Feedback circuit, switching power supply and PSE

Abstract

A feedback circuit, a switching power supply and a PSE are used for enabling an output voltage of the switching power supply to be within a safe voltage. The feedback circuit comprises a voltage dividing branch, a voltage stabilizing branch and a first diode; a first end of the voltage dividing branch is connected with an output end of the switching power supply, a second end is grounded, and a voltage dividing node of the voltage dividing branch is connected with a control chip of the switching power supply; the first end of the voltage stabilizing branch is connected with the first end of the voltage dividing branch, and the second end is grounded; the anode of the first diode is connected with the voltage stabilizing node of the voltage stabilizing branch, and the cathode of the first diode is connected with the voltage dividing node of the voltage dividing branch. When the voltage output to the control chip is reduced and the output voltage of the switching power supply is increased due to the failure of a device in the voltage dividing branch, the voltage output by the voltage stabilizing node is increased due to the increase of the current flowing through the voltage stabilizing branch, and the first diode is conducted and provides the voltage for the control chip; the control chip is prevented from controlling the output voltage of the switching power supply to rise all the time due to too low received voltage.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and particularly relates to a feedback circuit, a switching power supply, and a PSE. Background Art

[0002] A switching power supply is a power supply that maintains a stable output voltage by controlling the time ratio of conduction and cutoff of a switching device. It is widely used in various electronic devices due to its small size, light weight, and high efficiency, such as data centers, industrial control devices, communication devices, power equipment, instruments, and security monitoring devices.

[0003] In the prior art, a dedicated control chip is usually configured in a switching power supply. The control chip provides a corresponding drive signal for the switching device according to the voltage amplitude output by the switching power supply, and controls the conduction and cutoff of the switching device through the drive signal to adjust the voltage amplitude output by the switching power supply. The control chip obtains the voltage amplitude output by the switching power supply through a dedicated feedback circuit. However, when the devices in the above feedback circuit fail, the control chip cannot obtain the output voltage of the switching power supply or obtains an incorrect value of the output voltage of the switching power supply. The above voltage acquisition situation may cause the voltage amplitude output by the switching power supply to exceed the safe voltage. Summary of the Utility Model

[0004] This application provides a feedback circuit, a switching power supply, and a PSE for keeping the voltage output by the switching power supply within the safe voltage.

[0005] In a first aspect, an embodiment of this application provides a feedback circuit. The feedback circuit can be applied to a switching power supply and is used to feedback the voltage amplitude output by the switching power supply to a control chip inside the switching power supply, so that the control chip can adjust the conduction and cutoff of the internal switching device according to the output voltage amplitude, thereby achieving the effect of voltage stabilization. Among them, the feedback circuit at least includes the following devices: a voltage division branch, a voltage stabilization branch, and a first diode.

[0006] Specifically, the first end of the voltage division branch is used to connect to the output end of the switching power supply, the second end of the voltage division branch is grounded, and the voltage division node of the voltage division branch is used to connect to the control chip of the switching power supply; the first end of the voltage stabilization branch is connected to the first end of the voltage division branch, and the second end of the voltage stabilization branch is grounded; the anode of the first diode is connected to the voltage stabilization node of the voltage stabilization branch, and the cathode of the first diode is connected to the voltage division node of the voltage division branch.

[0007] With the above design, since the feedback circuit mainly includes a voltage division branch and a voltage stabilization branch, if the devices in the feedback circuit are all normal and free of faults, the potential of the voltage stabilization node in the voltage stabilization branch is less than the potential of the voltage division node in the voltage division branch, and the first diode is in the cut-off state. Therefore, the voltage division of the voltage divider devices in the voltage division branch provides a feedback voltage for the control chip in the switching power supply. When a fault occurs in the devices in the voltage division branch, resulting in a decrease in the voltage amplitude of the voltage division node, the conduction condition of the first diode is satisfied, and the first diode conducts and generates the voltage fed back to the control chip, thereby preventing the control chip from controlling the output voltage of the switching power supply from rising above the safe voltage, and further protecting the safety of the load connected to the switching power supply.

[0008] In a possible design, the voltage division branch includes a plurality of resistors connected in series between the output terminal of the switching power supply and the ground, and the voltage stabilization node is the connection point of any two adjacent resistors among the plurality of resistors. With the above design, the control chip cannot directly process the large voltage output by the switching power supply. In order to reduce the control cost of the control chip, the multiple voltages in the voltage division branch can be connected in series for voltage division, and the large voltage output by the switch is converted into a small voltage and then output to the control chip for processing.

[0009] In a possible design, the voltage division branch includes a first resistor and a second resistor. The first end of the first resistor is used to connect to the output terminal of the switching power supply, and the second end of the first resistor is connected to the first end of the second resistor and the cathode of the first diode; the first end of the second resistor is used to connect to the control chip of the switching power supply, and the second end of the second resistor is grounded.

[0010] In a possible design, the voltage division branch further includes a coupler. The second end of the first resistor is connected to the first end of the second resistor through the first end of the coupler, and the voltage division branch is connected to the control chip of the switching power supply through the second end of the coupler. With the above design, electrical isolation between the output terminal of the switching power supply and the control chip can be achieved through the coupler, which is beneficial to protecting the safety of the control chip.

[0011] In a possible design, the voltage stabilization branch includes: a third resistor and a plurality of voltage regulators, the third resistor and the plurality of voltage regulators are connected in series between the output terminal of the switching power supply and the ground, and the voltage stabilization node is the connection point of any two adjacent voltage regulators among the plurality of voltage regulators.

[0012] With the above design, since the voltage regulation function of the voltage regulator can provide a fixed voltage for the regulated voltage node, when the voltage division branch is normal and fault-free, the voltage of the regulated voltage node is lower than the voltage of the voltage division node of the voltage division branch, and the first diode connecting the regulated voltage node and the voltage division node is cut off. When the voltage of the voltage division node decreases due to a fault in the voltage division branch, the first diode conducts and raises the voltage output to the control chip, thus preventing the control chip from raising the output voltage of the switching power supply above the safe voltage due to receiving a low voltage. Since the output voltage of the switching power supply is within the safe voltage, it is also beneficial to protect the safety of the load connected to the switching power supply.

[0013] In a possible design, the voltage regulation branch includes: the third resistor, the first zener diode, and the second zener diode.

[0014] Wherein, the first end of the third resistor is used to connect to the output end of the switching power supply, the second end of the third resistor is connected to the cathode of the first zener diode; the anode of the first zener diode is connected to the cathode of the second zener diode; the cathode of the second zener diode is connected to the anode of the first diode, and the anode of the second zener diode is grounded.

[0015] In a possible design, the voltage regulation branch includes a third resistor, a first voltage regulator chip, and a second voltage regulator chip.

[0016] Wherein, the first end of the third resistor is used to connect to the output end of the switching power supply, the second end of the third resistor is connected to the first end of the first voltage regulator chip; the second end of the first voltage regulator chip is connected to the first end of the second voltage regulator chip; the first end of the second voltage regulator chip is connected to the anode of the first diode, and the second end of the second voltage regulator chip is grounded.

[0017] In a second aspect, an embodiment of the present application provides a switching power supply, which includes: a conversion circuit, a control chip, and a feedback circuit provided in the first aspect and any of its possible designs of the present application.

[0018] Wherein, the input end of the conversion circuit is used to connect to a power supply, and the output end of the conversion circuit is used to connect to a load; the control chip is respectively connected to the feedback circuit and the conversion circuit, and is used to control the voltage amplitude output by the conversion circuit according to the voltage amplitude output by the feedback circuit.

[0019] In a third aspect, an embodiment of the present application provides a PSE, which includes: a conversion circuit, a control chip, and a feedback circuit provided in the first aspect of the present application and any of its possible designs. Wherein, the input end of the conversion circuit is used to connect to a power supply, and the output end of the conversion circuit is used to connect to a PD; the control chip is respectively connected to the feedback circuit and the conversion circuit, and is used to control the voltage amplitude output by the conversion circuit according to the voltage amplitude output by the feedback circuit.

[0020] In addition, for the technical effects brought by the second to third aspects and any of their possible designs, reference may be made to the technical effects brought by different designs in the first aspect of the embodiments of the present application, which will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for description in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 Structural schematic of a switching power supply provided by an embodiment of the present application Figure 1 ;

[0023] Figure 2 Structural schematic diagram of a feedback circuit provided by an embodiment of the present application;

[0024] Figure 3 Structural schematic diagram of a voltage division branch provided by Embodiment 1 of the present application;

[0025] Figure 4 Structural schematic diagram of a voltage stabilizing branch provided by Embodiment 1 of the present application;

[0026] Figure 5 Structural schematic of a switching power supply provided by Embodiment 2 of the present application Figure 2 。 DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The terms used in the embodiments part of the present application are only for explaining the specific embodiments of the present application, and are not intended to limit the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts belong to the scope of protection of the present application.

[0028] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of this application are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of this application described here can be implemented in an order other than those illustrated or described here. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. On the contrary, they are only examples of devices and methods consistent with some aspects of this application as detailed in the appended claims.

[0029] The following explains some terms in the embodiments of this application to facilitate the understanding of those skilled in the art.

[0030] (1) In the embodiments of this application, the term "plurality" means two or more, and other quantifiers are similar.

[0031] (2) The switching device in the embodiments of this application can be one or more of various types of switching tubes such as metal oxide semiconductor field effect transistor (MOSFET), insulated gate bipolar transistor (IGBT), silicon carbide (SiC) transistor, silicon controlled rectifier (SCR), etc. This application will not list them one by one in the embodiments.

[0032] (3) In the embodiments of this application, "connection" can be understood as electrical connection or communication connection. The electrical connection of two electrical components can be a direct or indirect connection between the two electrical components. For example, when A is connected to B, it can be either a direct connection between A and B or an indirect connection between A and B through one or more other electrical components. For example, when A is connected to B, it can also be a direct connection between A and C and a direct connection between C and B, and the connection between A and B is achieved through C. The communication connection of two electrical components connected is a wireless connection between the two electrical components, that is, an electromagnetic connection between the two electrical components.

[0033] Next, the application scenarios of the technical solutions in the embodiments of this application will be introduced in combination with the drawings in the embodiments of this application. The solution provided by the embodiments of this application can be applied to a power supply system configured with a switching power supply. Generally, a switching device and a control chip or controller for controlling the working state of the above-mentioned switching device are provided inside the switching power supply. The control chip can adjust the conduction duration of the switching device according to the output voltage of the power supply connected to the switching power supply and the voltage output by the switching power supply to the backend load, so as to achieve the effect of stable power supply.

[0034] The feedback circuit provided by the embodiment of the present application can be applied to a switching power supply, such as Figure 1 shown. A switching power supply may include a conversion circuit, a control chip, and the feedback circuit provided by the embodiment of the present application. One end of the feedback circuit can be connected to the output end of the conversion circuit, and the output end of the conversion circuit is also the output end of the switching power supply for connecting to a load. The other end of the feedback circuit can be connected to the control chip and provide a voltage signal representing the output voltage condition of the switching power supply to the control chip.

[0035] such as Figure 2 shown, which is a schematic structural diagram of the feedback circuit provided by the embodiment of the present application. Refer to Figure 2 shown. The feedback circuit at least includes a voltage division branch, a voltage stabilization branch, and a first diode D1.

[0036] Among them, the first end of the voltage division branch is used to be connected to the output end of the switching power supply, the second end of the voltage division branch is grounded, and the voltage division node (not shown) of the voltage division branch is used to be connected to the control chip of the switching power supply; the first end of the voltage stabilization branch is connected to the first end of the voltage division branch, and the second end of the voltage stabilization branch is grounded; the anode of the first diode D1 is connected to the voltage stabilization node (not shown) of the voltage stabilization branch, and the cathode of the first diode D1 is connected to the voltage division node of the voltage division branch.

[0037] Refer to Figure 2 shown. The first ends of both the voltage division branch and the voltage stabilization branch are connected to the output end of the switching power supply, and the second ends of both the voltage division branch and the voltage stabilization branch are grounded, that is, the voltage division branch and the voltage stabilization branch are in parallel, and the connection between internal devices is realized through the first diode D1.

[0038] In actual application, the feedback circuit can be a device independent of other devices in the switching power supply, that is, the connections between the feedback circuit, the control chip, and the conversion circuit can be set in a flexible and detachable form. For example, fixed interfaces are provided on the feedback circuit, and the control chip and the conversion circuit can be connected to the feedback circuit through connection lines and the above interfaces. The feedback circuit can also be fixed on the switching power supply. For example, the feedback circuit can be encapsulated with other devices in the switching power supply as an integrated device, and the present application does not make any limitations in this regard.

[0039] Adopt Figure 2When the shown feedback circuit provides a voltage signal characterizing the output voltage of the switching power supply for the control chip, the voltage dividing branch and the voltage stabilizing branch can receive the output voltage of the switching power supply through the first end. The voltage dividing branch can proportionally convert the received voltage according to the impedance of the internal voltage dividing device and output it through the voltage dividing node. The voltage stabilizing device with voltage stabilizing function in the voltage stabilizing branch will provide a fixed voltage through the voltage stabilizing node. If all the voltage dividing devices in the voltage dividing branch work normally, the voltage amplitude output by the voltage stabilizing node is less than the voltage amplitude at the voltage dividing node in the voltage dividing branch. Therefore, the first diode D1 is in a cut-off state, and the voltage signal received by the control chip is provided by the voltage stabilizing node of the voltage dividing branch.

[0040] Continue to refer to Figure 2 As shown, when a voltage dividing device in the voltage dividing branch fails, for example, the voltage dividing device between the voltage dividing node and the output terminal of the switching power supply is open-circuited, the voltage signal received by the control chip will decrease or even drop to zero. After this voltage is output to the control chip, the control chip believes that the output voltage of the switching power supply has decreased and cannot meet the power supply requirements of the load connected at the back end. Therefore, it controls the conduction time of the switching device in the conversion circuit to increase the output voltage amplitude of the switching power supply, which may lead to the situation that the output voltage of the switching power supply exceeds the safety voltage. In the feedback circuit of this application, a voltage stabilizing branch and the first diode D1 connected between the voltage stabilizing branch and the voltage dividing branch are added. When the voltage dividing device between the voltage dividing node and the output terminal of the switching power supply is open-circuited, although the voltage signal received by the control chip will decrease, resulting in an increase in the output voltage amplitude of the switching power supply, during the increase of the output voltage of the switching power supply, the voltage amplitude of the voltage stabilizing node will increase due to the increase in the current received by the voltage stabilizing device. When the difference between the voltage amplitude provided by the voltage stabilizing node and the conduction voltage drop of the first diode D1 is the voltage for maintaining the voltage output set by the control chip, the output voltage of the switching power supply will be maintained at a fixed value. Therefore, with the above design, although the failure of the voltage dividing device in the voltage dividing branch will control the output voltage of the switching power supply to rise, the adjustment of the output voltage of the switching power supply takes a certain amount of time. Before the output voltage of the switching power supply is adjusted to the safety voltage, the voltage stabilizing node works and adjusts the output voltage of the switching power supply within the safety voltage. Since the output voltage of the switching power supply is within the safety voltage, it is also beneficial to protect the safety of the load connected to the back end of the switching power supply.

[0041] In actual use, according to the device types and the number of devices in the voltage dividing branch and the voltage stabilizing branch, the feedback circuit in this application can have different circuit topologies. Below, in combination with embodiments, the structure of the feedback circuit will be described in detail.

[0042] I. Voltage Dividing Branch

[0043] The first end of the voltage dividing branch is connected to the output end of the switching power supply, and the second end of the voltage dividing branch is grounded. The voltage dividing branch may include multiple resistors connected in series between the output end of the switching power supply and the ground. The voltage stabilizing node is the connection point of any two adjacent resistors among the multiple resistors. This voltage dividing node can be connected to the control chip and provide a voltage signal representing the output voltage condition of the switching power supply for it.

[0044] Among them, the function of setting multiple resistors in the voltage dividing branch is as follows: The multiple resistors are connected in series between the output end of the switching power supply and the ground wire. The output voltage of the switching power supply will be proportionally divided onto the corresponding resistors according to the resistance values of the multiple resistors connected in series. Thus, a voltage signal smaller than the output voltage of the switching power supply is output at the voltage dividing node. The control chip can determine the actual output voltage amplitude of the switching power supply based on the above small voltage, thereby reducing the control cost of the control chip.

[0045] It should be noted that using a resistor as the voltage dividing component in the voltage dividing branch is just an example. In actual applications, other devices with the above voltage dividing function in the industry can also be used in the voltage dividing branch, and specific limitations are not made here in this application.

[0046] In an example, the voltage dividing branch includes a first resistor and a second resistor. The first end of the first resistor is used to be connected to the output end of the switching power supply, and the second end of the first resistor is connected to the first end of the second resistor and the cathode of the first diode D1; the first end of the second resistor is used to be connected to the control chip of the switching power supply, and the second end of the second resistor is grounded.

[0047] For ease of understanding, a specific example of the voltage dividing branch is given below.

[0048] See Figure 3 As shown, it is a schematic structural diagram of a voltage dividing branch provided by an embodiment of the present application. In Figure 3 it, the resistor R1 can be regarded as the first resistor, and the resistor R2 can be regarded as the second resistor. The first end of the resistor R1 is the first end of the voltage dividing branch and is connected to the output end of the switching power supply, and the second end of the resistor R2 is the second end of the voltage dividing branch and is grounded.

[0049] When the voltage dividing branch shown in Figure 3 provides a voltage signal representing the output voltage condition of the switching power supply for the control chip, the first end of the resistor R1 is used as the input end, the second end of the resistor R1 is used as the output end, and the energy flows from top to bottom. The output voltage of the switching power supply on the upper side is proportionally reduced and then output to the control chip.

[0050] It should be noted that the resistance values of resistor R1 and resistor R2 can be configured according to the output voltage range of the control chip and the switching power supply. For example, when the switching power supply is normally powered and its output voltage amplitude is 54V, resistor R1 can be a resistor with a resistance value of 53KΩ, and resistor R2 can be a resistor with a resistance value of 1KΩ. When the switching power supply outputs a normal supply voltage of 54V, the voltage V provided by the voltage dividing node is V=(54*1) / (53 + 1)=1V. Of course, other resistor values can also be selected in this application, and this application does not make excessive limitations here.

[0051] In one example, since the voltage signal provided by the voltage dividing node in the voltage dividing branch is an analog signal and the control chip cannot directly process the analog signal, an analog-to-digital converter may be integrated inside the control chip or an analog-to-digital converter may be configured between the control chip and the voltage dividing branch. This analog-to-digital converter can convert the analog voltage signal provided by the voltage dividing node into a digital signal that can be processed by the control chip.

[0052] In some embodiments, if the control chip is set at the input end of the switching power supply and the voltage at the output end of the switching power supply is obtained for the feedback circuit, in order to achieve signal isolation between the input end and the output end of the switching power supply, in addition to the above-mentioned devices in the voltage dividing branch, a coupler for signal isolation is also included. The second end of the first resistor is connected to the first end of the second resistor through the first end of the coupler, and the voltage dividing branch is connected to the control chip of the switching power supply through the second end of the coupler. Among them, the isolator can be an opto-isolator, and of course, other isolators with signal isolation functions in the industry can also be selected. This application does not make specific limitations here.

[0053] Of course, the above introduction to the structure of the voltage dividing branch is only an example. In actual applications, the voltage dividing branch can also adopt other structures. For example, the voltage dividing branch can also adopt two or more resistors or configure other signal isolation devices.

[0054] II. Voltage Stabilization Branch

[0055] The first end of the voltage stabilization branch is connected to the output end of the switching power supply, and the second end of the voltage stabilization branch is grounded. The voltage stabilization branch includes: a third resistor and multiple voltage stabilizers. The third resistor and the multiple voltage stabilizers are connected in series between the output end of the switching power supply and the ground, and the voltage stabilization node is the connection point between any two adjacent voltage stabilizers among the multiple voltage stabilizers.

[0056] Among them, the function of setting multiple voltage regulators in the voltage stabilization branch is as follows: when the output voltage of the switching power supply remains unchanged, the multiple voltage regulators configured to work can provide a relatively fixed voltage value for the voltage stabilization node, and this voltage value is not affected by the components inside the voltage division branch. Therefore, when a component failure inside the voltage division branch causes the voltage of the voltage division node to drop, the first diode D1 conducts, and the voltage stabilization node can clamp the voltage of the voltage division node to prevent the control chip from receiving an incorrect voltage and raising the output voltage of the switching power supply above the safe voltage.

[0057] In some embodiments, the voltage regulator in the voltage stabilization branch is a zener diode. For example, the voltage stabilization branch includes: a third resistor, a first zener diode, and a second zener diode.

[0058] Among them, the first end of the third resistor is used to connect to the output end of the switching power supply, the second end of the third resistor is connected to the cathode of the first zener diode; the anode of the first zener diode is connected to the cathode of the second zener diode; the cathode of the second zener diode is connected to the anode of the first diode, and the anode of the second zener diode is grounded.

[0059] In some embodiments, the voltage regulator in the voltage stabilization branch is a voltage regulator chip. For example, the voltage stabilization branch includes: a third resistor, a first voltage regulator chip, and a second voltage regulator chip.

[0060] Among them, the first end of the third resistor is used to connect to the output end of the switching power supply, the second end of the third resistor is connected to the first end of the first voltage regulator chip; the second end of the first voltage regulator chip is connected to the first end of the second voltage regulator chip; the first end of the second voltage regulator chip is connected to the anode of the first diode, and the second end of the second voltage regulator chip is grounded.

[0061] For the convenience of understanding, the following takes the voltage regulator in the voltage stabilization branch as a zener diode as an example to give a specific example of the voltage stabilization branch.

[0062] See Figure 4 shown, which is a schematic structural diagram of a voltage stabilization branch provided by an embodiment of the present application. In Figure 4 it, the zener diode Z1 can be regarded as the first zener diode, the zener diode Z2 can be regarded as the second zener diode, and the resistor R3 can be regarded as the third resistor. The cathode of the zener diode Z1 can be regarded as the first end of the voltage stabilization branch connected to the output end of the switching power supply, and the anode of the zener diode Z2 can be regarded as the second end of the voltage stabilization branch grounded.

[0063] When Figure 4 the shown voltage stabilization branch provides a voltage signal representing the output voltage condition of the switching power supply for the control chip, the cathode of the zener diode Z1 is used as the input end, the anode of the zener diode Z1 is used as the output end, and the energy flows from top to bottom, and the output voltage of the switching power supply on the upper side is reduced in proportion and then output to the control chip.

[0064] It should be noted that the models of the first voltage stabilizing diode Z1, the second voltage stabilizing diode Z2, and the third resistor R3 can be configured according to the model of the control chip and the output voltage range of the switching power supply. For example, a device with a regulated voltage value of 56V can be selected for the first voltage stabilizing diode Z1, a device with a regulated voltage value of 3V can be selected for the second voltage stabilizing diode Z2, and a resistor with a resistance value of 100Ω can be selected for the resistor R3.

[0065] In one example, since the voltage signal provided by the voltage stabilizing node in the voltage stabilizing branch is an analog signal, the control chip may not be able to directly process the analog signal. Therefore, an analog-to-digital converter may be integrated inside the control chip, or an analog-to-digital converter may be configured between the control chip and the feedback circuit. This analog-to-digital converter can convert the voltage signal provided by the voltage dividing node into a digital signal that can be processed by the control chip.

[0066] In some embodiments, if the control chip is set at the input end of the switching power supply, in order to achieve signal isolation between the input end and the output end of the switching power supply, an isolator for signal isolation can also be configured. Among them, the voltage dividing branch and the voltage stabilizing branch can share one isolator. In order to enable the voltage dividing branch and the voltage stabilizing branch to work independently of each other, each of the voltage dividing branch and the voltage stabilizing branch is configured with an isolator, and specific limitations are not made here in this application.

[0067] Of course, the above introduction to the structure of the voltage stabilizing branch is only an example. In actual applications, the voltage stabilizing branch can also adopt other structures. For example, the voltage stabilizing branch can also adopt two or more voltage regulators or other devices with voltage stabilizing functions in the industry.

[0068] The above is the feedback circuit structure provided by the embodiments of this application. Next, in combination with Figure 4 the shown feedback circuit structure and device models, taking the switching power supply as a Power Sourcing Equipment (PSE) as an example, when the PSE is normally powered, the output voltage VCC = 54V. Since the PSE belongs to a type of electrical energy source ES1, the output voltage of the PSE cannot exceed the safety voltage of 60V under normal operation, abnormal operation, and single fault conditions. Next, the voltages output in several device states of the feedback circuit will be described respectively in combination with the working parameters of the above devices.

[0069] See Figure 4As shown, when all the devices in the feedback circuit are working properly, the voltage V1 output at the voltage division node in the feedback circuit is V1 = (54 * 1) / (53 + 1) = 1V. The current amplitude flowing through the voltage regulator device in the voltage stabilization branch is small, and the voltage V(z2) output at the voltage stabilization node is 0.9V. At this time, the voltage VF(D1) between the anode and the cathode of the first diode D1 is -0.1V, and the first diode D1 does not meet the conduction condition and is cut off. When the control chip receives the above 1V for maintaining the output voltage, it will control the switching device to turn on and off the switching tube according to the original duty cycle, and the output voltage VCC of the switching power supply will be maintained at 54Vdc during normal power supply.

[0070] If the first resistor R1 in the feedback circuit is open, the voltage received by the control chip drops or even drops to 0V, and the first diode D1 conducts. The control chip will increase the conduction time of the switching tube because the received voltage amplitude is less than 1V, and the output voltage of the switching power supply will increase accordingly. When the output voltage of the switching power supply increases to 57.6V, the reverse current flowing through the first voltage regulator diode Z1 is about 1mA, and the current flowing through the second voltage regulator diode Z2 is about 0.05mA. Then the voltage V(z1) across the first voltage regulator diode Z1 is 56.3V, the voltage V(z2) across the second voltage regulator diode Z2 is 1.2V, the voltage V(R3) across the third resistor R3 is approximately 0.1V, and the conduction voltage drop of the first diode D1 is 0.2V. Therefore, the voltage output by the feedback circuit to the control chip is 1V for maintaining the output voltage, and the output voltage of the switching power supply is VCC = 57.6V < 60V. At this time, although the voltage output by the switching power supply is higher than the voltage of 54V during normal power supply, it is less than the safety voltage of 60V, which can ensure the safety of the load connected at the back end.

[0071] If the second resistor R2 in the feedback circuit is open, the first diode D1 will be in a reverse breakdown state, providing a voltage of about 11.6V for the control chip. When the control chip receives the above voltage, it will think that the output voltage is too high, and the control chip will reduce the conduction time of the switching tube. The output voltage of the switching power supply will decrease accordingly until the voltage of the switching power supply drops from the required 54V during normal power supply to 12.9V. Then, when the voltage output by the feedback circuit to the control chip drops to 1V due to the decrease in the output voltage of the switching power supply, the output voltage of the switching power supply is maintained at 12.9V, which is less than the safety voltage.

[0072] If the first diode D1 is open or short-circuited, since the first resistor R1 and the second resistor R2 are both working properly, a voltage of 1V for maintaining the output voltage amplitude can be provided for the control chip, and the output voltage of the switching power supply still remains at VCC = 54V required for normal power supply.

[0073] If the second voltage stabilizing diode Z2 is open or short - circuited, since the first resistor R1 and the second resistor R2 are both operating normally, 1V can be provided for the control chip to maintain the output voltage amplitude, and the output voltage of the switching power supply still maintains VCC = 54V required for normal power supply.

[0074] If the first voltage stabilizing diode Z1 is short - circuited, the first voltage stabilizing diode is in a low - resistance state, then the current flowing through the second voltage stabilizing diode Z2 increases, and the voltage V(z2) across the second voltage stabilizing diode Z2 is 3.88V, whose value is greater than 1V obtained by resistor voltage division. At this time, the first diode D1 conducts, and the voltage output to the control chip is 3.68V > 1V. Therefore, the control chip will reduce the conduction duration of the switching tube, and the output voltage of the switching power supply will drop to VCC = 12.5V < 60V, meeting the safety requirements of ES1.

[0075] If the first voltage stabilizing diode Z1 is open or the third resistor R3 in series with the first voltage stabilizing diode Z1 is open, then there is no current in the second voltage stabilizing diode Z1. Therefore, the voltage provided by the voltage - stabilizing node is 0V, the first diode D1 is cut off, and the voltage provided by the normal voltage division of the first resistor R1 and the second resistor R2 for the control chip is V=(54 * 1) / (53 + 1)=1V. After receiving the above - mentioned 1V for maintaining the output, the control switch device controls the switching tube to conduct and turn off according to the original duty cycle, and the output voltage VCC of the switching power supply is maintained at 54Vdc during normal power supply.

[0076] The above is the output situation of the switching power supply under different states of the devices in the feedback circuit when the switching power supply is a PSE of a type of electrical energy source. Of course, the switching power supply can also be other devices. According to the specific application scenario of the switching power supply, devices with different parameters can be selected for the feedback circuit, which will not be introduced one by one here in this application.

[0077] Combined with the above description, the embodiment of this application also provides a switching power supply, which can be applied to a power supply system. The switching power supply may include a conversion circuit, a control chip, and the aforementioned feedback circuit.

[0078] Among them, the input end of the conversion circuit is used to connect to the power supply, and the output end of the conversion circuit is used to connect to the load; the control chip is respectively connected to the feedback circuit and the conversion circuit, and is used to control the voltage amplitude output by the conversion circuit according to the voltage amplitude output by the feedback circuit.

[0079] See Figure 5 As shown, it is a schematic structural diagram of a switching power supply for converting 12V voltage to 54V. Among them, the switching resistor R1 and the resistor R2 constitute the voltage - dividing branch in the feedback circuit, the voltage - stabilizing diode D1, the voltage - stabilizing diode D2, and the resistor R4 constitute the voltage - stabilizing branch, and the diode D3 constitutes the first diode.

[0080] It should be noted that Figure 5 The conversion circuit structure composed of a switching tube and a storage inductor shown is only one topology of the switching power supply. In actual application, according to the voltage amplitude and type of the power supply connected to the switching power supply, the structure of the conversion circuit is configured. When the positive and negative directions of the voltage received by the conversion circuit and the voltage output by the conversion circuit are the same, for example, both the voltage received by the conversion circuit and the output voltage are direct current, the conversion circuit can adopt a boost circuit with a boost function or a buck circuit with a buck function. When the types of the voltage received by the conversion circuit and the output voltage are different, for example, if the voltage received by the conversion circuit is alternating current and the voltage output by the conversion circuit is direct current, the conversion circuit can be composed of a power factor correction (PFC) circuit composed of a storage inductor and four switching tubes. When the PFC circuit realizes the rectification function, it is also beneficial to improve the efficiency of the conversion circuit. Of course, the conversion circuit can also adopt other topologies with the above functions in the industry, which are not introduced one by one here in this application.

[0081] In actual application, other devices can also be included in the switching power supply. For example, in addition to the above devices, the switching power supply can also include protection devices, and the protection devices can be overload protection devices and short-circuit protection devices.

[0082] Combined with the above description, an embodiment of the present application also provides a PSE, which at least includes a conversion circuit, a control chip, and the aforementioned feedback circuit.

[0083] Among them, the input end of the conversion circuit is used to connect to the power supply, and the output end of the conversion circuit is used to connect to the PD; the control chip is respectively connected to the feedback circuit and the conversion circuit, and is used to control the voltage amplitude output by the conversion circuit according to the voltage amplitude output by the feedback circuit.

[0084] In each embodiment of the present application, if there is no special description and logical conflict, the terms and / or descriptions between different embodiments are consistent and can be referenced to each other, and the technical features in different embodiments can be combined to form new embodiments according to their internal logical relationships.

[0085] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the protection scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these changes and modifications.

Claims

1. A feedback circuit, characterized in that: Applied to a switching power supply, the feedback circuit comprises: a voltage dividing branch, a voltage stabilizing branch and a first diode; The first end of the voltage dividing branch is used to be connected to the output end of the switching power supply, the second end of the voltage dividing branch is grounded, and the voltage dividing node of the voltage dividing branch is used to be connected to the control chip of the switching power supply; The first end of the voltage stabilizing branch is connected to the first end of the voltage dividing branch, and the second end of the voltage stabilizing branch is grounded; An anode of the first diode is connected to a voltage stabilization node of the voltage stabilization branch, and a cathode of the first diode is connected to a voltage dividing node of the voltage dividing branch.

2. The circuit according to claim 1, characterized in that The voltage dividing branch includes a plurality of resistors connected in series between the output end of the switching power supply and the ground, and the voltage stabilization node is a connection point of any two adjacent resistors among the plurality of resistors.

3. The circuit according to claim 2, characterized in that The voltage dividing branch comprises: a first resistor and a second resistor; The first end of the first resistor is used to be connected to the output end of the switching power supply, and the second end of the first resistor is connected to the first end of the second resistor and the cathode of the first diode; The first end of the second resistor is used to be connected to the control chip of the switching power supply, and the second end of the second resistor is grounded.

4. The circuit according to claim 3, characterized in that The voltage dividing branch also includes a coupler, the second end of the first resistor is connected to the first end of the second resistor through the first end of the coupler, and the voltage dividing branch is connected to the control chip of the switching power supply through the second end of the coupler.

5. The circuit according to claim 1 or 2, characterized in that: The voltage stabilization branch includes: a third resistor and a plurality of voltage stabilizers, the third resistor and the plurality of voltage stabilizers are connected in series between the output end of the switching power supply and the ground, and the voltage stabilization node is a connection point between any two adjacent voltage stabilizers among the plurality of voltage stabilizers.

6. The circuit according to claim 5, characterized in that The voltage stabilizing branch includes: the third resistor, the first voltage stabilizing diode and the second voltage stabilizing diode; The first end of the third resistor is used to be connected to the output end of the switching power supply, and the second end of the third resistor is connected to the cathode of the first voltage stabilizing diode; The anode of the first voltage zener diode is connected to the cathode of the second voltage zener diode; A cathode of the second voltage stabilizing diode is connected to an anode of the first diode, and an anode of the second voltage stabilizing diode is grounded.

7. The circuit according to claim 5, characterized in that The voltage stabilizing branch includes: a third resistor, a first voltage stabilizing chip and a second voltage stabilizing chip; The first end of the third resistor is used to be connected to the output end of the switching power supply, and the second end of the third resistor is connected to the first end of the first voltage stabilizing chip; The second end of the first voltage stabilizing chip is connected to the first end of the second voltage stabilizing chip; A first end of the second voltage stabilizing chip is connected to the anode of the first diode, and a second end of the second voltage stabilizing chip is grounded.

8. A switching power supply, characterized in that: include: A conversion circuit, a control chip and a feedback circuit as claimed in any one of claims 1 to 7; The input end of the conversion circuit is used to be connected to a power supply, and the output end of the conversion circuit is used to be connected to a load; The control chip is connected to the feedback circuit and the conversion circuit respectively, and is used to control the voltage amplitude output by the conversion circuit according to the voltage amplitude output by the feedback circuit.

9. A PSE, characterized in that: include: A conversion circuit, a control chip and a feedback circuit as claimed in any one of claims 1 to 7; The input end of the conversion circuit is used to connect to the power supply, and the output end of the conversion circuit is used to connect to the PD; The control chip is connected to the feedback circuit and the conversion circuit respectively, and is used to control the voltage amplitude output by the conversion circuit according to the voltage amplitude output by the feedback circuit.

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