Field-effect transistor (FET) based synchronous rectifier for diode simulation

Abstract

The present invention provides a field effect transistor (FET) based synchronous rectifier for simulating a diode, the synchronous rectifier comprising: a first terminal (20) and a second terminal (30); a first FET (M1) and a second FET (M2), wherein the second FET (M2) is adapted to control the operation of the first FET (M1) to thereby allow unidirectional current flow when the two terminals (20, 30) are connected to an external circuit; and wherein the FET based synchronous rectifier comprises a fully integrated single chip device (10) adapted to emulate a diode.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Hong Kong Short-Term Patent Application No. 19130644.8 filed on October 10, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to an electronic component and / or device based on a field effect transistor (FET), and in particular, but not exclusively, to an electronic component and / or device based on a metal oxide semiconductor field effect transistor (MOSFET). Background Art

[0004] Various electronic components including diodes of different configurations are known in the art. Diodes may be found in various electronic applications where a unidirectional flow of current is required. A typical diode comprises two terminals, a cathode and an anode, between which the diode exhibits a low or ideally close to zero resistance in one direction and a high or ideally close to infinite resistance in the other direction. FIG. 1 shows a semiconductor diode of a known type having a p-type semiconductor forming an anode, an n-type semiconductor forming a cathode, and a pn junction therebetween.

[0005] Like many other electronic components, diodes exhibit energy losses during operation, and one of the main parameters that determines the energy losses of a diode is the forward voltage (V f ). According to Ohm's law, the power dissipated by the diode (P d ) can be expressed as follows:

[0006] P d (Power dissipated by the diode) = V f (Forward voltage)*I f (Forward current).

[0007] Power dissipated (P d ) and forward voltage (V f ), therefore, it is desirable to have a low forward voltage (V f ) diodes to thereby reduce power losses. The power losses of the diodes are mostly dissipated in the form of heat, which is undesirable not only because it is a waste of energy but also because the dissipated heat may damage the electronic circuits, which is potentially dangerous.

[0008] Therefore, many electronic components and / or circuit designs have been developed with the goal of reducing the forward voltage (V f). One example is to use a Schottky barrier with a diode, as shown in FIG2 , where a Schottky metal barrier is provided at a metal contact including (in this case) an anode. Although Schottky diodes are known to provide a satisfactory forward voltage (V f ) is reduced, but it exhibits significant reverse current leakage (I r ), which allows current to flow through the diode during the reverse polarization phase. Another example is the use of metal oxide semiconductor field effect transistors (MOSFETs) in a synchronous rectification configuration to simulate the function of a diode, as shown in Figure 3. MOSFET synchronous rectifiers provide a relatively low V f However, typical MOSFET synchronous rectification circuits require a large number of discrete electronic components in complex configurations, which results in bulky structures and complex and expensive processing and / or assembly steps, which is undesirable. Summary of the invention

[0009] It is an object of the present invention to provide a novel FET-based electronic component for simulating the functionality of a diode.

[0010] It is another object of the present invention to alleviate or avoid to some extent one or more problems associated with known diode structures, or to at least provide a useful alternative.

[0011] The above objects are met by the feature combinations of the independent claims; the dependent claims disclose further advantageous embodiments of the invention.

[0012] Those skilled in the art will derive other objects of the present invention from the following description. Therefore, the above object statements are not exhaustive, but are only used to illustrate some of the numerous objects of the present invention.

[0013] The present invention provides a field effect transistor (FET) based synchronous rectifier, which includes: a first terminal and a second terminal; a first FET (M1) and a second FET (M2), wherein the second FET (M2) is suitable for controlling the operation of the first FET (M1) to thereby allow unidirectional current flow when the two terminals are connected to an external circuit; and wherein the FET based synchronous rectifier includes a fully integrated single-chip device suitable for simulating a diode.

[0014] The summary of the invention does not necessarily disclose all features essential to defining the invention; the invention may lie in sub-combinations of the disclosed features. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and further features of the present invention will be apparent from the following description of preferred embodiments, which are provided by way of example only in conjunction with the accompanying drawings, in which:

[0016] FIG1 shows a general structure of a semiconductor diode in the prior art;

[0017] FIG2 shows a schematic diagram of a Schottky diode chip in the prior art;

[0018] FIG3 shows a circuit diagram of a MOSFET synchronous rectifier in the prior art;

[0019] Figure 4 is a circuit diagram showing a MOSFET-based synchronous rectifier for diode emulation in the form of a fully integrated single-chip device according to one embodiment of the present invention;

[0020] Figure 5a It shows Figure 4 A schematic cross-sectional view of a chip device;

[0021] Figure 5b It shows Figure 5a A circuit diagram of a cross-sectional view;

[0022] Figure 6 The drain current waveform of the first MOSFET (M1) is shown, simulating the Figure 4 The forward current (I f );

[0023] Figure 7 The drain-source waveform of M1 is shown, simulating the Figure 4 The forward voltage (V f );as well as

[0024] Figure 8 The prior art Schottky diode and Figure 4 Comparison of power dissipation waveforms between the implemented chip devices. DETAILED DESCRIPTION

[0025] What is described below is a preferred embodiment only as an example and is not limited to the combination of features necessary for implementing the invention.

[0026] References in this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor do separate or alternative embodiments exclude other embodiments. Furthermore, various features described may be exhibited by some embodiments and not by others. Similarly, various requirements are described that may be requirements of some embodiments and not others.

[0027] The present invention relates to a field effect transistor (FET), and in particular, but not exclusively, to a synchronous rectifier based on a metal oxide semiconductor field effect transistor (MOSFET), in the form of a fully integrated single chip device for emulating the functionality of a diode. In particular, the present invention provides a structurally simple on-chip device by integrating all required, active and passive electronic components typically associated with a synchronous rectifier diode in a single chip. In one embodiment, the fully integrated single chip device may include equal to or less than 15 discrete electronic devices or components integrated in the chip. The fully integrated chip device of the present invention can be applied and / or assembled in any standard or non-standard electronic package and / or application to function as a diode chip, wherein a significantly lower forward voltage (V f )drop.

[0028] Reference Figure 4 , shows a circuit diagram of a synchronous rectifier based on a metal oxide semiconductor field effect transistor (MOSFET) implemented according to the present invention, which is provided in the form of a fully integrated single-chip device 10 for simulating the function of a diode. In this embodiment, the fully integrated chip device 10 includes two terminals 20, 30, and the two terminals 20, 30 include a first terminal having an anode 20 and a second terminal having a cathode 30. The chip 10 also includes a first FET (such as a first MOSFET (M1)) and a second FET (such as a second MOSFET (M2)). Specifically, the second MOSFET (M2) is suitable for controlling the operation of the first MOSFET (M1) to thereby allow unidirectional current flow when the two terminals 20, 30 are connected to an external circuit to simulate a diode.

[0029] Preferably, the first terminal, i.e., the anode 20, is disposed on a first or top metal surface of the fully integrated single-chip device 10, and the second terminal, i.e., the cathode 30, is disposed on a second or bottom metal surface of the fully integrated single-chip device 10. More preferably, the single-chip device 10 has only two terminals 20, 30, i.e., the anode 20 at the top surface and the cathode 30 at the bottom surface, so that the integrated single-chip device 10 can function as a diode.

[0030] In this embodiment, the first MOSFET (M1) and the second MOSFET (M2) are integrated in the single-chip device 10, so that the second MOSFET (M2) includes a driver for the first MOSFET (M1) to enable the first MOSFET (M1) to operate as a synchronous rectifier. Figure 4 The detailed structure and functions of the implemented on-chip device 10 are shown in FIG.

[0031] Like most MOSFETs, the first MOSFET (M1) of the present invention has at least a first gate electrode, a first source electrode and a first drain electrode; and the second MOSFET (M2) has at least a second gate electrode, a second source electrode and a second drain electrode. Figure 4 In the illustrated embodiment, the second drain electrode of the second MOSFET (M2) is connected in series with the first gate electrode of the first MOSFET (M1).

[0032] In order to enable the integrated chip device 10 to function as a diode, the second MOSFET (M2) is configured to remain turned on when the voltage at the first drain electrode of the first MOSFET (M1) is a positive voltage, and the second MOSFET (M2) is configured to remain turned off when the voltage at the first drain electrode of the first FET (M1) is a negative voltage. This provides a clear difference in operating principle from the MOSFET-based diode structure of the prior art: the fully integrated chip device 10 utilizes M2 to control M1 to operate as a synchronous rectifier MOSFET, while other MOSFET solutions in the prior art require the use of at least one separate, operational integrated circuit to control the synchronous rectifier MOSFET, and the at least one separate, operational integrated circuit includes a very large number of other discrete electronic components electrically connected thereto, which has a considerable impact on assembly and cost.

[0033] Preferably, the circuit of the chip device 10 of the present invention can be configured as follows: the second source electrode of the second MOSFET (M2) and the first source electrode of the first MOSFET (M1) are connected to the anode 20; and the first drain electrode of the first MOSFET (M1) is connected to the cathode 30. More preferably, the chip device 10 may also include: a first diode (D1) and a first resistor (R1), which are connected in series between the second drain electrode of the second MOSFET (M2) and the cathode 30; a first capacitor (C1), which is connected in series between the first diode (D1) and the second source electrode of the second MOSFET (M2); and a second resistor (R2) and a second diode (D2), which are connected in parallel with the first capacitor (C1) and the first diode (D1) between the anode 20 and the cathode 30. More preferably, the second resistor (R2) is connected in series with the second gate electrode of the second MOSFET (M2); and the circuit may further include a third diode (D3) connected in parallel with the first MOSFET (M1), such as Figure 4 as shown in .

[0034] In one embodiment, the integrated capacitor (C1) is adapted to act as a voltage pump or a current pump, so that the capacitor (C1) will be charged at the beginning stage of the input sinusoidal waveform, and the charged voltage will be used by the second MOSFET (M2) to drive the operation of the first MOSFET (M1).

[0035] Figure 5a A schematic diagram of a cross section of the fully integrated on-chip device 10 is further shown; Figure 5b Components shown in the cross-sectional view are shown in dashed lines, as well as their interconnection in the form of a circuit diagram.

[0036] When operating as an analog diode, the fully integrated single-chip device 10 does not require connection to any one or more of an external power FET and / or a control integrated circuit (IC) having one or more active and / or passive electronic components to control the MOSFET. This is in contrast to MOSFET synchronous rectifiers in the prior art, which typically require at least one or more external power MOSFETs, a control integrated circuit and / or several other discrete components in order to, for example, be able to control the MOSFET via the integrated circuit. All required active and / or passive components are integrated into the single-chip device 10 of the present invention, and these active and / or passive components may include equal to or less than 15 discrete electronic devices or components integrated into the chip, for example so that the device can be provided with an analog diode in a simple and compact on-chip structure. As Figure 5aAs further shown in FIG. 1 , the first MOSFET ( M1 ) is preferably integrated in the single-chip device 10 for vertical operation, while all other components are integrated in the single-chip device 10 for horizontal operation.

[0037] As discussed, the single-chip device 10 is able to simulate the function of a diode based on its MOSFET synchronous rectification configuration, which allows the first MOSFET (M1) to enter the on-phase when its drain electrode is negatively polarized; and enter the blocking phase when the polarization of its drain electrode switches from negative polarization to positive polarization. In particular, during the on-phase, the drain-source resistance can be very low, which makes the voltage between the drain electrode and the source electrode of M1 become very low. In one embodiment, this low voltage (which is equivalent to the forward voltage (V f ))For example, more than 90% of the time during the on-time can be equal to or lower than about 0.3 volts (V), and preferably more than 90% of the time during the on-time can be less than or equal to about 0.1 volts (V), and more preferably, more than 90% of the time during the on-time is in the range of about 80mV to about 90mV.

[0038] To verify that the single chip device 10 has a low V f A series of simulations have been performed to demonstrate the functionality of the diode simulator. For example, Figure 6 and Figure 7 The waveform exhibited by a simulated diode during switching from on to off is shown when the circuit of chip arrangement 10 is biased by a sinusoidal waveform generator. Figure 8 The power dissipation waveform of the first MOSFET (M1) of the chip device 10 of the present invention is further compared with the power dissipation waveform of the Schottky diode as shown in FIG. 2. The results clearly show that the simulated diode of the present invention can achieve a significant reduction in power loss. According to Ohm's law, the chip device 10 of the simulated diode dissipates a peak power loss of about 9.5W; while the equivalent Schottky diode typically dissipates a power loss of about 52.5W, which is equivalent to about 5.5 times the power loss of the simulated diode of the present invention.

[0039] The present invention is therefore advantageous in that it provides a simple MOSFET-based synchronous rectifier for emulating the function of a diode, wherein a significantly lower forward voltage (V) is achieved when compared to known alternative diode arrangements. f) drop. In particular, the present invention utilizes a second MOSFET (M2) to control the operation of a first MOSFET (M1) configured in a synchronous rectification arrangement, which is different from the prior art MOSFET synchronous rectifiers in which the MOSFET is controlled by at least one separate operating integrated circuit having a large number of discrete electronic components connected thereto. It has been demonstrated, for example, that for a voltage less than 30 mm 2 or about 30mm 2 With a chip size of 100%, conventional silicon diodes and / or Schottky diodes can achieve a low V of about 0.3V to 1V at most at high currents above 3A. f By means of the present invention, under the same conditions, a much lower V of less than or equal to about 0.1 V can be achieved during more than 90% of the on-time. f value, and thus a significant reduction in power loss is achieved. It has been found that the V f About 5.5 times lower than a conventional Schottky diode, or in other words, the present invention requires a smaller chip size of about 1 / 5.5 or less to provide the same power during operation. The present invention also exhibits superior performance with much lower reverse leakage at high temperatures, which can prevent thermal runaway when the simulated diode is operated at high temperatures. In addition, compared with the processing steps of Schottky diodes and / or MOSFET diodes in the prior art, the present invention also makes the manufacturing and / or assembly process relatively simple, which provides a reduction in related manufacturing costs.

[0040] The principles of the invention are explained in the specification. It will therefore be appreciated that those skilled in the art will be able to conceive of various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within the spirit and scope of the invention.

[0041] In addition, all descriptions of the principles, aspects and embodiments of the present invention recorded herein and their specific embodiments are intended to include equivalents in structure and function. In addition, it is intended that such equivalents include currently known equivalents and equivalents developed in the future, i.e. any element developed to perform the same function regardless of its structure.

[0042] Although the present invention has been described and illustrated in detail in the accompanying drawings and the foregoing description, it should be regarded as illustrative rather than restrictive in words, and it should be understood that only exemplary embodiments are shown and described, and these exemplary embodiments do not limit the scope of the present invention in any way. It is understood that any feature described herein can be used in any embodiment. The illustrative embodiments are not mutually exclusive or exclusive of other embodiments not recorded herein.

[0043] Therefore, the present invention also provides embodiments including combinations of one or more of the above illustrative embodiments. Modifications and variations may be made to the present invention as set forth herein without departing from the spirit and scope of the present invention, and therefore only such limitations should be imposed as indicated by the appended claims.

[0044] In the claims of the present invention, any element shown as a means for performing a particular function is intended to encompass any manner of performing that function. The invention defined by the claims is that the functions provided by the various recited means are combined and brought together in the manner required by the claims. Therefore, any means capable of providing these functions are considered equivalent to the means shown herein.

[0045] In the appended claims and the foregoing description of the present invention, unless the context requires otherwise due to explicit language or necessary implication, the word "comprise" or variations such as "including" or "comprising" are used in an inclusive sense, that is, to indicate the presence of the features described, but not to exclude the presence or presence of further features in various embodiments of the present invention.

[0046] It will be appreciated that if any prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art.

Claims

1. A synchronous rectifier based on a field effect transistor (FET), characterized in that: The synchronous rectifier includes: a first terminal and a second terminal; a first field effect transistor (M1) and a second field effect transistor (M2); wherein the second field effect transistor (M2) is adapted to control the operation of the first field effect transistor (M1), thereby allowing a unidirectional current flow when the first terminal and the second terminal are connected to an external circuit; and wherein the field effect transistor based synchronous rectifier comprises a fully integrated single chip device adapted to emulate a diode; The first field effect transistor (M1) at least has a first gate electrode, a first source electrode and a first drain electrode; the second field effect transistor (M2) at least has a second gate electrode, a second source electrode and a second drain electrode; the second drain electrode of the second field effect transistor (M2) is connected in series with the first gate electrode of the first field effect transistor (M1); a first diode (D1) and a first resistor (R1), the first diode and the first resistor being connected in series between a second drain electrode and a second terminal of the second field effect transistor (M2); and a first capacitor (C1) connected in series between the first diode (D1) and the second source electrode of the second field effect transistor (M2), The field effect transistor based synchronous rectifier further includes a second resistor (R2) and a second diode (D2) connected in parallel with the first capacitor (C1) and the first diode (D1) between the first terminal and the second terminal, wherein the second resistor (R2) is connected in series with the second gate electrode of the second field effect transistor (M2); and The second resistor (R2) is directly connected to the second terminal, and the second diode (D2) is directly connected to the first terminal.

2. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The fully integrated single-chip device includes equal to or less than 15 discrete electronic devices or components integrated into the chip.

3. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The first terminal is disposed on a first or top metal surface of the fully integrated single-chip device, and the second terminal is disposed on a second or bottom metal surface of the fully integrated single-chip device.

4. The synchronous rectifier based on field effect transistor according to claim 3, characterized in that: The first or top metal surface of the fully integrated single-chip device includes an anode and the second or bottom metal surface of the fully integrated single-chip device includes a cathode.

5. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The field effect transistor based synchronous rectifier is used to emulate a diode, wherein the single chip device has only two terminals.

6. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The first field effect transistor (M1) includes a first metal oxide semiconductor field effect transistor (MOSFET), and the second field effect transistor (M2) includes a second metal oxide semiconductor field effect transistor (MOSFET).

7. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The first field effect transistor (M1) and the second field effect transistor (M2) are integrated in the single chip device, whereby the second field effect transistor (M2) includes a driver for the first field effect transistor (M1) to enable the first field effect transistor (M1) to operate as a synchronous rectifier.

8. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The second field effect transistor (M2) is configured to remain turned on when the voltage at the first drain electrode of the first field effect transistor (M1) is a positive voltage, and the second field effect transistor (M2) is configured to remain turned off when the voltage at the first drain electrode of the first field effect transistor (M1) is a negative voltage.

9. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The second source electrode of the second field effect transistor (M2) and the first source electrode of the first field effect transistor (M1) are connected to the first terminal.

10. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The first drain electrode of the first field effect transistor (M1) is connected to the second terminal.

11. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The synchronous rectifier also includes a third diode (D3) connected in parallel with the first field effect transistor (M1).

12. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The field effect transistor based synchronous rectifier exhibits a forward voltage drop of less than or equal to 0.3 volts for more than 90% of the on-time when simulating a diode.

13. The synchronous rectifier based on field effect transistor according to claim 12, characterized in that: The forward voltage drop of the simulated diode is less than or equal to 0.1 volt during more than 90% of the on-time.

14. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The fully integrated single chip device, when operating as a simulated diode, does not require connection to any one or more of an external power field effect transistor, a control integrated circuit (IC), and one or more passive components to control the first field effect transistor.

15. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: All of the one or more active and passive components required to enable the device to emulate a diode are integrated into the fully integrated single-chip device.

16. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The first field effect transistor (M1) is integrated in the single chip device to have a vertical operation, while all other components are integrated in the single chip device to have a horizontal operation.

17. The synchronous rectifier based on field effect transistor according to claim 1, characterized in that: The first capacitor (C1) is adapted to act as a voltage pump or a current pump, whereby the capacitor (C1) is adapted to be charged at the beginning of an input sinusoidal waveform, and the charged voltage is subsequently used by the second field effect transistor (M2) to drive the operation of the first field effect transistor (M1).

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