| 摘要 |
An isolated flyback converter having temperature compensation (TC) uses primary side sensing and an output diode, the output diode having a variable voltage drop related to its temperature. A feedback voltage VFB, proportional to the output voltage VOUT, in a feedback loop is compared to a fixed reference voltage VREF for setting a duty cycle of a power switch, wherein VFB is caused to approximately equal VREF. A TC circuit has a voltage source configured to generate a proportional-to-absolute-temperature voltage VPTAT, wherein VPTAT is at approximately VREF at a calibration temperature T0 and rises as a temperature exceeds T0. The voltage source is connected to the VFB node via a TC resistor RTC, so that at T0 no current flows through RTC. Therefore, the selection of the optimal RTC does not affect the selection of a scaling resistance for generating VFB. The current through RTC at elevated temperatures compensates VOUT. |
