An electrolytic capacitor discharge circuit

Abstract

The application relates to an electrolytic capacitor discharging circuit, which comprises an input circuit, a rectification filter circuit, a constant-current discharging circuit, a discharging-off circuit and the like; the front end of the input circuit is connected with an L terminal and an N terminal of a power supply access, and the rear end of the input circuit is connected with the rectification filter circuit; the input circuit comprises a fuse, a first filter capacitor, a second filter capacitor and a common-mode inductor, the fuse is connected with a power supply input end, and the first filter capacitor, the second filter capacitor and the common-mode inductor are connected; the rectification filter circuit comprises a rectification bridge stack and a filter capacitor, the front end of the rectification bridge stack is connected with the input circuit, and the rear end of the rectification bridge stack is connected with the filter capacitor. The technical scheme of the application provides a discharging technology which is energy-saving and has high efficiency.

Description

Technical Field

[0001] This application relates to the field of switching power supply technology, and in particular to an electrolytic capacitor discharge circuit. Background Technology

[0002] In high-power switching power supplies, the electrolytic capacitors after the high-voltage side rectifier bridge are often used as filtering components. Their large capacitance helps stabilize the output voltage. However, after the power is turned off, the charge stored at the leads of the electrolytic capacitors persists for a considerable period, affecting the user experience. For example, lighting fixtures using switching power supplies do not immediately turn off after the power is switched off, but remain lit for a while; similarly, running machines do not immediately stop operating after the power is turned off due to the stored charge in the capacitors, but continue to run for a period of time.

[0003] To address this issue, existing technologies typically involve connecting a discharge resistor in parallel across the electrolytic capacitor to achieve rapid discharge. However, this method requires careful consideration of the resistor value: if the resistance is too small, while rapid discharge is possible, it leads to a significant increase in power consumption and excessive heat generation; if the resistance is too large, the discharge speed will be slower, although power consumption will be relatively lower. Given the current technological trend towards high efficiency and low power consumption, this traditional approach is clearly no longer sufficient. Utility Model Content

[0004] This application provides an electrolytic capacitor discharge circuit to solve the problem that high efficiency and low power consumption cannot be achieved simultaneously in the prior art discharge circuits.

[0005] Therefore, in a first aspect, embodiments of this application provide an electrolytic capacitor discharge circuit, including: an input circuit, a rectifier and filter circuit, a constant current discharge circuit, a discharge shutdown circuit, etc.; the front end of the input circuit is connected to the mains power input L terminal and N terminal, and the rear end of the input circuit is connected to the rectifier and filter circuit;

[0006] The input circuit includes a fuse, a first filter capacitor, a second filter capacitor, and a common-mode inductor. The fuse is connected to the mains input terminal, and the first filter capacitor, the second filter capacitor, and the common-mode inductor are connected together.

[0007] The rectifier and filter circuit includes a rectifier bridge and a filter capacitor. The front end of the rectifier bridge is connected to the input circuit, and the rear end of the rectifier bridge is connected to the filter capacitor. After the AC power enters the rectifier bridge and the filter capacitor, it is rectified and filtered to obtain a stable high-voltage DC power.

[0008] The constant current discharge circuit includes a first resistor, a third resistor, a fourth resistor, a first transistor, a second transistor, a discharge transistor, and a Zener diode; the first resistor and the third resistor are bias resistors for the discharge transistor, and the fourth resistor is a current sensing resistor;

[0009] The discharge shutdown circuit includes a first rectifier diode, a second rectifier diode, a second resistor, and a capacitor; the second resistor provides a discharge path for the capacitor.

[0010] An electrolytic capacitor discharge circuit according to an embodiment of this application includes: an input circuit, a rectifier and filter circuit, a constant current discharge circuit, and a discharge shutdown circuit; wherein, the input circuit includes a fuse, a first filter capacitor, a second filter capacitor, and a common-mode inductor, the fuse being connected to the mains input terminal, and the first filter capacitor, the second filter capacitor, and the common-mode inductor being connected; the rectifier and filter circuit includes a rectifier bridge and a filter capacitor, the front end of the rectifier bridge being connected to the input circuit, and the rear end of the rectifier bridge being connected to the filter capacitor; the constant current discharge circuit includes a first resistor, a third resistor, a fourth resistor, a first transistor, a second transistor, a discharge transistor, and a Zener diode; the first resistor and the third resistor are bias resistors for the discharge transistor, and the fourth resistor is a current sensing resistor; the discharge shutdown circuit includes a first rectifier diode, a second rectifier diode, a second resistor, and a capacitor; the second resistor provides a discharge path for the capacitor. This application proposes an electrolytic capacitor discharge circuit suitable for high-voltage bus capacitor discharge. It has the advantages of rapid discharge and stable and controllable discharge current. This method does not require a fixed discharge resistor in the high-voltage bus capacitor, effectively avoiding the energy loss generated by the discharge resistor in the circuit, and provides a discharge technology that is both efficient and energy-saving. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort. In addition, in the drawings, the same parts use the same reference numerals, and the drawings are not drawn to scale.

[0012] Figure 1 This is a schematic diagram of the structure of an electrolytic capacitor discharge circuit provided in an embodiment of this application. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0014] This utility model aims to improve upon the problems existing in the capacitor discharge circuit of the prior art. Through innovative design and technical means, it solves the problems that the existing technology is prone to large no-load loss and long discharge time after power-off. Based on this, the embodiments of this application provide an electrolytic capacitor discharge circuit. The following is a detailed description of this application through specific embodiments.

[0015] Figure 1 This is a schematic diagram of the structure of an electrolytic capacitor discharge circuit provided in an embodiment of this application, referring to... Figure 1 As shown, the electrolytic capacitor discharge circuit provided in this embodiment includes: an input circuit, a rectifier and filter circuit, a constant current discharge circuit, and a discharge shutdown circuit; wherein, the front end of the input circuit is connected to the mains power input L terminal and N terminal, and the rear end of the input circuit is connected to the rectifier and filter circuit.

[0016] Specific reference Figure 1 The aforementioned input circuit includes a fuse F1, a first filter capacitor CX1, a second filter capacitor CX2, and a common-mode inductor LF1. The fuse F1 is connected to the mains input terminal, and the first filter capacitor CX1, the second filter capacitor CX2, and the common-mode inductor LF1 are connected together. When the mains power is input, high-frequency interference is filtered through the fuse F1, the first filter capacitor CX1, the second filter capacitor CX2, and the common-mode inductor LF1, resulting in a clean and stable AC power supply.

[0017] The above-mentioned rectifier and filter circuit includes a rectifier bridge BD1 and an electrolytic capacitor EC1. The front end of the rectifier bridge BD1 is connected to the input circuit, and the rear end of the rectifier bridge BD1 is connected to the filter capacitor EC1.

[0018] The constant current discharge circuit mentioned above includes a first resistor R1, a third resistor R3, a fourth resistor R4, a first transistor Q1, a second transistor Q2, a discharge transistor Q3, and a Zener diode ZD1; the first resistor R1 and the third resistor R3 are bias resistors for the discharge transistor Q3, and the fourth resistor R4 is a current sensing resistor.

[0019] The aforementioned discharge shutdown circuit includes a first rectifier diode D1, a second rectifier diode D2, a second resistor R2, and a capacitor C1; the second resistor R2 provides a discharge path for the capacitor C1. The aforementioned discharge shutdown circuit operates at a high level when AC power is applied, and is used to control the operation of the constant current discharge circuit.

[0020] The present invention provides an electrolytic capacitor discharge circuit, which is a circuit for discharging the high-voltage bus capacitor of a switching power supply after power failure, solving the problem that the bus capacitor cannot discharge due to prolonged energization after the mains power is cut off.

[0021] The specific working principle of this application is as follows: When the mains power is turned on, high-frequency interference is filtered through fuse F1, first filter capacitor CX1, second filter capacitor CX2 and common mode inductor LF1, and a clean and stable AC power is obtained after filtering.

[0022] The alternating current enters the rectifier bridge BD1 and electrolytic capacitor EC1 for rectification and filtering, resulting in a stable high-voltage direct current. This high-voltage direct current is marked HV and is used in subsequent circuits. Electrolytic capacitor EC1 has a large capacitance, and a relatively high voltage remains across it even after power is off.

[0023] The alternating current flows through another path, passing through the first rectifier diode D1, the second rectifier diode D2, the second resistor R2, and the capacitor C1 for rectification and filtering. A second high-voltage direct current is then obtained across capacitor C1. This circuit is also called the discharge shutdown circuit, which controls the switching of the discharge circuit. Here, the capacitance of capacitor C1 is extremely small, storing only a tiny amount of energy; we refer to this high voltage as the high level.

[0024] When AC power is applied, the terminals of capacitor C1 are at a high level. Transistor Q1, being a PNP transistor, is not conducting at a high level. The base of discharge transistor Q3 is not biased and is also at a low level, meaning it is not conducting. Therefore, the constant current discharge circuit does not operate, and the entire discharge circuit experiences almost no losses.

[0025] When the AC power is cut off, the capacitance of capacitor C1 in the discharge shutdown circuit is extremely small, and the time it retains the charge is extremely short. Therefore, the high level across capacitor C1 will quickly become low through the second resistor R2. The low level of capacitor C1 turns on Q1, and there is a bias current at the base of discharge tube Q3, so Q3 begins to conduct and discharge.

[0026] The discharge current flows through the fourth resistor R4 to the negative electrode of electrolytic capacitor EC1, and a voltage drop is generated across the fourth resistor R4.

[0027] The fourth resistor R4 is connected to the second transistor Q2. When the voltage drop across R4 is greater than the turn-on voltage of the base of the second transistor Q2, Q2 starts to conduct with a bias current, which lowers the bias of the base of the discharge transistor Q3, reduces the conduction degree of Q3, and thus reduces the discharge current of Q3, keeping the discharge current of Q3 constant at a certain value (the specific constant current value is determined by the values ​​of R4 and ZD1).

[0028] Once the voltage across electrolytic capacitor EC1 is discharged, the circuit completes its discharge function and shuts down. When the mains power is restored, as C1 returns to a high level, as mentioned earlier, Q1, Q2, and Q3 do not operate. The discharge circuit operates without loss and does not affect the normal operation of subsequent circuits.

[0029] Furthermore, the above provides a more energy-efficient discharge technology that discharges rapidly, with a stable and controllable discharge current. The high-voltage bus capacitor does not require a fixed discharge resistor, thus avoiding losses in the circuit due to the discharge resistor.

[0030] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An electrolytic capacitor discharge circuit, characterized in that, include: The circuit includes an input circuit, a rectifier and filter circuit, a constant current discharge circuit, and a discharge shutdown circuit. The front end of the input circuit is connected to the mains power input L terminal and N terminal, and the rear end of the input circuit is connected to the rectifier and filter circuit. The input circuit includes a fuse, a first filter capacitor, a second filter capacitor, and a common-mode inductor. The fuse is connected to the mains input terminal, and the first filter capacitor, the second filter capacitor, and the common-mode inductor are connected together. The rectifier and filter circuit includes a rectifier bridge and a filter capacitor. The front end of the rectifier bridge is connected to the input circuit, and the rear end of the rectifier bridge is connected to the filter capacitor. The constant current discharge circuit includes a first resistor, a third resistor, a fourth resistor, a first transistor, a second transistor, a discharge transistor, and a Zener diode; the first resistor and the third resistor are bias resistors for the discharge transistor, and the fourth resistor is a current sensing resistor; The discharge shutdown circuit includes a first rectifier diode, a second rectifier diode, a second resistor, and a capacitor C1; the second resistor provides a discharge path for the capacitor.

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