Power conversion circuit and current detection circuit

Abstract

The invention provides a power conversion circuit and a current detection circuit. The power conversion circuit comprises an upper bridge switch, a lower bridge switch, a transformer, a first capacitor and the current detection circuit. The upper bridge switch is coupled between an input voltage and a switching node. The lower bridge switch is coupled between the switching node and a ground terminal. The transformer includes a primary coil, wherein the primary coil is coupled between the switching node and the first node. The first capacitor is coupled between the first node and a ground terminal. The current detection circuit is connected in parallel with the first capacitor and comprises a second capacitor and a current detection resistor. The second capacitor is coupled to the first node. The current detection resistor is coupled between the second capacitor and the ground terminal.

Description

Technical Field

[0001] The present invention relates to a power conversion circuit and its current detection circuit, and particularly to a resistive memory circuit that shares a transistor to increase the current in the low resistance state. Background Art

[0002] Since battery life is an important indicator in mobile devices, the power supply efficiency has become an important parameter in mobile devices. Coupled with the continuous innovation of the related technologies of switched-mode power conversion circuits, the power conversion efficiency has been pushed to an unprecedented level.

[0003] The flyback voltage converter is a voltage conversion circuit generated by changing the buck–boost converter. After replacing the single-winding inductor of the buck–boost converter with a two-winding transformer, the output voltage is generated after rectification by a rectification unit (such as a diode). However, in order to accurately control the flyback voltage converter, it is necessary to detect the current flowing through the primary coil of the transformer to achieve the best conversion efficiency of the flyback voltage converter. Summary of the Invention

[0004] The present invention proposes a power conversion circuit and its current detection circuit. By mapping a small current of a path beside the path of a large current, it not only helps to significantly reduce the power loss caused by the current detection resistor, but also can reduce the component cost and the circuit area, and the accuracy of the circuit detection is also maintained.

[0005] In view of this, the present invention proposes a power conversion circuit, including an upper bridge switch, a lower bridge switch, a transformer, a first capacitor, and a current detection circuit. The upper bridge switch is coupled between an input voltage and a switching node. The lower bridge switch is coupled between the switching node and a ground terminal. The transformer includes a primary coil, and the primary coil is coupled between the switching node and a first node. The first capacitor is coupled between the first node and the ground terminal. The current detection circuit is connected in parallel with the first capacitor and includes a second capacitor and a current detection resistor. The second capacitor is coupled to the first node. The current detection resistor is coupled between the second capacitor and the ground terminal.

[0006] According to an embodiment of the present invention, the power conversion circuit is an asynchronous half-bridge flyback converter. The power conversion circuit obtains the current flowing through the transformer and the first capacitor according to the voltage across the current detection resistor.

[0007] According to an embodiment of the present invention, a first current flows through the first capacitor, and a second current flows through the second capacitor. A first ratio of the first current and the second current is equal to a second ratio of the capacitance value of the first capacitor and the capacitance value of the second capacitor. The first current is greater than the second current, and the capacitance value of the first capacitor is greater than the capacitance value of the second capacitor.

[0008] According to an embodiment of the present invention, the transformer includes a first secondary coil.

[0009] According to an embodiment of the present invention, the power conversion circuit further includes an output circuit. The output circuit is coupled to the first secondary coil for converting the energy stored in the first secondary coil into an output voltage.

[0010] According to an embodiment of the present invention, the output circuit includes a third capacitor and a first rectifying unit. The third capacitor includes a first end and a second end for generating an output voltage, wherein the first end is coupled to the first secondary coil. The first rectifying unit is coupled between the first secondary coil and the second end for rectifying the half-wave rectified energy of the first secondary coil into a third current. The third current charges the third capacitor to generate the output voltage.

[0011] According to an embodiment of the present invention, when the upper bridge transistor is turned on, the lower bridge transistor is turned off, and the first rectifying unit is turned off, the input voltage stores energy in the transformer and the first capacitor. When the upper bridge transistor is turned off, the lower bridge transistor is turned on, and the first rectifying unit is turned on, the energy of the transformer and the first capacitor is transferred to the secondary coil through the primary coil, and the third capacitor is charged to generate the output voltage.

[0012] According to another embodiment of the present invention, the transformer further includes a second secondary coil. The first secondary coil and the second secondary coil are connected in series to a second node.

[0013] According to another embodiment of the present invention, the output circuit further includes a second rectifying unit and an inductor. The second rectifying unit is coupled between the second secondary coil and the second end for rectifying the full-wave rectified energy of the first secondary coil into a fourth current. The inductor is coupled between the second node and the first end. The fourth current charges the third capacitor to generate the output voltage.

[0014] According to another embodiment of the present invention, when the above upper bridge transistor is turned on, the above lower bridge transistor is turned off, and the above second rectifying unit is turned on, the above input voltage stores energy in the above transformer and the above first capacitor. The energy stored in the above transformer is transferred to the above second secondary coil through the above primary coil, and the above third capacitor is charged to generate the above output voltage. When the above upper bridge transistor is turned off, the above lower bridge transistor is turned on, and the above first rectifying unit is turned on, the energy of the above transformer and the above first capacitor is transferred to the above first secondary coil through the above primary coil, and the above third capacitor is charged to generate the above output voltage.

[0015] The present invention further provides a current detection circuit applicable to a power conversion circuit. The above power conversion circuit includes an upper bridge switch coupled between an input voltage and a switching node, a lower bridge transistor coupled between the above switching node and a ground terminal, a transformer including a primary coil, and a first capacitor coupled to the above ground terminal. The above primary coil is coupled between the above switching node and the above first capacitor. The above current detection circuit includes a second capacitor and a current detection resistor. The above second capacitor is coupled to the above first node. The above current detection resistor is coupled between the above second capacitor and the above ground terminal.

[0016] According to an embodiment of the present invention, the above power conversion circuit is an asynchronous half-bridge flyback converter. The above power conversion circuit obtains the current flowing through the above transformer and the above first capacitor according to the voltage across the above current detection resistor.

[0017] According to an embodiment of the present invention, a first current flows through the above first capacitor, and a second current flows through the above second capacitor. A first ratio of the above first current and the above second current is equal to a second ratio of the capacitance value of the above first capacitor and the capacitance value of the above second capacitor. The above first current is greater than the above second current, and the capacitance value of the above first capacitor is greater than the capacitance value of the above second capacitor.

[0018] According to an embodiment of the present invention, the above transformer includes a first secondary coil.

[0019] According to an embodiment of the present invention, the above power conversion circuit further includes an output circuit. The above output circuit is coupled to the above first secondary coil and is used to convert the energy stored in the above first secondary coil into an output voltage.

[0020] According to an embodiment of the present invention, the output circuit includes a third capacitor and a first rectifying unit. The third capacitor includes a first end and a second end for generating an output voltage. The first end is coupled to the first secondary coil. The first rectifying unit is coupled between the first secondary coil and the second end for rectifying the half-wave rectified energy of the first secondary coil into a third current. The third current charges the third capacitor to generate the output voltage.

[0021] According to an embodiment of the present invention, when the upper bridge transistor is turned on, the lower bridge transistor is turned off, and the first rectifying unit is not turned on, the input voltage stores energy in the transformer and the first capacitor. When the upper bridge transistor is turned off, the lower bridge transistor is turned on, and the first rectifying unit is turned on, the energy of the transformer and the first capacitor is transferred to the secondary coil through the primary coil and charges the third capacitor to generate the output voltage.

[0022] According to another embodiment of the present invention, the transformer further includes a second secondary coil. The first secondary coil and the second secondary coil are connected in series to a second node.

[0023] According to another embodiment of the present invention, the output circuit further includes a second rectifying unit and an inductor. The second rectifying unit is coupled between the second secondary coil and the second end for rectifying the full-wave rectified energy of the first secondary coil into a fourth current. The inductor is coupled between the second node and the first end. The fourth current charges the third capacitor to generate the output voltage.

[0024] According to another embodiment of the present invention, when the upper bridge transistor is turned on, the lower bridge transistor is turned off, and the second rectifying unit is turned on, the input voltage stores energy in the transformer and the first capacitor. The energy stored in the transformer is transferred to the second secondary coil through the primary coil and charges the third capacitor to generate the output voltage. When the upper bridge transistor is turned off, the lower bridge transistor is turned on, and the first rectifying unit is turned on, the energy of the transformer and the first capacitor is transferred to the first secondary coil through the primary coil and charges the third capacitor to generate the output voltage. Description of the Drawings

[0025] Figure 1 A circuit diagram showing a power conversion circuit according to an embodiment of the present invention;

[0026] Figure 2 A circuit diagram showing a power conversion circuit according to another embodiment of the present invention;

[0027] Figure 3 Show the circuit diagram of the power conversion circuit according to another embodiment of the present invention; and

[0028] Figure 4 Show the circuit diagram of the power conversion circuit according to another embodiment of the present invention.

[0029] Reference numerals:

[0030] 100, 200, 300, 400: Power conversion circuit

[0031] 110, 410: Output circuit

[0032] 320: Current detection circuit

[0033] Q1: Upper bridge transistor

[0034] Q2: Lower bridge transistor

[0035] TM: Transformer

[0036] VIN: Input voltage

[0037] SW: Switching node

[0038] N1: First node

[0039] N2: Second node

[0040] N3: Third node

[0041] PC: Primary coil

[0042] SC1: First secondary coil

[0043] SC2: Second secondary coil

[0044] Lr: Leakage inductance

[0045] Lm: Magnetizing inductance

[0046] C1: First capacitor

[0047] C2: Second capacitor

[0048] C3: Third capacitor

[0049] UR1: First rectifying element

[0050] UR2: Second rectifying element

[0051] CK: Choke

[0052] TE1: First end

[0053] TE2: Second end

[0054] VO: Output voltage

[0055] ICHR: Charging current

[0056] IDIS: Discharging current

[0057] IO1: First output current

[0058] IO2: Second output current

[0059] VCS1: First current detection voltage

[0060] VCS2: Second current detection voltage

[0061] VCS3: Third current detection voltage

[0062] RCS1: First current detection resistor

[0063] RCS2: Second current detection circuit

[0064] RCS3: Third current detection resistor

[0065] IC1: First capacitor current

[0066] IC2: Second capacitor current Detailed implementation manners

[0067] The following description is of the embodiments of the present invention. Its purpose is to illustrate the general principles of the present invention by way of examples and should not be regarded as a limitation of the present invention. The scope of the present invention shall be defined by the scope defined in the claims.

[0068] It should be noted that the content disclosed below can provide multiple embodiments or examples for practicing different features of the present invention. The specific element examples and arrangements described below are only used to briefly elaborate the spirit of the present invention and are not used to limit the scope of the present invention. In addition, the following specification may reuse the same element symbols or words in multiple examples. However, the purpose of the reuse is only to provide a simplified and clear description and is not used to limit the relationship between the multiple embodiments and / or configurations discussed below.

[0069] In addition, the descriptions such as one feature being connected to, coupled to, and / or formed on another feature in the following specification may actually include multiple different embodiments, including the direct contact of these features, or the inclusion of other additional features formed between these features, etc., such that these features are not in direct contact.

[0070] In addition, relative terms may be used in the embodiments, such as "lower" or "bottom" and "higher" or "top", to describe the relative relationship of one element of the drawing to another element. It can be understood that if the device in the drawing is flipped upside down, the element described on the "lower" side will become the element on the "higher" side.

[0071] It can be understood that although terms such as "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms, and these terms are only used to distinguish different elements, components, regions, layers, and / or parts. Therefore, a first element, component, region, layer, and / or part discussed below may be referred to as a second element, component, region, layer, and / or part without departing from the teachings of some embodiments of the present invention.

[0072] Some embodiments of the present invention can be understood in conjunction with the drawings, and the drawings of the embodiments of the present invention are also regarded as a part of the description of the embodiments of the present invention. It should be understood that the drawings of the embodiments of the present invention are not drawn to the scale of actual devices and elements. In the drawings, the shapes and thicknesses of the embodiments may be exaggerated to clearly show the features of the embodiments of the present invention. In addition, the structures and devices in the drawings are shown in a schematic manner to clearly show the features of the embodiments of the present invention.

[0073] Herein, the terms "about", "approximately", "substantially" generally mean within 20% of a given value or range, preferably within 10%, more preferably within 5%, or 3%, or 2%, or 1%, or 0.5%. The given quantity is an approximate quantity, that is, the meaning of "about", "approximately", "substantially" may still be implied even without specifically stating "about", "approximately", "substantially".

[0074] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. It can be understood that these terms, such as those defined in a commonly used dictionary, should be interpreted to have a meaning consistent with the relevant technology and the background or context of the present invention, and should not be interpreted in an idealized or overly formal manner, unless specifically defined in the embodiments of the present invention.

[0075] In some embodiments of the present invention, terms regarding joining and connection, such as "connect" and "interconnect", unless specifically defined, may mean that two structures are in direct contact, or may also mean that two structures are not in direct contact, and other structures are provided between these two structures. And these terms regarding joining and connection may also include the cases where both structures can move, or both structures are fixed.

[0076] In the drawings, like elements and / or features may have the same element symbols. Various elements of the same type may be distinguished by adding a letter or number after the element symbol for distinguishing like elements and / or like features.

[0077] Figure 1 A circuit diagram showing a power conversion circuit according to an embodiment of the present invention is shown. As Figure 1 shown, the power conversion circuit 100 includes an upper bridge transistor Q1, a lower bridge transistor Q2, a transformer TM, a first capacitor C1, a first current detection resistor RCS1, and an output circuit 110. According to an embodiment of the present invention, the power conversion circuit 100 may be an asymmetrical half-bridge flyback power converter.

[0078] The upper bridge switch Q1 is coupled between the input voltage VIN and the switching node SW, and the lower bridge switch Q2 is coupled between the switching node SW and the second node N2. The transformer TM includes a primary coil PC and a first secondary coil SC1, wherein the primary coil PC is equivalent to a leakage inductance Lr and a magnetizing inductance Lm, and the leakage inductance Lr and the magnetizing inductance Lm are connected in series between the switching node SW and the first node N1. According to some embodiments of the present invention, the transformer TM provides the energy stored in the primary coil PC to the first secondary coil SC1. The first capacitor C1 is coupled between the first node N1 and the second node N2, and the first current detection resistor RCS1 is coupled between the second node N2 and the ground terminal.

[0079] As Figure 1 shown, the output circuit 110 is connected across both ends of the secondary coil SC for converting the energy stored in the transformer TM into an output voltage VO. The output circuit 110 includes a third capacitor C3 and a first rectifying element UR1. The third capacitor C3 includes a first terminal TE1 and a second terminal TE2 for generating the output voltage VO, wherein the first terminal TE1 is directly coupled to the first secondary coil SC1. The first rectifying unit UR1 is coupled between the first secondary coil SC1 and the second terminal TE2 for providing the first output current IO1 output from the first secondary coil SC1 to the third capacitor C3 to generate the output voltage VO.

[0080] According to an embodiment of the present invention, the first rectifying unit UR1 may be a rectifying diode. According to another embodiment of the present invention, the first rectifying unit UR1 may be a transistor that is controlled to conduct and not conduct through a gate voltage. According to other embodiments of the present invention, the first rectifying unit UR1 may be any known or unknown rectifying element. In the following embodiments, the first rectifying unit UR1 is described by taking a transistor that is controlled to conduct and not conduct through a gate voltage as an example, and is not limited thereto in any form.

[0081] According to an embodiment of the present invention, when the transformer TM is completely demagnetized, the upper bridge transistor Q1 conducts, the lower bridge transistor Q2 does not conduct, and the first rectifying unit UR1 does not conduct, so that the input voltage VIN charges the transformer TM and the first capacitor C1 through the upper bridge transistor Q1. According to an embodiment of the present invention, when the upper bridge transistor Q1 conducts, the charging current ICHR generated by the input voltage VIN flows through the leakage inductance Lr, the magnetizing inductance Lm, the first capacitor C1, and the first current detection resistor RCS1 to the ground terminal, thereby storing energy in the magnetizing inductance Lm and the first capacitor C1.

[0082] According to another embodiment of the present invention, when the upper bridge transistor Q1 does not conduct, the lower bridge transistor Q2 conducts, and the first rectifying unit UR1 conducts, the energy stored in the magnetizing inductance Lm is transferred to the first secondary coil SC1 through the turns ratio of the transformer TM, thereby generating a first output current IO1. In addition, the energy stored in the first capacitor C1 generates a discharge current IDIS, which is also transferred to the first secondary coil SC1 through the turns ratio of the transformer TM, thereby generating a first output current IO1. At the same time, the conducting first rectifying unit UR1 enables the first output current IO1 generated by the first secondary coil SC1 to charge the third capacitor C3, thereby generating an output voltage VO.

[0083] As Figure 1 shown, since the charging current ICHR generated by the input voltage VIN passes through the first current detection resistor RCS1 to generate a first current detection voltage VCS1, the magnitude of the charging current ICHR can be known by measuring the first current detection voltage VCS1 across the two ends of the first current detection resistor RCS1. However, since the discharge current IDIS does not flow through the first current detection resistor RCS1, the magnitude of the discharge current IDIS cannot be known through the first current detection voltage VCS1.

[0084] Figure 2 Shows a circuit diagram of a power conversion circuit according to another embodiment of the present invention. Comparing the Figure 2 power conversion circuit 200 with the Figure 1 power conversion circuit 100, Figure 1The first current detection circuit RCS1 is replaced by a second current detection circuit RCS2, and the lower bridge transistor Q2 is modified to be coupled between the switching node SW and the ground terminal. According to an embodiment of the present invention, the power conversion circuit 200 can be an asynchronous half-bridge flyback converter.

[0085] As Figure 2 shown, since both the charging current ICHR and the discharging current IDIS flow through the second current detection resistor RCS2, the magnitudes of the charging current ICHR and the discharging current IDIS can be obtained by measuring the second current detection voltage VCS2 across the second current detection resistor RCS2. However, since both the charging current ICHR and the discharging current IDIS are large currents, the power loss caused by the second current detection resistor RCS2 is very large, thereby significantly reducing the overall conversion efficiency of the power conversion circuit 200. In addition, due to the significant power loss generated by the second current detection resistor RCS2, the second current detection resistor RCS2 must consider the heat dissipation problem, which causes trouble in component design and increases the cost required for the components. Therefore, there is a need for a more efficient current detection method to improve the conversion efficiency of the power conversion circuit.

[0086] Figure 3 Displays a circuit diagram of a power conversion circuit according to another embodiment of the present invention. Comparing the Figure 3 power conversion circuit 300 with the Figure 2 power conversion circuit 200, Figure 2 the second current detection resistor RCS2 is replaced by a current detection circuit 320, where the current detection circuit 320 is connected in parallel with the first capacitor C1 and is coupled between the first node N1 and the ground terminal.

[0087] As Figure 3 shown, the current detection circuit 320 includes a second capacitor C2 and a third current detection resistor RCS3. The second capacitor C2 is coupled to the first node N1, and the third current detection resistor RCS3 is coupled between the second capacitor C2 and the ground terminal. In other words, the second capacitor C2 and the third current detection resistor RCS3 are connected in series between the first node N1 and the ground terminal, and the second capacitor C2 and the third current detection resistor RCS3 are connected in parallel with the first capacitor C1 after being connected in series.

[0088] According to an embodiment of the present invention, the capacitance value of the first capacitor C1 is N times that of the second capacitor C2, where N is any positive number. When N is very large, the current IC2 of the second capacitor is much smaller than the current IC1 of the first capacitor, such that the third current detection voltage VCS3 generated by the third current detection resistor RCS3 is much smaller than the voltage across the second capacitor C2. When N is large enough such that the third current detection voltage VCS3 can be neglected, the current IC1 of the first capacitor is approximately N times that of the second capacitor current IC2. In other words, by selecting the ratio of the capacitance value of the first capacitor C1 to that of the second capacitor C2, the current IC2 of the second capacitor flowing through the third current detection resistor RCS3 can be reduced, thereby reducing the power loss caused by the third current detection resistor RCS3.

[0089] For example, assume that the first capacitor current IC1 of the first capacitor C1 flowing through Figure 2 and Figure 3 is I for both, and when the second current detection resistor RCS2 is R, Figure 2 the second current detection voltage VCS2 is equal to I×R. As Figure 3 shown, since the second capacitor current IC2 is approximately of the first capacitor current IC1, and in order to keep the third current detection voltage VCS3 equal to the second current detection voltage VCS2, therefore Figure 3 the third current detection resistor RCS3 should be N times that of the second current detection resistor RCS2, that is, the resistance value of the third current detection resistor RCS3 is N·R. The power consumed by the third current detection resistor RCS3 is as shown in Equation 1:

[0090]

[0091]

[0092] The power consumed by the second current detection resistor RCS2 is as shown in Equation 2:

[0093] IC2 2 ×RC2 = I 2 R (Equation 2)

[0094] Comparing Equation 1 with Equation 2, the power consumed by the third current detection resistor RCS3 is of the power consumed by the second current detection resistor RCS2. When N is very large, the power consumed by the third current detection resistor RCS3 can be significantly reduced, thereby significantly improving the conversion efficiency of the power conversion circuit 300.

[0095] In addition, due to the maximum power consumption limitations of the second current sensing resistor RCS2 and the third current sensing resistor RCS3, multiple second current sensing resistors RCS2 often need to be connected in parallel to share the power consumption and avoid the phenomenon of thermal runaway, which increases the component cost.

[0096] For example, assume that the maximum power consumption of a resistor component is 0.25W, and assume that the power consumption generated by the second current sensing resistor RCS2 is 0.5W. To operate the resistor within a safe range, five resistors with a maximum power consumption of 0.25W are selected and connected in parallel to form the second current sensing resistor RCS2.

[0097] In other words, five resistors with a maximum power consumption of 0.25W are used to share the 0.5W power consumption to avoid thermal runaway of the resistor component. Assume N is 50, which represents that the power consumption generated by the third current sensing resistor RCS3 is only 0.01W. In this case, only one resistor component with a maximum power consumption of 0.25W is required.

[0098] Furthermore, Figure 3 the power conversion circuit 300 of Figure 2 further includes a second capacitor C2 compared to the power conversion circuit 200 of Figure 3 Therefore, the power conversion circuit 300 of Figure 2 requires an additional capacitor component to meet the requirement of the second capacitor C2. Assume that the areas and component costs required for the resistor and the capacitor are the same.

[0099] In comparison, Figure 3 the power conversion circuit 300 of Figure 2 saves the circuit area and component cost of three resistors compared to the power conversion circuit 200 of Figure 3 In other words, the power conversion circuit 300 of Figure 2 not only significantly reduces power loss and improves the overall conversion efficiency compared to the power conversion circuit 200 of

[0100] Figure 4 shows the circuit diagram of the power conversion circuit according to another embodiment of the present invention. Comparing the power conversion circuit 400 of Figure 4 with the power conversion circuit 300 of Figure 3 the power conversion circuit 400 further includes a second secondary coil SC2 and an output circuit 410, where the output circuit 410 compared to Figure 3The output circuit 110 further includes a second rectifying element UR2 and a choke CK.

[0101] As Figure 4 shown, the first secondary coil SC1 and the second secondary coil SC2 are connected in series to the third node N3, and the second rectifying element UR2 is coupled between the second secondary coil SC2 and the second terminal TE2. The choke CK is coupled between the third node N3 and the first terminal TE1 to reduce the influence of high-frequency noise.

[0102] According to an embodiment of the present invention, the second rectifying unit UR2 may be a rectifying diode. According to another embodiment of the present invention, the second rectifying unit UR2 may be a transistor that is controlled to conduct and not conduct through a gate voltage. According to other embodiments of the present invention, the second rectifying unit UR2 may be any known or unknown rectifying element. In Figure 4 the embodiment, the second rectifying unit UR2 is described by taking a transistor that is controlled to conduct and not conduct through a gate voltage as an example, and is not limited thereto in any form.

[0103] According to an embodiment of the present invention, when the upper bridge transistor Q1 conducts, the lower bridge transistor Q2 does not conduct, and the second rectifying element UR2 conducts, the input voltage VIN stores energy in the transformer TM and the first capacitor C1, and the energy stored in the transformer TM and the first capacitor C1 is transferred to the second secondary coil SC2 through the transformer TM, so that the second secondary coil SC2 generates a second output current IO2 and charges the third capacitor C3 to generate an output voltage VO.

[0104] According to another embodiment of the present invention, when the upper bridge transistor Q1 does not conduct, the lower bridge transistor Q2 conducts, and the first rectifying element UR1 conducts, the energy stored in the transformer TM and the first capacitor C1 is transferred to the first secondary coil SC1 through the transformer TM, so that the first secondary coil SC1 generates a first output current IO1 and charges the third capacitor C3 to generate an output voltage VO.

[0105] In other words, the current detection circuit 320 of the power conversion circuit 400 reduces the power loss generated by the third current detection resistor RCS3 by selecting the ratio of the first capacitor C1 and the second capacitor C2, thereby improving the overall conversion efficiency, reducing the component cost, and reducing the circuit area. In addition, the first secondary coil SC1 outputs the energy of the half-wave rectification stored in the transformer TM as the first output current IO1 to charge the third capacitor C3, and the second secondary coil SC2 then outputs the energy of the full-wave rectification stored in the transformer TM as the second output current IO2 to charge the third capacitor C3, thereby improving the conversion efficiency of the power conversion circuit 400. Furthermore, the power conversion circuit 400 further includes a second secondary coil SC2 and a second rectifying element UR2 for generating an additional second output current IO2 to further improve the conversion efficiency.

[0106] The present invention provides a power conversion circuit and its current detection circuit. By mapping a small current of a path beside a path with a large current, it not only helps to significantly reduce the power loss caused by the current detection resistor, but also can reduce the component cost and the circuit area, and the accuracy of the circuit detection can also be maintained.

[0107] Although the embodiments of the present invention and their advantages have been disclosed as above, it should be understood that any person skilled in the art can make changes, substitutions, and modifications without departing from the spirit and scope of the present invention. In addition, the protection scope of the present invention is not limited to the processes, machines, manufactures, compositions of matter, devices, methods, and steps in the specific embodiments described in the specification. Any person skilled in the art can understand the processes, machines, manufactures, compositions of matter, devices, methods, and steps developed currently or in the future from the disclosure content of some embodiments of the present invention. As long as they can implement substantially the same functions or obtain substantially the same results in the embodiments described herein, they can be used according to some embodiments of the present invention. Therefore, the protection scope of the present invention includes the above-mentioned processes, machines, manufactures, compositions of matter, devices, methods, and steps. In addition, each claim constitutes an individual embodiment, and the protection scope of the present invention also includes the combination of each claim and embodiment.

Claims

1. A power conversion circuit, characterized in that: include: An upper bridge switch coupled between an input voltage and a switching node; A lower bridge switch coupled between the switching node and a ground terminal; A transformer, comprising a primary coil, wherein the primary coil is coupled between the switching node and a first node; A first capacitor coupled between the first node and the ground terminal; as well as A current detection circuit, connected in parallel with the first capacitor, comprising: a second capacitor coupled to the first node; as well as A current detection resistor is coupled between the second capacitor and the ground terminal.

2. The power conversion circuit according to claim 1, characterized in that: The power conversion circuit is a non-synchronous half-bridge flyback converter; The power conversion circuit obtains the current flowing through the transformer and the first capacitor according to the voltage across the current detection resistor.

3. The power conversion circuit according to claim 1, characterized in that: A first current flows through the first capacitor, and a second current flows through the second capacitor; wherein a first ratio of the first current to the second current is equal to a second ratio of the capacitance value of the first capacitor to the capacitance value of the second capacitor; The first current is greater than the second current, and the capacitance value of the first capacitor is greater than the capacitance value of the second capacitor.

4. The power conversion circuit according to claim 1, characterized in that: The transformer comprises a first secondary coil.

5. The power conversion circuit according to claim 4, characterized in that: Also includes: An output circuit is coupled to the first secondary coil and is used for converting the energy stored in the first secondary coil into an output voltage.

6. The power conversion circuit according to claim 5, characterized in that: The above output circuit comprises: a third capacitor, comprising a first terminal and a second terminal, for generating an output voltage, wherein the first terminal is coupled to the first secondary coil; and a first rectifying unit, coupled between the first secondary coil and the second end, for rectifying the half-wave rectified energy of the first secondary coil into a third current; The third current charges the third capacitor to generate the output voltage.

7. The power conversion circuit according to claim 6, characterized in that: When the upper bridge transistor is turned on, the lower bridge transistor is turned off, and the first rectifying unit is turned off, the input voltage stores energy in the transformer and the first capacitor; When the upper bridge transistor is not conducting, the lower bridge transistor is conducting and the first rectifying unit is conducting, the energy of the transformer and the first capacitor is transferred to the secondary coil via the primary coil, and the third capacitor is charged to generate the output voltage.

8. The power conversion circuit according to claim 6, characterized in that: The transformer further comprises a second secondary coil; The first secondary coil and the second secondary coil are connected in series at a second node.

9. The power conversion circuit according to claim 8, characterized in that: The output circuit further comprises: a second rectifying unit, coupled between the second secondary coil and the second end, for rectifying the full-wave rectified energy of the first secondary coil into a fourth current; and a choke coil coupled between the second node and the first end; The fourth current charges the third capacitor to generate the output voltage.

10. The power conversion circuit according to claim 9, characterized in that: When the upper bridge transistor is turned on, the lower bridge transistor is not turned on, and the second rectifying unit is turned on, the input voltage stores energy in the transformer and the first capacitor, and the energy stored in the transformer is transferred to the second secondary coil via the primary coil, and the third capacitor is charged to generate the output voltage; When the upper bridge transistor is not conducting, the lower bridge transistor is conducting and the first rectifying unit is conducting, the energy of the transformer and the first capacitor is transferred to the first secondary coil via the primary coil, and the third capacitor is charged to generate the output voltage.

11. A current detection circuit, characterized in that: The invention is applicable to a power conversion circuit, wherein the power conversion circuit comprises an upper bridge switch coupled between an input voltage and a switching node, a lower bridge transistor coupled between the switching node and a ground terminal, a transformer comprising a primary coil and a first capacitor coupled to the ground terminal, wherein the primary coil is coupled between the switching node and the first capacitor, wherein the current detection circuit comprises: a second capacitor coupled to a first node; and A current detection resistor is coupled between the second capacitor and the ground terminal.

12. The current detection circuit according to claim 11, characterized in that: The power conversion circuit is a non-synchronous half-bridge flyback converter; The power conversion circuit obtains the current flowing through the transformer and the first capacitor according to the voltage across the current detection resistor.

13. The current detection circuit according to claim 11, characterized in that: A first current flows through the first capacitor, and a second current flows through the second capacitor; wherein a first ratio of the first current to the second current is equal to a second ratio of the capacitance value of the first capacitor to the capacitance value of the second capacitor; The first current is greater than the second current, and the capacitance value of the first capacitor is greater than the capacitance value of the second capacitor.

14. The current detection circuit according to claim 11, characterized in that: The transformer comprises a first secondary coil.

15. The current detection circuit according to claim 14, characterized in that: The power conversion circuit further includes an output circuit; The output circuit is coupled to the first secondary coil and is used for converting the energy stored in the first secondary coil into an output voltage.

16. The current detection circuit according to claim 15, characterized in that: The output circuit comprises a third capacitor and a first rectifying unit; The third capacitor comprises a first terminal and a second terminal, and is used to generate an output voltage; wherein the first end is coupled to the first secondary coil; The first rectifying unit is coupled between the first secondary coil and the second end, and is used to rectify the half-wave rectified energy of the first secondary coil into a third current; The third current charges the third capacitor to generate the output voltage.

17. The current detection circuit according to claim 16, characterized in that: When the upper bridge transistor is turned on, the lower bridge transistor is turned off, and the first rectifying unit is turned off, the input voltage stores energy in the transformer and the first capacitor; When the upper bridge transistor is not conducting, the lower bridge transistor is conducting and the first rectifying unit is conducting, the energy of the transformer and the first capacitor is transferred to the secondary coil via the primary coil, and the third capacitor is charged to generate the output voltage.

18. The current detection circuit according to claim 16, characterized in that: The transformer further comprises a second secondary coil; The first secondary coil and the second secondary coil are connected in series at a second node.

19. The current detection circuit according to claim 18, characterized in that: The output circuit further includes a second rectifying unit and a choke coil; The second rectifying unit is coupled between the second secondary coil and the second end, and is used to rectify the full-wave rectified energy of the first secondary coil into a fourth current; wherein the choke is coupled between the second node and the first end; The fourth current charges the third capacitor to generate the output voltage.

20. The current detection circuit according to claim 19, characterized in that: When the upper bridge transistor is turned on, the lower bridge transistor is not turned on, and the second rectifying unit is turned on, the input voltage stores energy in the transformer and the first capacitor, and the energy stored in the transformer is transferred to the second secondary coil via the primary coil, and the third capacitor is charged to generate the output voltage; When the upper bridge transistor is not conducting, the lower bridge transistor is conducting and the first rectifying unit is conducting, the energy of the transformer and the first capacitor is transferred to the first secondary coil via the primary coil, and the third capacitor is charged to generate the output voltage.

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