A synchronous rectification unit

Abstract

The embodiment of the application discloses a synchronous rectification unit, which is used in the technical field of integrated circuits and comprises a synchronous rectification integrated circuit and an N-channel field effect transistor Q1; a second input end of a sampling circuit module is connected with the drain of the N-channel transistor Q1 after being connected with a diode D101 in series, and is used for collecting the drain voltage of the N-channel transistor Q1; a third input end of the sampling circuit module is connected with the output end of a trigger voltage conversion module, and the output end is connected with the reference voltage input pole of a three-terminal voltage stabilizing tube IC101 in a comparison circuit module; the comparison output end of the three-terminal voltage stabilizing tube IC101 in the comparison circuit module is connected with the input end of the trigger voltage conversion circuit module; and the output end of a driving circuit module is connected with the gate of the N-channel transistor Q1 through a resistor, and is used for controlling the running state of the N-channel transistor Q1 according to the drain voltage of the N-channel transistor Q1, a first critical trigger voltage value and a second critical trigger voltage value, and the synchronous rectification unit can be applied in a high-voltage direct-current power supply and has high universality.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a synchronous rectification unit. Background Technology

[0002] In recent years, with the development of power supply technology, synchronous rectification technology is being rapidly adopted in low-voltage, high-current output DC / DC converters. Integrated synchronous rectifier controllers, due to their fewer external components and simpler external circuit structure, are widely used in AC-to-DC switching power supplies. An example of an existing integrated synchronous rectifier controller (a schematic diagram of the secondary synchronous rectification in a flyback switching power supply) is shown below. Figure 1 As shown, in the "Synchronous Rectification Control Circuit Module 10," the port connected to VO+ (positive terminal of the output DC voltage) and the port connected to VS (positive terminal of the secondary output of transformer T1) will experience a high voltage U(VO+,VS). In a flyback power supply: U(VO+,VS) = U(VO+,VO-) / D, where D is the duty cycle of the switching power supply drive signal, typically 20% to 30%. Therefore, the voltage U(VO+,VS) is generally 3 to 5 times the output voltage U(VO+,VO-) of the switching power supply. For example, when the output voltage U(VO+,VO-) of the switching power supply is 60V, U(VO+,VS) is typically 180V to 300V.

[0003] Generally, the voltage difference between all ports of the "Synchronous Rectification Control Circuit Module 10" is less than 200V. When the output voltage U(VO+,VO-) of the switching power supply is greater than 60V, existing control integrated circuits are insufficient. For example, in LED lighting, LED chips are connected in series according to different brightness requirements to ensure that each chip has the same current and generates roughly the same amount of heat. The more chips connected in series, the higher the output voltage required to drive the switching power supply. Many applications require a maximum output voltage greater than 60V. Furthermore, existing integrated synchronous rectification controllers are generally used in specific switching power supply topologies corresponding to their model, making it difficult to combine the same model of integrated controller in different topologies, resulting in poor versatility. For instance, the "synchronous rectification control integrated circuit" used in a flyback switching power supply with a single rectifier NMOS transistor cannot be easily combined and applied to a push-pull rectifier circuit with multiple rectifier NMOS transistors; a dedicated push-pull synchronous rectification circuit control IC must be selected separately.

[0004] It is evident that the withstand voltage values ​​of each lead of the existing integrated synchronous rectifier controller are low, making it difficult to apply in high-voltage DC power supplies. Furthermore, the existing integrated synchronous rectifier controllers are generally used in dedicated switching power supply topologies corresponding to their models, making it difficult to combine them in different topologies and resulting in poor versatility. Summary of the Invention

[0005] This application provides a synchronous rectification unit that can be used in high-voltage DC power supplies and has high versatility.

[0006] This application provides a synchronous rectification unit, including: a synchronous rectification integrated circuit and an N-channel transistor Q1; wherein, the synchronous rectification integrated circuit includes: a reference voltage circuit module, a sampling circuit module, a comparison circuit module, a trigger voltage conversion circuit module, a level shaping circuit module, and a driving circuit module;

[0007] The input terminal of the reference voltage circuit module is connected to the positive and negative terminals of the power supply, respectively, and the output terminal is connected to the first input terminal of the sampling circuit module; the source of the N-channel transistor Q1 is connected to the negative terminal of the power supply.

[0008] The second input terminal of the sampling circuit module is connected to the drain of the N-channel transistor Q1 after being connected in series with diode D101, and is used to acquire the drain voltage of the N-channel transistor Q1; the third input terminal of the sampling circuit module is connected to the output terminal of the trigger voltage conversion module, and the output terminal is connected to the reference voltage input terminal of the three-terminal Zener diode IC101 in the comparison circuit module.

[0009] The comparison output terminal of the three-terminal Zener diode IC101 in the comparison circuit module is connected to the input terminal of the trigger voltage conversion circuit module; the trigger voltage conversion circuit module is used to output a bias current to the sampling circuit module to obtain the first critical trigger voltage value of the drain when the N-channel transistor Q1 is triggered from the on state to the off state, and the second critical trigger voltage value of the drain when the N-channel transistor Q1 is triggered from the off state to the on state.

[0010] The input terminal of the level shaping circuit module is connected to the comparison output terminal of the comparison circuit module, and the output terminal is connected to the input terminal of the drive circuit module.

[0011] The output terminal of the driving circuit module is connected to the gate of the N-channel transistor Q1 through a resistor, and is used to control the operating state of the N-channel transistor Q1 according to the drain voltage of the N-channel transistor Q1, the first critical trigger voltage value and the second critical trigger voltage value.

[0012] Furthermore, the reference voltage circuit module includes: resistor R101, resistor R109, resistor R111, capacitor C102, capacitor C103, and three-terminal Zener diode IC102.

[0013] The first end of the resistor R101 is connected to the positive terminal of the power supply, and the second end of the resistor R101 is connected to the output terminal VR1 of the reference voltage circuit module.

[0014] The output terminal VR1 is connected to the first terminal of the resistor R111, the first terminal of the capacitor C103, and the cathode of the three-terminal Zener diode IC102, respectively.

[0015] The reference voltage input terminal of the three-terminal Zener diode IC102 is connected to the second terminal of the resistor R111, the second terminal of the capacitor C103, the first terminal of the capacitor C102, and the first terminal of the resistor R109, respectively.

[0016] The anode of the three-terminal Zener diode IC102 is connected to the negative terminal of the power supply, the second terminal of the capacitor C102, and the second terminal of the resistor R109, respectively.

[0017] Furthermore, the sampling circuit module also includes: resistor R102 and resistor R104;

[0018] The first end of the resistor 102 is connected to the output terminal VR1 of the reference voltage circuit module, and the second end of the resistor 102 is connected to the output terminal of the trigger voltage conversion module, the reference voltage input terminal of the three-terminal regulator IC101, and the first end of the resistor R104.

[0019] The second end of the resistor R104 is connected to the anode of the diode D101, and the cathode of the diode D101 is connected to the drain of the N-channel transistor Q1.

[0020] Furthermore, the comparison circuit module also includes: resistor R105 and capacitor C104;

[0021] The first end of the resistor R105 is connected to the positive terminal of the power supply, and the second end of the resistor R105 is connected to the comparator output terminal of the three-terminal regulator IC101 and the input terminal of the trigger voltage conversion circuit module, respectively.

[0022] The first terminal of the capacitor 104 is connected to the reference voltage input terminal of the three-terminal Zener diode IC101, and the second terminal of the capacitor 104 is connected to the anode of the three-terminal Zener diode IC101 and the negative terminal of the power supply, respectively.

[0023] Furthermore, the trigger voltage conversion circuit module includes: a PNP transistor Q101, a capacitor C105, a resistor R110, a resistor R103, a resistor R106, and a diode D102.

[0024] The emitter of the PNP transistor Q101 is connected to the output terminal VR1 of the reference voltage circuit module, the first terminal of the capacitor C105, and the first terminal of the resistor R110, respectively.

[0025] The base of the PNP transistor Q101 is connected to the second terminal of the capacitor C105, the second terminal of the resistor R110, and the first terminal of the resistor R106, respectively.

[0026] The collector of the PNP transistor Q101 is connected to the first end of the resistor R103, and the second end of the resistor R103 is connected to the third input end of the sampling circuit module.

[0027] The second end of the resistor R106 is connected to the anode of the diode D102, and the cathode of the diode D102 is connected to the comparator output terminal of the three-terminal Zener diode IC101.

[0028] Furthermore, the level shaping circuit module includes: resistor R201, resistor R212, Zener diode ZD201, capacitor C201, diode D201, resistor R211, capacitor C202, PNP transistor Q201, resistor R202, resistor R205, resistor R203, and NPN transistor Q202;

[0029] The first end of the resistor R201 is connected to the comparator output terminal of the three-terminal Zener diode IC101, and the second end of the resistor R201 is connected to the first end of the resistor R212, the anode of the Zener diode ZD201, and the first end of the capacitor C201.

[0030] The second end of the resistor R212 is connected to the cathode of the diode D201, the first end of the resistor R211, the first end of the capacitor C202, the emitter of the PNP transistor Q201, and the first end of the resistor R203.

[0031] The cathode of the Zener diode ZD201 is connected to the second terminal of the capacitor C201, the anode of the diode D201, the second terminal of the resistor R211, the second terminal of the capacitor C202, and the base of the PNP transistor Q201, respectively.

[0032] The collector of the PNP transistor Q201 is connected to the first end of the resistor R202, the second end of the resistor R202 is connected to the first end of the resistor R205 and the base of the NPN transistor Q202, and the emitter of the NPN transistor Q202 is connected to the second end of the resistor R205 and the negative terminal of the power supply.

[0033] The second end of the resistor R203 is connected to the collector of the NPN transistor Q202 and the output terminal P2 of the level shaping circuit module, respectively.

[0034] Furthermore, the driving circuit module includes: resistors R204, R206, and R207; NPN transistor Q204; PNP transistor Q203; resistors R208, R210, and R209; NPN transistor Q206; PNP transistor Q205; Zener diode ZD202; and capacitor C203.

[0035] Among them, resistors R204, R206, R207, NPN transistor Q204, PNP transistor Q203, resistors R208, R210, R209, NPN transistor Q206, and PNP transistor Q205 constitute a bridge circuit;

[0036] The bridging circuit is connected to the positive terminal and the negative terminal of the power supply respectively. The input terminal of the bridging circuit is connected to the output terminal P2 of the level shaping circuit module, and the output terminal is connected to the anode of the Zener diode ZD202 and the first terminal of the capacitor C203 respectively.

[0037] The cathode of the Zener diode ZD202 is connected to the second terminal of the capacitor C203 and connected to the gate of the N-channel transistor Q1 through a resistor.

[0038] Furthermore, it also includes: a current change slope detection circuit module;

[0039] The input terminal of the current change slope detection circuit module is connected to the drain of the N-channel transistor Q1, and the output terminal is connected to the output terminal of the level shaping circuit module.

[0040] The current change slope detection circuit module is used to control the output of the level shaping circuit module to be set to a low level when the slope of the drain voltage change of the N-channel transistor Q1 is detected to be greater than a preset voltage change slope threshold.

[0041] Furthermore, the current change slope detection circuit module includes: capacitor C101, resistor R107, diode D104, resistor R108, and NPN transistor Q102.

[0042] The first terminal of the capacitor C101 is connected to the drain of the N-channel transistor Q1, and the second terminal of the capacitor C101 is connected to the first terminal of the resistor R107.

[0043] The second end of the resistor R107 is connected to the cathode of the diode D104, the first end of the resistor R108, and the base of the NPN transistor Q102, respectively.

[0044] The collector of the NPN transistor Q102 is connected to the output terminal of the level shaping circuit module, and the emitter of the NPN transistor Q102 is connected to the anode of the diode D104, the second terminal of the resistor R108, and the negative terminal of the power supply, respectively.

[0045] Furthermore, the synchronous rectification integrated circuit is specifically used to: when the N-channel transistor Q1 is in the on state, if the drain voltage of the N-channel transistor Q1 is less than the first critical trigger voltage value, control the N-channel transistor Q1 to remain in the on state; if the drain voltage of the N-channel transistor Q1 is greater than the first critical trigger voltage value, control the N-channel transistor Q1 to switch to the off state; when the N-channel transistor Q1 is in the off state, if the drain voltage of the N-channel transistor Q1 is greater than the second critical trigger voltage value, control the N-channel transistor Q1 to remain in the off state; if the drain voltage of the N-channel transistor Q1 is less than the second critical trigger voltage value, control the N-channel transistor Q1 to switch to the on state.

[0046] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0047] The synchronous rectification unit of this application embodiment includes: a synchronous rectification integrated circuit and an N-channel transistor Q1; the second input terminal of the sampling circuit module is connected to the drain of the N-channel transistor Q1 via a series diode D101, and is used to collect the drain voltage of the N-channel transistor Q1; the third input terminal of the sampling circuit module is connected to the output terminal of the trigger voltage conversion module, and the output terminal is connected to the reference voltage input terminal of the three-terminal Zener diode IC101 in the comparator circuit module; the comparator output terminal of the three-terminal Zener diode IC101 in the comparator circuit module is connected to the input terminal of the trigger voltage conversion circuit module; the output terminal of the drive circuit module is connected to the gate of the N-channel transistor Q1 through a resistor, and is used to control the operating state of the N-channel transistor Q1 according to the drain voltage, the first critical trigger voltage value, and the second critical trigger voltage value. The reverse blocking effect of the diode D101 prevents high voltage from entering the synchronous rectification integrated circuit circuit, which can be used in high-voltage DC power supplies and has high versatility. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0049] Figure 1 This is a schematic diagram of the secondary synchronous rectification of a flyback switching power supply disclosed in an embodiment of this application;

[0050] Figure 2 This is a circuit diagram of a synchronous rectification unit disclosed in an embodiment of this application;

[0051] Figure 3 This is a schematic diagram of a synchronous rectification integrated circuit disclosed in an embodiment of this application;

[0052] Figure 4 This is a circuit structure diagram of a synchronous rectification integrated circuit disclosed in an embodiment of this application;

[0053] Figure 5 This is a circuit structure diagram of another synchronous rectification integrated circuit disclosed in an embodiment of this application;

[0054] Figure 6 This is a simplified circuit diagram of a synchronous rectification integrated circuit disclosed in an embodiment of this application;

[0055] Figure 7 This is a simplified circuit diagram of another synchronous rectification integrated circuit disclosed in an embodiment of this application;

[0056] Figure 8 This is a simplified circuit diagram of another synchronous rectification integrated circuit disclosed in an embodiment of this application;

[0057] Figure 9 This is a waveform diagram of the operation of a synchronous rectification unit disclosed in an embodiment of this application;

[0058] Figure 10 This is a schematic diagram of a full-bridge synchronous rectifier circuit disclosed in an embodiment of this application. Detailed Implementation

[0059] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0060] In the description of the embodiments of this application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and 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. Therefore, they should not be construed as limitations on the embodiments of this application.

[0061] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0062] Existing integrated synchronous rectifier controllers have low withstand voltage values ​​at their pins, making them difficult to apply in high-voltage DC power supplies. Furthermore, these controllers are typically used in dedicated switching power supply topologies corresponding to their specific models, hindering their versatility and making them difficult to combine in different topologies. In switching power supplies with output voltages greater than 60V, existing technologies struggle to achieve synchronous rectification, hindering further efficiency improvements in related applications and failing to meet the ever-increasing energy-saving and carbon-reduction requirements of today's economy. Simultaneously, the poor versatility of existing "synchronous rectification control integrated circuits" hinders cost reduction. With socio-economic development, the demand for high efficiency, energy saving, reduced consumption, and carbon reduction is becoming increasingly urgent. In summary, existing technologies cannot meet the demands of socio-economic development in some switching power supply applications, necessitating a technology that provides synchronous rectification control for high-output-voltage switching power supplies. This technology also needs to meet the socio-economic development requirements of continuously decreasing switching power supply costs and large-scale deployment. Therefore, this application provides a synchronous rectification unit that can be applied in high-voltage DC power supplies and has high versatility. Figure 2 as well as Figure 3 As shown, it can be understood that the transistors shown in the figures of this application embodiment can be replaced by field-effect transistors. The transistors in the figures of this application embodiment can be described using field-effect transistors, and will not be repeated hereafter. The specific embodiments of this application are as follows:

[0063] Figure 2In this circuit, Q1 is an N-channel transistor, which can be an N-channel field-effect transistor made of various semiconductor materials; V1 is the positive terminal of the power supply (auxiliary power supply positive terminal); S1 is the negative terminal of the power supply (auxiliary power supply negative terminal) or the source (S) of Q1, and S1 is the zero potential reference point of the integrated circuit; G1 is the positive output terminal of the "synchronous rectification control circuit module 10", which can also be understood as the gate of the N-channel transistor Q1; D1 is the drain (D) of the N-channel transistor Q1; R* is a resistor, and the * sign represents any numerical number. The synchronous rectification unit of this application embodiment includes: a synchronous rectification integrated circuit (synchronous rectification control integrated circuit) 10 and an N-channel transistor Q1.

[0064] The synchronous rectification integrated circuit 10 includes: a reference voltage circuit module 101, a sampling circuit module 102, a comparator circuit module 103, a trigger voltage conversion circuit module 104, a current change slope detection circuit module 105, a level shaping circuit module 106, and a drive circuit module 107. The input terminal of the reference voltage circuit module 101 is connected to the positive power supply V1 and the negative power supply S1, respectively, and its output terminal is connected to the first input terminal of the sampling circuit module 102; the source of the N-channel transistor Q1 is connected to the negative power supply S1. The second input terminal of the sampling circuit module 102 is connected to the drain of the N-channel transistor Q1 after series connection with diode D101, for acquiring the drain voltage of the N-channel transistor Q1. The third input terminal of the sampling circuit module 102 is connected to the output terminal of the trigger voltage conversion module 104, and its output terminal is connected to the reference voltage input terminal of the three-terminal Zener diode IC101 in the comparator circuit module 103. In the comparator circuit module 103, the comparator output terminal of the three-terminal Zener diode IC 101 is connected to the input terminal of the trigger voltage conversion circuit module 104. The trigger voltage conversion circuit module 104 is used to output a bias current to the sampling circuit module 102 to obtain the first critical trigger voltage value VD1_1 of the drain of the N-channel transistor Q1 when it is triggered from the on state to the off state, and the second critical trigger voltage value VD1_0 of the drain of the N-channel transistor Q1 when it is triggered from the off state to the on state. The input terminal of the level shaping circuit module 106 is connected to the comparator output terminal of the comparator circuit module 103, and the output terminal is connected to the input terminal of the drive circuit module 107. The output terminal of the drive circuit module 107 is connected to the gate of the N-channel transistor Q1 through a resistor, and is used to control the operating state of the N-channel transistor Q1 according to the drain voltage, the first critical trigger voltage value, and the second critical trigger voltage value.

[0065] Specifically, the working principle of the synchronous rectification unit in this embodiment is as follows:

[0066] ① Assume the initial state of the N-channel field-effect transistor Q1: the voltage difference VG1 between its gate (G) and source (S) is low, and Q1 is in the off state. At this time, if current flows from the source (S) of Q1 through the parasitic body diode (or an externally connected diode in the same direction) and parasitic capacitance to the drain (D) of Q1, the drain (D) voltage VD1 of Q1 is a negative voltage value whose absolute value is less than the forward voltage drop of the diode (0.7V). The synchronous rectification control integrated circuit 10 can determine that the current flowing through Q1 in the main circuit is in the negative direction (flowing from the source (S) to the drain (D)) of Q1 by detecting the drain (D) voltage VD1 of Q1, and switch the output drive level state within a few hundred nanoseconds, so that the voltage difference VG1 between the gate (G) and source (S) of Q1 changes from low to high. At this point, Q1 transitions from the off state to the on state, switching the current in the main circuit from flowing through the parasitic diode of Q1 to flowing through the semiconductor channel of Q1. Because Q1 transitions from the off state to the on state, the current flows through the semiconductor channel of Q1, which has a much lower impedance, thus avoiding significant losses caused by large current in the diode with a high on-state voltage drop. By selecting an N-channel MOSFET Q1 with a smaller on-resistance (Rdson), power consumption can be reduced to a fraction of the diode losses, reaching a level not exceeding one-tenth. The larger the current flowing through the synchronous rectification unit, the more significant the energy-saving and carbon-reduction effects.

[0067] ② Assume the initial state of the N-channel field-effect transistor Q1: its gate (G) and source (S) voltage difference VG1 is high, and Q1 is in the on-state. At this time, since the drain (D) voltage VD1 of Q1 is equal to the product of the on-resistance (Rdson) of the Q1 semiconductor channel and the current (I) flowing through the Q1 semiconductor channel, the synchronous rectification control integrated circuit 10 can determine the magnitude of the current flowing through the Q1 semiconductor channel by detecting the drain (D) voltage value VD1 of Q1. If the current flowing through the semiconductor channel of Q1 begins to decrease, when the current decreases to close to 0A, the synchronous rectification control integrated circuit 10 also detects that the drain (D) voltage value VD1 of Q1 is close to 0V. At this time, the synchronous rectification control integrated circuit 10 will switch the output drive level state within a few hundred nanoseconds, so that the gate (G) and source (S) voltage difference VG1 of Q1 changes from high level to low level. This is to prevent Q1 from remaining on after the AC voltage commutation, which would cause the circuit to lose its rectification function and result in a short circuit.

[0068] As can be seen, the synchronous rectification unit of this application embodiment includes: a synchronous rectification integrated circuit and an N-channel transistor Q1; the second input terminal of the sampling circuit module is connected to the drain of the N-channel transistor Q1 after being connected in series with a diode D101, and is used to collect the drain voltage of the N-channel transistor Q1; the third input terminal of the sampling circuit module is connected to the output terminal of the trigger voltage conversion module, and the output terminal is connected to the reference voltage input terminal of the three-terminal Zener diode IC101 in the comparison circuit module; the comparison output terminal of the three-terminal Zener diode IC101 in the comparison circuit module is connected to the input terminal of the trigger voltage conversion circuit module; the output terminal of the drive circuit module is connected to the gate of the N-channel transistor Q1 through a resistor, and is used to control the operating state of the N-channel transistor Q1 according to the drain voltage of the N-channel transistor Q1, the first critical trigger voltage value, and the second critical trigger voltage value. The reverse blocking effect of the diode D101 prevents high voltage from entering the synchronous rectification integrated circuit circuit, which can be used in high-voltage DC power supplies and has high versatility.

[0069] Furthermore, in this embodiment, a three-terminal Zener diode IC101 is used as the core logic device of the synchronous rectification control integrated circuit 10. The input / output pulse response time of a general-purpose three-terminal Zener diode (e.g., TL431, TL432 series, etc.) is less than 100 ns, which is a fraction of the input / output pulse response time of a similarly priced general-purpose comparator. Therefore, using this synchronous rectification control integrated circuit 10 can achieve a smaller circuit logic delay than using existing comparators with similar costs, making the synchronous rectification drive pulse level conversion time of the switching power supply more accurate, thereby increasing power efficiency. On the other hand, the cost of using the synchronous rectification control integrated circuit 10 is several times lower than that of using a dedicated synchronous rectification control integrated circuit with similar input / output pulse response time, not only achieving synchronous rectification more accurately but also significantly reducing costs. Meanwhile, in this embodiment, a diode D101 is connected in series between the output terminal of the sampling circuit module 102 in the synchronous rectification control integrated circuit 10 and the drain (D) of the N-channel field-effect transistor Q1. By employing this synchronous rectification control integrated circuit 10, only one component, the diode D101 with a high reverse withstand voltage rating, needs to be selected. This allows the synchronous rectification control integrated circuit 10 to be applied to high-output voltage rectified power supplies, a field where existing integrated synchronous rectification controllers are difficult to apply. Furthermore, the diode D101 is a low-current, low-cost device. The synchronous rectification unit in this embodiment can be combined and applied to different topologies, such as... Figure 10As shown, S1 is the source (S) of the N-channel field-effect transistor Q1 in "Synchronous Rectification Unit 01"; S2 is the source (S) of the N-channel field-effect transistor Q1 in "Synchronous Rectification Unit 02"; S3 is the source (S) of the N-channel field-effect transistor Q1 in "Synchronous Rectification Unit 03"; S4 is the source (S) of the N-channel field-effect transistor Q1 in "Synchronous Rectification Unit 04"; D1 is the drain (D) of the N-channel field-effect transistor Q1 in "Synchronous Rectification Unit 01"; D2 is the drain (D) of the N-channel field-effect transistor Q1 in "Synchronous Rectification Unit 02"; D3 is the drain (D) of the N-channel field-effect transistor Q1 in "Synchronous Rectification Unit 03". D1 is the drain (D) of N-channel field-effect transistor Q1 in synchronous rectification unit 04; D4 is the drain (D) of N-channel field-effect transistor Q1 in synchronous rectification unit 04; V1 is the positive terminal of the auxiliary power input of synchronous rectification unit 01; V2 is the positive terminal of the auxiliary power input of synchronous rectification unit 02; V3 is the positive terminal of the auxiliary power input of synchronous rectification units 03 and 04; AC_L is the AC input live wire (L); AC_N is the AC input neutral wire (N); VO+ is the positive terminal of the DC output voltage of the full-bridge synchronous rectification circuit system; VO- is the negative terminal of the DC output voltage of the full-bridge synchronous rectification circuit system; C1 is a capacitor. It can be seen that four identical synchronous rectification units using the embodiments of this application are used in the bridge rectifier circuit, while two identical synchronous rectification units using the embodiments of this application can be used in the push-pull rectifier circuit. This provides greater versatility and can further promote widespread application and reduce costs.

[0070] Furthermore, the reference voltage circuit module 101, sampling circuit module 102, comparison circuit module 103, and trigger voltage value conversion circuit module 104 in this application embodiment are as follows: Figure 4As shown. The reference voltage circuit module 101 includes: resistors R101, R109, and R111; capacitors C102 and C103; and a three-terminal Zener diode IC102. The reference voltage circuit 101 is composed of IC102 as the core component. The first terminal of resistor R101 is connected to the positive terminal V1 of the power supply, and the second terminal of resistor R101 is connected to the output terminal VR1 of the reference voltage circuit module 101. The output terminal VR1 is connected to the first terminal of resistor R111, the first terminal of capacitor C103, and the cathode (K) of the three-terminal Zener diode IC102. The reference voltage input terminal (R) of the three-terminal Zener diode IC102 is connected to the second terminal of resistor R111, the second terminal of capacitor C103, the first terminal of capacitor C102, and the first terminal of resistor R109. The anode (A) of the three-terminal Zener diode IC102 is connected to the negative terminal S1 of the power supply, the second terminal of capacitor C102, and the second terminal of resistor R109. In the reference voltage circuit module 101, circuit node S1 is taken as the reference 0 potential, and the cathode (K) of the three-terminal Zener diode IC102 is the output terminal of the reference voltage VR1. The reference voltage VR1 is calculated as shown in Formula 1:

[0071] VR1=V_IC102*(R109+R111) / R109 Formula 1

[0072] VR1 represents the voltage difference between the cathode (D) of the three-terminal Zener diode IC102 and the reference 0 potential circuit node S1; V_IC102 represents the internal reference voltage of the three-terminal Zener diode IC102. Capacitors C102 and C103 are used for voltage smoothing, filtering, and interference suppression. Resistor R101 supplies power to IC102.

[0073] The sampling circuit module 102 further includes resistors R102 and R104. The first end of resistor R102 is connected to the output terminal VR1 of the reference voltage circuit module 101. The second end of resistor R102 is connected to the output terminal of the trigger voltage conversion module, the reference voltage input terminal (R) of the three-terminal regulator IC101, and the first end of resistor R104. The second end of resistor R104 is connected to the anode of diode D101, and the cathode of diode D101 is connected to the drain of N-channel transistor Q1. The comparator circuit module 103 further includes resistor R105 and capacitor C104. The first end of resistor R105 is connected to the positive terminal of the power supply. The second end of resistor R105 is connected to the comparator output terminal of the three-terminal regulator IC101 and the input terminal of the trigger voltage conversion circuit module. The first end of capacitor C104 is connected to the reference voltage input terminal (R) of the three-terminal regulator IC101, and the second end of capacitor C104 is connected to the anode (A) of the three-terminal regulator IC101 and the negative terminal S1 of the power supply. The trigger voltage conversion circuit module 104 includes: a PNP transistor Q101, a capacitor C105, a resistor R110, a resistor R103, a resistor R106, and a diode D102; the emitter of the PNP transistor Q101 is connected to the output terminal VR1 of the reference voltage circuit module, the first terminal of the capacitor C105, and the first terminal of the resistor R110, respectively; the base of the PNP transistor Q101 is connected to the second terminal of the capacitor C105, the second terminal of the resistor R110, and... The first end of resistor R106 is connected to the first end of resistor R103; the collector of PNP transistor Q101 is connected to the first end of resistor R103, the second end of resistor R103 is connected to the third input terminal of the sampling circuit module; the second end of resistor R106 is connected to the anode of diode D102, and the cathode of diode D102 is connected to the comparator output terminal P1 of Zener diode IC101. It can be understood that the comparator output terminal P1 of Zener diode IC101 is the cathode (K) of Zener diode IC101.

[0074] The working principle of the reference voltage circuit module 101, sampling circuit module 102, comparison circuit module 103, and trigger voltage value conversion circuit module 104 is as follows:

[0075] (1) Assume the initial state of the "Synchronous Rectification Control Integrated Circuit 10" of the present invention: with circuit node S1 as the reference potential 0, the voltage VR at the reference voltage input terminal (R) of the three-terminal Zener diode IC101 is greater than the internal reference voltage V_IC101 of the three-terminal Zener diode IC101. At this time, the cathode (K) voltage VP1 of the three-terminal Zener diode IC101 is at a low level (Q1 is in the off state at this time). When VP1 is at a low level, a large current flows from the positive terminal VR1 of the "reference voltage circuit" output terminal, through resistors R110 and R106, the positive terminal of diode D102, the negative terminal of diode D102, the cathode (K) of the three-terminal Zener diode IC101, the anode (A) of the three-terminal Zener diode IC101, and back to the negative terminal of the "reference voltage circuit" output terminal (reference potential circuit node S1).

[0076] Choose appropriate resistors R110 and R106 so that the voltage difference between the emitter (E) and base (B) of the PNP transistor Q101 (i.e., the voltage across resistor R110) is equal to its PN junction turn-on voltage (or the voltage difference between the source (S) and gate (G) of the P-channel MOSFET Q101 is greater than its turn-on threshold voltage). At this point, Q101 turns on. Because Q101 is on, current flows from the positive terminal VR1 of the "reference voltage circuit" output, through the emitter (E) of the PNP transistor Q101, the collector (C) of the PNP transistor Q101, resistor R103, and into resistor R104 and the reference voltage terminal (R) of the three-terminal Zener diode IC101.

[0077] At this time, another current flows from the positive terminal VR1 of the "reference voltage circuit" output, through resistor R102, and simultaneously into resistors R104 and the reference voltage terminal (R) of the three-terminal regulator IC101. Since the input current to the reference terminal (R) of the three-terminal regulator IC101 is only a few microamps, it is negligible compared to the current flowing through appropriately selected resistors R102, R103, and R104. The current converging into resistor R104 then flows through the anode and cathode of diode D101, and into the drain (D) of the N-channel MOSFET Q1. By selecting appropriate component parameters, the forward voltage drop between the emitter (E) and collector (C) of the PNP transistor Q101 (or the source (S) and drain (D) of the P-channel MOSFET Q101) can also be ignored.

[0078] At this point, the reference voltage (R) VR of the three-terminal Zener diode IC101 is calculated as shown in Formula 4:

[0079]

[0080] In formula 4, let

[0081] K1=(R104*R103+R102*R104) / (R102*R103+R103*R104+R102*R104)

[0082] Formula 4 can then be simplified to Formula 5:

[0083] VR=VR1*K1+V_D101*(1-K1)+VD1*(1-K1) Formula 5

[0084] When VR = V_IC101, the three-terminal Zener diode IC101 is at the critical moment of being triggered to conduct.

[0085] When VR > V_IC101, the three-terminal Zener diode IC101 is triggered to conduct, and the cathode (K) voltage VP1 of IC101 becomes low. At this time, a current greater than 100mA can pass between its cathode (K) and anode (A).

[0086] When VR < V_IC101, the three-terminal Zener diode IC101 is not triggered to conduct, and the cathode (K) voltage VP1 of IC101 becomes high. At this time, there is only a static operating current of less than 1mA between its cathode (K) and anode (A).

[0087] When the initial state is VR > V_IC101, IC101 is in the on state. Assuming the voltage VR gradually decreases and reaches VR = V_IC101 (the critical point where IC101 transitions from the on state to the off state), the specific value of the drain (D) voltage VD1 of the N-channel field-effect transistor Q1 is defined as VD1_0. Formula 6 can be derived from Formula 5:

[0088] VD1_0=[(V_IC101-VR1*K1) / (1-K1)]-V_D101 Formula 6

[0089] From Formula 6, we can conclude that when the three parameters VR1, K1, and V_D101 on the right side of the formula are selected as fixed values, the critical trigger voltage value VD1_0 of the drain (D) of Q1 that triggers IC101 from the on state to the off state (at this time, Q1 is triggered from the off state to the on state) is also uniquely determined.

[0090] Formula 7 can be derived from Formulas 5 and 6:

[0091] When the initial state is VR > V_IC101, the following formula 7 holds:

[0092] When VD1 changes from the initial state described above to VD1 < VD1_0, then VR changes to VR < V_IC101, and VP1 becomes high. Formula 7

[0093] The symbols in Formula 4-7 have the following meanings: VR: Voltage difference between the reference terminal (R) of the three-terminal Zener diode IC101 and the reference 0 potential circuit node S1. V_IC101: Internal reference voltage of the three-terminal Zener diode IC101. V_D101: Forward conduction voltage of diode D101. VD1_0: Critical trigger voltage at circuit node D1 of the drain (D) of Q1, which triggers Q1 from the off state to the on state. Other symbols are the same as in Formula 1 above.

[0094] In high-voltage synchronous rectification circuit applications, such as some secondary rectifier circuits in switching power supplies used for LED series light strips, such as... Figure 1 As shown, in the off state of the N-channel field-effect transistor Q1, the voltage difference VD1 between its drain (D) and source (S) (reference 0 potential) can reach over 200V. Existing synchronous rectification control ICs, due to their voltage rating being below 200V, cannot be used in this type of circuit.

[0095] Based on existing technology, such high-voltage rectifier circuits can only use diode rectification, resulting in huge losses in switching power supplies with large output currents, which cannot meet the current trend of accelerating energy conservation and carbon reduction.

[0096] Therefore, in the sampling circuit module 102 of this application embodiment, a diode D101 is innovatively added. When the N-channel field-effect transistor Q1 is in the off state, and the voltage difference VD1 between its drain (D) and source (S) (reference 0 potential) is greater than VR1, the diode D101 is reverse biased. Due to the reverse blocking effect of the diode D101, high voltage cannot enter the control circuit of this invention. In the synchronous rectification control integrated circuit 10, the highest voltage value VR on the reference terminal (R) of the three-terminal Zener diode IC101 is less than VR1, and other components in the circuit are not affected by the high voltage of the external circuit. Therefore, by simply selecting the reverse withstand voltage specification of the diode D101 to exceed the peak voltage VD1 of the synchronous rectification circuit, the circuit of this application embodiment can be reliably applied in any high-voltage synchronous rectification field. This invention further meets the urgent social development needs of energy conservation and carbon reduction at a lower cost. Therefore, this application embodiment can be widely used in various power supplies and synchronous rectification circuits, and has great social and economic value.

[0097] From the above formula 4-7, we can conclude that:

[0098] After selecting suitable component parameters in the circuit of this application embodiment, when the initial state of the synchronous rectification control integrated circuit 10 of this application embodiment is VR>V_IC101, the critical trigger voltage value VD1_0 of the drain (D) voltage VD1 of the N-channel field effect transistor Q1 is determined by formula 4-6.

[0099] As can be seen from Formula 7, after selecting the appropriate component parameters in the circuit of the present invention, the output level VP1 state of the comparator circuit module 103 in the synchronous rectification control integrated circuit 10 of this application embodiment is determined by the VD1 voltage value.

[0100] For example, when selecting component parameters as follows:

[0101] V_IC102=2.5V, V_IC101=2.5V, V_D101=0.7V, R109=10KΩ, R111=10KΩ, R102=10KΩ, R104=7.2KΩ, R103=180KΩ.

[0102] The result can be obtained by calculating according to formula 1-6:

[0103] VR1 = 5V, VD1_0 = -0.1V.

[0104] Based on the calculation results and the above principle analysis, we can conclude that:

[0105] When the N-channel field-effect transistor Q1 is initially in the off state, if the drain (D) voltage VD1 of the N-channel field-effect transistor Q1 is greater than -0.1V, the output voltage VP1 of the comparator circuit module 103 in the synchronous rectification control integrated circuit 10 of the present invention will maintain a low initial level, and the output voltage VG1 of the drive circuit module 107 will also maintain a low initial level. At this time, Q1 remains in the off state.

[0106] When the drain (D) voltage VD1 of the N-channel field-effect transistor Q1 is less than -0.1V, the output voltage VP1 of the comparator circuit module 103 of the synchronous rectification control integrated circuit 10 of the present invention will flip from a low initial state to a high level, and the output voltage VG1 of the drive circuit module 107 will also flip from a low initial state to a high level. At this time, Q1 will also change from the cutoff state to the conduction state.

[0107] When the voltage value of VD1 changes from the initial state VD1>VD1_0 to VD1<VD1_0, the three-terminal regulator IC101 will change from the on state to the off state, and change from the initial state (the cathode (K) voltage VP1 of the three-terminal regulator IC101 is low) to a new state where the cathode (K) voltage VP1 of the three-terminal regulator IC101 is high.

[0108] (2) Based on the analysis in the previous section, when the actual voltage VD1 at the detection point D1 is less than VD1_0, it is determined that current flows through the parasitic body diode (or the parallel diode in the same direction) and parasitic capacitance of the N-channel field-effect transistor Q1. At this time, Q1 is triggered to conduct, allowing current to flow from the source (S) of Q1 through the semiconductor channel to the drain (D). This avoids current flowing through the parasitic body diode or the parallel diode in the same direction of Q1, as the forward conduction voltage of the diode is relatively high, and a large conduction loss will occur when the current is large. When VP1 is high, the Zener diode IC101 has only a very small quiescent operating current, which flows from the positive terminal VR1 of the reference voltage circuit 101, through resistors R110 and R106, the positive terminal of diode D102, the negative terminal of diode D102, the cathode (K) of the Zener diode IC101, the anode (A) of the Zener diode IC101, and back to the negative terminal of the reference voltage circuit 101 (refer to node S1 of the 0 potential circuit).

[0109] By selecting appropriate resistor parameters R110 and R106, the voltage difference between the emitter (E) and base (B) of the PNP transistor Q101 (i.e., the voltage across resistor R110) is less than its PN junction turn-on voltage (or the voltage difference between the source (S) and gate (G) of the P-channel MOSFET Q101 is less than the absolute value of its turn-on threshold voltage). At this point, Q101 is cut off. Because Q101 is cut off, the current path from the positive output terminal VR1 of the reference voltage circuit 101, through the emitter (E) of Q101, the collector (C) of Q101, and resistor R103, to resistor R104 and the reference voltage terminal (R) of the Zener diode IC101 is blocked. Since no current flows through resistor R103, only one current flows from the positive output terminal VR1 of the reference voltage circuit 101, through resistor R102, and simultaneously into R104 and the reference voltage terminal (R) of the Zener diode IC101. Since the input current to the reference terminal (R) of the three-terminal Zener diode IC101 is only a few microamps, it can be ignored compared with the current flowing through resistors R102 and R104 with appropriate parameters. The current that converges to resistor R104 then flows through the anode and cathode of diode D101 and into the drain (D) of N-channel MOSFET Q1 (circuit node D1).

[0110] At this point, the reference voltage (R) VR of the three-terminal Zener diode IC101 is calculated as shown in Formula 8:

[0111]

[0112] In formula 4, let K2 = R104 / (R102 + R104), then formula 8 can be simplified to formula 9:

[0113] VR = VR1*K2 + V_D101*(1-K2) + VD1*(1-K2) Formula 9

[0114] When the initial state is VR < V_IC101, IC101 is in the off state. Assuming the voltage VR gradually increases and reaches VR = V_IC101 (the critical point where IC101 changes from off to on or from on to off), the drain (D) voltage VD1 of the N-channel field-effect transistor Q1 has a specific value of VD1_1 at this time. Formula 10 can be derived from Formula 9:

[0115] VD1_1=[(V_IC101-VR1*K2) / (1-K2)]-V_D101 Formula 10

[0116] From Equation 10, we can conclude that when the three parameters VR1, K2, and V_D101 on the right side of the equation are selected as fixed values, the critical trigger voltage value VD1_1 of the drain (D) of Q1 when IC101 is triggered from the cutoff state to the on state (at this time, Q1 is triggered from the on state to the cutoff state) is also uniquely determined.

[0117] Formula 11 can be derived from Formulas 9 and 10:

[0118] When the initial state is VR < V_IC101, the following formula 11 holds:

[0119] When VD1 changes from the initial state to VD1 > VD1_1, VR changes to VR > V_IC101, and VP1 becomes low. (Formula 11)

[0120] The meanings of the symbols in Formula 8-11:

[0121] Same as formulas 1-7 above.

[0122] From the above formula 8-11, we can conclude that:

[0123] After selecting suitable component parameters in the circuit of the present invention, when the initial state of the synchronous rectification control integrated circuit 10 of the present invention is VR < V_IC101, the critical trigger voltage value VD1_1 of the drain (D) voltage VD1 of the N-channel field effect transistor Q1 is determined by formula 8-10.

[0124] As can be seen from Formula 11, after selecting the appropriate component parameters in the circuit of the present invention, the output level VP1 state of the comparator circuit module 103 of the synchronous rectification control integrated circuit 10 of the present invention is determined by the VD1 voltage value.

[0125] For example, when selecting component parameters as follows:

[0126] V_IC102=2.5V, V_IC101=2.5V, V_D101=0.7V, R109=10KΩ, R111=10KΩ, R102=10KΩ, R104=7.2KΩ, R103=180KΩ.

[0127] All of the above parameters are exactly the same as the values ​​selected in Section (2).

[0128] The result can be obtained by calculating according to formula 8-11:

[0129] VR1 = 5V, VD1_1 = 0V.

[0130] Based on the calculation results and the above principle analysis, we can conclude that:

[0131] When the N-channel field-effect transistor Q1 is initially in the on state, if the drain (D) voltage VD1 of the N-channel field-effect transistor Q1 is less than 0V, the output voltage VP1 of the comparator circuit module 103 in the synchronous rectification control integrated circuit 10 of the present invention will maintain a high initial level, and the output voltage VG1 of the drive circuit module 107 will also maintain a high initial level. At this time, Q1 remains in the on state.

[0132] When the drain (D) voltage VD1 of the N-channel field-effect transistor Q1 is greater than 0V, the output voltage VP1 of the comparator circuit module 103 of the synchronous rectification control integrated circuit 10 of the present invention will flip from the initial high level to the low level, and the output voltage VG1 of the drive circuit module 107 will also flip from the initial high level to the low level. At this time, Q1 will also change from the on state to the off state.

[0133] When the N-channel field-effect transistor Q1 is in the on state, its drain (D) voltage VD1 = I*Rdson. Therefore, VD1 is proportional to the magnitude of the channel current (I) flowing through the drain (D) and source (S) of Q1 and the on-resistance (Rdson).

[0134] To improve the efficiency of the synchronous rectification unit, the on-resistance (Rdson) of Q1 is generally chosen to be very small. To ensure that the synchronous rectification control IC 10 output level VG1 only flips to a low level when the channel current flowing through the drain (D) and source (S) of Q1 is close to 0A, thus turning off Q1 and minimizing circuit losses, the critical trigger voltage VD1_1 is chosen to be 0V or close to 0V to maximize circuit efficiency.

[0135] Furthermore, such as Figure 5As shown, the level shaping circuit module 106 in this application includes: resistor R201, resistor R212, Zener diode ZD201, capacitor C201, diode D201, resistor R211, capacitor C202, PNP transistor Q201, resistor R202, resistor R205, resistor R203, and NPN transistor Q202; the first terminal of resistor R201 is connected to the comparator output terminal of the three-terminal Zener diode IC101, and the second terminal of resistor R201 is connected to the first terminal of resistor R212, the anode of Zener diode ZD201, and the first terminal of capacitor C201; the second terminal of resistor R212 is connected to the cathode of diode D201, the first terminal of resistor R211, the first terminal of capacitor C202, and the PNP transistor Q202. The emitter of Q201 is connected to the first terminal of resistor R203; the cathode of Zener diode ZD201 is connected to the second terminal of capacitor C201, the anode of diode D201, the second terminal of resistor R211, the second terminal of capacitor C202, and the base of PNP transistor Q201; the collector of PNP transistor Q201 is connected to the first terminal of resistor R202; the second terminal of resistor R202 is connected to the first terminal of resistor R205 and the base of NPN transistor Q202; the emitter of NPN transistor Q202 is connected to the second terminal of resistor R205 and the negative terminal of the power supply; the second terminal of resistor R203 is connected to the collector of NPN transistor Q202 and the output terminal P2 of the level shaping circuit module.

[0136] The driving circuit module 107 in this application includes: resistors R204, R206, R207, NPN transistor Q204, PNP transistor Q203, resistors R208, R210, R209, NPN transistor Q206, PNP transistor Q205, Zener diode ZD202, and capacitor C203; wherein, resistors R204, R206, R207, NPN transistor Q204, PNP transistor Q203, and R208 are used in driving circuits. 08. Resistors R210 and R209, NPN transistor Q206, and PNP transistor Q205 form a bridge circuit. The bridge circuit is connected to the positive and negative terminals of the power supply, respectively. The input terminal of the bridge circuit is connected to the output terminal P2 of the level shaping circuit module, and the output terminal is connected to the anode of Zener diode ZD202 and the first terminal of capacitor C203, respectively. The cathode of Zener diode ZD202 is connected to the second terminal of capacitor C203 and the first terminal of resistor R1, respectively. The second terminal of resistor R1 is connected to the gate of N-channel transistor Q1.

[0137] Specifically, the synchronous rectification integrated circuit is used to control N-channel transistor Q1 to remain in the on state if the drain voltage of N-channel transistor Q1 is less than the first critical trigger voltage value, and to switch N-channel transistor Q1 to the off state if the drain voltage of N-channel transistor Q1 is greater than the first critical trigger voltage value; and to control N-channel transistor Q1 to switch to the off state if the drain voltage of N-channel transistor Q1 is greater than the second critical trigger voltage value when N-channel transistor Q1 is in the off state.

[0138] The working principles of the level shaping circuit module 106 and the driving circuit module 107 are as follows:

[0139] (1) When the three-terminal Zener IC101 is turned on, its cathode (K) voltage VP1 is low.

[0140] Choose appropriate resistors R201, R211, and R212 so that the voltage across resistor R211 is equal to the forward conduction voltage of the PN junction between the emitter (E) and base (B) of the PNP transistor Q201 (or the absolute value of the voltage across resistor R211 is greater than the absolute value of the turn-on threshold voltage between the source (S) and gate (G) of the P-channel MOSFET Q201). At this point, current flows from the positive terminal V1 of the first auxiliary power supply, through resistor R211, and through the emitter (E) and base (B) of the PNP transistor Q201 (or through the source (S) and gate (G) of the P-channel MOSFET Q201), then into the cathode of the Zener diode ZD201 and one end of capacitor C201, flowing out from the anode of the Zener diode ZD201 and the other end of capacitor C201, and then through resistor R201 to circuit node P1. At this point, Q201 is turned on. With Q201 conducting, current flows from the positive terminal V1 of the first auxiliary power supply, through resistor R202, the base (B) of the NPN transistor Q202 (or the gate (G) of the N-channel MOSFET Q202), then one path flows through resistor R205 into circuit node S1 (reference 0 potential), and the other path flows through the emitter (E) of the NPN transistor Q202 (or the source (S) of the N-channel MOSFET) into circuit node S1 (reference 0 potential). At this time, Q202 is conducting. Because Q202 is conducting, the collector (C) voltage (or the drain (D) voltage) VP2 of the NPN transistor Q202 is low.

[0141] When VP2 is low, the charge stored in the parasitic capacitance between the gate (G) and source (S) of the N-channel MOSFET Q1 (refer to the 0 potential circuit node S1) is discharged through the following current path: one path goes through capacitor C203, and the other path goes through the anode and cathode of Zener diode ZD202, and then flows into the emitter (E) of PNP transistor Q205 (or the source (S) of P-channel MOSFET Q205). Then, one path flows through the collector (C) of the PNP transistor Q205 (or the drain (D) of the P-channel MOSFET Q205) into circuit node S1 (reference 0 potential), and the other path flows through the base (B) of the PNP transistor Q205 (or the gate (G) of the P-channel MOSFET Q205) and then splits again, one path flowing through resistor R210 into circuit node S1 (reference 0 potential), and the other path flowing through resistor R208 and the emitter (E) of the PNP transistor Q203 (or the source (S) of the P-channel MOSFET Q203) and then splits again, one path flowing through the collector (C) of the PNP transistor Q203 (or... The drain (D) of the P-channel MOSFET Q203 flows into circuit node S1 (reference 0 potential). Another path flows through the base (B) of the PNP transistor Q203 (or the gate (G) of the P-channel MOSFET Q203) and then splits, with one path flowing through resistor R206 into circuit node S1 (reference 0 potential), and the other path flowing through resistor R204, the collector (C) of the NPN transistor Q202 (or the drain (D) of the N-channel MOSFET Q202), and the emitter (E) of the NPN transistor Q202 (or the source (S) of the N-channel MOSFET Q202) into circuit node S1 (reference 0 potential). The voltage across the parasitic capacitance between the gate (G) and source (S) of the N-channel MOSFET Q1 (i.e., reference 0 potential circuit node S1) gradually decreases during this discharge process. When this voltage falls below the gate (G) threshold voltage of Q1, Q1 is turned off. At this time, VG1 is at a low level.

[0142] The function of Zener diode ZD202 and capacitor C203 is that, due to the existence of the PN junction voltage between the emitter (E) and collector (C) of PNP transistors Q203 and Q205 (or the turn-on threshold voltage between the source (S) and gate (G) of P-channel MOSFET Q203), if the voltage of the parasitic capacitance between the gate (G) and source (S) of Q1 is discharged only through the natural current path, when it approaches the voltage of two series PN junctions (approximately 0.6V to 1.4V) (or two series threshold voltages (approximately 4V to 7V)), the discharge current will become 0A, making Q1 unable to reliably turn off.

[0143] To ensure reliable cutoff of the N-channel MOSFET Q1, capacitor C203, which stored charge during the previous charging cycle of Q1's gate (G), has a negative voltage at one end connected to G1 and a positive voltage at the other end connected to the cathode of Zener diode ZD202. Therefore, during the charge discharge cycle of Q1's gate (G), this capacitor can reverse charge the parasitic capacitance between Q1's gate (G) and source (S), making the parasitic capacitance between Q1's gate (G) and source (S) a reverse voltage when cutoff, thus achieving reliable cutoff.

[0144] (2) Assume that the three-terminal Zener diode IC101 is turned off and its cathode (K) voltage VP1 is high.

[0145] At this time, only a very small static operating current of the three-terminal Zener diode IC101 flows from the positive terminal V1 of the first auxiliary power supply. One path passes through resistor R211, the cathode of Zener diode ZD201, and one end of capacitor C201, and flows out from the anode of Zener diode ZD201 and the other end of capacitor C201, into one end of resistor R201; the other path passes through resistor R212 and merges into the same end of resistor R201. The two currents merge into resistor R201 and flow to circuit node P1.

[0146] Choose appropriate resistors R201, R211, and R212 to satisfy both the conditions specified in section (1) above and the following condition: At this time, the voltage across resistor R211 is less than the forward conduction voltage of the PN junction between the emitter (E) and base (B) of the PNP transistor Q201 (or the absolute value of the voltage across resistor R211 is less than the absolute value of the turn-on threshold voltage between the source (S) and gate (G) of the P-channel MOSFET Q201). At this time, Q201 is cut off. Because Q201 is cut off, the current flowing through resistor R202 through the base (B) of the NPN transistor Q202 (or the gate (G) of the N-channel MOSFET Q202) is 0A, and Q202 is cut off. Because Q202 is cut off, the voltage VP2 at circuit node P2 is high. At this time, the current flows from the positive terminal V1 of the first auxiliary power supply, through resistors R203 and R204, the base (B) of the NPN transistor Q204 (or the gate (G) of the N-channel MOSFET Q204), the emitter (E) of the NPN transistor Q204 (or the source (S) of the N-channel MOSFET Q204), and into resistor R208, at which point Q204 is turned on. With Q204 conducting, another larger current flows from the positive terminal V1 of the first auxiliary power supply, through resistor R207, the collector (C) of NPN transistor Q204 (or the drain (D) of N-channel MOSFET Q204), and simultaneously into resistor R208, then through the base (B) of NPN transistor Q206 (or the gate (G) of N-channel MOSFET Q206), the emitter (E) of NPN transistor Q206 (or the source (S) of N-channel MOSFET Q206), and into the cathode of Zener diode ZD202 and one end of capacitor C203. At this time, Q206 conducts.

[0147] With Q206 conducting, another larger current flows from the positive terminal V1 of the first auxiliary power supply, through resistor R209, the collector (C) of the NPN transistor Q206 (or the drain (D) of the N-channel MOSFET Q206), and simultaneously flows with the aforementioned current into the cathode of the Zener diode ZD202 and one end of capacitor C203. Then, through the anode of the Zener diode ZD202 and the other end of capacitor C203, it flows into resistor R1, then through the gate (G) of the N-channel MOSFET Q1. One path flows through resistor R2 into circuit node S1 (reference 0 potential), and the other path flows through the source (S) of the N-channel MOSFET Q1 into circuit node S1 (reference 0 potential). The parasitic capacitance voltage between the gate (G) and source (S) of Q1 gradually increases, and Q1 conducts. At this time, VG1 is at a high level.

[0148] Furthermore, the synchronous rectification integrated circuit 10 also includes: a current change slope detection circuit module 105; the input terminal of the current change slope detection circuit module 105 is connected to the drain of the N-channel transistor Q1, and the output terminal is connected to the output terminal of the level shaping circuit module 106; the current change slope detection circuit module 105 is used to control the output terminal of the level shaping circuit module to a low level when the detected slope of the drain voltage change of the N-channel transistor Q1 is greater than a preset voltage change slope threshold. Specifically, as shown... Figure 4 As shown, the current change slope detection circuit module 105 includes: capacitor C101, resistor R107, diode D104, resistor R108, and NPN transistor Q102; the first end of capacitor C101 is connected to the drain of N-channel transistor Q1, and the second end of capacitor C101 is connected to the first end of resistor R107; the second end of resistor R107 is connected to the cathode of diode D104, the first end of resistor R108, and the base of NPN transistor Q102; the collector of NPN transistor Q102 is connected to the output terminal of level shaping circuit module 106, and the emitter of NPN transistor Q102 is connected to the anode of diode D104, the second end of resistor R108, and the negative power supply S1. The current change slope detection circuit module 105 enables the circuit of this application embodiment to predict the abnormal rise of VD1 voltage in advance when the external circuit is abnormal, and to more quickly switch the output terminal VG1 of the synchronous rectification control integrated circuit 10 to a low level, so as to avoid the N-channel field effect transistor Q1 from short-circuiting with other circuits in the rectifier power supply and burning it out.

[0149] The working principle of the current change slope detection circuit module 105 is as follows:

[0150] (1) When the "synchronous rectification unit" circuit is in the initial state of N-channel field-effect transistor Q1 being turned on, if an external circuit interference factor suddenly occurs, causing the drain (D) voltage VD1 of N-channel field-effect transistor Q1 to rise rapidly. Although the voltage VD1 has not yet reached the critical trigger voltage, the high voltage rise slope of VD1 reduces the capacitive reactance of capacitor C101. At this time, a large current will flow from circuit node D1 through capacitor C101, resistor R107, and resistor R108 into circuit node S1 (reference 0 potential). Because resistor R108 is connected in parallel between the base (B) and emitter (C) of NPN transistor Q102, when the voltage across R108 is greater than the PN junction voltage between the base (B) and emitter (E) of Q102, a portion of the current flows into the base (B) of Q102, through the emitter (E) of Q102, and into circuit node S1 (reference 0 potential). At this time, Q102 is turned on. Because Q102 is turned on, the voltage VP2 between its collector (C) and emitter (E) is low.

[0151] When VP2 is low, the output voltage VG1 of the "synchronous rectification control integrated circuit 10" transitions to a low level. At this time, the N-channel field-effect transistor Q1 transitions from the on state to the off state. Because Q1 turns off early and quickly, the state transition delay effect of the synchronous rectification control integrated circuit 10 is avoided. This prevents Q1 from remaining on when the voltage VD1 rises rapidly above 0V, which would cause an unacceptable reverse current to flow through Q1, thus causing the synchronous rectification unit circuit to lose its rectification function and resulting in a short circuit in the power supply system.

[0152] (2) When the drain (D) voltage VD1 of the N-channel field-effect transistor Q1 is lower than the voltage of its source (S) circuit node S1 (reference 0 potential), the charge stored in capacitor C101 will be discharged through resistors R107 and R108 and diode D104.

[0153] Furthermore, Figure 4 and Figure 5 Some components can be selected using extreme values, such as:

[0154] a. The capacitance values ​​of capacitors C102, C103, C104, C105, C201, and C202 can be 0uF. In this case, the capacitors are in an open-circuit state, and the capacitor symbols do not need to be drawn in the schematic diagram. Figure 6 , Figure 7 , Figure 8 As shown.

[0155] b. The resistance values ​​of resistors R108, R109, R110, R205, R206, R210, R211, and R212 can be infinite, equivalent to an open circuit, and can be omitted. The resistor symbols do not need to be drawn in the schematic diagram. Figure 6 , Figure 7 , Figure 8 As shown.

[0156] c. The resistance values ​​of resistors R111, R204, R207, R208, and R209 can be 0Ω. In this case, the resistor symbol can be replaced by a short circuit, such as... Figure 6 , Figure 8 As shown.

[0157] D.ZD201, ZD202, C203, D201, Q205, Q206, R208, R209, and R210 are circuit function optimization devices and can be omitted. Figure 8 As shown.

[0158] Figure 6 In the circuit, the three-terminal Zener diode IC102 and resistor R101 form a simplified reference voltage circuit 101. With circuit node S1 as the reference potential 0, the reference voltage VR is calculated as shown in Formula 2:

[0159] VR1 = V_IC102 (Formula 2)

[0160] Figure 7 In the circuit, the Zener diode ZD203 and resistor R101 form a simplified reference voltage circuit 101. With circuit node S1 as the reference potential 0, the reference voltage VR is calculated as shown in Formula 3:

[0161] VR1 = V_ZD101 Formula 3

[0162] V_ZD101: Rated Zener voltage of Zener diode ZD101.

[0163] Figure 8 In the circuit 106, a simplified level shaping circuit is formed by a PNP transistor or P-channel MOSFET Q201, an NPN transistor or N-channel MOSFET Q202, and resistors R201, R202, and R204; and a simplified driving circuit is formed by an NPN transistor or N-channel MOSFET Q204, a PNP transistor or P-channel MOSFET Q203, and resistor R205.

[0164] Furthermore, the trigger voltage value conversion circuit module 104 in the synchronous rectification control integrated circuit 10 enables the circuit of the present invention to have two different trigger voltage values ​​for triggering the N-channel field-effect transistor Q1 to turn on and off. For example... Figure 9 As shown, v: voltage axis of the waveform diagram. I: current axis of the waveform diagram. t: time axis of the waveform diagram. Ton: conduction time of N-channel MOSFET Q1. Toff: cutoff time of N-channel MOSFET Q1. VG1: voltage difference between the drive voltage output terminal G1 of the "Synchronous Rectifier Control Integrated Circuit 10" and the reference 0 potential point S1. VD1: voltage difference between the drain (D) of N-channel MOSFET Q1 and the reference 0 potential point S1. I_Q1: current flowing through the channel between the drain (D) and source (S) of N-channel MOSFET Q1, with the positive direction of current flowing from the drain (D) to the source (S). Time period 0-t1: N-channel MOSFET Q1 is cut off, and the drain (D) voltage of Q1 is a positive high voltage. Time period t1-t2: N-channel MOSFET Q1 is triggered to turn on at the VD1_0 voltage point, and the drain (D) voltage of Q1 is a reverse low voltage during this time period. During the time period t2-t3: N-channel field-effect transistor Q1 is triggered to cut off at the VD1_1 voltage point, and the drain (D) voltage of Q1 is a positive high voltage.

[0165] The trigger voltage VD1_0 for Q1 to switch from cutoff to conduction is a low negative voltage, allowing Q1 to definitively determine the current trend in the body diode before switching from cutoff to conduction. Therefore, the circuit of this invention has high anti-interference capability. The trigger voltage VD1_1 for Q1 to switch from conduction to cutoff is close to 0V, so the current in the rectifier circuit can flow through the channel of Q1 almost all the time, minimizing the conduction loss of the rectifier circuit. Therefore, the circuit of this embodiment has high efficiency.

[0166] In summary, this invention enables the application of more efficient synchronous rectification technology in a wider range of rectifier power supply fields. The circuit of this invention boasts high versatility, extremely low cost, high reliability, and high efficiency. It can be widely applied in both specialized industry power supplies and the vast majority of consumer power supplies. This invention meets the technological development trends of the rectifier power supply industry, which emphasize high efficiency, energy saving, reduced consumption, carbon reduction, and high versatility. The circuit of this invention has significant economic and social benefits and holds promise for large-scale application.

Claims

1. A synchronous rectification unit, characterized in that, include: The synchronous rectification integrated circuit and the N-channel transistor Q1; wherein, the synchronous rectification integrated circuit includes: a reference voltage circuit module, a sampling circuit module, a comparator circuit module, a trigger voltage conversion circuit module, a level shaping circuit module, and a drive circuit module; The input terminal of the reference voltage circuit module is connected to the positive and negative terminals of the power supply, respectively, and the output terminal is connected to the first input terminal of the sampling circuit module; the source of the N-channel transistor Q1 is connected to the negative terminal of the power supply. The second input terminal of the sampling circuit module is connected in series with diode D101 and then connected to the drain of N-channel transistor Q1 to acquire the drain voltage of N-channel transistor Q1; the third input terminal of the sampling circuit module is connected to the output terminal of the trigger voltage conversion circuit module, and the output terminal is connected to the reference voltage input terminal of three-terminal Zener diode IC101 in the comparator circuit module; wherein, the sampling circuit module further includes: resistor R102 and resistor R104; the first terminal of resistor R102 is connected to the output terminal VR1 of the reference voltage circuit module, the second terminal of resistor R102 is connected to the output terminal of the trigger voltage conversion circuit module, the reference voltage input terminal of three-terminal Zener diode IC101, and the first terminal of resistor R104; the second terminal of resistor R104 is connected to the anode of diode D101, and the cathode of diode D101 is connected to the drain of N-channel transistor Q1; The comparison output terminal of the three-terminal Zener diode IC101 in the comparison circuit module is connected to the input terminal of the trigger voltage conversion circuit module; the trigger voltage conversion circuit module is used to output a bias current to the sampling circuit module to obtain the first critical trigger voltage value of the drain when the N-channel transistor Q1 is triggered from the on state to the off state, and the second critical trigger voltage value of the drain when the N-channel transistor Q1 is triggered from the off state to the on state. The input terminal of the level shaping circuit module is connected to the comparison output terminal of the comparison circuit module, and the output terminal is connected to the input terminal of the drive circuit module. The output terminal of the driving circuit module is connected to the gate of the N-channel transistor Q1 through a resistor, and is used to control the operating state of the N-channel transistor Q1 according to the drain voltage of the N-channel transistor Q1, the first critical trigger voltage value and the second critical trigger voltage value.

2. The synchronous rectification unit according to claim 1, characterized in that, The reference voltage circuit module includes: resistor R101, resistor R109, resistor R111, capacitor C102, capacitor C103, and three-terminal Zener diode IC102. The first end of the resistor R101 is connected to the positive terminal of the power supply, and the second end of the resistor R101 is connected to the output terminal VR1 of the reference voltage circuit module. The output terminal VR1 is connected to the first terminal of the resistor R111, the first terminal of the capacitor C103, and the cathode of the three-terminal Zener diode IC102, respectively. The reference voltage input terminal of the three-terminal Zener diode IC102 is connected to the second terminal of the resistor R111, the second terminal of the capacitor C103, the first terminal of the capacitor C102, and the first terminal of the resistor R109, respectively. The anode of the three-terminal Zener diode IC102 is connected to the negative terminal of the power supply, the second terminal of the capacitor C102, and the second terminal of the resistor R109, respectively.

3. The synchronous rectification unit according to claim 1, characterized in that, The comparison circuit module also includes: resistor R105 and capacitor C104; The first end of the resistor R105 is connected to the positive terminal of the power supply, and the second end of the resistor R105 is connected to the comparator output terminal of the three-terminal regulator IC101 and the input terminal of the trigger voltage conversion circuit module, respectively. The first terminal of the capacitor C104 is connected to the reference voltage input terminal of the three-terminal Zener diode IC101, and the second terminal of the capacitor C104 is connected to the anode of the three-terminal Zener diode IC101 and the negative terminal of the power supply.

4. The synchronous rectification unit according to claim 1, characterized in that, The trigger voltage conversion circuit module includes: a PNP transistor Q101, a capacitor C105, a resistor R110, a resistor R103, a resistor R106, and a diode D102. The emitter of the PNP transistor Q101 is connected to the output terminal VR1 of the reference voltage circuit module, the first terminal of the capacitor C105, and the first terminal of the resistor R110, respectively. The base of the PNP transistor Q101 is connected to the second terminal of the capacitor C105, the second terminal of the resistor R110, and the first terminal of the resistor R106, respectively. The collector of the PNP transistor Q101 is connected to the first end of the resistor R103, and the second end of the resistor R103 is connected to the third input end of the sampling circuit module. The second end of the resistor R106 is connected to the anode of the diode D102, and the cathode of the diode D102 is connected to the comparator output terminal of the three-terminal Zener diode IC101.

5. The synchronous rectification unit according to claim 1, characterized in that, The level shaping circuit module includes: resistor R201, resistor R212, Zener diode ZD201, capacitor C201, diode D201, resistor R211, capacitor C202, PNP transistor Q201, resistor R202, resistor R205, resistor R203, and NPN transistor Q202. The first end of the resistor R201 is connected to the comparator output terminal of the three-terminal Zener diode IC101, and the second end of the resistor R201 is connected to the first end of the resistor R212, the anode of the Zener diode ZD201, and the first end of the capacitor C201. The second end of the resistor R212 is connected to the cathode of the diode D201, the first end of the resistor R211, the first end of the capacitor C202, the emitter of the PNP transistor Q201, and the first end of the resistor R203. The cathode of the Zener diode ZD201 is connected to the second terminal of the capacitor C201, the anode of the diode D201, the second terminal of the resistor R211, the second terminal of the capacitor C202, and the base of the PNP transistor Q201, respectively. The collector of the PNP transistor Q201 is connected to the first end of the resistor R202, the second end of the resistor R202 is connected to the first end of the resistor R205 and the base of the NPN transistor Q202, and the emitter of the NPN transistor Q202 is connected to the second end of the resistor R205 and the negative terminal of the power supply. The second end of the resistor R203 is connected to the collector of the NPN transistor Q202 and the output terminal P2 of the level shaping circuit module, respectively.

6. The synchronous rectification unit according to claim 5, characterized in that, The driving circuit module includes: resistors R204, R206, and R207; NPN transistor Q204; PNP transistor Q203; resistors R208, R210, and R209; NPN transistor Q206; PNP transistor Q205; Zener diode ZD202; and capacitor C203. Among them, resistors R204, R206, R207, NPN transistor Q204, PNP transistor Q203, resistors R208, R210, R209, NPN transistor Q206, and PNP transistor Q205 constitute a bridge circuit; The bridging circuit is connected to the positive terminal and the negative terminal of the power supply respectively. The input terminal of the bridging circuit is connected to the output terminal P2 of the level shaping circuit module, and the output terminal is connected to the cathode of the Zener diode ZD202 and the first terminal of the capacitor C203 respectively. The anode of the Zener diode ZD202 is connected to the second terminal of the capacitor C203 and connected to the gate of the N-channel transistor Q1 through a resistor.

7. The synchronous rectification unit according to claim 1, characterized in that, Also includes: Current change slope detection circuit module; The input terminal of the current change slope detection circuit module is connected to the drain of the N-channel transistor Q1, and the output terminal is connected to the output terminal of the level shaping circuit module. The current change slope detection circuit module is used to control the output of the level shaping circuit module to be set to a low level when the slope of the drain voltage change of the N-channel transistor Q1 is detected to be greater than a preset voltage change slope threshold.

8. The synchronous rectification unit according to claim 7, characterized in that, The current change slope detection circuit module includes: capacitor C101, resistor R107, diode D104, resistor R108, and NPN transistor Q102. The first terminal of the capacitor C101 is connected to the drain of the N-channel transistor Q1, and the second terminal of the capacitor C101 is connected to the first terminal of the resistor R107. The second end of the resistor R107 is connected to the cathode of the diode D104, the first end of the resistor R108, and the base of the NPN transistor Q102, respectively. The collector of the NPN transistor Q102 is connected to the output terminal of the level shaping circuit module, and the emitter of the NPN transistor Q102 is connected to the anode of the diode D104, the second terminal of the resistor R108, and the negative terminal of the power supply, respectively.

9. The synchronous rectification unit according to claim 1, characterized in that, The synchronous rectification integrated circuit is specifically used to: when the N-channel transistor Q1 is in the on state, if the drain voltage of the N-channel transistor Q1 is less than the first critical trigger voltage value, control the N-channel transistor Q1 to remain in the on state; if the drain voltage of the N-channel transistor Q1 is greater than the first critical trigger voltage value, control the N-channel transistor Q1 to switch to the off state; when the N-channel transistor Q1 is in the off state, if the drain voltage of the N-channel transistor Q1 is greater than the second critical trigger voltage value, control the N-channel transistor Q1 to remain in the off state; if the drain voltage of the N-channel transistor Q1 is less than the second critical trigger voltage value, control the N-channel transistor Q1 to switch to the on state.

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