CN216290682U - Line loss compensation circuit - Google Patents

Abstract

The utility model discloses a line loss compensation circuit, which is applied to a switching power supply. Sampling the voltage V1 and amplifying the output voltage V2; the voltage divider circuit for dividing the voltage V2 and outputting the divided voltage V3; the adding circuit for dividing the divided voltage V3 The voltage V3 is added with the reference voltage VREF to output a voltage Vf, which is used as the reference voltage of the switching power supply voltage loop. The method and circuit of the utility model can solve the line loss compensation function under the condition that the output line loss of the switching power supply is too long, the output voltage is too long and the output voltage drops or changes too much. It has the characteristics of simple circuit structure, active adjustment, suitable for different line loss environments, and low cost.

Description

A line loss compensation circuit

technical field

The utility model belongs to the technical field of switching power supplies, in particular to the line loss compensation of the output voltage of the switching power supply.

Background technique

From the relationship between the voltage V, the resistance R and the current I, V=R*I, it can be known that the impedance on the connection line between the output end of the switching power supply and the device and the output current of the switching power supply will cause the voltage from the output voltage to the device to change. The deviation of the power supply voltage on the power supply often causes the instability of the equipment, so the output voltage accuracy is an important indicator in the performance of the switching power supply. Most switching power supplies with high power or long output lines have the function of line loss compensation. However, the existing line loss compensation control method, device composition, cost, structure and performance have no advantages. The existing technology mainly has the following characteristics:

At present, the commonly used line loss compensation circuit widely adopts the circuit scheme of connecting two wires at the output end of the switching power supply to sample the voltage of the equipment. On the one hand, this scheme requires external wires, which makes the cost high, and on the other hand, the wiring is more complicated, which will cause space. and waste of cost.

In addition, there are also time-delay protection circuits built with analog devices, but they cannot be actively adjusted due to different line losses, and the scope of use is narrow.

Utility model content

In view of this, the technical problem to be solved by the present invention is to provide a line loss compensation circuit, which can reduce the line loss when the connection line from the output end of the switching power supply to the equipment is long, or the output current of the switching power supply is large, and also has a circuit Simple structure, active adjustment, suitable for different line loss environments, and low cost.

To achieve the above object, the utility model adopts the following technical solutions:

A line loss compensation circuit, which is applied to a switching power supply, is characterized by comprising: a sampling amplifying circuit and an adding circuit;

The sampling amplifying circuit is used to input the sampling voltage V1 reflecting the output condition of the switching power supply, and output the voltage V2 after amplifying;

The adding circuit is used for adding the voltage V2 and the reference voltage VREF to output a voltage Vf, and the voltage Vf is used as the reference voltage of the switching power supply voltage loop.

Further, the sampling voltage V1 is a voltage obtained by sampling the output voltage of the switching power supply, or a voltage obtained by sampling the output current of the switching power supply.

As a specific implementation of the sampling amplifier circuit, it is characterized in that it includes an operational amplifier U1B, a resistor R1 and a resistor R2, the non-inverting input terminal of the operational amplifier U1B is used to input the sampling voltage V1, one end of the resistor R1 is grounded, and the other end of the resistor R2 is grounded. The other end is simultaneously connected to the inverting input end of the operational amplifier U1B and one end of the resistor R2, and the output end of the operational amplifier U1B and the other end of the resistor R2 are connected together to output a voltage V2.

Further, the resistor R2 is an adjustable resistor.

Further, the line loss compensation circuit also includes: a voltage divider circuit;

The voltage divider circuit is used to divide the voltage V2 and output the divided voltage V3;

The adding circuit is used for adding the divided voltage V3 and the reference voltage VREF to output a voltage Vf, and the voltage Vf is used as the reference voltage of the switching power supply voltage loop.

As a specific implementation of the voltage divider circuit, it is characterized in that it includes a resistor R3 and a resistor R4, one end of the resistor R3 is used to input the voltage V2, the other end of the resistor R3 is connected with one end of the resistor R4, and the output voltage divider Voltage V3, the other end of resistor R4 is grounded.

Further, the sampling amplifier circuit includes an operational amplifier U1B, a resistor R1 and a resistor RP1. The non-inverting input terminal of the operational amplifier U1B is used to input the sampling voltage V1, one end of the resistor R1 is grounded, and the other end of the resistor R2 is connected to the inverting phase of the operational amplifier U1B at the same time. The input end and one end of the resistor R2, the output end of the operational amplifier U1B and the other end of the resistor R2 are connected together to output the voltage V2.

As a specific implementation of the adding circuit, it is characterized in that it includes a resistor R5, a resistor R6, a resistor R7, a resistor R8 and an operational amplifier U1A, one end of the resistor R5 is used to input the divided voltage V3, and the other end of the resistor R5 is simultaneously Connect one end of the resistor R6 to the inverting input end of the op amp U1A, the other end of the resistor R6 is used to input the reference voltage VREF, and one end of the resistor R7 is connected to one end of the resistor R8 and the non-inverting input end of the op amp U1A, and the other end of the resistor R7 One end is grounded, and the other end of the resistor R8 is connected with the output end of the operational amplifier U1A for the output voltage Vf.

Further, the resistance values of the resistor R5, the resistor R6, the resistor R7 and the resistor R8 are the same.

The working principle of the present utility model will be analyzed in conjunction with specific embodiments, which will not be repeated here. Compared with the prior art, the present utility model has the following beneficial effects:

1. When the output voltage line loss of the present utility model is relatively large, the voltage of the device terminal can still maintain a relatively high voltage accuracy;

2. The utility model circuit can be used as the overvoltage protection function circuit of the switching power supply when sampling the output main power voltage, and can be used as the overpower protection function circuit of the switching power supply when sampling the output main power current. It can be used as an over-temperature protection function circuit to realize multiple multiplexing functions of the circuit;

3. When the adjustable resistance is adopted in the utility model, it can adapt to different line resistances, and effectively solve the problem of large deviation of the output voltage accuracy caused by different line impedances of the switching power supply;

4. No digital control chip is used in the circuit of the utility model, which reduces the complexity of the circuit, reduces the development cost, and has advantages in terms of space and cost.

Description of drawings

1 is a schematic diagram of the application of the line loss compensation circuit of the first embodiment of the present invention in a switching power supply;

2 is a schematic diagram of the application of the line loss compensation circuit of the second embodiment of the present invention in a switching power supply;

FIG. 3 is a schematic diagram of the application of the line loss compensation circuit of the third embodiment of the present invention in a switching power supply.

Detailed ways

In order to make the technical solutions of the present invention clearer, the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, and those of ordinary skill in the art make other modifications, replacements or changes to the present invention in various forms without creative work, which still belong to the protection of the present invention. scope.

first embodiment

FIG. 1 is a structural diagram of a line loss compensation circuit according to a first embodiment of the present invention. The line loss compensation circuit in this embodiment includes a sampling amplifying circuit, a voltage dividing circuit and an adding circuit.

The sampling amplifier circuit includes an operational amplifier U1B, a resistor R1 and an adjustable resistor RP1. The non-inverting input terminal of the operational amplifier U1B is used to input the sampling voltage V1, one end of the resistor R1 is grounded, and the other end of the resistor R2 is connected to the inverting input of the operational amplifier U1B at the same time. terminal and one end of the resistor RP1, the output terminal of the op amp U1B and the other end of the resistor RP1 are connected together to output the voltage V2, and the relationship between the voltage V2 and the sampling voltage V1 is as follows:

Among them, R1 is the resistance value of the resistor R1, and RP1 is the resistance value of the resistor RP1.

The voltage divider circuit includes a resistor R3 and a resistor R4. One end of the resistor R3 is used to input the voltage V2, and the other end of the resistor R3 is connected to one end of the resistor R4 to output the divided voltage V3. The other end of the resistor R4 is grounded, and the divided voltage is The relationship between V3 and voltage V2 is as follows:

Among them, R3 is the resistance value of the resistor R3, and R4 is the resistance value of the resistor R4.

The adding circuit includes resistor R5, resistor R6, resistor R7, resistor R8 and op amp U1A. One end of resistor R5 is used to input the divided voltage V3, and the other end of resistor R5 is connected to one end of resistor R6 and the inverting input of op amp U1A at the same time. The other end of the resistor R6 is used to input the reference voltage VREF, one end of the resistor R7 is connected to one end of the resistor R8 and the non-inverting input end of the op amp U1A at the same time, the other end of the resistor R7 is grounded, and the other end of the resistor R8 is connected to the op amp U1A. The outputs are connected together for the output voltage Vf.

The application scheme of the line loss compensation circuit of this embodiment in the switching power supply is as follows: the sampling voltage V1 input by the line loss compensation circuit is the output voltage sampling signal or the output current sampling signal of the switching power supply, and the voltage loop of the switching power supply includes resistors R9, Resistor R10, op amp U1C and isolation feedback optocoupler OC1, one end of resistor R9 is connected to the output voltage Vo of the switching power supply and pin A of the isolation feedback optocoupler OC1 at the same time, the other end of resistor R9 is connected to one end of resistor R10 and the op amp at the same time The reverse input terminal of U1C, the other end of the resistor R10 is grounded, the non-inverting input terminal of the operational amplifier U1C is connected to the output terminal of the operational amplifier U1A, and the output terminal of the operational amplifier U1C is connected to the K pin of the isolation feedback optocoupler OC1, and the isolation feedback optocoupler The C pin of OC1 is connected to the output voltage feedback signal FB of the switching power supply, and the E pin of the isolated feedback optocoupler OC1 is grounded.

The voltage Vf output by the output terminal of the operational amplifier U1A of the utility model is used as the reference voltage of the switching power supply voltage loop to adjust the output voltage Vo of the switching power supply. The working principle is as follows:

In order to facilitate debugging and calculation, if the resistance values of resistor R5, resistor R6, resistor R7 and resistor R8 are the same, the calculation formula of the voltage output by the output terminal of op amp U1A is as follows:

Vf=VREF+V3...Formula (3)

Where VREF is the voltage value of the reference voltage;

The formula for calculating the output voltage Vo of the switching power supply is:

The calculation formula of sampling voltage V1 is:

V1=I _O R _REF ... Formula (5)

Wherein I _O is the output current of the switching power supply, and R _REF is the resistance value of the sampling resistor that samples the output current of the switching power supply;

Simultaneous formulas (1)(2)(3)(4)(5) can be obtained, and the output voltage formula of the switching power supply is as follows:

和设备端电压

It can be seen from formula (6) that the output voltage VO of the switching power supply is composed of two parts, namely the line loss voltage

and device terminal voltage

In addition, it can also be seen from formula (6) that the output voltage of the switching power supply has nothing to do with the output current. The resistance value RP1 of the adjustable resistor can be adjusted once. After the resistance value RP1 of the adjustable resistor is adjusted, the switching power supply will automatically adjust the output voltage no matter how the output current changes, so that the voltage provided to the device terminal remains unchanged.

The debugging method of the resistance value RP1 of the adjustable resistor is as follows:

Since the line loss voltage is equal to the product of the cable impedance and the output current of the switching power supply, that is:

Among them, ΔV is the line loss voltage drop from the output end of the switching power supply to the device end, and R _LOSS is the impedance from the output end of the switching power supply to the device. Therefore, the calculation formula of the resistance value of the adjustable resistor RP1 is as follows:

It can be seen from formula (8) that RP1 is a fixed value, and RP1 is not affected by the output current and line impedance. It can also be concluded that when the line impedance is fixed, RP1 is a fixed value. When the load current of the switching power supply changes, it will automatically The output voltage is adjusted so that the voltage at the device end remains constant.

Second Embodiment

2 is a schematic diagram of the application of the line loss compensation circuit of the second embodiment of the present invention in the switching power supply. The difference between this embodiment and the first embodiment is that the voltage divider circuit is removed, and the compensation range can be further increased. Amplification, for the occasion where the impedance between the power output terminal and the device terminal is large, the compensation amount needs to be increased. At this time, the voltage V1 output by the sampling amplifier circuit can be directly used as the compensation voltage.

Third Embodiment

3 is a schematic diagram of the application of the line loss compensation circuit in the switching power supply according to the third embodiment of the present invention. The difference between this embodiment and the first embodiment is that the adjustable resistor RP1 is replaced with a fixed resistance value. Resistor R2. This embodiment is suitable for the situation where the line impedance is fixed. Changing the adjustable resistance to a fixed resistance can reduce the change of the resistance value of the adjustable resistance caused by external mechanical force, increase the consistency of the switching power supply, and improve the compensation accuracy and stability of the switching power supply. sex.

The above is only to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail according to the embodiments, those of ordinary skill in the art can modify or replace the specific embodiments of the present invention. Any modification or replacement that departs from the spirit and scope of the present invention is within the protection scope of the claims of the present invention.

Claims (9)

1. A line loss compensation circuit, applied to a switching power supply, is characterized in that, comprising: a sampling amplifying circuit and an adding circuit; The sampling amplifying circuit is used to input the sampling voltage V1 reflecting the output condition of the switching power supply, and output the voltage V2 after amplifying; The adding circuit is used for adding the voltage V2 and the reference voltage VREF to output a voltage Vf, and the voltage Vf is used as the reference voltage of the switching power supply voltage loop. 2 . The line loss compensation circuit according to claim 1 , wherein the sampling voltage V1 is a voltage obtained by sampling the output voltage of the switching power supply, or a voltage obtained by sampling the output current of the switching power supply. 3 . 3. line loss compensation circuit according to claim 1 is characterized in that: described sampling amplifying circuit comprises operational amplifier U1B, resistance R1 and resistance R2, the non-inverting input end of operational amplifier U1B is used for inputting sampling voltage V1, resistance One end of R1 is grounded, the other end of resistor R2 is connected to the inverting input end of op amp U1B and one end of resistor R2 at the same time, the output end of op amp U1B and the other end of resistor R2 are connected together to output voltage V2. 4 . The line loss compensation circuit according to claim 3 , wherein the resistor R2 is an adjustable resistor. 5 . 5. The line loss compensation circuit according to claim 1, further comprising: a voltage divider circuit; The voltage divider circuit is used to divide the voltage V2 and output the divided voltage V3; The adding circuit is used for adding the divided voltage V3 and the reference voltage VREF to output a voltage Vf, and the voltage Vf is used as the reference voltage of the switching power supply voltage loop. 6. The line loss compensation circuit according to claim 5, wherein the voltage divider circuit comprises a resistor R3 and a resistor R4, one end of the resistor R3 is used for the input voltage V2, the other end of the resistor R3 and the resistor R4 One end is connected together to output the divided voltage V3, and the other end of the resistor R4 is grounded. 7. The line loss compensation circuit according to claim 6, wherein: The sampling amplifying circuit includes an operational amplifier U1B, a resistor R1 and a resistor RP1. The non-inverting input terminal of the operational amplifier U1B is used to input the sampling voltage V1, one end of the resistor R1 is grounded, and the other end of the resistor R2 is connected to the inverting phase of the operational amplifier U1B at the same time. The input end and one end of the resistor R2, the output end of the operational amplifier U1B and the other end of the resistor R2 are connected together to output the voltage V2. 8. The line loss compensation circuit according to any one of claims 1 to 7, wherein the adding circuit comprises a resistor R5, a resistor R6, a resistor R7, a resistor R8 and an operational amplifier U1A, and one end of the resistor R5 is used for For the input voltage divider V3, the other end of the resistor R5 is connected to one end of the resistor R6 and the inverting input end of the operational amplifier U1A at the same time, the other end of the resistor R6 is used to input the reference voltage VREF, and one end of the resistor R7 is connected to one end of the resistor R8. With the non-inverting input terminal of the operational amplifier U1A, the other end of the resistor R7 is grounded, and the other end of the resistor R8 is connected with the output terminal of the operational amplifier U1A for the output voltage Vf. 9 . The line loss compensation circuit according to claim 8 , wherein the resistance values of the resistor R5 , the resistor R6 , the resistor R7 and the resistor R8 are the same. 10 .

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