Feedforward compensation and overcurrent protection method and device, switching power supply and power distribution system

Abstract

The invention discloses a feed-forward compensation and overcurrent protection method and device, a switching power supply and a power distribution system.The feed-forward compensation and overcurrent protection method comprises the steps that an input voltage sampling signal Vin of the switching power supply is received and compared with a first preset voltage V1, when Vin is smaller than V1, the voltage of an input voltage detection pin is controlled to change along with the input voltage, and when Vin is smaller than V1, the input voltage detection pin is controlled to change along with the input voltage; the voltage divider does not generate discharge current, so that feed-forward compensation is not carried out, and the overcurrent point voltage is a third preset voltage; when Vin is greater than or equal to V1, controlling the voltage of the input voltage detection pin to be clamped as a first preset voltage, generating a bleeder current by the voltage divider, and generating a first compensation current and a second compensation current in proportion based on the bleeder current; the first compensation current generates feed-forward compensation voltage through the first compensation resistor, and the feed-forward compensation voltage is used for feed-forward compensation; and the second compensation current is used for generating an overcurrent point voltage which changes along with the change of the second compensation current. The problem that the power tube is not turned on due to too large feedforward compensation introduced under high-voltage input can be avoided, and the efficiency of the switching power supply and a power distribution system can be improved.

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, and a power distribution system having the power switch. Background Art

[0002] With the rapid development of electronic technology, a fully functional 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 POWER Peak current; UVP pin through 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 Among the conventional compensation technologies involved, the inventors of this application have found through research that the compensation technology solution has the following deficiencies: 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 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.

[0004] At the same time, the switching power supply has the same driving delay under high and low voltage inputs because the main control IC has the same driving delay: under high voltage, the primary peak current rises quickly and reaches the overcurrent point very quickly. Under low voltage, the primary peak current rises slowly and reaches the overcurrent point relatively slowly. Under the same driving delay, the overcurrent point is inconsistent when the input is high or low voltage. The consistency of the overcurrent point is particularly important for the switching power supply, which is related to the consistency of the power supply product, which will directly affect the applicability and efficiency of the switching power supply and even the entire power distribution system.

[0005] It should be noted that the above information disclosed in the background technology section is only intended to deepen the understanding of the overall background technology of this application, and should not be regarded as admitting or suggesting in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention

[0006] 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 solves one of the technical problems existing in the prior art to a certain extent.

[0007] 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 voltage input voltages, avoiding the problem of excessive differences in the overcurrent point when the input voltage is in a wide range and failing to meet the output indicators of the switching power supply.

[0008] As a first aspect of the present invention, the technical solution of the embodiment of the feedforward compensation and overcurrent protection method provided is as follows: 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 the 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 RCS The other end, the sampling resistor R CSP Connect the second current sampling pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sampling pin CSN and the sampling resistor R CS The signals of the second current sampling pin CSP and the third current sampling pin CSN are subtracted and amplified, and the output signal is superimposed on the first current sampling pin CSOUT to generate a 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: Receive the input voltage sampling signal V of the switching power supply in , compared with the first preset voltage V1: When V in When <V1, the voltage of input voltage detection pin UVP is controlled to follow the input voltage change, and the voltage divider does not generate discharge current I UVP , so no feed-forward 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 generates 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 proportion; 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 is opposite to the change of the second compensation current Ics2.

[0009] Further, 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.

[0010] Furthermore, V OCP =V3-R1×Ics2; wherein: V3 is the third preset voltage, and R1 is the preset resistance value.

[0011] 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, and the third preset voltage V3 is subtracted from the first voltage to form an overcurrent point voltage.

[0012] 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.

[0013] Furthermore, the discharge current I UVP The 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.

[0014] As a second aspect of the present invention, the technical solution of the embodiment of the feedforward compensation and overcurrent protection device provided is as follows: A feedforward compensation and overcurrent protection device 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 the 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 The other end, the sampling resistor R CSP Connect the second current sampling pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sampling pin CSN and the sampling resistor R CS The signals of the second current sampling pin CSP and the third current sampling pin CSN are subtracted and amplified, and the output signal is superimposed on the first current sampling pin CSOUT to generate a 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 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, wherein 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 generates 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 proportion; 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 is opposite to the change of the second compensation current Ics2.

[0015] 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.

[0016] 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.

[0017] Furthermore, 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 OCPIt no longer changes with the second compensation current Ics2, but is set according to the first preset current I1.

[0018] Furthermore, the clamping module discharges the current I UVP The 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 third aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows: 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 the 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 The other end, the sampling resistor R CSP Connect the second current sampling pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sampling pin CSN and the sampling resistor R CS The signals of the second current sampling pin CSP and the third current sampling pin CSN are subtracted and amplified, and the output signal is superimposed on the first current sampling pin CSOUT to generate a 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 Subtracting 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.

[0020] As a fourth aspect of the present invention, there is provided a power distribution system, which includes the switching power supply of the above-mentioned solution.

[0021] 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: Compared with the prior art, the feedforward compensation targeted by the embodiment of the present invention can not only realize the compensation function of input voltage sampling normally, 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 output ripple of the switching power supply to be large, and the output index requirements of the switching power supply are not met. 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

[0022] Figure 1 A simplified diagram of an application circuit of a switching power supply with an external feedforward compensation circuit in the prior art; Figure 2 A simplified diagram of a switching power supply circuit applicable to the present invention; Figure 3 A circuit block diagram of several modules in an embodiment of a control IC involved in the present invention; Figure 4 is a basic circuit principle block diagram of an embodiment of the clamping module 110 of the present invention; Figure 5 is a basic circuit principle block diagram of an embodiment of the compensation module 120 of the present invention; Figure 6 It is a basic circuit principle block diagram of an embodiment of the PWM shutdown module 200 of the present invention; Figure 7 For the general Figure 4 and Figure 5 The circuit schematic after drawing together; Figure 8 for Figure 7 An equivalent replacement circuit schematic. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0024] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0025] 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, so that the embodiments of the present application are described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising 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 equipment.

[0026] 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.

[0027] In addition, the drawings of the present disclosure are only schematic diagrams of the present disclosure and are not necessarily drawn to scale. The same symbols in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented using software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontrollers.

[0028] Figure 2 This is a simplified diagram of a switching power supply circuit applicable to the present invention, which adopts an optocoupler feedback flyback power supply, similar to Figure 1 The secondary side optocoupler, TL431 and loop compensation are omitted. Since the present invention adopts current sampling, the power density is higher than that of 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 , R CSOUT The function is to amplify the sampling voltage and flow it through the power tube MN POWER Forming the final peak current.

[0029] First embodiment 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 the 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 The other end, the sampling resistor R CSP Connect the second current sampling pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sampling pin CSN and the sampling resistor R CS The signals of the second current sampling pin CSP and the third current sampling pin CSN are subtracted and amplified, and the output signal is superimposed on the first current sampling pin CSOUT to generate a 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: Receive the input voltage sampling signal V of the switching power supply in , compared with the first preset voltage V1: When V in When <V1, the voltage of input voltage detection pin UVP is controlled to follow the input voltage change, and the voltage divider does not generate discharge current I UVP , so no feed-forward 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 generates 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 proportion; 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 is opposite to the change of the second compensation current Ics2.

[0030] The advantages of this embodiment are: it realizes providing feedforward compensation current only when the power tube is turned on, realizing the compensation function of input voltage sampling, and avoiding the problem that excessive feedforward compensation is introduced during the power tube shutdown period, causing the power tube to 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, especially under high voltage input.

[0031] As a specific implementation, 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.

[0032] As a specific implementation, V OCP =V3-R1×Ics2; wherein: V3 is the third preset voltage, and R1 is the preset resistance value.

[0033] 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, and the third preset voltage V3 is subtracted from the first voltage to form an overcurrent point voltage.

[0034] 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 point in the switching power supply is consistent under high and low voltage inputs.

[0035] 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.

[0036] Second embodiment This embodiment discloses a feedforward compensation and overcurrent protection device, which is applied to 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 the 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 RCS 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 The other end, the sampling resistor R CSP Connect the second current sampling pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sampling pin CSN and the sampling resistor R CS The signals of the second current sampling pin CSP and the third current sampling pin CSN are subtracted and amplified, and the output signal is superimposed on the first current sampling pin CSOUT to generate a 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, wherein 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 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; 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 generates a discharge current I UVP ; 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 proportion; 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 is opposite to the change of the second compensation current Ics2.

[0037] As a specific implementation, the clamping module is based on the discharge current I UVPA 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.

[0038] 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.

[0039] 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.

[0040] As a specific implementation, the clamp 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.

[0041] 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.

[0042] Third embodiment 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 the 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 The other end, the sampling resistor R CSP Connect the second current sampling pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sampling pin CSN and the sampling resistor R CSThe signals of the second current sampling pin CSP and the third current sampling pin CSN are subtracted and amplified, and the output signal is superimposed on the first current sampling pin CSOUT to generate a 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 subtracted from 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 any feedforward compensation and overcurrent protection device of the second embodiment.

[0043] Figure 3 The present invention relates to a circuit block diagram 10 of several modules in an embodiment of a control IC, 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.

[0044] Figure 3 The connection relationship is as follows: One end of the clamp module 110 is connected to the pin UVP to form a current mirror node for receiving an input voltage sampling signal; the other end of the clamp module 110 is connected to a preset voltage V1, which is a clamp reference of the clamp module. One end of the clamp module 110 outputs a bias control voltage Vbias of a feedforward compensation current; the other end of the clamp module 110 outputs a control signal Ctrl, which controls the compensation amount of the overcurrent point under different input voltages.

[0045] The compensation module 120 has an input Vbias, an output of the clamp module 110, as a bias control voltage for the feedforward compensation current; another input Ctrl of the compensation module 120 is another output of the clamp module 110, 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 a preset voltage V2, one end of the compensation module 120 is connected to a preset current I1, and one output of the compensation module 120 is a current I cs1 , another output of the compensation module 120 is a current I cs2 .

[0046] PWM shutdown module 200, 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, and 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 pin CSN, the other end is connected to pin CSP, and the output is connected to pin CSOUT.

[0047] Figure 3 The working principle is as follows: the clamping module 110 is connected to a 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, Vbias and Ctrl signals are generated; 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 the pin CSN and the pin 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 over a wide voltage input range; at the same time, through the control of the preset voltage inside the compensation module 120, the consistency of the overcurrent point of the wide range of input voltage is adjusted, and a control signal Ctrl is output through the other end of the clamping module 110 to realize different coefficient compensation under different input voltages.

[0048] Figure 4 This is a basic circuit diagram of an embodiment of the clamp module 110 of the present invention. Figure 5 is a basic circuit diagram of an embodiment of the compensation module 120 of the present invention, Figure 6 It is a basic circuit principle block diagram of an embodiment of the PWM shutdown module 200 of the present invention.

[0049] Figure 4The clamp module 110 includes a PMOS tube PM1, a PMOS tube PM2, a PMOS tube PM10, a PMOS tube PM9, an NMOS tube NM1, an NMOS tube NM2, an NMOS tube 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 tube PM1, the gate of the PMOS tube PM1 and the drain of the PMOS tube PM1 are connected to the gate of the PMOS tube PM2, and are connected to the drain of the NMOS tube NM1; the source of the PMOS tube PM2 is connected to the pin UVP, and the drain of the PMOS tube PM2 is connected to the gate of the NMOS tube NM1 and the drain of the NMOS tube NM8. The gate and drain of NM2 and the gate of NMOS tube NM8 are connected, the drain of NMOS tube NM8 is connected to the drain of PMOS tube PM10 and the gate of PMOS tube PM10, the source of PMOS tube PM10 is connected to the power supply VCC, the drain of PMOS tube PM9 is connected to one end of resistor R2 and the positive end of comparator comp1, the negative end of comparator comp1 is connected to the preset voltage V2, the other end of resistor R2 is connected to the ground, the drain of NMOS tube NM2 is used as an output of the clamp module 110 to form a node Vbias; the output of comparator comp1 is used as another output of the clamp module 110 to form a node Ctrl; the sources of NMOS tubes NM1, NMOS tubes NM2 and NMOS tubes NM8 are connected to the reference ground.

[0050] Figure 5The compensation module 120 includes a PMOS tube PM3, a PMOS tube PM4, a PMOS tube PM5, a PMOS tube PM6, a PMOS tube PM7, a PMOS tube PM8, an NMOS tube NM3, an NMOS tube NM5, an NMOS tube NM6 and an NMOS tube NM7, wherein the drain of the NMOS tube NM7 is connected to the preset current I1, the gate of the PMOS tube PM3 is connected to the gate of the PMOS tube PM4, the gate of the PMOS tube PM5 is connected, the gate of the PMOS tube PM6 is connected to the gate of the PMOS tube PM7, the source of the PMOS tube PM3, the source of the PMOS tube PM4, the source of the PMOS tube PM5, the source of the PMOS tube PM6, and the PMOS tube PM7 are connected. 7 is connected to the reference power supply VCC; the gate of the PMOS tube PM3 is connected to the drain of the PMOS tube PM3 and the drain of the NMOS tube NM3; the gate of the NMOS tube NM3 is connected to an output Vbias of the clamping module 110; the drain of the PMOS tube PM4 forms a node Ics1 as an output of the compensation module 120; the drain of the PMOS tube PM5 is connected to the source of the PMOS tube PM8, and the gate of the PMOS tube PM8 is connected to another output node Ctrl of the clamping module 110; the drain of the PMOS tube PM8 is connected to the drain of the PMOS tube PM6 to form an output node Ics2; the drain of the PMOS tube PM4 forms an output node Ics1. The gate of the PMOS tube PM6, the gate of the PMOS tube PM7, and the drain of the PMOS tube PM7 are connected, the drain of the NMOS tube NM6 is connected to the gate of the NMOS tube NM6 and the gate of the NMOS tube 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.

[0051] Figure 6 It is an implementation scheme of the PWM shutdown module 200 of the present invention. The current sampling operational amplifier is connected to the pin CSP, the pin CSN, and the pin 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 tube NM8. The gate of the NMOS tube NM8 is connected to the gate of the NMOS tube NM9 and the gate of the NMOS tube NM10. The drain of the NMOS tube NM9 is connected to the gate. The drain input current I cs2, the 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 input 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 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 finally outputs the main power tube drive GTL.

[0052] Figure 7 Will Figure 4 and Figure 5 Draw together, the working principle is analyzed as follows: The received input voltage sampling signal is compared with the first preset voltage V1 to generate a bias voltage Vbias and a first control signal Ctrl. After 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 first compensation current Ics1 and the second compensation current Ics2 are generated by the bias voltage Vbias. The first compensation current Ics1 and the resistor R CSOUT Generate a feedforward compensation voltage, 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 voltage, and the third preset voltage V3 is subtracted from it to form an 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 is lower than the second preset voltage V2, the first control signal Ctrl is the ground voltage. The first control signal Ctrl turns off the first switch NM7 and turns on the second switch PM8. The first bias current IB1 follows the second compensation current Ics2 in a certain proportion. When the product of the second bias current IB2 and the second compensation resistor is higher than the second preset voltage V2, the first control signal Ctrl is the power supply voltage. The first control signal Ctrl turns on the first switch NM7 and turns off the third switch PM8. The second compensation current Ics2 is a certain proportion of the first preset current I1. Achieve consistency compensation of the overcurrent point of the switching power supply under high and low voltages, and achieve overcurrent point compensation of different switching power supplies by setting the first preset current I1. It can be specifically expressed by the following relationship: (1) The clamp module will current I UVPIn the compensation module, I is generated according to the mirror ratio K1 and K2. cs1 with I cs2 ,Right now (2) 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 selection of the proportional coefficient K1 can be changed through the setting of the current mirror device to achieve different compensation amounts.

[0053] The actual feedforward compensation can be expressed as: (3) 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, and the compensation amount is flexible and adjustable, ensuring the consistency of the overcurrent point of the switching power supply under different input voltages, solving the problem of difficulty in ensuring consistency of the overcurrent point in the switching power supply with a wide range of input, and the implementation method has fewer circuits, small area, low cost, and reliable function. The basic principle of its overcurrent point consistency compensation function is as follows: Under high and low input voltages, since the main control IC has the same driving delay, the overcurrent points are inconsistent when the input voltage is high and low. Consistency is particularly important for switching power supplies. The overcurrent point consistency compensation when the input voltage is high and low can be achieved through the following relationship: (4) The actual overcurrent point can be expressed as: (5) I cs2 The first bias current IB1 is generated by the current mirror device. 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 To achieve the 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 V OCP 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.

[0054] Figure 7The 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 it is greater than VFB_CS, the PWM comparator CMP_PWM outputs the Toff_L signal at a low level, which is sent to the reset terminal Clr_L of the D flip-flop DFF. The output terminal Q of the D flip-flop outputs a low level signal, and the GTL pin is at a low level. 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, at low input voltage, the added feedforward compensation voltage V LCS It will be relatively small and may not achieve the compensation effect. Therefore, in the design of switching power supply, 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, and the influence of input high and low voltage needs to be taken into account.

[0055] Figure 8 for Figure 7 An equivalent replacement circuit schematic diagram, such as Figure 8 As shown, Figure 7 The difference is that Figure 8 The drain of the PMOS tube 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 output signal of the comparator is generated is different. However, it can also represent 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 feed-forward voltage V CSOUT Only then it is produced.

[0056] 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 generated by the current mirror is generated in the resistor R CSOUT A suitable compensation value is generated on the surface 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.

[0057] 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.

[0058] 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 added by the input voltage, the overcurrent point compensation current is within the protection scope of this patent. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications made without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A feedforward compensation and overcurrent protection method, 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 the 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 The other end, the sampling resistor R CSP Connect the second current sampling pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sampling pin CSN and the sampling resistor R CS The signals of the second current sampling pin CSP and the third current sampling pin CSN are subtracted and amplified, and the output signal is superimposed on the first current sampling pin CSOUT to generate a 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 comprises: Receive the input voltage sampling signal V of the switching power supply in , compared with the first preset voltage V1: When V in When <V1, the voltage of input voltage detection pin UVP is controlled to follow the input voltage change, and the voltage divider does not generate the discharge current I UVP , so no feed-forward 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 generates 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 proportion; 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 is opposite to the change 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 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.

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 The 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 the 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 The other end, the sampling resistor R CSP Connect the second current sampling pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sampling pin CSN and the sampling resistor R CS The signals of the second current sampling pin CSP and the third current sampling pin CSN are subtracted and amplified, and the output signal is superimposed on the first current sampling pin CSOUT to generate a 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 comprises: 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 generates 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 proportion; 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 is opposite to the change 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 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.

11. The feedforward compensation and overcurrent protection device according to claim 10, characterized in that: The clamp module will discharge the current I UVP The 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 the 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 The other end, the sampling resistor R CSP Connect the second current sampling pin CSP and the sampling resistor R CS Between one end and the other, the sampling resistor R CSN Connect the third current sampling pin CSN and the sampling resistor R CS The signals of the second current sampling pin CSP and the third current sampling pin CSN are subtracted and amplified, and the output signal is superimposed on the first current sampling pin CSOUT to generate a 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 by: The switching power supply also includes the feedforward compensation and overcurrent protection device as described in 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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