Synchronous rectification device for power converter

Abstract

The invention provides a synchronous rectification device for a power converter. The power converter at least comprises a secondary side circuit and a transformer. The synchronous rectification device comprises a synchronous rectification circuit and a controller. The synchronous rectification circuit comprises a synchronous rectification switch and a current receiving circuit. The synchronous rectification switch is coupled between the secondary side circuit and the secondary side winding of the transformer. The current receiving circuit provides a current signal according to a current flowing through the synchronous rectification switch. The controller controls the synchronous rectification switch according to the current signal. Under the condition that the synchronous rectification switch is turned off, when the current signal shows that the current value of the current is larger than the preset value, the controller turns on the synchronous rectification switch.

Description

Technical Field

[0001] The invention relates to an electronic device, and in particular to a synchronous rectification device for a power converter. Background Art

[0002] Generally speaking, a power converter can use a synchronous rectification switch to perform synchronous rectification operation to reduce energy loss in power conversion. The synchronous rectification switch must operate based on a control signal. Therefore, how to provide a correct control signal to accurately perform the synchronous rectification operation of the power converter is one of the research focuses of those skilled in the art. Summary of the invention

[0003] The invention provides a synchronous rectification device for a power converter, which can accurately perform the synchronous rectification operation of the power converter.

[0004] The synchronous rectification device of the present invention is used for a power converter. The power converter includes at least a secondary side circuit and a transformer. The synchronous rectification device includes a synchronous rectification circuit and a controller. The synchronous rectification circuit includes a synchronous rectification switch and a current receiving circuit. The synchronous rectification switch is coupled between the secondary side circuit and the secondary side winding of the transformer. The current receiving circuit receives the current flowing through the synchronous rectification switch and provides a current signal based on the current. The controller is coupled to the current receiving circuit and the control end of the synchronous rectification switch. The controller controls the synchronous rectification switch based on the current signal. When the synchronous rectification switch is disconnected, when the current signal indicates that the current is greater than a predetermined value, the controller turns on the synchronous rectification switch.

[0005] Based on the above, the current receiving circuit provides a current signal according to the current flowing through the synchronous rectification switch. The controller controls the synchronous rectification switch according to the current signal. When the synchronous rectification switch is disconnected, when the current signal indicates that the current is greater than a predetermined value, the controller turns on the synchronous rectification switch. In this way, the synchronous rectification device can accurately perform the synchronous rectification operation of the power converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic diagram of a power converter according to a first embodiment of the present invention;

[0007] Figure 2 is a schematic diagram of a power converter according to a second embodiment of the present invention;

[0008] Figure 3 is a schematic diagram of a power converter according to a third embodiment of the present invention.

[0009] Description of Reference Numerals

[0010] 10, 20, 30: Power converter

[0011] 11: Primary circuit

[0012] 12: Transformer

[0013] 13: Secondary circuit

[0014] 100, 200, 300: Synchronous rectifier

[0015] 110: Synchronous Rectification Circuit

[0016] 111: Synchronous rectification switch

[0017] 112: Current receiving circuit

[0018] 120, 220, 320: Controller

[0019] 221, 321: Logic control circuit

[0020] 222, 322: Voltage judgment circuit

[0021] 323: Sensing Circuit

[0022] C0: Output capacitor

[0023] FF:Flip-flop

[0024] ID: Current

[0025] ND: Connecting Node

[0026] Q: Output of the flip-flop

[0027] R: reset terminal of the flip-flop

[0028] S: Setting terminal of the flip-flop

[0029] SC: Control signal

[0030] SCR: Current signal

[0031] SD: judgment signal

[0032] SS: Sensing signal

[0033] TD: Determined value

[0034] VD: Detection voltage

[0035] VTH: Voltage threshold DETAILED DESCRIPTION

[0036] Some embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The component symbols cited in the following description will be regarded as the same or similar components when the same component symbols appear in different drawings. These embodiments are only part of the present invention and do not disclose all possible implementation methods of the present invention. More specifically, these embodiments are only examples in the patent claims of the present invention.

[0037] Please refer to Figure 1 , Figure 1 is a schematic diagram of a power converter according to a first embodiment of the present invention. In this embodiment, the power converter 10 includes a primary side circuit 11, a transformer 12, a secondary side circuit 13 and a synchronous rectification device 100. Taking this embodiment as an example, the primary side winding of the transformer 12 is coupled to the primary side circuit 11. The secondary side winding of the transformer 12 is coupled to the secondary side circuit 13. The secondary side circuit 13 includes an output capacitor C0. Taking this embodiment as an example, the first end of the output capacitor C0 is coupled to the first end of the secondary side winding of the transformer 12. The second end of the output capacitor C0 is coupled to the ground end of the secondary side circuit 13.

[0038] In this embodiment, the synchronous rectification device 100 is used for the synchronous rectification operation of the power converter 10. The synchronous rectification device 100 includes a synchronous rectification circuit 110 and a controller 120. The synchronous rectification circuit 110 includes a synchronous rectification switch 111 and a current receiving circuit 112. The synchronous rectification switch 111 is coupled between the secondary side circuit 13 and the secondary side winding of the transformer 12. Taking this embodiment as an example, the first end of the synchronous rectification switch 111 is coupled to the secondary side winding at the connection node ND. The second end of the synchronous rectification switch 111 is coupled to the second end of the output capacitor C0. The control end of the synchronous rectification switch 111 is coupled to the controller 120.

[0039] In this embodiment, the current receiving circuit 112 receives the current ID flowing through the synchronous rectification switch 111, and provides a current signal SCR according to the current ID. In one embodiment, the current receiving circuit 112 can receive the current ID flowing through the diode component of the synchronous rectification switch 111. In one embodiment, the current receiving circuit 112 can sense the current ID flowing through the first end of the synchronous rectification switch 111. The current signal SCR can be information corresponding to the current ID, such as the current value of the current ID.

[0040] In the present embodiment, the controller 120 is coupled to the current receiving circuit 112 and the control end of the synchronous rectification switch 111. The controller 120 receives the current signal SCR and analyzes the current signal SCR. The controller 120 controls the synchronous rectification switch 111 according to the current signal SCR. When the synchronous rectification switch 111 is turned off, when the current signal SCR indicates that the current value of the current ID is greater than the predetermined value TD, the controller 120 turns on the synchronous rectification switch 111. In the present embodiment, the controller 120 uses the control signal SC to turn on the synchronous rectification switch 111.

[0041] On the other hand, when the synchronous rectification switch 111 is turned off, when the current signal SCR indicates that the current value of the current ID is less than or equal to the predetermined value TD, the controller 120 continues to turn off the synchronous rectification switch 111 .

[0042] It is worth mentioning that the current receiving circuit 112 provides the current signal SCR according to the current ID flowing through the synchronous rectification switch 111. When the synchronous rectification switch 111 is turned off, when the current signal SCR indicates that the current value of the current ID is greater than the predetermined value TD, the controller 120 turns on the synchronous rectification switch 111. In this way, the synchronous rectification device 100 can accurately perform the synchronous rectification operation of the power converter 100 according to the current ID flowing through the synchronous rectification switch 111.

[0043] For example, when the synchronous rectification switch 111 is turned off, the current ID flows through the diode component of the synchronous rectification switch 111. When the current value of the current ID is less than or equal to the predetermined value TD, this indicates that the current ID is a resonant current. Therefore, the controller 120 continues to turn off the synchronous rectification switch 111. When the current value of the current ID is greater than the predetermined value TD, this indicates that the current ID is an output current, not a resonant current. Therefore, the controller 120 turns on the synchronous rectification switch 111.

[0044] In this embodiment, the controller 120 may receive the detection voltage VD at the connection node ND and determine the voltage value of the detection voltage VD. When the voltage value of the detection voltage VD changes more than the slew rate threshold, the controller 120 turns on the synchronous rectification switch 111. When the voltage value of the detection voltage VD changes less than the slew rate threshold, the detection voltage VD may be a resonant voltage. Therefore, the controller 120 continues to turn off the synchronous rectification switch 111.

[0045] In addition, when the voltage value of the detection voltage VD is lower than the predetermined voltage value, the controller 120 turns on the synchronous rectification switch 111. When the voltage value of the detection voltage VD is higher than or equal to the predetermined voltage value, the controller 120 turns off the synchronous rectification switch 111.

[0046] Based on the above, the controller 120 may use the detection voltage VD as an auxiliary basis for controlling the synchronous rectification switch 111. However, the present invention is not limited thereto, and in some embodiments, the controller 120 may not receive the detection voltage VD.

[0047] In this embodiment, the synchronous rectification switch 111 and the current receiving circuit 112 are fabricated in a single semiconductor die. In other words, the synchronous rectification circuit 110 is fabricated in a single semiconductor die. The controller 120 and the semiconductor die are packaged in the same circuit package. Therefore, the synchronous rectification device 100 can be assembled into the power converter 10.

[0048] Please refer to Figure 2 , Figure 2 2 is a schematic diagram of a power converter according to a second embodiment of the present invention. In this embodiment, the power converter 20 includes a primary side circuit 11, a transformer 12, a secondary side circuit 13 and a synchronous rectification device 200. The synchronous rectification device 200 includes a synchronous rectification circuit 110 and a controller 220. The coupling relationship between the primary side circuit 11, the transformer 12, the secondary side circuit 13 and the synchronous rectification circuit 110 and the implementation method of the synchronous rectification circuit 110 have been described in detail. Figure 1 The above is clearly described in the embodiments of the present invention, so it will not be repeated here.

[0049] In this embodiment, the controller 220 is coupled to the current receiving circuit 112 and the control terminal of the synchronous rectification switch 111. The controller 220 includes a logic control circuit 221. The logic control circuit 221 is coupled to the current receiving circuit 112. The logic control circuit 221 provides a control signal SC for controlling the synchronous rectification switch 111 according to the current signal SCR.

[0050] When the synchronous rectification switch 111 is turned off, when the current signal SCR indicates that the current value of the current ID is greater than the predetermined value TD, the logic control circuit 221 uses the control signal SC to turn on the synchronous rectification switch 111. On the other hand, when the synchronous rectification switch 111 is turned off, when the current signal SCR indicates that the current value of the current ID is less than or equal to the predetermined value TD, the logic control circuit 221 continues to turn off the synchronous rectification switch 111.

[0051] In this embodiment, the controller 220 further includes a voltage determination circuit 222. The voltage determination circuit 222 is coupled to the connection node ND and the logic control circuit 221. The voltage determination circuit 222 determines the detection voltage VD at the connection node ND to generate a determination signal SD, and provides the determination signal SD to the logic control circuit 221.

[0052] In this embodiment, the voltage judgment circuit 222 can be implemented by a comparator. The non-inverting input terminal of the voltage judgment circuit 222 receives the detection voltage VD. The inverting input terminal of the voltage judgment circuit 222 receives the voltage threshold VTH. When the voltage value of the detection voltage VD is higher than the voltage threshold VTH, the voltage judgment circuit 222 provides a judgment signal SD having a first logic value. The logic control circuit 221 will continue to turn off the synchronous rectification switch 111 according to the judgment signal SD having the first logic value. When the voltage value of the detection voltage VD is lower than or equal to the voltage threshold VTH, the voltage judgment circuit 222 provides a judgment signal SD having a second logic value. The logic control circuit 221 will turn on the synchronous rectification switch 111 according to the judgment signal SD having the second logic value.

[0053] Please refer to Figure 3 , Figure 3 3 is a schematic diagram of a power converter according to a third embodiment of the present invention. In this embodiment, the power converter 30 includes a primary side circuit 11, a transformer 12, a secondary side circuit 13 and a synchronous rectification device 300. The synchronous rectification device 300 includes a synchronous rectification circuit 110 and a controller 320. The coupling relationship between the primary side circuit 11, the transformer 12, the secondary side circuit 13 and the synchronous rectification circuit 110 and the implementation method of the synchronous rectification circuit 110 have been described in detail. Figure 1 The above is clearly described in the embodiments of the present invention, so it will not be repeated here.

[0054] In this embodiment, the controller 320 is coupled to the current receiving circuit 112 and the control terminal of the synchronous rectification switch 111 . The controller 320 includes a logic control circuit 321 , a voltage determination circuit 322 and a sensing circuit 323 .

[0055] In this embodiment, the sensing circuit 323 is coupled to the current receiving circuit 112 and the logic control circuit 321. The sensing circuit 323 generates a sensing signal SS according to the current signal SCR from the current receiving circuit 112, and provides the sensing signal SS to the logic control circuit 321. In this embodiment, the logic control circuit 221 includes a flip-flop FF. The setting terminal S of the flip-flop FF is coupled to the sensing circuit 323. The reset terminal R of the flip-flop FF is coupled to the voltage determination circuit 322. The output terminal Q of the flip-flop FF is coupled to the control terminal of the synchronous rectification switch 111.

[0056] In this embodiment, the sensing circuit 323 determines the current value of the current ID. When the current value of the current ID is higher than the predetermined value TD, the sensing circuit 323 generates a sensing signal SS with a high logic value. On the other hand, when the current value of the current ID is lower than or equal to the predetermined value TD, the sensing circuit 323 generates a sensing signal SS with a low logic value.

[0057] In addition, when the voltage value of the detection voltage VD is higher than the voltage threshold VTH, the voltage judgment circuit 322 provides a judgment signal SD having a high logic value. On the other hand, when the voltage value of the detection voltage VD is lower than or equal to the voltage threshold VTH, the voltage judgment circuit 322 provides a judgment signal SD having a low logic value.

[0058] In this embodiment, when the voltage value of the detection voltage VD is lower than or equal to the voltage threshold VTH and the current value of the current ID is higher than the predetermined value TD, the flip-flop FF outputs a control signal SC (i.e., a signal with a high logic value) to turn on the synchronous rectification switch 111. When the voltage value of the detection voltage VD is higher than the voltage threshold VTH, the flip-flop FF turns off the synchronous rectification switch 111. In addition, when the current value of the current ID is lower than or equal to the predetermined value TD, the flip-flop FF also turns off the synchronous rectification switch 111.

[0059] In summary, the synchronous rectification device includes a synchronous rectification circuit and a controller 120. The synchronous rectification circuit includes a synchronous rectification switch and a current receiving circuit. The current receiving circuit provides a current signal according to the current flowing through the synchronous rectification switch. The controller controls the synchronous rectification switch according to the current signal. In this way, the synchronous rectification device can accurately perform the synchronous rectification operation of the power converter according to the current flowing through the synchronous rectification switch. In addition, the synchronous rectification switch and the current receiving circuit are made in a single semiconductor die. The controller and the synchronous rectification circuit are packaged in the same circuit package. In this way, the synchronous rectification device can be assembled into the power converter.

[0060] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the appended claims.

Claims

1. A synchronous rectification device for a power converter, characterized in that: The power converter comprises a secondary side circuit and a transformer, wherein the synchronous rectification device comprises: A synchronous rectification circuit, comprising: a synchronous rectification switch coupled between the secondary side circuit and the secondary side winding of the transformer; and a current receiving circuit configured to receive a current flowing through the synchronous rectification switch and provide a current signal according to the current; and a controller, coupled to the current receiving circuit and the control end of the synchronous rectification switch, and configured to control the synchronous rectification switch according to the current signal, Wherein, in the case where the synchronous rectification switch is turned off, when the current signal indicates that the current value of the current is greater than a predetermined value, the controller turns on the synchronous rectification switch.

2. The synchronous rectification device according to claim 1, characterized in that: In the case where the synchronous rectification switch is turned off, when the current signal indicates that the current value of the current is less than or equal to the predetermined value, the controller continues to turn off the synchronous rectification switch.

3. The synchronous rectification device according to claim 1, characterized in that: The controller comprises: The logic control circuit is coupled to the current receiving circuit and is configured to provide a control signal for controlling the synchronous rectification switch according to the current signal.

4. The synchronous rectification device according to claim 3, characterized in that: The synchronous rectification switch and the secondary winding are connected at a connection node, and The controller further comprises: The voltage determination circuit is coupled to the connection node and the logic control circuit, and is configured to determine the detection voltage at the connection node to generate a determination signal, and provide the determination signal to the logic control circuit.

5. The synchronous rectification device according to claim 4, characterized in that: The controller further comprises: The sensing circuit is coupled to the current receiving circuit and the logic control circuit, and is configured to generate a sensing signal according to the current signal and provide the sensing signal to the logic control circuit.

6. The synchronous rectification device according to claim 5, characterized in that: The logic control circuit comprises: A flip-flop, wherein a setting end of the flip-flop is coupled to the sensing circuit, a reset end of the flip-flop is coupled to the voltage judgment circuit, and an output end of the flip-flop is coupled to the control end of the synchronous rectification switch.

7. The synchronous rectification device according to claim 6, characterized in that: The sensing circuit determines the current value of the current, When the current value of the current is higher than a predetermined value, the sensing circuit generates the sensing signal having a high logic value, and When the current value of the current is lower than or equal to the predetermined value, the sensing circuit generates the sensing signal having a low logic value.

8. The synchronous rectification device according to claim 6, characterized in that: When the voltage value of the detection voltage is higher than the voltage threshold, the voltage judgment circuit provides the judgment signal with a high logic value, and When the voltage value of the detection voltage is lower than or equal to the voltage threshold, the voltage determination circuit provides the determination signal having a low logic value.

9. The synchronous rectification device according to claim 1, characterized in that: The synchronous rectification switch and the current receiving circuit are fabricated in a single semiconductor die.

10. The synchronous rectification device according to claim 9, characterized in that: The controller and the semiconductor die are packaged in the same circuit package.

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