Automatic voltage-sharing circuit
By designing an automatic voltage equalization circuit, the voltage at the midpoint of the capacitor series is collected in real time and the charging and discharging is controlled, the capacitor failure problem caused by the difference in capacitance value at high working voltage is solved, and the voltage equalization and protection of the capacitor is realized, reducing static losses and costs.
Patent Information
- Application Number
- CN202421610367.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-09
- Publication Date
- 2025-05-23
- Estimated Expiration
- 2034-07-09
AI Technical Summary
In switching power supplies, the capacitance values of the capacitors connected in series at high operating voltages vary greatly, resulting in the operating voltage that a single capacitor bears higher than its rated voltage, which may lead to the capacitance failure or explosion.
An automatic voltage equalization circuit is designed to collect the voltage at the midpoint of the capacitor series through the voltage equalization charge and discharge module and the voltage acquisition module in real time, and the control switch realizes the charge and discharge of the controlled capacitor to ensure the voltage equalization of the capacitor.
The voltage equalization between the series capacitors is realized, the capacitor is protected, and the static loss is reduced. There are few circuit components, the control solution is simple and the cost is low.
Smart Images
Figure CN222897187U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of switch power supply, and in particular to an automatic voltage equalizing circuit. Background Art
[0002] In switching power supply devices, electrolytic capacitors are usually needed for energy storage and filtering. When the operating voltage of the switching power supply is high (for example, the voltage is 800V), multiple capacitors (for example, multiple capacitors with a rated voltage of 450V) need to be connected in series to meet working requirements. However, electrolytic capacitors usually have an accuracy of only ±20% or even lower, and the capacitance of electrolytic capacitors is greatly affected by temperature, especially at low temperatures, the capacitance of electrolytic capacitors attenuates more seriously. When the capacitance values of the capacitors in series are very different, the operating voltage of a single capacitor may be higher than its rated voltage, which will cause the capacitor to fail or even explode. Therefore, when using capacitors in series, it is necessary to ensure that the capacitor voltage is balanced. Utility Model Content
[0003] The utility model aims to provide an automatic voltage equalization circuit to realize voltage equalization between series-connected capacitors.
[0004] In order to achieve the above-mentioned purpose, the technical solution of the utility model is:
[0005] An automatic voltage balancing circuit, used to achieve voltage balancing of a first capacitor and a second capacitor, comprising a voltage balancing charging and discharging module and a voltage acquisition module, wherein the voltage balancing charging and discharging module is connected to the first capacitor and the second capacitor, and the voltage balancing charging and discharging module is connected to the voltage acquisition module;
[0006] The voltage-equalizing charge and discharge module includes a first switch, a second switch, a third capacitor and a fourth capacitor. The first end of the first capacitor is connected to the first end of the first switch, the second end of the first switch is connected to the second end of the first capacitor, the second end of the first capacitor is connected to the first end of the second capacitor, the first end of the second capacitor is connected to the second end of the second switch, and the first end of the second switch is connected to the second end of the second capacitor; the first end of the first capacitor is connected to the first end of the third capacitor, the second end of the third capacitor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is connected to the second end of the second capacitor.
[0007] Furthermore, the above-mentioned voltage-equalizing charge and discharge module also includes a first resistor and a second resistor, the first end of the first resistor is connected to the first end of the first capacitor, and the second end of the first resistor is connected to the first end of the first switch; the first end of the second switch is connected to the first end of the second resistor, and the second end of the second resistor is connected to the second end of the second capacitor.
[0008] Furthermore, the voltage acquisition module includes a first operational amplifier, a third operational amplifier and multiple resistors, the series midpoint of the third capacitor and the fourth capacitor is connected to the positive input terminal of the first operational amplifier through the third resistor, the negative input terminal of the first operational amplifier is grounded, the positive input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier through the fourth resistor, the output terminal of the first operational amplifier is connected to the negative input terminal of the third operational amplifier, the positive input terminal of the third operational amplifier is connected to the output terminal of the third operational amplifier, and the output terminal of the third operational amplifier is connected to the third terminal of the first switch and the third terminal of the second switch.
[0009] Furthermore, the voltage acquisition module further includes a seventh resistor and an eighth resistor, the output end of the third operational amplifier is connected to the third end of the first switch via the seventh resistor, and the output end of the third operational amplifier is connected to the third end of the second switch via the eighth resistor.
[0010] Furthermore, the second end of the first capacitor and the first end of the second capacitor are reference grounds.
[0011] Furthermore, the first switch and the second switch are turned on complementarily.
[0012] Furthermore, the voltage across the third capacitor is kept equal to the voltage across the fourth capacitor.
[0013] In a specific embodiment, the first switch is an NPN transistor, the first end of the first switch is a collector, the second end of the first switch is an emitter, and the third end of the first switch is a base.
[0014] In a specific embodiment, the second switch is a PNP transistor, the first end of the second switch is a collector, the second end of the second switch is an emitter, and the third end of the second switch is a base.
[0015] In a specific embodiment, the voltage acquisition module further includes a second operational amplifier, the output end of the first operational amplifier is connected to the positive input end of the second operational amplifier via a fifth resistor, the negative input end of the second operational amplifier is grounded, the positive input end of the second operational amplifier is connected to the output end of the second operational amplifier via a sixth resistor, and the output end of the second operational amplifier is connected to the negative input end of the third operational amplifier.
[0016] Beneficial effect: the utility model is an automatic voltage equalization circuit, which uses a low-capacitance high-precision capacitor as a reference capacitor, and uses the series midpoint of the controlled capacitor as a reference ground. The control signal is obtained by collecting the voltage of the series midpoint of the reference capacitor, and the switch is controlled in real time to realize the charging and discharging of the controlled capacitor, thereby realizing the automatic voltage equalization control function; when the series midpoint voltage of the controlled capacitor is kept within a certain range, the circuit stops working, reducing static loss; and the utility model has few components, a simple control scheme, and low cost. Conventional series-parallel resistor voltage equalization generally requires the resistance value of the resistor to be one-tenth of the equivalent impedance of the capacitor, which will cause large losses. In this application, only one of the series resistors is charging and discharging when working, and the resistor does not work under the condition of capacitor voltage balance. Therefore, the loss is significantly less than the conventional series resistor voltage equalization scheme.
[0017] In order to make the above features and advantages of the utility model more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 The utility model is a circuit diagram of a specific embodiment of an automatic voltage equalizing circuit.
[0019] Figure 2 for Figure 1 The actual working waveform of the circuit. DETAILED DESCRIPTION
[0020] In order to make the purpose and technical solution of the embodiment of the utility model clearer, the technical solution of the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings of the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all of the embodiments. Based on the described embodiment 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] Figure 1 This is a circuit diagram of a specific embodiment of an automatic voltage equalizing circuit of the utility model. Figure 1 As shown, capacitor C1 and capacitor C2 are large-capacitance electrolytic capacitors connected in series, which are controlled capacitors. The utility model is an automatic voltage equalization circuit comprising a voltage equalization charging and discharging module 1 and a voltage acquisition module 2. The voltage equalization charging and discharging module 1 is connected to capacitor C1 and capacitor C2, and the voltage equalization charging and discharging module 1 is connected to the voltage acquisition module 2. Among them, the midpoint of the series connection of capacitor C1 and capacitor C2 is the reference ground of the automatic voltage equalization circuit of the utility model.
[0022] Furthermore, the voltage-equalizing charge and discharge module 1 includes a switch Q1, a switch Q2, a resistor R1, a resistor R2, a capacitor C3 and a capacitor C4, the first end of the resistor R1 is connected to the first end of the capacitor C1, the second end of the resistor R1 is connected to the first end of the switch Q1, the second end of the switch Q1 is connected to the second end of the capacitor C1, the second end of the capacitor C1 is connected to the first end of the capacitor C2, the first end of the capacitor C2 is connected to the second end of the switch Q2, the first end of the switch Q2 is connected to the first end of the resistor R2, the second end of the resistor R2 is connected to the second end of the capacitor C2, the second end of the capacitor C1 and the first end of the capacitor C2 are reference grounds; the first end of the capacitor C1 is connected to the first end of the capacitor C3, the second end of the capacitor C3 is connected to the first end of the capacitor C4, and the second end of the capacitor C4 is connected to the second end of the capacitor C2.
[0023] Further, the voltage acquisition module 2 includes an operational amplifier A1, an operational amplifier A2, an operational amplifier A3 and multiple resistors, the series midpoint of the capacitor C3 and the capacitor C4 is connected to the positive input terminal of the operational amplifier A1 through the resistor R3, the negative input terminal of the operational amplifier A1 is grounded, the positive input terminal of the operational amplifier A1 is connected to the output terminal of the operational amplifier A1 through the resistor R4, the output terminal of the operational amplifier A1 is connected to the positive input terminal of the operational amplifier A2 through the resistor R5, the negative input terminal of the operational amplifier A2 is grounded, the positive input terminal of the operational amplifier A2 is connected to the output terminal of the operational amplifier A2 through the resistor R6, the output terminal of the operational amplifier A2 is connected to the negative input terminal of the operational amplifier A3, the positive input terminal of the operational amplifier A3 is connected to the output terminal of the operational amplifier A3, and the output terminal of the operational amplifier A3 is connected to the third terminal of the switch Q1 and the third terminal of the switch Q2.
[0024] The operational amplifier A1 has the same function as the operational amplifier A2, and can be simplified to one operational amplifier or multiple operational amplifiers can be provided for multi-stage amplification according to actual needs. For example, the output terminal of the operational amplifier A1 can be directly connected to the negative input terminal of the operational amplifier A3.
[0025] Furthermore, the voltage acquisition module 2 further includes a resistor R7 and a resistor R8, the output end of the operational amplifier A3 is connected to the third end of the switch Q1 through the resistor R7, and the output end of the operational amplifier A3 is connected to the third end of the switch Q2 through the resistor R8.
[0026] Furthermore, the switch Q1 and the switch Q2 are turned on complementarily.
[0027] Furthermore, capacitor C3 and capacitor C4 are low-capacitance, high-precision capacitors, and capacitor C3 and capacitor C4 are used as reference capacitors, that is, the voltage across capacitor C3 and the voltage across capacitor C4 remain equal, which is half of the total voltage.
[0028] In this specific embodiment, the switch Q1 is an NPN transistor, the first end of the switch Q1 is a collector, the second end of the switch Q1 is an emitter, and the third end of the switch Q1 is a base.
[0029] In this specific embodiment, the switch Q2 is a PNP transistor, the first end of the switch Q2 is a collector, the second end of the switch Q2 is an emitter, and the third end of the switch Q2 is a base.
[0030] Next, continue to combine Figure 1 The working principle of the utility model is introduced as follows: The voltage at the midpoint of the series connection of capacitors C3 and C4 is collected by the voltage collection module 2, compared with the reference ground, and the control signal G1 of the switch Q1 and the switch Q2 is output.
[0031] More specifically, the voltage u across capacitor C1 is C1 The voltage u across capacitor C2 C2 When they are equal, the voltage of the positive input terminal and the negative input terminal of the operational amplifier A1 are equal, the voltage acquisition module 2 does not work, and there is no static loss at this time.
[0032] When the voltage across capacitor C1 is C1 Greater than the voltage u across capacitor C2 C2 When the voltage across capacitor C2 is C2 The total voltage is less than one-half, and the operational amplifier A1 outputs a high level. After being amplified by the operational amplifiers A2 and A3, the output control signal G1 is a high level, which controls the switch Q1 to be turned on and the switch Q2 to be turned off, so that the capacitor C1 is discharged and the capacitor C2 is charged until the voltage across the capacitor C1 reaches u C1 The voltage u across capacitor C2 C2 Equalize to achieve automatic pressure equalization.
[0033] When the voltage across capacitor C1 is C1 Less than the voltage u across capacitor C2 C2 When the voltage across capacitor C2 is C2 When the total voltage is greater than one-half, the operational amplifier A1 outputs a low level. After being amplified by the operational amplifiers A2 and A3, the output control signal G1 is a low level, which controls the switch Q2 to be turned on and the switch Q1 to be turned off, so that the capacitor C2 discharges and the capacitor C1 is charged until the voltage across the capacitor C1 reaches u C1 The voltage u across capacitor C2 C2 Equalize to achieve automatic pressure equalization.
[0034] Figure 2 for Figure 1 The actual working waveform of the circuit in Figure 2 The voltage across capacitor C1 is u C1 、The voltage across capacitor C2 is u C2In the initial state, the difference is relatively large. After the automatic voltage equalization circuit of the utility model is adjusted, the voltage difference between the capacitors C1 and C2 is reduced to a smaller range, which plays a role in protecting the capacitors C1 and C2.
[0035] Although the present invention has been disclosed as above by the embodiments, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.
Claims
1. An automatic voltage balancing circuit, used to achieve voltage balancing of a first capacitor and a second capacitor, characterized in that: It includes a voltage-equalizing charging and discharging module and a voltage acquisition module, wherein the voltage-equalizing charging and discharging module is connected to the first capacitor and the second capacitor, and the voltage-equalizing charging and discharging module is connected to the voltage acquisition module; The voltage-equalizing charge and discharge module includes a first switch, a second switch, a third capacitor and a fourth capacitor. The first end of the first capacitor is connected to the first end of the first switch, the second end of the first switch is connected to the second end of the first capacitor, the second end of the first capacitor is connected to the first end of the second capacitor, the first end of the second capacitor is connected to the second end of the second switch, and the first end of the second switch is connected to the second end of the second capacitor; the first end of the first capacitor is connected to the first end of the third capacitor, the second end of the third capacitor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is connected to the second end of the second capacitor.
2. An automatic voltage equalizing circuit as claimed in claim 1, characterized in that: The voltage-equalizing charge and discharge module also includes a first resistor and a second resistor, wherein the first end of the first resistor is connected to the first end of the first capacitor, and the second end of the first resistor is connected to the first end of the first switch; the first end of the second switch is connected to the first end of the second resistor, and the second end of the second resistor is connected to the second end of the second capacitor.
3. An automatic voltage equalizing circuit as claimed in claim 2, characterized in that: The voltage acquisition module includes a first operational amplifier, a third operational amplifier and a plurality of resistors, the series midpoint of the third capacitor and the fourth capacitor is connected to the positive input terminal of the first operational amplifier through the third resistor, the negative input terminal of the first operational amplifier is grounded, the positive input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier through the fourth resistor, the output terminal of the first operational amplifier is connected to the negative input terminal of the third operational amplifier, the positive input terminal of the third operational amplifier is connected to the output terminal of the third operational amplifier, and the output terminal of the third operational amplifier is connected to the third terminal of the first switch and the third terminal of the second switch.
4. An automatic voltage equalizing circuit as claimed in claim 3, characterized in that: The voltage acquisition module also includes a seventh resistor and an eighth resistor. The output end of the third operational amplifier is connected to the third end of the first switch through the seventh resistor. The output end of the third operational amplifier is connected to the third end of the second switch through the eighth resistor.
5. An automatic voltage equalizing circuit as claimed in claim 1, characterized in that: The second end of the first capacitor and the first end of the second capacitor are reference grounds.
6. An automatic voltage equalizing circuit as claimed in claim 5, characterized in that: The first switch and the second switch are complementarily turned on.
7. An automatic voltage equalizing circuit as claimed in claim 6, characterized in that: The voltage across the third capacitor is kept equal to the voltage across the fourth capacitor.
8. An automatic voltage equalizing circuit as claimed in claim 1, characterized in that: The first switch is an NPN transistor, the first end of the first switch is a collector, the second end of the first switch is an emitter, and the third end of the first switch is a base.
9. An automatic voltage equalizing circuit as claimed in claim 8, characterized in that: The second switch is a PNP transistor, the first end of the second switch is a collector, the second end of the second switch is an emitter, and the third end of the second switch is a base.
10. An automatic voltage equalizing circuit as claimed in claim 3, characterized in that: The voltage acquisition module also includes a second operational amplifier, the output end of the first operational amplifier is connected to the positive input end of the second operational amplifier through a fifth resistor, the negative input end of the second operational amplifier is grounded, the positive input end of the second operational amplifier is connected to the output end of the second operational amplifier through a sixth resistor, and the output end of the second operational amplifier is connected to the negative input end of the third operational amplifier.