Buck-boost protection circuit

Abstract

The utility model relates to a buck-boost protection circuit comprising a low voltage side; a high pressure side; the boost-buck circuit is electrically connected with the high-voltage side and the low-voltage side, and a negative electrode of the high-voltage side is electrically connected with a negative electrode of the low-voltage side; the bypass circuit comprises a relay and a diode, the relay is electrically connected with the positive electrode of the low-voltage side and the positive electrode of the diode, and the negative electrode of the diode is electrically connected with the positive electrode of the high-voltage side; and the control module controls the on-off of the relay. According to the utility model, the relay and the diode are used as bypass circuits to replace conventional low-resistance power type resistors, the working time of the relay is shorter, the situation of long-time overlarge current is avoided, the model selection difficulty of the relay is effectively reduced, and the cost of the diode is lower, so that the use cost can be reduced to a certain extent; when the relay is stuck and cannot be disconnected, the overpower phenomenon of the device does not exist, the damage of other components caused by abnormal work of the relay can be avoided, the fault rate is reduced, and the maintenance cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of protection circuits, in particular to a step-up and step-down protection circuit. Background Art

[0002] The buck-boost circuit is a common topology in the photovoltaic energy storage industry. In this circuit, transistors are used as switches to increase switching frequency, thereby improving product efficiency and reducing temperature rise. However, the internal diode of a transistor has a weak ability to withstand current surges. When a voltage without ramp-up is applied to the low-voltage side, current flows through the inductor and the transistor's body diode to the high-voltage side. At this point, the current in the inductor is very large, potentially reaching the KA level, which can easily break down the transistor's body diode, causing it to short-circuit.

[0003] Although there is currently a commonly used solution to protect transistors in buck-boost circuits, this form of protection limits the inrush current of the transistor through a power resistor without a ramp-up voltage to protect the transistor. However, the requirements for the power resistor and relay are high. The resistor needs to have sufficient power and a small enough resistance value, but not too small, which will cause circuit failure. The reliability requirements for the relay are high. If the relay cannot close normally, the current will flow through the resistor when the transistor is working, and the resistor will experience overpower, causing the resistor to burn out, and increasing costs.

[0004] Therefore, a buck-boost protection circuit is needed that does not require the addition of power resistors, can reduce the difficulty of component selection, and reduces the cost of use. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the utility model provides a step-up / step-down protection circuit.

[0006] The technical solution of this utility model is as follows:

[0007] A buck-boost protection circuit, comprising:

[0008] Low-voltage side, the voltage of the low-voltage side is Ui;

[0009] High voltage side, the voltage of the high voltage side is Uo;

[0010] a buck-boost circuit, the buck-boost circuit electrically connecting the high-voltage side and the low-voltage side, wherein the negative electrode of the high-voltage side is electrically connected to the negative electrode of the low-voltage side;

[0011] A bypass circuit, comprising a relay K1 and a diode D1, wherein the relay K1 is electrically connected to the positive electrode of the low-voltage side and the anode of the diode D1, and the cathode of the diode D1 is electrically connected to the positive electrode of the high-voltage side;

[0012] A control module controls the on and off of the relay K1.

[0013] As a further improvement of the present invention, the control module supplies power to the relay K1 , and the relay K1 is a power-type normally closed relay.

[0014] As a further improvement of the present invention, the operating voltage of the relay K1 is 12V.

[0015] As a further improvement of the present invention, the relay K1 includes a power input end, a transistor, an electromagnet, a ground end and a switch, the power input end is electrically connected to the control module, the switch is electrically connected to the positive pole of the low-voltage side and the anode of the diode D1, the electromagnet cooperates with the switch, the power input end is electrically connected to the first end of the electromagnet and the base of the transistor respectively, the second end of the electromagnet is electrically connected to the collector of the transistor, and the emitter of the transistor is electrically connected to the ground end.

[0016] As a further improvement of the present invention, a voltage stabilizing diode is provided between the power input terminal and the base.

[0017] As a further improvement of the present invention, a first resistor is provided between the voltage stabilizing diode and the base, and a second resistor is provided between the base and the emitter.

[0018] As a further improvement of the present invention, the buck-boost circuit includes an inductor L, a switch tube Q1 and a switch tube Q2, the first end of the inductor L is electrically connected to the positive pole of the low-voltage side, the second end of the inductor L is electrically connected to the first end of the switch tube Q1, the second end of the switch tube Q1 is electrically connected to the positive pole of the high-voltage side, the first end of the switch tube Q2 is electrically connected to the midpoint of the inductor L and the switch tube Q1, and the second end of the switch tube Q2 is electrically connected to the negative pole of the low-voltage side.

[0019] As a further improvement of the present invention, the control module is electrically connected to the switch tube Q1 and the switch tube Q2 respectively and controls the switch tube Q1 and the switch tube Q2.

[0020] As a further improvement of the present invention, the buck-boost protection circuit further includes a sampling module, which collects the voltage Ui on the low-voltage side, the current Ii on the low-voltage side, and the voltage Uo on the high-voltage side.

[0021] As a further improvement of the present invention, a voltage-stabilizing capacitor C1 is connected in parallel at both ends of the high-voltage side.

[0022] According to the utility model of the above solution, the beneficial effects of the utility model are:

[0023] The relay K1 of the present invention has a shorter working time and does not have a long-term excessive current situation, which effectively reduces the difficulty of selecting the relay K1. Secondly, the cost of the diode D1 is relatively low, which can reduce the cost of use to a certain extent. In addition, when the relay K1 is stuck and cannot be disconnected, there will be no device overpower phenomenon, and there is no need to add a new voltage sampling circuit to determine whether the relay K1 is stuck. The Ui, Uo and Ii sampling values ​​can be used to determine whether the relay K1 is stuck and thus stop working. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural diagram of the utility model;

[0025] Figure 2 This is a schematic diagram of the structure of the closed relay of the utility model;

[0026] Figure 3 It is a schematic structural diagram of the utility model when the relay is disconnected. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely to facilitate the description of this utility model and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] See also Figure 1 The utility model provides a step-up / step-down protection circuit, comprising:

[0031] Low voltage side, the voltage on the low voltage side is Ui;

[0032] On the high-voltage side, the voltage on the high-voltage side is Uo;

[0033] A buck-boost circuit, the buck-boost circuit electrically connecting the high-voltage side and the low-voltage side, wherein the negative electrode of the high-voltage side is electrically connected to the negative electrode of the low-voltage side;

[0034] A bypass circuit includes a relay K1 and a diode D1. The relay K1 is electrically connected to the positive electrode of the low-voltage side and the anode of the diode D1. The cathode of the diode D1 is electrically connected to the positive electrode of the high-voltage side.

[0035] Control module: The control module controls the on and off of relay K1.

[0036] The utility model adopts relay K1 and diode D1 as a bypass circuit to replace the conventional low-resistance power resistor. The working time of relay K1 is short, and there is no long-term excessive current situation, which effectively reduces the difficulty of selecting relay K1. Secondly, compared with the low-resistance power resistor, the cost of diode D1 is lower, which can reduce the cost of use to a certain extent. In addition, when relay K1 sticks and cannot be disconnected, there will be no device overpower phenomenon, which can avoid damage to other components due to abnormal operation of relay K1, reduce the failure rate and reduce maintenance costs.

[0037] As an embodiment of the present utility model, the buck-boost circuit includes an inductor L, a switch tube Q1 and a switch tube Q2, the first end of the inductor L is electrically connected to the positive pole of the low-voltage side, the second end of the inductor L is electrically connected to the first end of the switch tube Q1, the second end of the switch tube Q1 is electrically connected to the positive pole of the high-voltage side, the first end of the switch tube Q2 is electrically connected to the midpoint of the inductor L and the switch tube Q1, and the second end of the switch tube Q2 is electrically connected to the negative pole of the low-voltage side.

[0038] As an embodiment of the present invention, the control module is electrically connected to the switch tube Q1 and the switch tube Q2 respectively and controls the switch tube Q1 and the switch tube Q2. The switch tube Q1, the switch tube Q2 and the relay K1 are controlled by the same control module, which can effectively reduce the number of control modules and reduce the use cost to a certain extent. At the same time, the control modules of the switch tube Q1, the switch tube Q2 and the relay K1 are integrated together, which can effectively improve the control module's management and control capabilities of the switch tube Q1, the switch tube Q2 and the relay K1, improve the coordination and cooperation capabilities between the switch tube Q1, the switch tube Q2 and the relay K1, avoid unnecessary influence on each other's work, and improve the stability and reliability of the work.

[0039] As an embodiment of the present invention, the control module supplies power to the relay K1, which is a power type normally closed relay. Preferably, the operating voltage of the relay K1 is 12V. Of course, a relay K1 with an appropriate operating voltage can also be selected according to specific working requirements. The working state of the relay K1 is as follows:

[0040] See also Figure 2 , when the control module is in the power-off state: the control module cannot supply power to relay K1, so relay K1 is in the normally closed state, that is, the bypass circuit is turned on;

[0041] See also Figure 3 , when the control module is in normal operation: the control module normally supplies power to relay K1, therefore, relay K1 is in the disconnected state, that is, the bypass circuit is disconnected.

[0042] Initially, the control module is powered off, relay K1 is normally closed, and the bypass circuit is conducting. When a voltage without ramp-up is applied to the low-voltage side, an inrush current occurs. The contact impedance of relay K1 is low, typically in the milliohm (milliohm) range, and the forward voltage drop of diode D1 is typically 1-2V. At this point, the voltage applied to the low-voltage side is greater than the voltage on the high-voltage side, satisfying the conduction condition for diode D1. Furthermore, the impedance of the bypass circuit is much lower than that of the main power circuit. Therefore, the current I1 flowing through the bypass circuit is much greater than the current I2 flowing through inductor L and switch Q1. Most of the inrush current flows through the bypass circuit, reducing the inrush current I2 flowing through switch Q1, thereby protecting switch Q1 from breakdown by the inrush current.

[0043] When the surge current is eliminated, the control module is in normal working state and supplies power to relay K1. After receiving power, relay K1 is disconnected, so that the bypass circuit is disconnected. The current Ii output from the low-voltage side flows through the inductor L and the switch tube Q1, that is, Ii=I2, and normal operation is performed.

[0044] As an embodiment of the present invention, the relay K1 includes a power input terminal, a transistor, an electromagnet, a ground terminal, and a switch. The power input terminal is electrically connected to the control module, the switch is electrically connected to the positive electrode of the low-voltage side and the anode of the diode D1, the electromagnet cooperates with the switch, the power input terminal is electrically connected to the first end of the electromagnet and the base of the transistor, the second end of the electromagnet is electrically connected to the collector of the transistor, and the emitter of the transistor is electrically connected to the ground terminal. The working state is as follows:

[0045] When the power input terminal is not energized: the relay K1 is in a non-working state as a whole, that is, the transistor is not conducting, there is no voltage difference across the electromagnet, the switch is closed, and the bypass circuit is conducting;

[0046] When the power input terminal is energized: the relay K1 is in the working state as a whole, that is, the base voltage of the transistor is greater than the emitter voltage, which meets the conduction condition of the transistor. There is a voltage difference at both ends of the electromagnet and a magnetic field is generated, causing the switch to operate and disconnect, and the bypass circuit is disconnected.

[0047] As an embodiment of the present invention, a voltage stabilizing diode is provided between the power input terminal and the base, so that the voltage of the transistor base can be stable, thereby improving the working stability of the transistor and further achieving the working stability of the relay K1.

[0048] As an embodiment of the present utility model, a first resistor is provided between the voltage-stabilizing diode and the base, and a second resistor is provided between the base and the emitter. The voltage drop of the first resistor and the second resistor can effectively reduce the voltage on the base of the transistor, thereby protecting the transistor. At the same time, it can also ensure that the base voltage of the transistor is greater than the emitter voltage, thereby ensuring that the transistor can be turned on normally, further improving the working stability of the relay K1.

[0049] As an embodiment of the present invention, the buck-boost protection circuit further includes a sampling module, which collects the voltage Ui on the low-voltage side, the current Ii on the low-voltage side, and the voltage Uo on the high-voltage side. The sampling module feeds the sampling results back to the control module. Considering that the contact impedance of the relay K1 is extremely small, generally below 100mΩ, the current Ii on the low-voltage side is 10A, according to the formula U=IR, the voltage difference across the relay K1 is ≤10A*100mΩ=1V, considering the low-voltage side voltage Ui and the high-voltage side voltage Uo The difference is small and there is a certain error. Therefore, if the low-voltage side current Ii ≥ 10A and the voltage difference between the low-voltage side and the high-voltage side |Ui-Uo|> 5V, the relay K1 is not stuck. If the voltage difference between the low-voltage side and the high-voltage side |Ui-Uo| ≤ 5V, the relay K1 is in a stuck state, the control module alarms and stops working. The utility model does not need to add a new voltage sampling circuit to determine whether the relay K1 is stuck. The sampling values ​​of Ui, Uo and Ii can be used to determine whether the relay K1 is stuck and thus stop working.

[0050] As an embodiment of the present invention, a voltage-stabilizing capacitor C1 is connected in parallel at both ends of the high-voltage side, which can stabilize the voltage Uo on the high-voltage side and improve the overall working stability.

[0051] In summary, the utility model provides a buck-boost protection circuit, which adopts relay K1 and diode D1 as a bypass circuit instead of a conventional low-resistance power resistor. The working time of relay K1 is short, and there is no long-term excessive current situation, which effectively reduces the difficulty of selecting relay K1. Secondly, compared with the low-resistance power resistor, the cost of diode D1 is lower, which can reduce the cost of use to a certain extent. In addition, when relay K1 is stuck and cannot be disconnected, there will be no device overpower phenomenon, which can avoid damage to other components due to abnormal operation of relay K1, reduce the failure rate and reduce maintenance costs; there is no need to add a new voltage sampling circuit to determine whether relay K1 is stuck, and the Ui, Uo and Ii sampling values ​​can be used to determine whether relay K1 is stuck and stop working.

[0052] It should be emphasized that the above are only preferred embodiments of the present invention and do not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A buck-boost protection circuit, characterized in that: include: Low-voltage side, the voltage of the low-voltage side is Ui; High voltage side, the voltage of the high voltage side is Uo; a buck-boost circuit, the buck-boost circuit electrically connecting the high-voltage side and the low-voltage side, wherein the negative electrode of the high-voltage side is electrically connected to the negative electrode of the low-voltage side; A bypass circuit, comprising a relay K1 and a diode D1, wherein the relay K1 is electrically connected to the positive electrode of the low-voltage side and the anode of the diode D1, and the cathode of the diode D1 is electrically connected to the positive electrode of the high-voltage side; A control module controls the on and off of the relay K1.

2. The buck-boost protection circuit according to claim 1, wherein: The control module supplies power to the relay K1 , which is a power-type normally closed relay.

3. The buck-boost protection circuit according to claim 2, wherein: The operating voltage of the relay K1 is 12V.

4. The buck-boost protection circuit according to claim 3, wherein: The relay K1 includes a power input end, a transistor, an electromagnet, a ground end and a switch. The power input end is electrically connected to the control module, the switch is electrically connected to the positive pole of the low-voltage side and the anode of the diode D1, the electromagnet cooperates with the switch, the power input end is electrically connected to the first end of the electromagnet and the base of the transistor respectively, the second end of the electromagnet is electrically connected to the collector of the transistor, and the emitter of the transistor is electrically connected to the ground end.

5. The buck-boost protection circuit according to claim 4, characterized in that: A voltage stabilizing diode is provided between the power input terminal and the base.

6. The buck-boost protection circuit according to claim 5, characterized in that: A first resistor is provided between the voltage stabilizing diode and the base, and a second resistor is provided between the base and the emitter.

7. The buck-boost protection circuit according to claim 1, wherein: The buck-boost circuit includes an inductor L, a switch tube Q1, and a switch tube Q2. The first end of the inductor L is electrically connected to the positive electrode of the low-voltage side, the second end of the inductor L is electrically connected to the first end of the switch tube Q1, the second end of the switch tube Q1 is electrically connected to the positive electrode of the high-voltage side, the first end of the switch tube Q2 is electrically connected to the midpoint between the inductor L and the switch tube Q1, and the second end of the switch tube Q2 is electrically connected to the negative electrode of the low-voltage side.

8. The buck-boost protection circuit according to claim 7, wherein: The control module is electrically connected to the switch tube Q1 and the switch tube Q2 respectively and controls the switch tube Q1 and the switch tube Q2.

9. The buck-boost protection circuit according to claim 1, wherein: The buck-boost protection circuit further includes a sampling module, which collects the voltage Ui on the low-voltage side, the current Ii on the low-voltage side, and the voltage Uo on the high-voltage side.

10. The buck-boost protection circuit according to claim 1, wherein: The two ends of the high-voltage side are connected in parallel with a voltage-stabilizing capacitor C1.

Images