AC / DC Power Supply, Rectifier Circuit and Control Method Thereof

Abstract

An AC / DC power supply, a rectification circuit and a control method thereof are disclosed. A supply voltage is generated by a filter circuit in the rectification circuit, which follows the DC pulsating voltage received by the filter circuit in a first time interval, and in a second time interval, the value of the supply voltage is greater than the value of the supply voltage at the end of the first time interval, thereby reducing the volume of the filter circuit, and further reducing the volume of the rectification circuit and improving the power density of the AC / DC power supply.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology. Specifically, it relates to an AC / DC power supply, a rectification circuit, and a control method thereof. Background Art

[0002] Currently, in the application scenarios of AC / DC without PFC requirements, a two-stage power supply architecture is generally adopted. Figure 1 The circuit block diagram of the AC / DC power supply in the prior art is shown. The front stage is a rectification circuit, including a rectifier bridge, which is used to rectify the AC input voltage Vac into a DC pulsating voltage Vbus, where the DC pulsating voltage Vbus is the absolute value of the AC input voltage Vac. A capacitor C is connected in parallel at the output end of the rectifier bridge to generate a supply voltage Vin. The rear stage is a DC / DC converter, which is used to convert the supply voltage Vin into the required voltage level. Figure 2 The working waveform diagram of the rectification circuit in the prior art is shown. As Figure 2 shown, at time t0, the DC pulsating voltage Vbus rises to the voltage of the capacitor C (i.e., the supply voltage Vin). Thereafter, during the period from t0 to t1, the rectifier bridge conducts, and the supply voltage Vin follows the change of the DC pulsating voltage Vbus. The AC input voltage Vac charges the capacitor C and at the same time provides energy to the rear stage. At time t1, the DC pulsating voltage Vbus drops to equal the supply voltage Vin. Thereafter, during the period from t1 to t2, the rectifier bridge turns off, and the capacitor C discharges to provide energy to the rear stage, so that the supply voltage Vin linearly drops and equals the DC pulsating voltage Vbus at time t2. Thereafter, the rectifier bridge conducts again, repeating the above process. In the above process, the AC input voltage Vac only provides energy to the rear stage during the period from t0 to t1. In this application scenario, the supply voltage Vin needs to be within a certain range to ensure the normal operation of the rear-stage DC / DC converter. On the one hand, in order to meet the voltage requirements under low-voltage input full load, a capacitor with a relatively large capacitance value is often required. On the other hand, in order to meet the withstand voltage requirements under high-voltage input, a capacitor with a relatively high withstand voltage is often required. The large capacitance value and high withstand voltage result in a relatively large volume of this capacitor, and ultimately lead to a relatively large volume of the AC / DC power supply, reducing the power density of the AC / DC power supply. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to set the working mode of the filter circuit in the rectification circuit according to the rectified DC pulsating voltage, thereby reducing the volume of the filter circuit, and further reducing the volume of the rectification circuit, and improving the power density of the AC / DC power supply.

[0004] According to the first aspect of the present invention, a rectification circuit is proposed, including:

[0005] A filtering circuit is used to receive a DC pulsating voltage and generate a supply voltage. During a first time interval, the waveform of the supply voltage follows the DC pulsating voltage; during a second time interval, the value of the supply voltage is greater than the value of the supply voltage at the end of the first time interval, thereby reducing the volume of the filtering circuit.

[0006] Further, during the second time interval, the value of the supply voltage is less than or equal to the peak value of the minimum DC pulsating voltage.

[0007] Further, during a first part of the first time interval, the filtering circuit is in a first operating mode, and during a second part of the first time interval and the second time interval, the filtering circuit is in a second operating mode.

[0008] Further, in the first operating mode, the filtering circuit has a first capacitance value; in the second operating mode, the filtering circuit has a second capacitance value, where the second capacitance value is greater than the first capacitance value.

[0009] Further, the DC pulsating voltage supplies energy to the subsequent circuit of the rectifying circuit during the first time interval.

[0010] Further, the first part of the first time interval starts when the DC pulsating voltage rises to a second threshold and ends when it drops to a first threshold, and the second part of the first time interval starts when the DC pulsating voltage rises to the supply voltage and ends when it rises to the second threshold.

[0011] Further, the second time interval starts when the DC pulsating voltage drops to the first threshold and ends until it rises to the supply voltage.

[0012] Further, the second threshold is greater than the first threshold and less than or equal to the peak value of the minimum DC pulsating voltage.

[0013] Further, the filtering circuit includes:

[0014] A first capacitor, connected in parallel at the input end of the filtering circuit; and

[0015] A second capacitor, selectively connected in parallel at the input end of the filtering circuit, and the capacitance value of the second capacitor is greater than the capacitance value of the first capacitor.

[0016] Further, during the second part of the first time interval and the second time interval, the first capacitor and the second capacitor are connected in parallel together.

[0017] Further, in the first part of the first time interval, the second capacitor is disconnected from the first capacitor.

[0018] Further, the filter circuit further includes:

[0019] A first switch, connected in series with the second capacitor, to selectively connect the second capacitor to the input end of the filter circuit.

[0020] Further, when the DC pulsating voltage drops to a first threshold value, the first switch is controlled to conduct, so as to connect the first capacitor in parallel at the input end of the filter circuit.

[0021] Further, when the DC pulsating voltage rises to a second threshold value, the first switch is controlled to turn off, so as to disconnect the connection between the first capacitor and the input end of the filter circuit.

[0022] Further, the rectifier circuit further includes:

[0023] A rectification unit, configured to receive an AC input voltage and output a DC pulsating voltage.

[0024] According to a second aspect of the present invention, an AC / DC power supply is provided, including:

[0025] The rectifier circuit according to any one of the above; and

[0026] A DC / DC converter, configured to convert the supply voltage into a desired voltage level for supplying to a load.

[0027] According to a third aspect of the present invention, a control method for controlling a rectifier circuit is provided, including:

[0028] Generating a supply voltage according to the rectified DC pulsating voltage, wherein in a first time interval, the waveform of the supply voltage follows the DC pulsating voltage; in a second time interval, the value of the supply voltage is greater than the value of the supply voltage at the end of the first time interval, so as to reduce the volume of the filter circuit.

[0029] Further, the control method further includes:

[0030] In the first part of the first time interval, the filter circuit generates a first capacitance value to receive the DC pulsating voltage;

[0031] In the second time interval and the second part of the first time interval, the filter circuit generates a second capacitance value to receive the DC pulsating voltage, wherein the second capacitance value is greater than the first capacitance value.

[0032] Further, the first part of the first time interval starts when the DC pulsating voltage rises to the second threshold and ends when it drops to the first threshold, and the second part of the first time interval starts when the DC pulsating voltage rises to the supply voltage and ends when it rises to the second threshold; the second time interval starts when the DC pulsating voltage drops to the first threshold and ends until it rises to the supply voltage.

[0033] Further, the second threshold is greater than the first threshold and less than or equal to the peak value of the minimum DC pulsating voltage.

[0034] In summary, a supply voltage is generated by the filter circuit in the rectifier circuit. It follows the DC pulsating voltage received by the filter circuit within the first time interval. Within the second time interval, the value of the supply voltage is greater than the value of the supply voltage at the end of the first time interval, thereby reducing the volume of the filter circuit, and further reducing the volume of the rectifier circuit, and improving the power density of the AC / DC power supply. Description of the Drawings

[0035] Through the following description of the embodiments of the present invention with reference to the drawings, the above and other objects, features, and advantages of the present invention will become clearer. In the drawings:

[0036] Figure 1 is the circuit diagram of the AC / DC power supply in the prior art;

[0037] Figure 2 is the working waveform diagram of the rectifier circuit in the prior art;

[0038] Figure 3 is the circuit diagram of the AC / DC power supply according to the embodiment of the present invention;

[0039] Figure 4 is the working waveform diagram of the rectifier circuit according to the embodiment of the present invention; and

[0040] Figure 5 is the flowchart of the control method of the rectifier circuit according to the embodiment of the present invention. Detailed Embodiments

[0041] The following describes the present invention based on embodiments, but the present invention is not limited to these embodiments. In the following detailed description of the present invention, some specific details are described in detail. Those skilled in the art can fully understand the present invention without the description of these details. In order to avoid obscuring the essence of the present invention, well-known methods, processes, flows, elements, and circuits are not described in detail.

[0042] In addition, those of ordinary skill in the art should understand that the drawings provided here are all for illustrative purposes, and the drawings are not necessarily drawn to scale.

[0043] Meanwhile, it should be understood that in the following description, "circuit" refers to a conductive loop formed by at least one component or sub-circuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "connected to" another element or when an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. In contrast, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between the two.

[0044] Unless the context clearly requires otherwise, the words such as "comprising", "including" and the like in the whole specification and claims should be interpreted in an inclusive sense rather than an exclusive or exhaustive sense; that is, it is the meaning of "including but not limited to".

[0045] In the description of the present invention, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0046] Figure 3 It is a circuit block diagram of the AC / DC power supply according to an embodiment of the present invention. As Figure 3 shown, the front stage is a rectification circuit 1, and the rear stage is a DC / DC converter 2. The rectification circuit 1 includes a rectification unit 11 and a filtering circuit 12. The rectification unit 11 is used to receive the AC input voltage Vac and rectify it into a DC pulsating voltage Vbus, where the DC pulsating voltage Vbus is the absolute value of the AC input voltage Vac. Specifically, the rectification unit 11 includes four diodes constituting a bridge rectification. It can be understood that the four diodes can also be partially or completely replaced by power tubes. The rectification unit 11 can also include other circuits with rectification functions such as a bridgeless LLC circuit, which will not be described restrictively here.

[0047] The filter circuit 12 is connected to the output terminal of the rectification unit 11 to receive the DC pulsating voltage Vbus and generate a supply voltage Vin to supply the subsequent DC / DC converter. Among them, within the first time interval, the waveform of the supply voltage Vin follows the DC pulsating voltage Vbus; within the second time interval, the value of the supply voltage Vin is greater than the value of the supply voltage Vin at the end of the first time interval, thereby reducing the volume of the filter circuit 12. At the same time, within the second time interval, the supply voltage Vin is less than or equal to the peak value of the minimum DC pulsating voltage Vbus. Specifically, the filter circuit 12 has two operating modes. In the first part of the first time interval, the filter circuit 12 is in the first operating mode; in the second part of the first time interval and the second time interval, the filter circuit 12 is in the second operating mode. In the first operating mode, the filter circuit 12 has a first capacitance value; in the second operating mode, the filter circuit 12 has a second capacitance value, where the second capacitance value is greater than the first capacitance value. In this embodiment, the first part of the first time interval starts when the DC pulsating voltage Vbus rises to the second threshold Vth2 and ends when it drops to the first threshold Vth1. The second part of the first time interval starts when the DC pulsating voltage Vbus rises to the supply voltage Vin and ends when it rises to the second threshold Vth2. The second time interval starts when the DC pulsating voltage Vbus drops to the first threshold Vth1 and ends until it rises to the supply voltage Vbus. Among them, the first threshold Vth1 can be set according to the minimum operating voltage of the subsequent circuit. The second threshold Vth2 is greater than the first threshold Vth1 and not greater than the peak value of the minimum DC pulsating voltage Vbus.

[0048] In this embodiment, the filter circuit 12 includes a first capacitor C1 and a second capacitor C2, and the capacitance value of the second capacitor C2 is much larger than that of the first capacitor C1. Among them, the first capacitor C1 is connected in parallel to the input terminal of the filter circuit 12, and the second capacitor C2 is selectively connected in parallel with the first capacitor C1. That is, the first capacitor C1 is independently connected in parallel to the input terminal of the filter circuit 12 in the first operating mode; in the second operating mode, the first capacitor C1 and the second capacitor C2 are jointly connected in parallel to the input terminal of the filter circuit 12.

[0049] The filter circuit 12 further includes a switch S, which is connected in series with the second capacitor C2 to selectively connect the second capacitor C2 in parallel to the input terminal of the filter circuit 12. The switch S is controlled to turn off in the first operating mode and controlled to turn on in the second operating mode. It should be understood that only one implementation manner of the filter circuit is given in the embodiment of the present invention, and any other circuit that can implement this function is within the protection scope of the present invention. For example, a switch can also be connected in series with the first capacitor. This switch conducts in the first working stage and turns off or conducts in the second working stage, which will not affect the circuit effect either.

[0050] The working process of the rectifier circuit will be specifically described below in conjunction with the working waveform diagram.

[0051] Figure 4 The working waveform diagram of the rectifier circuit according to the embodiment of the present invention is shown. As Figure 4 shown, the DC pulsating voltage Vbus rises to the second threshold Vth2 at time t0. Thereafter, the filter circuit starts to enter the first working mode. The switch S is controlled to turn off, that is, only the first capacitor C1 is connected in parallel at the input end of the filter circuit 12. During the period from t0 to t1 (i.e., the first part of the first time interval), since the capacitance value of the first capacitor C1 is small, the supply voltage Vin follows the change of the DC pulsating voltage Vbus. At this time, the first capacitor C1 and the AC input voltage Vac jointly supply energy to the subsequent stage. After the DC pulsating voltage Vbus rises to the peak value, it starts to decline. At time t1, it drops to the first threshold Vth1, and thus the first part of the first time interval ends. Thereafter, the filter circuit 12 enters the second working mode, and the switch S is controlled to turn on to connect the second capacitor C2 in parallel at the input end of the filter circuit 12. Since the capacitance value of the second capacitor C2 is much larger than that of the first capacitor C1, the supply voltage Vin instantaneously rises to approximately equal to the voltage across the second capacitor C2, that is, the second threshold Vth2. During the period from t1 to t2 (i.e., the second time interval), since the supply voltage Vin is greater than the DC pulsating voltage Vbus, the rectifier unit 11 is turned off. Therefore, the first capacitor C1 and the second capacitor C2 jointly supply energy to the subsequent stage, and the supply voltage Vin also linearly decreases as the capacitor discharges. During this period, the DC pulsating voltage Vbus drops to zero and then rises. At time t2, it rises to be equal to the supply voltage Vin, and thus the second time interval ends. Thereafter, the rectifier unit 11 is turned on. During the period from t2 to t3 (i.e., the second part of the first time interval), the filter circuit 12 is still in the second working mode. The AC input voltage Vac charges the first capacitor C1 and the second capacitor C2 on the one hand, and supplies energy to the subsequent stage on the other hand. The DC pulsating voltage Vbus continues to rise. At time t3, it is greater than the second threshold Vth2, and thus the second part of the first time interval ends. Thereafter, the filter circuit enters the first working mode, and the switch S is controlled to turn off. At this time, the voltage value across the second capacitor C2 is Vth2, that is, the maximum voltage value borne by the second capacitor C2 is the second threshold Vth2.

[0052] Thus, in this embodiment, the AC input voltage Vac supplies energy to the subsequent stage during both the first part t0 - t1 and the second part t2 - t3 of the first time interval. That is, the time during which the AC input voltage Vac supplies energy to the subsequent stage in each cycle is Figure 2 greatly extended compared with Figure 2Since the capacitor C has been connected in parallel to the output terminal of the rectifier circuit all the time, the withstand voltage value of the capacitor is equal to the peak value of the maximum DC pulsating voltage. In this embodiment, the withstand voltage value of the second capacitor C2 is the second threshold Vth2, which is also equal to the peak value of the minimum DC pulsating voltage. It should be understood that the peak value of the maximum DC pulsating voltage and the peak value of the minimum DC pulsating voltage here refer to the AC input voltages of different voltage levels received by the rectifier circuit. Therefore, the DC pulsating voltage has different voltage ranges. For example, in order to meet different load requirements, the AC input voltage that the AC / DC power supply can receive is between 110V - 220V. Therefore, the peak value of the maximum DC pulsating voltage is 220V, and the peak value of the minimum DC pulsating voltage is 110V. According to the rectifier circuit in the prior art, the maximum voltage value that the required capacitor bears is 220V, while according to the rectifier circuit of the present invention, the maximum voltage value that the second capacitor bears is 110V. Therefore, the volume of the second capacitor is reduced. In addition, although the withstand voltage value of the first capacitor is still 220V, its capacitance value is very small, so its volume is very small.

[0053] Figure 5 The flowchart of the control method of the rectifier circuit according to the embodiment of the present invention is as follows. The method includes:

[0054] Generate a supply voltage according to the rectified DC pulsating voltage, wherein in the first time interval, the waveform of the supply voltage follows the DC pulsating voltage; in the second time interval, the value of the supply voltage is greater than the value of the supply voltage at the end of the first time interval, thereby reducing the volume of the filter circuit.

[0055] Specifically, in the first part of the first time interval, the filter circuit generates a first capacitance value to receive the DC pulsating voltage.

[0056] In the second time interval and the second part of the first time interval, the filter circuit generates a second capacitance value to receive the DC pulsating voltage, wherein the second capacitance value is greater than the first capacitance value.

[0057] Wherein, the first part of the first time interval starts from when the DC pulsating voltage rises to the second threshold and ends when it drops to the first threshold; the second part of the first time interval starts from when the DC pulsating voltage rises to the supply voltage and ends when it rises to the second threshold; the second time interval starts from when the DC pulsating voltage drops to the first threshold and ends until it rises to the supply voltage. The second threshold is greater than the first threshold and less than or equal to the peak value of the minimum DC pulsating voltage.

[0058] In summary, in the rectifier circuit of the present invention, the supply voltage generated by the filter circuit follows the DC pulsating voltage received by the filter circuit in the first time interval. In the second time interval, the value of the supply voltage is greater than the value of the supply voltage at the end of the first time interval, thereby reducing the volume of the filter circuit, further reducing the volume of the rectifier circuit, and improving the power density of the AC / DC power supply.

[0059] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A rectifier circuit, characterized in that, Comprising: A filtering circuit for receiving a DC pulsating voltage and generating a supply voltage input to a subsequent circuit, wherein in a first time interval, the waveform of the supply voltage follows the DC pulsating voltage; in a second time interval, the value of the supply voltage is greater than the value of the supply voltage at the end of the first time interval, thereby reducing the volume of the filtering circuit; Wherein, the filtering circuit includes a second capacitor, when the DC pulsating voltage drops to a first threshold, the second capacitor is connected in parallel to the input end of the filtering circuit; when the DC pulsating voltage rises to a second threshold, the connection between the second capacitor and the input end of the filtering circuit is disconnected.

2. The rectifier circuit according to claim 1, wherein In the second time interval, the value of the supply voltage is less than or equal to the peak value of the minimum DC pulsating voltage.

3. The rectifier circuit according to claim 1, characterized in that In the first part of the first time interval, the filtering circuit is in a first operating mode, and in the second part of the first time interval and the second time interval, the filtering circuit is in a second operating mode.

4. The rectifier circuit according to claim 3, wherein In the first operating mode, the filtering circuit has a first capacitance value; in the second operating mode, the filtering circuit has a second capacitance value, wherein the second capacitance value is greater than the first capacitance value.

5. The rectifier circuit according to claim 1, characterized in that The DC pulsating voltage supplies energy to the subsequent circuit of the rectifying circuit in the first time interval.

6. The rectifier circuit according to claim 3, wherein The first part of the first time interval starts when the DC pulsating voltage rises to the second threshold and ends when it drops to the first threshold, and the second part of the first time interval starts when the DC pulsating voltage rises to the supply voltage and ends when it rises to the second threshold.

7. The rectifier circuit according to claim 6, wherein The second time interval starts when the DC pulsating voltage drops to the first threshold and ends until it rises to the supply voltage.

8. The rectifier circuit according to claim 7, characterized in that The second threshold is greater than the first threshold and less than or equal to the peak value of the minimum DC pulsating voltage.

9. The rectifier circuit according to claim 1, wherein The filtering circuit includes: A first capacitor connected in parallel to the input end of the filtering circuit; and A second capacitor selectively connected in parallel to the input end of the filtering circuit, and the capacitance value of the second capacitor is greater than the capacitance value of the first capacitor.

10. The rectifier circuit according to claim 9, characterized in that, In the second part of the first time interval and the second time interval, the first capacitor and the second capacitor are connected in parallel together.

11. The rectifier circuit according to claim 9, characterized in that, In the first part of the first time interval, the second capacitor is disconnected from the first capacitor.

12. The rectifier circuit according to claim 9, wherein, The filtering circuit further includes: A first switch connected in series with the second capacitor to selectively connect the second capacitor to the input end of the filtering circuit.

13. The rectifier circuit according to claim 12, characterized in that, When the DC pulsating voltage drops to the first threshold, the first switch is controlled to conduct to connect the second capacitor in parallel to the input end of the filtering circuit.

14. The rectifier circuit according to claim 12, characterized in that, When the DC pulsating voltage rises to the second threshold, the first switch is controlled to turn off to disconnect the connection between the second capacitor and the input end of the filtering circuit.

15. The rectifier circuit according to claim 1, characterized in that, Further comprising: A rectifying unit for receiving an AC input voltage and outputting a DC pulsating voltage.

16. An AC / DC power supply, characterized in that, Comprising: The rectifying circuit according to any one of claims 1-15; and A DC / DC converter for converting the supply voltage into a desired voltage level to supply to a load.

17. A control method for controlling a rectifier circuit, characterized in that, Comprising: Generate a supply voltage input to the subsequent stage circuit based on the rectified DC pulsating voltage, where within the first time interval, the waveform of the supply voltage follows the DC pulsating voltage; Within the second time interval, the value of the supply voltage is greater than the value of the supply voltage at the end of the first time interval, thereby reducing the volume of the filter circuit; When the DC pulsating voltage drops to the first threshold, connect a second capacitor in parallel to the input end of the filter circuit; when the DC pulsating voltage rises to the second threshold, disconnect the connection between the second capacitor and the input end of the filter circuit.

18. The control method according to claim 17, characterized in that, It further includes: In the first part of the first time interval, the filter circuit generates a first capacitance value to receive the DC pulsating voltage; In the second time interval and the second part of the first time interval, the filter circuit generates a second capacitance value to receive the DC pulsating voltage, where the second capacitance value is greater than the first capacitance value.

19. The control method according to claim 18, characterized in that, The first part of the first time interval starts when the DC pulsating voltage rises to the second threshold and ends when it drops to the first threshold, and the second part of the first time interval starts when the DC pulsating voltage rises to the supply voltage and ends when it rises to the second threshold; the second time interval starts when the DC pulsating voltage drops to the first threshold and ends until it rises to the supply voltage.

20. The control method according to claim 19, wherein The second threshold is greater than the first threshold and less than or equal to the peak value of the minimum DC pulsating voltage.

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