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What is the reference voltage of the TL431?
In the case of the current sink, the voltage at the cathode will be Vref+Vbe (Vbe of the BJT) when it is regulating. The internal transistor shunts the current from the resistor to the BJT base to maintain the reference input of the TL431 at Vref.
What does the sinking end of TL431 do?
The sinking end of TL431 drives the light-emitting part of an optocoupler. The feedback voltage obtained by the photosensitive part of the photocoupler on the main side of the power supply is used to adjust the switching time of a current mode PWM controller.
Why does the TL431 turn on too much?
The goldilocks answer – the transistor is just conducting enough to allow 2.5 v to develop across Rs which in turn is just starting the turn the TL431 on and if it turned on too much, the current would reduce thru Rs and this would counteract the TL431 turning on too much. It’s called negative feedback.
When does the TL431 trigger the V protection point?
As shown in the figure, when Vi exceeds a certain voltage, TL431 triggers. At this time, the thyristor is turned on and generates a large instantaneous current, which blows the fuse, thereby protecting the rear circuit. V protection point = (1+R1/R2)Vref. Figure 3. TL431 Circuit: Overvoltage Protection As the picture shows.
TL431 mentioned earlier contains a 2.5V internal reference voltage, so when the end of the introduction of the REF output feedback, the device from the cathode to the anode through a wide range of streaming, control the output voltage.
How is peak current determined in a flyback converter?
For the flyback converter, the input capacitor supplies the input current when the diode rectifier is off. The voltage discharge on the input capacitor, due to the input average current, should be within the limits specified. VIN,PK = √2 × VAC,MIN = peak voltage at minimum input AC voltage.
How is the input capacitor chosen for a flyback converter?
Capacitor Selection Based on Rectified Line Voltage Ripple (MAX17595) For the flyback converter, the input capacitor supplies the input current when the diode rectifier is off. The voltage discharge on the input capacitor, due to the input average current, should be within the limits specified.
Which is the best mode for a flyback converter?
Flyback converters may be operated in discontinuous conduction mode (DCM) or continuous conduction mode (CCM). The component choices, stress level in power devices, and controller design vary depending on the operating mode of the converter.