A protection circuit
Patent Information
- Application Number
- CN202522236128.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2035-10-22
AI Technical Summary
Existing Boost circuit protection circuits suffer from high conduction losses, complex structures, and low reliability when preventing reverse connection of input power and output short circuit.
The input capacitor Ci and the output filter capacitor Co are connected in parallel, and the switching transistors Q1, Q2 and Q3 are used as protection devices. Through PWM modulation control, protection barriers are formed on the input side and the output side respectively to achieve reverse connection protection and short circuit protection.
It simplifies the circuit structure, reduces component costs and control complexity, improves the stability and reliability of power conversion, and avoids circuit damage.
Smart Images
Figure CN224935357U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of power supply technology, specifically, it relates to a protection circuit. Background Technology
[0002] With the development of power electronics technology, non-isolated boost DC-DC (DCDC) converter circuits (i.e., boost circuits) are widely used in industries with stringent requirements for power conversion efficiency and circuit reliability, such as the rail and photovoltaic industries, because they can convert low input DC voltage to high output DC voltage. In these applications, boost circuits not only need to stably achieve the boost function, but also need to be equipped with protection circuits to prevent circuit failures such as reverse connection and short circuit.
[0003] To address the issue of reverse connection of the input power supply, existing technologies often employ the addition of a reverse connection protection circuit composed of diodes. While this can block reverse current, the forward voltage drop of the diodes increases the conduction loss of the circuit, reducing the overall power conversion efficiency of the Boost circuit. Alternatively, contactors or electromagnetic relays can be used as reverse connection protection switches. These devices are not only bulky and occupy circuit space, but also suffer from mechanical contact wear, leading to decreased reliability after long-term use. Furthermore, they require additional drive control circuitry, further increasing the control complexity of the circuit. Utility Model Content
[0004] The technical problem to be solved by this utility model is to overcome the shortcomings of the prior art and provide a protection circuit.
[0005] To achieve the above objectives, the technical solution of this utility model is as follows:
[0006] A protection circuit is provided at the input terminal of a Boost circuit, including an input capacitor Ci connected in parallel across the input power supply for filtering input voltage ripple, and a first protection device is provided between the positive terminal of the input power supply and the positive terminal of the output power supply of the protection circuit.
[0007] An output filter capacitor Co is connected in parallel across the output power supply terminals of the protection circuit, and a second switching transistor Q2 is connected in parallel between the input capacitor Ci and the output filter capacitor Co.
[0008] One end of the first protection device is connected to the input capacitor Ci, and the other end is connected to the energy storage inductor L. A second protection device is provided between the energy storage inductor and the positive terminal of the output power supply.
[0009] The first protection device and the energy storage inductor L are disposed between the input capacitor Ci and the switching transistor Q2;
[0010] The second protection device is located between the switching transistor Q2 and the output filter capacitor Co.
[0011] Furthermore, a second freewheeling diode is provided on the switching transistor Q2, and the current flowing in the second freewheeling diode is from the negative terminal of the power supply to the positive terminal.
[0012] Furthermore, the first protection device is a switching transistor Q1.
[0013] Furthermore, a first freewheeling diode is provided on the switching transistor Q1, and the current flowing in the first freewheeling diode is from the input power supply side to the output power supply side.
[0014] Furthermore, the second protection device is the switching transistor Q3.
[0015] Furthermore, a third freewheeling diode is provided on the switching transistor Q3, and the current flowing in the third freewheeling diode is from the output power supply side to the input power supply side.
[0016] Furthermore, the switching transistors Q1, Q2, and Q3 are all controlled by PWM modulation.
[0017] By adopting the above technical solution, the protection circuit provided by this utility model has the following beneficial effects compared with the prior art.
[0018] (1) This utility model filters out voltage ripple on the input and output sides by using the input capacitor Ci and the output filter capacitor Co respectively, stabilizes the voltage at both ends of the circuit, avoids ripple interference with the normal boost function of the Boost circuit, and improves the stability of power conversion. By setting the first protection device and the second protection device to form a protection barrier on the input side and the output side respectively, there is no need to add an independent reverse connection protection circuit or output short circuit protection contactor as in the prior art, which simplifies the overall circuit structure and reduces the complexity of the circuit and the difficulty of control.
[0019] (2) Compared with the existing technology of “using an additional anti-reverse connection circuit or contactor to achieve input anti-reverse connection”, this utility model uses the switching transistor Q1 as the first protection device, without the need to add a complex independent circuit. The input side anti-reverse connection function can be achieved with a single device, which greatly simplifies the circuit structure and reduces component cost and control complexity.
[0020] (3) By setting the switching transistor Q3 as the second protection module, this utility model can actively disconnect when the circuit detects an output short circuit (such as the output current exceeding the set value), completely cut off the short circuit current path on the output side, realize output short circuit protection, avoid circuit damage, greatly improve circuit reliability, and avoid the situation in the prior art where the freewheeling diode will still conduct short circuit current when the Boost circuit output is short-circuited, even if the control switching transistor is disconnected, which leads to circuit damage.
[0021] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings. Attached Figure Description
[0022] The accompanying drawings, as part of this utility model, are used to provide a further understanding of the present utility model. The illustrative embodiments and descriptions of the present utility model are used to explain the present utility model, but do not constitute an undue limitation of the present utility model. Obviously, the drawings described below are merely some embodiments; those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings:
[0023] Figure 1 This is a circuit diagram of the present invention;
[0024] Figure 2 This is a timing diagram of the DCM (Distributed Control Center) of the circuit of this utility model.
[0025] Figure 3 This is a timing diagram of the working BCM of the circuit of this utility model;
[0026] Figure 4 This is a timing diagram of the CCM operation of the circuit of this utility model.
[0027] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the present invention in any way, but rather to illustrate the concept of the present invention to those skilled in the art by referring to specific embodiments. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate this utility model, but are not intended to limit the scope of this utility model.
[0029] In the description of this utility model, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.
[0030] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.
[0032] Example 1
[0033] like Figures 1 to 4 As shown, the present invention provides a protection circuit, which is set at the input end of the Boost circuit and includes an input capacitor Ci connected in parallel across the input power supply for filtering input voltage ripple. A first protection device is provided between the positive terminal of the input power supply and the positive terminal of the output power supply of the protection circuit.
[0034] The output power supply of the protection circuit is connected in parallel with an output filter capacitor Co, and a second switching transistor Q2 is connected in parallel between the input capacitor Ci and the output filter capacitor Co.
[0035] One end of the first protection device is connected to the input capacitor Ci, and the other end is connected to the energy storage inductor L. A second protection device is provided between the energy storage inductor and the positive terminal of the output power supply.
[0036] The first protection device and the energy storage inductor L are positioned between the input capacitor Ci and the switching transistor Q2;
[0037] The second protection device is located between the switching transistor Q2 and the output filter capacitor Co.
[0038] The input capacitor Ci and the output filter capacitor Co respectively filter out the voltage ripple on the input and output sides, stabilize the voltage across the circuit, avoid ripple interference with the normal boost function of the Boost circuit, improve the stability of power conversion, and better meet the power supply reliability requirements of the rail and photovoltaic industries.
[0039] The first and second protection devices form protection barriers on the input and output sides, respectively. Unlike existing technologies, there is no need to add an additional independent reverse connection protection circuit or output short circuit protection contactor, which simplifies the overall circuit structure and reduces the complexity of the circuit and the difficulty of control.
[0040] In this embodiment, it is further preferred that a second freewheeling diode is provided on the switching transistor Q2, and the current flow in the second freewheeling diode is from the negative terminal of the power supply to the positive terminal.
[0041] In response to the problem in the prior art where the reverse current flows through the switching transistor's body diode and inductor and causes damage when the Boost circuit input is reverse connected, the current flow direction restriction of this freewheeling diode can block the reverse current path when reverse connected, further enhancing the reverse connection protection effect on the input side and preventing the second switching transistor Q2 and the energy storage inductor L from being damaged by reverse current surges.
[0042] When the Boost circuit is working normally (such as during the inductor discharge phase), the freewheeling diode can help achieve current freewheeling, ensuring that the energy of the energy storage inductor L can be released stably when the second switch Q2 is turned off, without affecting the normal boost timing of the Boost circuit, thus balancing protection function and circuit performance.
[0043] In this embodiment, it is further preferred that the first protection device is a switching transistor Q1. Specifically, the source of the switching transistor Q1 is connected to the positive terminal of the input power supply and one end of the input capacitor Ci, and the drain of the first switching transistor Q1 is connected to one end of the energy storage inductor L.
[0044] The other end of the energy storage inductor L is connected to the drain of the second switch Q2 and the drain of the third switch Q3, respectively.
[0045] The source of the second switch Q2 is connected to the negative terminal of the input power supply and the other end of the input capacitor Ci.
[0046] The source of the third switch Q3 is connected to one end of the output filter capacitor Co and the positive terminal of the output load, respectively. The other end of the output filter capacitor Co is connected to the negative terminal of the output load and the source of the second switch Q2.
[0047] Compared to existing technologies that use additional reverse connection protection circuits or contactors to achieve input reverse connection protection, this method uses a switching transistor Q1 as the first protection device. It eliminates the need for additional complex independent circuits and achieves input-side reverse connection protection with a single device, greatly simplifying the circuit structure and reducing component costs and control complexity.
[0048] Moreover, the switching transistor Q1 can be linked with the overall control logic of the Boost circuit, eliminating the need for an additional independent control unit, reducing line redundancy, and avoiding mechanical or conduction losses caused by components such as contactors, thereby improving the overall power conversion efficiency of the circuit.
[0049] A first freewheeling diode is provided on the switching transistor Q1. The current in the first freewheeling diode flows from the input power supply side to the output power supply side.
[0050] During normal operation, the current flow of the freewheeling diode is consistent with the forward current path from the input to the output of the Boost circuit. It can assist the switch Q1 in conducting forward current. Especially in scenarios where the circuit operates in discontinuous mode (DCM) and the current fluctuates greatly, it can prevent the current interruption caused by the conduction delay of the switch Q1 and ensure the continuity of power conversion.
[0051] When the input side is reverse connected, the reverse cutoff characteristic of the freewheeling diode can further block the reverse current, completely preventing the reverse current from flowing through the energy storage inductor L and subsequent components, solving the problem of circuit damage caused by input reverse connection in the prior art, and protecting the switching transistor Q1 itself from reverse breakdown.
[0052] In this embodiment, the second protection device is further preferably a switching transistor Q3.
[0053] In this embodiment, a further preferred embodiment includes a third freewheeling diode on the switching transistor Q3, with the current flowing from the output power supply side to the input power supply side. The advantages are similar to those of the switching transistors Q1 and Q2 described above, and will not be elaborated further here.
[0054] Example 2
[0055] The difference from Embodiment 1 is that, in this embodiment, the switching transistors Q1, Q2, and Q3 are all controlled by PWM modulation.
[0056] PWM modulation can flexibly adjust the on / off timing of each switch according to the current input and output state of the Boost circuit (such as input voltage and output load requirements), adapting to the discontinuous mode of the circuit. When the circuit has faults such as input reverse connection or output short circuit, PWM modulation can quickly respond to the fault signal and control the corresponding switch in time (such as Q1 being cut off to prevent reverse connection and Q3 being cut off to cut off short circuit current). Compared with the traditional discrete control method, the fault response speed is faster, further reducing the risk of fault damage to the circuit. Precise PWM timing control can reduce the switching loss and conduction loss of the switch, avoiding energy waste caused by improper control timing.
[0057] This application mentions another basic Boost protection circuit. Based on the circuit of this application, the switching transistor Q1 is removed and the connection directions of the source and drain of the switching transistor Q3 are interchanged. Some functions can also be achieved. However, when the input side is reversed, the reverse current flows through the freewheeling diode of the switching transistor Q2 and the energy storage inductor L, which damages the circuit.
[0058] When the output is short-circuited, the circuit detects that the output current is greater than the set value, causing the switching transistors Q2 and Q3 to turn off. Due to the freewheeling diode of the switching transistor Q3, the short-circuit current can still flow through the freewheeling diode to the output side, causing circuit damage.
[0059] When the input side is reverse-connected, the protection circuit of this application allows the reverse current to flow through either switch Q2 or switch Q3. However, due to the function of switch Q1 (PMOS), the current cannot flow through the body diode of switch Q1. This effectively prevents reverse connection of the input.
[0060] When the output is short-circuited, the circuit detects that the output current exceeds the set value, causing switches Q2 and Q3 to turn off, thus putting the circuit into a protection state. However, in a basic Boost protection circuit, even if the switches are turned off during an output short circuit, the short-circuit current can still flow through the freewheeling diode to the output side, potentially damaging the circuit.
[0061] Based on the input and output conditions, the operating state of the protection circuit in this application can be divided into three states: discontinuous mode (DCM), critical mode (BCM), and continuous mode (CCM). Compared with the basic Boost protection circuit, it is necessary to control the added Q1 on the input side, especially in the discontinuous mode (DCM) operating state, the difference is more obvious.
[0062] like Figure 2 As shown, it is assumed that the switching transistors Q1, Q2, and Q3, the input capacitor Ci, the output filter capacitor Co, and the energy storage inductor L are all ideal devices.
[0063] At time T0: Switches Q1 and Q2 are turned on simultaneously, switch Q3 is turned off, and the current in inductor L is 0.
[0064] Between time T0 and T1: Switches Q1 and Q2 remain on, while switch Q3 remains off. The current IL in the energy storage inductor L increases linearly from 0. At time T1, the current IL in the energy storage inductor L reaches its maximum value ILPK. At this point, switch Q2 is off, switch Q1 remains on, and switch Q3 is on.
[0065] Between time points T1 and T2: Switches Q2 and Q3 remain on, while switch Q1 remains off. The current IL in the energy storage inductor L decreases linearly from its maximum value ILPK. At time T2, the current IL in the energy storage inductor L drops to 0. At this point, switches Q1 and Q3 are off, while switch Q2 remains off.
[0066] Time T2-T3: During this period, switching transistors Q1, Q2, and Q3 remain off until the start of the next cycle.
[0067] like Figure 3 and Figure 4As shown, when the circuit operates in BCM and CCM modes, switch Q1 remains on, and the operating timing of switches Q2 and Q3 is the same as that of the basic Boost protection circuit without switch Q1.
[0068] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to preferred embodiments, it is not intended to limit the present utility model. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present utility model. The implementation schemes in the above embodiments can also be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall still fall within the scope of the present utility model.
Claims
1. A protection circuit, disposed at the input terminal of a Boost circuit, characterized in that: The protection circuit includes an input capacitor Ci connected in parallel across the input power supply to filter out input voltage ripple, and a first protection device is provided between the positive terminal of the input power supply and the positive terminal of the output power supply. An output filter capacitor Co is connected in parallel across the output power supply terminals of the protection circuit, and a second switching transistor Q2 is connected in parallel between the input capacitor Ci and the output filter capacitor Co. One end of the first protection device is connected to the input capacitor Ci, and the other end is connected to the energy storage inductor L. A second protection device is provided between the energy storage inductor and the positive terminal of the output power supply. The first protection device and the energy storage inductor L are disposed between the input capacitor Ci and the switching transistor Q2; The second protection device is located between the switching transistor Q2 and the output filter capacitor Co.
2. The protection circuit according to claim 1, characterized in that: The switching transistor Q2 is provided with a second freewheeling diode, and the current in the second freewheeling diode flows from the negative terminal of the power supply to the positive terminal.
3. A protection circuit according to claim 1 or 2, characterized in that: The first protection device is the switching transistor Q1.
4. A protection circuit according to claim 3, characterized in that: The switching transistor Q1 is provided with a first freewheeling diode, and the current in the first freewheeling diode flows from the input power supply side to the output power supply side.
5. A protection circuit according to claim 3, characterized in that: The second protection device is the switching transistor Q3.
6. A protection circuit according to claim 5, characterized in that: A third freewheeling diode is provided on the switching transistor Q3, and the current flowing in the third freewheeling diode is from the output power supply side to the input power supply side.
7. A protection circuit according to claim 5, characterized in that: The switching transistors Q1, Q2, and Q3 are all controlled by PWM modulation.