Switching power supply controller and switching power supply converter

Abstract

The utility model discloses a switching power supply controller and a switching power supply converter. Comprising a switch control circuit, a drive circuit, a start control circuit and a delay circuit. The starting control circuit is used for sampling a direct-current input voltage to obtain a first sampling signal taking a second reference ground as a benchmark, converting the first sampling signal into a second sampling signal taking the first reference ground as the benchmark, and generating an effective starting indication signal when the second sampling signal is greater than a set threshold voltage; and the control circuit is used for delaying preset time to control the switch control circuit to enable to be started after receiving the effective starting indication signal. Through the design, it is ensured that the switching power supply converter starts to work after surge current limiting of the preceding-stage controller is finished, the system cost is reduced, the reliability and stability of the system are improved, and normal starting and running of the power supply converter are ensured.

Description

Technical Field

[0001] The utility model relates to the field of electronic technology, and more particularly to a switching power supply controller and a switching power supply converter. Background Art

[0002] Power over Ethernet (PoE), also known as PoE, is a technology that transmits power and data to devices over twisted-pair Ethernet cables. Compatible with existing Ethernet cabling infrastructure, PoE allows devices to be powered through their network ports, eliminating power cables and reducing wiring and hardware costs. PoE is currently widely used in video telephony, security, IoT devices, and other fields.

[0003] A Power over Ethernet system generally includes a Power Sourcing Equipment (PSE), a Powered Device (PD), and an Ethernet cable that transmits power and data between the two.

[0004] In a PoE power supply system, the powered device (PD) typically needs to convert the high-voltage AC power received from the Ethernet cable into a low-voltage DC power suitable for its internal circuitry. The flyback converter is a common power conversion topology, widely used in power management for PDs due to its simplicity, low cost, and high efficiency.

[0005] A flyback converter typically consists of a primary circuit and a secondary circuit. By controlling the on / off switching of the power switch in the primary circuit, a constant voltage is output on the secondary circuit. In a PoE system, the downstream switching power converter must only start operating after the inrush current limiting of the upstream powered device controller has expired. Otherwise, proper startup may occur. Therefore, the powered device controller typically outputs an enable signal to control the operating state of the downstream switching power converter. If the downstream switching power converter and the upstream powered device controller share a common ground, the enable signal from the powered device controller can be used to control the downstream switching power converter. However, if the powered device controller and the downstream switching power converter do not share a common ground, the enable signal from the powered device controller often needs to be level-converted before it can be used to control the downstream switching power converter. This not only increases the complexity of the control circuitry but also often requires a high-voltage BCD process to design the controller, increasing costs.

[0006] Figure 1 A system structure block diagram of a powered device according to the prior art is shown. Figure 2 FIG. 1 shows a circuit diagram of a switching power converter according to the prior art. Figure 1 and Figure 2 As shown, a conventional powered device 100 includes a rectifier bridge 110, a powered device controller 120, and a switching power converter 130, wherein the switching power converter 130 is implemented as a flyback converter. In conventional powered devices, by connecting the output ground of the powered device controller 120 to the ground terminal of the switching power converter 130, the powered device controller 120 can directly control the subsequent switching power converter 130 via the PG terminal, eliminating the need for a level conversion circuit between the two and reducing the complexity of the control circuit. However, this solution requires the addition of an auxiliary winding L3 to the switching power converter 130 to obtain output voltage feedback parameters. Due to the complex winding process of the auxiliary winding, this increases the production cost and difficulty of the flyback converter. Furthermore, the introduction of the auxiliary winding may cause electromagnetic interference within the circuit. Utility Model Content

[0007] In view of this, the purpose of the present invention is to provide a switching power supply controller and a switching power supply converter, which not only reduces system cost but also improves system reliability and stability, ensuring normal startup and operation of the power converter.

[0008] According to one aspect of the present invention, a switching power supply controller is provided for controlling a power switch in a switching power supply converter, the switching power supply converter being configured to generate a DC output voltage based on a DC input voltage. The switching power supply controller includes: a switch control circuit for generating a switch control signal based on a current sampling signal and a feedback signal of the DC output voltage; a drive circuit for receiving the switch control signal and generating a switch drive signal to turn the power switch on or off; a startup control circuit connected between the DC input voltage and a second reference ground, for sampling the DC input voltage to obtain a first sampling signal based on the second reference ground, converting the first sampling signal into a second sampling signal based on the first reference ground, and generating a valid startup indication signal when the second sampling signal is greater than a set threshold voltage, the first reference ground being different from the second reference ground; and a delay circuit connected to the startup control circuit for delaying, after receiving the valid startup indication signal, outputting a valid enable control signal to the switching control circuit for a preset time to enable the switching control circuit.

[0009] Optionally, the switching power converter further includes a first capacitor connected between the DC input voltage and the first reference ground, and the preset time is set according to the time required for the first capacitor to charge to a platform voltage.

[0010] Optionally, the first sampling signal includes a first sampling voltage, the second sampling signal includes a second sampling voltage, and the startup control circuit includes: an N-order filtering module connected between the DC input voltage and the second reference ground, for converting the first sampling voltage into a second sampling voltage, where N is an integer greater than or equal to 1; a first voltage divider module, for dividing the second sampling voltage to obtain a first voltage-divided signal of the second sampling voltage; and a first comparator, whose non-inverting input terminal is used to receive the first voltage-divided signal, the inverting input terminal is used to receive a first reference voltage representing the threshold voltage, and the output terminal is used to output the startup indication signal.

[0011] Optionally, the switch control circuit includes: a first sampling and holding module, used to sample and hold the feedback signal according to the switch control signal to obtain a third sampling voltage; an error amplifier, whose non-phase input terminal is used to receive the second reference voltage, the inverting input terminal is used to receive the third sampling voltage, and the output terminal is used to output an error signal; a second comparator, whose non-phase input terminal is used to receive the current sampling signal, the inverting input terminal is used to receive the error signal, and the output terminal is used to output a comparison signal; and an RS trigger, whose set terminal is used to receive a clock signal, the reset terminal is used to receive the comparison signal, and the output terminal is used to provide the switch control signal.

[0012] Optionally, the switch control circuit further includes: a switching frequency control module, configured to generate the clock signal according to the error signal, wherein the switching frequency of the switch drive signal is set by the clock frequency of the clock signal.

[0013] Optionally, the first sampling signal is a first sampling voltage, the second sampling signal is a fourth sampling voltage, and the startup control circuit includes: a second voltage divider module, used to divide the first sampling voltage to obtain a second voltage divider signal; a second sampling and holding module, used to sample and hold the second voltage divider signal according to the switch drive signal to obtain the fourth sampling voltage; and a third comparator, whose non-phase input terminal is used to receive the fourth sampling voltage, the inverting input terminal is used to receive a first reference voltage representing the threshold voltage, and the output terminal is used to output the startup indication signal.

[0014] Optionally, the switching power supply controller further includes: a power supply circuit, configured to provide a power supply voltage to the switching control circuit according to the DC input voltage.

[0015] Optionally, the first reference ground is a fixed ground, and the second reference ground is a floating ground.

[0016] Optionally, the switching power converter further includes: a current sampling resistor connected to the second end of the power switch tube, and the current sampling resistor is used to provide the current sampling signal to the switching power controller.

[0017] Optionally, it further includes: a current sampling circuit connected to the first end of the power switch tube, for generating the current sampling signal.

[0018] According to another aspect of the present invention, a switching power supply converter is provided, comprising: a power switch tube; and the above-mentioned switching power supply controller.

[0019] Optionally, the switching power converter is one of a floating Buck-Boost topology, a floating Buck topology, a Boost topology and a flyback topology.

[0020] In summary, the present invention provides a switching power supply controller that samples the DC input voltage through a startup control circuit to obtain a first sampled voltage referenced to a floating ground. This first sampled voltage is then converted into a second sampled voltage referenced to the fixed ground of a preceding controller. This allows the DC input voltage to be compared with a threshold voltage referenced to the fixed ground, enabling the subsequent switching power supply converter to begin operating after the preceding controller's inrush current limiting has ended. This design ensures that the switching power supply converter begins operating only after the preceding controller's inrush current limiting has ended, thus avoiding the problem of the switching power supply converter failing to start normally.

[0021] In addition, in some embodiments of the present invention, the switching power supply converter sets the power switch tube and the switching power supply controller on the high side and the primary winding on the low side, so that the switching power supply controller and the power switch tube both use the floating ground end as the reference ground, thereby reducing the difficulty of the drive design and the cost of the chip.

[0022] In addition, the switching power supply controller of the present invention is also used to delay the setting time before turning on after the second sampling voltage is greater than the threshold voltage, thereby avoiding the problem that the switching power supply converter cannot output the target output voltage due to the need to charge the large capacitor at the DC input voltage, ensuring the normal startup and operation of the switching power supply converter

[0023] Furthermore, in some other embodiments of the present invention, the switching power supply controller and the preceding controller are not grounded. Compared to conventional solutions, this allows output voltage sampling solely through the primary winding, eliminating the need for an auxiliary winding in the circuit. This significantly reduces the production cost and difficulty of the flyback converter. Furthermore, the absence of an auxiliary winding reduces electromagnetic interference within the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0025] Figure 1 A system structure block diagram of a powered device according to the prior art is shown.

[0026] Figure 2 FIG. 1 is a circuit diagram of a switching power converter according to the prior art.

[0027] Figure 3 A system structure block diagram of a powered device according to a first embodiment of the present invention is shown.

[0028] Figure 4 Show Figure 3 Schematic diagram of the switching power supply controller.

[0029] Figure 5 Show Figure 4 Schematic diagram of the startup control circuit.

[0030] Figure 6 Show Figure 4 Schematic diagram of the switch control circuit in .

[0031] Figure 7 Show Figure 5 Input and output waveforms of the startup control circuit in .

[0032] Figure 8 Show Figure 4 Waveform diagram of the start indication signal and enable control signal in .

[0033] Figure 9 Show Figure 6 Working waveform of the switch control circuit in .

[0034] Figure 10 A system structure block diagram of a powered device according to a second embodiment of the present invention is shown.

[0035] Figure 11 A system structure block diagram of a powered device according to a third embodiment of the present invention is shown.

[0036] Figure 12 Show Figure 11 Schematic diagram of the switching power supply controller.

[0037] Figure 13 A system structure block diagram of a powered device according to a fourth embodiment of the present invention is shown.

[0038] Figure 14 A system structure block diagram of a powered device according to a fifth embodiment of the present invention is shown.

[0039] Figure 15 Show Figure 14 Schematic diagram of the switching power supply controller.

[0040] Figure 16 Show Figure 15 Schematic diagram of the startup control circuit.

[0041] Figure 17 Show Figure 15 Input and output waveforms of the startup control circuit in .

[0042] Figure 18 Show Figure 16 Waveform diagram of the start indication signal and enable control signal in .

[0043] Figure 19 Show Figure 15 Working waveform of the switch control circuit in .

[0044] Figure 20 A system structure block diagram of a powered device according to a sixth embodiment of the present invention is shown.

[0045] Figure 21 Show Figure 20 Schematic diagram of the switching power supply controller.

[0046] Figure 22 A structural block diagram of an Ethernet power supply system according to a seventh embodiment of the present utility model is shown. DETAILED DESCRIPTION

[0047] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, identical elements are represented by identical or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0048] The present invention may be embodied in various forms, some examples of which will be described below.

[0049] Figure 3 FIG. 1 shows a system structure block diagram of a powered device according to an embodiment of the present utility model. Figure 3 As shown, the powered device (powered device) 200 of this embodiment includes a rectifier bridge 210 , a powered device controller 220 , a first capacitor Cp, and a switching power converter 230 .

[0050] The rectifier bridge 210 is used to rectify the AC input voltage to obtain a DC input voltage Vin.

[0051] The powered device controller 220 is connected between the DC input voltage Vin and the reference ground GND1. It is used to perform a handshake protocol with the power sourcing equipment (PSE) in the PoE system, obtain the required energy, and then output it to the subsequent switching power converter 230. For example, when the powered device 200 is connected to an Ethernet cable, the powered device controller 220 communicates with the PSE to confirm the device's presence and determine its power requirements, ensuring that the PSE can provide appropriate power without overloading or damaging the network. The powered device controller also has protection functions, monitoring various parameters during power transmission, such as current, voltage, and temperature. If an abnormality is detected, the powered device controller will quickly take action, such as disconnecting power or adjusting power output, to protect the powered device and the entire PoE system. Furthermore, the powered device controller 220 supports various PoE standards and protocols, such as IEEE 802.3af, IEEE 802.3at, and IEEE 802.3bt. These standards specify different power levels and communication methods, and the powered device controller needs to be compatible with these standards to ensure interoperability with various PSE devices.

[0052] Capacitor Cp is provided between the powered device controller 220 and the switching power converter 230 and is connected between the DC input voltage Vin and the first reference ground GND1. First capacitor Cp is used to smooth and filter the DC input voltage Vin and absorb inrush current during startup of the powered device controller 220. For example, first capacitor Cp may be an electrolytic capacitor or a ceramic capacitor.

[0053] The switching power converter 230 is used to perform power conversion and regulation functions, converting the DC input voltage Vin into a DC output voltage Vout suitable for the powered device, so as to minimize energy loss and ensure stable operation of the device.

[0054] Specifically, the first embodiment of the present invention provides a switching power converter 230 with a flyback topology without an auxiliary winding, including a switching power controller 231, a power switch Q1, a transformer T1 (including a primary winding L1 and a secondary winding L2), a current sampling resistor Rcs, a freewheeling diode D1, an output capacitor Co, and a feedback circuit 233. The switching power converter 230 is configured to convert a DC input voltage Vin into a DC output voltage Vout to provide an output current Iout to a load Ro, and the switching power controller 231 is configured to control the operating state of the power switch Q1.

[0055] In particular, a first terminal of the power switch Q1 (e.g., a transistor, a field-effect transistor, a thyristor, etc.) is connected to a DC input voltage Vin, a second terminal of the power switch Q1 is connected to a first terminal of a current sampling resistor Rcs and a current detection terminal of a switching power supply controller 231, a second terminal of the current sampling resistor Rcs is connected to a second reference ground VS (illustratively, the reference ground VS is a floating ground), and a control terminal of the power switch Q1 is connected to a drive terminal of the switching power supply controller 231 to receive a switch drive signal DRV. The power switch Q1 is configured to control the transmission of power from the input terminal to the output terminal based on the switch drive signal DRV. In an exemplary embodiment, the power switch Q1 is an NMOS transistor, whose first terminal, second terminal, and control terminal are respectively a drain, a source, and a gate. Of course, the present invention is not limited to this. In other embodiments, the power switch Q1 may be a PMOS transistor, whose first terminal, second terminal, and control terminal are respectively a source, a drain, and a gate.

[0056] A first end of the primary winding L1 is connected to the reference ground VS, and a second end is connected to the reference ground GND1. The anode of the diode D1 is connected to the first end of the secondary winding L2, the cathode of the diode D1 is connected to the first end of the output capacitor Co and the load Ro, and the second end of the output capacitor Co is connected to the second end of the secondary winding L2 and the reference ground GND2.

[0057] Feedback circuit 233 is connected between reference ground VS and reference ground GND1 and is configured to divide the DC output voltage Vout to generate a feedback signal FB. For example, feedback circuit 233 includes resistors R1 and R2 connected in series between reference ground VS and reference ground GND1. The node between resistors R1 and R2 is configured to provide the feedback signal FB.

[0058] The current sampling resistor Rcs is used to sample the current flowing through the power switch Q1 to obtain a current sampling signal CS. The intermediate node between the power switch Q1 and the current sampling resistor Rcs is used to output the current sampling signal CS. Of course, the present invention is not limited to this method, and those skilled in the art may also select other current sampling methods to obtain the current in the power switch Q1 according to actual circumstances.

[0059] The switching power supply controller 231 is connected to the DC input voltage Vin, the feedback signal FB, the current sampling signal CS and the reference ground VS, and is used to generate a switch drive signal DRV according to the feedback signal FB and the current sampling signal CS, and provide it to the control end of the power switch tube Q1.

[0060] exist Figure 3In the embodiment, the ground terminal of the powered device controller 220 is connected to the reference ground GND1, and the ground terminal of the switching power supply controller 231 is connected to the reference ground VS. Since these two controllers are connected to different grounds, the powered device controller cannot be used to directly control the subsequent switching power converter. Therefore, the switching power supply controller 231 of this embodiment is further configured to sample the DC input voltage Vin to obtain a first sampled voltage relative to the reference ground VS, convert the first sampled voltage to a second sampled voltage relative to the reference ground GND1, compare the second sampled voltage with a set threshold voltage, and enable the switching power converter when the second sampled voltage exceeds the threshold voltage. This avoids the problem of the powered device controller 220 starting to operate while still in the inrush current limiting phase, which could cause the entire PoE system to fail to start normally, thereby improving circuit reliability.

[0061] Furthermore, the switching power supply controller 231 is further configured to enable the switching power converter after a preset time has passed since the second sampled voltage exceeds the threshold voltage, ensuring that the power converter begins operation after the inrush current limiting of the powered device controller ends. This prevents insufficient PoE energy from charging capacitor Cp at startup, preventing the target output voltage from being output, thereby further improving circuit reliability. For example, the preset time can be set based on the time required for capacitor Cp to charge to the platform voltage.

[0062] Figure 4 FIG. 1 shows a schematic diagram of the structure of a switching power supply controller according to an embodiment of the present invention. Figure 4 As shown, the switching power supply controller 231 of this embodiment includes: a switching control circuit 301 , a startup control circuit 302 , a delay circuit 303 , a power supply circuit 304 and a drive circuit 305 .

[0063] The switch control circuit 301 is configured to generate a switch control signal PWM for controlling the switching operation of the power switch Q1 based on the current sampling signal CS and the feedback signal FB, thereby stabilizing the DC output voltage Vout at a set value. In an exemplary embodiment, for a switching power supply controller operating in a constant off-time control (COT) mode, the switch control circuit 301 controls the turn-on timing of the power switch Q1 based on a set clock signal, and controls the turn-off timing of the power switch Q1 based on the feedback signal FB and the current sampling signal CS.

[0064] The startup control circuit 302 is connected between a DC input voltage Vin and a reference ground VS, and is configured to sample the DC input voltage Vin to obtain a first sampled voltage Va1, convert the first sampled voltage Va1 into a second sampled voltage Va2, and generate a valid (e.g., high level) startup indication signal POR when the second sampled voltage Va2 is greater than the threshold voltage.

[0065] The delay circuit 303 is connected to the start control circuit 302, and is used to start timing when receiving the valid start indication signal POR, and provide a valid (for example, high level) enable control signal EN to the switch control circuit 301 after the timing reaches the preset time, so as to control the switch control circuit 301 to be enabled and turned on.

[0066] The power supply circuit 304 is connected to the DC input voltage Vin and is used to provide a power supply voltage Vcc to the switch control circuit 301 according to the DC input voltage Vin. In addition, the switching power supply controller 231 also includes an input capacitor Cin connected between the power supply terminal of the switch control circuit 301 and the reference ground VS.

[0067] The input end of the drive circuit 305 is connected to the output end of the switch control circuit 301, and the output end of the drive circuit 305 is connected to the control end of the power switch tube Q1. The drive circuit 305 is used to enhance and amplify the switch control signal PWM to generate a switch drive signal DRV applied to the control end of the power switch tube Q1 to control the conduction and shutdown of the power switch tube Q1.

[0068] Figure 5 FIG. 1 shows a schematic diagram of the structure of the startup control circuit according to an embodiment of the present utility model. Figure 5 As shown, the startup control circuit 302 of this embodiment includes an N-th order filter module 3021 , a voltage divider module 3022 , a comparator CMP, and a reference module 3023 .

[0069] The N-order filter module 3021 is connected between the DC input voltage Vin and the reference ground VS, and is used to convert the first sampled voltage Va1 into the second sampled voltage Va2, where N is an integer greater than / equal to 1. For example, the N-order filter module 3021 includes N RC filter units cascaded in sequence, where the first RC filter unit includes a resistor R11 and a capacitor C11, which are connected in series between the DC input voltage Vin and the reference ground VS. The second RC filter unit includes a resistor R12 and a capacitor C12, which are connected in series between the middle node of the resistor R11 and the capacitor C11 and the reference ground VS. Similarly, the last RC filter unit includes a resistor R1N and a capacitor C1N, and the middle node of the resistor R1N and the capacitor C1N is used to output the second sampled voltage Va2.

[0070] The voltage divider module 3022 is configured to divide the second sampled voltage Va2 to obtain a voltage divider signal Vb1 of the second sampled voltage Va2. The reference module 3023 is configured to provide a first reference voltage Vref1 representing the threshold voltage. The comparator CMP has a non-inverting input terminal configured to receive the voltage divider signal Vb1, and an inverting input terminal configured to receive the first reference voltage Vref1. The comparator CMP is configured to compare the voltage divider signal Vb1 with the first reference voltage Vref1 to provide a start indication signal POR at its output terminal. When the voltage divider signal Vb1 is greater than the first reference voltage Vref1, indicating that the second sampled voltage Va2 is greater than the threshold voltage (e.g., 36V), the comparator CMP outputs a valid (e.g., high) start indication signal POR.

[0071] In this embodiment, the N-order filtering module 3021 is used to integrate and average the first sampling voltage Va1 (Va1=Vin-VS, when the voltage difference of the current sampling circuit is ignored, the first sampling voltage can also be referred to as the voltage difference between the drain and source of the power switch tube Q1) over time to obtain the second sampling voltage Va2.

[0072] Assume that the voltages at the two input terminals of the N-order filter module 3021 are the first sampling voltage Va1 = Vin-VS, the voltage across the capacitor Cp connected between the DC input voltage Vin and the reference ground GND1 is Vp, and the voltage across the primary winding when the power switch Q1 is turned off is VOR.

[0073] According to Figure 4 It can be obtained that when the power switch Q1 is turned off:

[0074] Vin―GND1=Vp (1)

[0075] GND1―VS=VOR (2)

[0076] By adding formulas (1) and (2), we can obtain:

[0077] Vin―VS=Vp+VOR (3)

[0078] When the power tube Q1 is turned on, the voltage on the current sampling resistor Rcs is very small and can be ignored, so Vin-VS=0.

[0079] Figure 7 shows the input and output waveforms of the startup control circuit according to an embodiment of the present utility model, Figure 7 3 and 4 show the waveforms of the input voltage Vin-VS and the switch drive signal DRV of the startup control circuit 302, respectively. Figure 7 As shown in Figure 1, when the switch drive signal DRV is high, the power switch Q1 is turned on; when the switch drive signal DRV is low, the power switch Q1 is turned off. The ratio of the on-time to the switching cycle time (i.e., the duty cycle) is D. Therefore, according to the above content and Figure 7 It can be seen that when the switch driving signal DRV is at a high level, Vin-VS=0; when the switch driving signal DRV is at a low level, Vin-VS=Vp+VOR.

[0080] The N-order filter module 3021 integrates Vin-VS over time and averages it (which can also be understood as filtering). The resulting output voltage is:

[0081] Va2=(Vp+VOR)*(1―D) (4)

[0082] Furthermore, when the power switch Q1 is turned on, the voltage across the primary winding L1 of the transformer T1 is Vin-GND1; when the power switch Q1 is turned off, the voltage across the primary winding L1 of the transformer T1 is VOR. According to the volt-second balance principle, we can obtain:

[0083] (Vin―GND1)*D=VOR*(1―D) (5)

[0084] Substituting formula (1) into formula (5), we can obtain:

[0085] Vp*D=VOR*(1―D) (6)

[0086] From formula (6), we can get:

[0087] VOR=Vp*D / (1―D) (7)

[0088] Substituting formula (7) into formula (4), we can obtain:

[0089] Va2=Vp=Vin―GND1.

[0090] It can be seen that the N-th order filter module 3021 converts the input voltage (Vin-VS) based on the reference ground VS into the output voltage (Vin-GND1) based on the reference ground GND1.

[0091] Figure 6 FIG. 1 shows a schematic diagram of the structure of a switch control circuit according to an embodiment of the present utility model. Figure 6 As shown, the switch control circuit 301 of this embodiment includes a sample and hold module 3011 , an error amplifier P1 , a comparator P2 , a switching frequency control module 3012 and an RS trigger 3013 .

[0092] The sampling and holding module 3011 is configured to sample and hold the feedback signal FB according to the switch control signal PWM to obtain a third sampled voltage Va3. For example, the sampling and holding module 3011 is configured to sample the feedback signal FB when the switch control signal PWM is at a low level, and hold the sampled voltage when the switch control signal PWM is at a low level, thereby obtaining the third sampled voltage Va3.

[0093] The non-inverting input terminal of the error amplifier P1 is used to receive the second reference voltage Vref2, and the inverting input terminal is used to receive the third sampling voltage Va3. The error amplifier P1 is used to amplify the difference between the second reference voltage Vref2 and the third sampling voltage Va3 to obtain an error signal Comp.

[0094] The comparator P2 has a positive input terminal for receiving the current sampling signal CS and an inverting input terminal for receiving the error signal Comp. The comparator P2 is configured to compare the current sampling signal CS with the error signal Comp to generate a comparison signal. For example, the comparison signal is a square wave signal switching between high and low levels.

[0095] The switching frequency control module 3012 is used to control the internal oscillator to generate the clock signal CLK according to the level amplitude of the error signal Comp, and provide the clock signal CLK with a certain clock frequency to the RS flip-flop 3013.

[0096] The set terminal S of the RS flip-flop 3013 is used to receive the clock signal CLK, the reset terminal R is connected to the output terminal of the comparator P2 to receive the comparison signal, and the output terminal Q is used to output the switch control signal PWM. For example, the RS flip-flop 3013 is configured to set the switch control signal PWM to a high level when the rising edge of the clock signal CLK at the set terminal S arrives, thereby turning on the power switch Q1. When the current sampling signal CS is greater than the error signal Comp, the comparator P2 outputs a high level, and the RS flip-flop 3013 sets the switch control signal PWM to a low level based on the high level at the reset terminal R, thereby turning off the power switch Q1. When the next rising edge of the clock signal CLK arrives, the RS flip-flop 3013 again sets the switch control signal PWM to a high level, and so on. It can be seen that the switching frequency of the switch control signal PWM in this embodiment can be set by the clock frequency of the clock signal CLK.

[0097] Figure 8 shows a waveform diagram of the start indication signal and the enable control signal according to an embodiment of the present utility model, Figure 8 , respectively, show the waveforms of the second sampling voltage Va2, the start indication signal POR, and the enable control signal EN. Figure 8 As shown, before time t1, the PoE system has not yet been turned on. At this time, the second sampling voltage Va2 is 0, so the start indication signal POR and the enable control signal EN are both low. The period between time t1 and t3 is the surge current limiting stage. At this time, the PoE system is turned on, the output voltage of the rectifier bridge charges the capacitor Cp, the voltage on the capacitor Cp rises linearly, and the second sampling voltage Va2 rises linearly. At time t2, the second sampling voltage Va2 rises to the set threshold voltage, and the start indication signal POR flips to a high level. At time t3, the voltage on the capacitor Cp rises to the platform voltage (for example, 48V), and the surge current limiting ends. The time t2-t4 is the delay time set by the delay circuit. After the preset delay time, the enable control signal EN flips to a valid level (for example, a high level), so that the switch control circuit controls the power switch tube Q1 to start working.

[0098] Figure 9 FIG. 1 shows the working waveform of the switch control circuit according to the embodiment of the present utility model. Figure 9As shown, during the on-time Ton, the switch drive signal DRV is at a high level, the power switch tube Q1 is turned on, and the voltage across the current sampling resistor Rcs rises. At this time, the current sampling signal CS is still very small, and the voltage of the primary winding L1 sampled by the voltage feedback circuit 233 is a negative voltage. Since there is a reverse diode clamp inside the switching power supply controller, the negative voltage is clamped at -0.7V to prevent the negative voltage from damaging the chip. During the off-time Toff, the switch drive signal DRV is at a low level, so the power switch tube Q1 is turned off, and the primary winding L1 is positive at the bottom and negative at the top, so the voltage sampled by the voltage feedback circuit 233 is a positive value. In addition, it should be noted that Figure 9 FIG. 1 shows a voltage waveform when the switch control circuit is in the DCM mode. Therefore, after the off time Toff, the feedback signal FB has a voltage fluctuation.

[0099] Figure 10 A system structure block diagram of a powered device according to a second embodiment of the present invention is shown. Figure 10 The illustrated embodiment illustrates an application of the switching power supply controller of the first embodiment to a switching power supply converter in a flyback topology with an auxiliary winding. Specifically, the powered device 300 includes a rectifier bridge 310, a powered device controller 320, a first capacitor Cp, and a switching power supply converter 330. The rectifier bridge 310 and powered device controller 320 of this embodiment are identical to the rectifier bridge 210 and powered device controller 220 of the first embodiment and are not further described here.

[0100] The switching power converter 330 of this embodiment differs from the switching power converter 230 of the first embodiment only in that a first end of the primary winding L1 of the transformer T1 in the switching power converter 330 is connected to the output terminal of the rectifier bridge, a second end of the primary winding L1 is connected to the DRAIN terminal of the switching power controller 331 and the first end of the power switch Q1, a second end of the sampling resistor Rcs is connected to the reference ground GND1, and the transformer T1 further includes an auxiliary winding L3. A first end of the auxiliary winding L3 is connected to the power supply terminal Vcc of the switching power controller 331 via a diode D2, and a second end of the auxiliary winding L3 is connected to the reference ground GND1. A feedback circuit 333 is configured to divide the voltage of the auxiliary winding L3 to generate the feedback signal FB. Otherwise, the switching power controller 331 of this embodiment is substantially identical to the switching power controller 231 of the first embodiment and will not be further described herein.

[0101] Figure 11 A system structure block diagram of a powered device according to a third embodiment of the present utility model is shown. Figure 11The illustrated embodiment provides an example of a flyback topology switching power converter for a powered device, without a current sampling resistor Rcs and an auxiliary winding. Specifically, the powered device 400 includes a rectifier bridge 410, a powered device controller 420, a capacitor Cp, and a switching power converter 430. Similarly, the rectifier bridge 410 and powered device controller 420 of this embodiment are identical to the rectifier bridge 210 and powered device controller 220 of the first embodiment and are not further described here.

[0102] The difference between the switching power converter 430 of this embodiment and the switching power converter 230 of the first embodiment is that the switching power converter 430 does not have a current sampling resistor Rcs, that is, the second end of the power switch tube Q1 is directly connected to the first end of the primary winding L1 and the floating reference ground terminal VS of the switching power controller 431, and the switching power controller 431 does not have a current detection terminal CS.

[0103] Figure 12 Show Figure 11 The structural diagram of the switching power supply controller in FIG. Figure 12 As shown, the switching power supply controller 431 of this embodiment is Figure 4 The difference between the switching power supply controller 231 shown in FIG4 is that the switching power supply controller 431 further includes a current sampling circuit 306, wherein the current sampling circuit 306 is connected to the first end of the power switch tube Q1 and is configured to obtain a current sampling signal CS representing peak current information of the switching power converter based on the drain-source voltage difference of the power switch tube Q1, and provide the current sampling signal CS to the switch control circuit 301. Specifically, the current sampling circuit 306 synchronously samples the drain-source voltage difference of the power switch tube Q1 according to the turn-on and turn-off actions of the power switch tube Q1 to obtain the current sampling signal CS.

[0104] Figure 13 A system structure block diagram of a powered device according to a fourth embodiment of the present invention is shown. Figure 13 The illustrated embodiment illustrates an application of the switching power supply controller of the third embodiment to a switching power supply converter in a flyback topology with an auxiliary winding. Specifically, the powered device 500 includes a rectifier bridge 510, a powered device controller 520, a capacitor Cp, and a switching power supply converter 530. The rectifier bridge 510 and powered device controller 520 of this embodiment are identical to the rectifier bridge 410 and powered device controller 420 of the third embodiment and are not further described here.

[0105] The switching power converter 530 of this embodiment differs from the switching power converter 430 of the third embodiment only in that the primary winding L1 of the transformer T1 in the switching power converter 530 is connected between the output of the rectifier bridge and the first terminal of the power switch Q1. The connection node between the first terminal of the power switch Q1 and the primary winding L1 serves as the DRAIN terminal of the switching power controller 531. The startup control circuit in the switching power controller 531 receives a DC input voltage Vin from the DRAIN terminal, and the current sampling circuit in the switching power controller 531 also receives the voltage Vin at the first terminal of the power switch Q1 from the DRAIN terminal. The transformer T1 also includes an auxiliary winding L3. The first terminal of the auxiliary winding L3 is connected to the power supply terminal Vcc of the switching power controller 531 via a diode D2, and the second terminal of the auxiliary winding L3 is connected to the reference ground GND1. The feedback circuit 533 is used to divide the voltage of the auxiliary winding L3 to generate the feedback signal FB. Otherwise, the switching power controller 531 of this embodiment is substantially identical to the switching power controller 431 of the first embodiment and will not be further described here.

[0106] Figure 14 FIG. 5 shows a system structure block diagram of a powered device according to a fifth embodiment of the present invention. Figure 14 , shows a powered device 600 with a step-down switching power converter topology using a current sampling resistor. Specifically, the powered device 600 includes a rectifier bridge 610, a powered device controller 620, a capacitor Cp, and a switching power converter 630. The rectifier bridge 610 and powered device controller 620 of this embodiment are identical to the rectifier bridge 210 and powered device controller 220 of the first embodiment and are not further described here.

[0107] The switching power converter 630 of this embodiment differs from the switching power converter 230 of the first embodiment only in that the switching power converter 630 includes a power switch Q1, a current sampling resistor Rcs, an inductor L1, a freewheeling diode D1, and an output capacitor Co. A first terminal of the power switch Q1 (e.g., a transistor, a field-effect transistor, a thyristor, etc.) is connected to a DC input voltage Vin, a second terminal of the power switch Q1 is connected to a first terminal of the current sampling resistor Rcs and a current detection terminal of a switching power controller 631, a second terminal of the current sampling resistor Rcs is connected to a reference ground VS (illustratively, the reference ground VS is a floating ground), and a control terminal of the power switch Q1 is connected to a drive terminal of the switching power controller 631 to receive a switch drive signal DRV. The power switch Q1 is configured to control power transmission from an input terminal to an output terminal based on the switch drive signal DRV. A first end of the inductor L1 is connected to the reference ground VS, a second end is connected to the output capacitor Co and the first end of the load Ro, a cathode of the diode D1 is connected to the reference ground VS and the first end of the inductor L1, and an anode of the diode D1 is connected to the second end of the output capacitor Co and the load Ro and the reference ground GND1.

[0108] Feedback circuit 633 is connected between the two ends of inductor L1 and is used to divide the voltage of inductor L1 to obtain the feedback signal FB. For example, feedback circuit 633 includes resistors R1 and R2 connected in series between the two ends of inductor L1, and the middle node between resistors R1 and R2 is used to provide the feedback signal FB.

[0109] The current sampling resistor Rcs is used to sample the current flowing through the power switch Q1 to obtain a current sampling signal CS. The intermediate node between the power switch Q1 and the current sampling resistor Rcs is used to output the current sampling signal CS. Of course, the present invention is not limited to this method, and those skilled in the art may also select other current sampling methods to obtain the current in the power switch Q1 according to actual circumstances.

[0110] The switching power supply controller 631 is connected to the DC input voltage Vin, the feedback signal FB, the current sampling signal CS and the reference ground VS, and is used to generate a switch drive signal DRV according to the feedback signal FB and the current sampling signal CS, and provide it to the control end of the power switch tube Q1.

[0111] Figure 15 Show Figure 14 The structural diagram of the switching power supply controller in FIG. Figure 15As shown, the switching power supply controller 631 includes a switching control circuit 401, a startup control circuit 402, a delay circuit 403, a power supply circuit 404, and a drive circuit 405. The switching control circuit 401, the delay circuit 403, the power supply circuit 404, and the drive circuit 405 are identical to the switching control circuit 301, the delay circuit 303, the power supply circuit 304, and the drive circuit 305 of the first embodiment, and are not described in detail here.

[0112] Figure 16 Show Figure 15 The schematic diagram of the startup control circuit in FIG. Figure 16 As shown, the startup control circuit 402 of this embodiment includes a voltage divider module 4021 , a sample and hold module 4022 , a comparator CMP, and a reference module 4023 .

[0113] Among them, the voltage divider module 4021 is connected between the DC input voltage Vin and the reference ground VS, and is used to divide the first sampling voltage Va1 (Va1=Vin-VS, when the voltage difference of the current sampling circuit is ignored, the first sampling voltage can also be referred to as the voltage difference between the drain and source of the power switch tube Q1) to obtain a divided voltage signal Vb2 of the first sampling voltage.

[0114] The sampling and holding module 4022 is used to sample and hold the high level voltage of the divided voltage signal Vb2 of the first sampling voltage according to the switch driving signal DRV to obtain the fourth sampling voltage Va4, which represents the converter input voltage information based on the reference ground GND1. Figure 17 Show Figure 15 The input and output waveforms of the startup control circuit in FIG1 are as follows: when the switch drive signal DRV of the power switch tube Q1 is high, the power switch tube Q1 is turned on, and Vin-VS = 0V; when the switch drive signal DRV of the power switch tube Q1 is low, the power switch tube Q1 is turned off, the inductor L1 continues to flow, and the diode D1 is turned on, and Vin-VS = Vp + VF (where VF is the forward voltage drop of the diode D1, and Vp = Vin-GND1). That is, the sampling and holding module 4022 of this embodiment obtains the input voltage of the switching power converter by recording the voltage information of Vin-VS after the power switch tube Q1 is turned off. Assuming that the voltage divider ratio of the voltage divider module is K2, the output voltage of the sampling and holding module 4022 is Va4 = K2*(Vp+VF).

[0115] The reference module 4023 is configured to provide a first reference voltage Vref1 representing the threshold voltage. A comparator CMP has a non-inverting input terminal configured to receive the fourth sampled voltage Va4, and an inverting input terminal configured to receive the first reference voltage Vref1. The comparator CMP is configured to compare the fourth sampled voltage Va4 with the first reference voltage Vref1 to provide a startup indication signal POR at its output terminal. When the fourth sampled voltage Va4 is greater than the first reference voltage Vref1, indicating that the input voltage of the switching power converter is greater than the threshold voltage (e.g., 36V), the comparator CMP outputs a valid (e.g., high) startup indication signal POR.

[0116] Figure 18 Show Figure 16 The waveform diagram of the start indication signal and enable control signal in Figure 18 , respectively, show the waveforms of the fourth sampling voltage Va4, the start indication signal POR, and the enable control signal EN. Figure 18 As shown, before time t1, the PoE system has not yet been turned on. At this time, the fourth sampling voltage Va4 is 0, so the start indication signal POR and the enable control signal EN are both low. The period between time t1 and t3 is the surge current limiting stage. At this time, the PoE system is turned on, the output voltage of the rectifier bridge charges the capacitor Cp, the voltage on the capacitor Cp rises linearly, and the fourth sampling voltage Va4 rises linearly. At time t2, the fourth sampling voltage Va4 rises to the set threshold voltage, and the start indication signal POR flips to a high level. At time t3, the voltage on the capacitor Cp rises to the platform voltage (for example, 48V), and the surge current limiting ends. Time t2-t4 is the delay time set by the delay circuit. After the preset delay time, the enable control signal EN flips to a valid level (for example, a high level), causing the switch control circuit to control the power switch tube Q1 to start working.

[0117] Figure 19 Show Figure 15 The working waveform of the switch control circuit in FIG. Figure 19 As shown, during the on-time Ton, the switch drive signal DRV is at a high level, the power switch tube Q1 is turned on, and the voltage across the current sampling resistor Rcs rises. At this time, the current sampling signal CS is still very small, and the voltage of the inductor L1 sampled by the voltage feedback circuit 633 is a negative voltage. Since there is a reverse diode clamp inside the switching power supply controller, the negative voltage is clamped at -0.7V to prevent the negative voltage from damaging the chip. During the off-time Toff, the switch drive signal DRV is at a low level, so the power switch tube Q1 is turned off, and the inductor L1 is positive at the bottom and negative at the top, so the voltage sampled by the voltage feedback circuit 633 is a positive value. In addition, it should be noted that Figure 19 What is shown in FIG. 1 is the voltage waveform when the switch control circuit is in critical mode.

[0118] Figure 20 A system structure block diagram of a powered device according to a sixth embodiment of the present invention is shown. Figure 20 The embodiment described above provides an example of a switching power converter with a step-down topology architecture, without a current sampling resistor Rcs, for use in a powered device. Specifically, the powered device 700 includes a rectifier bridge 710, a powered device controller 720, a capacitor Cp, and a switching power converter 730. The rectifier bridge 710 and powered device controller 720 of this embodiment are identical to the rectifier bridge 610 and powered device controller 620 of the fifth embodiment and are not further described here.

[0119] The difference between the switching power converter 730 of this embodiment and the switching power converter 630 of the fifth embodiment is that the switching power converter 730 does not have a current sampling resistor Rcs, that is, the second end of the power switch tube Q1 is directly connected to the first end of the inductor L1 and the floating reference ground terminal VS of the switching power controller 731, and the switching power controller 431 does not have a current detection terminal CS.

[0120] Figure 21 Show Figure 20 The structural diagram of the switching power supply controller in FIG. Figure 21 As shown, the switching power supply controller 731 of this embodiment is Figure 19 The difference between the switching power supply controller 631 shown in FIG4 is that the switching power supply controller 731 further includes a current sampling circuit 406, wherein the current sampling circuit 406 is connected to the first end of the power switch Q1 and is configured to obtain a current sampling signal CS representing peak current information of the switching power converter based on the drain-source voltage difference of the power switch Q1, and provide the current sampling signal CS to the switch control circuit 401. Specifically, the current sampling circuit 406 synchronously samples the drain-source voltage difference of the power switch Q1 according to the turn-on and turn-off operations of the power switch Q1 to obtain the current sampling signal CS. In addition, it should be noted that the current sampling circuit 406 of this embodiment is exactly the same as the current sampling circuit 306 in the third embodiment and will not be described in detail here.

[0121] Figure 22 FIG. 8 is a block diagram showing a structure of an Ethernet power supply system according to a seventh embodiment of the present invention. Figure 22 As shown, the Ethernet power supply system 800 includes a power supply device (PSE) 810 and a powered device (PD) 820. The power supply device 810 can be a network device such as a switch, router, firewall, or hub. The powered device 820 can be an Internet Protocol (IP) phone, a wireless LAN access point, a micro base station, or a network camera.

[0122] refer to Figure 22 Both the power supply device 810 and the powered device 820 can be provided with multiple Ethernet interfaces. Each Ethernet interface of the power supply device 810 can be connected to an Ethernet interface of the powered device 820 via an Ethernet twisted pair cable. The power supply device 810 can transmit data signals to the powered device 820 via the Ethernet twisted pair cable, and can also transmit power signals to the powered device 820, thereby providing power to the powered device 820. The powered device 820 can be implemented using the powered devices 200-700 of the above-described embodiments.

[0123] The operating mode of the power supply device 810 can be controlled by a control circuit, such as an MCU controller or a power supply controller. The operating mode of the power supply device 810 includes, for example, normal power supply to the powered device 820, MPS current to the powered device 820, or stopping power supply to the powered device 820.

[0124] For convenience, Figure 22 Some structures in the Ethernet power supply system are omitted. It should be understood that the omitted parts have been described in other parts of the embodiments of the present disclosure or can be inferred by those skilled in the art based on the enlightenment of the present disclosure, and will not be repeated here.

[0125] In summary, the present invention provides a switching power supply controller that samples the DC input voltage through a startup control circuit to obtain a first sampled voltage referenced to a floating ground. This first sampled voltage is then converted into a second sampled voltage referenced to the fixed ground of a preceding controller. This allows the DC input voltage to be compared with a threshold voltage referenced to the fixed ground, enabling the subsequent switching power supply converter to begin operating after the preceding controller's inrush current limiting has ended. This design ensures that the switching power supply converter begins operating only after the preceding controller's inrush current limiting has ended, thus avoiding the problem of the switching power supply converter failing to start normally.

[0126] In addition, in some embodiments of the present invention, the switching power supply converter sets the power switch tube and the switching power supply controller on the high side and the primary winding on the low side, so that the switching power supply controller and the power switch tube both use the floating ground end as the reference ground, thereby reducing the difficulty of the drive design and the cost of the chip.

[0127] In addition, the switching power supply controller of the present invention is also used to delay the setting time before turning on after the second sampling voltage is greater than the threshold voltage, thereby avoiding the problem that the switching power supply converter cannot output the target output voltage due to the need to charge the large capacitor at the DC input voltage, ensuring the normal startup and operation of the switching power supply converter

[0128] Furthermore, in some other embodiments of the present invention, the switching power supply controller and the preceding controller are not grounded. Compared to conventional solutions, this allows output voltage sampling solely through the primary winding, eliminating the need for an auxiliary winding in the circuit. This significantly reduces the production cost and difficulty of the flyback converter. Furthermore, the absence of an auxiliary winding reduces electromagnetic interference within the circuit.

[0129] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0130] While embodiments of the present invention have been described above, these embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, numerous modifications and variations are possible based on the above description. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better utilize the present invention and its modifications. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A switching power supply controller for controlling a power switch in a switching power supply converter, wherein the switching power supply converter is configured to generate a DC output voltage based on a DC input voltage, characterized in that: The switching power supply controller includes: a switch control circuit, generating a switch control signal according to the current sampling signal and the feedback signal of the DC output voltage; A driving circuit receives the switch control signal and generates a switch driving signal to drive the power switch tube to be turned on or off; a startup control circuit, connected between the DC input voltage and a second reference ground, configured to sample the DC input voltage to obtain a first sampling signal based on the second reference ground, convert the first sampling signal into a second sampling signal based on the first reference ground, and generate a valid startup indication signal when the second sampling signal is greater than a set threshold voltage, the first reference ground being different from the second reference ground; and The delay circuit is connected to the start control circuit and is used to delay the output of a valid enable control signal to the switch control circuit for a preset time after receiving a valid start indication signal, so as to control the switch control circuit to be enabled and turned on.

2. The switching power supply controller according to claim 1, wherein: The switching power converter further includes a first capacitor connected between the DC input voltage and the first reference ground. The preset time is set according to the time required for the first capacitor to charge to the platform voltage.

3. The switching power supply controller according to claim 1, wherein: The first sampling signal includes a first sampling voltage, the second sampling signal includes a second sampling voltage, and the startup control circuit includes: An N-order filtering module, connected between the DC input voltage and the second reference ground, for converting the first sampled voltage into a second sampled voltage, where N is an integer greater than or equal to 1; a first voltage dividing module, configured to divide the second sampled voltage to obtain a first voltage dividing signal of the second sampled voltage; and The first comparator has a non-inverting input terminal for receiving the first voltage-divided signal, an inverting input terminal for receiving a first reference voltage representing the threshold voltage, and an output terminal for outputting the start-up indication signal.

4. The switching power supply controller according to claim 1, wherein: The switch control circuit includes: a first sampling and holding module, configured to sample and hold the feedback signal according to the switch control signal to obtain a third sampling voltage; an error amplifier, wherein the non-inverting input terminal is used to receive the second reference voltage, the inverting input terminal is used to receive the third sampling voltage, and the output terminal is used to output an error signal; a second comparator, whose non-phase input terminal is used to receive the current sampling signal, whose inverting input terminal is used to receive the error signal, and whose output terminal is used to output a comparison signal; and The RS trigger has a set terminal for receiving a clock signal, a reset terminal for receiving the comparison signal, and an output terminal for providing the switch control signal.

5. The switching power supply controller according to claim 4, characterized in that: The switch control circuit further includes: A switching frequency control module is configured to generate the clock signal according to the error signal, wherein the switching frequency of the switch driving signal is set by the clock frequency of the clock signal.

6. The switching power supply controller according to claim 1, wherein: The first sampling signal is a first sampling voltage, the second sampling signal is a fourth sampling voltage, and the startup control circuit includes: a second voltage dividing module, configured to divide the first sampling voltage to obtain a second voltage dividing signal; a second sampling and holding module, configured to sample and hold the second voltage-divided signal according to the switch driving signal to obtain the fourth sampling voltage; and The third comparator has a non-inverting input terminal for receiving the fourth sampling voltage, an inverting input terminal for receiving a first reference voltage representing the threshold voltage, and an output terminal for outputting the start indication signal.

7. The switching power supply controller according to claim 1, wherein: Also includes: A power supply circuit is used to provide a power supply voltage to the switch control circuit according to the DC input voltage.

8. The switching power supply controller according to claim 1, wherein: The first reference ground is a fixed ground, and the second reference ground is a floating ground.

9. The switching power supply controller according to any one of claims 1 to 8, characterized in that: The switching power converter further comprises: A current sampling resistor connected to the second end of the power switch tube, the current sampling resistor is used to provide the current sampling signal to the switching power supply controller.

10. The switching power supply controller according to any one of claims 1 to 8, characterized in that: Also includes: The current sampling circuit is connected to the first end of the power switch tube and is used to generate the current sampling signal.

11. A switching power converter, characterized in that: include: Power switch tube; as well as The switching power supply controller according to any one of claims 1 to 10.

12. The switching power converter according to claim 11, wherein: The switching power converter is one of a floating Buck-Boost topology, a floating Buck topology, a Boost topology and a flyback topology.

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