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| You are here: VMI Home Page > Diodes > High Voltage Diodes Appendix B: Thermal Analysis Contact Us |
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On A PC Board
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Controlling junction temperature is key to reliable design in any semiconductor
package, but high voltage diodes present unique problems that must be addressed. In
high voltage diodes, heat is generated by: Forward Voltage Reverse Leakage Current Reverse Recovery Losses Each of these factors change differently with temperature and must be considered carefully over the intended operating temperature range. The following examples depict the relative change in heat sources in a typical example: Diode Losses vs. Temperature: Diode = 1N6515 TRR= 70ns PIV = 3000V VF = 4.0V @ 0.5A Circuit Conditions: Operating Frequency = 50kHz Voltage Rise Time = 100ns Average Rectified Current = 0.5A per diode Reverse Voltage = 2000V Peak 
In this example, the junction temperature would exceed +150°C if the package thermal impedance exceeds 6.25 °C/watt. TOTAL heat source consideration must be made. The deceptive difference in recovery losses in high voltage applications is due primarily to the high voltage bias applied while the diode is recovering from forward bias to a blocking mode. The problem presented can be solved by: a) decreasing forward voltage losses b) decreasing the reverse recovery losses c) improving the thermal impedance d) operating over a reduced temperature range
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