This is the DC voltage doubler circuit which build based National IC LM2586. The circuit will doubling the input voltage of 12VDC to become 24VDC. Heatsink is required for this circuit.
The LM2586 is a monolithic integrated circuits specifically designed for flyback, step-up (boost), and forward converter applications. The device is available in 4 different output voltage versions: 3.3V, 5.0V, 12V, and adjustable.
Download LM2586 datasheet for this DC voltage doubler circuit reference.