Table:
text: Switched-mode power supply
Types
Isolated topologies
Type_ Power_W_ Relative_cost Input_range_V_ Energy_storage Features_
Flyback 0–250 1.0 5–600 Mutual Inductors Isolated form of the buck-boost converter.
Ringing choke converter (RCC) 0–150 1.0 5–600 Transformer Low-cost self-oscillating flyback variant.
Half-forward 0–250 1.2 5–500 Inductor 
Forward 100-200  60–200 Inductor Isolated form of buck converter
Resonant forward 0–60 1.0 60–400 Inductor and capacitor Single rail input, unregulated output, high efficiency, low EMI.
Push-pull 100–1,000 1.75 50–1,000 Inductor 
Half-bridge 0–2,000 1.9 50–1,000 Inductor 
Full-bridge 400–5,000 >2.0 50–1,000 Inductor Very efficient use of transformer, used for highest powers.
Resonant, zero voltage switched >1,000 >2.0  Inductor and capacitor 
Isolated Ćuk    Two capacitors and two inductors

Question: What is the energy storage of the half-bridge in a switching power supply is not a transformer, but what ?