A feed-forward compensation and overcurrent protection method and device, switching power supply and power distribution system

Abstract

The application discloses a feedforward compensation and overcurrent protection method and device, a switching power supply and a power distribution system. in The input voltage sampling signal V in When V in When V in When V in The application can avoid excessive feedforward compensation under high voltage input, and is beneficial to improving the efficiency of the switching power supply and the power distribution system.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a feedforward compensation and overcurrent protection method, device, and switching power supply, as well as a power distribution system having the power switch. Background Art

[0002] With the rapid development of electronic technology, a complete switching power supply control process often needs to include other functions in addition to the necessary main power control circuit, such as input undervoltage protection, feedforward compensation, and over-power point consistency compensation. The simplified block diagram of the overall application circuit of the conventional feedforward compensation circuit topology is as follows Figure 1 As shown, the main power topology is a well-known technology, including input voltage Vin, output voltage Vout, capacitor C1, voltage divider resistors Ruvp1 and Ruvp2, control IC, main power transformer, main power tube MN POWER , sampling resistor Rcs, diode Drec, capacitor C2, output inductor L out And capacitor C3, etc. The GTL pin is the driver output of the controller IC, which is used to control the power tube MN POWER The FB pin is the optocoupler feedback pin. When the output voltage Vout increases, the optocoupler current increases and the FB pin voltage decreases. On the contrary, when the output voltage Vout decreases, the optocoupler current decreases and the FB pin voltage increases. The CSOUT pin is the current sampling pin. CS The voltage flowing through the power tube MN is determined by POWER Peak current of UVP pin is connected to the voltage divider resistor R uvp1 and R uvp2 Detect input voltage V in , realize the feedforward compensation function, the feedforward compensation current flows out from the CSOUT pin, and the resistor R CS A compensation voltage is generated on the

[0003] exist Figure 1 The inventors of this application have found through research that the conventional compensation technology involved has the following deficiencies:

[0004] In the power tube MN POWER Feedforward compensation is introduced during both the start-up and shutdown phases. POWER When the CSOUT pin is turned off, the voltage on the sampling resistor Rcs is zero, and the amplified output is at the resistor R CSOUT The voltage on the UVP pin is also zero; however, since the current flowing into the UVP pin represents the information of the input voltage, the first compensation current I cs1 Falling on the resistor R CSOUT The voltage on the feedforward compensation voltage V LCS, instead of zero, which will lead to excessive feedforward compensation and the power tube will not turn on, resulting in large output ripple of the switching power supply and failure to meet the output indicators of the switching power supply.

[0005] At the same time, the switching power supply has the same drive delay at high and low voltage inputs because the main control IC has the same drive delay: at high voltage, the primary side peak current rises quickly and reaches the overcurrent point quickly. At low voltage, the primary side peak current rises more slowly and reaches the overcurrent point relatively slowly. Under the same drive delay, the overcurrent points are inconsistent at high and low input voltages. Overcurrent point consistency is particularly important for switching power supplies and is related to the consistency of power supply products. This will directly affect the applicability and efficiency of the switching power supply and even the entire power distribution system.

[0006] It should be noted that the information disclosed in the background technology section above is only intended to deepen the understanding of the overall background technology of this application, and should not be regarded as an admission or in any form of implication that the information constitutes prior art already known to those skilled in the art. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a feedforward compensation and overcurrent protection method, device, switching power supply and distribution system, which at least to a certain extent solve one of the technical problems existing in the prior art.

[0008] The inventive concept of the present application is: different feedforward compensation amounts are provided for different input voltages to achieve the compensation function of wide-range input voltage sampling; at the same time, an overcurrent point compensation amount is introduced, and different overcurrent point compensation amounts are provided for different input voltages, so that the overcurrent point remains consistent under high and low input voltages, avoiding the problem that the overcurrent point difference is too large when the input voltage is wide range and does not meet the output indicators of the switching power supply.

[0009] As a first aspect of the present invention, the embodiment and technical solution of the feedforward compensation and overcurrent protection method provided are as follows:

[0010] A feedforward compensation and overcurrent protection method is applied to a switching power supply, wherein the switching power supply includes a main power tube and a main control IC, a voltage divider, a sampling resistor R CSOUT , sampling resistor Rcs, sampling resistor R CSP and sampling resistor R CSN The main control IC includes an input voltage detection pin UVP, a first current sampling pin CSOUT, a second current sampling pin CSP, and a third current sampling pin CSN. The voltage divider includes a first voltage divider and a second voltage divider connected in series. One end of the voltage divider is connected to the input end of the switching power supply, the voltage dividing point is connected to the input voltage detection pin UVP, and the other end is grounded. The sampling resistor R CS One end is connected to the drain of the main power tube and the other end is grounded. The sampling resistor R CSOUTConnect the first current sampling pin CSOUT and the sampling resistor R CS Between the other ends, the sampling resistor R CSP Connect the second current sensing pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sensing pin CSN and the sampling resistor R CS The other end, the second current sampling pin CSP and the third current sampling pin CSN signal subtraction and amplification output signal superimposed on the first current sampling pin CSOUT is used to generate PWM turn-off voltage, thereby realizing the feedforward compensation function of the switching power supply. At the same time, the overcurrent point voltage V OCP The signal on the first current sampling pin CSOUT is subtracted and used to generate a PWM turn-off voltage, thereby realizing the overcurrent protection function of the switching power supply. The feedforward compensation and overcurrent protection method includes:

[0011] Receive the input voltage sampling signal V of the switching power supply in , compared with the first preset voltage V1:

[0012] When V in When V<V1, the voltage of the input voltage detection pin UVP is controlled to follow the input voltage change, and the voltage divider does not generate a discharge current I UVP , so no feedforward compensation is performed, and the overcurrent point voltage V OCP is a third preset voltage V3;

[0013] When V in ≥V1, the voltage of the input voltage detection pin UVP is clamped to the first preset voltage V1, and the voltage divider will generate a discharge current I UVP , based on the discharge current I UVP The first compensation current Ics1 and the second compensation current Ics2 are generated in a proportional relationship; the first compensation current Ics1 passes through the sampling resistor R CSOUT Generate a feedforward compensation voltage for feedforward compensation; the second compensation current Ics2 is used to generate an overcurrent point voltage V that changes with the second compensation current Ics2 OCP , and the overcurrent point voltage V OCP The change of the second compensation current Ics2 is opposite to that of the second compensation current Ics2.

[0014] Furthermore, based on the discharge current I UVP A bias voltage Vbias is generated, and a first compensation current Ics1 and a second compensation current Ics2 are generated through a current mirror under the control of the bias voltage Vbias.

[0015] Furthermore, V OCP=V3-R1×Ics2; wherein: V3 is the third preset voltage, and R1 is the preset resistance value.

[0016] Furthermore, the second compensation current Ics2 generates a first bias current IB1 through a current mirror. The first bias current IB1 and the first compensation resistor R1 generate a first voltage. The third preset voltage V3 is subtracted from the first voltage to form an overcurrent point voltage.

[0017] Furthermore, when V in ≥ V1, if the second voltage representing the input voltage of the switching power supply is greater than or equal to the second preset voltage V2, the overcurrent point voltage V OCP It no longer changes with the second compensation current Ics2 but is set according to the first preset current I1.

[0018] Furthermore, the discharge current I UVP A second bias current IB2 is generated by the current mirror, and the second bias current IB2 and the second compensation resistor R2 generate the second voltage.

[0019] As a second aspect of the present invention, the embodiment and technical solution of the feedforward compensation and overcurrent protection device provided are as follows:

[0020] A feedforward compensation and overcurrent protection device is applied to a switching power supply, which includes a main power tube and a main control IC, a voltage divider, a sampling resistor R CSOUT , sampling resistor Rcs, sampling resistor R CSP and sampling resistor R CSN The main control IC includes an input voltage detection pin UVP, a first current sampling pin CSOUT, a second current sampling pin CSP, and a third current sampling pin CSN. The voltage divider includes a first voltage divider and a second voltage divider connected in series. One end of the voltage divider is connected to the input end of the switching power supply, the voltage dividing point is connected to the input voltage detection pin UVP, and the other end is grounded. The sampling resistor R CS One end is connected to the drain of the main power tube and the other end is grounded. The sampling resistor R CSOUT Connect the first current sampling pin CSOUT and the sampling resistor R CS Between the other ends, the sampling resistor R CSP Connect the second current sensing pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sensing pin CSN and the sampling resistor R CS The other end, the second current sampling pin CSP and the third current sampling pin CSN signal subtraction and amplification output signal superimposed on the first current sampling pin CSOUT is used to generate PWM turn-off voltage, thereby realizing the feedforward compensation function of the switching power supply. At the same time, the overcurrent point voltage V OCPThe subtraction of the signal on the first current sampling pin CSOUT is also used to generate a PWM turn-off voltage, thereby realizing the overcurrent protection function of the switching power supply, wherein the feedforward compensation and overcurrent protection device includes: a clamping module and a compensation module;

[0021] The first input terminal of the clamp module is used to receive the input voltage sampling signal V in , compared with the first preset voltage V1:

[0022] When V in <V1:

[0023] The clamp module is configured to follow the input voltage change by controlling the voltage of the input voltage detection pin UVP, and the voltage divider does not generate a bleeder current I UVP , so that the compensation module does not perform feedforward compensation, and the compensation module controls the overcurrent point voltage V OCP is a third preset voltage V3;

[0024] When V in ≥V1:

[0025] The clamping module is configured to control the voltage of the input voltage detection pin UVP to be clamped to a first preset voltage V1, at which time the voltage divider will generate a discharge current I UVP ;

[0026] The compensation module is now configured to: based on the discharge current I UVP The first compensation current Ics1 and the second compensation current Ics2 are generated in a proportional relationship; the first compensation current Ics1 passes through the sampling resistor R CSOUT Generate a feedforward compensation voltage for feedforward compensation; the second compensation current Ics2 is used to generate an overcurrent point voltage V that changes with the second compensation current Ics2 OCP , and the overcurrent point voltage V OCP The change of the second compensation current Ics2 is opposite to that of the second compensation current Ics2.

[0027] Furthermore, the clamping module is based on the discharge current I UVP A bias voltage Vbias is generated, and a first compensation current Ics1 and a second compensation current Ics2 are generated through a current mirror under the control of the bias voltage Vbias.

[0028] Furthermore, the compensation module generates a first bias current IB1 through a current mirror using the second compensation current Ics2. The first bias current IB1 and the first compensation resistor R1 generate a first voltage. The third preset voltage V3 is subtracted from the first voltage to form an overcurrent point voltage.

[0029] Furthermore, when V in≥ V1, the clamping module detects that if the second voltage representing the magnitude of the input voltage of the switching power supply is greater than or equal to the second preset voltage V2, the compensation module controls the overcurrent point voltage V OCP It no longer changes with the second compensation current Ics2 but is set according to the first preset current I1.

[0030] Furthermore, the clamping module discharges the current I UVP A second bias current IB2 is generated by the current mirror, and the second bias current IB2 and the second compensation resistor R2 generate the second voltage.

[0031] As a third aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows:

[0032] A switching power supply, comprising a main power tube and a main control IC, a voltage divider, a sampling resistor R CSOUT , sampling resistor Rcs, sampling resistor R CSP and sampling resistor R CSN The main control IC includes an input voltage detection pin UVP, a first current sampling pin CSOUT, a second current sampling pin CSP, and a third current sampling pin CSN. The voltage divider includes a first voltage divider and a second voltage divider connected in series. One end of the voltage divider is connected to the input end of the switching power supply, the voltage dividing point is connected to the input voltage detection pin UVP, and the other end is grounded. The sampling resistor R CS One end is connected to the drain of the main power tube and the other end is grounded. The sampling resistor R CSOUT Connect the first current sampling pin CSOUT and the sampling resistor R CS Between the other ends, the sampling resistor R CSP Connect the second current sensing pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sensing pin CSN and the sampling resistor R CS The other end, the second current sampling pin CSP and the third current sampling pin CSN signal subtraction and amplification output signal superimposed on the first current sampling pin CSOUT is used to generate PWM turn-off voltage, thereby realizing the feedforward compensation function of the switching power supply. At the same time, the overcurrent point voltage V OCP The subtraction of the signal on the first current sampling pin CSOUT is also used to generate a PWM shutdown voltage, thereby realizing the overcurrent protection function of the switching power supply, wherein: the switching power supply also includes the feedforward compensation and overcurrent protection device described in any one of the second aspects above.

[0033] As a fourth aspect of the present invention, a power distribution system is provided, which includes the switching power supply of the above solution.

[0034] The feedforward compensation and overcurrent protection of the embodiment of the present invention adopt an interrelated two-stage strategy. Compared with the prior art, the beneficial effects are summarized as follows:

[0035] Compared with the prior art, the feedforward compensation targeted by the embodiments of the present invention can not only normally realize the compensation function of input voltage sampling, but also avoid the problem that under high voltage input, the feedforward compensation is too large, resulting in the power tube not turning on, and under low voltage input, the feedforward compensation is too small, resulting in the power tube not turning off in time, causing the switching power supply output ripple to be large and failing to meet the switching power supply output index requirements. This is beneficial to improving the efficiency and applicability of the switching power supply and even the entire power distribution system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A simplified diagram of an application circuit of a switching power supply with an external feedforward compensation circuit in the prior art;

[0037] Figure 2 A simplified diagram of a switching power supply circuit applicable to the present invention;

[0038] Figure 3 This is a circuit block diagram of several modules in one embodiment of the control IC involved in the present invention;

[0039] Figure 4 This is a basic circuit principle block diagram of an embodiment of the clamping module 110 of the present invention;

[0040] Figure 5 FIG1 is a basic circuit principle block diagram of an embodiment of the compensation module 120 of the present invention;

[0041] Figure 6 This is a basic circuit principle block diagram of an embodiment of the PWM shutdown module 200 of the present invention;

[0042] Figure 7 For the general Figure 4 and Figure 5 The circuit schematic after drawing together;

[0043] Figure 8 for Figure 7 An equivalent replacement circuit schematic. DETAILED DESCRIPTION

[0044] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0045] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0046] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate to describe the embodiments of the present application here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0047] It should be understood that in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

[0048] In addition, the figures of this disclosure are merely schematic diagrams of the present disclosure and are not necessarily drawn to scale. Identical reference numbers in the figures denote identical or similar parts, and therefore repeated descriptions thereof will be omitted. Some of the blocks shown in the figures are functional entities that do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented using software, in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontrollers.

[0049] Figure 2 This is a simplified diagram of a switching power supply circuit applicable to the present invention, which uses an optocoupler feedback flyback power supply, similar to Figure 1 The secondary side optocoupler, TL431 and loop compensation are omitted. The present invention uses current sampling, so the power density is higher than the above-mentioned known technology. Its feedback loop is equivalent to the known technology. In the topology of the present invention, the CSOUT pin is the current sampling output pin. Through the resistor R CSP 、R CSN 、RCSOUT The function of the sampling voltage is to amplify the voltage and flow through the power tube MN POWER Forming the final peak current.

[0050] First embodiment

[0051] This embodiment discloses a feedforward compensation and overcurrent protection method, which is applied to a switching power supply. Figure 2 As shown, it includes the main power tube and main control IC, voltage divider, sampling resistor R CSOUT , sampling resistor Rcs, sampling resistor R CSP and sampling resistor R CSN The main control IC includes an input voltage detection pin UVP, a first current sampling pin CSOUT, a second current sampling pin CSP, and a third current sampling pin CSN. The voltage divider includes a first voltage divider and a second voltage divider connected in series. One end of the voltage divider is connected to the input end of the switching power supply, the voltage dividing point is connected to the input voltage detection pin UVP, and the other end is grounded. The sampling resistor R CS One end is connected to the drain of the main power tube and the other end is grounded. The sampling resistor R CSOUT Connect the first current sampling pin CSOUT and the sampling resistor R CS Between the other ends, the sampling resistor R CSP Connect the second current sensing pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sensing pin CSN and the sampling resistor R CS The other end, the second current sampling pin CSP and the third current sampling pin CSN signal subtraction and amplification output signal superimposed on the first current sampling pin CSOUT is used to generate PWM turn-off voltage, thereby realizing the feedforward compensation function of the switching power supply. At the same time, the overcurrent point voltage V OCP The signal on the first current sampling pin CSOUT is subtracted and used to generate a PWM turn-off voltage, thereby realizing the overcurrent protection function of the switching power supply. The feedforward compensation and overcurrent protection method includes:

[0052] Receive the input voltage sampling signal V of the switching power supply in , compared with the first preset voltage V1:

[0053] When V in When V<V1, the voltage of the input voltage detection pin UVP is controlled to follow the input voltage change, and the voltage divider does not generate a discharge current I UVP , so no feedforward compensation is performed, and the overcurrent point voltage V OCP is a third preset voltage V3;

[0054] When V in≥V1, the voltage of the input voltage detection pin UVP is clamped to the first preset voltage V1, and the voltage divider will generate a discharge current I UVP , based on the discharge current I UVP The first compensation current Ics1 and the second compensation current Ics2 are generated in a proportional relationship; the first compensation current Ics1 passes through the sampling resistor R CSOUT Generate a feedforward compensation voltage for feedforward compensation; the second compensation current Ics2 is used to generate an overcurrent point voltage V that changes with the second compensation current Ics2 OCP , and the overcurrent point voltage V OCP The change of the second compensation current Ics2 is opposite to that of the second compensation current Ics2.

[0055] The advantages of this embodiment are: it realizes that the feedforward compensation current is provided only during the power tube turn-on phase, realizes the compensation function of the input voltage sampling, and avoids the problem that the power tube does not turn on due to excessive feedforward compensation during the power tube turn-off phase, especially under high voltage input, resulting in large output ripple of the switching power supply and failure to meet the output indicators of the switching power supply.

[0056] As a specific implementation method, based on the discharge current I UVP A bias voltage Vbias is generated, and a first compensation current Ics1 and a second compensation current Ics2 are generated through a current mirror under the control of the bias voltage Vbias.

[0057] As a specific embodiment, V OCP =V3-R1×Ics2; wherein: V3 is the third preset voltage, and R1 is the preset resistance value.

[0058] As a specific implementation, the second compensation current Ics2 generates a first bias current IB1 through a current mirror. The first bias current IB1 and the first compensation resistor R1 generate a first voltage. The third preset voltage V3 is subtracted from the first voltage to form an overcurrent point voltage.

[0059] As a specific implementation, when V in ≥ V1, if the second voltage representing the input voltage of the switching power supply is greater than or equal to the second preset voltage V2, the overcurrent point voltage V OCP It no longer changes with the second compensation current Ics2 but is set according to the first preset current I1, thereby ensuring that the overcurrent points in the switching power supply are consistent under high and low voltage inputs.

[0060] As a specific implementation, the discharge current I UVP A second bias current IB2 is generated by the current mirror, and the second bias current IB2 and the second compensation resistor R2 generate a second voltage.

[0061] Second embodiment

[0062] This embodiment discloses a feedforward compensation and overcurrent protection device for use in a switching power supply. The switching power supply includes a main power tube and a main control IC, a voltage divider, a sampling resistor R CSOUT , sampling resistor Rcs, sampling resistor R CSP and sampling resistor R CSN The main control IC includes an input voltage detection pin UVP, a first current sampling pin CSOUT, a second current sampling pin CSP, and a third current sampling pin CSN. The voltage divider includes a first voltage divider and a second voltage divider connected in series. One end of the voltage divider is connected to the input end of the switching power supply, the voltage dividing point is connected to the input voltage detection pin UVP, and the other end is grounded. The sampling resistor R CS One end is connected to the drain of the main power tube and the other end is grounded. The sampling resistor R CSOUT Connect the first current sampling pin CSOUT and the sampling resistor R CS Between the other ends, the sampling resistor R CSP Connect the second current sensing pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sensing pin CSN and the sampling resistor R CS The other end, the second current sampling pin CSP and the third current sampling pin CSN signal subtraction and amplification output signal superimposed on the first current sampling pin CSOUT is used to generate PWM turn-off voltage, thereby realizing the feedforward compensation function of the switching power supply. At the same time, the overcurrent point voltage V OCP The subtraction of the signal on the first current sampling pin CSOUT is also used to generate a PWM turn-off voltage, thereby realizing the overcurrent protection function of the switching power supply, wherein the feedforward compensation and overcurrent protection device includes: a clamping module and a compensation module;

[0063] The first input terminal of the clamp module is used to receive the input voltage sampling signal V in , compared with the first preset voltage V1:

[0064] When V in <V1:

[0065] The clamp module is configured to follow the input voltage change by controlling the voltage of the input voltage detection pin UVP. The voltage divider does not generate a bleeder current I UVP , so that the compensation module does not perform feedforward compensation, and the compensation module controls the overcurrent point voltage V OCP is a third preset voltage V3;

[0066] When V in ≥V1:

[0067] The clamping module is configured to control the voltage of the input voltage detection pin UVP to be clamped to a first preset voltage V1, at which time the voltage divider will generate a discharge current I UVP ;

[0068] The compensation module is now configured as follows: Based on the discharge current I UVP The first compensation current Ics1 and the second compensation current Ics2 are generated in a proportional relationship; the first compensation current Ics1 passes through the sampling resistor R CSOUT Generate a feedforward compensation voltage for feedforward compensation; the second compensation current Ics2 is used to generate an overcurrent point voltage V that changes with the second compensation current Ics2 OCP , and the overcurrent point voltage V OCP The change of the second compensation current Ics2 is opposite to that of the second compensation current Ics2.

[0069] As a specific implementation, the clamping module is based on the discharge current I UVP A bias voltage Vbias is generated, and a first compensation current Ics1 and a second compensation current Ics2 are generated through a current mirror under the control of the bias voltage Vbias.

[0070] As a specific implementation, the compensation module uses the second compensation current Ics2 to generate a first bias current IB1 through a current mirror. The first bias current IB1 and the first compensation resistor R1 generate a first voltage. The third preset voltage V3 is subtracted from the first voltage to form an overcurrent point voltage.

[0071] As a specific implementation, when V in ≥ V1, the clamping module detects that if the second voltage representing the input voltage of the switching power supply is greater than or equal to the second preset voltage V2, the compensation module controls the overcurrent point voltage V OCP It no longer changes with the second compensation current Ics2 but is set according to the first preset current I1.

[0072] As a specific implementation, the clamping module discharges the current I UVP A second bias current IB2 is generated by the current mirror, and the second bias current IB2 and the second compensation resistor R2 generate a second voltage.

[0073] The technical means adopted by the control device of this embodiment correspond to and are consistent with the control method of the first embodiment, and have the same beneficial effects.

[0074] Third embodiment

[0075] A switching power supply includes a main power tube and a main control IC, a voltage divider, a sampling resistor R CSOUT , sampling resistor Rcs, sampling resistor R CSP and sampling resistor RCSN The main control IC includes an input voltage detection pin UVP, a first current sampling pin CSOUT, a second current sampling pin CSP, and a third current sampling pin CSN. The voltage divider includes a first voltage divider and a second voltage divider connected in series. One end of the voltage divider is connected to the input end of the switching power supply, the voltage dividing point is connected to the input voltage detection pin UVP, and the other end is grounded. The sampling resistor R CS One end is connected to the drain of the main power tube and the other end is grounded. The sampling resistor R CSOUT Connect the first current sampling pin CSOUT and the sampling resistor R CS Between the other ends, the sampling resistor R CSP Connect the second current sensing pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sensing pin CSN and the sampling resistor R CS The other end, the second current sampling pin CSP and the third current sampling pin CSN signal subtraction and amplification output signal superimposed on the first current sampling pin CSOUT is used to generate PWM turn-off voltage, thereby realizing the feedforward compensation function of the switching power supply. At the same time, the overcurrent point voltage V OCP The subtraction of the signal on the first current sampling pin CSOUT is also used to generate a PWM turn-off voltage, thereby realizing the overcurrent protection function of the switching power supply, wherein: the switching power supply also includes any feedforward compensation and overcurrent protection device of the second embodiment.

[0076] Figure 3 This is a circuit block diagram 10 of several modules in an embodiment of the control IC involved in the present invention, including a preset voltage V1, a preset voltage V2, a preset voltage V3, a preset current I1, a pin UVP, a pin CSP, a pin CSN, a pin CSOUT, a clamp module 110, a clamp module 120, a PWM shutdown module 200, a node Vbias, a node Ctrl, a node Ics1, and a node Ics2.

[0077] Figure 3 The connection relationship is as follows:

[0078] One end of the clamp module 110 is connected to the pin UVP to form a current mirror node for receiving the input voltage sampling signal; the other end of the clamp module 110 is connected to the preset voltage V1, which is the clamping reference of the clamp module. The output of one end of the clamp module 110 is the bias control voltage Vbias of the feedforward compensation current; the output of the other end of the clamp module 110 is the control signal Ctrl, which controls the compensation amount of the overcurrent point under different input voltages.

[0079] The compensation module 120 has an input of the output Vbias of the clamp module 110, which serves as the bias control voltage for the feedforward compensation current. Another input of the compensation module 120 is another output Ctrl of the clamp module 110, which serves as a control signal for the overcurrent point compensation amount under different input voltages. The other end of the compensation module 120 is connected to the preset voltage V2, and one end of the compensation module 120 is connected to the preset current I1. One output of the compensation module 120 is the current I cs1 , the other output of the compensation module 120 is the current I cs2 .

[0080] The PWM shutdown module 200 is connected to the preset voltage V3. One input of the PWM shutdown module 200 is an output Ics1 of the compensation module 120. Another input of the PWM shutdown module 200 is another output Ics2 of the compensation module 120. One end of the PWM shutdown module 200 is connected to the pin CSN, the other end is connected to the pin CSP, and the output is connected to the pin CSOUT.

[0081] Figure 3 The working principle is as follows: the clamping module 110 is connected to the preset voltage V1, which is the clamping reference of the clamping module; the clamping module is also connected to the pin UVP, and when the voltage of the external voltage divider of the pin UVP is greater than or equal to V1, the voltage of the UVP pin is clamped to the preset voltage V1, that is, at this time V UVP =V1; when the clamping module 110 combines the preset voltage V1 and the input voltage information obtained from the UVP pin, it generates Vbias and Ctrl signals; the compensation module 120 generates two currents Ics1 and Ics2 through the Vbias and Ctrl signals, combined with the preset voltage V2 and the preset current I1; Ics1 and Ics2 are sent to the PWM shutdown module 200, and the PWM shutdown module 200 combines pins CSN and CSP; then a compensation amount is generated at the output of the PWM shutdown module 200, which is superimposed on the CSOUT pin resistor to generate a PWM shutdown voltage, thereby realizing a feedforward compensation function with a wide voltage input range; at the same time, by controlling the preset voltage within the compensation module 120, the consistency of the overcurrent point over a wide range of input voltages is adjusted, and a control signal Ctrl is output from the other end of the clamping module 110 to realize different coefficient compensation under different input voltages.

[0082] Figure 4 This is a basic circuit diagram of an embodiment of the clamping module 110 of the present invention. Figure 5 This is a basic circuit diagram of an embodiment of the compensation module 120 of the present invention. Figure 6 This is a basic circuit principle block diagram of an embodiment of the PWM shutdown module 200 of the present invention.

[0083] Figure 4 The clamp module 110 includes a PMOS transistor PM1, a PMOS transistor PM2, a PMOS transistor PM10, a PMOS transistor PM9, an NMOS transistor NM1, an NMOS transistor NM2, an NMOS transistor NM8, a resistor R2, a comparator COMP1, and an operational amplifier BUFFER connected to a unit negative feedback gain, wherein the positive input terminal of the operational amplifier BUFFER connected to a unit negative feedback gain is connected to a preset voltage V1, and the output terminal is connected to the source of the PMOS transistor PM1, the gate of the PMOS transistor PM1 and the drain of the PMOS transistor PM1 are connected to the gate of the PMOS transistor PM2, and are connected to the drain of the NMOS transistor NM1; the source of the PMOS transistor PM2 is connected to the pin UVP, and the drain of the PMOS transistor PM2 is connected to the gate of the NMOS transistor NM1 and the drain of the NMOS transistor NM8. The gate and drain of NM2 and the gate of NMOS transistor NM8 are connected. The drain of NMOS transistor NM8 is connected to the drain and gate of PMOS transistor PM10. The source of PMOS transistor PM10 is connected to power supply VCC. The drain of PMOS transistor PM9 is connected to one end of resistor R2 and the positive end of comparator comp1, and the negative end of comparator comp1 is connected to preset voltage V2. The other end of resistor R2 is connected to ground. The drain of NMOS transistor NM2 serves as an output of clamping module 110, forming node Vbias. The output of comparator comp1 serves as another output of clamping module 110, forming node Ctrl. The sources of NMOS transistors NM1, NMOS transistors NM2, and NMOS transistor NM8 are connected to reference ground.

[0084] Figure 5The compensation module 120 includes a PMOS transistor PM3, a PMOS transistor PM4, a PMOS transistor PM5, a PMOS transistor PM6, a PMOS transistor PM7, a PMOS transistor PM8, an NMOS transistor NM3, an NMOS transistor NM5, an NMOS transistor NM6, and an NMOS transistor NM7. The drain of the NMOS transistor NM7 is connected to the preset current I1, the gate of the PMOS transistor PM3 is connected to the gate of the PMOS transistor PM4, the gate of the PMOS transistor PM5 is connected, the gate of the PMOS transistor PM6 is connected to the gate of the PMOS transistor PM7, the source of the PMOS transistor PM3, the source of the PMOS transistor PM4, the source of the PMOS transistor PM5, the source of the PMOS transistor PM6, and the PMOS transistor PM7. 7 is connected to the reference power supply VCC; the gate of the PMOS transistor PM3 is connected to the drain of the PMOS transistor PM3 and the drain of the NMOS transistor NM3; the gate of the NMOS transistor NM3 is connected to an output Vbias of the clamping module 110; the drain of the PMOS transistor PM4 serves as an output of the compensation module 120 to form a node Ics1; the drain of the PMOS transistor PM5 is connected to the source of the PMOS transistor PM8, and the gate of the PMOS transistor PM8 is connected to another output node Ctrl of the clamping module 110; the drain of the PMOS transistor PM8 is connected to the drain of the PMOS transistor PM6 to form an output node Ics2; and the drain of the PMOS transistor PM4 forms an output node Ics1. The gate of the PMOS transistor PM6, the gate of the PMOS transistor PM7, and the drain of the PMOS transistor PM7 are connected, the drain of the NMOS transistor NM6 is connected to the gate of the NMOS transistor NM6 and the gate of the NMOS transistor NM5, the drain of NM6 is connected to the source of NM7, the drain of NM7 serves as the input of the preset current I1, and the gate of NM7 serves as the input of Ctrl.

[0085] Figure 6 This is an implementation scheme of the PWM shutdown module 200 of the present invention. The current sampling operational amplifier is connected to the pins CSP, CSN, and CSOUT. The clamping operational amplifier is connected in a unit gain negative feedback form. The positive terminal is connected to the preset voltage V3. The negative terminal is connected to the drain of the NMOS transistor NM8. The gate of the NMOS transistor NM8 is connected to the gate of the NMOS transistor NM9 and the gate of the NMOS transistor NM10. The drain of the NMOS transistor NM9 is connected to the gate. The drain input current I cs2The positive end of the clamp op amp is also connected to one end of the resistor R1, the other end of the resistor R1 is connected to the positive end of the comparator COM_OCP, the negative end of the comparator COM_OCP is connected to the CSOUT pin, the positive end of the comparator COM_PWM is connected to the FB after the PWM gain, the negative end of the comparator COM_PWM is connected to the CSOUT pin, the outputs of the two comparators are used as the inputs of the NAND gate NAND, the output of the NAND gate NAND is connected to the input of the inverter INV, the output of the inverter INV is connected to the clear end Clr_L of the low-level trigger DFF, the trigger end CP_L of DFF is connected to the preset clock CLK, the data end D of the trigger DFF is connected to the power supply voltage VCC, and the output end Q of the trigger DFF is finally output to the main power tube drive GTL.

[0086] Figure 7 Will Figure 4 and Figure 5 Draw together, the working principle is analyzed as follows:

[0087] The input voltage sampling signal is received and compared with the first preset voltage V1 to generate a bias voltage Vbias and a first control signal Ctrl. When the input voltage passes through the resistor divider, if it is lower than the first preset voltage V1, no feedforward current Iuvp is generated, and no overcurrent point compensation is performed. The overcurrent point is the third preset voltage V3. If it is higher than the first preset voltage V1, a bias voltage Vbias is generated, and the bias voltage Vbias generates a first compensation current Ics1 and a second compensation current Ics2. The first compensation current Ics1 and the resistor R CSOUT A feedforward compensation voltage is generated. The second compensation current Ics2 generates the first bias current IB1 through a current mirror. The first bias current IB1 and the first compensation resistor R1 generate a voltage, which is subtracted from the third preset voltage V3 to form the overcurrent point voltage. As the input voltage reaches a certain value, the second bias current IB2 is generated under the control of the bias voltage Vbias. When the product of the second bias current IB2 and the second compensation resistor R2 falls below the second preset voltage V2, the first control signal Ctrl becomes the ground voltage. The first control signal Ctrl closes the first switch NM7 and opens the second switch PM8, causing the first bias current IB1 to follow the second compensation current Ics2 at a predetermined ratio. When the product of the second bias current IB2 and the second compensation resistor exceeds the second preset voltage V2, the first control signal Ctrl becomes the power supply voltage. The first control signal Ctrl opens the first switch NM7 and closes the third switch PM8, causing the second compensation current Ics2 to be a predetermined ratio of the first preset current I1. This achieves consistent overcurrent point compensation for switching power supplies under high and low voltage conditions. By setting the first preset current I1, overcurrent point compensation for different switching power supplies can be achieved. It can be expressed specifically by the following relationship:

[0088] (1)

[0089] The clamp module will current I UVP In the compensation module, I is generated according to the mirror ratio K1 and K2. cs1 with I cs2 ,Right now

[0090] (2)

[0091] I cs1 Flows through the resistor R through the pin CSOUT CSOUT To generate a compensation voltage V CSOUT =I cs1 ·R CSOUT , realizing the feedforward compensation function. At the same time, for different input voltages, the proportional coefficient K1 can be changed by setting the current mirror to achieve different compensation amounts.

[0092] The actual feedforward compensation can be expressed as:

[0093] (3)

[0094] Figure 7 A two-stage overcurrent point compensation is adopted to achieve different compensation amounts for the overcurrent point under a wide range of voltage input. The compensation amount is flexibly adjustable, ensuring the consistency of the overcurrent point of the switching power supply under different input voltages. This solves the problem of difficulty in ensuring consistency of the overcurrent point in switching power supplies with a wide input range. The implementation method has fewer circuits, a small area, low cost, and reliable function. The basic principle of its overcurrent point consistency compensation function is as follows:

[0095] At high and low input voltages, the main control IC has the same drive delay, resulting in inconsistent overcurrent points at high and low input voltages. Consistency is particularly important for switching power supplies. The following relationship can be used to achieve consistency compensation for overcurrent points at high and low input voltages:

[0096] (4)

[0097] The actual overcurrent point can be expressed as:

[0098] (5)

[0099] I cs2 The first bias current IB1 is generated by the current mirror. The first bias current IB1 and the first compensation resistor R1 generate a voltage whose value is V C =I cs2 R1, through different I cs2 Achieve compensation function of overcurrent point under high and low voltage. Specifically, when V in ≥ V1: If the second voltage representing the input voltage of the switching power supply is less than the second preset voltage V2, the overcurrent point voltage VOCP Changes with the second compensation current Ics2; if the second voltage representing the input voltage of the switching power supply is greater than or equal to the second preset voltage V2, the overcurrent point voltage V OCP The setting is performed according to the first preset current I1.

[0100] Figure 7 The circuit solves the problem of meeting the consistency of high and low voltage overcurrent points under a wide range of DC input voltage. When the high voltage input is applied, the received input voltage sampling signal is much larger than the first preset voltage V1, and the current Iuvp flowing into the controller through the clamping module is relatively large, resulting in the added feedforward compensation voltage V LCS During the power tube shutdown period, if the voltage V on the pin CSOUT CS If the voltage is greater than VFB_CS, the PWM comparator CMP_PWM outputs the Toff_L signal at a low level, which is sent to the clear terminal Clr_L of the D flip-flop DFF. The output terminal Q of the D flip-flop outputs a low signal, and the GTL pin is low. The power tube is not turned on, resulting in a lack of the power tube drive signal. The problem caused by the lack of the drive signal is that there is no energy transferred from the primary side to the secondary side, causing the switching power supply output to lose power, the output ripple is large, the output loop is unstable, and the switching power supply output index requirements are not met. Therefore, in order to avoid this situation, a suitable compensation amount needs to be selected when the high voltage input is used. Similarly, when the input voltage is low, the feedforward compensation voltage V LCS It will be relatively small and may not achieve the compensation effect. Therefore, in the design of switching power supplies, the compensation amount needs to be adjusted according to the input voltage. In different switching power supply designs, it is particularly important to choose a suitable compensation amount, taking into account the influence of high and low input voltages.

[0101] Figure 8 for Figure 7 An equivalent replacement circuit diagram, such as Figure 8 As shown, Figure 7 The difference is that Figure 8 The drain of the PMOS transistor PM9 in the clamping module 110 is connected to the positive terminal of the comparator comp1, and the negative terminal of the comparator comp1 is connected to one end of the resistor. Similarly, the comparator outputs a first control signal Ctrl to control a mirror ratio. Compared with embodiment 1, the way the comparator generates the output signal is different. However, it can also indicate that when the input sampling voltage exceeds the preset voltage value V1, I UVP The inflow will produce currents with different proportional coefficients. UVP Generate I in a certain proportion through current mirror cs1 with I cs1 , the final feedforward voltage V CSOUT Only then it is produced.

[0102] Although the implementation methods are different, the ultimate goal is to make the feedforward current I cs1 A current flows through the clamp module, and another current is generated by the current mirror and the resistor R CSOUT A suitable compensation amount is generated to realize the feedforward compensation function. At the same time, a current I is generated to adjust the overcurrent point compensation. cs2 , so that the overcurrent point of the switching power supply can be kept consistent under a wide range of input voltage.

[0103] The switching power supply described in the present invention is specifically applied to power distribution systems and can be widely used in industrial control, intelligent transportation, smart grid, smart medical care, new energy, Internet of Things, communications and other fields to meet the power distribution requirements necessary for system operation.

[0104] The above is a preferred embodiment of the present invention. In addition, there are many other ways to control the timing of the feedforward compensation current. UVP , generate feedforward current I cs1 , overcurrent point compensation current I cs2 , or the final feedforward compensation voltage V CSOUT As long as the feedforward compensation function is ultimately added through the input voltage, the overcurrent point compensation current falls within the scope of protection of this patent. It should be noted that for ordinary technicians in this technical field, several improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A feedforward compensation and overcurrent protection method is applied to a switching power supply, wherein the switching power supply includes a main power tube and a main control IC, a voltage divider, a sampling resistor R CSOUT , sampling resistor Rcs, sampling resistor R CSP and sampling resistor R CSN The main control IC includes an input voltage detection pin UVP, a first current sampling pin CSOUT, a second current sampling pin CSP, and a third current sampling pin CSN. The voltage divider includes a first voltage divider and a second voltage divider connected in series. One end of the voltage divider is connected to the input end of the switching power supply, the voltage dividing point is connected to the input voltage detection pin UVP, and the other end is grounded. The sampling resistor R CS One end is connected to the drain of the main power tube and the other end is grounded. The sampling resistor R CSOUT Connect the first current sampling pin CSOUT and the sampling resistor R CS Between the other ends, the sampling resistor R CSP Connect the second current sensing pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sensing pin CSN and the sampling resistor R CS The other end, the second current sampling pin CSP and the third current sampling pin CSN signal subtraction and amplification output signal superimposed on the first current sampling pin CSOUT is used to generate PWM turn-off voltage, thereby realizing the feedforward compensation function of the switching power supply. At the same time, the overcurrent point voltage V OCP The signal on the first current sampling pin CSOUT is subtracted and used to generate a PWM turn-off voltage, thereby realizing the overcurrent protection function of the switching power supply, which is characterized in that: The feedforward compensation and overcurrent protection method includes: Receive the input voltage sampling signal V of the switching power supply in , compared with the first preset voltage V1: When V in When V<V1, the voltage of the input voltage detection pin UVP is controlled to follow the input voltage change, and the voltage divider does not generate a discharge current I UVP , so no feedforward compensation is performed, and the overcurrent point voltage V OCP is a third preset voltage V3; When V in ≥V1, the voltage of the input voltage detection pin UVP is clamped to the first preset voltage V1, and the voltage divider will generate a discharge current I UVP , based on the discharge current I UVP The first compensation current Ics1 and the second compensation current Ics2 are generated in a proportional relationship; the first compensation current Ics1 passes through the sampling resistor R CSOUT Generate a feedforward compensation voltage for feedforward compensation; the second compensation current Ics2 is used to generate an overcurrent point voltage V that changes with the second compensation current Ics2 OCP , and the overcurrent point voltage V OCP The change of the second compensation current Ics2 is opposite to that of the second compensation current Ics2.

2. The feedforward compensation and overcurrent protection method according to claim 1, characterized in that: Based on the discharge current I UVP A bias voltage Vbias is generated, and a first compensation current Ics1 and a second compensation current Ics2 are generated through a current mirror under the control of the bias voltage Vbias.

3. The feedforward compensation and overcurrent protection method according to claim 1, characterized in that: V OCP =V3-R1×Ics2; wherein: V3 is the third preset voltage, and R1 is the preset resistance value.

4. The feedforward compensation and overcurrent protection method according to claim 3, characterized in that: The second compensation current Ics2 generates a first bias current IB1 through the current mirror. The first bias current IB1 and the first compensation resistor R1 generate a first voltage. The third preset voltage V3 is subtracted from the first voltage to generate an overcurrent point voltage.

5. The feedforward compensation and overcurrent protection method according to claim 1, characterized in that: When V in ≥ V1, if the second voltage representing the input voltage of the switching power supply is greater than or equal to the second preset voltage V2, the overcurrent point voltage V OCP It no longer changes with the second compensation current Ics2 but is set according to the first preset current I1.

6. The feedforward compensation and overcurrent protection method according to claim 5, characterized in that: The discharge current I UVP A second bias current IB2 is generated by the current mirror, and the second bias current IB2 and the second compensation resistor R2 generate the second voltage.

7. A feedforward compensation and overcurrent protection device, applied to a switching power supply, the switching power supply comprising a main power tube and a main control IC, a voltage divider, a sampling resistor R CSOUT , sampling resistor Rcs, sampling resistor R CSP and sampling resistor R CSN The main control IC includes an input voltage detection pin UVP, a first current sampling pin CSOUT, a second current sampling pin CSP, and a third current sampling pin CSN. The voltage divider includes a first voltage divider and a second voltage divider connected in series. One end of the voltage divider is connected to the input end of the switching power supply, the voltage dividing point is connected to the input voltage detection pin UVP, and the other end is grounded. The sampling resistor R CS One end is connected to the drain of the main power tube and the other end is grounded. The sampling resistor R CSOUT Connect the first current sampling pin CSOUT and the sampling resistor R CS Between the other ends, the sampling resistor R CSP Connect the second current sensing pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sensing pin CSN and the sampling resistor R CS The other end, the second current sampling pin CSP and the third current sampling pin CSN signal subtraction and amplification output signal superimposed on the first current sampling pin CSOUT is used to generate PWM turn-off voltage, thereby realizing the feedforward compensation function of the switching power supply. At the same time, the overcurrent point voltage V OCP The signal on the first current sampling pin CSOUT is subtracted and used to generate a PWM turn-off voltage, thereby realizing the overcurrent protection function of the switching power supply, which is characterized in that: The feedforward compensation and overcurrent protection device includes: a clamping module and a compensation module; The first input terminal of the clamp module is used to receive the input voltage sampling signal V in , compared with the first preset voltage V1: When V in <V1: The clamp module is configured to follow the input voltage change by controlling the voltage of the input voltage detection pin UVP, and the voltage divider does not generate a discharge current I UVP , so that the compensation module does not perform feedforward compensation, and the compensation module controls the overcurrent point voltage V OCP is a third preset voltage V3; When V in ≥V1: The clamping module is configured to control the voltage of the input voltage detection pin UVP to be clamped to a first preset voltage V1, at which time the voltage divider will generate a discharge current I UVP ; The compensation module is now configured to: based on the discharge current I UVP The first compensation current Ics1 and the second compensation current Ics2 are generated in a proportional relationship; the first compensation current Ics1 passes through the sampling resistor R CSOUT Generate a feedforward compensation voltage for feedforward compensation; the second compensation current Ics2 is used to generate an overcurrent point voltage V that changes with the second compensation current Ics2 OCP , and the overcurrent point voltage V OCP The change of the second compensation current Ics2 is opposite to that of the second compensation current Ics2.

8. The feedforward compensation and overcurrent protection device according to claim 7, characterized in that: The clamping module is based on the discharge current I UVP A bias voltage Vbias is generated, and a first compensation current Ics1 and a second compensation current Ics2 are generated through a current mirror under the control of the bias voltage Vbias.

9. The feedforward compensation and overcurrent protection device according to claim 7, characterized in that: The compensation module generates a first bias current IB1 through a current mirror using the second compensation current Ics2. The first bias current IB1 and the first compensation resistor R1 generate a first voltage. The third preset voltage V3 is subtracted from the first voltage to form an overcurrent point voltage.

10. The feedforward compensation and overcurrent protection device according to claim 7, characterized in that: When V in ≥ V1, the clamping module detects that if the second voltage representing the magnitude of the switching power supply input voltage is greater than or equal to the second preset voltage V2, the compensation module controls the overcurrent point voltage V OCP It no longer changes with the second compensation current Ics2 but is set according to the first preset current I1.

11. The feedforward compensation and overcurrent protection device according to claim 10, characterized in that: The clamp module will discharge the current I UVP A second bias current IB2 is generated by the current mirror, and the second bias current IB2 and the second compensation resistor R2 generate the second voltage.

12. A switching power supply comprising a main power tube and a main control IC, a voltage divider, a sampling resistor R CSOUT , sampling resistor Rcs, sampling resistor R CSP and sampling resistor R CSN The main control IC includes an input voltage detection pin UVP, a first current sampling pin CSOUT, a second current sampling pin CSP, and a third current sampling pin CSN. The voltage divider includes a first voltage divider and a second voltage divider connected in series. One end of the voltage divider is connected to the input end of the switching power supply, the voltage dividing point is connected to the input voltage detection pin UVP, and the other end is grounded. The sampling resistor R CS One end is connected to the drain of the main power tube and the other end is grounded. The sampling resistor R CSOUT Connect the first current sampling pin CSOUT and the sampling resistor R CS Between the other ends, the sampling resistor R CSP Connect the second current sensing pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sensing pin CSN and the sampling resistor R CS The other end, the second current sampling pin CSP and the third current sampling pin CSN signal subtraction and amplification output signal superimposed on the first current sampling pin CSOUT is used to generate PWM turn-off voltage, thereby realizing the feedforward compensation function of the switching power supply. At the same time, the overcurrent point voltage V OCP The signal on the first current sampling pin CSOUT is subtracted to generate a PWM turn-off voltage, thereby realizing the overcurrent protection function of the switching power supply, which is characterized by: The switching power supply further comprises the feedforward compensation and overcurrent protection device according to any one of claims 7 to 11.

13. A power distribution system, characterized in that: Comprising the switching power supply as claimed in claim 12.

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