Over-current protection delay recovery system for DC-DC converter

Abstract

The utility model provides an overcurrent protection delay recovery system for a DC-DC converter, and relates to the technical field of power electronic equipment. The overcurrent protection delay recovery system comprises an output current sampling circuit, a sampling amplification circuit, a reference circuit, an overcurrent protection delay recovery circuit, an isolation control circuit and an optical coupler isolation circuit. Under the condition that the amplified sampling signal is greater than the reference voltage, the overcurrent protection delay recovery circuit outputs a high level, the isolation control circuit is switched on, the optical coupler isolation circuit outputs an overcurrent protection signal, and the DC-DC converter executes overcurrent protection; under the condition that the DC-DC converter executes overcurrent protection, the overcurrent protection delay recovery circuit delays for a first time and then outputs a low level, the isolation control circuit is disconnected, the optocoupler isolation circuit does not output the overcurrent protection signal any more, and the DC-DC converter ends overcurrent protection, so that the situation that the DC-DC converter stops overcurrent protection when an overcurrent fault occurs is effectively avoided. And a device is heated or damaged due to frequent action of the overcurrent protection circuit.

Description

Technical Field

[0001] This application relates to the field of power electronic equipment technology, and more specifically, to an overcurrent protection delay recovery system for a DC-DC converter. Background Technology

[0002] A DC-DC converter is a device that transforms a DC input voltage into a DC output voltage of another level. Based on whether there is electrical isolation between the input and output, DC-DC converters can be divided into isolated and non-isolated types. Compared to non-isolated DC-DC converters, the biggest characteristic of isolated DC-DC converters is that electrical isolation between the input and output is achieved through a transformer. In isolated DC-DC converters, there are no conductive parts between the input and output, making them safer and more stable.

[0003] When the output of a DC-DC converter exceeds its rated load, it can damage the converter itself, causing the system to malfunction. Therefore, overcurrent protection design is crucial for the reliable operation of a DC-DC converter. For isolated DC-DC converters, overcurrent protection circuits can be designed on the primary side of the isolation transformer for primary-side overcurrent protection, or on the secondary side for output overcurrent protection. Compared to primary-side overcurrent protection, output overcurrent protection circuits directly sample the output current. When the output current exceeds the overcurrent protection threshold, the overcurrent protection circuit activates, generating an overcurrent protection signal and controlling the DC-DC converter to stop operating. Output overcurrent protection offers the advantage of a more precise protection threshold and is independent of the DC-DC converter's input parameters, simplifying overcurrent protection design.

[0004] However, in practical engineering applications, overcurrent faults often cannot be eliminated in a short time, and simply implementing overcurrent protection cannot fully guarantee the safe and reliable operation of the DC-DC converter. Furthermore, frequent and prolonged operation of overcurrent protection can still cause overheating or damage to the DC-DC converter components. However, in the current DC-DC converter industry, due to cost control and design complexity considerations, the issue of frequent overcurrent protection circuit operation during overcurrent faults, potentially leading to overheating or damage to components, is not considered in most cases. Utility Model Content

[0005] To address at least one of the aforementioned problems, this application proposes an overcurrent protection delay recovery system for DC-DC converters.

[0006] According to a first aspect of this application, at least one embodiment of this application provides an overcurrent protection delay recovery system for a DC-DC converter, comprising: an output current sampling circuit for acquiring the output current of the DC-DC converter and generating a sampling signal; a sampling amplification circuit connected to the output current sampling circuit for amplifying the sampling signal; a reference circuit for generating a reference voltage; an overcurrent protection delay recovery circuit connected to the sampling amplification circuit and the reference circuit respectively, for receiving the amplified sampling signal and the reference voltage, and outputting a high level or a low level according to the magnitude of the amplified sampling signal and the reference voltage; and an isolation control circuit connected to the DC-DC converter. The overcurrent protection delay recovery circuit is connected to receive the high or low level signal; an optocoupler isolation circuit is connected to the isolation control circuit; when the amplified sampled signal is greater than the reference voltage, the overcurrent protection delay recovery circuit outputs a high level, the isolation control circuit is turned on, the optocoupler isolation circuit outputs an overcurrent protection signal, and the DC-DC converter performs overcurrent protection; when the DC-DC converter performs overcurrent protection, the overcurrent protection delay recovery circuit outputs a low level after a first delay, the isolation control circuit is turned off, the optocoupler isolation circuit no longer outputs the overcurrent protection signal, and the DC-DC converter ends overcurrent protection.

[0007] For example, in some embodiments of this application, the output current sampling circuit includes a sampling resistor for acquiring the output current of the DC-DC converter and converting the output current into a voltage sampling signal.

[0008] For example, in some embodiments of this application, the sampling amplification circuit includes: a first comparator; a first resistor, one end of which is connected to the negative input terminal of the first comparator and the other end of which is grounded; a second resistor, one end of which is connected to one end of the sampling resistor and the other end of which is connected to the positive input terminal of the first comparator; a third resistor, one end of which is connected to the negative input terminal of the first comparator and the other end of which is connected to the output terminal of the first comparator; a second comparator; a fourth resistor, one end of which is connected to the output terminal of the first comparator and the other end of which is connected to the negative input terminal of the second comparator; a fifth resistor, one end of which is connected to the other end of the sampling resistor and the other end of which is connected to the positive input terminal of the second comparator; and a sixth resistor, one end of which is connected to the negative input terminal of the second comparator and the other end of which is connected to the output terminal of the second comparator.

[0009] For example, in some embodiments of this application, the reference circuit includes: a seventh resistor, one end of which is connected to the power supply voltage; a first capacitor, one end of which is connected to the power supply voltage and the other end is grounded; and a voltage reference chip, wherein the reference electrode and cathode of the voltage reference chip are short-circuited and connected to the other end of the seventh resistor as the output terminal of the reference circuit, and the anode of the voltage reference chip is grounded.

[0010] For example, in some embodiments of this application, the overcurrent protection delay recovery circuit includes: a third comparator; an eighth resistor, one end of which is connected to the output terminal of the sampling amplification circuit, and the other end of which is connected to the positive input terminal of the third comparator; a ninth resistor, one end of which is connected to the output terminal of the reference circuit, and the other end of which is connected to the negative input terminal of the third comparator; a tenth resistor, one end of which is connected to the positive input terminal of the third comparator, and the other end of which is connected to the output terminal of the third comparator; an eleventh resistor, one end of which is connected to the supply voltage, and the other end of which is connected to the output terminal of the third comparator; and a first diode, the anode of which is connected to the third comparator. The output terminal of the comparator is connected to: a second capacitor, one end of which is connected to the cathode of the first diode, and the other end is grounded; a twelfth resistor, connected in parallel with the second capacitor; a fourth comparator; a thirteenth resistor, one end of which is connected to the cathode of the first diode, and the other end is connected to the positive input terminal of the fourth comparator; a fourteenth resistor, one end of which is connected to the supply voltage, and the other end is connected to the negative input terminal of the fourth comparator; a fifteenth resistor, one end of which is connected to the negative input terminal of the fourth comparator, and the other end is grounded; and a sixteenth resistor, one end of which is connected to the positive input terminal of the fourth comparator, and the other end is connected to the output terminal of the fourth comparator.

[0011] For example, in some embodiments of this application, the first time is calculated according to the following formula:

[0012]

[0013] Among them, t delay For the first time, C2 is the capacitance value of the second capacitor, and R... 12 R is the resistance value of the twelfth resistor. 14 R is the resistance value of the fourteenth resistor. 15 The value of the fifteenth resistor.

[0014] For example, in some embodiments of this application, the resistance value of the tenth resistor is greater than the resistance value of the eighth resistor; the resistance value of the sixteenth resistor is greater than the resistance value of the thirteenth resistor.

[0015] For example, in some embodiments of this application, the isolation control circuit includes: a seventeenth resistor, one end of which is connected to the power supply voltage and the other end of which is connected to the output terminal of the overcurrent protection delay recovery circuit; an eighteenth resistor, one end of which is connected to the output terminal of the overcurrent protection delay recovery circuit and the other end of which is grounded; a nineteenth resistor, one end of which is connected to the power supply voltage and the other end of which is connected to the optocoupler isolation circuit; and a first MOS transistor, the gate of which is connected to the output terminal of the overcurrent protection delay recovery circuit, the drain of which is connected to the optocoupler isolation circuit, and the source of which is grounded.

[0016] For example, in some embodiments of this application, the resistance value of the sixteenth resistor is greater than the resistance value of the seventeenth resistor.

[0017] For example, in some embodiments of this application, the optocoupler isolation circuit includes: an optocoupler, wherein the anode of the light-emitting diode on the primary side of the optocoupler is connected to the other end of the nineteenth resistor, and the cathode is connected to the drain of the first MOS transistor; the emitter of the transistor on the secondary side of the optocoupler is connected to the primary signal ground of the DC-DC converter, and the collector is connected to the control chip of the DC-DC converter to output the overcurrent protection signal.

[0018] Through the above example embodiments, this application provides an overcurrent protection delay recovery system for DC-DC converters. By adding an overcurrent protection delay recovery circuit to the output current overcurrent protection circuit, it effectively avoids the problem of frequent operation of the overcurrent protection circuit during overcurrent faults, which could lead to device overheating or damage. Furthermore, compared to circuit designs using overcurrent protection control chips, this application uses only simple analog devices to construct the output current overcurrent protection delay recovery circuit, effectively controlling costs. The delay time of the overcurrent protection delay recovery circuit is controllable and relatively simple to design, allowing for flexible configuration of the delay time for DC-DC converters with different output power levels.

[0019] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0020] The above and other objects, features, and advantages of this application will become more apparent from the detailed description of exemplary embodiments with reference to the accompanying drawings. The drawings described below are merely some embodiments of this application and are not intended to limit the scope of this application.

[0021] Figure 1 A schematic diagram of an overcurrent protection delay recovery system for a DC-DC converter, illustrating an exemplary embodiment, is shown.

[0022] Figure 2 A circuit diagram of an overcurrent protection delay recovery system for a DC-DC converter is shown as an exemplary embodiment. Detailed Implementation

[0023] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0024] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0025] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0026] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0027] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily essential for implementing this application, and therefore cannot be used to limit the scope of protection of this application.

[0028] In practical engineering applications, the output overcurrent protection circuit directly samples the output current. When the output current exceeds the overcurrent protection threshold, the overcurrent protection circuit activates, generating an overcurrent protection signal to stop the DC-DC converter. However, overcurrent faults often cannot be eliminated in a short time, and simply implementing overcurrent protection cannot fully guarantee the safe and reliable operation of the DC-DC converter. Furthermore, frequent and prolonged activation of the overcurrent protection can still cause overheating or damage to the DC-DC converter components.

[0029] To address the aforementioned issues, this application proposes an overcurrent protection delay recovery system for DC-DC converters. This system aims to resolve the problem of existing output overcurrent protection circuits frequently outputting overcurrent protection signals, causing the DC-DC converter to operate frequently over a long period, resulting in device overheating or damage.

[0030] Figure 1 A schematic diagram of an overcurrent protection delay recovery system for a DC-DC converter is shown as an exemplary embodiment.

[0031] like Figure 1 As shown, the overcurrent protection delay recovery system for a DC-DC converter includes: an output current sampling circuit 101, a sampling amplification circuit 102, a reference circuit 103, an overcurrent protection delay recovery circuit 104, an isolation control circuit 105, and an optocoupler isolation circuit 106.

[0032] The output current sampling circuit 101 is used to acquire the output current of the DC-DC converter 107 and generate a sampling signal. The sampling amplification circuit 102 is connected to the output current sampling circuit 101 and is used to amplify the sampling signal. The reference circuit 103 is used to generate a reference voltage. The overcurrent protection delay recovery circuit 104 is connected to the sampling amplification circuit 102 and the reference circuit 103 respectively, and is used to receive the amplified sampling signal and the reference voltage, and output a high or low level according to the magnitude of the amplified sampling signal and the reference voltage. The isolation control circuit 105 is connected to the overcurrent protection delay recovery circuit 104 and is used to receive a high or low level. The optocoupler isolation circuit 106 is connected to the isolation control circuit 105. The DC-DC converter 107 includes a control chip 1071 and a DC-DC converter unit 1072.

[0033] When the amplified sampled signal is greater than the reference voltage, the overcurrent protection delay recovery circuit 104 outputs a high level, the isolation control circuit 105 is turned on, the optocoupler isolation circuit 106 outputs an overcurrent protection signal, and the DC-DC converter 107 performs overcurrent protection.

[0034] When the DC-DC converter 107 performs overcurrent protection, the overcurrent protection delay recovery circuit 104 outputs a low level after a delay of the first time, causing the isolation control circuit 105 to disconnect, the optocoupler isolation circuit 106 to stop outputting the overcurrent protection signal, and the DC-DC converter 107 ends the overcurrent protection.

[0035] According to some embodiments, the DC-DC converter unit 1072 includes any common DC-DC converter such as a forward converter.

[0036] Figure 2A circuit diagram of an overcurrent protection delay recovery system for a DC-DC converter is shown as an exemplary embodiment.

[0037] like Figure 2 As shown, the output current sampling circuit 101 includes a sampling resistor R. sense Sampling resistor R sense Used to collect the output current I of DC-DC converter 107 out The output current is converted into a voltage sampling signal V. sense The sampling resistor R of the output current sampling circuit 101 sense The high end is connected to the positive input terminal of the first comparator U1 through the second resistor R2, and the sampling resistor R of the output current sampling circuit 101 is connected to the sampling terminal of the first comparator U1. sense The low end is connected to the positive input of the second comparator U2 through the fifth resistor R5.

[0038] The sampling amplifier circuit 102 includes: a first comparator U1, a second comparator U2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6.

[0039] In this circuit, one end of the first resistor R1 is connected to the negative input terminal of the first comparator U1, and the other end is grounded. One end of the second resistor R2 is connected to the sampling resistor R. sense One end of the first resistor R1 is connected to the positive input terminal of the first comparator U1, and the other end is connected to the output terminal of the first comparator U1. One end of the second resistor R4 is connected to the output terminal of the first comparator U1, and the other end is connected to the negative input terminal of the second comparator U2. One end of the third resistor R5 is connected to the sampling resistor R. sense One end of the first comparator U1 is connected to the positive input terminal of the second comparator U2, and the other end is connected to the output terminal of the second comparator U2. The positive and negative power supply terminals of the first comparator U1 and the second comparator U2 are connected to the positive voltage VCC and ground GND, respectively.

[0040] The sampling amplifier circuit 102 realizes the V of the differential mode voltage sampling signal output by the output current sampling circuit 101. sense The proportional calculation will be performed on V. sense The amplification factor can be adjusted to a suitable value to set an appropriate overcurrent protection threshold. This method offers advantages such as convenient resistor selection and adjustment, and high input impedance. The amplification factor can be achieved by changing the resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6.

[0041] The reference circuit 103 includes: a seventh resistor R7, a first capacitor C1, and a voltage reference chip U5.

[0042] In this circuit, one end of the seventh resistor R7 is connected to the power supply voltage. One end of the first capacitor C1 is connected to the power supply voltage, and the other end is grounded. The reference and cathode terminals of the voltage reference chip U5 are shorted and connected to the other end of the seventh resistor R7, serving as the output terminal of the reference circuit 103. The anode of the voltage reference chip U5 is grounded. The reference circuit 103 is used to generate a stable and reliable reference voltage.

[0043] The overcurrent protection delay recovery circuit 104 includes: a third comparator U3, a fourth comparator U4, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a first diode D1, and a second capacitor C2.

[0044] In this circuit, one end of the eighth resistor R8 is connected to the output of the sampling amplifier circuit 102, and the other end is connected to the positive input of the third comparator U3. One end of the ninth resistor R9 is connected to the output of the reference circuit 103, and the other end is connected to the negative input of the third comparator U3. One end of the tenth resistor R10 is connected to the positive input of the third comparator U3, and the other end is connected to the output of the third comparator U3. One end of the eleventh resistor R11 is connected to the power supply voltage, and the other end is connected to the output of the third comparator U3. The anode of the first diode D1 is connected to the output of the third comparator U3. One end of the second capacitor C2 is connected to the cathode of the first diode D1, and the other end is grounded. The twelfth resistor R12 is connected in parallel with the second capacitor C2. One end of the thirteenth resistor R13 is connected to the cathode of the first diode D1, and the other end is connected to the positive input of the fourth comparator U4. One end of the fourteenth resistor R14 is connected to the power supply voltage, and the other end is connected to the negative input of the fourth comparator U4. One end of the fifteenth resistor R15 is connected to the negative input terminal of the fourth comparator U4, and the other end is grounded. One end of the sixteenth resistor R16 is connected to the positive input terminal of the fourth comparator U4, and the other end is connected to the output terminal of the fourth comparator U4. The positive and negative power supply terminals of the third comparator U3 and the fourth comparator U4 are connected to the positive voltage VCC and ground GND, respectively.

[0045] The isolation control circuit 105 includes: a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, and a first MOSFET Q1.

[0046] Among them, one end of the seventeenth resistor R17 is connected to the power supply voltage, and the other end is connected to the output terminal of the overcurrent protection delay recovery circuit 104. One end of the eighteenth resistor R18 is connected to the output terminal of the overcurrent protection delay recovery circuit 104, and the other end is grounded. One end of the nineteenth resistor R19 is connected to the power supply voltage, and the other end is connected to the optocoupler isolation circuit 106. The gate of the first MOSFET Q1 is connected to the output terminal of the overcurrent protection delay recovery circuit 104, the drain is connected to the optocoupler isolation circuit 106, and the source is grounded.

[0047] The optocoupler isolation circuit 106 includes an optocoupler U6.

[0048] The anode of the LED on the primary side of optocoupler U6 is connected to the other end of the nineteenth resistor R19, and the cathode is connected to the drain of the first MOSFET Q1. The emitter of the transistor on the secondary side of optocoupler U6 is connected to the primary side signal ground GNDA of DC-DC converter 107, and the collector is connected to the control chip of DC-DC converter 107. The collector generates a protection signal that can act on the control chip of the primary side of the forward converter, outputting an overcurrent protection signal.

[0049] Sampling amplifier circuit 102 pairs V sense The amplified voltage is compared with the reference voltage at the positive and negative input terminals of the third comparator U3. When the voltage at the positive input terminal of the third comparator U3 is higher than the voltage at the negative input terminal, the output of the third comparator U3 flips to a high level, and the voltage across the second capacitor C2 is pulled up to the positive voltage VCC. At the same time, the voltage at the positive input terminal of the fourth comparator U4 is higher than the voltage at the negative input terminal, and the output of the fourth comparator U4 flips to a high level. After the output of the fourth comparator U4 in the overcurrent protection delay recovery circuit 104 flips to a high level, the positive voltage VCC is divided by resistors R17 and R18 and input to the gate of the first MOSFET Q1, controlling the first MOSFET Q1 to conduct. This, in turn, turns on the primary side of the optocoupler U6, and the overcurrent protection signal on the secondary side of the optocoupler U6 is pulled down to a low level, making the overcurrent protection signal active low.

[0050] When the DC-DC converter 107 stops working due to overcurrent protection, V senseWhen the voltage drops to 0, the voltage at the positive input terminal of the third comparator U3 becomes lower than the voltage at the negative input terminal, causing the output of the third comparator U3 to flip to a low level. The voltage stored in the second capacitor C2 discharges through the twelfth resistor R12. After the first discharge time, the voltage at the positive input terminal of the fourth comparator U4 becomes lower than the voltage at the negative input terminal, causing the output of the fourth comparator U4 to flip to a low level. The discharge time of the second capacitor C2 is the overcurrent protection delay recovery time, i.e., the first time. The overcurrent protection delay recovery time can be adjusted by changing the values ​​of the twelfth resistor R12, the second capacitor C2, the fourteenth resistor R14, and the fifteenth resistor R15. After the output of the fourth comparator U4 in the overcurrent protection delay recovery circuit flips to a low level, the gate voltage of the first MOSFET Q1 disappears, the primary and secondary sides of the optocoupler U6 are not conducting, and the overcurrent protection signal is pulled up to a high level in the primary-side control circuit, rendering the overcurrent protection signal ineffective.

[0051] The calculation method for the overcurrent protection delay recovery time in the overcurrent protection delay recovery system for DC-DC converters is as follows:

[0052] Wherein, the output current of the DC-DC converter is set to I. out After sampling resistor R sense The obtained voltage sampling signal V sense With output current I out The relationship is:

[0053] V sense =I out ×R sense

[0054] The resistance values ​​of the first resistor R1 and the sixth resistor R6 are set to be the same, and the resistance values ​​of the third resistor R3 and the fourth resistor R4 are set to be the same. The output voltage of the sampling amplifier circuit 102 is set to V. amp Then the voltage sampling signal V sense With output voltage V amp The relationship is:

[0055]

[0056] Where R6 is the resistance value of the sixth resistor and R4 is the resistance value of the fourth resistor.

[0057] Taking a reference circuit outputting a 2.5V reference voltage as an example, the output voltage of the sampling amplifier circuit 102 is set to V. amp Rise to V ampH When the third comparator U3 outputs a high level, V ampH The relationship with the reference voltage is as follows:

[0058]

[0059] Where R8 is the resistance value of the eighth resistor and R10 is the resistance value of the tenth resistor.

[0060] According to the example embodiment, if the resistance value of the tenth resistor R10 is set to be much higher than the resistance value of the eighth resistor R8, then the following formula is satisfied:

[0061] R 10 >>R8

[0062]

[0063] V ampH ≈2.5

[0064] The discharge time constant τ of the RC network composed of the second capacitor C2 and the twelfth resistor R12 is:

[0065] τ=C2×R 12

[0066] Where C2 is the capacitance of the first capacitor and R12 is the resistance of the twelfth resistor.

[0067] The voltage V at the negative input terminal of the fourth comparator U4 delay With supply voltage V VCC The relationship is:

[0068]

[0069] Where R14 is the resistance value of the fourteenth resistor and R15 is the resistance value of the fifteenth resistor.

[0070] Set the voltage across the second capacitor C2 to drop to V. delayL Then, the output of the fourth comparator U4 flips to a low level, V delayL With V delay The relationship is:

[0071]

[0072] Where R13 is the resistance value of the thirteenth resistor, R16 is the resistance value of the sixteenth resistor, and R17 is the resistance value of the seventeenth resistor.

[0073] Generally, if the resistance value of the sixteenth resistor R16 is set much higher than that of the thirteenth resistor R13 and the seventeenth resistor R17, then the following formula will be satisfied:

[0074] R 16 >>R 13 &R 17

[0075]

[0076] The overcurrent protection delay recovery time t can be derived from the aforementioned formula.delay The calculation formula is:

[0077]

[0078] This application provides an overcurrent protection delay recovery system, which adds an overcurrent protection delay recovery circuit to the output current overcurrent protection circuit. This effectively avoids the problem of frequent operation of the overcurrent protection circuit during overcurrent faults, which could lead to device overheating or damage. Compared with circuit designs using overcurrent protection control chips, this application uses only simple analog devices to construct the output current overcurrent protection delay recovery circuit, effectively controlling costs. Furthermore, the delay time of the overcurrent protection delay recovery circuit is controllable and the design is relatively simple, allowing for flexible configuration of the delay time for DC-DC converters with different output power levels.

[0079] It should be clearly understood that this application describes how specific examples are formed and used, but this application is not limited to any details of these examples. Rather, based on the teachings of the disclosure of this application, these principles can be applied to many other embodiments.

[0080] Furthermore, it should be noted that the above figures are merely illustrative representations of the processes included in the method according to exemplary embodiments of this application, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0081] Exemplary embodiments of this application have been specifically shown and described above. It should be understood that this application is not limited to the detailed structures, arrangements, or implementation methods described herein; rather, this application is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. An overcurrent protection delay recovery system for a DC-DC converter, characterized in that, include: The output current sampling circuit is used to acquire the output current of the DC-DC converter and generate a sampling signal; A sampling amplification circuit, connected to the output current sampling circuit, is used to amplify the sampled signal; A reference circuit is used to generate a reference voltage. An overcurrent protection delay recovery circuit is connected to the sampling amplification circuit and the reference circuit respectively, and is used to receive the amplified sampling signal and the reference voltage, and output a high level or a low level according to the magnitude of the amplified sampling signal and the reference voltage; An isolation control circuit, connected to the overcurrent protection delay recovery circuit, is used to receive the high or low level. An optocoupler isolation circuit is connected to the isolation control circuit; When the amplified sampled signal is greater than the reference voltage, the overcurrent protection delay recovery circuit outputs a high level, the isolation control circuit is turned on, the optocoupler isolation circuit outputs an overcurrent protection signal, and the DC-DC converter performs overcurrent protection. When the DC-DC converter performs overcurrent protection, the overcurrent protection delay recovery circuit outputs a low level after a first delay, the isolation control circuit is disconnected, the optocoupler isolation circuit no longer outputs the overcurrent protection signal, and the DC-DC converter ends overcurrent protection.

2. The overcurrent protection delay recovery system as described in claim 1, characterized in that, The output current sampling circuit includes: The sampling resistor is used to acquire the output current of the DC-DC converter and convert the output current into a voltage sampling signal.

3. The overcurrent protection delay recovery system as described in claim 2, characterized in that, The sampling amplification circuit includes: First comparator; The first resistor has one end connected to the negative input terminal of the first comparator and the other end grounded. The second resistor has one end connected to one end of the sampling resistor and the other end connected to the positive input terminal of the first comparator. The third resistor has one end connected to the negative input terminal of the first comparator and the other end connected to the output terminal of the first comparator. Second comparator; The fourth resistor has one end connected to the output terminal of the first comparator and the other end connected to the negative input terminal of the second comparator. The fifth resistor has one end connected to the other end of the sampling resistor and the other end connected to the positive input terminal of the second comparator. The sixth resistor has one end connected to the negative input terminal of the second comparator and the other end connected to the output terminal of the second comparator.

4. The overcurrent protection delay recovery system as described in claim 1, characterized in that, The reference circuit includes: The seventh resistor has one end connected to the power supply voltage; The first capacitor has one end connected to the power supply voltage and the other end grounded. A voltage reference chip, wherein the reference electrode and the cathode of the voltage reference chip are shorted and connected to the other end of the seventh resistor, serving as the output terminal of the reference circuit, and the anode of the voltage reference chip is grounded.

5. The overcurrent protection delay recovery system as described in claim 1, characterized in that, The overcurrent protection delay recovery circuit includes: Third comparator; The eighth resistor has one end connected to the output terminal of the sampling amplifier circuit and the other end connected to the positive input terminal of the third comparator. The ninth resistor has one end connected to the output terminal of the reference circuit and the other end connected to the negative input terminal of the third comparator. The tenth resistor has one end connected to the positive input terminal of the third comparator and the other end connected to the output terminal of the third comparator. The eleventh resistor has one end connected to the power supply voltage and the other end connected to the output terminal of the third comparator. The anode of the first diode is connected to the output terminal of the third comparator. The second capacitor has one end connected to the cathode of the first diode and the other end grounded. The twelfth resistor is connected in parallel with the second capacitor; Fourth comparator; The thirteenth resistor has one end connected to the cathode of the first diode and the other end connected to the positive input terminal of the fourth comparator. The fourteenth resistor has one end connected to the power supply voltage and the other end connected to the negative input terminal of the fourth comparator. The fifteenth resistor has one end connected to the negative input terminal of the fourth comparator and the other end grounded. The sixteenth resistor has one end connected to the positive input terminal of the fourth comparator and the other end connected to the output terminal of the fourth comparator.

6. The overcurrent protection delay recovery system as described in claim 5, characterized in that, The first time is calculated according to the following formula: Among them, t delay For the first time, C2 is the capacitance value of the second capacitor, and R... 12 The resistance value of the twelfth resistor. R 14 The resistance value of the fourteenth resistor. R 15 The value of the fifteenth resistor.

7. The overcurrent protection delay recovery system as described in claim 5, characterized in that, The resistance value of the tenth resistor is greater than the resistance value of the eighth resistor; The resistance value of the sixteenth resistor is greater than the resistance value of the thirteenth resistor.

8. The overcurrent protection delay recovery system as described in claim 5, characterized in that, The isolation control circuit includes: The seventeenth resistor has one end connected to the power supply voltage and the other end connected to the output terminal of the overcurrent protection delay recovery circuit; The eighteenth resistor has one end connected to the output terminal of the overcurrent protection delay recovery circuit, and the other end grounded. The nineteenth resistor has one end connected to the power supply voltage and the other end connected to the optocoupler isolation circuit. The first MOSFET has its gate connected to the output of the overcurrent protection delay recovery circuit, its drain connected to the optocoupler isolation circuit, and its source grounded.

9. The overcurrent protection delay recovery system as described in claim 8, characterized in that, The resistance value of the sixteenth resistor is greater than the resistance value of the seventeenth resistor.

10. The overcurrent protection delay recovery system as described in claim 8, characterized in that, The optocoupler isolation circuit includes: The optocoupler has its primary side LED anode connected to the other end of the nineteenth resistor and its cathode connected to the drain of the first MOS transistor; the secondary side transistor's emitter is connected to the primary side signal ground of the DC-DC converter, and its collector is connected to the control chip of the DC-DC converter to output the overcurrent protection signal.

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