Half-bridge self-driven synchronous rectification circuit

Abstract

The invention provides a half-bridge self-driven synchronous rectification circuit. The synchronous rectification circuit comprises a first switching tube, a second switching tube, a transformer, a capacitor, a load resistor, a first driving circuit and a second driving circuit, under the condition that the first switching tube is switched on and the second switching tube is switched off, a first triode, a third triode and a fourth triode in the first driving circuit are switched on, and a second triode and a fifth triode in the first driving circuit are switched off; a first triode, a second triode and a fifth triode in the second driving circuit are switched on, and a third triode and a fourth triode in the second driving circuit are switched off; under the condition that the first switching tube is switched off and the second switching tube is switched on, a first triode, a second triode and a fifth triode in the first driving circuit are switched on, and a third triode and a fourth triode are switched off; and a first triode, a third triode and a fourth triode in the second driving circuit are switched on, and a second triode and a fifth triode in the second driving circuit are switched off.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and in particular to a half-bridge self-driven synchronous rectifier circuit. Background Technology

[0002] In rectifier circuits, using MOSFETs with low on-resistance is an effective way to improve system power conversion efficiency. To achieve synchronous rectification using MOSFETs, the magnitude and timing of the drive signal must be strictly designed. The drive signal determines the overall quality and efficiency of the converter.

[0003] Existing synchronous rectification drive circuits are generally divided into voltage-type drive and current-type drive. However, voltage-type drive circuits are easily affected by the input voltage range, which can cause the synchronous rectifier tube to be driven by too high a voltage, resulting in gate damage. Current-type drive circuits, on the other hand, require components such as current transformers to detect the current and provide the drive signal, resulting in a complex structure and large size. Summary of the Invention

[0004] This invention provides a half-bridge self-driven synchronous rectifier circuit that can solve the technical problems in the prior art.

[0005] This invention provides a half-bridge self-driven synchronous rectifier circuit, the synchronous rectifier circuit including a first switching transistor, a second switching transistor, a transformer, a capacitor, a load resistor, a first driving circuit, and a second driving circuit;

[0006] The same-zero terminal of the secondary side of the transformer is connected to the drain of the first switching transistor, and the opposite-zero terminal of the secondary side is connected to the drain of the second switching transistor; the capacitor and the load resistor are connected in parallel, with the first end of the parallel connection connected to the middle terminal of the secondary side of the transformer and the second end connected to the source of the second switching transistor; the source of the first switching transistor is connected to the source of the second switching transistor; the first driving circuit is used to drive the first switching transistor, and the second driving circuit is used to drive the second switching transistor;

[0007] The first driving circuit includes a first resistor, a second resistor, a third resistor, a first diode, a second diode, a third diode, a fourth diode, a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, and a third switching transistor. The base of the first transistor is connected to the base of the second transistor and the anode of the third diode, respectively. The collector is connected to the first terminal of the first resistor and its own base, respectively. The emitter is connected to the anode of the first diode. The cathode of the first diode serves as the first connection point of the first driving circuit and is connected to the drain of the first switching transistor. The base of the fourth transistor is connected to the base of the fifth transistor, the emitter of the third transistor, and the anode of the fourth diode, respectively. The emitter is connected to the emitter of the fifth transistor and serves as... The second connection point of the first driving circuit is connected to the gate of the first switching transistor, and the collector is connected to the second terminal of the first resistor, the collector of the third transistor, and the first terminal of the second resistor, and is at a high level. The collector of the second transistor is connected to the base of the third transistor, the second terminal of the second resistor, the cathode of the fourth diode, the cathode of the third diode, and the drain of the third switching transistor, and the emitter is connected to the anode of the second diode. The cathode of the second diode is connected to the source of the third switching transistor and the collector of the fifth transistor, and then serves as the third connection point of the first driving circuit and the source of the first switching transistor. The first terminal of the third resistor is connected to the gate of the third switching transistor, and the second terminal serves as the fourth connection point of the first driving circuit and is connected to the gate of the second switching transistor.

[0008] The second driving circuit has the same structure as the first driving circuit. The first connection point of the second driving circuit is connected to the drain of the second switching transistor, the second connection point is connected to the gate of the second switching transistor, the third connection point is connected to the source of the second switching transistor, and the fourth connection point is connected to the gate of the first switching transistor.

[0009] When the first switch is on and the second switch is off, the first transistor, the third transistor, and the fourth transistor in the first driving circuit are on, and the second transistor and the fifth transistor are off; when the first transistor, the second transistor, and the fifth transistor in the second driving circuit are on, the third transistor and the fourth transistor are off.

[0010] When the first switch is off and the second switch is on, the first transistor, the second transistor, and the fifth transistor in the first driving circuit are on, and the third transistor and the fourth transistor are off; in the second driving circuit, the first transistor, the third transistor, and the fourth transistor are on, and the second transistor and the fifth transistor are off.

[0011] Preferably, the first and second switching transistors are power switching transistors, and the third switching transistor is a signal switching transistor.

[0012] Preferably, the first diode and the second diode have exactly the same characteristics.

[0013] Preferably, the third diode and the fourth diode are Schottky diodes.

[0014] Preferably, the first transistor, the second transistor, the third transistor, and the fourth transistor are NPN transistors, and the fifth transistor is a PNP transistor.

[0015] Preferably, the first transistor and the second transistor have exactly the same characteristics.

[0016] By applying the technical solution of this invention, the drive circuit realizes the automatic turn-on and turn-off of the synchronous rectifier diodes (first and second switching diodes) by detecting the drain-source voltage of the synchronous rectifier diodes. The faster start-up speed reduces the diode conduction time and dead time, thereby improving the rectification efficiency. At the same time, the reverse clamping circuit realizes the interlocking of the drive signal, preventing the two synchronous rectifier diodes from conducting simultaneously. Attached Figure Description

[0017] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0018] Figure 1 A schematic diagram of a half-bridge self-driven synchronous rectifier circuit according to an embodiment of the present invention is shown. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0022] like Figure 1 As shown, the present invention provides a half-bridge self-driven synchronous rectifier circuit, the synchronous rectifier circuit including a first switch Q1, a second switch Q2, a transformer T1, a capacitor C1, a load resistor R0, a first driving circuit and a second driving circuit;

[0023] The same-zero terminal of the secondary side of transformer T1 is connected to the drain of the first switching transistor Q1, and the opposite-zero terminal of the secondary side is connected to the drain of the second switching transistor Q2; the capacitor C1 and the load resistor R0 are connected in parallel, with the first end of the parallel connection connected to the middle terminal of the secondary side of transformer T1, and the second end connected to the source of the second switching transistor Q2; the source of the first switching transistor Q1 is connected to the source of the second switching transistor Q2; the first driving circuit is used to drive the first switching transistor Q1, and the second driving circuit is used to drive the second switching transistor Q2;

[0024] The first driving circuit includes a first resistor R1, a second resistor R2, a third resistor R3, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first transistor V1, a second transistor V2, a third transistor V3, a fourth transistor V4, a fifth transistor V5, and a third switching transistor Q3. The base of the first transistor V1 is connected to the base of the second transistor V2 and the anode of the third diode D3, respectively. The collector is connected to the first terminal of the first resistor R1 and its own base, respectively. The emitter is connected to the anode of the first diode D1. The cathode of the first diode D1 serves as the first connection point of the first driving circuit and is connected to the drain of the first switching transistor Q1. The base of the fourth transistor V4 is connected to the base of the fifth transistor V5, the emitter of the third transistor V3, and the anode of the fourth diode D4, respectively. The emitter is connected to the anode of the fifth transistor V5. After the emitter is connected, it serves as the second connection point of the first driving circuit and is connected to the gate of the first switch Q1. The collector is connected to the second terminal of the first resistor R1, the collector of the third transistor V3, and the first terminal of the second resistor R2, and is at a high level. The collector of the second transistor V2 is connected to the base of the third transistor V3, the second terminal of the second resistor R2, the cathode of the fourth diode D4, the cathode of the third diode D3, and the drain of the third switch Q3. The emitter is connected to the anode of the second diode D2. The cathode of the second diode D2 is connected to the source of the third switch Q3 and the collector of the fifth transistor V5, and then serves as the third connection point of the first driving circuit and is connected to the source of the first switch Q1. The first terminal of the third resistor R3 is connected to the gate of the third switch Q3, and the second terminal serves as the fourth connection point of the first driving circuit and is connected to the gate of the second switch Q2.

[0025] The second driving circuit has the same structure as the first driving circuit. The first connection point of the second driving circuit is connected to the drain of the second switching transistor Q2, the second connection point is connected to the gate of the second switching transistor Q2, the third connection point is connected to the source of the second switching transistor Q2, and the fourth connection point is connected to the gate of the first switching transistor Q1.

[0026] When the first switch Q1 is on and the second switch Q2 is off, the first transistor V1, the third transistor V3, and the fourth transistor V4 in the first driving circuit are on, while the second transistor V2 and the fifth transistor are off; in the second driving circuit, the first transistor V1, the second transistor V2, and the fifth transistor are on, while the third transistor V3 and the fourth transistor V4 are off; at this time, it is in the positive half-cycle of rectification, V A Greater than V B And VC Less than V D ;

[0027] When the first switch Q1 is off and the second switch Q2 is on, the first transistor V1, the second transistor V2, and the fifth transistor in the first driving circuit are on, while the third transistor V3 and the fourth transistor V4 are off; in the second driving circuit, the first transistor V1, the third transistor V3, and the fourth transistor V4 are on, while the second transistor V2 and the fifth transistor are off; at this time, it is in the negative half-cycle of rectification, V A Less than V B And V C Greater than V D This enables self-driven synchronous rectification control of the secondary half-bridge.

[0028] This invention achieves automatic turn-on and turn-off of the synchronous rectifier diodes (first and second switching diodes) by detecting the drain-source voltage of the diodes. The faster start-up speed reduces the diode conduction time and dead time, thus improving rectification efficiency. Simultaneously, the reverse clamping circuit interlocks the drive signals, preventing the simultaneous conduction of both synchronous rectifier diodes.

[0029] In this invention, the first switch Q1, the second switch Q2, the transformer T1, the capacitor C1, and the load resistor R0 constitute a secondary half-bridge rectifier circuit; the first driving circuit and the second driving circuit drive the first switch Q1 and the second switch Q2, respectively.

[0030] According to one embodiment of the present invention, the first resistor R1, the second resistor R2, the first diode D1, the second diode D2, the first transistor V1, and the second transistor V2 in the first driving circuit and the second driving circuit constitute a mirror voltage sampling circuit for acquiring the voltage across the first switching transistor Q1. The first diode D1 and the second diode D2 have the same characteristics, and the first transistor V1 and the second transistor V2 have the same characteristics.

[0031] According to one embodiment of the present invention, the first transistor V1, the second transistor V2, the third transistor V3, and the fourth transistor V4 in the first driving circuit and the second driving circuit are NPN transistors, and the fifth transistor V5 is a PNP transistor. Therefore, the fourth transistor V4 and the fifth transistor V5 constitute a totem pole driving circuit, and the third transistor V3 is used to improve the driving capability.

[0032] According to one embodiment of the present invention, the third diode and the fourth diode D4 in the first driving circuit and the second driving circuit are Schottky diodes.

[0033] According to one embodiment of the present invention, the third resistor R3 and the third switch Q3 in the first drive circuit and the second drive circuit constitute a reverse clamping circuit, which is used to realize the interlocking of the drive signals of the first switch Q1 and the second switch Q2.

[0034] According to one embodiment of the present invention, the first switch Q1 and the second switch Q2 are power switches, and the third switch Q3 is a signal switch.

[0035] The present invention will now be described in detail using the example of the first driving circuit driving the first switching transistor Q1.

[0036] In this embodiment, when V A Greater than V B At that time, because the base and collector of the first transistor V1 are short-circuited, the base voltage V of the first transistor V1 is... E If the voltage level is high, then the first transistor V1 is turned on. Since the base voltages of the first transistor V1 and the second transistor V2 are equal, then V... E >V V2BE +V D2 +V B (V E V represents the base voltage of the first transistor V1. V2BE This represents the voltage drop between the base and emitter of the second transistor V2. D2 This represents the voltage across the second diode D2, V. B (This represents the source voltage of the first switching transistor Q1), therefore the second transistor V2 is turned on. At this time, the base of the third transistor V3 is pulled low, the third transistor V3 and the fourth transistor V4 are turned off, and the fifth transistor is turned on. The gate voltage V of the first switching transistor Q1 is... g_Q1 When the signal is low, the first switch Q1 is turned off.

[0037] When V A Less than V B At that time, because the base and collector of the first transistor V1 are short-circuited, the base voltage V of the first transistor V1 is... E If the voltage level is high, then the first transistor V1 is turned on. Since the base voltages of the first transistor V1 and the second transistor V2 are equal, then V... E <V V2BE +V D2 +V B Therefore, the second transistor V2 is turned off. At this time, the base of the third transistor V3 is at a high level, the third transistor V3 and the fourth transistor V4 are turned on, the fifth transistor is turned off, and the gate voltage V of the first switching transistor Q1 is... g_Q1 When the signal is high, the first switching transistor Q1 is turned on.

[0038] The second drive circuit of the second switch Q2 is exactly the same as the first drive circuit of the first switch Q1. Similarly, when V C Greater than V D At that time, the gate voltage V of the second switch Q2 g_Q2 When V is low, the second switch Q2 is turned off. C Less than V D At that time, the gate voltage V of the second switch Q2 g_Q2 When the signal is high, the second switch Q2 is turned on.

[0039] Because the gate voltage V of the second switch Q2 g_Q2 When the voltage is high, the third switch Q3 is turned on, the base of the third transistor V3 is pulled low, and the first switch Q1 is turned off, forming an interlock. Similarly, when the gate voltage V of the first switch Q1 is high... g_Q1 When the voltage is high, as can be seen from the reverse clamping circuit, the gate voltage V of the second switch Q2 is... g_Q2 When the voltage is low, the first switch Q1 is turned on and the second switch Q2 is turned off, which avoids the first switch Q1 and the second switch Q2 being turned on at the same time. Furthermore, the Schottky diodes D3 and D4 increase the turn-on speed of the switches and reduce the dead time.

[0040] In summary, this invention provides a half-bridge self-driven synchronous rectifier circuit. By detecting the drain-source voltage of the synchronous rectifier diodes (first and second switching diodes), the driving circuit realizes the automatic turn-on and turn-off of the synchronous rectifier diodes. The faster start-up speed reduces the diode conduction time and dead time, thereby improving rectification efficiency. Simultaneously, the reverse clamping circuit achieves interlocking of the driving signals, preventing the simultaneous conduction of both synchronous rectifier diodes.

[0041] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0042] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0043] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0044] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A half-bridge self-driven synchronous rectifier circuit, characterized in that, The synchronous rectification circuit includes a first switching transistor, a second switching transistor, a transformer, a capacitor, a load resistor, a first driving circuit, and a second driving circuit. The same-zero terminal of the secondary side of the transformer is connected to the drain of the first switching transistor, and the opposite-zero terminal of the secondary side is connected to the drain of the second switching transistor; the capacitor and the load resistor are connected in parallel, with the first end of the parallel connection connected to the middle terminal of the secondary side of the transformer and the second end connected to the source of the second switching transistor; the source of the first switching transistor is connected to the source of the second switching transistor; the first driving circuit is used to drive the first switching transistor, and the second driving circuit is used to drive the second switching transistor; The first driving circuit includes a first resistor, a second resistor, a third resistor, a first diode, a second diode, a third diode, a fourth diode, a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, and a third switching transistor. The base of the first transistor is connected to the base of the second transistor and the anode of the third diode, respectively. The collector is connected to the first terminal of the first resistor and its own base, respectively. The emitter is connected to the anode of the first diode. The cathode of the first diode serves as the first connection point of the first driving circuit and is connected to the drain of the first switching transistor. The base of the fourth transistor is connected to the base of the fifth transistor, the emitter of the third transistor, and the anode of the fourth diode, respectively. The emitter is connected to the emitter of the fifth transistor and serves as... The second connection point of the first driving circuit is connected to the gate of the first switching transistor, and the collector is connected to the second terminal of the first resistor, the collector of the third transistor, and the first terminal of the second resistor, and is at a high level. The collector of the second transistor is connected to the base of the third transistor, the second terminal of the second resistor, the cathode of the fourth diode, the cathode of the third diode, and the drain of the third switching transistor, and the emitter is connected to the anode of the second diode. The cathode of the second diode is connected to the source of the third switching transistor and the collector of the fifth transistor, and then serves as the third connection point of the first driving circuit and the source of the first switching transistor. The first terminal of the third resistor is connected to the gate of the third switching transistor, and the second terminal serves as the fourth connection point of the first driving circuit and is connected to the gate of the second switching transistor. The second driving circuit has the same structure as the first driving circuit. The first connection point of the second driving circuit is connected to the drain of the second switching transistor, the second connection point is connected to the gate of the second switching transistor, the third connection point is connected to the source of the second switching transistor, and the fourth connection point is connected to the gate of the first switching transistor. When the first switch is turned on and the second switch is turned off, the first transistor, the third transistor, and the fourth transistor in the first drive circuit are turned on, while the second transistor and the fifth transistor are turned off. In the second driving circuit, the first transistor, the second transistor, and the fifth transistor are turned on, while the third transistor and the fourth transistor are turned off. When the first switch is off and the second switch is on, the first transistor, the second transistor, and the fifth transistor in the first driving circuit are on, and the third transistor and the fourth transistor are off; in the second driving circuit, the first transistor, the third transistor, and the fourth transistor are on, and the second transistor and the fifth transistor are off.

2. The synchronous rectifier circuit according to claim 1, characterized in that, The first and second switching transistors are power switching transistors, and the third switching transistor is a signal switching transistor.

3. The synchronous rectifier circuit according to claim 1, characterized in that, The first diode and the second diode have exactly the same characteristics.

4. The synchronous rectifier circuit according to claim 1, characterized in that, The third and fourth diodes are Schottky diodes.

5. The synchronous rectifier circuit according to claim 1, characterized in that, The first transistor, the second transistor, the third transistor, and the fourth transistor are NPN transistors, and the fifth transistor is a PNP transistor.

6. The synchronous rectifier circuit according to claims 1 and 5, characterized in that, The first transistor and the second transistor have exactly the same characteristics.

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