors
• Coupling capacitor must handle full output current
• Right-half-plane zero in boost mode
• Higher component count increases cost
• More complex control requirements

Applications

• Battery chargers requiring isolation
• DC motor drives
• Solar panel power optimizers
• Telecommunications power supplies
• Automotive electronics
• Industrial power conversion
• UPS systems

ZETA vs Other Converters

• vs SEPIC: ZETA has coupling capacitor in series with load, different energy transfer
• vs Cuk: ZETA has non-inverted output, different topology
• vs Buck-Boost: ZETA has continuous input current
• vs Boost: ZETA provides input-output isolation

Simulation Tips

• Start with duty cycle around 50% for unity gain
• Observe continuous input current waveform
• Monitor coupling capacitor current (carries full output current)
• Check inductor current discontinuity in DCM
• Note the series arrangement of C1 with load
• Consider right-half-plane zero effects in boost mode
• Verify ground isolation between input and output