The voltage regulator chip is discussed in detail (2), 7805 voltage regulator chip multi-directional analysis of the voltage regulator chip 7805 voltage regulator chip application circuit voltage regulator chip is one of the current important chips, the editor once analyzed the market prospect of the voltage regulator chip for you in the previous article . In this article, we will bring you a specific voltage regulator chip - 7805 voltage regulator chip. If you are interested in this voltage regulator chip, you may wish to continue reading the text.

1. Introduction of 7805 voltage regulator chip

7805 is the most commonly used voltage regulator chip. It is easy to use. It can input a DC voltage regulator with a very simple circuit. Its output voltage is exactly 5v, which is exactly the voltage required for the operation of the 51 series microcontroller. He has many series such as ka7805, ads7805, cw7805, etc. There are slight differences in performance, and the most used is lm7805.

The structure of 7805 is to use 78/79 series three-terminal voltage regulator IC to form a regulated power supply. There are very few peripheral components required. The 7805 three-terminal voltage regulator IC circuit also has protection circuits for overcurrent, overheating and adjustment tubes. It's reliable, convenient, and inexpensive. The numbers after 78 or 79 in the model of this series of integrated voltage stabilizer represent the output voltage of the three-terminal integrated voltage stabilizer circuit. For example, 7806 indicates that the output voltage is positive 6V, and 7909 indicates that the output voltage is negative 9V.

Because the three-terminal fixed integrated voltage regulator circuit is easy to use, it is often used in electronic production. In practical applications, a large enough heat sink should be installed on the three-terminal integrated voltage regulator circuit (of course, it is not necessary under the condition of low power). When the temperature of the voltage regulator tube is too high, the voltage regulation performance will be deteriorated or even damaged. When a regulated power supply that can output a current of more than 1.5A is required in the production, several three-terminal regulated circuits are usually used in parallel, so that the maximum output current is N 1.5A, but attention should be paid to the application: the integrated stabilizer used in parallel The voltage circuit should use products from the same manufacturer and the same batch number to ensure consistent parameters.

In addition, a certain margin is left on the output current to avoid the chain burning of other circuits when individual integrated voltage regulator circuits fail. The TO-220 and TO-202 packages are most commonly used in the 78 ** and 79 ** series of three-terminal regulators. The graphics, pin numbers, and pin functions of these two packages are shown in the attached drawings.

From the front, the ①②③ pins are marked in order from left to right. When connecting to the circuit, the voltage of the ① pin is higher than that of the ② pin, and the ③ pin is the output bit. For example, for 78** positive pressure series, ① pin is high potential, ② pin is grounded, and ③ pin is the output bit; while for 79** negative pressure series, ① pin is grounded, ② pin is connected to negative voltage, and ③ pin is the output bit. As shown in the attached image. In addition, it should also be noted that the heat sink is always connected to the second pin of the lowest potential. In this way, in the 78** series, the heat sink is connected to the ② pin (ground), while in the 79** series, the heat sink is connected to the ② pin (input end).
Two, 7805 internal circuit

The internal circuit of the 7805 three-terminal voltage regulator IC has the functions of overvoltage protection, overcurrent protection and overheating protection, which makes its performance very stable. Can achieve output current of more than 1A. The device has a good temperature coefficient, so the application range of the product is very wide. Local regulation can be used to eliminate noise effects, solving the dispersion problem associated with single-point regulation, and the output voltage error accuracy is divided into ±3% and ±5%.

3. 7805 application circuit

7805 typical application circuit diagram: (in the figure, the wrong pin 2 is grounded and pin 3 is output) The typical application circuit of the 78XX series integrated voltage regulator is shown in the figure below, which is a regulated power supply circuit that outputs a positive 5V DC voltage. The IC adopts an integrated voltage regulator 7805, C1 and C2 are the input and output filter capacitors respectively, and RL is the load resistance. When the output current is large, the 7805 should be equipped with a heat sink.

The figure below shows the application circuit for increasing the output voltage. Zener diode VD1 is connected in series between pin 2 of the 78XX regulator and the ground, which can increase the output voltage Uo to a certain extent. The output voltage Uo is the sum of the output voltage of the 78XX regulator and the voltage regulator value of the Zener diode VC1. VD2 is the output protection diode. Once the output voltage is lower than the regulated value of VD1, VD2 is turned on, bypassing the output current to protect the output stage of the 7800 regulator from being damaged by the 7905 typical application circuit diagram.

The figure below shows the application circuit where the output voltage can be adjusted within a certain range. Due to the role of the R1, RP resistor network, the output voltage is increased, and the increase depends on the ratio of RP to R1. By adjusting the potentiometer RP, the output voltage can be adjusted within a certain range. When RP=0, the output voltage Uo is equal to the output voltage of the 78XX regulator; when RP increases gradually, Uo also increases gradually. The figure below shows the application circuit for expanding the output current. VT2 is an external expansion rate tube, VT1 is a push tube, and the two are connected by Darlington. R1 is the bias resistor. The maximum output current of the circuit depends on the parameters of ov VT2