Primary-side feedback switching power supply and its line loss compensation circuit, control chip

Abstract

This invention provides a primary-side feedback switching power supply and its line loss compensation circuit and control chip, relating to the field of switching power supply technology. The line loss compensation circuit includes N first compensation modules and second compensation modules. Each first compensation module generates a first current signal based on a first voltage signal or a second voltage signal linearly proportional to the switching frequency of the switching power supply in constant voltage mode, and its corresponding first resistor and first current source. The second compensation module generates a second current signal based on the first voltage signal and the second resistor, and provides segmented line compensation current to the feedback terminal of the switching power supply based on the N first and second current signals. This invention can effectively improve the line loss compensation effect of the line terminal voltage, thereby improving the constant voltage accuracy.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, specifically to a primary-side feedback switching power supply and its line loss compensation circuit and control chip. Background Technology

[0002] Primary-side feedback (PSR) switching power supply control technology is widely used in fields such as mobile phone chargers. Figure 1 This is a schematic diagram of a commonly used PSR switching power supply, including the primary winding, secondary winding, and auxiliary winding located in the primary section. The battery and charger are typically connected by a wire of a certain length, which will result in the line-terminal voltage V supplied to the battery. o This will cause a voltage drop, which may lead to charging failure. Summary of the Invention

[0003] This invention provides a primary-side feedback switching power supply and its line loss compensation circuit and control chip, which can effectively improve the line loss compensation effect of the line terminal voltage, thereby improving the constant voltage accuracy.

[0004] To address the aforementioned problems, this invention discloses a line loss compensation circuit applied to a primary-side feedback switching power supply. The line loss compensation circuit includes:

[0005] N first compensation modules, each first compensation module is used to generate a first current signal based on a first voltage signal that is linearly proportional to the switching frequency of the switching power supply in constant voltage mode or a second voltage signal that is linearly proportional to the switching frequency of the switching power supply in constant voltage mode, and their respective first resistors and first current sources; N≥1.

[0006] The second compensation module generates a second current signal based on the first voltage signal and the second resistor, and generates a line compensation current in segments based on N first current signals and second current signals to compensate the feedback terminal of the switching power supply.

[0007] According to some embodiments, the first voltage signal and the second voltage signal are equal in steady state.

[0008] According to some embodiments, I1 (n)* R1 (n) >I1 (n-1)* R1 (n-1) ...>I1 (1)* R1 (1) , where I1 (n) This represents the current value generated by the first current source corresponding to the nth first compensation module among the N first compensation modules, where * represents the product, R1 (n)This represents the resistance value of the first resistor corresponding to the nth first compensation module out of N first compensation modules, where the value of n ranges from 1 to n to N.

[0009] According to some embodiments, N≥2.

[0010] According to some embodiments, the line compensation current flows from the line loss compensation circuit to the feedback terminal;

[0011] Alternatively, the line compensation current flows from the feedback terminal to the line loss compensation circuit.

[0012] According to some embodiments, the second compensation module includes: a second current generating unit and a second current source;

[0013] The second current generating unit is used to generate a second current signal Ifb2 based on the input first voltage signal, the second resistor, and the current value generated by the second current source; wherein, I1 (1)* R1 (1) >I2*R2, where I2 is the current value generated by the second current source and R2 is the resistance value of the second resistor.

[0014] According to some embodiments, the first compensation module includes: a first current source and a first current generating unit, wherein the first current generating unit is connected to the first current source; wherein the first current generating unit is used to transmit a first current signal to a node in the second compensation module that outputs a second current signal based on a first voltage signal or a second voltage signal and the current value generated by the corresponding first resistor and the first current source.

[0015] According to some embodiments, the first current generating unit includes: a first operational amplifier, a first resistor, a first switch, and a first current mirror; the first input terminal of the first operational amplifier is connected to a first voltage signal or a second voltage signal, and the second input terminal is grounded through the first resistor and connected to a first current source; the gate of the first switch is connected to the output terminal of the first operational amplifier, the source terminal is connected to the second input terminal of the first operational amplifier, and the drain terminal is connected to the input branch of the first current mirror; the output branch of the first current mirror is used to output a first current signal.

[0016] According to some embodiments, the second current generating unit includes: a second operational amplifier, a second resistor, a second switch, and a second current mirror; the first input terminal of the second operational amplifier is connected to a first voltage signal, and the second input terminal is grounded through the second resistor and connected to a second current source; the gate of the second switch is connected to the output terminal of the second operational amplifier, the source terminal is connected to the second input terminal of the second operational amplifier, and the drain terminal is connected to the input branch of the second current mirror; the output branch of the second current mirror is used to output a second current signal.

[0017] According to some embodiments, the second compensation module further includes: a line compensation current generation unit, which generates line compensation current in segments based on N first current signals and second current signals and the maximum value of line compensation current.

[0018] According to some embodiments, the line compensation current generating unit includes:

[0019] The third current source is used to generate the maximum value of the line compensation current;

[0020] The third current mirror has an input branch for receiving the current generated based on the first current signal, the second current signal, and the maximum value of the line compensation current, and an output branch for outputting the line compensation current.

[0021] According to some embodiments, the line loss compensation circuit further includes: a first conversion module, which is used to generate a first voltage signal based on a reference voltage, a switching frequency, and a full-load frequency.

[0022] According to some embodiments, the first conversion module includes:

[0023] The frequency-to-voltage unit is used to output a third voltage signal based on the reference voltage, switching frequency, and full-load frequency.

[0024] The filtering unit is used to input a third voltage signal and output a first voltage signal under the control of the switching frequency.

[0025] According to some embodiments, the filtering unit includes a third switch, a fourth switch, an inverter, a first capacitor, and a second capacitor. The first terminal of the third switch is used to receive a third voltage signal, the second terminal of the third switch is grounded through the first capacitor and connected to the first terminal of the fourth switch, and the control terminal of the third switch is used to receive the switching frequency. The second terminal of the fourth switch is grounded through the second capacitor, and the control terminal of the fourth switch is used to receive the signal after the switching frequency has passed through the inverter. The voltage on the second capacitor is the first voltage signal.

[0026] Based on the same inventive concept, embodiments of the present invention also disclose a control chip, including: a feedback terminal and a line loss compensation circuit as described in embodiments of the present invention.

[0027] Based on the same inventive concept, this invention also discloses a primary-side feedback switching power supply, characterized in that it includes the control chip described in this invention embodiment.

[0028] The embodiments of the present invention have the following advantages:

[0029] This invention proposes a line loss compensation circuit for a primary-side feedback switching power supply. The line compensation current is output as multiple continuous segments with continuous nodes between each segment, used to fit a cubic equation relating the line compensation current to the switching frequency. Thus, when compensating the feedback terminal of the switching power supply control chip using the line compensation current, the influence of the switching frequency and the primary-side peak current on the output current is simultaneously considered. This allows for adaptive line loss compensation based on output current changes, effectively improving the line loss compensation effect on the line terminal voltage and thereby enhancing constant voltage accuracy. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0031] Figure 1 This is a schematic diagram of a commonly used primary-side feedback switching power supply;

[0032] Figure 2a This is a diagram comparing the line terminal voltage with and without line loss compensation under ideal conditions. Figure 1 ;

[0033] Figure 2b This is a schematic diagram comparing the line terminal voltage with and without line loss compensation under ideal conditions (Figure 2).

[0034] Figure 3a This is a comparison of the line terminal voltage with and without line loss compensation in existing technologies. Figure 1 ;

[0035] Figure 3b Figure 2 is a comparison of the line terminal voltage with and without line loss compensation in the existing technology.

[0036] Figure 4 The switching frequency and V proposed in some embodiments of the present invention cs Relationship diagram;

[0037] Figure 5 This is a schematic diagram of the relationship curve between the line compensation current and the switching frequency using a cubic equation proposed in some embodiments of the present invention;

[0038] Figure 6 This is a schematic diagram of the line loss compensation circuit proposed in some embodiments of the present invention;

[0039] Figure 7 V is one of the embodiments of the present invention. cap_fsw_fb A schematic diagram showing the relationship between the switching frequency f and the frequency f.

[0040] Figure 8 This is a schematic diagram of the line compensation structure where the line compensation current flows into the feedback terminal;

[0041] Figure 9 This is a schematic diagram of segmented output of line-compensated current in some embodiments of the present invention. Figure 1 ;

[0042] Figure 10 This is a schematic diagram of the line compensation structure where the line compensation current flows out of the feedback terminal;

[0043] Figure 11 This is a schematic diagram of segmented output of line-compensated current in some embodiments of the present invention (II).

[0044] Figure 12 This is a schematic diagram comparing the line terminal voltage with line loss compensation in some embodiments of the present invention with the line terminal voltage with line loss compensation in the prior art.

[0045] Figure 13 This is a circuit diagram of a line loss compensation circuit proposed in some embodiments of the present invention;

[0046] Figure 14 This is a circuit diagram of a line loss compensation circuit proposed in other embodiments of the present invention;

[0047] Figure 15 This is a circuit diagram of a line loss compensation circuit proposed in some embodiments of the present invention;

[0048] Figure 16 This is a schematic diagram of the line loss compensation circuit proposed in other embodiments of the present invention;

[0049] Figure 17 This is a schematic diagram of the structure of the first conversion module in some embodiments of the present invention.

[0050] Explanation of reference numerals in the attached figures:

[0051] FB - Feedback terminal, CV - Constant voltage mode, CC - Constant current mode;

[0052] CV_1 - The change of line terminal voltage with output current without loss compensation; CV_2 - The change of line terminal voltage with output current with line loss compensation in an ideal system; CV_3 - The change of line terminal voltage with output current with line loss compensation in the prior art; CV_4 - The change of line terminal voltage with output current with line loss compensation in this invention.

[0053] Ifb1_n represents the first current signal output by the nth first compensation module, and Ifb2 represents the second current signal. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0055] Hereinafter, the terms "second," "first," etc., are used for descriptive convenience only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "second," "first," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0056] In this embodiment of the invention, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly, and can refer to direct connection or indirect connection through an intermediate medium.

[0057] In this embodiment of the invention, "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0058] AC / DC (alternating current to direct current) chargers are widely used in mobile phones, tablets, and other fields. Related technologies include line loss compensation techniques to compensate for the voltage V at the line terminals caused by the conductor. o Loss, causing the line terminal voltage V o It remains unchanged. Figure 2a and Figure 2b These are the line terminal voltages V with no loss compensation. o And the line terminal voltage V with line loss compensation o Two contrasting diagrams, in Figure 2a and Figure 2b In the middle, the line terminal voltage V without loss compensation o With output current I out The change is represented by CV_1, which is the ideal line terminal voltage V with line loss compensation. o With output current I out The change is represented by CV_2.

[0059] However, during the creation of this invention, it was discovered that... Figure 2a and Figure 2b The CV_2 shown is only an ideal state, based on existing line loss compensation techniques. Figure 2a Compensated line terminal voltage V o With output current I out The actual relationship is as follows Figure 3a As shown in CV_3, Figure 2bCompensated line terminal voltage V o With output current I out The actual relationship is as follows Figure 3b As shown in CV_3, it can be seen that with the output current I... out Changes in line terminal voltage V o Significant fluctuations affect the accuracy of constant pressure.

[0060] In various embodiments of the present invention, the unit of voltage can be expressed in volts (V), millivolts (mV), etc., the unit of current can be expressed in amperes (A), milliamperes (mA), etc., and the unit of frequency can be expressed in hertz (Hz). The present invention is not limited thereto. Figure 2a , Figure 2b , Figure 3a , Figure 3b In the middle, the line terminal voltage V o The unit is represented by volts (V), and the output current I is... out The unit is indicated by amperes (A), but this does not constitute a limitation on the magnitude of its voltage and current.

[0061] in, Figure 2a , Figure 2b , Figure 3a , Figure 3b In the diagram, the dashed line segment indicates that when the device is started up, the output voltage begins to rise from 0V, and the constant current and constant voltage functions have not yet been activated.

[0062] The concept of line loss compensation in this invention will be explained below.

[0063] like Figure 1 As shown, in constant voltage mode (denoted by CV in the various figures), the line terminal voltage V o The calculation formula is: Formula (1); where V o V is the line terminal voltage. out V is the output voltage. b For example Figure 1 The rectifier diode voltage I between the secondary winding and capacitor C02 is shown. out For the output current, R cable This is the equivalent resistance of the secondary output wire.

[0064] exist Figure 1 In a switching power supply, the primary winding, secondary winding, and auxiliary winding N are all included. aux The primary side portion of the control chip may include the primary winding N. p 1. Capacitor C4, Resistor R3, MOS switch Q5, Current sampling resistor R cs The components include diode D3, capacitor C3, and resistors Rx and Ry. The secondary side may include secondary winding N. sCapacitor C2. The control chip can be connected to the primary side of the switching power supply via its power supply terminal VDD, feedback terminal FB, control terminal GATE, and current sampling terminal CS. For specific connection instructions, please refer to [reference needed]. Figure 1 The schematic diagram can also be referenced from schematic diagrams of other existing switching power supply structures, but these are not part of the present invention and will not be elaborated upon here. AC-VIN represents the input voltage of the switching power supply. In the various figures of this invention, GND represents ground.

[0065] Line loss compensation is essentially compensating for the voltage loss on the line, specifically the line loss voltage V. S =I out *R cable In the constant voltage mode of a switching power supply, it is desirable to minimize the line loss voltage V. S Minimize it so that the line terminal voltage V o =V out -V b However, in constant voltage mode, the output voltage V out Keep constant, while the output current I out It changes according to the load; when the output current I... out At different times, line loss voltage V S They are also different, and the final output line terminal voltage V o They are also different. Therefore, the output current I out The magnitude of the line loss significantly affects the final line loss compensation effect.

[0066] Ideally, the input power of the primary winding of the switching power supply is equal to the output power of the secondary winding. Therefore, according to the law of conservation of energy, we have... Formula (2), where, For the conversion efficiency of the switching power supply, L p I is the inductance of the primary winding. pk Here, f represents the peak current of the primary winding, and f is the switching frequency. The switching frequency f of a switching power supply can be understood as... Figure 1 The switching frequency of the MOS switch Q5.

[0067] Obviously, when the switching power supply operates in constant voltage mode, the output voltage remains basically constant, and the output current I... out The output current I is affected by the peak current of the primary winding and the switching frequency f. out It has a quadratic relationship with the peak current and a first-order relationship with the switching frequency f. For example, when the switching power supply control chip operates in PFM (Pulse Frequency Modulation) mode, it will simultaneously adjust the switching frequency f and the peak current of the primary winding to meet the power change requirements.

[0068] refer to Figure 4 This invention enables , formula (3), , where V cs It reflects R cs The voltage drop across the circuit, where a and b are constants, f is the switching frequency, and V cs_max V represents cs The maximum value, V cs_min V represents cs The minimum value of f0. When f0 ≤ f ≤ f1, the switching power supply is in constant voltage mode; when f > f1, the switching power supply is in constant current mode, and f0 is V. cs_min The corresponding switching frequency. And because... Formula (4), where, in power MOS (such as Figure 1 When Q5 is enabled, V cs It will increase linearly, reaching a level based on V. cap_fsw_cs When the set reference voltage is reached, the chip will turn off the power MOSFET. Based on formulas (1)-(4), we can obtain:

[0069] , formula (5).

[0070] Due to the line terminal voltage V o Much greater than the line loss voltage V S That is, much larger than I out *R cable Therefore, formula (5) can be further transformed into: Formula (6). Based on formula (6), it can be seen that when V o and V b At a given time, the output current I out It has a cubic relationship with the switching frequency f.

[0071] Based on such Figure 1 The switching power supply shown has a structure where the number of turns in the secondary winding is proportional to the number of turns in the auxiliary winding. Therefore, the output voltage V... out The feedback terminal voltage of the control chip of the switching power supply Vref It also satisfies a certain relationship, as shown in formula (7):

[0072] , formula (7), The calculated result is a constant value. Rx This represents the resistance connected between the feedback terminal and the auxiliary winding. Ry This represents the resistor connected between the feedback terminal and ground.

[0073] Therefore, through the line compensation current I cable Feedback terminal voltage of the switching power supply control chip Vref Compensation can be performed to compensate for the output voltage, that is, to compensate for the line terminal voltage V. oCompensation.

[0074] Due to line loss voltage V S =I out *R cable Output current I out The output line compensation current I is related to the cubic relationship with the switching frequency f. cable Theoretically, it should also satisfy this cubic relationship with the switching frequency f, so that the output current I can be adaptively adjusted. out The change in line loss voltage V compensates for the change in line loss voltage V. S The resulting line terminal voltage V o Loss. In other words, due to the output current I out The relationship between the current and the switching frequency f is cubic. Therefore, by providing a line compensation current I to the feedback terminal that also has the same cubic relationship with the switching frequency f, a solution can be found. cable (Line compensation current I) cable The relationship curve between the cubic equation and the switching frequency f can be shown as follows: Figure 5 As shown in the figure, it can adaptively output current I. out Line loss compensation is applied to the changes in I, so that regardless of the changes... out How it changes, the final output V o Both are close to V out That is, maintain V o The constant pressure improves the accuracy of constant pressure.

[0075] Based on the above line loss compensation concept, this invention proposes a line loss compensation circuit for primary-side feedback switching power supplies in some embodiments, which compensates for the line loss current I... cable The output consists of multiple continuous segments with continuous nodes between each segment, used to fit the line-complementary current I. cable The relationship curve between the switching frequency f and the cubic equation. Thus, using the line compensation current I... cable When compensating the feedback terminal of the switching power supply control chip, both the switching frequency f and the primary-side peak current I of the switching power supply are taken into account. pk For output current I out The influence can be adaptively applied to the output current I. out The changes in line loss are compensated to effectively improve the line terminal voltage V. o This improves the line loss compensation effect, thereby enhancing the constant voltage accuracy.

[0076] In some embodiments, the structural schematic diagram of the line loss compensation circuit can be as follows: Figure 6As shown, the line loss compensation circuit includes N first compensation modules and second compensation modules, where N≥1. Each first compensation module generates a first current signal based on a first voltage signal that is linearly proportional to the switching frequency f of the switching power supply in constant voltage mode, as well as its corresponding first resistor and first current source. The second compensation module generates a second current signal based on the first voltage signal and the second resistor, and generates a line compensation current Icable segmented based on the N first current signals and the second current signals to compensate the feedback terminal of the switching power supply control chip.

[0077] In such Figure 6 In the illustrated embodiment, the voltage signals input to the first compensation module and the second compensation module are the same, for example, both are the first voltage signal. In some feasible implementations, the first voltage signal can be V... cap_fsw_fb In other feasible implementations, the first voltage signal may be V. cap_fsw_cs In constant voltage mode, the first voltage signal is linearly proportional to the switching frequency f. Let the first voltage signal be V. cap_fsw_fb For example, V cap_fsw_fb The relationship with the switching frequency f can be referenced. Figure 7 When f2 ≤ f ≤ f1, V cap_fsw_fb The switching frequency f has a linear relationship with the first power, increasing as f increases; when the switching frequency f > f1, the switching power supply is in constant current mode. Here, f1 and f2 are set frequency thresholds, and f2 ≤ f0.

[0078] In the accompanying diagrams, Ifb1_n represents the first current signal output by the nth first compensation module, where n ranges from 1 to n to N. For example, the first current signal output by the first first compensation module is Ifb1_1, the first current signal output by the second first compensation module is Ifb1_2, the first current signal output by the third first compensation module is Ifb1_3, and so on. That is, the N first compensation modules actually generate a total of N first current signals, namely Ifb1_1, Ifb1_2, Ifb1_3, ..., Ifb1_n.

[0079] The line loss compensation circuit in this embodiment is designed with N first compensation modules and second compensation modules. Since the first voltage signal is linearly proportional to the switching frequency f, and the first current signal output by the first compensation module and the second current signal generated by the second compensation module are both based on the first voltage signal, both the first current signal and the second current signal are related to the switching frequency f. Furthermore, the second compensation module outputs a line compensation current I based on N first current signals and second current signals. cable This establishes the relationship between the switching frequency f and the line compensation current I. cable The relationship between the N first current signals and the second current signals. Together, they determine the line compensation current I.cable Relative to the number of inflection points at the switching frequency f, the line loss compensation circuit can thus output multiple segments of continuous line compensation current I between each segment. cable Used for fitting line compensation current I cable The relationship curve between the cubic equation and the switching frequency f is used to compensate the feedback terminal, thereby achieving control over the line terminal voltage V. o Line loss compensation. Based on this fitting idea, essentially the larger the number of N, the better the fitting effect, i.e., the line compensation current I... cable The closer the segments corresponding to the switching frequency f are to the relationship curve of the cubic equation, the better. Line compensation current I cable One implementation of the cubic equation relating the switching frequency f to the curve is as follows: Figure 5 As shown.

[0080] In one feasible implementation, the line compensation current I cable The feedback terminal FB of the switching power supply control chip is a pull-up current, and the line compensation structure is as follows: Figure 8 As shown. Line compensation current I cable The current flows from the line loss compensation circuit to the feedback terminal, and then out through the feedback terminal FB to the outside of the chip. This sampled feedback terminal voltage... Vref Higher than the actual value, there are:

[0081] , formula (8);

[0082] Right now, , formula (9).

[0083] In each formula, / / represents the parallel connection symbol, Rx / / Ry indicates that resistors Rx and Ry are connected in parallel, and I cable (Rx / / Ry) represents I cable Multiply by the resistance value (Rx / / Ry) to get the line compensation voltage.

[0084] To ensure the line terminal voltage V o Under constant voltage mode with the output voltage constant across the full load range, i.e., when the output voltage is constant, the line compensation current I... cable With output current I out Inversely proportional, then: when the load is fully loaded, i.e., the output current I... out At its maximum, the line compensation current I cable =0; when the load is unloaded, there is The line compensation current is the maximum, which is max_I. cable Based on this compensation approach, the optional line compensation current I is N≥2. cable The relationship with the switching frequency f is as follows Figure 9 As shown, it is used for fitting such as Figure 5The curve shown represents the cubic equation relating the line compensation current I to the switching frequency f. In this curve, the line compensation current I... cable It is inversely proportional to the switching frequency f.

[0085] In another feasible implementation, the line compensation current I cable The feedback terminal FB of the switching power supply control chip is a pull-down current, and the line compensation structure is as follows: Figure 10 As shown, the line compensation current I cable The current flows from the feedback terminal FB to the line loss compensation circuit, that is, from the feedback terminal FB to the control chip. The sampled Vref is lower than the actual value, therefore:

[0086] , formula (10);

[0087] Right now, , formula (11);

[0088] To ensure the output terminal voltage V o Under constant voltage mode with the output voltage constant across the full load range, i.e., when the output voltage is constant, the line compensation current I... cable With output current I out It is directly proportional. Therefore, when the load is full, the output current I is... out At its maximum, the line compensation current I cable It is also the largest, which is max_I. cable , When the load is unloaded, the output current I out Small, line compensation current I cable The value is 0. Based on this compensation approach, the optional value is N≥2, and the line compensation current I is 0. cable The relationship with the switching frequency f is as follows Figure 11 As shown, it is used to fit the line compensation current I. cable The relationship curve between the cubic equation and the switching frequency f (not shown in the figure) shows the line compensation current I. cable It is directly proportional to the switching frequency f.

[0089] like Figure 9 and Figure 11 As shown, the line compensation current I changes with the switching frequency f. cable It is presented as multiple segments with continuous nodes between each segment, effectively fitting the data such as... Figure 5 The line compensation current I shown cable The relationship curve between the cubic equation and the switching frequency f is used to compensate for the feedback terminal FB, thereby achieving control over the line terminal voltage V. o Line loss compensation. In some embodiments, the line compensation current I cable After compensation at the feedback end, the final output line terminal voltage V in this embodiment is... o With output current Iout Relationship such as Figure 12 As shown in CV_4; Figure 12 CV_3 in the figure shows the line terminal voltage V after compensation using a prior art technique. o With output current I out The relationship. Clearly, compared to the line terminal voltage V after compensation using existing technology... o The waveform (shown as CV_3), and the line terminal voltage V after compensation according to the embodiment of the present invention. o The waveform (denoted by CV_4) is significantly smoother, and is closer to the ideal line-end voltage V with line loss compensation. o waveform (such as) Figure 2a and Figure 2b (CV_2 in the text) increases the output line terminal voltage V. o The constant pressure accuracy.

[0090] Next, taking the first voltage signal as V cap_fsw_fb Taking two first compensation modules and one second compensation module as an example, the circuit of this embodiment will be described.

[0091] In this case, the input terminal of each first compensation module is V. cap_fsw_fb Each first compensation module is connected to a corresponding first resistor and a first current source. A first compensation module may include a first current source and a first current generation unit, with the first current generation unit connected to the corresponding first current source. The first current generation unit generates a first current signal Ifb1_n based on the first voltage signal and the current value generated by its corresponding first resistor and first current source. The first current signals Ifb1_n generated by each of the N first compensation modules eventually flow to the second compensation module. If the output terminals of all N first compensation modules are connected to the node in the second compensation module used to output the second current signal Ifb2, the first current signal Ifb1_n flows to the node in the second compensation module used to output the second current signal Ifb2 to compensate for the second current signal Ifb2. This changes the current line compensation current I. cable The slope of the line compensation current I cable Compared to the inflection point generated by the switching frequency f, this enables the compensation current I in the line. cable The segmentation.

[0092] In this case, the product of the first resistor and the first current source corresponding to each first compensation module is different, which can distinguish the line compensation current I. cable Different segments. Optional, II1 (n)* R1 (n) >I1 (n-1)* R1 (n-1) ...>I1 (1)* R1 (1), where I1 (n) This represents the current value generated by the first current source corresponding to the nth first compensation module out of N first compensation modules, where * indicates product, R1 (n) This represents the resistance value of the first resistor corresponding to the nth first compensation module out of N first compensation modules.

[0093] by Figure 13 and Figure 14 Taking the structure shown as an example, the calculation method of the first current generation unit in the first compensation module based on the first current signal generated by its corresponding first resistor and first current source is explained. (Reference) Figure 13 and Figure 14 The first current generating unit may include a first operational amplifier, a first resistor, a first switch, and a first current mirror; wherein, the first input terminal of the first operational amplifier is connected to a voltage V. cap_fsw_fb The second input terminal is grounded through the first resistor and connected to the first current source; the gate of the first switch is connected to the output terminal of the first operational amplifier, the source is connected to the second input terminal of the first operational amplifier, and the drain is connected to the input branch of the first current mirror; the output branch of the first current mirror is used to supply power to the node in the second compensation module that outputs the second current signal Ifb2 (in... Figure 13 and Figure 14 In the diagram, this node (represented by Q) outputs the first current signal Ifb1_n.

[0094] The first operational amplifier in the nth first compensation module is shown in the attached figure via A1. (n) This means that the first input terminal can be a non-inverting input terminal, and the second input terminal can be an inverting input terminal. In this structure, Ifb1_n = K1 (n) *(V) cap_fsw_fb / R1 (n) -I1 (n) Formula (12), where K1 (n) This indicates the mirror ratio of the first current mirror in the nth first compensation module. For example:

[0095] In the first compensation module, the resistance value of the corresponding first resistor is R1. (1) The current value generated by the corresponding first current source is I1. (1) The first switch is represented as N1. (1) The first current mirror consists of MOSFETs P5 and P6, and the mirror ratio of the first current mirror is K1. (1) The first current signal Ifb_1 = K1 output by the first compensation module. (1) *(V) cap_fsw_fb / R1 (1) -I1 (1) ).

[0096] In the second first compensation module, the resistance value of the corresponding first resistor is R1. (2) The current value generated by the corresponding first current source is I1. (2) The first switch is represented as N1. (2) The first current mirror consists of MOSFETs P7 and P8, and the mirror ratio of the first current mirror is K1. (2) The first current signal Ifb_2=K1 output by the second compensation module. (2) *(V) cap_fsw_fb / R1 (2) -I1 (2) ).

[0097] The second compensation module may include a second current generation unit and a line compensation current generation unit. The second current generation unit generates a second current signal Ifb2, where Ifb2 ≥ 0. The line compensation current generation unit generates the signal based on N first and second current signals and the maximum line compensation current value max_I. cable Segmented generation of line compensation current I cable This is to compensate the feedback terminal of the switching power supply, thereby achieving control over the line terminal voltage V. o Line loss compensation.

[0098] In some embodiments of this example, the structure for generating the second current signal can be as follows: Figure 13 As shown, the second current generation unit is based on the input V cap_fsw_fb The second current generating unit generates a second current signal Ifb2 using a second resistor. Specifically, the second current generating unit includes a second operational amplifier, a second resistor, a second switch, and a second current mirror. The first input terminal of the second operational amplifier is connected to a first voltage signal, and the second input terminal is grounded through the second resistor. The gate of the second switch is connected to the output terminal of the second operational amplifier, its source is connected to the second input terminal of the second operational amplifier, and its drain is connected to the input branch of the second current mirror. The output branch of the second current mirror is used to output the second current signal Ifb2.

[0099] In this embodiment, the second operational amplifier is represented by A2 in the attached figure. Specifically, the first input terminal can be a non-inverting input terminal, and the second input terminal can be an inverting input terminal. The second switch is represented by N2, and the second current mirror is composed of MOSFETs P1 and P2. Ifb2=K2*(V cap_fsw_fb / R2), formula (13), where K2 represents the mirror ratio of the second current mirror and R2 is the resistance value of the second resistor.

[0100] In other embodiments of this example, the structure for generating the second current signal Ifb2 can also be as follows. Figure 14 As shown in the structure, the second compensation module also includes a second current source. That is, different from... Figure 13 In the illustrated embodiment, a second current source is added. The second current generation unit generates a second current signal Ifb2 based on the input first voltage signal, the second resistor, and the current value generated by the second current source. Specifically, in the second current generation unit, the first input terminal of the second operational amplifier is connected to the first voltage signal, and the second input terminal is grounded through the second resistor and connected to the second current source. The gate of the second switch in the second current generation unit is still connected to the output terminal of the second operational amplifier, the source is connected to the second input terminal of the second operational amplifier, and the drain is connected to the input branch of the second current mirror. The output branch of the second current mirror is used to output the second current signal Ifb2.

[0101] In this implementation, Ifb2 = K2 * (V cap_fsw_fb / R2-I2), formula (14), where K2 represents the mirror ratio of the second current mirror, R2 is the resistance value of the second resistor, I2 is the current value generated by the second current source, I1 (1)* R1 (1) >I2*R2.

[0102] Continue to refer to Figure 13 and Figure 14 The line compensation current generation unit may include a third current source and a third current mirror (in the attached figure, the third current mirror is composed of MOSFETs P3 and P4), wherein the third current source is used to generate the maximum line compensation current max_I. cable The input branch of the third current mirror is connected to node Q, which is used to input the maximum value of the line compensation current max_I based on N first current signals, second current signals Ifb2, and the line compensation current max_I. cable The generated current is used by the output branch to compensate for the output line current I. cable .

[0103] by Figure 14 Taking the structure shown as an example, assume the mirror ratio K3 of the third current mirror is equal to 1. As the switching frequency f changes, that is, as V... cap_fsw_fb The line compensation current generation unit is based on two first current signals Ifb1_1 and Ifb1_2, a second current signal Ifb2, and the maximum value of the line compensation current max_I. cable This generates a line compensation current I. cable The piecewise function is shown in the following formula:

[0104] , formula (15).

[0105] The line compensation current I corresponding to this piecewise function cable The relationship with the switching frequency f can be referenced. Figure 9 :

[0106] when At that time, the second switch N2 and the first switch N1 corresponding to the first compensation module (1) The first switch N1 corresponding to the second first compensation module (2) Both are in the off state, and the line compensation current I cable For max_I cable The corresponding segments are as follows Figure 9 As shown in L1;

[0107] when When the second switch N2 is turned on, the first switch N1 corresponding to the first compensation module is turned on. (1) The first switch N1 corresponding to the second first compensation module (2) Both are in the off state, and the line compensation current I cable for The corresponding segments are as follows Figure 9 As shown in L2;

[0108] when At that time, the second switch N2 and the first switch N1 corresponding to the first compensation module (1) The first switch N1 corresponding to the second first compensation module is turned on. (2) When in the off state, the line compensation current I cable for:

[0109] The corresponding segments are as follows Figure 9 As shown in L3;

[0110] when At that time, the second switch N2 and the first switch N1 corresponding to the first compensation module (1) The first switch N1 corresponding to the second first compensation module (2) All are conducting, line compensation current I cable for:

[0111] The corresponding segments are as follows Figure 9 As shown in L4.

[0112] When V cap_fsw_fb >max_V set At that time, the line compensation current I cable Reduced to 0, the corresponding segment is as follows Figure 9 As shown in L5 of the diagram. max_V set This is the set value.

[0113] above Figure 13 and Figure 14 In the disclosed embodiments, the first voltage signal connected to the first compensation module and the second compensation module is the same, and the first voltage signal connected to both is V. cap_fsw_fbIn other embodiments, the first voltage signal may also be V. cap_fsw_cs .

[0114] Figure 13 and Figure 14 The difference lies in whether the second compensation module includes a second current source, which makes Ifb2 slightly different, where Ifb2≥0.

[0115] Figure 13 and Figure 14 The circuit structure shown corresponds to Figure 8 The line compensation structure shown has a line compensation current I. cable The flow goes from the line loss compensation circuit to the feedback terminal FB. Of course, for... Figure 10 The line compensation structure shown continues with N=2 as an example, the line compensation current I cable A schematic diagram showing the flow from the feedback terminal FB to the line loss compensation circuit can be seen as follows: Figure 15 As shown, in Figure 15 In the middle, the third current mirror is composed of MOSFETs N3 and N4, and the line compensation current I... cable The relationship with the switching frequency f can be referenced. Figure 11 .

[0116] when At that time, the second switch N2 and the first switch N1 corresponding to the first compensation module (1) The first switch N1 corresponding to the second first compensation module (2) Both are in the off state, and the line compensation current I cable If it is 0, the corresponding segment is as follows: Figure 11 As shown in L1;

[0117] when When the second switch N2 is turned on, the first switch N1 corresponding to the first compensation module is turned on. (1) The first switch N1 corresponding to the second first compensation module (2) Both are in the off state, and the line compensation current I cable for The corresponding segments are as follows Figure 11 As shown in L2;

[0118] when At that time, the second switch N2 and the first switch N1 corresponding to the first compensation module (1) The first switch N1 corresponding to the second first compensation module is turned on. (2) When in the off state, the line compensation current I cable for: The corresponding segments are as follows Figure 11 As shown in L3;

[0119] when At that time, the second switch N2 and the first switch N1 corresponding to the first compensation module (1) The first switch N1 corresponding to the second first compensation module (2) All are conducting, line compensation current I cable for:

[0120] This segment is as follows Figure 11 As shown in L4;

[0121] When V cap_fsw_fb >max_V set At that time, the line compensation current I cable For max_I cable The corresponding segments are as follows Figure 11 As shown in L5 of the diagram. max_V set This is the set value.

[0122] In other embodiments, the structural schematic diagram of the line loss compensation circuit of the present invention can be as follows: Figure 16 As shown, the line loss compensation circuit includes N first compensation modules and second compensation modules, where N ≥ 1. Each first compensation module generates a first current signal based on a second voltage signal linearly proportional to the switching frequency f of the switching power supply in constant voltage mode, and its corresponding first resistor and first current source. The second compensation module generates a second current signal Ifb2 based on the first voltage signal and the second resistor, which are also linearly proportional to the switching frequency f of the switching power supply in constant voltage mode, and generates a line compensation current I segmentally based on the N first current signals and second current signals Ifb2. cable This is to compensate the feedback terminal FB of the switching power supply control chip.

[0123] Unlike some of the aforementioned embodiments, in the case of... Figure 16 In the illustrated embodiment, the voltage signals input to the first compensation module and the second compensation module are different, which can be understood as two signals. Optionally, the first voltage signal is V. cap_fsw_fb The second voltage signal is V cap_fsw_cs Alternatively, the first voltage signal is V. cap_fsw_cs The second voltage signal is V cap_fsw_fb .

[0124] In the actual circuit, the first voltage signal and the second voltage signal may be equal or unequal, depending on the design requirements. In some optional embodiments, the first voltage signal and the second voltage signal are equal in steady state.

[0125] Other related explanations of this embodiment can be found in the foregoing embodiments, and will not be repeated here. The circuit structures of the first compensation module and the second compensation module can also be found in... Figure 13-15The key point of this embodiment is to emphasize that the voltage signals input to the first compensation module and the second compensation module are different. Correspondingly, as shown below... Figures 13-15 The structure shown illustrates that when the voltage connected to the first operational amplifier in the first compensation module is V... cap_fsw_fb When the voltage is V, the voltage connected to the second operational amplifier in the second compensation module is V. cap_fsw_cs When the voltage connected to the first operational amplifier in the first compensation module is V cap_fsw_cs When the voltage is V, the voltage connected to the second operational amplifier in the second compensation module is V. cap_fsw_fb .

[0126] In this embodiment, since both the first and second voltage signals are linearly proportional to the switching frequency f, and the first current signal is generated based on the second voltage signal, and the second current signal is generated based on the first voltage signal, both the first and second current signals are related to the switching frequency f. Furthermore, the second compensation module outputs a line compensation current I based on N first current signals Ifb1_n and second current signals Ifb2. cable This establishes the relationship between the switching frequency f and the line compensation current I. cable The relationship between the N first current signals and the second current signal Ifb2 together determines the line compensation current I. cable Relative to the number of inflection points at the switching frequency f, the line loss compensation circuit can thus output multiple segments of continuous line compensation current I between each segment. cable Used for fitting line compensation current I cable The relationship curve between the cubic equation and the switching frequency f is used to compensate for the feedback terminal FB. Based on this fitting idea, essentially, the larger the number of N, the better the fitting effect, i.e., the line compensation current I... cable The closer the segments corresponding to the switching frequency f are to the relationship curve of the cubic equation, the better.

[0127] In this embodiment of the invention, the first voltage signal is V. cap_fsw_fb The second voltage signal is V cap_fsw_cs Taking this as an example, we will explain the differences between the two and their respective implementation circuits.

[0128] The line loss compensation circuit in this embodiment may further include a first conversion module, which generates a first voltage signal V based on the reference voltage, switching frequency, and full-load frequency. cap_fsw_fb Among them, reference Figure 17 The first conversion module may include: a frequency-to-voltage unit, used to output a third voltage signal based on a reference voltage, a switching frequency, and a full-load frequency; and a filtering unit, used to input the third voltage signal and output V under the control of the switching frequency. cap_fsw_fb .

[0129] The reference voltage, amplified by a buffer amplifier, is input to the frequency-to-voltage conversion unit. This reference voltage is a set value; therefore, the first voltage signal V... cap_fsw_fb It is an absolute voltage generated based on the switching frequency, and its voltage value is only related to the switching frequency f. It can effectively reflect changes in the switching frequency f, such as increasing as the switching frequency increases. First voltage signal V cap_fsw_fb The value ranges from 0 to the reference voltage. For example, if the reference voltage is 2V, then 0 ≤ V. cap_fsw_fb ≤2V.

[0130] exist Figure 17 In this context, the full-load frequency is represented by Fset, which is a set value, such as f1. Specifically, it can be compared with the aforementioned max_V. set Corresponding. When f≥Fset, V cap_fsw_fb Equal to the reference voltage; when f < Fset, V cap_fsw_fb It is directly proportional to f; the lower f is, the greater V is. cap_fsw_fb The lower the value. The frequency-to-voltage conversion unit can be implemented using some existing frequency-to-voltage circuits available on the market; this embodiment does not limit its structure. The filtering unit can be implemented using... Figure 17 The structure shown includes a filter unit comprising a third switch S3, a fourth switch S4, an inverter INV, a first capacitor C01, and a second capacitor C02. The first terminal of the third switch S3 is used to receive a third voltage signal. The second terminal of the third switch S3 is grounded via the first capacitor C01 and connected to the first terminal of the fourth switch S4. The control terminal of the third switch S3 is used to receive a switching frequency f. The second terminal of the fourth switch S4 is grounded via the second capacitor C02. The control terminal of the fourth switch S4 is used to receive the signal after the switching frequency f has passed through the inverter. The voltage across the second capacitor C02 is V. cap_fsw_fb The third switch S3 and the fourth switch S4 can be implemented using MOSFETs, and this invention does not limit this implementation.

[0131] If the second voltage signal is V cap_fsw_cs It can also be based on, for example Figure 17 The similar structure shown converts the switching frequency f to V. cap_fsw_cs Among them, due to V cap_fsw_cs It can be used to convert current sampling voltage V cs The reference voltage is V to adapt to changes in the switching frequency f. cs Different reference voltage values ​​are provided. Based on V cap_fsw_cs This function is generally performed when the chip is initially powered on, V cap_fsw_cs With V cap_fsw_fb Different default values ​​are needed. Therefore, V cap_fsw_fb With V cap_fsw_cs Although both are converted through switching frequency f, V cap_fsw_fbWith V cap_fsw_cs Essentially, it consists of two voltage signals. In some application implementations, when the chip enters constant voltage mode, V... cap_fsw_fb From 0V, it gradually builds up to a steady state, which can be compared with V. cap_fsw_cs They become the same voltage.

[0132] Based on the same inventive concept, embodiments of the present invention also provide a control chip, including a feedback terminal FB and the line loss compensation circuit described in the embodiments of the present invention. Furthermore, the line loss compensation circuit uses V... cap_fsw_cs Under the given constraints, the control chip may also include a current sampling terminal CS.

[0133] Based on the same inventive concept, embodiments of the present invention also provide a primary-side feedback switching power supply, including the control chip as described in the embodiments of the present invention.

[0134] In summary, this invention provides a line loss compensation circuit for a primary-side feedback switching power supply. This circuit, based on a first or second voltage signal linearly proportional to the switching frequency f, can output a segmented line loss compensation current I corresponding to the switching frequency f. cable The segmented line compensates for the current I. cable Used for fitting line compensation current I cable The relationship curve between the switching frequency f and the cubic equation is shown, and this relationship curve is actually reflected in the output current I. out The relationship between the switching frequency f and the cubic function equation. Thus, the segmented output line compensation current I... cable When compensating the feedback terminal of the switching power supply control chip, both the switching frequency f and the primary-side peak current I of the switching power supply are taken into account. pk For output current I out The influence can be adaptively applied to the output current I. out The changes in line loss are compensated to effectively improve the line terminal voltage V. o This improves the line loss compensation effect, thereby enhancing the constant voltage accuracy.

[0135] During this process, due to the output current I out As the switching frequency f changes, the line compensation current I also changes. cable This also changes accordingly, thus, the line compensation current I cable Size can vary with I out It adapts to changes and compensates for line loss quickly.

[0136] In the circuit structure of the line loss compensation circuit proposed in this invention, the circuits that generate current in the N first compensation modules and second compensation modules are all independent. For example, each module has its own operational amplifier, resistor, and current source to generate current, which allows for convenient adjustment of the line compensation current I. cableThe slope and starting point are determined to make the circuit simple and occupy a small area.

[0137] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0138] The technical solution provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand this invention, and the content of this specification should not be construed as a limitation of this invention. Furthermore, for those skilled in the art, there will be different forms of changes in the specific implementation methods and application scope based on this invention. It is neither necessary nor possible to exhaustively list all implementation methods here, but obvious changes or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A line loss compensation circuit, characterized in that, The line loss compensation circuit, applied to a primary-side feedback switching power supply, includes: N first compensation modules, each first compensation module is used to generate a first current signal based on a first voltage signal that is linearly proportional to the switching frequency of the switching power supply in constant voltage mode or a second voltage signal that is linearly proportional to the switching frequency of the switching power supply in constant voltage mode, and a corresponding first resistor and a first current source; N≥1; The second compensation module generates a second current signal based on the first voltage signal and the second resistor, and generates a line compensation current in segments based on N first current signals and the second current signals to compensate the feedback terminal of the switching power supply.

2. The line loss compensation circuit according to claim 1, characterized in that, in, The first voltage signal and the second voltage signal are equal in steady state.

3. The line loss compensation circuit according to claim 1 or 2, characterized in that, I1 (n)* R1 (n) >I1 (n-1)* R1 (n-1) ...>I1 (1)* R1 (1) , where I1 (n) This represents the current value generated by the first current source corresponding to the nth first compensation module among the N first compensation modules, where * indicates product, R1 (n) This represents the resistance value of the first resistor corresponding to the nth first compensation module among the N first compensation modules.

4. The line loss compensation circuit according to claim 3, characterized in that, in, N≥2。 5. The line loss compensation circuit according to claim 1, characterized in that, The line compensation current flows from the line loss compensation circuit to the feedback terminal; Alternatively, the line compensation current flows from the feedback terminal to the line loss compensation circuit.

6. The line loss compensation circuit according to claim 3, characterized in that, The second compensation module includes: a second current generating unit and a second current source; The second current generating unit is used to generate a second current signal based on the input first voltage signal, the second resistor, and the current value generated by the second current source; Among them, I1 (1)* R1 (1) >I2*R2, where I2 is the current value generated by the second current source and R2 is the resistance value of the second resistor.

7. The line loss compensation circuit according to claim 1, characterized in that, The first compensation module includes: a first current source and a first current generating unit, wherein the first current generating unit is connected to the first current source; The first current generating unit is used to transmit a first current signal to the node in the second compensation module that outputs the second current signal, based on the first voltage signal or the second voltage signal and the current value generated by the corresponding first resistor and the first current source.

8. The line loss compensation circuit according to claim 7, characterized in that, The first current generating unit includes: a first operational amplifier, a first resistor, a first switch, and a first current mirror; The first input terminal of the first operational amplifier is connected to the first voltage signal or the second voltage signal, and the second input terminal is grounded through the first resistor and connected to the first current source. The gate of the first switch is connected to the output terminal of the first operational amplifier, the source is connected to the second input terminal of the first operational amplifier, and the drain is connected to the input branch of the first current mirror; the output branch of the first current mirror is used to output the first current signal.

9. The line loss compensation circuit according to claim 6, characterized in that, The second current generating unit includes: a second operational amplifier, a second resistor, a second switch, and a second current mirror; The first input terminal of the second operational amplifier is connected to the first voltage signal, and the second input terminal is grounded through the second resistor and connected to the second current source; The gate of the second switch is connected to the output terminal of the second operational amplifier, the source is connected to the second input terminal of the second operational amplifier, and the drain is connected to the input branch of the second current mirror; the output branch of the second current mirror is used to output the second current signal.

10. The line loss compensation circuit according to claim 1, 6, or 9, characterized in that, The second compensation module also includes: The line compensation current generation unit generates the line compensation current in segments based on N first current signals, second current signals, and the maximum value of the line compensation current.

11. The line loss compensation circuit according to claim 10, characterized in that, The line compensation current generating unit includes: A third current source is used to generate the maximum value of the line compensation current; The third current mirror has an input branch for receiving a current generated based on the first current signal, the second current signal, and the maximum value of the line compensation current, and an output branch for outputting the line compensation current.

12. The line loss compensation circuit according to claim 1 or 2, characterized in that, Also includes: The first conversion module is used to generate the first voltage signal based on the reference voltage, the switching frequency, and the full-load frequency.

13. The line loss compensation circuit according to claim 12, characterized in that, The first conversion module includes: A frequency-to-voltage unit is used to output a third voltage signal based on a reference voltage, the switching frequency, and the full-load frequency. A filtering unit is used to input the third voltage signal and output the first voltage signal under the control of the switching frequency.

14. The line loss compensation circuit according to claim 13, characterized in that, The filtering unit includes a third switch, a fourth switch, an inverter, a first capacitor, and a second capacitor. The first terminal of the third switch is used to receive the third voltage signal, the second terminal of the third switch is grounded through the first capacitor and connected to the first terminal of the fourth switch, and the control terminal of the third switch is used to receive the switching frequency. The second terminal of the fourth switch is grounded via the second capacitor, and the control terminal of the fourth switch is used to receive the signal after the switching frequency has passed through the inverter. The voltage across the second capacitor is the first voltage signal.

15. A control chip, characterized in that, include: The feedback terminal FB and the line loss compensation circuit as described in any one of claims 1-14.

16. A primary-side feedback switching power supply, characterized in that, Includes the control chip as described in any one of claims 15.

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