Control circuit for preventing power supply starting overshoot

Abstract

The utility model discloses a control circuit for preventing power supply starting overshoot, which comprises a power factor correction circuit, and the power factor correction circuit comprises an acquisition unit which is used for measuring current or voltage and feeding back information to a control unit so as to control the working state of the circuit; the acquisition unit adopts a resistance voltage division network to sample the direct current voltage output by the boost transformation unit; the resistance voltage dividing network is divided into an upper half resistor and a lower half resistor; the acquisition unit is also provided with an anti-overshoot circuit, the circuit comprises a capacitor element, and the capacitor element is connected in parallel at a half or one third position of the upper half resistor. At the starting moment of the power supply, the newly-added capacitor is rapidly charged to form a short-circuit state, thereby reducing the effective resistance value of the divider resistor, enabling the sampling voltage to reach a preset threshold value in advance, and promoting the control circuit to stop the boosting action in time. When the capacitor is fully charged, the capacitor becomes an open-circuit state, and voltage sampling and voltage stabilization setting during normal work are not affected.

Description

Technical Field

[0001] The utility model relates to the field of control circuit design, in particular to a control circuit for preventing overshoot at power startup. Background Art

[0002] The bipolar switching power supply is a precision-structured power conversion device, and its architecture is mainly divided into two key parts: the front-end part is the power factor correction (PFC) circuit, and the back-end part is to transform the 420-volt DC voltage into different low-voltage DC outputs for users. Among them, the power factor correction circuit is responsible for handling a wide range of AC input voltages, such as the common 110 volts to 277 volts AC. During operation, the PFC circuit first rectifies these AC voltages into DC, and then uses advanced switching technology and integrated controller ICs to coordinate boost inductors, high-speed boost diodes, large-capacity electrolytic capacitors, and other auxiliary capacitors and resistors to efficiently increase the DC voltage to approximately 420 volts. At the same time, it significantly improves the power factor of the entire system to the power grid, reduces reactive power consumption, and meets energy efficiency standards.

[0003] However, in practical applications, even with today's mainstream PFC IC solutions and their supporting peripheral circuits, it is often difficult to completely avoid a certain degree of overshoot voltage during the startup boost phase during the debugging process. This phenomenon may cause transient spike voltages to reach 8%-10% of the original set voltage. Such excessively high voltage peaks will not only shorten the service life of key components in the circuit, but may also cause unexpected failures, posing a threat to the stability of the power system.

[0004] In summary, it is found that the prior art has at least the following technical problems:

[0005] The existing peripheral control circuit has an overshoot voltage of 8%-10% when the power is started, which may cause damage to circuit components. Utility Model Content

[0006] In view of this, the utility model aims to provide a control circuit for preventing overshoot at power startup, so as to solve the problems existing in the above-mentioned background technology.

[0007] In order to solve the above technical problems, the technical solution of the utility model is a control circuit for preventing power supply startup overshoot, characterized in that: it includes a power factor correction circuit of the front pole, and the power factor correction circuit includes: a rectifier and filter unit, which is used to convert AC input into DC power; a boost transformer unit, which is used to increase the low voltage output by the rectifier and filter unit to a high voltage; a control unit, which is used to monitor and control the startup and operation status of the circuit; a collection unit, which is used to measure the current or voltage and feed back the information to the control unit to control the working status of the circuit; the collection unit uses a resistor divider network to sample the DC voltage output by the boost transformer unit; the resistor divider network is divided into an upper half resistor and a lower half resistor; the collection unit is also provided with an anti-overshoot circuit, which includes a capacitor element, and the capacitor is connected in parallel at a half or a third position of the upper half resistor.

[0008] Preferably, the anti-overshoot circuit is formed by the upper half resistor and the capacitor connected in parallel therewith, thereby forming a functional circuit structure capable of suppressing overshoot voltage during startup.

[0009] Preferably, the rectification and filtering unit is composed of a rectifier and a filter, and the rectification and filtering unit can rectify and filter an AC voltage of 100 volts to 277 volts into a DC voltage.

[0010] Preferably, the step-up transformer unit includes a step-up transformer, and the step-up transformer unit increases the DC voltage output by the rectifier and filter unit to a DC voltage of 420 volts.

[0011] Preferably, it also includes a transformer output circuit at the rear pole, which converts the 420V DC voltage output by the power factor correction circuit into low-voltage DC power of different voltage levels.

[0012] The technical effects of the utility model are mainly reflected in the following aspects: the control circuit sampling unit adopts the method of resistor voltage division to sample 420V; by adding a capacitor element in parallel to a part of the resistors in the resistor voltage division network. At the moment of power startup, the newly added capacitor is quickly charged to form a short-circuit state, thereby reducing the effective resistance of the voltage-dividing resistor, so that the sampling voltage reaches the preset threshold in advance, prompting the control circuit to stop the boost action in time; when the capacitor is fully charged, it becomes an open circuit state, which does not affect the voltage sampling and voltage regulation settings during normal operation. The power supply is soft-started, and the peak voltage is effectively suppressed during startup, making the boost process smoother, effectively reducing the voltage impact on the electrolytic capacitor and other components, reducing the manufacturing cost, and also enhancing the reliability and stability of the entire power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1This is a principle structure block diagram of a control circuit for preventing overshoot at power startup in the utility model;

[0014] Figure 2 This is an application example diagram of a control circuit for preventing overshoot at power startup of the utility model;

[0015] Figure 3 for Figure 2 Schematic diagram of the anti-overshoot circuit;

[0016] In the figure: 1. power factor correction circuit, 11. rectifier filter unit, 12. boost transformer unit, 13. control unit, 14. acquisition unit, 141. lower half resistor, 142. anti-overshoot circuit; 2. transformer output circuit. DETAILED DESCRIPTION

[0017] The specific implementation modes of the present invention are further described below in conjunction with the accompanying drawings to make the technical solutions of the present invention easier to understand and grasp.

[0018] In this embodiment, it should be understood that the terms "middle", "upper", "lower", "top", "right", "left end", "above", "back", "middle", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0019] In addition, in this specific embodiment, if the connection or fixing method between components is not specifically described, the connection or fixing method can be through bolt fixing or pin fixing, or pin shaft connection and the like commonly used in the prior art, and therefore, it is not described in detail in this embodiment.

[0020] Terminology explanation:

[0021] PFC: Power Factor Correction Power factor is an important technical data of the power system. Power factor is a coefficient to measure the efficiency of electrical equipment. A low power factor means that the reactive power used by the circuit for alternating magnetic field conversion is large, which reduces the utilization rate of the equipment and increases the line power supply loss. In an AC circuit, the cosine of the phase difference between voltage and current is called the power factor.

[0022] IC: Integrated Circuit

[0023] See also Figure 1-2A control circuit for preventing overshoot at power startup includes a power factor correction circuit 1 of the front pole, wherein the power factor correction circuit 1 includes: a rectifier and filter unit 11, which is used to convert AC input into DC power; the rectifier and filter unit 11 is composed of a rectifier and a filter, and the rectifier and filter unit 11 can rectify and filter the AC voltage of 100 volts to 277 volts into DC power. A boost transformer unit 12 is used to increase the low voltage output by the rectifier and filter unit 11 to a high voltage; the boost transformer unit 12 includes a boost transformer, and the boost transformer unit 12 increases the DC voltage output by the rectifier and filter unit 11 to a DC voltage of 420 volts. The control unit 13 is used to monitor and control the startup and operation status of the circuit; the acquisition unit 14 is used to measure the current or voltage and feed back the information to the control unit 13 to control the working status of the circuit; the acquisition unit 14 uses a resistor voltage divider network to sample the DC voltage output by the boost transformer 12; the resistor voltage divider network is divided into an upper resistor and a lower resistor 141; the acquisition unit 14 is also provided with an anti-overshoot circuit 142, which includes a capacitor element, which is connected in parallel at one-half or one-third of the upper resistor. The anti-overshoot circuit 142 is formed by the upper resistor and the capacitor connected in parallel thereto to form a functional circuit structure that can suppress overshoot voltage at startup. The sampling unit samples 420V by resistor voltage division; by adding a capacitor element in parallel to a part of the resistors in the resistor voltage divider network. At the moment of power startup, the newly added capacitor is quickly charged to form a short-circuit state, thereby reducing the effective resistance of the voltage divider resistor, so that the sampled voltage reaches the preset threshold in advance, prompting the control circuit to stop the boost action in time. When the capacitor is fully charged, it becomes an open circuit state, which does not affect the voltage sampling and voltage stabilization settings during normal operation. It also includes a transformer output circuit 2 at the rear pole, which converts the 420V DC voltage output by the power factor correction circuit 1 into low-voltage DC power of different voltage levels to supply power to user loads.

[0024] The specific process is as follows: In the power startup stage, since the charge amount of the capacitor is zero in the initial state, it shows low impedance, which is equivalent to short-circuiting a part of the upper resistor, thereby reducing the overall voltage division ratio, so that the sampling voltage can reach the preset threshold before reaching 420 volts, thereby triggering the control circuit to stop continuing to boost, effectively preventing the occurrence of overshoot. As the power starts and the capacitor is charged, the capacitor gradually presents a high impedance state until it is approximately open circuit, at which time it no longer affects the resistor voltage division ratio, the sampling circuit returns to normal, and maintains stable voltage sampling after startup. Such a design ensures a smooth transition of the startup process, avoids voltage shocks to the internal components of the power supply, especially the electrolytic capacitor, and improves the safety and service life of the system. The role of the lower half resistor 141 is to form a voltage division network together with the upper half resistor to ensure that the actual value of the 420-volt DC voltage can be accurately reflected in the non-startup stage.

[0025] Specifically, the rated input voltage of the front-stage circuit is an AC voltage of 100V to 277V. The boost needs to be set to 420V to meet the requirement. The existing conventional electrolytic capacitors have a withstand voltage of 400V, 450V or 500V; originally, electrolytic capacitors with a withstand voltage of 450V could be selected. However, the traditional IC solution will have an overshoot of 8%-10%, that is, 420V*(1+8%)=453.6V; so that the traditional IC solution can only choose electrolytic capacitors with a withstand voltage of 500V, resulting in a higher manufacturing cost of the bipolar switching power supply.

[0026] In this regard, the control circuit adopts the method of adding a capacitor element in parallel to a part of the resistors in the resistor voltage divider network for sampling of 420 volt DC voltage. At the moment of power supply startup, the newly added capacitor is quickly charged to form a short-circuit state, thereby reducing the effective resistance of the voltage divider resistor, so that the sampling voltage reaches the preset threshold in advance, prompting the control circuit to stop the boost action in time. When the capacitor is fully charged, it becomes an open circuit state, which does not affect the voltage sampling and voltage regulation settings during normal operation. The transient voltage that may originally cause 453.6 volts (i.e., 8% overshoot on the basis of 420 volts) is reduced to 434.7 volts or lower, so that a cost-effective 450 volt withstand voltage grade electrolytic capacitor can be selected instead of a more expensive and uncommon 500 volt grade product. The power supply is soft-started, and the peak voltage is effectively suppressed during startup, making the boost process smoother, effectively reducing the voltage impact on the electrolytic capacitor and other components, reducing the manufacturing cost, and also enhancing the reliability and stability of the entire power supply system.

[0027] The technical effects of the utility model are mainly reflected in the following aspects: the control circuit sampling unit adopts the method of resistor voltage division to sample 420V; by adding a capacitor element in parallel to a part of the resistors in the resistor voltage division network. At the moment of power startup, the newly added capacitor is quickly charged to form a short-circuit state, thereby reducing the effective resistance of the voltage-dividing resistor, so that the sampling voltage reaches the preset threshold in advance, prompting the control circuit to stop the boost action in time; when the capacitor is fully charged, it becomes an open circuit state, which does not affect the voltage sampling and voltage regulation settings during normal operation. The power supply is soft-started, and the peak voltage is effectively suppressed during startup, making the boost process smoother, effectively reducing the voltage impact on the electrolytic capacitor and other components, reducing the manufacturing cost, and also enhancing the reliability and stability of the entire power supply system.

[0028] In addition, as common knowledge in the industry, the rectifier filter unit 11, the boost transformer unit 12, the control unit 13 and the acquisition unit 14 mentioned above are common knowledge, so their principles and structures will not be described in detail.

[0029] Of course, the above are only typical examples of the present invention. In addition, the present invention can also have many other specific implementation methods. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims

1. A control circuit to prevent overshoot at power startup, characterized in that: A power factor correction circuit comprising a front pole, the power factor correction circuit comprising: A rectifier and filter unit, which is used to convert AC input into DC power; A boost transformer unit, which is used to boost the low voltage output by the rectifying and filtering unit to a high voltage; A control unit, which is used to monitor and control the startup and operation status of the circuit; The acquisition unit is used to measure the current or voltage and feed back the information to the control unit so as to control the working state of the circuit; the acquisition unit adopts a resistor voltage divider network to sample the DC voltage output by the step-up transformer unit; the resistor voltage divider network is divided into an upper half resistor and a lower half resistor; the acquisition unit is also provided with an anti-overshoot circuit, which includes a capacitor element, and the capacitor is connected in parallel at the half or one-third position of the upper half resistor.

2. A control circuit for preventing overshoot at power startup as claimed in claim 1, characterized in that: The anti-overshoot circuit is formed by the upper half resistor and the capacitor connected in parallel therewith, forming a functional circuit structure capable of suppressing overshoot voltage during startup.

3. A control circuit for preventing power supply startup overshoot as claimed in claim 1, characterized in that: The rectifying and filtering unit is composed of a rectifier and a filter, and the rectifying and filtering unit can rectify and filter an AC voltage of 100 volts to 277 volts into a DC voltage.

4. A control circuit for preventing power supply startup overshoot as claimed in claim 1, characterized in that: The step-up transformer unit includes a step-up transformer, and the step-up transformer unit steps up the DC voltage output by the rectifying and filtering unit to a DC voltage of 420V.

5. A control circuit for preventing power supply startup overshoot as claimed in claim 1, characterized in that: It also includes a transformer output circuit at the rear pole, which converts the 420V DC voltage output by the power factor correction circuit into low-voltage DC power of different voltage levels.

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