What is a Linear Voltage Regulator
Linear regulated power supply is a class of DC regulated power supply used earlier. According to the working state of the adjustment tube, we often divide the regulated power supply into two categories: linear regulated power supply and switching regulated power supply. Linear regulated DC power supply is characterized by: the output voltage than the input voltage is low; fast response time, the output ripple is small; low noise generated by the work; low efficiency (now often look at the LDO is to solve the problem of efficiency and the emergence of); heat (especially high-power power supply), indirectly to the system to increase the thermal noise.
According to the operating state of the regulator tube, we often divide the regulated power supply into two categories: linear regulated power supply and switching regulated power supply. In addition, there is a small power supply that uses a voltage regulator. The linear regulated power supply here refers to the DC regulated power supply in which the regulator tube operates in a linear state. A regulator operating in a linear state can be understood in this way: RW (see analysis below) is continuously variable, i.e. linear.
Principle of operation of a linear regulated power supply
Uo=Ui×RL/(RW+RL), so by adjusting the size of RW, you can change the size of the output voltage. Note that in this equation, the output of Uo is not linear if we only look at the change in value of the adjustable resistor RW, but it is linear if we look at RW and RL together. Note also that we don't draw the leads of RW connected to the left in this diagram, but on the right. Although this does not make any difference from the formula, but drawn on the right, but reflects the concept of "sampling" and "feedback" ---- actual power supply, the vast majority of the work in the sampling and feedback mode, the use of feed-forward method is rarely, or If they do, it is only an auxiliary method.
Let us continue: If we use a triode or field effect tube, to replace the variable resistor in the figure, and by detecting the size of the output voltage, to control the size of this "variable resistor" resistance, so that the output voltage remains constant, so that we have achieved the purpose of regulating the voltage. The triode or field effect tube is used to adjust the size of the voltage output, so it is called regulator.
Because the regulator is connected in series between the power supply and the load, so it is called series-type voltage regulator. Accordingly, there are parallel-type regulated power supply, that is, the adjustment tube and the load in parallel to regulate the output voltage, a typical reference regulator TL431 is a parallel-type regulator. The so-called parallel means, is like Figure 2 in the regulator, through the shunt to ensure that the attenuation amplifier tube emitter voltage "stability", perhaps this figure does not let you immediately see that it is "parallel", but a closer look, indeed. However, we should also note here: the regulator here, is the use of its nonlinear region of operation, therefore, if you think it is a power supply, it is also a nonlinear power supply. In order to facilitate your understanding, back to us to find a reasonably suitable diagram to see, until you can briefly understand it.
Since the regulator tube is equivalent to a resistor, the current flowing through the resistor will heat up, so the regulator tube operating in the linear state, generally generate a lot of heat, resulting in low efficiency. This is one of the main drawbacks of the linear voltage regulator. For a more detailed understanding of linear regulated power supplies, please refer to the Analog Electronic Circuits textbook. Here we will mainly help you to clarify these concepts and their relationship to each other.
