Circuit for reducing ripple current of electrolytic capacitor

Abstract

The utility model discloses a circuit for reducing ripple current of an electrolytic capacitor, which comprises a voltage source, a rectifier bridge, a switching circuit and a first capacitor which are electrically connected in sequence, the switching circuit comprises a first switching tube, a first triode and a first resistor, a drain electrode of the first switching tube is connected with the first capacitor, and a drain electrode of the first triode is connected with the second capacitor. The source electrode of the first switch tube is connected with the base electrode of the first triode and the first resistor, the voltage source inputs voltage to the first resistor, and the first resistor is used for controlling the first switch tube and the first triode to be switched on and switched off according to the voltage of the first resistor. According to the utility model, the ripple current of the electrolytic capacitor can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronics, in particular to a circuit for reducing the ripple current of an electrolytic capacitor. Background Art

[0002] A high-speed blower can be a common household small appliance high-speed hair dryer, which is usually used to dry hair. Its working principle is to blow out the air heated by the internal heating wire through strong wind force, thereby forming a high-speed and high-temperature airflow to accelerate the hair drying process. A high-speed hair dryer is usually composed of a high-speed brushless motor, heating wire, structural parts, control circuit board and other components.

[0003] High-speed fans are also a common industrial equipment, usually used for drying, dust removal and material conveying. Its working principle is to blow air into the equipment through strong wind force, thereby forming a high-speed airflow to accelerate the drying process of materials or transport materials from one location to another. High-speed fans are usually composed of fans, heaters, conveying pipelines and other components. In industrial production, high-speed fans are widely used in food processing, chemical industry, building materials, metallurgy and other fields, which can improve production efficiency and ensure product quality.

[0004] Since the operation and control mode of the high-speed brushless motor in the high-speed fan will cause the problem of large ripple current of the electrolytic capacitor, the high-frequency component in the ripple current will cause certain damage to the high-speed fan. Utility Model Content

[0005] The main purpose of the utility model is to provide a circuit for reducing the ripple current of an electrolytic capacitor, aiming at reducing the ripple current of the electrolytic capacitor.

[0006] To achieve the above-mentioned purpose, the utility model proposes a circuit for reducing the ripple current of an electrolytic capacitor, comprising a voltage source, a rectifier bridge, a switching circuit, and a first capacitor electrically connected in sequence, the switching circuit comprising a first switching tube, a first transistor, and a first resistor, the drain of the first switching tube being connected to the first capacitor, the source of the first switching tube being connected to the base of the first transistor and the first resistor, the voltage source inputting a voltage to the first resistor, and the first resistor being used to control the conduction and closing of the first switching tube and the first transistor by the voltage size of the first resistor.

[0007] In one embodiment, the rectifier bridge includes a first diode, a second diode, a third diode, and a fourth diode, the anode of the first diode is connected to the cathode of the second diode, the anode of the voltage source is connected between the first diode and the second diode, the anode of the third diode is connected to the cathode of the fourth diode, and the cathode of the voltage source is connected between the third diode and the fourth diode.

[0008] In one embodiment, the circuit further includes a second capacitor, which is connected in parallel with the rectifier bridge.

[0009] In one embodiment, the circuit further includes a fifth diode, a cathode of the fifth diode is connected to the first capacitor, and an anode of the fifth diode is grounded.

[0010] In one embodiment, the circuit further includes a sixth diode, and a cathode of the sixth diode is connected to the gate of the first switch tube.

[0011] In one embodiment, the circuit further includes a second resistor, one end of the second resistor is electrically connected to the voltage source, and the other end of the second resistor is connected to the collector of the first transistor.

[0012] In one embodiment, the circuit further includes a third resistor, and the third resistor is connected in parallel with the rectifier bridge.

[0013] In one embodiment, the third resistor is an adjustable resistor.

[0014] The utility model controls the on and off of the first switch tube and the first triode by using the voltage size passing through the first resistor. When the current flowing through the first resistor continues to increase, the voltage of the first resistor also continues to rise, the first triode is turned on, and the first switch tube is turned off; when the first switch tube is turned off, the voltage of the first resistor drops, the first triode is turned off, and the first switch tube is turned on, thereby achieving dynamic stability, so the peak ripple current of the first capacitor is limited, and the ripple current of the electrolytic capacitor is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0016] Figure 1 Circuit diagram for reducing the ripple current of electrolytic capacitors;

[0017] Figure 2 Waveform diagram after adding circuit to high-speed fan;

[0018] Figure 3 This is the waveform diagram of the high-speed fan after removing the circuit.

[0019] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0021] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0022] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if the meaning of "and / or" appearing in the full text is to include three parallel schemes, taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the utility model.

[0023] The utility model proposes a circuit for reducing the ripple current of an electrolytic capacitor, comprising a voltage source V1, a rectifier bridge 1, a switch circuit 2, and a first capacitor C2 which are electrically connected in sequence, wherein the switch circuit 2 comprises a first switch tube M1, a first transistor Q1, and a first resistor R1, wherein the drain of the first switch tube M1 is connected to the first capacitor C2, the source of the first switch tube M1 is connected to the base of the first transistor Q1 and the first resistor R1, the voltage source V1 inputs a voltage to the first resistor R1, and the first resistor R1 is used to control the conduction and closing of the first switch tube M1 and the first transistor Q1 through the voltage magnitude of the first resistor R1.

[0024] In the embodiment of the present utility model, Figure 1As shown, the circuit controls the on and off of the first switch tube M1 and the first triode Q1 through the voltage of the first resistor R1. When the current flowing through the first resistor R1 continues to increase, the voltage of the first resistor R1 also continues to rise, the first triode Q1 is turned on, and the first switch tube M1 is turned off; when the first switch tube M1 is turned off, the voltage of the first resistor R1 drops, the first triode Q1 is turned off, and the first switch tube M1 is turned on, achieving dynamic stability, so the peak ripple current of the first capacitor C2 is limited, reducing the ripple current of the electrolytic capacitor;

[0025] like Figure 1 As shown, the first capacitor C2 is an electrolytic capacitor, and the current direction of the first capacitor C2 is: from the voltage source V1, the rectifier bridge 1, the first capacitor C2, the first switch tube M1, the first resistor R1, and the ground terminal;

[0026] When the current flowing through the first resistor R1 continues to increase, the voltage on the first resistor R1 increases. When the voltage on the first resistor R1 is greater than 0.65V (this parameter comes from the 2N3904 device specification), the conduction threshold of the first transistor Q1 is reached, and the first transistor Q1 is turned on, so that the base of the first switch tube M1 is pulled to the ground end, and the first switch tube M1 is controlled to be turned off.

[0027] When the first switch tube M1 is turned off, no current flows through the first resistor R1, and the voltage on the first resistor R1 will be lower than the conduction threshold of the first transistor Q1, and the first transistor Q1 is turned off again;

[0028] The first transistor Q1 is turned off, which causes the first switch tube M1 to be turned on again, and the cycle repeats like this;

[0029] When dynamic stability is achieved, the base voltage of the first transistor Q1 always maintains the turn-on threshold of 0.65V, which is the balance point.

[0030] Therefore, the peak ripple current of the first capacitor C2 will be limited, and the value under dynamic balance is about 420 mA.

[0031] The main reason for the surge current is the charging current of the first capacitor C2 at the moment of power-on. Due to the above working principle, the charging current of the first capacitor C2 is limited, so the input surge current can be reduced at the same time, and the NTC thermistor at the input end of the circuit can be omitted.

[0032] like Figure 2 and Figure 3 As shown, after the circuit for reducing the ripple current of the electrolytic capacitor is applied to the high-speed fan, the current peak reaches 420mA, and after removing the circuit for reducing the ripple current of the electrolytic capacitor, the current peak reaches 1.4A. After the high-speed fan is added with the circuit of this embodiment, the ripple current of the electrolytic capacitor can be effectively reduced.

[0033] The rectifier bridge 1 includes a first diode D5, a second diode D6, a third diode D3, and a fourth diode D4. The anode of the first diode D5 is connected to the cathode of the second diode D6, the anode of the voltage source V1 is connected between the first diode D5 and the second diode D6, the anode of the third diode D3 is connected to the cathode of the fourth diode D4, and the cathode of the voltage source V1 is connected between the third diode D3 and the fourth diode D4. Through such a connection method, the rectifier bridge 1 can convert the input AC signal into a unidirectional DC signal output.

[0034] The circuit further includes a fifth diode D1 , a cathode of the fifth diode D1 is connected to the first capacitor C2 , and an anode of the fifth diode D1 is grounded.

[0035] Connecting the fifth diode D1 to the ground can be used as a circuit protection method. When an overvoltage or reverse voltage appears in the circuit, the fifth diode D1 will work to lead the overvoltage or reverse voltage to the ground to prevent other components in the circuit from being damaged.

[0036] The circuit further includes a sixth diode D2, a cathode of which is connected to the gate of the first switch tube M1.

[0037] By properly connecting the sixth diode D2 and the first switch tube M1, the switching speed of the circuit can be increased. For example, in some power amplifiers, the sixth diode D2 and the first switch tube M1 are connected in parallel to increase the switching speed and reduce power loss during the switching process.

[0038] The circuit further includes a second resistor R2, one end of the second resistor R2 is electrically connected to the voltage source V1, and the other end of the second resistor R2 is connected to the collector of the first transistor Q1.

[0039] The circuit also includes a third resistor I1, which is connected in parallel with the rectifier bridge 1. The third resistor I1 is an adjustable resistor. By changing the value of the third resistor I1 in the circuit, the current in the circuit can be adjusted, thereby controlling the working condition of the circuit. The adjustable resistor can be used to adjust the voltage in the circuit; by adjusting the resistance value in the circuit, the power in the circuit can be controlled to ensure that the circuit works normally and is not damaged.

[0040] The above description is only an optional embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A circuit for reducing the ripple current of an electrolytic capacitor, characterized in that: It includes a voltage source, a rectifier bridge, a switching circuit, and a first capacitor that are electrically connected in sequence. The switching circuit includes a first switching tube, a first triode, and a first resistor. The drain of the first switching tube is connected to the first capacitor, the source of the first switching tube is connected to the base of the first triode and the first resistor, the voltage source inputs voltage to the first resistor, and the first resistor is used to control the conduction and closing of the first switching tube and the first triode through the voltage of the first resistor.

2. The circuit according to claim 1, characterized in that The rectifier bridge includes a first diode, a second diode, a third diode, and a fourth diode. The anode of the first diode is connected to the cathode of the second diode, the anode of the voltage source is connected between the first diode and the second diode, the anode of the third diode is connected to the cathode of the fourth diode, and the cathode of the voltage source is connected between the third diode and the fourth diode.

3. The circuit according to claim 1, characterized in that The circuit further includes a second capacitor connected in parallel with the rectifier bridge.

4. The circuit according to claim 1, characterized in that The circuit further includes a fifth diode, a cathode of the fifth diode is connected to the first capacitor, and an anode of the fifth diode is grounded.

5. The circuit according to claim 1, characterized in that The circuit further includes a sixth diode, a cathode of which is connected to the gate of the first switch tube.

6. The circuit according to claim 1, characterized in that The circuit further includes a second resistor, one end of which is electrically connected to the voltage source, and the other end of which is connected to the collector of the first transistor.

7. The circuit according to claim 1, characterized in that The circuit further includes a third resistor, which is connected in parallel with the rectifier bridge.

8. The circuit according to claim 7, characterized in that The third resistor is an adjustable resistor.

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