![]() R3 is wrongly mentioned in the formula above, please ignore R3, it is not required in the formula.Īlthough the above configurations can be used in any place where precision voltage setting and references may be required, it's extensively used in SMPS circuits nowadays for generating precise reference voltage for the connected opto coupler, which in turn prompts the input mosfet of the SMPS to regulate the output voltage precisely to the desired levels. When T2 turns ON, it shunts the supply voltage to ground thus regulating the supply voltage at the desired level. The 1K preset is adjusted such that the TL431 just conducts at around 56 V which is optimal level for charging a 48 V battery.Īs soon as the TL431 conducts, the T1 shuts off, causing T2 to turn ON. In this design, the TL431 IC is well protected with 12 V zener diodes to ensure the internal circuitry of the device is not subjected to extreme breakdown voltages. The following image shows how the TL431 device can be used for controlling windmill generators for charging upto 48 V batteries. Making a Precision Shunt Regulator using TL431 for Windmill Applications ![]() The resistor at the base of the transistor is not critical and may arbitrarily selected anything between 1k and 4k7. This resistor protects the transistor from burning due to short circuit at the output. This will lead naturally to our discussion of digital systems. We will conclude this chapter by looking at how transistors can be used as logic devices. In the case of both devices, we will talk about the nonlinear models, load line analysis and applications. This can be calculated in the same way as discussed previously for the first TL431 regulator diagram. Next we will talk about diodes, followed by the bipolar junction transistor. The resistor at the input side limits the maximum tolerable current that can be sinked or shunted by the PNP transistor. In the above diagram we can see two resistors whose values are not mentioned, one in series with the input supply line, another at the base of the PNP transistor. The output current will depend on the magnitude of current the transistor is able to sink. In the above diagram most of the parts placement is similar to the first shunt regulator design, except that here the cathode is provided with a resistor to positive and the point also becomes the base trigger of the connected buffer transistor. However this device can be configured to shunt higher amount of currents by adding an external shunting transistor with the output of the TL431.įor working with higher current a transistor buffer may be used, as shown in the following circuit. Normally, the TL431 adjustable zener diode cannot used with currents over 100 mA. Making a High Current Shunt Regulator using TL431 The above configurations are restricted to a max 100 mA current at the output. The parts can be identified through the formula shown in the diagram.
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