Including Reverse Leakage in a Schottky Rectifier Thermal Review

A Schottky rectifier selected for low forward voltage can still dissipate meaningful power while reverse biased. Leakage generally changes with voltage and temperature, so a forward-loss calculation alone may miss the limiting condition. Review both parts of the operating cycle.

Read the leakage information

Vishay’s Schottky design guidance explains the tradeoff between forward drop and reverse leakage and describes thermal feedback when increasing temperature creates additional leakage loss. Its historical product examples are not universal temperature limits for current devices.

Use the exact rectifier data sheet for leakage versus reverse voltage and temperature, including guaranteed values where available. Keep typical curves separate from limits used to justify the design. Record the operating duty cycle and the time spent reverse biased.

Calculate both loss contributions

Estimate forward-conduction loss using the actual current waveform and applicable forward-voltage behavior. Estimate reverse loss from reverse voltage, leakage and the reverse-biased fraction of the cycle. Include other relevant switching contributions using the supplier’s recommended method.

For illustration, 20 V multiplied by 2 mA is 40 mW while that reverse condition is present. If leakage rises significantly as the device warms, the original room-temperature estimate no longer describes the final operating state. The example is arithmetic, not a leakage specification.

Check thermal consistency

Evaluate whether the estimated dissipation and board thermal path lead to a temperature consistent with the electrical values used in the calculation. Iterate the estimate when necessary or use an appropriate electrothermal model. Include enclosure temperature and nearby heat sources.

Do not assume that a low forward-drop candidate always produces the lowest total loss. Compare candidates using the actual forward and reverse operating intervals. A difference that is small during room-temperature conduction can become important during warm reverse-biased operation.

Verify the relevant states

Measure current and temperature during steady operation and during product states that leave the diode reverse biased for long intervals. Use a suitable controlled setup and stop before exceeding the defined operating limits. Identify whether the circuit reaches a stable thermal condition.

Keep the board mounting, ambient conditions, leakage assumptions and measured behavior with the selected component. Recheck the review after increasing reverse voltage, changing duty cycle or reducing available copper area. A defensible approval explains the thermal behavior of the entire cycle, rather than using a room-temperature forward-voltage number or a successful short-duration bench run as the only evidence of margin. Record how the component temperature was estimated and the uncertainty of that method.