Today, I will tell you about the application of resistor shunt, current limiting and voltage division circuit. The following circuit is a series voltage regulator circuit. Next, I will understand the role of each resistor in the circuit.

1. This figure is a high-efficiency series regulated power supply circuit, whose power supply +16~18V is the full wave rectifier voltage that fluctuates with the power grid. An RF resistor is added on this circuit, mainly for shunt function. This means that Q1 is responsible for almost half of the power loss. In order to reduce the power loss of Q1, a shunt resistor RF6 is placed in parallel between the emitter and collector of Q1 of the adjusting tube to shunt the current of the adjusting tube. So far, many high-power DC regulated power supplies have adopted this measure, which greatly improves the efficiency.

2. Resistance RF6 insurance function: When the circuit is working normally, the voltage drop at both ends of the shunt resistor RF6 is only about 4V, and the actual power consumption is less than 0.8W. If the carbon film resistor with rated power of 2W is selected, it can also play the role of insurance resistance when the circuit fails. It should be pointed out here that the carbon film resistor RF6 is required, because the power load per unit area is small. And its upper limit temperature is low when the rated power is working, so it is easier to cause open circuit crossover in the case of circuit overload. From the sense of circuit self-protection function, the carbon film resistance is more reliable, which is the reason why most insurance resistors use carbon film resistance.

3. The current limiting effect of the resistance RF, it can be seen that once the load appears short circuit, the input voltage (16V) will be added to both ends of the RF6, it is because of the existence of RF6, limits the growth of short circuit current, so that the short circuit current is less than 1A, this is the shunt resistance RF6 played a current limiting role.

4 current limiting resistance RX20 function is to limit the working current of the regulator tube within the rated current range: resistance R8/VR1/R2 constitute sampling voltage division circuit, R8/R2 is usually sampling voltage division resistance, potentiometer VR1 called sampling potentiometer.