Overvoltage protection circuit for a DC-DC converter

Abstract

The utility model discloses a kind of overvoltage protection circuit of DC-DC converter, it is related to circuit technical field, comprising: voltage reference source U1 has three pins, the first pin of voltage reference source U1 is electrically connected by resistance R4 with the base of triode Q1, second pin is electrically connected with the output end of DC-DC converter by voltage dividing resistance R1 and voltage dividing resistance R2, third pin is grounded;Emitting electrode of triode Q1 is electrically connected with power supply, the collector of triode Q1 is electrically connected with the base of triode Q2 by voltage dividing resistance R7 and voltage dividing resistance R8, the collector of triode Q1 is electrically connected with the second pin of voltage reference source U1 by diode D1, current-limiting resistance R6 and voltage reference source U1 voltage reference source U1;The collector of triode Q2 is electrically connected with the enable pin of DC-DC converter, the emitter of triode Q2 is grounded.The utility model circuit simple structure, low in cost, high reliability, can effectively realize the locking protection after output overvoltage, avoid system in fault not thoroughly before automatic recovery.

Description

Technical Field

[0001] This utility model relates to the field of circuit technology, specifically to an overvoltage protection circuit for a DC-DC converter. Background Technology

[0002] DC-DC converters are widely used in modern electronic devices, and their output stability directly affects system safety. Currently, DC-DC converters are equipped with output overvoltage protection circuits, and some circuit systems require overvoltage protection for the DC-DC converter when the output voltage is too high.

[0003] Existing DC-DC converter overvoltage protection circuits generally have the defect of automatically restoring output after overvoltage is cleared. However, this may pose a risk in some application scenarios. For example, some systems require the DC-DC converter to remain locked in a no-output state after an output overvoltage until the system is completely restarted. This cannot meet the system's locking requirement for continuous overvoltage faults, and the protection state needs to be cleared by power-off restart.

[0004] Therefore, how to provide a simple, reliable, and low-cost overvoltage protection circuit is an important issue that urgently needs to be addressed in the industry. Utility Model Content

[0005] In view of this, this utility model embodiment provides an overvoltage protection circuit for a DC-DC converter, thereby solving the problem that the overvoltage protection circuit of the DC-DC converter cannot meet the system's lockout requirement for continuous overvoltage faults.

[0006] According to a first aspect, this utility model provides an overvoltage protection circuit for a DC-DC converter, the circuit comprising: DC-DC converter, voltage reference source U1, transistor Q1, transistor Q2, and current limiting resistor R6; The voltage reference source U1 has three pins. The first pin of the voltage reference source U1 is electrically connected to the base of the transistor Q1 through resistor R4. The second pin is electrically connected to the output terminal of the DC-DC converter through voltage divider resistors R1 and R2. The third pin is grounded. The voltage reference source U1 is used to detect whether the output voltage of the DC-DC converter is over-voltage. The emitter of transistor Q1 is electrically connected to the power supply. The collector of transistor Q1 is electrically connected to the base of transistor Q2 through voltage divider resistors R7 and R8. The collector of transistor Q1 is electrically connected to the second pin of voltage reference source U1 through diode D1 and current-limiting resistor R6. The anode of diode D1 is electrically connected to the collector of transistor Q1, the cathode of diode D1 is electrically connected to one end of current-limiting resistor R6, and the other end of current-limiting resistor R6 is electrically connected to the collector of transistor Q1. The collector of transistor Q2 is electrically connected to the enable pin of the DC-DC converter, and the emitter of transistor Q2 is grounded.

[0007] In conjunction with the first aspect, in the first embodiment of the first aspect, the circuit further includes: The current-limiting resistor R3 and the capacitor C2 are connected in parallel. One end of the current-limiting resistor R3 is connected between the emitter of the transistor Q1 and the power supply, and the other end is connected between the base of the transistor Q1 and the resistor R4.

[0008] In conjunction with the first aspect, in the second embodiment of the first aspect, the circuit further includes: Capacitor C1, one end of voltage divider resistor R1 is electrically connected to the output terminal of the DC-DC converter, the other end of voltage divider resistor R1 is electrically connected to voltage divider resistor R2 and the second pin of voltage reference source U1, one end of voltage divider resistor R2 is electrically connected to the other end of voltage divider resistor R1 and the second pin of voltage reference source U1, the other end of voltage divider resistor R2 is grounded, and capacitor C1 and voltage divider resistor R2 are connected in parallel.

[0009] In conjunction with the first aspect, in the third embodiment of the first aspect, the circuit further includes: Capacitor C3 is connected between the emitter and base of transistor Q2.

[0010] In conjunction with the first aspect, in the fourth embodiment of the first aspect, the second pin of the voltage reference source U1 is grounded through resistor R5.

[0011] In conjunction with the first aspect, in the fifth embodiment of the first aspect, one end of the voltage divider resistor R7 is electrically connected to the collector of the transistor Q1, the other end of the voltage divider resistor R7 is electrically connected to one end of the voltage divider resistor R8 and the base of the transistor Q2, one end of the voltage divider resistor R8 is electrically connected to the other end of the voltage divider resistor R7 and the base of the transistor Q2, and the other end of the voltage divider resistor R8 is grounded.

[0012] In conjunction with the first aspect, in the sixth embodiment of the first aspect, the reference terminal voltage of the voltage reference source U1 is set to 2.5V.

[0013] In conjunction with the first aspect, in the seventh embodiment of the first aspect, the voltage reference source U1 adopts a TL431 voltage regulator.

[0014] In conjunction with the first aspect, in the eighth embodiment of the first aspect, the transistor Q1 is a BT4403 type PNP transistor.

[0015] In conjunction with the first aspect, in the ninth embodiment of the first aspect, the transistor Q2 is an NPN transistor of type BT4401.

[0016] This invention relates to an overvoltage protection circuit for a DC-DC converter. Through transistor Q1, diode D1, and current-limiting resistor R6, the circuit ensures that after an overvoltage event, the voltage of the power supply VCC continues to flow through the second pin of the voltage reference source U1. This allows the second pin of the voltage reference source U1 to maintain its reference voltage, thus keeping the DC-DC converter in a locked, no-output state. Only after disconnecting the power supply VCC, restarting the system, and powering it back on will the voltages of all components in the circuit reset, allowing the DC-DC converter to return to normal operation. The placement of resistors and capacitors in the circuit improves its stability and reliability. The circuit is simple in structure, low in cost, and highly reliable, effectively achieving lockout protection after an output overvoltage, preventing the system from automatically recovering before the fault is completely eliminated, thus enhancing system safety. It possesses high practicality and application value. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] in: Figure 1 A circuit diagram of the overvoltage protection circuit of the DC-DC converter provided by this utility model is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0020] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0021] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0022] DC-DC converters are widely used in modern electronic devices, and their output stability directly affects system safety. Currently, DC-DC converters are equipped with output overvoltage protection circuits, and some circuit systems require overvoltage protection for the DC-DC converter when the output voltage is too high.

[0023] Existing DC-DC converter overvoltage protection circuits generally have the defect of automatically restoring output after overvoltage is cleared. However, this may pose a risk in some application scenarios. For example, some systems require the DC-DC converter to remain locked in a no-output state after an output overvoltage until the system is completely restarted. This cannot meet the system's locking requirement for continuous overvoltage faults, and the protection state needs to be cleared by power-off restart.

[0024] Therefore, how to provide a simple, reliable, and low-cost overvoltage protection circuit is an important issue that urgently needs to be addressed in the industry.

[0025] To address the aforementioned issues, this specification provides an overvoltage protection circuit for a DC-DC converter. For example... Figure 1 As shown, the circuit includes: The circuit consists of a DC-DC converter, a voltage reference source U1, transistors Q1 and Q2, voltage divider resistors R1 and R2, current-limiting resistors R3, R4, R5, R6, voltage divider resistors R7 and R8, a diode D1, capacitors C1, C2, and C3. The core components of this circuit are the voltage reference source, transistors Q1 and Q2, which form an overvoltage protection and self-locking protection circuit. This circuit comprises the following three parts: Voltage detection section: It consists of voltage reference source U1 and its surrounding resistors and capacitors, and is used to detect whether the output voltage of the DC-DC converter is over-voltage.

[0026] In this embodiment, the voltage reference source U1 uses a TL431 regulated power supply. The voltage reference source U1 has three pins: a first pin (cathode), a second pin (reference pin), and a third pin (anode). The first pin of the voltage reference source U1 is electrically connected to the base of the transistor Q1 through a resistor R4. The second pin is electrically connected to the output terminal OUT of the DC-DC converter through voltage divider resistors R1 and R2. One end of the voltage divider resistor R1 is electrically connected to the output terminal of the DC-DC converter, and the other end of the voltage divider resistor R1 is electrically connected to the voltage divider resistor R2 and the second pin of the voltage reference source U1. One end of the voltage divider resistor R2 is electrically connected to the other end of the voltage divider resistor R1 and the second pin of the voltage reference source U1, and the other end of the voltage divider resistor R2 is grounded. Capacitor C1 is connected in parallel with the voltage divider resistor R2. The second pin of the voltage reference source U1 is grounded through a resistor R5, and the third pin is grounded.

[0027] The reference voltage of the voltage reference source U1 is set to 2.5V.

[0028] The self-locking control section, composed of transistors Q1 and Q2, controls the level of the enable pin ENA of the DC-DC converter. The emitter of transistor Q1 is electrically connected to the power supply. The collector of transistor Q1 is electrically connected to the base of transistor Q2 through voltage divider resistors R7 and R8. The collector of transistor Q1 is electrically connected to the second pin of voltage reference source U1 through diode D1 and current-limiting resistor R6. The anode of diode D1 is electrically connected to the collector of transistor Q1, and the cathode of diode D1 is electrically connected to one end of current-limiting resistor R6. The other end of current-limiting resistor R6 is electrically connected to the collector of transistor Q1. Current-limiting resistor R3 is connected in parallel with capacitor C2, with one end connected to transistor Q1. One end of transistor Q1 is connected to the power supply, and the other end is connected between the base of transistor Q1 and resistor R4. The collector of transistor Q2 is electrically connected to the enable pin of the DC-DC converter, and the emitter of transistor Q2 is grounded. Capacitor C3 is connected between the emitter and base of transistor Q2. One end of voltage divider resistor R7 is electrically connected to the collector of transistor Q1, and the other end of voltage divider resistor R7 is electrically connected to one end of voltage divider resistor R8 and the base of transistor Q2. One end of voltage divider resistor R8 is electrically connected to the other end of voltage divider resistor R7 and the base of transistor Q2, and the other end of voltage divider resistor R8 is grounded. In this embodiment, transistor Q1 is a BT4403 PNP transistor, and transistor Q2 is a BT4401 NPN transistor.

[0029] Capacitors C1, C2, and C3 all serve to filter out interference signals. The specific capacitance values ​​of capacitors C1, C2, and C3 are selected based on the frequency of the interference signal to be filtered. Resistor R5 stabilizes the level of the enable pin ENA.

[0030] When no overvoltage occurs at the output of the DC-DC converter, after voltage division, the voltage at the second pin of the voltage reference source U1 does not reach the reference terminal voltage. At this time, the first pin of the voltage reference source U1 is in the cutoff state, so transistors Q1 and Q2 are also in the cutoff state. The enable pin ENA of the DC-DC converter is not pulled low and remains at the normal level. The DC-DC converter is in normal working state.

[0031] When an overvoltage occurs at the output of the DC-DC converter, after voltage division, the voltage at the second pin of the voltage reference source U1 reaches the reference voltage. At this time, the voltage reference source U1 starts to work, and the current flows through the first pin of the voltage reference source U1 and resistor R4 to the base of transistor Q1, causing transistor Q1 to conduct. When transistor Q1 conducts, its collector current provides current to the base of transistor Q2, thereby causing transistor Q2 to also conduct. When transistor Q2 conducts, it continuously pulls down the level of the enable pin ENA of the DC-DC converter, thus causing the DC-DC converter to remain in a no-output state.

[0032] During an overvoltage event at the output of the DC-DC converter, because transistor Q1 is turned on, the voltage of the power supply VCC will continuously flow through the second pin of the voltage reference source U1 through the self-locking path formed by diode D1 and resistor R6. Therefore, even if the overvoltage condition is relieved, the second pin of the voltage reference source U1 can still maintain the reference voltage, i.e., 2.5V. The first pin of the voltage reference source U1 also remains on, and correspondingly, transistors Q1 and Q2 also remain on. In this way, the level of the enable pin ENA of the DC-DC converter will be continuously pulled low, and the DC-DC converter will remain in a no-output state.

[0033] When the power supply VCC is de-energized Figure 1 The voltages at the VCC, OUT, and ENA terminals will be reset. By restarting the system and powering it back on, transistors Q1 and Q2 will be reset to the off state, so the level of the enable pin ENA of the DC-DC converter will not be pulled low and will return to the normal level, and the DC-DC converter will re-enter the normal working state.

[0034] This invention relates to an overvoltage protection circuit for a DC-DC converter. Through transistor Q1, diode D1, and current-limiting resistor R6, the circuit ensures that after an overvoltage event, the voltage of the power supply VCC continues to flow through the second pin of the voltage reference source U1. This allows the second pin of the voltage reference source U1 to maintain its reference voltage, thus keeping the DC-DC converter in a locked, no-output state. Only after disconnecting the power supply VCC, restarting the system, and powering it back on will the voltages of all components in the circuit reset, allowing the DC-DC converter to return to normal operation. The placement of resistors and capacitors in the circuit improves its stability and reliability. The circuit is simple in structure, low in cost, and highly reliable, effectively achieving lockout protection after an output overvoltage, preventing the system from automatically recovering before the fault is completely eliminated, thus enhancing system safety. It possesses high practicality and application value.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. An overvoltage protection circuit for a DC-DC converter, characterized in that, The circuit includes: DC-DC converter, voltage reference source U1, transistor Q1, transistor Q2, and current limiting resistor R6; The voltage reference source U1 has three pins. The first pin of the voltage reference source U1 is electrically connected to the base of the transistor Q1 through resistor R4. The second pin is electrically connected to the output terminal of the DC-DC converter through voltage divider resistors R1 and R2. The third pin is grounded. The voltage reference source U1 is used to detect whether the output voltage of the DC-DC converter is over-voltage. The emitter of transistor Q1 is electrically connected to the power supply. The collector of transistor Q1 is electrically connected to the base of transistor Q2 through voltage divider resistors R7 and R8. The collector of transistor Q1 is electrically connected to the second pin of voltage reference source U1 through diode D1 and current-limiting resistor R6. The anode of diode D1 is electrically connected to the collector of transistor Q1, the cathode of diode D1 is electrically connected to one end of current-limiting resistor R6, and the other end of current-limiting resistor R6 is electrically connected to the collector of transistor Q1. The collector of transistor Q2 is electrically connected to the enable pin of the DC-DC converter, and the emitter of transistor Q2 is grounded.

2. The overvoltage protection circuit for the DC-DC converter according to claim 1, characterized in that, The circuit also includes: The current-limiting resistor R3 and the capacitor C2 are connected in parallel. One end of the current-limiting resistor R3 is connected between the emitter of the transistor Q1 and the power supply, and the other end is connected between the base of the transistor Q1 and the resistor R4.

3. The overvoltage protection circuit for the DC-DC converter according to claim 1, characterized in that, The circuit also includes: Capacitor C1, one end of voltage divider resistor R1 is electrically connected to the output terminal of the DC-DC converter, the other end of voltage divider resistor R1 is electrically connected to voltage divider resistor R2 and the second pin of voltage reference source U1, one end of voltage divider resistor R2 is electrically connected to the other end of voltage divider resistor R1 and the second pin of voltage reference source U1, the other end of voltage divider resistor R2 is grounded, and capacitor C1 and voltage divider resistor R2 are connected in parallel.

4. The overvoltage protection circuit for the DC-DC converter according to claim 1, characterized in that, The circuit also includes: Capacitor C3 is connected between the emitter and base of transistor Q2.

5. The overvoltage protection circuit for the DC-DC converter according to claim 1, characterized in that, The second pin of the voltage reference source U1 is grounded through resistor R5.

6. The overvoltage protection circuit for the DC-DC converter according to claim 1, characterized in that, One end of the voltage divider resistor R7 is electrically connected to the collector of the transistor Q1, and the other end of the voltage divider resistor R7 is electrically connected to one end of the voltage divider resistor R8 and the base of the transistor Q2. One end of the voltage divider resistor R8 is electrically connected to the other end of the voltage divider resistor R7 and the base of the transistor Q2, and the other end of the voltage divider resistor R8 is grounded.

7. The overvoltage protection circuit for the DC-DC converter according to claim 1, characterized in that, The reference voltage of the voltage reference source U1 is set to 2.5V.

8. The overvoltage protection circuit for the DC-DC converter according to claim 1, characterized in that, The voltage reference source U1 is a TL431 voltage regulator.

9. The overvoltage protection circuit for the DC-DC converter according to claim 1, characterized in that, The transistor Q1 is a BT4403 PNP transistor.

10. The overvoltage protection circuit for the DC-DC converter according to claim 1, characterized in that, The transistor Q2 is a BT4401 NPN transistor.

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