These circuit diagrams show the switching operations of the boost transistor (simplified as an ideal switch in the diagrams) and the boost diode. The upper diagram shows that when the transistor switch (usually a MOSFET) is off, the boost diode is forward biased. Energy stored in the boost inductor will be released through a boost diode to the output load. The lower diagram illustrates when the transistor is on, the boost diode is reverse biased. The reverse recovery current presented in silicon diodes will find the path to flow through the main switching device, as shown in the diagram. Higher reverse recovery current will not only increase the turn-off switching loss in the boost diode, but also the transistor turn-on loss. It will cause both device case temperatures to increase.