Tl431 is produced by Texas Instruments, a tl431 is a three-terminal adjustable shunt reference with good thermal stability. Its output voltage can be arbitrarily set to any value from Vref (2.5V) to 36V with two resistors. The device's typical dynamic impedance is 0.2Ω, which can be used in many applications to replace Zener diodes, such as digital voltmeters, op amp circuits, adjustable voltage supplies, switching power supplies, and more. 　 Programmable output voltage is 36V Voltage reference error: ±0.4%, typical @25°C (TL431B) Low dynamic output impedance, typically 0.22Ω Load current capability 1.0mA to 100mA Equivalent full range temperature coefficient 50 ppm/°C typical Temperature compensation operation full rated operating temperature range Low output noise voltage The equivalent circuit of tl431 is shown in the figure above, mainly including 1 error amplifier A, its non-inverting input terminal is connected to the sampling voltage obtained from the resistor divider, and the inverting terminal is connected to the internal 2.5V reference voltage Uref, and the designed UREF=Uref, the UREF is normally 2.5V, so Called the reference end; 2 internal 2.5CV reference voltage source Uref; 3NPN transistor VT, which acts to regulate the load current in the circuit; 4 protection diode VD, can prevent the chip from being damaged due to the reverse polarity of the power supply between KA. It is equivalent to an adjustable Zener voltage regulator, the output voltage is set by an external precision voltage divider resistor. R3 is the current limiting resistor of IKA. The voltage regulation principle is as follows: When UO rises, the sampling voltage UREF also rises, so that UREF "Uref", the comparator outputs a high level, so that VT is turned on, and UO starts to fall. Conversely, a drop in UO will cause the UREF to drop, and UREF "Uref, causing the comparator to flip again, the output goes low, and the VT cuts off UO. This cycle continues, from the point of view of dynamic balance, forcing UO to stabilize, thus achieving the purpose of stability, and UREF = Uref. The specific working principle of tl431 is: When the input voltage increases, the output voltage increases, resulting in an increase in output sampling. At this time, the internal circuit is adjusted to increase the current flowing through itself, which increases the circuit flowing through the current limit. Thus, the voltage drop of the current limiting resistor is increased, and the output voltage is equal to the input voltage. The current limiting voltage drop is increased, so that the output voltage is reduced to achieve voltage regulation. Fiber Optic Patch Cord Production Line Fiber Optic Patch Cord Production Line ShenZhen JunJin Technology Co.,Ltd , https://www.jjtcl.com
