DC-DC constant voltage circuit and overvoltage protection constant voltage output device

Abstract

The utility model provides a DC-DC constant voltage circuit and an overvoltage protection constant voltage output device, the circuit comprises an input circuit, a switch control circuit and an output circuit, and the input circuit is used for receiving and outputting an input voltage; the switch control circuit comprises an eighth resistor, a ninth resistor, a tenth resistor, a first control tube, a second control tube and a third control tube; the output circuit comprises a thirteenth resistor, a sliding resistor, a first voltage stabilizing diode, a fourth control tube, a fifth control tube and a second capacitor. When the input voltage exceeds a threshold value set by the input circuit, the second control tube is conducted and grounded, so that the first control tube and the third control tube are sequentially switched off, and an overvoltage protection effect is achieved; when the input voltage is in a normal range, the second control tube is switched off, the first control tube and the third control tube are sequentially switched on, and then the fourth control tube is matched with the fifth control tube to be switched on, so that a constant-voltage output function is realized. Therefore, the circuit can realize overvoltage protection and constant voltage output.

Description

Technical Field

[0001] The present disclosure relates to the technical field of overvoltage protection and constant voltage output, and in particular to a DC-DC constant voltage circuit and an overvoltage protection constant voltage output device. Background Art

[0002] There are many overvoltage protection devices and constant voltage output devices on the market, and the functions of the internal circuit diagrams are also diverse. However, when the device can achieve overvoltage protection, it cannot achieve constant voltage output, or when it can achieve constant voltage output, it cannot achieve overvoltage protection. Similarly, when applying DC-DC circuits, it is impossible to achieve overvoltage protection and constant voltage output at the same time.

[0003] For example, Figure 1 To prevent overvoltage circuits, although overvoltage protection can be achieved by controlling the switching state of the PMOS tube through the level state of each stage of the PNP transistor, constant voltage output cannot be guaranteed when the voltage is within the normal range; Figure 2 For a voltage control circuit, even if the voltage output can be achieved through a comparator, inductor, etc., the overvoltage protection effect cannot be guaranteed.

[0004] Therefore, it is necessary to design a DC-DC circuit that can achieve overvoltage protection and constant voltage output at the same time. Utility Model Content

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a DC-DC constant voltage circuit and an overvoltage protection constant voltage output device that can simultaneously achieve overvoltage protection and constant voltage output.

[0006] The purpose of this disclosure is achieved through the following technical solutions:

[0007] A DC-DC constant voltage circuit, comprising:

[0008] An input circuit, used for receiving an input voltage and outputting it, wherein an input terminal of the input circuit is connected to a power input terminal;

[0009] A switch control circuit comprises an eighth resistor, a ninth resistor, a tenth resistor, a first control tube, a second control tube and a third control tube, wherein the output end of the input circuit is respectively connected to the control end of the second control tube and the first end of the tenth resistor, the second end of the second control tube is connected to the second end of the tenth resistor, the second end of the tenth resistor is grounded, the first end of the eighth resistor is connected to the power input end, the second end of the eighth resistor is respectively connected to the first end of the second control tube and the control end of the first control tube, the first end of the ninth resistor is respectively connected to the first end of the eighth resistor and the first end of the third control tube, the second end of the ninth resistor is respectively connected to the control end of the third control tube and the first end of the first control tube, and the second end of the first control tube is grounded;

[0010] The output circuit includes a thirteenth resistor, a sliding resistor, a first voltage-stabilizing diode, a fourth control tube, a fifth control tube and a second capacitor. The second end of the third control tube is respectively connected to the first end of the fourth control tube, the first end of the fifth control tube and the first end of the thirteenth resistor. The second end of the thirteenth resistor is respectively connected to the cathode of the first voltage-stabilizing diode and the control end of the fifth control tube. The anode of the first voltage-stabilizing diode is grounded. The second end of the fifth control tube is respectively connected to the control end of the fourth control tube, the upper half end of the second capacitor and the sliding adjustment end of the sliding resistor. The lower half end of the second capacitor is grounded. The second end of the fourth control tube is grounded through the sliding resistor. The second end of the fourth control tube is used for constant voltage output.

[0011] In one embodiment, the output circuit further includes a fifteenth resistor, and the second end of the fourth control tube is grounded through the fifteenth resistor and the sliding resistor in sequence.

[0012] In one embodiment, the output circuit further includes a twelfth resistor, a first end of the twelfth resistor is connected to the second end of the third control tube, and a second end of the twelfth resistor is connected to the first end of the fifth control tube.

[0013] In one embodiment, the switch control circuit further includes a fifth resistor, a first end of the fifth resistor is connected to the output end of the input circuit, and a second end of the fifth resistor is connected to the control end of the second control transistor.

[0014] In one embodiment, at least one of the fifth resistor and the tenth resistor is a variable resistor.

[0015] In one embodiment, the switch control circuit further includes a sixth resistor, and the second end of the ninth resistor is connected to the first end of the first control tube through the sixth resistor.

[0016] In one embodiment, the switch control circuit further includes an eleventh resistor, a first end of the eleventh resistor is connected to the control end of the first control transistor, and a second end of the eleventh resistor is grounded.

[0017] In one embodiment, at least one of the eighth resistor and the eleventh resistor is a variable resistor.

[0018] In one embodiment, the switch control circuit further includes a fifth zener diode, an anode of the fifth zener diode is connected to the second end of the ninth resistor, and a cathode of the fifth zener diode is connected to the first end of the ninth resistor.

[0019] An overvoltage protection constant voltage output device comprises the DC-DC constant voltage circuit described in any one of the above embodiments.

[0020] Compared with the prior art, the present invention has at least the following advantages:

[0021] When the input voltage exceeds the threshold value set by the input circuit, the second control tube is turned on and grounded, so that the first control tube and the third control tube are turned off in sequence, which plays an overvoltage protection role; when the input voltage is within the normal range, the second control tube is turned off and the first control tube and the third control tube are turned on in sequence, and then the fourth control tube is turned on in coordination with the fifth control tube to realize the constant voltage output function. Therefore, the above-mentioned DC-DC constant voltage circuit can combine overvoltage protection and constant voltage output. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A circuit diagram of an overvoltage protection circuit in the prior art;

[0024] Figure 2 is a circuit diagram of a voltage control circuit in the prior art;

[0025] Figure 3 is a circuit diagram of a DC-DC constant voltage circuit in one embodiment;

[0026] Figure 4 FIG. 4 is a specific circuit diagram of a voltage stabilizing comparator U1 in a DC-DC constant voltage circuit according to an embodiment of the present invention.

[0027] Figure numerals: 10, DC-DC constant voltage circuit; 100, input circuit; 200, switch control circuit; 300, output circuit; R1, first resistor; R2, second resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor; R8, eighth resistor; R9, ninth resistor; R10, tenth resistor; R11, eleventh resistor; R12, twelfth resistor; R13, thirteenth resistor; R14, fourteenth resistor; R15, fifteenth resistor; RV1, sliding resistor; Q1, first control tube; Q2, second control tube; Q3, third control tube; Q4, fourth control tube; Q5, fifth control tube; C1, first capacitor; C2, second capacitor; U1, voltage regulator comparator; D1, first voltage regulator diode; D4, fourth voltage regulator diode; D5, fifth voltage regulator diode. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are given in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thoroughly and comprehensively understood.

[0029] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present disclosure. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0031] In order to better understand the technical solutions and beneficial effects of the present invention, the present invention is further described in detail below in conjunction with specific embodiments:

[0032] See also Figure 3 , which is a DC-DC constant voltage circuit 10 according to an embodiment of the present invention, includes an input circuit 100 , a switch control circuit 200 and an output circuit 300 .

[0033] The input circuit 100 is used to receive an input voltage and output it. The input terminal of the input circuit 100 is connected to the power input terminal INPUT.

[0034] The switch control circuit 200 includes an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a first control transistor Q1, a second control transistor Q2 and a third control transistor Q3. The output end of the input circuit 100 is respectively connected to the control end of the second control transistor Q2 and the first end of the tenth resistor R10, the second end of the second control transistor Q2 is connected to the second end of the tenth resistor R10, the second end of the tenth resistor R10 is grounded, the first end of the eighth resistor R8 is connected to the power input end, the second end of the eighth resistor R8 is respectively connected to the first end of the second control transistor Q2 and the control end of the first control transistor Q1, the first end of the ninth resistor R9 is respectively connected to the first end of the eighth resistor R8 and the first end of the third control transistor Q3, the second end of the ninth resistor R9 is respectively connected to the control end of the third control transistor Q3 and the first end of the first control transistor Q1, and the second end of the first control transistor Q1 is grounded.

[0035] The output circuit 300 includes a thirteenth resistor R13, a sliding resistor RV1, a first voltage-stabilizing diode D1, a fourth control tube Q4, a fifth control tube Q5 and a second capacitor C2. The second end of the third control tube Q3 is respectively connected to the first end of the fourth control tube Q4, the first end of the fifth control tube Q5 and the first end of the thirteenth resistor R13. The second end of the thirteenth resistor R13 is respectively connected to the cathode of the first voltage-stabilizing diode D1 and the control end of the fifth control tube Q5. The anode of the first voltage-stabilizing diode D1 is grounded. The second end of the fifth control tube Q5 is respectively connected to the control end of the fourth control tube Q4, the upper half end of the second capacitor C2 and the sliding adjustment end of the sliding resistor RV1. The lower half end of the second capacitor C2 is grounded. The second end of the fourth control tube Q4 is grounded through the sliding resistor RV1. The second end of the fourth control tube Q4 is used for constant voltage output.

[0036] In this embodiment, when the input voltage exceeds the threshold value set by the input circuit 100, the second control tube Q2 is turned on and grounded, so that the first control tube Q1 and the third control tube Q3 are turned off in sequence, which plays an overvoltage protection role; when the input voltage is in the normal range, the second control tube Q2 is turned off and the first control tube Q1 and the third control tube Q3 are turned on in sequence, and then the fourth control tube Q4 is turned on in coordination with the state of the fifth control tube Q5 to achieve the constant voltage output function. Therefore, the above-mentioned DC-DC constant voltage circuit 10 can combine overvoltage protection and constant voltage output.

[0037] It can be understood that the input circuit 100 includes a first resistor R1, a second resistor R2 and a voltage regulator comparator U1. Further, the voltage regulator comparator U1 is a TL431. Figure 4As shown, the first terminal 1 is the positive input terminal (R terminal), the second terminal 2 is the negative input terminal (A terminal), and the third terminal is the output terminal (K terminal). The input voltage is divided by the first resistor R1 and the second resistor R2, and the voltage of the second resistor R2 accounts for R2 / (R1+R2) of the resistor divider, that is, the R terminal of the TL431 comparator.

[0038] When the input voltage is within the normal range, the divided voltage of the second resistor R2 is lower than the reference voltage value (assuming it is 2.5V), and the output end of the voltage regulator comparator U1 outputs a high level. The high level signal passes through the control end of the second control tube Q2, so that the second control tube Q2 is not turned on. The first end of the second control tube Q2 is at a high level, so that the control end of the first control tube Q1 is at a high level, thereby turning on the first control tube Q1 and grounding it. Subsequently, the control end of the third control tube Q3 is at a low level to turn on. When the current passes through the output circuit 300, due to the action of the first voltage regulator diode D1, the control end voltage of the fifth control tube Q5 It is clamped at a fixed value, recorded as Vd. The control-end current of the fifth control tube Q5 is determined according to the relationship between the difference between the input voltage and the fixed value and the thirteenth resistor R13 to confirm the conduction state of the fifth control tube Q5. When the first voltage-stabilizing diode D1 reaches its own conduction condition to be turned on, the fifth control tube Q5 is turned on, and then the fourth control tube Q4 is also turned on. Since the voltage divider value occupied by the sliding resistor RV1 is the same as the voltage at the second end of the fifth control tube Q5, the second end of the fourth resistor outputs a constant voltage, thereby playing the role of constant voltage output, and the output voltage value can be determined by adjusting the resistance value of the sliding resistor RV1.

[0039] When the input voltage exceeds the normal range, the divided voltage of the second resistor R2 is higher than the reference voltage value, and the output end of the voltage regulator comparator U1 outputs a low level. The low level signal passes through the control end of the second control tube Q2 to turn on the second control tube Q2 and ground it. The first end of the second control tube Q2 is at a low level, which makes the control end of the first control tube Q1 at a low level, and then turns off. Subsequently, the third control tube Q3 is also turned off, and there is no voltage output in the output circuit 300, thereby playing a role of overvoltage protection.

[0040] The voltage at the output end of the voltage stabilizing comparator U1 can be stabilized by the fourth resistor R4 and the fourth voltage stabilizing diode D4 connected in parallel, so as to avoid the situation where the output voltage fluctuates greatly and causes the second control tube Q2 to be damaged.

[0041] In this embodiment, the first control tube Q1 is an NMOS tube, whose first end is a drain, whose second end is a source, and whose control end is a gate; the second control tube Q2 is a PNP transistor, whose first end is an emitter, whose second end is a collector, and whose control end is a base; the third control tube Q3 is a PMOS tube, whose first end is a source, whose second end is a drain, and whose control end is a gate; the fourth control tube Q4 is an NPN transistor, whose first end is a collector, whose second end is an emitter, and whose control end is a base; the fifth control tube Q5 is a PNP transistor, whose first end is a collector, whose second end is an emitter, and whose control end is a base.

[0042] In another embodiment, the output circuit 300 further includes a fourteenth resistor R14, and the second end of the fourth control tube Q4 is grounded through the fourteenth resistor R14. Further, the output circuit 300 further includes a first capacitor C1, and the first capacitor C1 is connected in parallel with the fourteenth resistor R14 to form a resistor-capacitor circuit, which can filter the output voltage of the second end of the fourth control tube Q4, reduce the interference of redundant signals, and ensure stable voltage output.

[0043] In one embodiment, the output circuit 300 further includes a fifteenth resistor R15, and the second end of the fourth control tube Q4 is grounded through the fifteenth resistor R15 and the sliding resistor RV1 in sequence. It can be understood that the fifteenth resistor R15 is connected in series with the sliding resistor RV1, and the second end voltage of the fourth control tube Q4, that is, the output voltage, can be confirmed by fine adjustment of the fifteenth resistor R15 and the sliding resistor RV1, that is, the constant voltage value can be adjusted by the resistance value of the fifteenth resistor R15 and the sliding resistor RV1.

[0044] In one embodiment, the output circuit 300 further includes a twelfth resistor R12, a first end of the twelfth resistor R12 is connected to the second end of the third control tube Q3, and a second end of the twelfth resistor R12 is connected to the first end of the fifth control tube Q5. It can be understood that the twelfth resistor R12 is connected in series to the first end of the fifth control tube Q5 to protect the fifth control tube Q5, avoid excessive current from breaking through the fifth control tube Q5, and ensure the normal switching state of the fifth control tube Q5.

[0045] In one embodiment, the switch control circuit 200 further includes a fifth resistor R5, a first end of the fifth resistor R5 is connected to the output end of the input circuit 100, and a second end of the fifth resistor R5 is connected to the control end of the second control tube Q2. It can be understood that the fifth resistor R5 and the tenth resistor R10 are connected in series, and the fifth resistor R5 is electrically connected to the control end of the second control tube Q2 to further protect the second control tube Q2, avoid the second control tube Q2 from being broken down, and ensure the normal switching state of the second control tube Q2. Further, at least one of the fifth resistor R5 and the tenth resistor R10 is a variable resistor. It can be understood that when one or both of the fifth resistor R5 and the tenth resistor R10 are variable resistors, the conduction condition of the second control tube Q2 can be adjusted by adjusting the resistance value of one or both of the fifth resistor R5 and the tenth resistor R10 to adapt to more models of second control tubes Q2, that is, PNP transistors.

[0046] In one embodiment, the switch control circuit 200 further includes a sixth resistor R6, and the second end of the ninth resistor R9 is connected to the first end of the first control tube Q1 through the sixth resistor R6, so that the current after passing through the ninth resistor R9 is limited, thereby further protecting the first control tube Q1 and preventing the first control tube Q1 from being broken down by excessive current.

[0047] In one embodiment, the switch control circuit 200 further includes an eleventh resistor R11, a first end of the eleventh resistor R11 is connected to the control end of the first control tube Q1, and a second end of the eleventh resistor R11 is grounded. It can be understood that the eighth resistor R8 and the eleventh resistor R11 are connected in series, and when the current passes through the eighth resistor R8 and the eleventh resistor R11, the eighth resistor R8 and the eleventh resistor R11 divide the voltage, and a voltage drop is generated in the eleventh resistor R11, and whether to turn on the first control tube Q1 is determined according to the current situation. Further, at least one of the eighth resistor R8 and the eleventh resistor R11 is a variable resistor. It can be understood that when one or both of the eighth resistor R8 and the eleventh resistor R11 are variable resistors, the conduction condition of the first control tube Q1 can be adjusted by adjusting the resistance value of one or both of the eighth resistor R8 and the eleventh resistor R11, so as to adapt to more models of the first control tube Q1, that is, NMOS tubes.

[0048] In one embodiment, the switch control circuit 200 further includes a fifth voltage stabilizing diode D5, an anode of the fifth voltage stabilizing diode D5 connected to the second end of the ninth resistor R9, and a cathode of the fifth voltage stabilizing diode D5 connected to the first end of the ninth resistor R9. It can be understood that the fifth voltage stabilizing diode D5 is connected in parallel with the ninth resistor R9, which can stabilize the voltage at the first end of the third control tube Q3, avoid voltage fluctuations that damage the third control tube Q3, and ensure the normal switching state of the third control tube Q3.

[0049] The present disclosure also provides an overvoltage protection constant voltage output device, including any of the DC-DC constant voltage circuits 10 of the above embodiments. When the overvoltage protection constant voltage output device uses the DC-DC constant voltage circuit 10, overvoltage protection and constant voltage output can be achieved simultaneously, ensuring normal operation of the product and voltage stability.

[0050] Compared with the prior art, the present invention has at least the following advantages:

[0051] When the input voltage exceeds the threshold value set by the input circuit 100, the second control tube Q2 is turned on and grounded, so that the first control tube Q1 and the third control tube Q3 are turned off in sequence, which plays an overvoltage protection role; when the input voltage is within the normal range, the second control tube Q2 is turned off and the first control tube Q1 and the third control tube Q3 are turned on in sequence, and then the fourth control tube Q4 is turned on in coordination with the fifth control tube Q5 to achieve the constant voltage output function. Therefore, the above-mentioned DC-DC constant voltage circuit 10 can combine overvoltage protection and constant voltage output.

[0052] The above-mentioned embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the disclosed patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the disclosed patent shall be subject to the attached claims.

Claims

1. A DC-DC constant voltage circuit, characterized in that: include: An input circuit, used for receiving an input voltage and outputting it, wherein an input terminal of the input circuit is connected to a power input terminal; A switch control circuit comprises an eighth resistor, a ninth resistor, a tenth resistor, a first control tube, a second control tube and a third control tube, wherein the output end of the input circuit is respectively connected to the control end of the second control tube and the first end of the tenth resistor, the second end of the second control tube is connected to the second end of the tenth resistor, the second end of the tenth resistor is grounded, the first end of the eighth resistor is connected to the power input end, the second end of the eighth resistor is respectively connected to the first end of the second control tube and the control end of the first control tube, the first end of the ninth resistor is respectively connected to the first end of the eighth resistor and the first end of the third control tube, the second end of the ninth resistor is respectively connected to the control end of the third control tube and the first end of the first control tube, and the second end of the first control tube is grounded; The output circuit includes a thirteenth resistor, a sliding resistor, a first voltage-stabilizing diode, a fourth control tube, a fifth control tube and a second capacitor. The second end of the third control tube is respectively connected to the first end of the fourth control tube, the first end of the fifth control tube and the first end of the thirteenth resistor. The second end of the thirteenth resistor is respectively connected to the cathode of the first voltage-stabilizing diode and the control end of the fifth control tube. The anode of the first voltage-stabilizing diode is grounded. The second end of the fifth control tube is respectively connected to the control end of the fourth control tube, the upper half end of the second capacitor and the sliding adjustment end of the sliding resistor. The lower half end of the second capacitor is grounded. The second end of the fourth control tube is grounded through the sliding resistor. The second end of the fourth control tube is used for constant voltage output.

2. The DC-DC constant voltage circuit according to claim 1, characterized in that: The output circuit also includes a fifteenth resistor, and the second end of the fourth control tube is grounded through the fifteenth resistor and the sliding resistor in sequence.

3. The DC-DC constant voltage circuit according to claim 1, characterized in that: The output circuit further includes a twelfth resistor, a first end of the twelfth resistor is connected to the second end of the third control tube, and a second end of the twelfth resistor is connected to the first end of the fifth control tube.

4. The DC-DC constant voltage circuit according to claim 1, characterized in that: The switch control circuit further includes a fifth resistor, a first end of the fifth resistor is connected to the output end of the input circuit, and a second end of the fifth resistor is connected to the control end of the second control tube.

5. The DC-DC constant voltage circuit according to claim 4, characterized in that: At least one of the fifth resistor and the tenth resistor is a variable resistor.

6. The DC-DC constant voltage circuit according to claim 1, characterized in that: The switch control circuit further includes a sixth resistor, and the second end of the ninth resistor is connected to the first end of the first control tube through the sixth resistor.

7. The DC-DC constant voltage circuit according to claim 1, characterized in that: The switch control circuit further includes an eleventh resistor, a first end of the eleventh resistor is connected to the control end of the first control tube, and a second end of the eleventh resistor is grounded.

8. The DC-DC constant voltage circuit according to claim 7, characterized in that: At least one of the eighth resistor and the eleventh resistor is a variable resistor.

9. The DC-DC constant voltage circuit according to claim 1, characterized in that: The switch control circuit further includes a fifth zener diode, an anode of the fifth zener diode is connected to the second end of the ninth resistor, and a cathode of the fifth zener diode is connected to the first end of the ninth resistor.

10. An overvoltage protection constant voltage output device, characterized in that: A DC-DC constant voltage circuit comprising any one of claims 1 to 9.

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