TL431 is one of the semiconductors and an adjustable precision zener shunt regulator. The output voltage of it can be set to any value between 2.5V and 36V with the use of two external resistors, which acting a voltage divider.
With the cost reducing and very sharp trun-on characteristics, the TL431 is an excellent alternative to a zener diode in many applications. But how does it saving?
In the early, TL431 controller I used to reduce the cost of feedback loop. While not offering as good a gain-bandwidth as a standalone amplifier, this threeterminal part includes a reference, takes up little board space, and became widespread in the industry as a way to achieve reasonable performance at a reduced cost.
Does reduce the cost of feedback loop mean really cost? Yes, control loop is always a target for cost reduction. The designers are often so focused on power processing that control design is often an afterthought, and not viewed as crucial to performance. Only later in the design process does the importance of a good controller become apparent.
TL431 can save cost, especially used by many power supply designers. Because current-mode control is the best way to control converters, and for this type of control, the optimal compensation network is a Type II amplifier. At the same time, power suppliers are constantly striving to reduce cost. No matter in the past or now, prices are always be driven down to insanely low levels, and compromises must often be made to meet performance and cost goals. So, whether you are a designer or a supplier, you would like choose TL431 which can save the cost.
