The fault diagnosis and maintenance method of series DC regulated power supply can be adjusted

You'll also need to provide some necessary information, such as: What about the nature of the input being AC 220VAC? Or DC 24VDC?

Or is it something else ? How high should the input voltage be considered "overvoltage"? What is the output current limit?

Is the voltage adjustment continuously adjustable or is there only two voltage switching of 9V and 12V?

With a 220VAC input, a 13VAC output transformer can step down the 220VAC to 13VAC and filter it through bridge rectification, and a continuously adjustable DC voltage output of 9V and 12V can be achieved with an adjustable linear regulator LM317. As shown in the figure below

The output voltage of this circuit VO=VREF(1+R2 R1)+IADJ R2, where the current IADJ value is very small (tens of microamps), which is generally negligible, and the output voltage can be calculated according to VO=VREF(1+R2 R1).

In the figure, R1 is a fixed resistor, R2 is a variable resistor (potentiometer), CI and CO are the filter capacitors connected between the input and output terminals and the ground wire of LM317 respectively, if the output current is not very large, take about 100 F.

The output voltage is continuously adjustable to 9V, with short-circuit protection function, there must be a circuit diagram and design process 220V, after the transformer secondary 12V, it is OK not to have a three-terminal regulator, I have done it, to 16V.

The output resistance can increase the output electrolytic capacitor capacity, and more importantly, it depends on the performance of your voltage regulator circuit.

Increasing the load resistance or decreasing the dynamic resistance of the regulator can improve the stability; Increasing the output filter capacitor can reduce the output resistance.

When the load changes, the current between the base and the emitter of the adjustment tube changes accordingly, and the emitter current of the adjustment tube is adjusted to stabilize the voltage, and the pressure difference between the base and the emitter determines the base current, the magnification determines the emitter current, and the emitter current and the load determine the output voltage, that is, the voltage difference between the base and the emitter;

The three achieve a balance, set the base voltage constant, different emission stage voltages are required under different load conditions to balance, that is, the output voltage is not stable, when the amplification of the adjustment tube is too low (the magnification of the high-current tube is not high), the large load will inevitably lead to a significant drop in the output voltage, and the performance is like the internal resistance is too large, in fact, this is just too large the load effect.

The voltage regulator pipe is connected in the opposite direction, only left and right, then the series voltage regulator output is close to 0V. It can be detected by measuring the voltage of the regulator tube.

The diode has unidirectional conductivity, often used as a rectifier element, in the DC series circuit of the diode to the reverse diode reverse cut-off resistance approximately infinity is equivalent to an open circuit, in the half-wave rectifier circuit the diode is connected to the reverse output voltage polarity is opposite, that is, the negative electrode becomes positive, the positive electrode becomes negative, the voltage regulator diode is connected to the reverse is similar to a short circuit, the output voltage is very low only a few tenths of a volt, and the light-emitting diode is not illuminated.

In fact, in such voltage debugging, the resistance can not be reversed, otherwise there will be some short circuit problems on the line.

What faults will occur if the regulator diode is welded during the debugging of the series regulated power supply? There will be tripping.

Working principle: In addition to transforming, rectifying and filtering, the voltage stabilization part generally has four links: adjustment link, voltage reference, comparison amplifier and sampling circuit.

When the output voltage v0 changes due to changes in the grid voltage or load, the sampling circuit feeds a portion of the output voltage v0 back to the comparison amplifier and reference voltage for comparison. The error voltage generated by it is amplified to control the base current of the adjustment tube, automatically change the voltage between the adjustment tube set and the emitter, and compensate for the change of V0, so as to maintain the output voltage basically unchanged. Extended Information The series regulated circuit is one of the DC regulated power supplies, which is widely used in practical application circuits.

The commonly used 78 or 79 series three-terminal regulators are also one of them. DC regulated power supply can be widely used in national defense, scientific research, colleges and universities, laboratories, industrial and mining enterprises, electrolysis, electroplating, DC motors, charging equipment, etc.

The diagram is a series regulated circuit consisting of discrete components, which may cause the output voltage UO to rise or fall when the grid voltage fluctuates or the load changes. In order to keep the output voltage UO constant, the principle of negative feedback can be used to stabilize it. Suppose the output voltage uo rises for some reason, the voltage stabilization process is uo ub2 ub1(uc2) uo.

Zener diode voltage regulator circuit is a typical parallel type voltage regulator circuit, the principle of voltage regulation is that when the output voltage rises due to the increase of input voltage or the decrease of load current, the impedance of Zener diode decreases, so that the current flowing through Zener diode increases, thereby increasing the voltage drop of the current limiting resistor, so that the output voltage decreases. When the output voltage drops due to the decrease of input voltage or the increase of load current, the impedance of the Zener diode increases, so that the current flowing through the Zener diode decreases, thereby reducing the voltage drop of the current limiting resistor, and achieving the purpose of voltage stabilization.

Increasing the load resistance or decreasing the dynamic resistance of the regulator can improve stability; Increasing the output filter capacitor can reduce the output resistance.

The output internal resistance can increase the output electrolytic capacitor capacity, and the more important thing is to see the performance of your voltage regulator circuit.

Advantages of parallel regulated power supply: 6 1 There is overload self-protection performance, and the adjustment tube will not be damaged when the output is broken. 6 1 When the load changes, the voltage regulation performance is better.

6 1 Good adaptability to instantaneous changes. Disadvantages of parallel voltage regulator circuits: 6 1 The efficiency is low, especially at light loads, and almost all the electrical energy is consumed on the current limiting resistor and the adjustment tube.

6 1 The output voltage regulation range is small. 6 1 The stability is not easy to make very high. In fact, these advantages of parallel regulated power supply can be achieved by using some special circuits for series regulated power supply.

However, these inherent shortcomings of parallel regulated power supplies are difficult to improve, so series regulated power supplies are commonly used now.

The switching regulated power supply is directly rectified to obtain high-voltage DC, and the output voltage is adjusted by the high-frequency ** device controlling the on-off time ratio of the switch tube. There are two kinds of switching power supply circuits, series type and parallel type, the advantage of switching type regulated power supply is high efficiency, because the power consumed by the transistor itself in the switching state is very small, and it can reach 70-80% or even higher efficiency, and there is no step-down transformer, and its output transformer is working at high frequency, and its volume is much less than 50 Hz power frequency transformer. Therefore, the circuit of the switching power supply is small and lightweight.

Switching power supplies can operate over a wide range of voltages.