Series regulated power supply circuit, describing the maintenance idea of input voltage reduction

1. It has little to do with voltage stabilization and adjustment.

2. It is unlikely that the low-voltage alternating current from the transformer will change.

3. The problem of the rectification part should be considered at the midpoint, and the maximum possibility is that a diode is damaged and the full-wave rectification becomes half-wave rectification, resulting in a voltage drop.

Series regulated power supply, that is, a circuit that uses the adjustment tube Q1 connected in series in the circuit to dynamically divide the voltage and obtain a stable voltage for the load. The working principle of the series regulated power supply is a device that keeps the output voltage constant when the input voltage fluctuates, and the output voltage remains unchanged by using the principle that the voltage at both ends of the regulator diode remains unchanged, and the multi-stage transistor is used to form a Darlington composite circuit to form an amplifier to improve the voltage stabilization accuracy.

In addition to transforming, rectifying and filtering, the series voltage regulator circuit generally has four links: adjustment link, voltage reference, comparison amplifier and sampling circuit. When the output voltage v0 changes due to the change of grid voltage or load, the sampling circuit feeds a part of the output voltage v0 back to the comparison amplifier and the reference voltage for comparison, and the generated error voltage 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.

The adjustment tube in the series regulator circuit works in the amplified state for the following reasons:

In the series voltage regulator circuit, the adjustment tube works in the amplified state. If it works in a saturated state, the voltage drop of the adjustment tube is only about, so that the output voltage is basically equal to the input voltage, so that the circuit loses the voltage regulation function.

a, amplification state, the adjustment tube is to amplify the output current, working in the amplification area.

Saturated and cut-off transistors are generally used in the switching state.

aThe higher the amplified input voltage, the greater the CE voltage drop of the transistor! So it's magnified!

Since you're a high school student, I don't know how much you know about "the basic workings of transistors" and so on? There is also the basic concept of "feedback" and so on.

Now just a few simple questions:

1. The on/off of the power supply load, the change of current, the change of input voltage and temperature, etc., will cause the change of output voltage.

2. The "simplest series voltage regulator circuit" does not have the "negative feedback" link of "VO (due to VB unchanged)--VBE --IB --VCE --VO" as it says, that is to say, the follow-up analysis of the circuit he talked about is wrong! In that circuit, the voltage is regulated by using the voltage stabilization value of the regulator and the VBE of the transistor to achieve voltage regulation.

Only in the series regulated circuit with amplification link does the negative feedback regulation link exist: VO --V2 VB --V2 IC --V2 VC (that is, V1 VB) -VO (because VO=VB+VBE, and VBE is basically unchanged).

By the way, "negative feedback" means that the amount of change in the output is added to the input "in reverse", so as to partially cancel out the change in the output and play a "stable" role.

3. C2 is a filter capacitor, which should be found in a regulated power supply.

As mentioned earlier, the change in VO is applied to the base of V2 by the resistor partial voltage.

4. It is not to adjust the VBE, but to adjust the VB, usually the VBE is on the left and right, and the change is small.

Hello, 1. Stable output voltage: Series negative feedback can keep the output voltage at a constant voltage value, and overcome the instability of the output voltage caused by changes in the reference power supply (such as battery supply voltage) and other parameters in the circuit.

2. Reduce input resistance: The negative feedback mechanism can reduce the power consumption at the input end of the circuit, thereby reducing the input resistance in the circuit and the heat loss between it. As a result, the stability of the Songchun circuit is improved, and the efficiency and reliability of the response are also improved.

Dear users, voltage series negative feedback is a common circuit design technique, which can optimize the circuit performance by feeding back part of the output voltage to the input terminal. Among them, stabilizing the output voltage and reducing the input resistance are the two important roles of voltage series negative feedback.

First of all, the voltage series negative feedback can stabilize the output voltage. In circuits, the output voltage is often affected by various factors, such as fluctuations in the supply voltage, temperature changes, drift of component parameters, and so on. These factors can lead to instability in the output voltage, affecting the performance and reliability of the circuit.

By introducing voltage series negative feedback, part of the output voltage can be fed back to the input terminal, forming a negative feedback loop, thereby suppressing the fluctuation of the output voltage and making the output voltage more stable.

Secondly, the voltage series negative feedback can also reduce the input resistance. In some circuits, the input resistance tends to be higher, which can cause the circuit to respond slower to external signals or require a larger input signal for the circuit to function properly. By introducing voltage series negative feedback through laughter, a part of the output voltage can be fed back to the failed input, thereby reducing the input resistance and improving the input sensitivity and response speed of the circuit.

In summary, electric vertical bucket voltage series negative feedback is a common circuit design technique, which can optimize circuit performance by stabilizing the output voltage and reducing the input resistance.

Voltage series negative feedback is a form of connecting a negative feedback circuit between the input and the output. This form of negative feedback effectively stabilizes the output voltage and lowers the input resistance. The principle is that when the output voltage changes, the feedback circuit will adjust the voltage at the input so that the output voltage remains the same.

The advantage of voltage series negative feedback is that it can effectively suppress changes in the output voltage, thereby improving the stability of the system. It also reduces the input resistance of the system, which reduces the input resistance of the system, thus improving the efficiency of the power supply. In addition, the voltage series negative feedback can also effectively suppress the noise, making the output of the system more stable.

In addition, voltage series negative feedback can also improve the dynamic range of the system. It can maintain the stability of the output voltage by adjusting the voltage at the input when the output voltage changes, so that there is no system jitter caused by voltage changes.

In summary, voltage series negative feedback has the effect of stabilizing the output voltage and reducing the input leased liquid resistance, which can improve the stability of the system, reduce noise, improve the efficiency of the power supply, and improve the dynamic range of the system.

Voltage series negative feedback is a circuit used to stabilize the output voltage, which combines an external circuit with the original circuit to form a negative feedback loop with a series of connections. When the output voltage of the negative feedback loop changes, the negative feedback circuit will feed back the changed signal to the input of the power supply, so as to adjust the cracking output of the power supply to keep it at a stable voltage level. The advantage of voltage series negative feedback is that it can provide high-precision control, so that the voltage can be stably kept at the set level, and the anti-interference ability is strong, which can effectively resist external interference and reduce the impact of voltage jitter on the system.

Typical values for IN4734A are: Let's assume that the voltage of this regulator tube is VZ, and the resistance in series into R4 is A, and according to the op amp characteristics, we know that VO=3VZ(1+A), where A changes to 0 1, then the output voltage range is 3VZ.

IN4737 regulated voltage.

For the voltage comparison circuit to work properly, the minimum sampling voltage is.

Both the potentiometer and the voltage divider resistor are 1k, which means that the voltage sampling can be adjusted between 1 3 --- 2 3 of the output voltage.

When the output of 2 3= is the lowest voltage, ie;

When the output of 1 3= is the maximum voltage, ie.

It can be understood that the midpoint voltage of the potentiometer is equal to the voltage of the regulator tube.

The nominal value of the stable voltage of the 1N4734 is , so the highest output voltage in the regulated circuit is , and the lowest is .

Because in the closed-loop working range of the op amp, the voltage of the two input pins will always be basically equal, in this problem, when the sliding foot of the 1k potentiometer is adjusted to the bottom, the total resistance of the voltage regulation series loop is 3 times that of the op amp inverting input to ground (R4), and when the 1k potentiometer sliding foot is adjusted to the top, the total resistance of the voltage regulation series loop is the multiple of the op amp inverting input to the ground resistance (R4 + potentiometer), so the output voltage and the reference voltage are also the same multiple relationship.

This problem is easy to understand with the phenomenon of virtual ground and virtual zero of op amp:

First of all, the circuit works in the amplification area, in order to play a role in voltage stabilization, the voltage of the positive input terminal of the op amp is uz, because the voltage of the negative input end of the virtual ground phenomenon is also uz, and then look at the resistance R1R2R3 series branch, the output voltage of the voltage regulator circuit is the sum of the three resistor voltages, because the negative input current of the op amp is 0 (virtual zero phenomenon), so the voltage of each resistor can be directly calculated with the voltage division ratio, so it is not difficult to see:

When the input voltage reaches the minimum, the R3 voltage is the input voltage = uz, so that the total voltage of R1R2R3 in series is the output voltage of the voltage regulator circuit is:

uz(r1+r2+r3) (r3) is reached.

When the input voltage reaches the maximum, the R3+R2 voltage is the input voltage = uz, so that the total voltage of R1R2R3 in series is the output voltage of the voltage regulator circuit is:

uz(r1+r2+r3) (r2+r3) is the minimum value.

1. The regulated power supply has voltage input adaptation range requirements, such as 16V 27V, in this range, no matter whether the input voltage is high or low, the output voltage is unchanged.

2 The formula is to find the minimum and maximum values of the output voltage when R2 changes to the upper and lower ends, which is the calculated output voltage adjustable range.

3 In the regulated state, the voltage drop of the regulator tube is equal to the input voltage minus the output voltage. No matter how much the output voltage is adjusted, this is mostly the case.

The working principle of series regulated power supply is to achieve voltage stabilization by changing the voltage drop of the CE pole of the adjustment tube, when the output voltage changes for some reason, the voltage of the sampling circuit will also change, and the base voltage of the adjustment tube is controlled to change the voltage drop of the CE pole through comparison and amplification, if the output voltage increases, the CE voltage drop of the adjustment tube increases, the output voltage decreases, and vice versa.

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.