Low-power-consumption short-circuit protection circuit for DC / DC converter

Abstract

The utility model belongs to the technical field of electronic circuits, and particularly relates to a low-power-consumption short-circuit protection circuit for a DC / DC converter, which comprises a DC / DC output power loop of the DC / DC converter, an operational amplifier U3, an operational amplifier U1, a current detection unit, a first voltage stabilizing circuit, a second voltage stabilizing circuit, an input signal adjusting unit and a protection signal output circuit. The DC / DC output power loop is connected with the positive / negative input end of the operational amplifier U3 through the current detection unit, and the positive / negative input end of the operational amplifier U3 is connected with the first voltage stabilizing circuit through the current detection unit; the reverse input end of the operational amplifier U1 is connected with the DC / DC output power loop through the input signal adjusting unit, and the positive input end of the operational amplifier U1 is connected with the second voltage stabilizing circuit. And the output ends of the operational amplifier U1 and the operational amplifier U3 are respectively connected with a protection signal output circuit. And after the short circuit is detected, repeated restarting is avoided, a short circuit fault mode can be entered for a long time, unnecessary energy consumption is avoided, and thus the short circuit power consumption is reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of electronic circuit, especially relate to a low -power consumption short circuit protection circuit for DC DC converter. BACKGROUND

[0002] DC-DC converter is a kind of DC power supply conversion device, which plays a vital role in many fields.

[0003] It is necessary to protect DC / DC converter from short circuit. Firstly, from the safety of equipment, short circuit can make the output current of DC / DC converter become very large instantaneously, and the excessive current can generate excessive heat in the internal power device. Without protection, these devices may be damaged due to overheating, and even explode, resulting in the entire converter being scrapped. Secondly, from the system stability, DC / DC converter is usually part of an electronic system, and the abnormally large current caused by short circuit may interfere with other parts of the system where the converter is located, such as causing fluctuations in system voltage, thereby affecting the normal operation of other circuit elements connected to it, which may cause the entire electronic system to malfunction.

[0004] Traditional DC / DC converter short circuit protection is mostly hiccup short circuit protection, that is, when the circuit is running normally, the current and voltage are within the preset range. When short circuit occurs, the current will increase sharply instantaneously. The detection element (such as current transformer, sampling resistor, etc.) in the circuit will monitor this change and transmit the signal to the control circuit. After receiving the signal, the control circuit will immediately cut off the power output, which is the first protection action. Then, the control circuit will start a timer. After the time interval set by the timer, the control circuit will try to restart the power output, because the short circuit may be caused by instantaneous interference. If the short circuit still exists, the detection element will detect the abnormality again, and the control circuit will cut off the output again, so the cycle is like hiccup, until the short circuit fault is eliminated, and the circuit can resume normal continuous power supply.

[0005] The defects of hiccup short circuit protection are:

[0006] 1) After short circuit occurs, it is restarted repeatedly, and each restart consumes a certain amount of energy, resulting in large short circuit power consumption;

[0007] 2) Due to repeated restart, the product may be damaged by over-power in long-term short circuit condition;

[0008] 3) Repeated restart may cause system instability and affect normal operation of the equipment. INVENTION CONTENTS

[0009] The utility model discloses a purpose at in order to overcome the insufficient of prior art, propose a kind of low-power short-circuit protection circuit for DC / DC converter, can long time enter short-circuit fault mode, until fault mode eliminates.

[0010] The above object is achieved by the following technical solutions:

[0011] A kind of low-power short-circuit protection circuit for DC / DC converter, including the DC / DC output power loop of DC / DC converter, still including operational amplifier U3, operational amplifier U1, current detection unit, first voltage stabilizing circuit, second voltage stabilizing circuit, input signal adjusting unit and protection signal output circuit.The current detection unit includes power resistor R1, voltage dividing resistor R7, voltage dividing resistor R8, voltage dividing resistor R9 and voltage dividing resistor R10;Power resistor R1 is connected in series in DC / DC output power loop.The input signal adjusting unit includes voltage dividing resistor R5 and voltage dividing resistor R4.The positive input end of operational amplifier U3 is connected to the input end of power resistor R1 by voltage dividing resistor R7, is connected first voltage stabilizing circuit by voltage dividing resistor R9;The output end of operational amplifier U3 is connected protection signal output circuit;The positive power supply end of operational amplifier U3 is connected power supply Vcc.The positive input end of operational amplifier U1 is connected second voltage stabilizing circuit;The output end of operational amplifier U1 is connected protection signal output circuit, while being connected power supply Vcc by resistance R2;The positive power supply end of operational amplifier U1 is connected power supply Vcc.

[0012] Preferably, the first voltage stabilizing circuit includes voltage stabilizing tube U4 and current limiting resistor R11;The positive pole of voltage stabilizing tube U4 is grounded;The negative pole of voltage stabilizing tube U4 is connected power supply Vcc by current limiting resistor R11;Voltage dividing resistor R9 and voltage dividing resistor R10 are connected the negative pole of voltage stabilizing tube U4.

[0013] Preferably, the second voltage stabilizing circuit includes three-terminal voltage regulator U2 and current limiting resistor R6;The negative pole and reference end of three-terminal voltage regulator U2 are connected power supply Vcc by current limiting resistor R6, the positive pole of three-terminal voltage regulator U2 is grounded, and the positive input end of operational amplifier U1 is connected the negative pole of three-terminal voltage regulator U2.

[0014] Preferably, it further includes first feedback circuit, and the first feedback circuit includes resistance R12 and capacitor C1;The output end of operational amplifier U3 is connected the reverse input end of operational amplifier U3 by capacitor C1 and resistance R12.

[0015] Preferably, the second feedback circuit is further included, and the second feedback circuit comprises a resistor R3 and a capacitor C2; the output end of the operational amplifier U1 is connected to the reverse input end of the operational amplifier U1 through the capacitor C2 and the resistor R3.

[0016] Preferably, the first filter circuit is further included, and the first filter circuit comprises a filter capacitor C4; the reverse input end of the operational amplifier U3 is grounded through the filter capacitor C4.

[0017] Preferably, the second filter circuit is further included, and the second filter circuit comprises a filter capacitor C3; the forward input end of the operational amplifier U1 is grounded through the filter capacitor C3.

[0018] Preferably, the protection signal output circuit comprises a diode D2 and a signal output port Vcomp; the anode of the diode D2 is connected to the output end of the operational amplifier U1, and the cathode of the diode D2 is connected to the output end of the operational amplifier U3; the signal output port Vcomp is connected to the anode of the diode D2.

[0019] Compared with the prior art, the technical scheme has the advantages that:

[0020] 1) Lower power consumption

[0021] The low-power short-circuit protection circuit proposed in the technical scheme will not restart repeatedly after detecting a short circuit, and can enter a short-circuit fault mode for a long time, thereby avoiding unnecessary energy consumption and reducing short-circuit power consumption. For example, in some application scenarios with strict power consumption requirements, such as portable electronic devices, the low-power short-circuit protection circuit proposed in the technical scheme can prolong the battery life of the device and improve the reliability and stability of the device.

[0022] 2) Reduce the risk of product over-power damage

[0023] The low-power short-circuit protection circuit proposed in the technical scheme is in a fault mode when a short-circuit fault has not been eliminated, and will not cause repeated power impact on the product, thereby reducing the risk of product over-power damage. For example, in some industrial control devices, once a product is damaged due to a short circuit, it may cause the entire production system to shut down, resulting in huge economic losses. The low-power short-circuit protection circuit proposed in the technical scheme can effectively protect the device and reduce the risk of device damage and production interruption caused by a short circuit.

[0024] 3) Higher stability

[0025] The low-power short-circuit protection circuit provided in the technical scheme can stably enter a fault mode after a short-circuit fault occurs, and will not cause frequent interference to the system, thereby improving the stability of the system. For example, in some communication equipment with high requirements for system stability, the low-power short-circuit protection circuit can ensure that the equipment can still maintain a stable working state during a short-circuit fault, thereby improving the reliability of communication. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a connection structure diagram of the low-power short-circuit protection circuit. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme of the embodiments of the utility model will be described clearly and completely in combination with the drawings of the embodiments of the utility model below, which should not be understood as limiting the utility model to the following examples. The utility model in the field of deformation and improvement should be included in the protection scope of the utility model claims without departing from the concept of the utility model.

[0028] Unless otherwise defined, technical terms or scientific terms used in the present disclosure should be understood as the usual meaning understood by a person with ordinary skills in the art to which the present disclosure belongs. The similar words such as "or", "including" and the like used in the present disclosure mean that the elements or objects appearing before the words cover the elements or objects listed after the words and their equivalents, and other elements or objects are not excluded.

[0029] Embodiment 1

[0030] The embodiment discloses a low-power short-circuit protection circuit for a DC / DC converter (hereinafter referred to as "low-power short-circuit protection circuit"), which comprises a DC / DC output power loop of the DC / DC converter. As a preferred embodiment of the embodiment, the low-power short-circuit protection circuit further comprises an operational amplifier U3, an operational amplifier U1, a current detection unit, a first voltage stabilizing circuit, a second voltage stabilizing circuit, an input signal adjusting unit and a protection signal output circuit.

[0031] The current detection unit comprises a power resistor R1, a voltage dividing resistor R7, a voltage dividing resistor R8, a voltage dividing resistor R9 and a voltage dividing resistor R10. The power resistor R1 is connected in series in the DC / DC output power loop.

[0032] The input signal adjusting unit comprises a voltage dividing resistor R5 and a voltage dividing resistor R4.

[0033] The positive input end of the operational amplifier U3 is connected to the input end of the power resistor R1 through the voltage dividing resistor R7 and connected to the first voltage stabilizing circuit through the voltage dividing resistor R9; the negative input end of the operational amplifier U3 is connected to the output end of the power resistor R1 through the voltage dividing resistor R8 and connected to the voltage stabilizing circuit through the voltage dividing resistor R10; the output end of the operational amplifier U3 is connected to the protection signal output circuit; and the positive power supply end of the operational amplifier U3 is connected to the power supply Vcc.

[0034] The operational amplifier U1 is used for error amplification of the sampling signal, the positive input end of the operational amplifier U1 is connected to the second voltage stabilizing circuit; the negative input end of the operational amplifier U1 is connected to the output end of the power resistor R1 through the voltage dividing resistor R5 and grounded through the voltage dividing resistor R4; the output end of the operational amplifier U1 is connected to the protection signal output circuit and connected to the power supply Vcc through the resistor R2; and the positive power supply end of the operational amplifier U1 is connected to the power supply Vcc. Among them, the reference voltage Vref provided by the second voltage stabilizing circuit is 2.495V, the output voltage Vout of the DC / DC output power loop load is 5V, and the voltage dividing resistor R4 is generally 10kΩ, and the voltage dividing resistor R5 is determined according to (R4xVout) / (Vref)-R4.

[0035] Further, the operational amplifier U1 and the operational amplifier U3 can adopt the LM158 low-power double operational amplifier.

[0036] Based on the composition structure of the above low-power short-circuit protection circuit, the working principle of the technical scheme is as follows:

[0037] Current detection: the power resistor R1 in the current detection unit is connected in series in the DC / DC output power loop. When the current in the DC / DC output power loop is normal, the voltage across the power resistor R1 is in a normal range. When overcurrent or short circuit occurs, according to Ohm's law (U=IR), the voltage across the power resistor R1 will change significantly. This changed voltage signal is transmitted to the operational amplifier U3 through the voltage dividing resistors R7-R10, and thus the voltage difference between the positive input end and the negative input end of the operational amplifier U3 will change according to the change of the voltage across the power resistor R1.

[0038] Signal adjustment and voltage stabilization: the input signal adjustment unit adjusts the signal at the negative input end of the operational amplifier U1 through the voltage dividing resistors R5 and R4. The voltage dividing resistor R5 inputs the voltage signal at the output end of the power resistor R1 after voltage division to the negative input end of the operational amplifier U1, and at the same time, the voltage dividing resistor R4 grounds it for determining the appropriate reference voltage. The first voltage stabilizing circuit provides a stable reference voltage for the operational amplifier U3, so that the operational amplifier U3 can accurately compare the input signal. The second voltage stabilizing circuit provides a stable voltage for the positive input end of the operational amplifier U1, ensuring the operational stability of the operational amplifier U1.

[0039] Operational amplification and comparison: Operational amplifier U3 performs amplification operation according to the voltage difference between the positive input terminal and the negative input terminal. Operational amplifier U1 also performs amplification operation according to the voltage difference between its positive input terminal and negative input terminal.

[0040] Protection signal output: After the operation of operational amplifier U3 and operational amplifier U1, the output signal is integrated by the protection signal output circuit. Under normal circumstances, the output signal will not trigger the protection action. When a short circuit condition is detected, the output signals of operational amplifier U3 and operational amplifier U1 are output through the protection signal output circuit to realize short circuit protection for the DC / DC converter. In this process, the resistance R2 is associated with the output signal of the operational amplifier U1, which plays a role in assisting the construction of the circuit connection relationship. When the output signal of operational amplifier U1 changes, the voltage across resistance R2 will also change accordingly, and it cooperates with the protection signal output circuit to complete the final protection signal output function, etc.

[0041] Throughout the process, since operational amplifiers U1 and U3 use LM158 low-power dual operational amplifiers, the power consumption of the circuit can be reduced while ensuring short circuit protection function.

[0042] Example 2

[0043] This embodiment discloses a low-power short circuit protection circuit for a DC / DC converter. As a preferred embodiment of this embodiment, it is based on Example 1, and the first voltage stabilizing circuit includes a voltage stabilizing tube U4 and a current limiting resistor R11; the positive electrode of the voltage stabilizing tube U4 is connected to ground; the negative electrode of the voltage stabilizing tube U4 is connected to the power supply Vcc through the current limiting resistor R11; and the voltage dividing resistor R9 and the voltage dividing resistor R10 are connected to the negative electrode of the voltage stabilizing tube U4.

[0044] Based on the above circuit structure, the working principle is as follows:

[0045] 1) Voltage stabilizing principle

[0046] When the power supply Vcc is connected to the circuit, the current flows through the current limiting resistor R11 to the voltage stabilizing tube U4. The voltage stabilizing tube U4 is a special semiconductor device that has a reverse breakdown characteristic. In normal working state, when the reverse voltage reaches a certain value (voltage stabilizing value), the voltage across the voltage stabilizing tube U4 remains stable.

[0047] The current limiting resistor R11 plays a role in limiting current to prevent the current through the voltage stabilizing tube U4 from being too large and damaging the voltage stabilizing tube. According to Ohm's law I=U / R, the difference between the power supply Vcc and the voltage stabilizing value of the voltage stabilizing tube U4 divided by the resistance value of the current limiting resistor R11 can obtain the current size through the current limiting resistor R11.

[0048] 2) Provide reference voltage for operational amplifier U3

[0049] The negative pole of the voltage stabilizing tube U4 is connected to the input end of the operational amplifier U3 through the voltage dividing resistor R9 and the voltage dividing resistor R10. Due to the voltage stabilizing effect of the voltage stabilizing tube U4, the voltage output by the negative pole is a stable voltage value, and this stable voltage is divided by the voltage dividing resistors R9 and R10 to provide a stable reference voltage for the positive input end and the reverse input end of the operational amplifier U3, so that the operational amplifier U3 can accurately compare the input signal and further reliably determine whether an overcurrent or a short circuit condition occurs. For example, if there is no stable reference voltage, factors such as fluctuations in the power supply voltage can cause the operational amplifier U3 to misjudge whether the voltage change at both ends of the power resistor R1 is caused by a short circuit.

[0050] Embodiment 3

[0051] This embodiment discloses a low-power short-circuit protection circuit for a DC / DC converter. As a preferred embodiment of this embodiment, the second voltage stabilizing circuit includes a three-terminal voltage stabilizer U2 and a current-limiting resistor R6, based on Embodiment 1 or 2. The negative pole and the reference end of the three-terminal voltage stabilizer U2 are connected to the power supply Vcc through the current-limiting resistor R6, the positive pole of the three-terminal voltage stabilizer U2 is grounded, and the positive input end of the operational amplifier U1 is connected to the negative pole of the three-terminal voltage stabilizer U2. The three-terminal voltage stabilizer U2 can be a TL431 three-terminal voltage stabilizer, and its reference level Vref is 2.495V.

[0052] Based on the above circuit structure, the working principle is as follows:

[0053] 1) Voltage stabilizing process

[0054] The three-terminal voltage stabilizer U2 is a device that can output a stable voltage under conditions such as changes in input voltage and changes in load. When the power supply Vcc is connected to the negative pole and the reference end of the three-terminal voltage stabilizer U2 through the current-limiting resistor R6, the three-terminal voltage stabilizer U2 adjusts the input voltage according to its internal circuit structure and working principle.

[0055] The current-limiting resistor R6 functions to limit the size of the current flowing into the three-terminal voltage stabilizer U2, preventing excessive current from damaging the three-terminal voltage stabilizer U2. The resistance value can be determined by Ohm's law I=U / R according to the voltage of the power supply Vcc, the rated current of the three-terminal voltage stabilizer U2, and other parameters to determine an appropriate value.

[0056] 2) Providing a stable reference voltage for the operational amplifier U1

[0057] The positive input terminal of the operational amplifier U1 is connected to the negative terminal of the three-terminal voltage regulator U2, so that the operational amplifier U1 can obtain a stable voltage as a reference voltage. This stable reference voltage is very important for the operational amplifier U1 to accurately compare the voltage signals at its positive input terminal and negative input terminal. During the operation of the circuit, the positive input terminal of the operational amplifier U1 can maintain a relatively stable voltage regardless of the voltage fluctuations of the power supply Vcc or the changes in the load, thereby ensuring that the operational amplifier U1 can correctly perform signal comparison and subsequent operations, providing a guarantee for the stable operation of the entire short circuit protection circuit.

[0058] Embodiment 4

[0059] The embodiment discloses a low-power short circuit protection circuit for a DC / DC converter. As a preferred embodiment of the embodiment, the low-power short circuit protection circuit further comprises a first feedback circuit based on the embodiments 1, 2 or 3, and the first feedback circuit comprises a resistor R12 and a capacitor C1. The output terminal of the operational amplifier U3 is connected to the negative input terminal of the operational amplifier U3 through the capacitor C1 and the resistor R12, which plays a role of operational amplifier loop compensation.

[0060] Based on the above circuit structure, the working principle is as follows:

[0061] 1) Feedback principle basis: the output terminal of the operational amplifier U3 is connected to the negative input terminal of the operational amplifier U3 through the capacitor C1 and the resistor R12, which constitutes a feedback loop. The main function of this feedback loop is to adjust the output signal of the operational amplifier U3.

[0062] 2) Function of capacitor C1: the capacitor C1 has the characteristics of blocking direct current and passing alternating current. In the circuit, it can block direct current signals through the feedback loop and only allow alternating current signals to pass. In this way, the direct current bias at the output terminal of the operational amplifier U3 can be avoided to affect the feedback signal, so that the feedback signal mainly reflects the alternating change part of the output signal. For example, when the output signal of the operational amplifier U3 has a transient high-frequency fluctuation, the capacitor C1 can transmit this high-frequency alternating current signal to the negative input terminal, so that the operational amplifier U3 can adjust this fluctuation.

[0063] 3) The role of resistor R12: Resistor R12, together with capacitor C1, determines the time constant of the feedback loop. The time constant affects the rate of change of the feedback signal. When the output signal of operational amplifier U3 changes, the feedback signal returns to the inverting input at a rate determined by the time constant, thereby affecting the amplification factor and output characteristics of operational amplifier U3. A smaller time constant means that the feedback signal can respond more quickly to changes in the output signal, allowing the output of operational amplifier U3 to stabilize more quickly and avoid instability such as oscillation. For example, if there is a step change in the output of operational amplifier U3, appropriate selection of the values of resistor R12 and capacitor C1 can allow the feedback signal to return to the inverting input at an appropriate rate, allowing the output of operational amplifier U3 to quickly reach a stable value.

[0064] Example 5

[0065] This embodiment discloses a low-power short-circuit protection circuit for a DC / DC converter. As a preferred embodiment of this embodiment, it is based on Examples 1, 2, 3, or 4, and further includes a second feedback circuit, which includes resistor R3 and capacitor C2. The output of operational amplifier U1 is connected to the inverting input of operational amplifier U1 through capacitor C2 and resistor R3, serving as loop compensation in the feedback signal loop.

[0066] Based on the above circuit structure, the working principle is as follows:

[0067] 1) Basic feedback principle: The output of operational amplifier U1 is connected to its inverting input through capacitor C2 and resistor R3, forming a feedback loop. This feedback structure is mainly used to stabilize the output signal of operational amplifier U1.

[0068] 2) The role of capacitor C2: Capacitor C2 can block DC signals and only allow AC signals to pass through the feedback loop. In this way, the DC component in the output signal will not interfere with the feedback process, while the AC component (such as noise, fluctuations, etc. in the output signal) can be fed back to the inverting input of operational amplifier U1. For example, when the circuit is started or disturbed, the output of operational amplifier U1 may have a DC offset, which can be prevented from affecting subsequent operations through the feedback loop by capacitor C2, so that the feedback signal mainly adjusts for the AC changes in the output signal.

[0069] 3) The role of resistor R3: Resistor R3, together with capacitor C2, determines the time constant of the feedback loop. This time constant controls the response speed of the feedback signal. When the output signal of operational amplifier U1 changes, the feedback signal returns to the inverting input at a rate determined by the time constant. If the time constant is small, the feedback signal can respond to changes in the output signal more quickly, helping the output of operational amplifier U1 to reach a stable state quickly and avoiding unstable phenomena such as oscillation or over-amplification of the output signal. For example, when the output of operational amplifier U1 has a rapidly changing signal, a suitable time constant allows the feedback signal to adjust the amplification factor of operational amplifier U1 in a timely manner, thereby stabilizing the output.

[0070] Example 6

[0071] This embodiment discloses a low-power short-circuit protection circuit for a DC / DC converter. As a preferred implementation of this embodiment, based on embodiments 1, 2, 3, 4, or 5, it further includes a first filter circuit and a second filter circuit. The first filter circuit includes a filter capacitor C4, and the inverting input terminal of operational amplifier U3 is grounded through the filter capacitor C4. The second filter circuit includes a filter capacitor C3, and the non-inverting input terminal of operational amplifier U1 is grounded through the filter capacitor C3.

[0072] Based on the above circuit structure, its working principle is as follows:

[0073] 1) Working principle of the first filter circuit

[0074] Basic filtering principle: The filter capacitor C4 is connected between the inverting input terminal of the operational amplifier U3 and ground. It is mainly used to filter out noise signals at this node and smooth the voltage signal.

[0075] Bypassing high-frequency signals: When high-frequency interference signals are present in the circuit, according to the capacitive reactance characteristics of capacitors, the capacitive reactance of capacitor C4 is very small for high-frequency signals. This allows the high-frequency interference signals to be bypassed to ground through capacitor C4, thereby reducing high-frequency noise entering the inverting input terminal of operational amplifier U3. This allows operational amplifier U3 to receive a relatively clean input signal, which helps improve the accuracy of operational amplifier U3 in comparing and amplifying signals.

[0076] Stabilizing the input voltage: When power supply fluctuations or other factors cause slight fluctuations in the voltage signal, the filter capacitor C4 can stabilize the voltage at the inverting input of the operational amplifier U3 through its charging and discharging process. For example, when the input voltage rises instantaneously, capacitor C4 charges to absorb excess charge; when the input voltage drops, capacitor C4 discharges to replenish charge, making the voltage change at the inverting input of the operational amplifier U3 relatively gradual.

[0077] 2) Working principle of the second filter circuit

[0078] Filtering function implementation: The filter capacitor C3 is connected between the positive input terminal of the operational amplifier U1 and ground, and its main purpose is also filtering.

[0079] High-frequency noise removal: For high-frequency noise that may appear at the positive input of operational amplifier U1, since the capacitive reactance of capacitor C3 is inversely proportional to frequency, the high-frequency noise can be easily bypassed to ground through capacitor C3. This prevents this high-frequency noise from interfering with the normal operation of operational amplifier U1, ensuring that the positive input of operational amplifier U1 receives a relatively clean reference voltage signal, thereby guaranteeing that operational amplifier U1 can accurately perform signal comparison and amplification operations.

[0080] Stabilizing the reference voltage: Similar to filter capacitor C4, filter capacitor C3 also plays an important role in stabilizing the voltage at the positive input terminal of operational amplifier U1. It can buffer voltage fluctuations caused by factors such as power supply issues to a certain extent, providing a more stable operating environment for operational amplifier U1 and improving the stability and reliability of the entire circuit.

[0081] Example 7

[0082] This embodiment discloses a low-power short-circuit protection circuit for a DC / DC converter. As a preferred implementation of this embodiment, based on embodiments 1, 2, 3, 4, 5 or 6, its protection signal output circuit includes a diode D2 and a signal output port Vcomp; the positive terminal of the diode D2 is connected to the output terminal of the operational amplifier U1, and the negative terminal is connected to the output terminal of the operational amplifier U3; the signal output port Vcomp is connected to the positive terminal of the diode D2.

[0083] Based on the above circuit structure, its working principle is as follows:

[0084] 1) Signal integration and unidirectional conduction

[0085] The anode of diode D2 is connected to the output terminal of operational amplifier U1, and the cathode is connected to the output terminal of operational amplifier U3. Diodes have unidirectional conductivity; when operational amplifiers U1 and U3 output signals, the signal can only flow from the output terminal of operational amplifier U1 (the anode of diode D2) to the output terminal of operational amplifier U3 (the cathode of diode D2). This connection method allows the output signals of the two operational amplifiers to be integrated at diode D2. For example, under normal operating conditions, the output signals of the two operational amplifiers may be within the normal range. After integration by diode D2, the signal output at the signal output port Vcomp is also within the normal range, and subsequent protection actions will not be triggered.

[0086] 2) Short circuit protection signal output

[0087] When a short circuit occurs in the circuit, operational amplifiers U1 and U3 perform calculations based on their input signals (from the current detection unit, etc.), resulting in a change in their output signals. These changed signals are output to the signal output port Vcomp via diode D2. Due to the unidirectional conductivity of diode D2, the signal is output in the correct direction, and in the event of a short circuit, the output protection signal can be accurately transmitted to subsequent protection devices (such as the control circuit connected to the Vcomp port), thereby achieving short-circuit protection for the DC / DC converter. For example, without the unidirectional control of diode D2, abnormal conditions such as reverse current may occur, causing the short-circuit protection function to fail.

[0088] Based on the above principle, when the DC / DC output power circuit is overcurrent or short-circuited, the output of the operational amplifier U1 is pulled low, which further pulls the level of the signal output port Vcomp low. The controller of the DC / DC converter has no output, thereby reducing the input current and achieving the purpose of low power consumption. When the fault mode is eliminated, the level of the signal output port Vcomp returns to the normal value.

[0089] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-power short-circuit protection circuit for a DC / DC converter, comprising the DC / DC output power circuit of the DC / DC converter, characterized in that: It also includes operational amplifier U3, operational amplifier U1, current detection unit, first voltage regulator circuit, second voltage regulator circuit, input signal conditioning unit and protection signal output circuit; The current detection unit includes a power resistor R1, a voltage divider resistor R7, a voltage divider resistor R8, a voltage divider resistor R9, and a voltage divider resistor R10; the power resistor R1 is connected in series in the DC / DC output power circuit; the input signal adjustment unit includes a voltage divider resistor R5 and a voltage divider resistor R4. The positive input terminal of the operational amplifier U3 is connected to the input terminal of the power resistor R1 through a voltage divider resistor R7, and is connected to the first voltage regulator circuit through a voltage divider resistor R9; the inverting input terminal of the operational amplifier U3 is connected to the output terminal of the power resistor R1 through a voltage divider resistor R8, and is connected to the voltage regulator circuit through a voltage divider resistor R10; the output terminal of the operational amplifier U3 is connected to the protection signal output circuit; the positive power supply terminal of the operational amplifier U3 is connected to the power supply Vcc. The positive input terminal of the operational amplifier U1 is connected to the second voltage regulator circuit; the inverting input terminal of the operational amplifier U1 is connected to the output terminal of the power resistor R1 through the voltage divider resistor R5, and grounded through the voltage divider resistor R4; the output terminal of the operational amplifier U1 is connected to the protection signal output circuit, and is also connected to the power supply Vcc through the resistor R2; the positive power supply terminal of the operational amplifier U1 is connected to the power supply Vcc.

2. The low-power short-circuit protection circuit for a DC / DC converter as described in claim 1, characterized in that: The first voltage regulator circuit includes a Zener diode U4 and a current-limiting resistor R11; the positive terminal of the Zener diode U4 is grounded; the negative terminal of the Zener diode U4 is connected to the power supply Vcc through the current-limiting resistor R11; the voltage divider resistors R9 and R10 are connected to the negative terminal of the Zener diode U4.

3. The low-power short-circuit protection circuit for a DC / DC converter as described in claim 1, characterized in that: The second voltage regulator circuit includes a three-terminal regulator U2 and a current-limiting resistor R6; the negative terminal and the reference terminal of the three-terminal regulator U2 are connected to the power supply Vcc through the current-limiting resistor R6, the positive terminal of the three-terminal regulator U2 is grounded, and the positive input terminal of the operational amplifier U1 is connected to the negative terminal of the three-terminal regulator U2.

4. The low-power short-circuit protection circuit for a DC / DC converter as described in claim 1, characterized in that: It also includes a first feedback circuit, which includes a resistor R12 and a capacitor C1; the output terminal of the operational amplifier U3 is connected to the inverting input terminal of the operational amplifier U3 through the capacitor C1 and the resistor R12.

5. The low-power short-circuit protection circuit for a DC / DC converter as described in claim 1, characterized in that: It also includes a second feedback circuit, which includes a resistor R3 and a capacitor C2; the output terminal of the operational amplifier U1 is connected to the inverting input terminal of the operational amplifier U1 through the capacitor C2 and the resistor R3.

6. The low-power short-circuit protection circuit for a DC / DC converter as described in claim 1, characterized in that: It also includes a first filter circuit, and the first filter circuit includes a filter capacitor C4; the inverting input terminal of the operational amplifier U3 is grounded through the filter capacitor C4.

7. The low-power short-circuit protection circuit for a DC / DC converter as described in claim 1, characterized in that: It also includes a second filter circuit, and the second filter circuit includes a filter capacitor C3; the positive input terminal of the operational amplifier U1 is grounded through the filter capacitor C3.

8. The low-power short-circuit protection circuit for a DC / DC converter as described in claim 1, characterized in that: The protection signal output circuit includes a diode D2 and a signal output port Vcomp; the positive terminal of the diode D2 is connected to the output terminal of the operational amplifier U1, and the negative terminal is connected to the output terminal of the operational amplifier U3; the signal output port Vcomp is connected to the positive terminal of the diode D2.

9. The low-power short-circuit protection circuit for a DC / DC converter as described in claim 1, characterized in that: The operational amplifiers U1 and U3 are LM158 low-power dual operational amplifiers.

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