TL431 has the advantages of small size, precise and adjustable reference voltage, and large output current. Therefore, TL431 can be used to make a variety of stable
compressor. Its performance is that the output voltage is continuously adjustable up to 36V, the operating current range is as wide as 0.1-100mA, and the typical value of dynamic resistance is
It is 0.22 ohms, and the output clutter is low. Its maximum input voltage is 37V, the maximum operating current is 150mA, and the internal reference voltage is
2.5V, the output voltage range is 2.5 ~ 30V.
TL431 is a 2.5-36V adjustable precision shunt regulator produced by Texas Instruments (TI) and Motorola. That
With excellent performance and low price, it can be widely used in monolithic precision switching power supply or precision linear regulated power supply. In addition, the TL431 can also
Constitute voltage comparator, power supply voltage monitor, delay circuit, precision constant current source, etc.
The package type of the common TL431 (KA431AZ) is shown in the figure. CATHODE means cathode, ANODE means anode
and REF are denoted as reference poles.
Respectively represented by K (C), R, and A, where K (C) is the control terminal, R is the sampling terminal, A is the ground terminal, and some circuit diagrams use 1, 2, and 3 points
Do not represent R, A, K.
TL431 is a high-precision adjustable current and voltage control device from TI Texas Instruments
Several basic usages of TL431:
As a cost-effective common shunt voltage reference, TL431 has a wide range of uses. Here is a brief introduction to several common and uncommon connections of TL431.
Figure (1) is a typical connection of TL431, which outputs a fixed voltage value. The calculation formula is: Vout = (R1+R2)*2.5/R2,
At the same time, the value of R3 should satisfy 1mA < (Vcc-Vout)/R3 < 500mA
When the value of R1 is 0, R2 can be omitted. At this time, the circuit becomes the form of figure (2), and TL431 is equivalent to a 2.5V voltage regulator here.
TL431 can also be used to form a discriminator, as shown in Figure (3), this circuit outputs Vout at a high level when the input voltage Vin < (R1+R2)*2.5/R2, otherwise the output is close to 2V. It should be noted that when Vin fluctuates in a small range around (R1+R2)*2.5/R2, the circuit will output an unstable value.
TL431可以用来提升一个近地电压，并且将其反相。如图(4)，输出计算公式为： Vout = ( (R1+R2)*2.5 - R1*Vin )/R2
特别的，当R1 = R2的时候，Vout = 5 - Vin。这个电路可以用来把一个接近地的电压提升到一个可以预先设定的范围内，唯一需要注意的是TL431的输出范围不是满幅的。
TL431自身有相当高的增益（我在仿真中粗略测试，有大概46db），所以可以用作放大器。
图(5)显示了一个用TL431组成的直流电压放大器，这个电路的放大倍数由R1和Rin决定，相当于运放的负反馈回路，而其静态输出电压由R1和R2决定。
这个电路的优点在于，它结构简单，精度也不错，能够提供稳定的静态特性。缺点是输入阻抗较小，Vout的摆幅有限。
图(6)是交流放大器，这个结构和直流放大器很相似，而且具有同样的优缺点。我正在尝试用这个放大器代替次级运放来放大热释红外传感器的输出信号。
用TL431制成的高精度稳压直流电源
该电路的纹波小，精度高，可以作高档电器供电电源。