| 摘要 |
An isolated flyback converter having a temperature compensation (TC) circuit (30) uses primary side sensing and an output diode (D), the output diode having a variable voltage drop related to its temperature. A feedback voltage V FB , proportional to the output voltage V OUT , in a feedback loop is compared to a fixed reference voltage V REF for setting a duty cycle of a power switch, wherein V FB is caused to approximately equal V REF . The TC circuit has a voltage source (32) configured to generate a proportional-to-absolute-temperature voltage V PTAT , wherein V PTAT is at approximately V REF at a calibration temperature To and rises as a temperature exceeds To. The voltage source is connected to the V FB node via a TC resistor R TC , so that at To no current flows through R TC . Therefore, the selection of the optimal R TC does not affect the selection of a scaling resistance for generating V FB . The current through R TC at elevated temperatures compensates V OUT . |
