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Principle and Application of DC Regulated Power Supply

Author: Apogeeweb Date: 27 May 2019  8997

DC Regulated Power Supply


This article mainly introduces how does the DC regulated power supply work, how to use it and some knowledge of maintenance. Let's take a look at this article.


This video shows how to use a power supply


Almost all electronic circuits need a stable DC power supply. In the verification and maintenance of the indicator instrument, in addition to the appropriate standard instrument, there must also be a suitable DC power supply and regulating device. When supplying power from the AC grid, it is necessary to convert the AC grid power supply into a stable DC power supply. After rectification and filtering, AC becomes DC. Although it can be used as a DC power supply, due to the fluctuation of the grid voltage, the rectified DC voltage output will also fluctuate.


At the same time, the load current in use is also constantly changing, some of which vary greatly. When it flows through the internal resistance of the rectifier, it will produce a fluctuating voltage drop on the internal resistance, causing the output voltage to fluctuate with the fluctuation of the load current. If the load current is small, the output voltage is high; if the load current is large, the output voltage is low. Voltage fluctuations of the DC power supply will cause unstable circuit operation. For precision measuring instruments, automatic controls or electronic calculation devices, it will cause measurement and calculation errors, and even affect normal operation. Therefore, a DC power supply with stable voltage is usually required.


Transistor DC regulated power supply can be used as DC power supply for various transistor meters, electronic computers, automatic control systems and equipment. The precision stabilized current power supply can also be used as the stabilized current power supply for the verification of some electrical instruments. Therefore, transistor DC regulated power supply is a necessary instrument commonly used in scientific research, production, teaching, maintenance and other departments.




I Principle of DC Regulated Power Supply

II Application of DC Regulated Power Supply

  3.1 Maintenance Procedures

  3.2 Common Examples of Troubleshooting of Voltage Regulated Power Supply




I Principle of DC Regulated Power Supply

• Block Diagram and Working Principle

The typical circuit block diagram of transistor series DC regulated power supply is shown in figure 1. It consists of a rectifier filter circuit, series voltage regulated circuit, auxiliary power supply and protection circuit.

II Application of DC Regulated Power Supply

The use of a DC stabilized power supply is very simple. Pay attention to the polarity of the required DC voltage when using it. If it is necessary to output a positive voltage, the output terminal of the DC stabilized power supply "-" is connected to the "ground" terminal of the electrical equipment, and the terminal "+" should be connected to the required positive voltage terminal. If you need to output a negative voltage, you need to reverse the above wiring method. Before energizing, use a multimeter to measure whether the output voltage meets the requirements, so as to avoid damage to electrical equipment due to excessive voltage.


In order to make the electrical equipment work properly and not to affect the stable and reliable operation of the electrical equipment because of the poor performance of the DC power supply, it is best to test it simply before acting on the regulated power supply. The main contents of the test are the regulation range of the output voltage, the stability degree, the ripple voltage and the overcurrent protection and so on.


III Maintenance of DC Regulated Power Supply

3.1 Maintenance Procedures

• Preliminary Surface Examination 

All kinds of voltage-regulated power supplies are generally equipped with overload or short circuit protection fuses and input and output terminals. You should first check if the fuses are fused or loose, whether the terminals are loose or short-circuited to the ground, and whether the gauge needle of the voltage indicator is jammed. Then open the casing cover to see if the power transformer has scorched taste or mildew and whether the resistance and capacitance have obvious damage phenomena, such as scorching, mold-breaking, liquid leakage, cracking and so on.


• Measurement of Rectifier Output Voltage 

In all kinds of regulated power supply, there are one or more groups of the rectified output voltage. If this rectified output voltage has a group of abnormal, then the regulated power supply will have a variety of faults. Therefore, during maintenance, it is necessary to first measure whether the rectified output voltage is normal.


• Test Electronic Device 

If the rectified voltage output is normal, but the output voltage is not normal, you need to further test whether the performance of the regulator tube, amplifier tube, etc. is good, whether the capacitor has a breakdown, short circuit or open circuit. If a device with a damaged or variable value is found, normally the regulated power supply can be restored to normal after updating.


• Check the Working Point of the Circuit 

If the rectifier voltage output and related electronic devices are normal, the operating point of the circuit should be further checked. For the transistor, there should be a certain working voltage between the collector and the emitter, and the bias voltage between the base and the emitter should meet the requirements and ensure that it works in the amplification area.


• Analysis of Circuit Principle 

If the voltage of an operating point of a transistor is found to be abnormal, there are two possibilities: one is that the transistor is damaged; the other is caused by the damage of other components in the circuit. At this time, it is necessary to carefully analyze the causes of the problems according to the circuit schematic diagram, and further identify the damaged and variable components.


3.2 Common Examples of Troubleshooting of Voltage Regulated Power Supply

• There is voltage stabilization but no voltage regulation 

When using a regulated power supply, it is usually to start the preheating first, then adjust the output voltage of the potentiometer "coarse adjustment", observe whether the voltage adjustment function and adjustment range are normal, and finally adjust to the required power supply voltage value and connect it to the load. The voltage is normal when there is no load, but the output voltage drops after the load are connected. If the possibility of external circuit failure is ruled out, it can be determined that the failure is that the voltage-regulating power supply has no voltage-regulating effect.


During the maintenance process, the on-off condition between the collector and the emitter of the high-power regulator tube can be measured with a multimeter. If no problem is found, you can further check whether the rectifier diode is damaged. As long as the rectifier is damaged, full-wave rectification becomes half-wave rectification. When there is no load, the large-capacity filter capacitor can still provide enough rectified output voltage to ensure the voltage regulation function of the regulated output. After the load is switched on, the rectified output voltage drops immediately, and the voltage at the regulated output terminal also drops, losing its stabilizing effect.


• The output voltage is too high, and there is no function of voltage regulation and voltage stabilization 

Under the condition of no load, the output voltage of transistor DC regulated power supply is larger than the specified value, and there is no voltage regulation and voltage stabilization, the fault may occur because of the following reasons:


— The collector and emitter of one of the composite adjustment tubes is a breakdown or short-circuited, and the rectifier output voltage is directly added to the voltage regulation output through the short circuit transistor and is not controlled by voltage regulation and voltage stabilization.


— The collector or emitter of the sampling amplifier tube is on or off, and the composite adjusting tube is directly under the negative voltage of the auxiliary power supply Dz, and the base current is very large so that the internal resistance between the emitter and the collector of the adjusting tube becomes very small. The voltage of the rectifier output is added directly to the stable voltage output terminal.


• The voltage output of each gear is very small and there is no voltage regulating effect 

The failure may occur because of the following reasons:

— There is no rectifying voltage output from the main rectifier

— The voltage of the auxiliary power supply Dz is zero, resulting in the adjustment tube not working.

— The c-e of the sampling amplifier tube breaks through the short circuit in reverse, resulting in the adjustment tube not working.



1. What is DC regulated power supply?

A regulated power supply is an embedded circuit; it converts unregulated AC (Alternating Current) into a constant DC. ... Its function is to supply a stable voltage (or less often current), to a circuit or device that must be operated within certain power supply limits.


2. What is the importance of DC regulated power supply?

A regulated power supply is used to ensure that the output remains constant even if the input changes. A regulated DC power supply is also known as a linear power supply, it is an embedded circuit and consists of various blocks. The regulated power supply will accept an AC input and give a constant DC output.


3. What is the difference between regulated and unregulated DC power supply?

In regulated power supplies, the output DC voltage is regulated so that a change in input voltage is not reflected in the output. In contrast, unregulated power supplies do not have a voltage regulation at the output. This is the key difference between the regulated and unregulated power supply.


4. What is the output of the regulated power supply?

In fancy electrical terms, a regulated power supply provides a constant output voltage, independent of the output current. A regulated power supply with multiple regulators can offer multiple output voltages for operating different devices.


5. What are the applications of the regulated power supply?

• Mobile phone chargers.

• Regulated power supplies in different appliances.

• Various oscillators & amplifiers.


6. How do I know if a power supply is regulated?

You can generally stick one probe into the middle of the connector, and hold the other against the outside. With a few exceptions, the middle is positive, so use the red lead there, and use the black lead on the outside shell. Regulated supplies, without any load, should measure very close to the target voltage of 12v.


7. How do you regulate a power supply?

To maintain a steady voltage level regardless of the amount of current drawn from a power supply, the power supply can incorporate a voltage regulator circuit. The voltage regulator monitors the current drawn by the load and increases or decreases the voltage accordingly to keep the voltage level constant.


8. What is meant by unregulated DC?

Every electronic circuit or system needs a stable DC voltage for its intended operation. The desired DC voltage is normally obtained by converting the AC mains or line voltage into a DC voltage. ... Such a system is called an unregulated power supply because the output changes significantly when its input load varies.


9. What is a regulated power supply and its limitations?

Linear regulators can only be used to step down voltage. For an AC-DC power supply, a transformer with rectification and filtering will need to be placed before the linear power supply which will add to overall costs and effort. Limited outputs. Linear-regulated power supplies only provide one output voltage.


10. What is the application of the DC power supply?

What are common DC applications? This form of power is most commonly produced by sources such as solar cells, batteries, and thermocouples. DC power is widely used in low voltage applications such as charging batteries, automotive applications, aircraft applications and other low voltage, low current applications.



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