Over-voltage and over-temperature protection circuit for PD equipment

Abstract

The utility model relates to the technical field of electronic circuits, and provides an overvoltage and over-temperature protection circuit for PD equipment, which comprises a PD power receiving circuit, an input protection module and an output protection module, and is characterized in that the PD power receiving circuit comprises an over-temperature protection module; the input end of the input protection module is connected with the power supply input end, and the output end is connected with the input end of the PD power receiving circuit; the input end of the output protection module is connected with the output end of the PD power receiving circuit, and the output end of the output protection module is connected with electric equipment. According to the utility model, the input protection module and the output protection module are respectively arranged at the input end and the output end of the PD power receiving circuit, the over-temperature protection module is additionally arranged in the PD power receiving circuit, perfect over-voltage and over-temperature protection measures are set up, and the circuit is controlled by pure hardware, so that software is not required to be involved in judgment and processing during working, and the working efficiency is greatly improved. And the response speed and sensitivity of overvoltage and over-temperature protection are effectively improved.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, in particular to an overvoltage and overtemperature protection circuit for PD equipment. Background Art

[0002] The IEEE802.3af specification, which we usually call it, allows devices that provide power to use a 36-57V DC voltage (usually 48V) to provide a 10-400mA current selectable maximum power of 15.40W through two available pairs of wires in the four pairs of Ethernet twisted pair cables. The cable type can be Category 3, Category 5 or Category 5e. This standard defines two types of equipment: PoE Power Sourcing Equipment (PSE) and PoE Powered Devices (PD). Power is provided to the powered device by the sourcing equipment. PoE is a technology that transmits power to remote devices while transmitting data on standard Ethernet twisted pair cables.

[0003] In order to optimize room communication routing and simplify product layout, more and more electronic products are beginning to use PD device (PoE powered device) circuit design solutions to match terminals, including cameras, routers, switches, etc. The PD device circuits currently on the market lack complete overvoltage and overtemperature protection measures.

[0004] On the one hand, when the input voltage of the PD input is too high, or the floating ground of the PD output is accidentally connected to the ground and the voltage drop increases to 48V, it will cause the terminal of the powered device to overvoltage and break down, and the aluminum electrolytic capacitor on the board may also be at risk of explosion.

[0005] On the other hand, the current application scenarios of PD equipment are mainly used for power supply of small electronic products such as cameras and APs. In addition, the integrated power switch module inside the PD chip generates a lot of heat, which poses a risk of over-temperature, which will seriously affect the safety of users' lives and property. Therefore, an over-voltage and over-temperature protection measure is needed to solve this problem. Summary of the invention

[0006] The utility model provides an overvoltage and overtemperature protection circuit for PD equipment, which solves the technical problem that the existing PD equipment circuit lacks perfect overvoltage and overtemperature protection measures.

[0007] In order to solve the above technical problems, the utility model provides an overvoltage and overtemperature protection circuit for a PD device, including a PD power receiving circuit, and also including an input protection module and an output protection module; the input end of the input protection module is connected to the power input end, and the output end is connected to the input end of the PD power receiving circuit; the input end of the output protection module is connected to the output end of the PD power receiving circuit, and the output end is connected to an electrical device; the PD power receiving circuit includes an overtemperature protection module, and the overtemperature protection module is connected to the input end of the output protection module.

[0008] In a further embodiment, the output protection module includes a first switch tube Q1, a second switch tube Q2, a voltage stabilizing diode D1, resistors R1 to R4, and a capacitor C1;

[0009] The first end of the first switch tube Q1 is connected to the control end of the second switch tube Q2, the second end is connected to the output end of the over-temperature protection module and the first end of the second switch tube Q2, and the control end is connected to the output end of the over-temperature protection module through the resistor R1 and the resistor R2; the positive electrode of the voltage regulator diode D1 is grounded, and the negative electrode is connected between the resistor R1 and the resistor R2;

[0010] The two ends of the resistor R3 are respectively connected to the first end and the control end of the second switch tube Q2;

[0011] One end of the resistor R4 is connected to the control end of the second switch tube Q2, and the other end is grounded;

[0012] One end of the capacitor C1 is connected to the second end of the second switch tube Q2, and the other end is grounded.

[0013] In a further embodiment, the utility model further comprises a mechanical switch K1, wherein the mechanical switch K1 is connected in series between the resistor R4 and the ground terminal GND.

[0014] In a further embodiment, the utility model also includes a display component, which includes a resistor R5 and an LED lamp D2, one end of the resistor R5 is connected to the output end of the output protection module, and the other end is connected to the positive pole of the LED lamp D2; the negative pole of the LED lamp D2 is grounded.

[0015] In a further implementation scheme, the input protection module includes a resettable fuse F1, a TVS tube D3 and a capacitor C2, one end of the resettable fuse F1 is connected to the power input end, and the other end is connected to the PD power receiving circuit; the negative electrode of the TVS tube D3 is connected to the other end of the resettable fuse F1, and the other end is grounded; the capacitor C1 is connected in parallel with the TVS tube D3.

[0016] In a further embodiment, the over-temperature protection module includes a diode D4, an inductor L1, a capacitor C3, a capacitor C4 and a temperature control switch K2;

[0017] The PD power receiving circuit also includes a main control chip;

[0018] The cathode of the diode D4 is connected between the output end of the input protection module and the input end of the output protection module, and the anode is connected to the switch pin of the main control chip through the temperature control switch K2; one end of the inductor L1 is connected between the anode of the diode D4 and the temperature control switch K2, and the other end is connected to one end of the capacitor C3; the other end of the capacitor is connected between the cathode of the diode D4 and the input end of the output protection module;

[0019] The capacitor C4 is connected in parallel with the capacitor C3.

[0020] In a further implementation scheme, the PD power receiving circuit also includes an output feedback module, which includes a resistor R6, a resistor R7 and a capacitor C5; one end of the resistor R6 is connected to the input end of the input protection module, and the other end is connected to the feedback pin of the main control chip; one end of the resistor R7 is connected to the other end of the resistor R6, and the other end is grounded; the capacitor C5 is connected in parallel with the resistor R7.

[0021] In a further embodiment, the first switch tube Q1 is a triode or a MOS tube; the second switch tube Q2 is a triode or a MOS tube.

[0022] The beneficial effects of the utility model are as follows:

[0023] (1) An input protection module and an output protection module are respectively set at the input and output ends of the PD power receiving circuit. At the same time, an over-temperature protection module is added to the PD power receiving circuit to build a complete over-voltage and over-temperature protection measure. The circuit is purely hardware controlled and does not require software intervention for judgment and processing during operation, which effectively improves the response speed and sensitivity of over-voltage and over-temperature protection.

[0024] (2) A TVS tube is set to detect the voltage difference at the input end. When the voltage is too large and the voltage difference is higher than the conduction voltage of the TVS tube, the state of the TVS tube is switched from cut-off to conduction, thereby causing a short circuit between VDD and VSS to protect the back-end circuit. At the same time, a self-recovery fuse is added. When the line is short-circuited, the current increases and the fuse fails and opens, thereby achieving overvoltage protection and protecting the TVS tube.

[0025] (3) A normally closed temperature control switch is connected in series between the BUCK step-down circuit (diode D4, inductor L1, capacitor C3, capacitor C4) of the PD power receiving circuit and the main control chip. Since the normally closed temperature control switch is placed in the place where the heat generation is the largest in the entire circuit, when the temperature is higher than the threshold, the state of the temperature control switch switches from closed to open, causing the inductor to be disconnected and the PD power receiving circuit to stop outputting voltage. The temperature control switch is used to realize the high-temperature mechanical automatic cut-off of the circuit, which has a simple structure and sensitive response.

[0026] (4) An output protection module composed of a triode and a switch tube is provided, and a two-stage switch tube is provided to control the on-off of the circuit. When an overvoltage condition occurs at the output end, the first switch tube Q1 is turned on and the second switch tube Q2 is turned off, so that the input and output cannot form a loop and the power supply to the output end is disconnected, thereby playing the role of overvoltage protection at the output end. The circuit has low cost, simple structure and strong operability.

[0027] (5) Setting up an output display with an LED light provides a reminder function to remind the user of abnormal power supply of the product, and then cooperating with the mechanical switch for active control to completely disconnect the PD circuit from the back-end powered device to fully protect the back-end device and avoid potential safety hazards to the user. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a system framework diagram of an overvoltage and overtemperature protection circuit for a PD device provided by an embodiment of the utility model;

[0029] Figure 2 The utility model embodiment provides Figure 1 The hardware circuit diagram of the output detection module;

[0030] Figure 3 The utility model embodiment provides Figure 1 Hardware circuit diagram of some modules in the middle;

[0031] Among them: input protection module 1, output protection module 2, PD power receiving circuit 3, main control chip U1, over-temperature protection module 4, output feedback module 5; input detection module 6. DETAILED DESCRIPTION

[0032] The following is a detailed explanation of the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limitations on the present invention. The accompanying drawings are provided for reference and illustration only and do not constitute limitations on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0033] The utility model provides an overvoltage and overtemperature protection circuit for a PD device, such as Figure 1 to Figure 3As shown, in this embodiment, it includes a PD power receiving circuit 3, an input protection module 1 and an output protection module 2; the input end of the input protection module 1 is connected to the power input end, and the output end is connected to the input end of the PD power receiving circuit 3; the input end of the output protection module 2 is connected to the output end of the PD power receiving circuit 3, and the output end is connected to the power-consuming device; the PD power receiving circuit 3 includes an over-temperature protection module 4, and the over-temperature protection module 4 is connected to the input end of the output protection module 2.

[0034] The PD power receiving circuit 3 is a conventional PD power receiving circuit 3, which includes a main control chip U1, an input detection module 6, an output feedback module 5 and a BUCK step-down circuit; the main control chip U1 is preferably a PD chip.

[0035] In this embodiment, the input protection module 1 includes a resettable fuse F1, a TVS tube D3 and a capacitor C2. One end of the resettable fuse F1 is connected to the power input end, and the other end is connected to the PD power receiving circuit 3 (i.e., the VPOS pin of the main control chip U1); the negative electrode of the TVS tube D3 is connected to the other end of the resettable fuse F1, and the other end is grounded; the capacitor C1 is connected in parallel with the TVS tube D3.

[0036] Among them, capacitor C1 mainly plays the role of voltage buffering and filtering. The input overvoltage protection principle is as follows:

[0037] The input voltage of the power input terminal is the voltage difference between VDD and VSS. When the voltage difference is higher than the threshold, the TVS tube D3 reaches the conduction voltage, and the state of the TVS tube D3 is switched from cut-off to conduction, thereby short-circuiting VDD and VSS to protect the back-end circuit. Since the current increases when the line is short-circuited, the TVS tube D3 will be damaged if it is turned on for a long time in this state, so a self-recovery fuse F1 is added. Before the TVS tube D3 is damaged, F1 will fail and open the circuit due to the increase in current when the line is short-circuited, thereby playing the role of overvoltage protection and protecting the TVS tube D3. When the abnormal overvoltage situation is restored, the self-recovery fuse F1 and the TVS tube D3 will return to normal state, and the input circuit of the PD power receiving circuit 3 will return to normal working state.

[0038] In this embodiment, the over-temperature protection module 4 includes a diode D4, an inductor L1, a capacitor C3, a capacitor C4 and a temperature control switch K2;

[0039] The cathode of diode D4 is connected between the output end of input protection module 1 and the input end of output protection module 2, and the anode is connected to the switch pin of main control chip U1 through temperature control switch K2; one end of inductor L1 is connected between the anode of diode D4 and temperature control switch K2, and the other end is connected to one end of capacitor C3; the other end of the capacitor is connected between the cathode of diode D4 and the input end of output protection module 2;

[0040] Capacitor C4 is connected in parallel with capacitor C3.

[0041] Among them, if the temperature control switch K2 is normally closed, the over-temperature protection principle is as follows:

[0042] The diode D4, the inductor L1, the capacitor C3 and the capacitor C4 form a BUCK step-down circuit, and the step-down condition is controlled by the switch tube inside the SWO pin of the main control chip U1.

[0043] When the temperature is higher than the threshold, the state of the temperature control switch K2 switches from closed to open, causing the inductor L1 to be disconnected and the main control chip U1 (i.e., PD device) to stop outputting voltage. When the temperature returns to the threshold, the temperature control switch K2 closes again and the circuit returns to normal working state.

[0044] In this embodiment, the output feedback module 5 includes a resistor R6, a resistor R7 and a capacitor C5; one end of the resistor R6 is connected to the input end of the input protection module 1, and the other end is connected to the feedback pin FBH of the main control chip U1; one end of the resistor R7 is connected to the other end of the resistor R6, and the other end is grounded; the capacitor C5 is connected in parallel with the resistor R7.

[0045] The input detection module 6 includes a voltage detection component and a current detection component. The voltage detection component includes a resistor R8, one end of which is connected to the output end of the over-temperature protection module 4; the current detection component includes a resistor R9, one end of which is connected to the HSO pin (providing voltage) and the ISNS pin (current detection) of the main control chip U1, and the other end is grounded.

[0046] In this embodiment, the output protection module 2 includes a first switch tube Q1, a second switch tube Q2, a voltage regulator diode D1, resistors R1 to R4, and a capacitor C1;

[0047] The first end of the first switch tube Q1 is connected to the control end of the second switch tube Q2, the second end is connected to the output end of the over-temperature protection module 4 and the first end of the second switch tube Q2, and the control end is connected to the output end of the over-temperature protection module 4 through the resistor R1 and the resistor R2; the positive electrode of the voltage stabilizing diode D1 is grounded, and the negative electrode is connected between the resistor R1 and the resistor R2;

[0048] The two ends of the resistor R3 are respectively connected to the first end and the control end of the second switch tube Q2;

[0049] One end of the resistor R4 is connected to the control end of the second switch tube Q2, and the other end is grounded;

[0050] One end of the capacitor C1 is connected to the second end of the second switch tube Q2 , and the other end is grounded.

[0051] Among them, capacitor C1 mainly plays the role of voltage buffering and filtering.

[0052] In this embodiment, the utility model further includes a mechanical switch K1 , which is connected in series between the resistor R4 and the ground terminal GND.

[0053] In this embodiment, the utility model also includes a display component, which includes a resistor R5 and an LED lamp D2. One end of the resistor R5 is connected to the output end of the output protection module 2, and the other end is connected to the positive pole of the LED lamp D2; the negative pole of the LED lamp D2 is grounded.

[0054] In this embodiment, the first switch tube Q1 is a triode or a MOS tube; the second switch tube Q2 is a triode or a MOS tube. Preferably, taking the first switch tube Q1 as a PNP type triode as an example, its first end, second end, and control end are respectively the collector, emitter, and base; taking the second switch tube Q2 as a P channel MOS tube as an example, its first end, second end, and control end are respectively the source, drain, and gate.

[0055] Among them, the mechanical switch K1 is a normally closed type. Taking the first switch tube Q1 as a PNP transistor and the second switch tube Q2 as a P-channel MOS tube as an example, the output end overvoltage protection principle is as follows:

[0056] When an overvoltage occurs at the output end, that is, the voltage difference between VOUT and GND is greater than the requirement of the back-end electrical equipment (PoE cameras, APs, etc.), the voltage across the voltage zener diode D1 will automatically stabilize to be equal to VOUT. At this time, there is a voltage difference across the resistor R1, so that there is also a voltage difference between the e-pole and the b-pole of the first switch tube Q1 and it is turned on. After the first switch tube Q1 is turned on, the G-pole of the second switch tube Q2 is connected to the S-pole of the second switch tube Q2 through the first switch tube Q1, resulting in no voltage difference in Vgs of the second switch tube Q2, which is in a cut-off state, making it impossible for the input and output to form a loop to disconnect the power supply of the output end, thereby playing the role of overvoltage protection at the output end. At this time, the LED light D2 goes out to remind the user that the power supply of the product is abnormal.

[0057] When the overvoltage abnormality is relieved, the Zener diode D1 is pulled up to the normal voltage through the resistor R1, and the Zener diode D1 does not meet the conduction requirement and is in the cut-off state. The b-pole of the first switch tube Q1 is connected to the e-pole of the first switch tube Q1 through the resistors R1 and R2, that is, the first switch tube Q1 is in the cut-off state. At this time, the G-pole of the second switch tube Q2 is smaller than the S-pole voltage due to the voltage-dividing function of the resistors R3 and R4 and the normally closed state of the mechanical switch K1, that is, the second switch tube Q2 will be in the conduction state, so that the input and output form a loop for normal power supply. At this time, the LED lamp D2 is on, indicating that the power supply circuit of the product is normal.

[0058] When the LED light D2 is in an abnormal state such as being off for a long time and not turning on again or continuously flashing, it indicates that there is an abnormality in the circuit. At this time, by disconnecting the mechanical switch K1, the PD power receiving circuit 3 can be completely disconnected from the rear-end power-consuming equipment, so as to fully protect the rear-end power-consuming equipment and avoid potential safety hazards to users.

[0059] The beneficial effects of the embodiments of the utility model are as follows:

[0060] (1) An input protection module 1 and an output protection module 2 are respectively provided at the input end and the output end of the PD power receiving circuit 3. At the same time, an over-temperature protection module 4 is added to the PD power receiving circuit 3 to build a complete over-voltage and over-temperature protection measure. The circuit is purely hardware controlled and does not require software intervention for judgment and processing during operation, which effectively improves the response speed and sensitivity of the over-voltage and over-temperature protection.

[0061] (2) A TVS tube is set to detect the voltage difference at the input end. When the voltage is too large and the voltage difference is higher than the conduction voltage of the TVS tube, the state of the TVS tube is switched from cut-off to conduction, thereby causing a short circuit between VDD and VSS to protect the back-end circuit. At the same time, a self-recovery fuse is added. When the line is short-circuited, the current increases and the fuse fails and opens, thereby achieving overvoltage protection and protecting the TVS tube.

[0062] (3) A normally closed temperature control switch is connected in series between the BUCK step-down circuit (diode D4, inductor L1, capacitor C3, capacitor C4) of the PD power receiving circuit 3 and the main control chip U1. Since the normally closed temperature control switch is placed at the place where the heat generation is the largest in the entire circuit, when the temperature is higher than the threshold, the state of the temperature control switch switches from closed to open, causing the inductor to be disconnected and the PD power receiving circuit 3 to stop outputting voltage. The temperature control switch is used to realize the high-temperature mechanical automatic cut-off of the circuit, which has a simple structure and sensitive response.

[0063] (4) An output protection module 2 composed of a triode and a switch tube is provided, and a bipolar switch tube is provided to control the on-off of the circuit. When an overvoltage condition occurs at the output end, the first switch tube Q1 is turned on and the second switch tube Q2 is turned off, so that the input and output cannot form a loop and the power supply to the output end is disconnected, thereby playing the role of overvoltage protection at the output end. The circuit has low cost, simple structure and strong operability.

[0064] (5) Setting up an output display with an LED light provides a reminder function to remind the user of abnormal power supply of the product, and then cooperating with the mechanical switch for active control to completely disconnect the PD circuit from the back-end powered device to fully protect the back-end device and avoid potential safety hazards to the user.

[0065] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principle of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An overvoltage and overtemperature protection circuit for a PD device, comprising a PD power receiving circuit, characterized in that: It also includes an input protection module and an output protection module; the input end of the input protection module is connected to the power input end, and the output end is connected to the input end of the PD power receiving circuit; the input end of the output protection module is connected to the output end of the PD power receiving circuit, and the output end is connected to the power-consuming device; the PD power receiving circuit includes an over-temperature protection module, and the over-temperature protection module is connected to the input end of the output protection module; The output protection module includes a first switch tube Q1, a second switch tube Q2, a voltage regulator diode D1, resistors R1 to R4 and a capacitor C1; The first end of the first switch tube Q1 is connected to the control end of the second switch tube Q2, the second end is connected to the output end of the over-temperature protection module and the first end of the second switch tube Q2, and the control end is connected to the output end of the over-temperature protection module through the resistor R1 and the resistor R2; the positive electrode of the voltage regulator diode D1 is grounded, and the negative electrode is connected between the resistor R1 and the resistor R2; The two ends of the resistor R3 are respectively connected to the first end and the control end of the second switch tube Q2; One end of the resistor R4 is connected to the control end of the second switch tube Q2, and the other end is grounded; One end of the capacitor C1 is connected to the second end of the second switch tube Q2, and the other end is grounded.

2. An overvoltage and overtemperature protection circuit for a PD device as claimed in claim 1, characterized in that: The mechanical switch K1 is also included, and the mechanical switch K1 is connected in series between the resistor R4 and the ground terminal GND.

3. An overvoltage and overtemperature protection circuit for a PD device as claimed in claim 1, characterized in that: It also includes a display component, which includes a resistor R5 and an LED lamp D2. One end of the resistor R5 is connected to the output end of the output protection module, and the other end is connected to the positive electrode of the LED lamp D2. The negative electrode of the LED lamp D2 is grounded.

4. An overvoltage and overtemperature protection circuit for a PD device as claimed in claim 1, characterized in that: The input protection module includes a resettable fuse F1, a TVS tube D3 and a capacitor C2. One end of the resettable fuse F1 is connected to the power input end, and the other end is connected to the PD power receiving circuit; the negative electrode of the TVS tube D3 is connected to the other end of the resettable fuse F1, and the other end is grounded; the capacitor C1 is connected in parallel with the TVS tube D3.

5. The overvoltage and overtemperature protection circuit for PD equipment according to claim 1, characterized in that: The over-temperature protection module includes a diode D4, an inductor L1, a capacitor C3, a capacitor C4 and a temperature control switch K2; The PD power receiving circuit also includes a main control chip; The cathode of the diode D4 is connected between the output end of the input protection module and the input end of the output protection module, and the anode is connected to the switch pin of the main control chip through the temperature control switch K2; one end of the inductor L1 is connected between the anode of the diode D4 and the temperature control switch K2, and the other end is connected to one end of the capacitor C3; the other end of the capacitor is connected between the cathode of the diode D4 and the input end of the output protection module; The capacitor C4 is connected in parallel with the capacitor C3.

6. An overvoltage and overtemperature protection circuit for a PD device as claimed in claim 5, characterized in that: The PD power receiving circuit also includes an output feedback module, which includes a resistor R6, a resistor R7 and a capacitor C5; one end of the resistor R6 is connected to the input end of the input protection module, and the other end is connected to the feedback pin of the main control chip; one end of the resistor R7 is connected to the other end of the resistor R6, and the other end is grounded; the capacitor C5 is connected in parallel with the resistor R7.

7. An overvoltage and overtemperature protection circuit for a PD device as claimed in claim 1, characterized in that: The first switch tube Q1 is a triode or a MOS tube; the second switch tube Q2 is a triode or a MOS tube.

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