Electrolytic capacitor protection circuit and electric tool

Abstract

The utility model discloses an electrolytic capacitor protection circuit and an electric tool, and relates to the field of electric tools, the electrolytic capacitor protection circuit comprises a commercial power supply module, a current power output module and a control unit; the current power output module comprises a switch unit; the mains supply module, the switch unit and the electrolytic capacitor are sequentially connected; the control unit is connected with the switch unit; the control unit is also connected with the commercial power supply module; and the control unit is used for controlling the switch unit to disconnect the circuit between the commercial power supply module and the electrolytic capacitor when the output voltage of the commercial power supply module is detected to be higher than the preset voltage. The electrolytic capacitor can be effectively protected, so that the alternating-current electric tool is protected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric tools, in particular to an electrolytic capacitor protection circuit and an electric tool. BACKGROUND

[0002] The electrolytic capacitor plays a crucial role in the AC electric tool. It can be used for filtering. After the AC power is converted into DC power in the power supply circuit of the electric tool, the output DC voltage often has ripple. The electrolytic capacitor can filter these ripples to make the output DC voltage smoother. For example, in the motor drive circuit of the electric tool, the smooth DC voltage can ensure the stable operation of the motor and reduce the jitter and noise of the motor, just like providing a stable "energy pool" for the motor to ensure that the motor can continuously and stably obtain energy, so that the AC electric tool can operate stably.

[0003] However, the electrolytic capacitor in the AC electric tool generally has a fixed withstand voltage. When the input voltage of the AC electric tool is greater than the withstand voltage, the electrolytic capacitor will be overvoltage failure, thereby causing the AC electric tool to malfunction. CONTENT OF THE INVENTION

[0004] The purpose of the present application is to provide an electrolytic capacitor protection circuit and an electric tool, which can effectively prevent the electrolytic capacitor from overvoltage failure.

[0005] To achieve the above purpose, the present application provides the following solutions:

[0006] In a first aspect, the present application provides an electrolytic capacitor protection circuit, which comprises:

[0007] a commercial power supply module, a current power output module and a control unit;

[0008] The current power output module comprises a switching unit;

[0009] The commercial power supply module, the switching unit and the electrolytic capacitor are connected in sequence;

[0010] The control unit is connected with the switching unit;

[0011] The control unit is also connected with the commercial power supply module;

[0012] The control unit is configured to control the switching unit to disconnect the circuit between the commercial power supply module and the electrolytic capacitor when detecting that the output voltage of the commercial power supply module is higher than a preset voltage;

[0013] The current power output module further comprises a rectifier bridge and a relay unit;

[0014] The switch unit comprises a first resistor and a first switch;

[0015] The mains supply module, the rectifier bridge, the first resistor, the first switch and the electrolytic capacitor are connected in sequence.

[0016] The relay unit is connected with the rectifier bridge and the electrolytic capacitor respectively.

[0017] The control unit is connected with the relay unit, the first switch and the mains supply module respectively.

[0018] The relay unit comprises a first relay and a first diode.

[0019] The first switch comprises a first transistor.

[0020] A first output end of the mains supply module is connected with a first input end of the rectifier bridge.

[0021] A second output end of the mains supply module is connected with a second input end of the rectifier bridge.

[0022] A positive output end of the rectifier bridge is connected with a first pin of the control unit.

[0023] One end of the electrolytic capacitor is connected in a circuit between the positive output end of the rectifier bridge and the first pin of the control unit, and the other end of the electrolytic capacitor is connected with one end of the first resistor.

[0024] A second pin of the control unit, a third end of the first transistor, a first contact terminal of the first relay, a first coil terminal of the first relay and an anode of the first diode are all connected with a negative output end of the rectifier bridge.

[0025] A second coil terminal of the first relay is connected with a third pin of the control unit, and a second contact terminal of the first relay is connected in a circuit between the other end of the electrolytic capacitor and one end of the first resistor.

[0026] A cathode of the first diode is connected in a circuit between the second coil terminal of the first relay and the third pin of the control unit.

[0027] A first end of the first transistor is connected with a fourth pin of the control unit, and a second end of the first transistor is connected with the other end of the first resistor.

[0028] In a second aspect, the application provides an electric tool comprising the electrolytic capacitor protection circuit as described in the first aspect.

[0029] According to the specific embodiments provided in the present application, the present application discloses the following technical effects:

[0030] The present application provides an electrolytic capacitor protection circuit and a power tool. The electrolytic capacitor protection circuit comprises: a mains supply module, a current power output module and a control unit; the current power output module comprises: a switching unit; the mains supply module, the switching unit and the electrolytic capacitor are connected in sequence; the control unit is connected with the switching unit; the control unit is also connected with the mains supply module; the control unit is used for controlling the switching unit to disconnect the circuit between the mains supply module and the electrolytic capacitor when detecting that the output voltage of the mains supply module is higher than a preset voltage. The preset voltage can be determined according to the withstand voltage of the electrolytic capacitor. When the control unit detects that the output voltage of the mains supply module is greater than the preset voltage, it is determined that the voltage connected at this time is too high and greater than the withstand voltage of the electrolytic capacitor. The switching unit is controlled to disconnect the circuit between the mains supply module and the electrolytic capacitor to avoid charging the electrolytic capacitor, thereby protecting the electrolytic capacitor and avoiding damage to the alternating current power tool. When it is detected that the output voltage of the mains supply module meets the preset voltage, it is determined that the voltage connected at this time is normal, that is, it meets the withstand voltage of the electrolytic capacitor. The switching unit is controlled to connect the circuit between the mains supply module and the electrolytic capacitor to charge the electrolytic capacitor, so that the alternating current power tool can be used normally. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0032] Figure 1 is a schematic diagram of an electrolytic capacitor protection circuit according to an exemplary embodiment Figure 1 ;

[0033] Figure 2 is a schematic diagram of an electrolytic capacitor protection circuit according to an exemplary embodiment Figure 2 ;

[0034] Figure 3 is a schematic diagram of an electrolytic capacitor protection circuit according to an exemplary embodiment Figure 3 ;

[0035] Figure 4 is a schematic diagram of an electrolytic capacitor protection circuit according to an exemplary embodiment Figure 4 ;

[0036] Figure 5 is a schematic diagram of an electrolytic capacitor protection circuit according to an exemplary embodimentFigure 5

[0037] Figure 6 is a schematic diagram of an electrolytic capacitor protection circuit according to an exemplary embodiment Figure 6

[0038] Figure 7 is a schematic diagram of an electrolytic capacitor protection circuit according to an exemplary embodiment Figure 7

[0039] Figure 8 is a schematic diagram of an electrolytic capacitor protection circuit according to an exemplary embodiment Figure 8

[0040] BRIEF DESCRIPTION OF DRAWINGS

[0041] 1 - mains supply module; 11 - fifth diode; 12 - first voltage dividing resistor; 13 - second voltage dividing resistor; 14 - third voltage dividing resistor; 15 - filter capacitor; 2 - current power output module; 21 - rectifier bridge; 22 - relay unit; 221 - first relay; 222 - first diode; 223 - second relay; 224 - second diode; 225 - third relay; 226 - third diode; 23 - switch unit; 231 - first resistor; 232 - first switch; 2321 - first transistor; 2322 - thyristor; 2323 - first optocoupler; 2324 - second resistor; 2325 - third resistor; 233 - second switch; 2331 - bidirectional thyristor; 2332 - second optocoupler; 234 - fourth resistor; 235 - fifth resistor; 236 - sixth resistor; 3 - electrolytic capacitor; 4 - control unit; 41 - first pin; 42 - second pin; 43 - third pin; 44 - fourth pin; 45 - voltage sampling pin; 5 - fourth diode. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work, belong to the protection scope of the present application.

[0043] The above purposes, features and advantages of the present application will be more apparent and easy to understand. The present application will be further described in detail below with reference to the drawings and specific embodiments.

[0044] Figure 1 is a schematic diagram of an electrolytic capacitor protection circuit according to an exemplary embodiment, as shown in Figure 1 the electrolytic capacitor protection circuit comprises: ​​​​

[0045] The AC power supply module 1, the current power output module 2 and the control unit 4;

[0046] The current power output module 2 comprises a switching unit 23.

[0047] The AC power supply module 1, the switching unit 23 and the electrolytic capacitor 3 are sequentially connected.

[0048] The control unit 4 is connected with the current power output module 2.

[0049] The control unit 4 is also connected with the AC power supply module 1.

[0050] The control unit 4 is configured to control the switching unit 23 to disconnect the circuit between the AC power supply module 1 and the electrolytic capacitor 3 when it is detected that the output voltage of the AC power supply module 1 is higher than a preset voltage.

[0051] The preset voltage can be determined according to the withstand voltage of the electrolytic capacitor 3.

[0052] AC power tools generally use AC 220V power supply, but when used in complex power supply environments such as factories and construction sites, AC 220V power tools are occasionally inserted into AC 380V power supply by mistake, which may cause the electrolytic capacitor 3 in the AC power tool to be overvoltage and fail, and further cause the AC power tool to be damaged. Therefore, it is hoped that the tool can trigger the electrolytic capacitor 3 protection when the user misuses the power supply, so as to avoid damage to the AC power tool. The electrolytic capacitor protection circuit in the present disclosure can well protect the electrolytic capacitor 3. The control unit 4 determines whether to charge the electrolytic capacitor 3 based on the detected output voltage of the AC power supply module 1. When it is detected that the output voltage of the AC power supply module 1 is greater than the preset voltage, it is determined that the voltage connected at this time is too high and greater than the withstand voltage of the electrolytic capacitor 3. The switching unit 23 is controlled to disconnect the circuit between the AC power supply module 1 and the electrolytic capacitor 3 to avoid charging the electrolytic capacitor 3, thereby protecting the electrolytic capacitor 3 and avoiding damage to the AC power tool. When it is detected that the output voltage of the AC power supply module 1 meets the preset voltage, it is determined that the voltage connected at this time is normal, i.e., it meets the withstand voltage of the electrolytic capacitor 3. The switching unit 23 is controlled to connect the circuit between the AC power supply module 1 and the electrolytic capacitor 3 to charge the electrolytic capacitor 3, so as to normally use the AC power tool.

[0053] In the present disclosure, the control unit 4 can adopt an existing chip, such as NM1200, LKS32MC07X, etc.

[0054] The functions of the control unit 4 can also be implemented by a circuit. For example, the control unit 4 is specifically a comparator, one end of which is connected to the output voltage end of the mains supply module 1, and the other end inputs a preset voltage, and the output end of the comparator is connected to the switch unit 23. In this way, when the output voltage of the mains supply module 1 is higher than the preset voltage, the comparator outputs a high level, and when the output voltage of the mains supply module 1 is lower than the preset voltage, the comparator outputs a low level. The high level output by the comparator can control the conduction of the switch unit 23, and the low level output by the comparator can control the turn-off of the switch unit 23.

[0055] As shown in Figure 2 , in the present disclosure, the current power output module 2 further comprises a rectifier bridge 21 and a relay unit 22.

[0056] The rectifier bridge 21 has two positional relationships with the relay unit 22 and the switch unit 23. One is that the rectifier bridge 21 is located before the relay unit 22 and the switch unit 23, and the other is that the rectifier bridge 21 is located after the relay unit 22 and the switch unit 23. Each scheme will be described in detail below.

[0057] The first scheme: the rectifier bridge 21 is located before the relay unit 22 and the switch unit 23.

[0058] Figure 3 The electrolytic capacitor protection circuit shown in the figure is according to an exemplary embodiment. As shown in Figure 3 , the switch unit 23 in the electrolytic capacitor protection circuit comprises a first resistor 231 and a first switch 232.

[0059] The mains supply module 1, the rectifier bridge 21, the first resistor 231, the first switch 232 and the electrolytic capacitor 3 are connected in sequence;

[0060] The relay unit 22 is connected to the rectifier bridge 21 and the electrolytic capacitor 3, respectively;

[0061] The control unit 4 is connected to the relay unit 22, the first switch 232 and the mains supply module 1, respectively.

[0062] The rectifier bridge 21 is a semiconductor device that converts alternating current into direct current, which is mainly composed of four diodes. These diodes are usually combined together in a bridge connection mode. This structure can utilize the unidirectional conductivity of diodes to make the positive and negative half cycles of alternating current pass through different paths, and finally obtain direct current at the output end.

[0063] The working principle of the rectifier bridge 21 is as follows: in the positive half cycle of the alternating input voltage, assuming that the upper end of the alternating power supply is positive and the lower end is negative. At this time, two diodes in the rectifier bridge 21 (the diode between the upper end of the alternating power supply and the positive end of the direct current output, and the diode between the lower end of the alternating power supply and the negative end of the direct current output) are in a forward conducting state, and the current flows from the upper end of the alternating power supply to the positive end of the direct current output through the conducting diode, and then returns to the lower end of the alternating power supply through the other conducting diode, so that the positive half cycle of the alternating current is converted into a direct current output. In the negative half cycle of the alternating input voltage, the lower end of the alternating power supply becomes positive and the upper end becomes negative. At this time, the other two diodes (the diode between the lower end of the alternating power supply and the positive end of the direct current output, and the diode between the upper end of the alternating power supply and the negative end of the direct current output) are conducting, the current direction changes, but the same is from the positive end of the direct current output, and then returns to the negative end of the direct current output after passing through the load, thereby converting the negative half cycle of the alternating current into a direct current of the same direction. In this way, the single-phase bridge rectifier circuit can convert the input alternating current into a pulsating direct current.

[0064] In use, after power-on, the control unit 4 samples the voltage provided by the power supply module 1, and then detects whether the provided voltage meets the preset voltage. When it meets, the control unit 4 controls the first switch 232 to close, so as to turn on the circuit between the first resistor 231 and the electrolytic capacitor 3. At this time, the direct current provided by the rectifier bridge 21 charges the electrolytic capacitor 3. When the electrolytic capacitor 3 is charged to the preset capacity, the control unit 4 controls the relay unit 22 to close, so as to completely connect the electrolytic capacitor 3 to the circuit. When it does not meet, the control unit 4 controls the first switch 232 to open, so as to disconnect the circuit between the first resistor 231 and the electrolytic capacitor 3. At this time, an error prompt such as a flashing light can be made in a preset manner, so that the electrolytic capacitor 3 can be prevented from being damaged due to the mistaken connection of AC380V instead of AC220V.

[0065] The control unit 4 can determine that the electrolytic capacitor 3 is charged to the preset capacity according to the charging time length, or the control unit 4 can directly sample the capacity of the electrolytic capacitor 3 to determine that the electrolytic capacitor 3 is charged to the preset capacity.

[0066] The first resistor 231 can be a PTC resistor.

[0067] In one implementation manner, as shown in Figure 4 The relay unit 22 includes a first relay 221 and a first diode 222, and the first switch 232 includes a first transistor 2321.

[0068] The first output end of the power supply module 1 is connected with the first input end of the rectifier bridge 21.

[0069] The second output end of the power supply module 1 is connected with the second input end of the rectifier bridge 21.

[0070] The positive output end of the rectifier bridge 21 is connected with the first pin 41 of the control unit 4;

[0071] One end of the electrolytic capacitor 3 is connected in the circuit between the positive output end of the rectifier bridge 21 and the first pin 41 of the control unit 4, and the other end of the electrolytic capacitor 3 is connected with one end of the first resistor 231;

[0072] The second pin 42 of the control unit 4, the third end D of the first transistor 2321, the first contact terminal d of the first relay 221, the first coil terminal b of the first relay 221 and the anode of the first diode 222 are all connected with the negative output end of the rectifier bridge 21;

[0073] The second coil terminal a of the first relay 221 is connected with the third pin 43 of the control unit 4, and the second contact terminal c of the first relay 221 is connected in the circuit between the other end of the electrolytic capacitor 3 and one end of the first resistor 231;

[0074] The cathode of the first diode 222 is connected in the circuit between the second coil terminal a of the first relay 221 and the third pin 43 of the control unit 4;

[0075] The first end A of the first transistor 2321 is connected with the fourth pin 44 of the control unit 4, and the second end B of the first transistor 2321 is connected with the other end of the first resistor 231.

[0076] In order to enable the control unit 4 to sample the voltage provided by the power supply model to the electrolytic capacitor 3, the first output end of the power supply module 1 is connected with the anode of the fifth diode 11, the anode of the fifth diode 11 is connected with one end of the first voltage dividing resistor 12, the other end of the first voltage dividing resistor 12 is connected with one end of the second voltage dividing resistor 13, the other end of the second voltage dividing resistor 13 is connected with one end of the third voltage dividing resistor 14, one end of the filter capacitor 15 is connected with the other end of the second voltage dividing resistor 13 and the voltage sampling pin 45 of the control unit 4 respectively; the other end of the third voltage dividing resistor 14 and the other end of the filter capacitor 15 are connected with the negative output end of the rectifier bridge 21.

[0077] A relay is an electric control device that causes a predetermined step change in the controlled quantity in the electrical output circuit when the change in the input quantity (excitation quantity) reaches a specified requirement. It is mainly composed of a coil, a core, an armature, contacts, and a spring, etc. The coil is the input part of the relay, usually wound on the core. When there is current flowing through the coil, a magnetic field is generated, attracting the armature to move. The contacts are the output part of the relay, used to control the on-off of the external circuit. When the appropriate voltage (or current) is applied to the coil of the relay, the coil generates a magnetic field, and the magnetic field intensity increases with the increase of the current. This magnetic field will magnetize the core, thereby attracting the armature to move towards the core. The movement of the armature causes the spring connected thereto to move, thereby making the contacts close or open. For example, for a normally open contact relay, when there is no current flowing through the coil, the contacts are open; when the coil is energized, the armature is attracted, and the normally open contacts are closed, thereby connecting the external circuit. When the current in the coil disappears, the magnetic field weakens, and the armature returns to the original position under the elastic force of the spring, and the contacts return to the initial state.

[0078] In use, after power-on, the control unit 4 samples the voltage provided by the power supply module 1, and then detects whether the provided voltage meets the preset voltage. When it meets, the control unit 4 controls the first transistor 2321 to close, so as to turn on the circuit between the negative output end of the rectifier bridge 21 and the electrolytic capacitor 3. Since one end of the electrolytic capacitor 3 is connected to the positive output end of the rectifier bridge 21, the negative output end of the rectifier bridge 21 is connected in turn through the first transistor 2321, the first resistor 231, and the other end of the electrolytic capacitor 3. Thus, the electrolytic capacitor 3 can be charged by the rectifier bridge 21. When it does not meet, the control unit 4 controls the first transistor 2321 to open, so as to disconnect the circuit between the negative output end of the rectifier bridge 21 and the electrolytic capacitor 3, thereby avoiding charging the electrolytic capacitor 3 by the rectifier bridge 21.

[0079] In one implementation manner, as Figure 5As shown, the first transistor 2321 can be an Insulated-Gate Bipolar Transistor (IGBT), which is a hybrid device combining the features of a bipolar transistor (BJT) and an insulated-gate field-effect transistor (MOSFET). Structurally, it has three electrodes: collector (C), emitter (E), and gate (G). Internally, it is a four-layer semiconductor structure similar to a thyristor, but with significant differences in operation and characteristics. This structure allows IGBT to combine the high input impedance, simple drive circuit, and low on-state voltage drop, high current density of BJT with the advantages of MOSFET. The working principle of IGBT is based on the combined action of field effect and bipolar transistors. When a positive voltage is applied between the gate and emitter, a conductive channel is formed near the gate. This conductive channel allows electrons to be injected from the emitter into the drift region, and then under the action of the electric field between the collector and emitter, they move towards the collector, thus forming a current. Unlike MOSFET, IGBT has a small number of holes injected when it is turned on, which allows it to have a lower on-state voltage drop in high-voltage and high-current applications. For example, in power electronic converters, when IGBT is turned on, a large amount of current can pass through, and due to the injection of holes, its on-state loss is relatively low.

[0080] When the first transistor 2321 is an IGBT, the first end A of the first transistor 2321 is the gate; the second end B of the first transistor 2321 is the collector; and the third end D of the first transistor 2321 is the emitter.

[0081] In another implementation, the first transistor 2321 can also be a Metal-Oxide-Semiconductor Field-Effect Transistor (MOS) tube, which mainly has two types: N-channel MOS tube (NMOS) and P-channel MOS tube (PMOS), both of which contain three electrodes: gate (G), source (S), and drain (D). Taking NMOS as an example, its structure is to make two highly doped N+ regions as the source and drain on a P-type semiconductor substrate, with a very thin silicon dioxide (SiO2) insulating layer between the source and drain, and the gate is located above the insulating layer. The structure of PMOS is similar to NMOS, except that the substrate is N-type semiconductor and the source and drain are P+ regions. This structure allows MOS tubes to control the formation and disappearance of the conductive channel between the source and drain by changing the gate voltage, thereby achieving control over the current.

[0082] The present disclosure adopts NMOS tube, whose working principle is: when a positive voltage (V GS ) is applied between the gate and the source, and V GS is greater than the opening voltage (Vth), the silicon dioxide insulation layer below the gate generates an electric field perpendicular to the semiconductor surface. This electric field attracts the electrons in the P-type substrate to the surface, forming an N-type conductive channel to connect the source and the drain, at which time the current can flow from the drain to the source (I DS ). When V GS is less than Vth, the conductive channel disappears, the MOS tube is cut off, and I DS is approximately zero.

[0083] When the first transistor 2321 is a MOS tube, the first end of the first transistor 2321 is the gate; the second end B of the first transistor 2321 is the drain; and the third end D of the first transistor 2321 is the source.

[0084] In an implementation manner, the relay unit 22 includes: a second relay 223 and a second diode 224.

[0085] The first switch 232 includes: a silicon controlled rectifier 2322 and a first optocoupler 2323.

[0086] The first output end of the power supply module 1 is connected with the first input end of the rectifier bridge 21.

[0087] The second output end of the power supply module 1 is connected with the second input end of the rectifier bridge 21.

[0088] The positive output end of the rectifier bridge 21 is connected with the first pin 41 of the control unit 4.

[0089] One end of the first resistor 231 is connected in the circuit between the positive output end of the rectifier bridge 21 and the first pin 41 of the control unit 4, and the other end of the first resistor 231 is connected with the first end of the silicon controlled rectifier 2322. The second end of the silicon controlled rectifier 2322 is connected with one end of the electrolytic capacitor 3.

[0090] The first end of the first optocoupler 2323 is connected in the circuit between the other end of the first resistor 231 and the first end of the silicon controlled rectifier 2322. The second end of the first optocoupler 2323 is connected with the third end of the silicon controlled rectifier 2322 through the second resistor 2324. The anode of the light emitting diode of the first optocoupler 2323 is connected with the fourth pin 44 of the control unit 4 through the third resistor 2325. The cathode of the light emitting diode of the first optocoupler 2323 is connected with the negative output end of the rectifier bridge 21.

[0091] The first contact terminal of the second relay 223 is connected with one end of the first resistor 231, the second contact terminal of the second relay 223 is connected in the circuit between the second end of the thyristor 2322 and one end of the electrolytic capacitor 3, the first coil terminal of the second relay 223 is connected with the third pin 43 of the control unit 4, the second coil terminal of the second relay 223 is connected with the negative output end of the rectifier bridge 21; the cathode of the second diode 224 is connected between the first coil terminal of the second relay 223 and the third pin 43 of the control unit 4, the anode of the second diode 224 is connected with the negative output end of the rectifier bridge 21.

[0092] The other end of the electrolytic capacitor 3 is connected with the negative output end of the rectifier bridge 21.

[0093] The thyristor 2322 can include a unidirectional thyristor 2322 and a multidirectional thyristor.

[0094] In one implementation manner, when the thyristor 2322 is a unidirectional thyristor 2322, as shown in the figure, the relay unit 22 includes the second relay 223 and the second diode 224; the first switch 232 includes the unidirectional thyristor 2322 and the first optocoupler 2323. Figure 6

[0095] The first output end of the commercial power supply module 1 is connected with the first input end of the rectifier bridge 21;

[0096] The second output end of the commercial power supply module 1 is connected with the second input end of the rectifier bridge 21;

[0097] The positive output end of the rectifier bridge 21 is connected with the first pin 41 of the control unit 4;

[0098] One end of the first resistor 231 is connected in the circuit between the positive output end of the rectifier bridge 21 and the first pin 41 of the control unit 4, the other end of the first resistor 231 is connected with the anode of the unidirectional thyristor 2322, the cathode of the unidirectional thyristor 2322 is connected with one end of the electrolytic capacitor 3;

[0099] The light-sensitive transistor collector of the first optocoupler 2323 is connected in the circuit between the other end of the first resistor 231 and the anode of the unidirectional thyristor 2322, the light-sensitive transistor emitter of the first optocoupler 2323 is connected with the gate of the unidirectional thyristor 2322 through the second resistor 2324, the anode of the light-emitting diode of the first optocoupler 2323 is connected with the fourth pin 44 of the control unit 4 through the third resistor 2325, the cathode of the light-emitting diode of the first optocoupler 2323 is connected with the negative output end of the rectifier bridge 21;

[0100] ​The first contact terminal of the second relay 223 is connected with one end of the first resistor 231, the second contact terminal of the second relay 223 is connected in the circuit between the cathode of the unidirectional thyristor 2322 and one end of the electrolytic capacitor 3, the first coil terminal of the second relay 223 is connected with the third pin 43 of the control unit 4, the second coil terminal of the second relay 223 is connected with the negative output end of the rectifier bridge 21; the cathode of the second diode 224 is connected between the first coil terminal of the second relay 223 and the third pin 43 of the control unit 4, the anode of the second diode 224 is connected with the negative output end of the rectifier bridge 21.

[0101] The other end of the electrolytic capacitor 3 is connected with the negative output end of the rectifier bridge 21.

[0102] In order to enable the control unit 4 to sample the voltage provided by the power supply model to the electrolytic capacitor 3, the first output end of the power supply module 1 is connected with the anode of the fifth diode 11, the anode of the fifth diode 11 is connected with one end of the first voltage dividing resistor 12, the other end of the first voltage dividing resistor 12 is connected with one end of the second voltage dividing resistor 13, the other end of the second voltage dividing resistor 13 is connected with one end of the third voltage dividing resistor 14, one end of the filter capacitor 15 is connected with the other end of the second voltage dividing resistor 13 and the voltage sampling pin 45 of the control unit 4 respectively; the other end of the third voltage dividing resistor 14 and the other end of the filter capacitor 15 are connected with the negative output end of the rectifier bridge 21.

[0103] When the unidirectional thyristor 2322 and the first optocoupler 2323 are matched, when a high-level signal is output, current passes through the light-emitting diode on the input side of the first optocoupler 2323, causing it to emit light. The light emitted by the light-emitting diode shines on the phototransistor on the output side of the first optocoupler 2323, causing the phototransistor to conduct. After the phototransistor is turned on, the current between its collector and emitter flows into the gate of the unidirectional thyristor 2322. If there is a forward voltage between the anode and cathode of the unidirectional thyristor 2322 at this time (for an N-P-N structure unidirectional thyristor 2322, the anode potential is higher than the cathode potential), the unidirectional thyristor 2322 will be turned on under the triggering of the gate current. For example, in an AC dimming circuit, according to the duty cycle of the dimming signal, the first optocoupler 2323 periodically triggers the unidirectional thyristor 2322, causing the unidirectional thyristor 2322 to conduct at different times in the AC cycle, thereby changing the effective voltage across the bulb and achieving the dimming function. Once the unidirectional thyristor 2322 is turned on, it will remain in the on state as long as the current between the anode and cathode is greater than the holding current. The optocoupler no longer affects the on state of the unidirectional thyristor 2322 in this process. Only when the current between the anode and cathode falls below the holding current will the unidirectional thyristor 2322 naturally turn off. For example, in an AC circuit, when the AC voltage crosses zero, the anode-cathode current of the unidirectional thyristor 2322 naturally drops to zero, at which point the unidirectional thyristor 2322 turns off and waits for the next trigger.

[0104] The first optocoupler 2323 is a photo optically coupled thyristor (MOC, i.e. Photo Optically Coupled Thyristor) corresponding to the unidirectional thyristor 2322. The output end of this optocoupler is a photo thyristor structure that can control the conduction and turn-off of the thyristor through optical signals, thereby achieving isolated transmission of signals and triggering control of the unidirectional thyristor 2322.

[0105] In a photo optically coupled thyristor, the input end is usually a light-emitting diode that emits light signals when current passes through. The photo thyristor on the output end receives the light signals and generates corresponding current, triggering the unidirectional thyristor 2322 to conduct. Since the input and output of the optocoupler are coupled through optical signals, electrical isolation can be achieved, improving the safety and reliability of the circuit.

[0106] This optocoupler is widely used in circuits that require precise control of the unidirectional thyristor 2322 and electrical isolation, such as power supply control, dimming circuits, motor control, etc. Common photo optically coupled thyristor models include MOC3021, MOC3061, MOC3081, etc. These models have different trigger currents, voltage withstands, etc. in different circuits and can be selected according to specific application requirements.

[0107] In use, after power on, the control unit 4 samples the voltage provided by the power supply module 1, and then detects whether the provided voltage meets the preset voltage. When the provided voltage meets the preset voltage, the control unit 4 controls the current input to the first optocoupler 2323 to reach the holding current, so as to turn on the circuit between the positive output end of the rectifier bridge 21 and the electrolytic capacitor 3. Since one end of the electrolytic capacitor 3 is connected to the negative output end of the rectifier bridge 21, the positive output end of the rectifier bridge 21 is connected to the other end of the electrolytic capacitor 3 in turn through the first resistor 231 and the unidirectional thyristor 2322. In this way, the electrolytic capacitor 3 can be charged through the rectifier bridge 21. When the provided voltage does not meet the preset voltage, the control unit 4 controls the current input to the first optocoupler 2323 to drop below the holding current, so as to turn off the circuit between the positive output end of the rectifier bridge 21 and the electrolytic capacitor 3, thereby avoiding charging the electrolytic capacitor 3.

[0108] In an implementation manner, when the thyristor 2322 is a bidirectional thyristor, the first end of the thyristor 2322 is a first main electrode of the bidirectional thyristor, the second end of the thyristor 2322 is a second main electrode of the bidirectional thyristor, and the third end of the thyristor 2322 is a gate electrode of the bidirectional thyristor. The first optocoupler 2323 is an optocoupler used in correspondence with the bidirectional thyristor, wherein the first end of the first optocoupler 2323 is the first main electrode, and the second end of the first optocoupler 2323 is the second main electrode. At this time, the optocoupler is similar to the second optocoupler in Figure 7 , and details are not repeated here.

[0109] The second scheme is that the rectifier bridge 21 is located after the relay unit 22 and the switching unit 23.

[0110] Figure 7 The electrolytic capacitor protection circuit shown in FIG. 1 is an electrolytic capacitor protection circuit according to an example embodiment. As shown in FIG. 1, the switching unit 23 in the electrolytic capacitor protection circuit includes a second switch 233 and a fourth resistor 234. Figure 7

[0111] The fourth resistor 234 and the second switch 233 are connected in series to obtain a series circuit, and the series circuit and the relay unit 22 are connected in parallel to obtain a parallel module.

[0112] The power supply module 1, the parallel module, the rectifier bridge 21, and the electrolytic capacitor 3 are connected in sequence.

[0113] The control unit 4 is connected to the rectifier bridge 21, the second switch 233, the relay unit 22, and the power supply module 1, respectively.

[0114] ​In use, after power on, the control unit 4 samples the voltage provided by the power supply module 1, and then detects whether the provided voltage meets the preset voltage. When it meets, the control unit 4 controls the second switch 233 to be closed to turn on the circuit between the power supply module 1 and the rectifier bridge 21. At this time, the direct current provided by the rectifier bridge 21 charges the electrolytic capacitor 3. When the electrolytic capacitor 3 is charged to the preset capacity, the control unit 4 controls the relay unit 22 to be closed to completely connect the electrolytic capacitor 3 to the circuit. When it does not meet, the control unit 4 controls the second switch 233 to be opened to disconnect the circuit between the power supply module 1 and the rectifier bridge 21. At this time, an error prompt such as a flashing light can be made in a preset manner, so that the electrolytic capacitor 3 can be prevented from being damaged due to the misconnection of AC380V instead of AC220V.

[0115] In an implementation manner, as shown in Figure 8 the relay unit 22 includes a third relay 225 and a third diode 226, and the second switch 233 includes a bidirectional thyristor 2331 and a second optocoupler 2332.

[0116] The first output end of the power supply module 1 is connected to the first pin 41 of the control unit 4 through a fourth diode 5.

[0117] The first output end of the power supply module 1 is also connected to one end of a fourth resistor 234.

[0118] The second output end of the power supply module 1 is connected to the second input end of the rectifier bridge 21.

[0119] The other end of the fourth resistor 234 is connected to the first main electrode of the bidirectional thyristor 2331, the second main electrode of the bidirectional thyristor 2331 is connected to the first input end of the rectifier bridge 21, and the gate of the bidirectional thyristor 2331 is connected to the second main electrode of the second optocoupler 2332 through a fifth resistor 235.

[0120] The first main electrode of the second optocoupler 2332 is connected in the circuit between the fourth resistor 234 and the first main electrode of the bidirectional thyristor 2331, the anode of the light-emitting diode of the second optocoupler 2332 is connected to the fourth pin 44 of the control unit 4 through a sixth resistor 236, and the cathode of the light-emitting diode of the second optocoupler 2332 is connected to the negative output end of the rectifier bridge 21.

[0121] The first contact terminal of the third relay 225 is connected in the circuit between the first output of the mains supply module 1 and one end of the fourth resistor 234, the second contact terminal of the relay is connected in the circuit between the second main electrode of the bidirectional thyristor 2331 and the first input of the rectifier bridge 21, the first coil end of the third relay 225 is connected with the third pin 43 of the control unit 4, the second coil end of the third relay 225 is connected with the negative output of the rectifier bridge 21, the cathode of the third diode 226 is connected in the circuit between the first coil end of the third relay 225 and the third pin 43 of the control unit 4, the anode of the third diode 226 is connected in the circuit between the second coil end of the third relay 225 and the negative output of the rectifier bridge 21;

[0122] The positive output of the rectifier bridge 21 is connected with one end of the electrolytic capacitor 3.

[0123] The negative output of the rectifier bridge 21 is also connected with the other end of the electrolytic capacitor 3.

[0124] In order to enable the control unit 4 to sample the voltage provided by the mains supply module to the electrolytic capacitor 3, the first output of the mains supply module 1 is connected with the anode of the fifth diode 11, the anode of the fifth diode 11 is connected with one end of the first voltage dividing resistor 12, the other end of the first voltage dividing resistor 12 is connected with one end of the second voltage dividing resistor 13, the other end of the second voltage dividing resistor 13 is connected with one end of the third voltage dividing resistor 14, one end of the filter capacitor 15 is connected with the other end of the second voltage dividing resistor 13 and the voltage sampling pin 45 of the control unit 4 respectively, the other end of the third voltage dividing resistor 14 and the other end of the filter capacitor 15 are connected with the negative output of the rectifier bridge 21.

[0125] Anode of input side (LED side): This is the positive terminal of the input side LED. When a forward voltage is applied between this pin and the cathode, the LED can emit light. This voltage generally meets the forward conduction condition of the LED, usually around 1.2-1.4V. In circuit connection, it is usually connected to the output terminal of the control signal source, such as an output pin of a microcontroller. When the microcontroller outputs a high level signal and passes through a suitable current limiting resistor, it can make the LED emit light, thereby starting the signal transmission process of the optocoupler. Cathode of input side (LED side): It is the negative terminal of the input side LED. It is used in conjunction with the anode. Only when the anode-cathode forms a forward conduction condition (anode potential higher than cathode potential), the LED will work. If the voltage polarity between the anode and the cathode is wrong, the LED will not emit light, and the optocoupler will not be able to normally transmit signals. It is usually connected to the low potential end of the circuit or the ground, depending on the design of the circuit. In some simple digital circuit isolation applications, the cathode is directly connected to the ground, so that the brightness of the LED can be easily controlled by controlling the level of the anode. First main electrode T1 of output side (phototriac side): This is one of the main electrodes of the output side phototriac. In the triac optocoupler, when the input side LED emits light and the output side phototriac is turned on by light, current can flow bidirectionally between T1 and the other main electrode T2. The specific connection of T1 in the circuit depends on the load being controlled and the specific application scenario. For example, in an AC dimming circuit, T1 may be connected to one end of the AC power source, and T2 controls the voltage on the load (such as a bulb) together. Second main electrode T2 of output side (phototriac side): It is the other main electrode of the output side phototriac. Cooperate with T1, when the optocoupler is working normally and the phototriac is turned on, current can flow bidirectionally between T1 and T2. In practical applications, T2 is also connected according to the requirements of the load and the circuit. For example, in an AC motor speed control circuit, T2 may be connected to one end of the AC motor, and the voltage effective value between the two ends of the motor is adjusted by controlling the optocoupler, thereby controlling the speed of the motor.

[0126] Among them, the second optocoupler 2332 is an optocoupler corresponding to the triac 2331, such as a triac optocoupler or a triac output optocoupler. Common triac optocouplers include the following:

[0127] ELM3052: Widely used in industrial control, communication equipment and other fields. It can effectively realize signal isolation transmission and control of triac 2331, with high reliability and stability.

[0128] AQH2223: The internal structure is to package a light emitting diode with two photosensitive triacs together. It has 0.9A maximum load current, 600V maximum load voltage, belongs to random switching type, and adopts 8-pin SMD package.

[0129] EL3021: It is commonly used in speed-regulating fans, air conditioners and other equipment, and can accurately control and regulate AC loads.

[0130] When these triac optocouplers work, the input end light emitting diode converts electrical energy into optical signals, and the output end photosensitive triac receives the optical signals to generate photoelectric current, thereby triggering the conduction or turn-off of the triac 2331, realizing the isolated transmission of signals and the control of the triac 2331.

[0131] In use, after power-on, the control unit 4 samples the voltage provided by the power supply module 1, and then detects whether the provided voltage meets the preset voltage. When it meets, the control unit 4 controls the current input to the second optocoupler 2332 to reach the holding current, so as to turn on the circuit between the power supply module 1 and the rectifier bridge 21. Since one end of the electrolytic capacitor 3 is connected to the positive output end of the rectifier bridge 21, and the other end of the electrolytic capacitor 3 is connected to the negative output end of the rectifier bridge 21, the rectifier bridge 21 can work normally since it is turned on. Thus, the electrolytic capacitor 3 can be charged through the rectifier bridge 21. When it does not meet, the control unit 4 controls the current input to the second optocoupler 2332 to drop below the holding current, so as to disconnect the circuit between the power supply module 1 and the rectifier bridge 21, thereby avoiding charging the electrolytic capacitor 3.

[0132] The present disclosure also provides an electric tool comprising the electrolytic capacitor protection circuit according to any one of the above embodiments.

[0133] The technical features of the above embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above embodiments are not described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0134] The principles and implementation modes of the present application are described by using specific examples in this paper, and the above embodiments are only used to help understand the method and its core idea of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range can be changed. In conclusion, the content of the present disclosure should not be understood as a limitation of the present application.

Claims

1. An electrolytic capacitor protection circuit, characterized in that, The electrolytic capacitor protection circuit includes: Mains power supply module, current power output module, and control unit; The current power output module includes: a switching unit; The mains power supply module, the switching unit, and the electrolytic capacitor are connected in sequence. The control unit is connected to the switch unit; The control unit is also connected to the mains power supply module; The control unit is configured to control the switching unit to disconnect the circuit between the mains power supply module and the electrolytic capacitor when the output voltage of the mains power supply module is detected to be higher than a preset voltage. The current power output module also includes a rectifier bridge and a relay unit; The switching unit includes: a first resistor and a first switch; The mains power supply module, the rectifier bridge, the first resistor, the first switch, and the electrolytic capacitor are connected in sequence. The relay unit is connected to the rectifier bridge and the electrolytic capacitor respectively; The control unit is connected to the relay unit, the first switch and the mains power supply module respectively; The relay unit includes: a first relay and a first diode; The first switch includes: a first transistor; The first output terminal of the mains power supply module is connected to the first input terminal of the rectifier bridge; The second output terminal of the mains power supply module is connected to the second input terminal of the rectifier bridge; The positive output terminal of the rectifier bridge is connected to the first pin of the control unit; One end of the electrolytic capacitor is connected in the line between the positive output terminal of the rectifier bridge and the first pin of the control unit, and the other end of the electrolytic capacitor is connected to one end of the first resistor. The second pin of the control unit, the third terminal of the first transistor, the first contact terminal of the first relay, the first coil terminal of the first relay, and the anode of the first diode are all connected to the negative output terminal of the rectifier bridge. The second coil terminal of the first relay is connected to the third pin of the control unit, and the second contact terminal of the first relay is connected in the line between the other end of the electrolytic capacitor and one end of the first resistor; The cathode of the first diode is connected in the line between the second coil terminal of the first relay and the third pin of the control unit; The first terminal of the first transistor is connected to the fourth pin of the control unit, and the second terminal of the first transistor is connected to the other terminal of the first resistor.

2. The electrolytic capacitor protection circuit according to claim 1, characterized in that, The first transistor includes: an IGBT; The first terminal of the first transistor is the gate; The second terminal of the first transistor is the collector. The third terminal of the first transistor is the emitter.

3. The electrolytic capacitor protection circuit according to claim 1, characterized in that, The first transistor includes: a MOS transistor; The first terminal of the first transistor is the gate; The second terminal of the first transistor is the drain. The third terminal of the first transistor is the source.

4. The electrolytic capacitor protection circuit according to claim 1, characterized in that, The relay unit includes: a second relay and a second diode; The first switch includes: a silicon controlled rectifier (SCR) and a first optocoupler; One end of the first resistor is connected in the line between the positive output terminal of the rectifier bridge and the first pin of the control unit, and the other end of the first resistor is connected to the first terminal of the thyristor, and the second terminal of the thyristor is connected to one end of the electrolytic capacitor. The first end of the first optocoupler is connected in the line between the other end of the first resistor and the first end of the thyristor. The second end of the first optocoupler is connected to the third end of the thyristor through the second resistor. The anode of the light-emitting diode of the first optocoupler is connected to the fourth pin of the control unit through the third resistor. The cathode of the light-emitting diode of the first optocoupler is connected to the negative output terminal of the rectifier bridge. The first contact terminal of the second relay is connected to one end of the first resistor, the second contact terminal of the second relay is connected in the circuit between the second end of the thyristor and one end of the electrolytic capacitor, the first coil terminal of the second relay is connected to the third pin of the control unit, and the second coil terminal of the second relay is connected to the negative output terminal of the rectifier bridge; the cathode of the second diode is connected between the first coil terminal of the second relay and the third pin of the control unit, and the anode of the second diode is connected to the negative output terminal of the rectifier bridge. The other end of the electrolytic capacitor is connected to the negative output terminal of the rectifier bridge.

5. The electrolytic capacitor protection circuit according to claim 1, characterized in that, The switching unit includes: a second switch and a fourth resistor; The fourth resistor is connected in series with the second switch to form a series circuit, and the series circuit is connected in parallel with the relay unit to form a parallel module. The mains power supply module, the parallel module, the rectifier bridge, and the electrolytic capacitor are connected in sequence; The control unit is connected to the rectifier bridge, the second switch, the relay unit, and the mains power supply module, respectively.

6. The electrolytic capacitor protection circuit according to claim 5, characterized in that, The relay unit includes: a third relay and a third diode; The second switch includes: a bidirectional thyristor and a second optocoupler; The first output terminal of the mains power supply module is connected to the first pin of the control unit through a fourth diode; The first output terminal of the mains power supply module is also connected to one end of the fourth resistor; The other end of the fourth resistor is connected to the first main electrode of the bidirectional thyristor, the second main electrode of the bidirectional thyristor is connected to the first input terminal of the rectifier bridge, and the gate of the bidirectional thyristor is connected to the second main electrode of the second optocoupler through the fifth resistor. The first main electrode of the second optocoupler is connected in the line between the fourth resistor and the first main electrode of the bidirectional thyristor. The anode of the light-emitting diode of the second optocoupler is connected to the fourth pin of the control unit through the sixth resistor. The cathode of the light-emitting diode of the second optocoupler is connected to the negative output terminal of the rectifier bridge. The first contact terminal of the third relay is connected in the line between the first output terminal of the mains power supply module and one end of the fourth resistor; the second contact terminal of the relay is connected in the line between the second main electrode of the bidirectional thyristor and the first input terminal of the rectifier bridge; the first coil terminal of the third relay is connected to the third pin of the control unit; the second coil terminal of the third relay is connected to the negative output terminal of the rectifier bridge; the cathode of the third diode is connected in the line between the first coil terminal of the third relay and the third pin of the control unit; and the anode of the third diode is connected in the line between the second coil terminal of the third relay and the negative output terminal of the rectifier bridge. The positive output terminal of the rectifier bridge is connected to one end of the electrolytic capacitor; The negative output terminal of the rectifier bridge is also connected to the other end of the electrolytic capacitor.

7. The electrolytic capacitor protection circuit according to any one of claims 2-6, characterized in that, The first output terminal of the mains power supply module is connected to the anode of the fifth diode. The anode of the fifth diode is connected to one end of the first voltage divider resistor. The other end of the first voltage divider resistor is connected to one end of the second voltage divider resistor. The other end of the second voltage divider resistor is connected to one end of the third voltage divider resistor. One end of the filter capacitor is connected to the other end of the second voltage divider resistor and the voltage sampling pin of the control unit, respectively. The other end of the third voltage divider resistor and the other end of the filter capacitor are connected to the negative output terminal of the rectifier bridge.

8. A power tool, characterized in that, Includes the electrolytic capacitor protection circuit as described in any one of claims 1-7.

Images