Control circuit of ideal diode

Abstract

The invention discloses a control circuit of an ideal diode, and relates to the technical field of diode control circuits, the control circuit comprises a mosfet Q6, a voltage ratio circuit, a mirror current source circuit providing different bias currents and a fast turn-off circuit, the mirror current source circuit controls and distributes the current in the voltage ratio circuit, and the fast turn-off circuit is used for turning off the current in the voltage ratio circuit. Different bias currents are provided through the mirror current source, the forward conduction voltage drop between the source electrode and the drain electrode of the mosfet is adjusted through the difference between the currents, when the currents flow in the reverse direction, discharging of the grid electrode of the mosfet can be accelerated through two-stage amplification of the currents, and therefore the forward conduction voltage value of the mosfet Q6 is effectively controlled. The mosfet is quickly closed, the switching process of the mosfet can be accurately controlled to change along with the change of the current, and single-phase flow of the current and extremely low VF voltage can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of diode control circuits, in particular to a control circuit for an ideal diode. Background Art

[0002] With the development of new energy technology, new requirements are brought about for low-voltage, high-current and system reliability. Dual-channel backup is usually designed with diode or MOS tube ORing circuit. Due to the large heat loss of diode, it is not suitable for large current occasions. ORing current uses MOS tube as diode semiconductor device and adds control circuit for control. MOS is a device that can conduct in both directions after being turned on. It needs to be turned off in time when the current is reversed to achieve precise control and achieve the effect of ideal diode, so the control circuit is particularly important. Summary of the invention

[0003] The purpose of the present invention is to provide a control circuit of an ideal diode, which adopts discrete semiconductor devices to accurately control the switching process of MOSFET as the current changes, adopts MOSFET as the main path of current flow, and accurately controls the gate voltage of MOSFET to solve the problems raised in the above background technology.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a control circuit of an ideal diode, comprising a mosfet Q6, a voltage comparison circuit, a mirror current source circuit providing different bias currents, and a fast shutdown circuit, wherein the voltage comparison circuit is connected between the source and the drain of the mosfet Q6, the mirror current source circuit controls and distributes the current in the voltage comparison circuit, adjusts the source and drain voltage difference of the mosfet Q6 at any time, and effectively controls the forward conduction voltage value of the mosfet Q6, and the fast shutdown circuit accelerates the discharge of the gate of the mosfet Q6 by two-stage amplification of the current, thereby realizing the fast shutdown of the mosfet Q6, and can achieve the precise control of the switching process of the mosfet Q6 changing with the change of the current.

[0005] Preferably, the mirror current source circuit includes resistors R1 and R2, transistors Q1 and Q2, one end of the resistor R1 is connected to the positive pole of the power supply, and the other end is connected to the emitter of the transistor Q1, one end of the resistor R2 is connected to the positive pole of the power supply, and the other end is connected to the emitter of the transistor Q2.

[0006] Preferably, the voltage comparison circuit includes a transistor Q3 and a transistor Q4, a diode D2 and a diode D3, the collector of the transistor Q3 is connected to the collector of the transistor Q1, the emitter of the transistor Q3 is connected to the anode of the diode D2, the cathode of the diode D2 is connected to the source of the mosfet Q6, the base and collector of the transistor Q4 are connected to each other, the emitter of the transistor Q4 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the drain of the mosfet Q6.

[0007] Preferably, the fast shutdown circuit includes a crystal diode D1, a resistor R3 and a crystal triode Q5, one end of the resistor R3 is connected to the collector of the crystal triode Q1, and the other end is connected to the gate of the mosfet Q6, the emitter of the crystal triode Q5 is connected to the resistor R3, the collector of the crystal triode Q5 is connected to the source of the mosfet Q6, the base of the crystal triode Q5 is connected to the collector of the crystal triode Q3, the crystal diode D1 is connected in series between the emitter of the crystal triode Q5 and the base of the crystal triode Q5, the anode of the crystal diode D1 is connected to the base of the crystal triode Q5, and the cathode of the crystal diode D1 is connected to the emitter of the crystal triode Q5.

[0008] Preferably, the voltage comparison circuit also includes a resistor R4 and a resistor R5, one end of the resistor R4 is connected to the base of the transistor Q3, and the other end is connected to the base of the transistor Q4, one end of the resistor R5 is connected to the collector of the transistor Q4, and the other end is connected to the collector of the transistor Q2.

[0009] Preferably, the collector of the transistor Q3 and the common end connected to the transistor Q1 are connected to the base of the transistor Q3, and a capacitor C1 is connected in series in between.

[0010] Preferably, the bases of the transistor Q1 and the transistor Q2 are connected to each other, and the common end point of the connection is connected to the collector of the transistor Q2.

[0011] Preferably, the transistor Q1 , the transistor Q2 , and the transistor Q5 are all of PNP type, and the transistor Q3 and the transistor Q4 are of NPN type.

[0012] Preferably, when facing a large current, multiple MOSFETs Q6 are arranged in parallel.

[0013] In summary, the beneficial effects of the present invention are: 1. The present invention provides different bias currents through a mirror current source, and uses the difference between the currents to adjust the forward conduction voltage drop between the source and drain of the mosfet. Moreover, when the current flows in the reverse direction, the discharge of the gate of the mosfet can be accelerated by a two-stage amplification of the current, so as to realize the rapid shutdown of the mosfet, and can achieve the precise control of the switching process of the mosfet with the change of the current, so as to realize the single-phase flow of the current and extremely low VF voltage. The traditional silicon diode generally has a voltage drop of 0.7V. If it is under a large current (such as greater than 100A), it may have a voltage drop greater than 1V. At this time, the power consumption of the diode has a loss of 100W. The ideal diode can control the VF voltage to be less than 50mV, and can be widely used in the reverse injection occasions of the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 This is a schematic diagram of the overall structure of a control circuit for an ideal diode of the present invention; Figure 2 A schematic diagram of a conventional silicon diode control circuit of an ideal diode control circuit of the present invention; Figure 3 The present invention is a schematic diagram of a circuit in which two control circuits of an ideal diode are connected in parallel to supply power to a load. DETAILED DESCRIPTION

[0016] The present invention will now be further described in detail in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. These drawings are all simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic way, and therefore they only show the structures related to the present invention.

[0017] To facilitate understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0018] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0019] Any feature disclosed in this specification (including any additional claims, abstract and drawings), unless otherwise stated, may be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0020] In the present invention, unless otherwise clearly defined and specified, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of at least two elements or the interaction relationship between at least two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] Combine the following Figure 1-3 The present invention is described in detail, and an embodiment is provided: For ease of understanding, the important components of the present invention, MOSFET (metal oxide semiconductor field effect transistor) and triode, are first introduced. MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a very important semiconductor device that is widely used in electronic circuits. There are two main types of MOSFET: N-channel and P-channel. Each type of MOSFET has three main electrodes, namely: Source - This is one of the paths that the current takes into the MOSFET. In an N-channel MOSFET, the source is connected to a lower voltage or ground, whereas in a P-channel MOSFET, the source is connected to a higher voltage.

[0022] Gate - The gate is the key part that controls the conduction and cutoff of the MOSFET. It is isolated from the semiconductor substrate by a very thin layer of insulating material (usually silicon dioxide SiO2). The voltage applied to the gate determines whether the MOSFET is turned on, thereby controlling the current flow between the source and the drain.

[0023] Drain - The drain is the path for current to flow out of the MOSFET. When the gate voltage is high enough to turn the MOSFET on, current can flow from the source to the drain.

[0024] Transistor: widely used in electronic circuits such as amplifier circuits and switch circuits. It has three pins, namely base, collector and emitter. According to different structures, transistors can be divided into two types: NPN type and PNP type.

[0025] Amplification effect: When there is a slight current change between the base and the emitter, this change will be amplified and reflected in the current between the collector and the emitter. This is the amplification effect of the transistor.

[0026] Switching function: By controlling the current of the base, the transistor can be placed in the on state or the off state, thereby realizing the control of the current between the collector and the emitter, playing the role of a switch.

[0027] NPN transistor: When the base is at a positive voltage relative to the emitter, the transistor is turned on; otherwise it is turned off. Applicable to the case where the current flows from the collector to the emitter.

[0028] PNP transistor: Contrary to NPN, when the base is at a negative voltage relative to the emitter, the transistor is turned on; otherwise, it is cut off. It is suitable for the case where the current flows from the emitter to the collector.

[0029] Based on the above components, a control circuit of an ideal diode provided by an embodiment of the present invention is described below in conjunction with the accompanying drawings.

[0030] refer to Figure 1 , a control circuit of an ideal diode, comprising a mosfet Q6, a voltage comparison circuit, a mirror current source circuit providing different bias currents and a fast shutdown circuit, wherein the source of the mosfet Q6 is connected to an external current inflow, and the drain is connected to a current outflow, and the voltage comparison circuit is connected between the source and the drain of the mosfet Q6, the mirror current source circuit controls and distributes the current in the voltage comparison circuit, adjusts the source and drain voltage difference of the mosfet Q6 at any time, and effectively controls the forward conduction voltage value of the mosfet Q6, and the fast shutdown circuit accelerates the discharge of the gate of the mosfet Q6 by using a two-stage amplification of the current, thereby realizing the fast shutdown of the mosfet Q6, and can achieve precise control of the mosfet The switching process of Q6 changes with the change of current, which can realize the single-phase flow of current and extremely low VF voltage. The traditional silicon diode we use generally has a voltage drop of 0.7V. If it is under a large current (such as greater than 100A), it may have a voltage drop greater than 1V. At this time, the power consumption of the diode has a loss of 100W. Figure 3 .

[0031] It is worth mentioning that, in the present embodiment, the mirror current source circuit includes resistors R1 and R2, transistors Q1 and Q2, one end of the resistor R1 is connected to the positive pole of the power supply, and the other end is connected to the emitter of the transistor Q1, one end of the resistor R2 is connected to the positive pole of the power supply, and the other end is connected to the emitter of the transistor Q2, the bases of the transistor Q1 and the transistor Q2 are connected to each other, and the common end point of the connection is connected to the collector of the transistor Q2, the mirror current source composed of R1, R2, Q1, Q2, since R1 and R2 can take different resistance values, the currents passing through R1 and R2 are different, and the currents allocated to the voltage comparison circuit are also different.

[0032] It is also worth mentioning that, in the present embodiment, the voltage comparison circuit comprises a transistor Q3 and a transistor Q4, a diode D2 and a diode D3, a resistor R4 and a resistor R5, the collector of the transistor Q3 is connected to the collector of the transistor Q1, the common end of the transistor Q3 and the transistor Q1 is connected to the base of the transistor Q3, and a capacitor C1 is connected in series in the middle, the emitter of the transistor Q3 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the mosfet The source of Q6 is connected, the base and collector of the transistor Q4 are connected to each other, one end of the resistor R4 is connected to the base of the transistor Q3, and the other end is connected to the base of the transistor Q4, one end of the resistor R5 is connected to the collector of the transistor Q4, and the other end is connected to the collector of the transistor Q2, the emitter of the transistor Q4 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the drain of the mosfet Q6. Since R1 and R2 can take different resistance values, different currents can be allocated to Q3, D2 and Q4, D3. The difference between the currents can make the voltages on the relevant PN nodes different. For example, the sum of the PN junction voltages of Q4 and D3 is adjusted to be greater than the sum of the PN junction voltages of Q3 and D2 by 30mV. In other words, the source of Q6 must be greater than the drain by 30mV, and Q3 will be turned off. If the source of Q6 is less than the drain plus 30mV, Q3 is in the on state. That is to say, when the current on Q6 is 0, the mosfet is in the off state. If Q6 has a relatively small current, the gate driver will try to add a suitable voltage to maintain a 30mV voltage drop, which is very equivalent to the characteristics of a diode, except that this diode has a forward conduction voltage drop of 30mV. By adjusting the ratio between R1 and R2, the forward conduction voltage value can be effectively changed.

[0033] It should be noted that, since the reverse current is uncertain, a faster current may flow in the reverse direction, so it is very necessary to quickly turn off the mosfet. Therefore, a fast shutdown circuit is added in this embodiment, and the two-stage amplification of the current is used to accelerate the discharge of the gate of the mosfet Q6 to achieve the fast shutdown of the mosfet Q6. The fast shutdown circuit includes a crystal diode D1, a resistor R3 and a crystal triode Q5. One end of the resistor R3 is connected to the collector of the crystal triode Q1, and the other end is connected to the gate of the mosfet Q6. The emitter of the crystal triode Q5 is connected to the resistor R3, and the collector of the crystal triode Q5 is connected to the mosfet Q6. The source of the transistor Q6 is connected between the base of the transistor Q5 and the collector of the transistor Q3, the emitter of the transistor Q5 and the base of the transistor Q5 are connected in series with the crystal diode D1, the anode of the crystal diode D1 is connected to the base of the transistor Q5, and the cathode of the crystal diode D1 is connected to the emitter of the transistor Q5; Normally, the input capacitance of this type of current-drawing MOSFET is about 10nF. If you need to operate at a higher current, or even select multiple MOSFETs for parallel design, refer to Figure 3 As shown, multiple power supplies can be used to supply power to the load, and a single power failure does not affect the normal operation of the system. The capacitance will reach 100nF. In general, the base current of Q3 is not designed to be large, usually 1mA, and the amplification factor of Q3 is about 50 times, so the shutdown current of Q3 is 50mA. This current is not fast enough to discharge and shut down Q6. It is necessary to add a current amplifier Q5. The base of Q5 is connected to the power supply VCC ORING through the resistor R3; When the base voltage of Q5 is higher than the emitter voltage, Q5 starts to conduct, allowing current to flow from the collector to the emitter. Due to the characteristics of the transistor, even a small base current can cause a large collector current, thereby achieving current amplification. The turn-off current can be amplified to a current greater than 2A. Q3 acts as the first-stage amplification and Q5 acts as the second-stage amplification. Such a discharge capacity can meet the requirements for the turn-off speed of Q6. It should be noted that the transistor Q1 , the transistor Q2 , and the transistor Q5 are all of PNP type, and the transistor Q3 and the transistor Q4 are of NPN type.

[0034] In specific operation, D2 and Q4 form a common base amplifier comparator. During startup, the mosfet is in the off state, and the current flows from the source of Q6 to the drain, generating a voltage drop of about 1V on Q6. Q3 is in the cut-off state, and the gate of the mosfet is charged through Q1, R3, and D1. When the voltage reaches the turn-on voltage of the mosfet, the current conduction path of the mosfet begins to shift from the parasitic diode to the channel of the mosfet, and the on-resistance begins to play a major role. Due to the extremely low on-resistance, the on-voltage can be very Low; if the current flows in the reverse direction, a voltage greater than the source will be formed on the drain of Q6, which will cause Q3 to turn on faster and discharge the gate of Q6 to achieve the purpose of shutdown. The single-phase flow of current and extremely low VF voltage can be achieved. Traditional silicon diodes generally have a voltage drop of 0.7V. If it is under a large current (such as greater than 100A), it may have a voltage drop greater than 1V. At this time, the power consumption of the diode has a loss of 100W. The ideal diode can control the VF voltage to less than 50mV and can be widely used in the reverse injection occasions of the power supply system.

[0035] The above is only a specific implementation of the invention, but the protection scope of the invention is not limited to it. Any changes or substitutions that are not conceived through creative work should be included in the protection scope of the invention. Therefore, the protection scope of the invention should be based on the protection scope defined in the claims.

Claims

1. A control circuit for an ideal diode, characterized in that: The invention comprises a mosfet Q6, a voltage comparison circuit, a mirror current source circuit providing different bias currents and a fast shutdown circuit, wherein the voltage comparison circuit is connected between the source and the drain of the mosfet Q6, the mirror current source circuit controls and distributes the current in the voltage comparison circuit, adjusts the voltage difference between the source and the drain of the mosfet Q6 at any time, and effectively controls the forward conduction voltage value of the mosfet Q6, while the fast shutdown circuit accelerates the discharge of the gate of the mosfet Q6 by utilizing the two-stage amplification of the current, realizes the fast shutdown of the mosfet Q6, and can achieve the precise control of the switching process of the mosfet Q6 changing with the change of the current.

2. The control circuit of an ideal diode according to claim 1, characterized in that: The mirror current source circuit includes a resistor R1 and a resistor R2, a transistor Q1 and a transistor Q2, one end of the resistor R1 is connected to the positive electrode of the power supply, and the other end is connected to the emitter of the transistor Q1, one end of the resistor R2 is connected to the positive electrode of the power supply, and the other end is connected to the emitter of the transistor Q2.

3. The control circuit of an ideal diode according to claim 2, characterized in that: The voltage comparison circuit includes a transistor Q3 and a transistor Q4, a diode D2 and a diode D3, the collector of the transistor Q3 is connected to the collector of the transistor Q1, the emitter of the transistor Q3 is connected to the anode of the diode D2, the cathode of the diode D2 is connected to the source of the mosfet Q6, the base and collector of the transistor Q4 are connected to each other, the emitter of the transistor Q4 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the drain of the mosfet Q6.

4. The control circuit of an ideal diode according to claim 3, characterized in that: The fast shutdown circuit includes a crystal diode D1, a resistor R3 and a crystal triode Q5, one end of the resistor R3 is connected to the collector of the crystal triode Q1, and the other end is connected to the gate of the mosfet Q6, the emitter of the crystal triode Q5 is connected to the resistor R3, the collector of the crystal triode Q5 is connected to the source of the mosfet Q6, the base of the crystal triode Q5 is connected to the collector of the crystal triode Q3, and the crystal diode D1 is connected in series between the emitter of the crystal triode Q5 and the base of the crystal triode Q5.

5. The control circuit of an ideal diode according to claim 4, characterized in that: The anode of the crystal diode D1 is connected to the base of the crystal triode Q5 , and the cathode of the crystal diode D1 is connected to the emitter of the crystal triode Q5 .

6. The control circuit of an ideal diode according to claim 5, characterized in that: The voltage comparison circuit also includes a resistor R4 and a resistor R5, one end of the resistor R4 is connected to the base of the transistor Q3, and the other end is connected to the base of the transistor Q4, one end of the resistor R5 is connected to the collector of the transistor Q4, and the other end is connected to the collector of the transistor Q2.

7. The control circuit of an ideal diode according to claim 3, characterized in that: The collector of the transistor Q3 and the common end connected to the transistor Q1 are connected to the base of the transistor Q3, and a capacitor C1 is connected in series in the middle.

8. The control circuit of an ideal diode according to claim 2, characterized in that: The bases of the transistor Q1 and the transistor Q2 are connected to each other, and the common end point of the connection is connected to the collector of the transistor Q2.

9. The control circuit of an ideal diode according to claim 8, characterized in that: The transistors Q1 , Q2 and Q5 are all of PNP type, and the transistors Q3 and Q4 are of NPN type.

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