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CURRENT_FOLDBACK_PROTECTION

2016-09-21 22:15  
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CURRENT_FOLDBACK_PROTECTION
MPC1000 hybrid regulator provides regulated output of 5 V at 5 A from 14-V input. Values of components are based on foldback current of 6 A and short-circuit current of 2 A; this ensures that dissipation of regulator on short-circuit is Iess than dissipation at rated Ioad. Short-circuit current is controlled by diode drop across Ra and foldback current by drop across R2 Article gives design equations and procedure for obtaining other output voltages. Circuit also serves to limit starting surges into capacitive load, and reduces heatsink size and transistor ratings. ReturningR3 to pin 2 of MPC1000 instead of pin 3 gives lower short-circuit current, improves ef-ficiency, and reduces heat generation. Foldback protection is not suitable for variable-output supplies because foldback current is propor-tional to output voltage.-R. L. Haver, Use Cur-rent Foldback to Protect Your Voltage Regula-tor, EDNMagazine, Aug. 20, 1974, p 69-72.