A BUCK-BOOST full-bridge isolated converter circuit

Abstract

The present invention discloses a BUCK-BOOST full-bridge isolation converter circuit, including a BUCK buck circuit, an active clamp circuit, a full-bridge primary circuit and a full-bridge post-stage synchronous rectification circuit, wherein the input end of the BUCK buck circuit is connected to the input voltage, the output end of the BUCK buck circuit is connected to the input end of the active clamp circuit, the output end of the active clamp circuit is connected to the input end of the full-bridge primary circuit, the output end of the full-bridge primary circuit is connected to the input end of the full-bridge post-stage synchronous rectification circuit, and the output end of the full-bridge post-stage synchronous rectification circuit is connected to the output voltage; the BUCK buck circuit includes a BUCK upper tube Q10 and a BUCK lower tube Q11; the MOS tubes of the full-bridge primary circuit all work in a duty cycle mode greater than 50%. The present invention can not only realize the functions of a traditional BUCK-BOOST full-bridge circuit, but also reduce costs and greatly reduce the layout space of a module power supply.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply, and in particular to a BUCK-BOOST full-bridge isolation converter circuit. Background Art

[0002] In the current field of power supply technology, especially in the context of the growing demand for high efficiency and energy saving, the design and optimization of power conversion circuits has become a research hotspot. As a power conversion circuit that can achieve step-up and step-down, the BUCK-BOOST circuit has been widely used in various power supply systems.

[0003] In the traditional four-arm BUCK-BOOST full-bridge circuit, the front stage is a four-arm BUCK-BOOST, including a BUCK upper tube, a BUCK lower tube, a BOOST upper tube and a BOOST lower tube. The BUCK upper tube and the BUCK lower tube are alternately and complementary turned on, and the BOOST upper tube and the BOOST lower tube are alternately and complementary turned on. This stage is a buck-boost circuit. When working in boost, the BUCK upper tube is directly turned on, and the BOOST upper tube and the BOOST lower tube start to boost. When bucking, the BOOST upper tube is directly turned on, and the BUCK upper tube and the BUCK lower tube start to buck. When bucking, the four tubes work simultaneously. The back stage is an open-loop full bridge, which isolates the output of the four-arm BUCK-BOOST.

[0004] Although the traditional four-arm BUCK-BOOST full-bridge circuit can provide higher conversion efficiency and certain electrical isolation functions, it still faces a series of problems in practical applications.

[0005] First, the cost of the traditional four-arm BUCK-BOOST full-bridge circuit is relatively high. This is mainly because the power circuit of the circuit is complex and requires the use of more electronic components, especially a large number of MOS tubes, which does not meet the requirements of energy saving and high efficiency.

[0006] Secondly, the traditional four-arm BUCK-BOOST full-bridge circuit has a large demand for MOS tubes, which not only increases the cost of the circuit, but also makes the PCB layout of the circuit compact and complicated. In the PCB layout, the arrangement and connection of components need to fully consider factors such as electrical performance, heat dissipation performance and mechanical strength, while the large number and large size of MOS tubes bring great challenges to the PCB layout. In addition, the compact PCB layout may also increase the electromagnetic interference and noise of the circuit, affecting the stability and reliability of the circuit. Summary of the invention

[0007] In order to overcome the problems of high cost, large MOS tube requirement and compact PCB layout of the four-bridge-arm BUCK-BOOST full-bridge circuit in the prior art, the present invention provides a BUCK-BOOST full-bridge isolation converter circuit.

[0008] The technical solution of the present invention is as follows:

[0009] A BUCK-BOOST full-bridge isolated converter circuit comprises a BUCK buck circuit, an active clamp circuit, a full-bridge primary circuit and a full-bridge post-stage synchronous rectification circuit, wherein the input end of the BUCK buck circuit is connected to an input voltage, the output end of the BUCK buck circuit is connected to the input end of the active clamp circuit, the output end of the active clamp circuit is connected to the input end of the full-bridge primary circuit, the output end of the full-bridge primary circuit is connected to the input end of the full-bridge post-stage synchronous rectification circuit, and the output end of the full-bridge post-stage synchronous rectification circuit is connected to the output voltage;

[0010] The BUCK step-down circuit includes a BUCK upper tube Q10 and a BUCK lower tube Q11, and the BUCK upper tube Q10 and the BUCK lower tube Q11 are alternately and complementary turned on;

[0011] The MOS tubes of the full-bridge primary circuit all operate in a duty cycle mode greater than 50%;

[0012] The active clamping circuit is used to absorb the MOS tube turn-off stress of the full-bridge primary circuit when the full-bridge primary circuit is in a common state.

[0013] According to the BUCK-BOOST full-bridge isolation converter circuit of the above scheme, the BUCK step-down circuit further includes a capacitor C14, a capacitor C15, a capacitor C16, a capacitor C17, a diode D3, a resistor R1, a resistor R2, a resistor R4, a resistor R5, a resistor R8, a resistor R78 and an energy storage inductor L1, one end of the capacitor C14, one end of the capacitor C15, one end of the capacitor C16, one end of the capacitor C17 and a first end of the BUCK upper tube Q10 are all connected to the positive electrode of the input voltage, the second end of the BUCK upper tube Q10 is respectively connected to the first end of the BUCK lower tube Q11, the first end of the resistor R4 and one end of the inductor, the second end of the BUCK upper tube Q10 is respectively connected to one end of the resistor R1, the One end of the resistor R2 and the other end of the resistor R4 are connected, the other end of the resistor R1 is respectively connected to the other end of the resistor R2 and the first driving signal after passing through the diode D3, the other end of the capacitor C14, the other end of the capacitor C15, the other end of the capacitor C16, the other end of the capacitor C17, one end of the resistor R8, one end of the resistor R78 and the second end of the BUCK lower tube Q11 are all connected to the negative electrode of the input voltage, the third end of the BUCK lower tube Q11 is respectively connected to one end of the resistor R5 and the other end of the resistor R8, the other end of the resistor R5 is connected to the second driving signal, the other end of the resistor R78 is grounded, and the other end of the energy storage inductor L1 is connected to the input end of the active clamping circuit.

[0014] According to the BUCK-BOOST full-bridge isolation converter circuit of the above scheme, the active clamping circuit includes a MOS tube Q5, a capacitor C4, a capacitor C13, a resistor R15, a diode D1, and a diode D2. One end of the capacitor C4 and one end of the capacitor C13 are both connected to the output end of the BUCK step-down circuit. The first end of the MOS tube Q5 is respectively connected to the other end of the capacitor C4, the other end of the capacitor C13, one end of the diode D1, and one end of the diode D2. The second end of the MOS tube Q5, one end of the resistor R15, the other end of the diode D1, and the other end of the diode D2 are all grounded. The third end of the MOS tube Q5 is respectively connected to the other end of the resistor R15 and the third drive signal.

[0015] Furthermore, when the full-bridge primary circuit is in a common state, the MOS tube Q5 is in a closed state, and the capacitor C4 and the capacitor C13 absorb the MOS tube turn-off stress of the full-bridge primary circuit.

[0016] Furthermore, the active clamping circuit also includes an RC absorption circuit composed of a resistor R14 and a capacitor C3, one end of the resistor R14 is connected to the output end of the BUCK step-down circuit, and the other end of the resistor R14 is grounded after passing through the capacitor C3.

[0017] According to the BUCK-BOOST full-bridge isolated converter circuit of the above scheme, the full-bridge primary circuit includes a MOS upper tube Q1, a MOS lower tube Q2, a MOS lower tube Q3, and a MOS upper tube Q4. The first end of the MOS upper tube Q1 and the first end of the MOS upper tube Q4 are both connected to the output end of the BUCK step-down circuit. The second end of the MOS upper tube Q1 and the first end of the MOS lower tube Q2 are respectively connected to one end of the primary side of the transformer T2. The first end of the MOS lower tube Q3 and the second end of the MOS upper tube Q4 are respectively connected to the other end of the primary side of the transformer T2. The second end of the MOS lower tube Q2 and the second end of the MOS lower tube Q3 are both grounded. The third end of the MOS upper tube Q1, the third end of the MOS lower tube Q2, the third end of the MOS lower tube Q3, and the third end of the MOS upper tube Q4 are respectively connected to the fourth drive signal, the fifth drive signal, the sixth drive signal, and the seventh drive signal.

[0018] Furthermore, the MOS upper tube Q1 and the MOS lower tube Q2 are alternately and complementary turned on, the MOS lower tube Q3 and the MOS upper tube Q4 are alternately and complementary turned on, the timing pulse width of the MOS upper tube Q1 and the MOS lower tube Q3 is the same, and the timing pulse width of the MOS lower tube Q2 and the MOS upper tube Q4 is the same.

[0019] Furthermore, when the full-bridge primary circuit is in a common state, the MOS upper tube Q1 and the MOS lower tube Q2 or the MOS lower tube Q3 and the MOS upper tube Q4 are short-circuited to the ground, so as to store energy for the energy storage inductor L1 of the BUCK step-down circuit;

[0020] The energy storage inductor L1 of the BUCK step-down circuit discharges energy when the MOS upper tube Q1, the MOS lower tube Q2, the MOS lower tube Q3 and the MOS upper tube Q4 work alternately, thereby achieving a boosting effect.

[0021] Further, the full-bridge primary circuit also includes a resistor R3, a resistor R6, a resistor R7, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R25, a capacitor C1, and a capacitor C2. The third end of the MOS upper tube Q1 is connected to one end of the resistor R7 and the resistor R9 respectively, the other end of the resistor R7 is connected to the fourth drive signal, the other end of the resistor R9 is connected to the second end of the MOS upper tube Q1, the first end of the MOS lower tube Q2, one end of the resistor R6, one end of the capacitor C1, and one end of the capacitor C2 respectively, and the other end of the resistor R6, the other end of the capacitor C1, and the other end of the capacitor C2 are all connected to the variable The first embodiment of the present invention is connected to the primary side of the transformer T2, the third end of the MOS lower tube Q2 is connected to one end of the resistor R11 and the resistor R12 respectively, the other end of the resistor R12 is connected to the fifth driving signal, the third end of the MOS lower tube Q3 is connected to one end of the resistor R13 and the resistor R25 respectively, the other end of the resistor R13 is connected to the sixth driving signal, the other end of the resistor R11 and the other end of the resistor R25 are grounded, the third end of the MOS upper tube Q4 is connected to one end of the resistor R3 and the resistor R10 respectively, the other end of the resistor R10 is connected to the seventh driving signal, and the other end of the resistor R3 is connected to the other end of the primary side of the transformer T2.

[0022] Further, the full-bridge rear-stage synchronous rectification circuit includes a MOS upper tube Q6, a MOS upper tube Q7, a MOS lower tube Q8, a MOS lower tube Q9 and an output LC filter circuit, the first end of the MOS upper tube Q6 and the first end of the MOS upper tube Q7 are both connected to one end of the output LC filter circuit, the second end of the MOS upper tube Q6 and the first end of the MOS lower tube Q8 are respectively connected to one end of the secondary side of the transformer T2, the second end of the MOS upper tube Q7 and the first end of the MOS lower tube Q8 are respectively connected to the other end of the primary side of the transformer T2, the second end of the MOS lower tube Q8 and the second end of the MOS lower tube Q9 are both grounded, the third end of the MOS upper tube Q6, the third end of the MOS upper tube Q7, the third end of the MOS lower tube Q8 and the third end of the MOS lower tube Q9 are respectively connected to the eighth drive signal, the ninth drive signal, the tenth drive signal and the eleventh drive signal, and the other end of the output LC filter circuit is connected to the output voltage.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention improves the traditional four-bridge BUCK-BOOST full-bridge circuit, changes the turn-on timing of the full-bridge MOS tube, and saves a pair of BOOST upper and lower tubes in the BUCK-BOOST circuit. It can not only realize the functions of the traditional BUCK-BOOST full-bridge circuit, but also reduce the cost and greatly reduce the layout space of the module power supply;

[0025] 2. The circuit structure is more concise, reducing the source of electromagnetic interference and noise, which is conducive to improving the electrical performance of the circuit; by optimizing the circuit design, unnecessary components and losses are reduced, thereby improving the overall efficiency;

[0026] 3. Due to the reduction in the number of components and the optimization of the layout space, the circuit of the present invention can provide higher power output under the same volume, that is, the power density is improved;

[0027] 4. By adding an active clamping circuit, the turn-off stress of the MOS tube can be absorbed when the full-bridge primary circuit is in a common state, thereby reducing the turn-off stress and improving the stability and reliability of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, 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 present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a structural block diagram of a BUCK-BOOST full-bridge isolation converter circuit in one embodiment of the present invention;

[0030] Figure 2 is a circuit diagram of a BUCK step-down circuit in one embodiment of the present invention;

[0031] Figure 3 is a circuit diagram of an active clamping circuit in one embodiment of the present invention;

[0032] Figure 4 is a circuit diagram of a full-bridge primary circuit in one embodiment of the present invention;

[0033] Figure 5 1 is a circuit diagram of a full-bridge rear-stage synchronous rectification circuit in one embodiment of the present invention;

[0034] Figure 6 FIG. 1 is a timing diagram of the operation of the BUCK-BOOST full-bridge isolation converter circuit in various modes according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. It is also stated that the embodiments described below are only used to explain the present invention and are not used to limit the present invention.

[0036] It should be noted that the term "connection" and other terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined.

[0037] See also Figures 1 to 5 The present embodiment provides a BUCK-BOOST full-bridge isolation converter circuit, including a BUCK buck circuit 1, an active clamp circuit 2, a full-bridge primary circuit 3 and a full-bridge post-stage synchronous rectification circuit 4, wherein the input end of the BUCK buck circuit 1 is connected to the input voltage, the output end of the BUCK buck circuit 1 is connected to the input end of the active clamp circuit 2, the output end of the active clamp circuit 2 is connected to the input end of the full-bridge primary circuit 3, the output end of the full-bridge primary circuit 3 is connected to the input end of the full-bridge post-stage synchronous rectification circuit 4, and the output end of the full-bridge post-stage synchronous rectification circuit 4 is connected to the output voltage.

[0038] BUCK step-down circuit 1 plays a role in reducing the voltage in the entire circuit. Figure 5The buck step-down circuit 1 includes a buck upper tube Q10, a buck lower tube Q11, a capacitor C14, a capacitor C15, a capacitor C16, a capacitor C17, a diode D3, a resistor R1, a resistor R2, a resistor R4, a resistor R5, a resistor R8, a resistor R78 and an energy storage inductor L1. One end of the capacitor C14, one end of the capacitor C15, one end of the capacitor C16, one end of the capacitor C17 and a first end of the buck upper tube Q10 are all connected to the positive electrode of the input voltage. The second end of the buck upper tube Q10 is respectively connected to the first end of the buck lower tube Q11, the first end of the resistor R4 and one end of the inductor. The second end of the buck upper tube Q10 is respectively connected to the first end of the resistor R1. The first end of the BUCK upper tube Q10 and the second end of the BUCK lower tube Q11 are connected to the first end of the active clamp circuit 2. The second end of the BUCK upper tube Q10 and the second end of the BUCK lower tube Q11 are connected to the first end of the active clamp circuit 2. The second end of the BUCK upper tube Q10 and the second end of the BUCK lower tube Q11 are connected to the first end of the active clamp circuit 2. The second end of the BUCK upper tube Q10 and the second end of the BUCK lower tube Q11 are connected to the first end of the active clamp circuit 2. The second end of the BUCK upper tube Q10 and the second end of the BUCK lower tube Q11 are connected to the first end of the active clamp circuit 2. The second end of the BUCK upper tube Q10 and the second end of the BUCK lower tube Q11 are connected to the first end of the active clamp circuit 2.

[0039] The active clamp circuit 2 is used to absorb the MOS tube turn-off stress of the full-bridge primary circuit 3 and clamp the full-bridge input voltage when the full-bridge primary circuit 3 is in a common state. Figure 3 The active clamp circuit 2 includes a MOS tube Q5, a capacitor C4, a capacitor C13, a resistor R15, a diode D1, and a diode D2. One end of the capacitor C4 and one end of the capacitor C13 are both connected to the output end of the BUCK step-down circuit 1. The first end of the MOS tube Q5 is respectively connected to the other end of the capacitor C4, the other end of the capacitor C13, one end of the diode D1, and one end of the diode D2. The second end of the MOS tube Q5, one end of the resistor R15, the other end of the diode D1, and the other end of the diode D2 are all grounded. The third end of the MOS tube Q5 is respectively connected to the other end of the resistor R15 and the third drive signal. When the full-bridge primary circuit 3 is in a common state, the MOS tube Q5 is in a closed state, so that the MOS tube turn-off stress of the full-bridge primary circuit 3 is absorbed through the capacitor C4 and the capacitor C13, and the full-bridge input voltage is clamped.

[0040] Furthermore, in one embodiment, in order to enhance the absorption effect, the active clamping circuit 2 further includes an RC absorption circuit composed of a resistor R14 and a capacitor C3, one end of the resistor R14 is connected to the output end of the BUCK step-down circuit 1, and the other end of the resistor R14 is grounded after passing through the capacitor C3.

[0041] See also Figure 4 The full-bridge primary circuit 3 includes a MOS upper tube Q1, a MOS lower tube Q2, a MOS lower tube Q3, and a MOS upper tube Q4. The first end of the MOS upper tube Q1 and the first end of the MOS upper tube Q4 are both connected to the output end of the BUCK step-down circuit 1. The second end of the MOS upper tube Q1 and the first end of the MOS lower tube Q2 are respectively connected to one end of the primary side of the transformer T2. The first end of the MOS lower tube Q3 and the second end of the MOS upper tube Q4 are respectively connected to the other end of the primary side of the transformer T2. The second end of the MOS lower tube Q2 and the second end of the MOS lower tube Q3 are both grounded. The third end of the MOS upper tube Q1, the third end of the MOS lower tube Q2, the third end of the MOS lower tube Q3, and the third end of the MOS upper tube Q4 are respectively connected to the fourth drive signal, the fifth drive signal, the sixth drive signal, and the seventh drive signal. Among them, the MOS upper tube Q1, the MOS lower tube Q2, the MOS lower tube Q3, and the MOS upper tube Q4 all work in a duty cycle mode greater than 50%, the MOS upper tube Q1 and the MOS lower tube Q2 are alternately and complementary turned on, the MOS lower tube Q3 and the MOS upper tube Q4 are alternately and complementary turned on, the timing pulse width of the MOS upper tube Q1 and the MOS lower tube Q3 is the same, and the timing pulse width of the MOS lower tube Q2 and the MOS upper tube Q4 is the same. In an ideal state, when the duty cycle is 50%, the upper and lower tubes work alternately and complementary, so that the conduction time greater than 50% of the duty cycle is the common time of the upper and lower tubes.

[0042] The full-bridge primary circuit 3 arranged as above has a BOOST function. When the full-bridge primary circuit 3 is in a common state, the MOS upper tube Q1 and the MOS lower tube Q2 or the MOS lower tube Q3 and the MOS upper tube Q4 are short-circuited to the ground, so as to store energy for the energy storage inductor L1 of the BUCK step-down circuit 1. In the next stage (the upper and lower tubes are not common), the energy storage inductor L1 of the BUCK step-down circuit 1 releases energy when the MOS upper tube Q1, the MOS lower tube Q2, the MOS lower tube Q3 and the MOS upper tube Q4 work alternately, so as to achieve a boost effect.

[0043] See also Figure 4In one embodiment, the full-bridge primary circuit 3 further includes a resistor R3, a resistor R6, a resistor R7, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R25, a capacitor C1, and a capacitor C2. The third end of the MOS upper tube Q1 is connected to one end of the resistor R7 and the resistor R9 respectively, the other end of the resistor R7 is connected to the fourth drive signal, the other end of the resistor R9 is connected to the second end of the MOS upper tube Q1, the first end of the MOS lower tube Q2, one end of the resistor R6, one end of the capacitor C1, and one end of the capacitor C2 respectively, the other end of the resistor R6, the other end of the capacitor C1, and the other end of the capacitor C2 One end is connected to one end of the primary side of transformer T2, the third end of MOS lower tube Q2 is connected to one end of resistor R11 and resistor R12 respectively, the other end of resistor R12 is connected to the fifth drive signal, the third end of MOS lower tube Q3 is connected to one end of resistor R13 and resistor R25 respectively, the other end of resistor R13 is connected to the sixth drive signal, the other end of resistor R11 and the other end of resistor R25 are grounded, the third end of MOS upper tube Q4 is connected to one end of resistor R3 and resistor R10 respectively, the other end of resistor R10 is connected to the seventh drive signal, and the other end of resistor R3 is connected to the other end of the primary side of transformer T2. The above resistors R3, R7, R9, R10, R11, R12, R13, and R25 are used to provide the gate drive current of the MOS tube and help stabilize the working state of the circuit; resistor R6, capacitor C1, and capacitor C2 form an RC filter network, which is used to smooth the fluctuation of the input voltage of transformer T2 and improve the stability of the circuit.

[0044] See also Figure 5 In one embodiment, the full-bridge rear stage synchronous rectification circuit 4 includes a MOS upper tube Q6, a MOS upper tube Q7, a MOS lower tube Q8, a MOS lower tube Q9 and an output LC filter circuit, the first end of the MOS upper tube Q6 and the first end of the MOS upper tube Q7 are both connected to one end of the output LC filter circuit, the second end of the MOS upper tube Q6 and the first end of the MOS lower tube Q8 are respectively connected to one end of the secondary side of the transformer T2, the second end of the MOS upper tube Q7 and the first end of the MOS lower tube Q8 are respectively connected to the other end of the primary side of the transformer T2, the second end of the MOS lower tube Q8 and the second end of the MOS lower tube Q9 are both grounded, the third end of the MOS upper tube Q6, the third end of the MOS upper tube Q7, the third end of the MOS lower tube Q8 and the third end of the MOS lower tube Q9 are respectively connected to the eighth drive signal, the ninth drive signal, the tenth drive signal and the eleventh drive signal, and the other end of the output LC filter circuit is connected to the output voltage. The bridge arms of the full-bridge rear stage synchronous rectification circuit 4 are complementary conduction rectified. The output LC filter circuit consists of inductor L2, capacitor C9, capacitor C10, capacitor C11 and capacitor C12, and is used to smooth the rectified output voltage and reduce voltage fluctuation and ripple.

[0045] The present invention uses a specific implementation case to perform timing analysis on the circuit below:

[0046] Assume that the full-bridge turns ratio is 1:1, that is, n=1, and the switching period is T. Figure 6 It is a working timing diagram of the BUCK-BOOST full-bridge isolation converter circuit in various modes of the present invention.

[0047] When entering the working range of BUCK mode, the BUCK upper tube Q10 and the BUCK lower tube Q11 work alternately, D_buck is the duty cycle of the BUCK tube, and the full bridge has a 50% duty cycle (or a little greater than 50%, there is a minimum common time T1, which must satisfy that the full bridge tube has no dead zone and is always in the on state. This is the minimum duty cycle of the full bridge), and the output voltage is Vo=Vin*D_buck*n.

[0048] When entering the BUCK_BOOST mode working range, the BUCK upper tube Q10 and the BUCK lower tube Q11 work alternately. At this time, the full-bridge common time T2 begins to increase as the input decreases, and the output voltage is Vo = Vin*D_buck / (1-D_boost)*n, where D_boost = 2*T2 / T, and T2 is the full-bridge common time.

[0049] When entering the BOOST mode working range, the BUCK upper tube Q10 works directly. At this time, the full-bridge common time T2 continues to increase as the input decreases, and the output voltage is Vo=Vin / (1-D_boost)*n, where D_boost=2*T3 / T, T3 is the full-bridge common time.

[0050] In summary, the present invention improves the traditional four-arm BUCK-BOOST full-bridge circuit, changes the turn-on timing of the full-bridge MOS tube, and saves a pair of BOOST upper and lower tubes in the BUCK-BOOST circuit, which not only can realize the function of the traditional BUCK-BOOST full-bridge circuit, but also reduces the cost and greatly reduces the layout space of the module power supply; the circuit structure is more concise, reduces the source of electromagnetic interference and noise, and is conducive to improving the electrical performance of the circuit; by optimizing the circuit design, unnecessary components and losses are reduced, thereby improving the overall efficiency; due to the reduction in the number of components and the optimization of the layout space, the circuit of the present invention can provide higher power output at the same volume, that is, the power density is improved; by adding an active clamping circuit 2, it can absorb the turn-off stress of the MOS tube when the full-bridge primary circuit 3 is in a common state, clamp the full-bridge input voltage, and improve the stability and reliability of the circuit.

[0051] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

[0052] The above is an exemplary description of the present invention in conjunction with the accompanying drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A BUCK-BOOST full-bridge isolated converter circuit, characterized in that: It includes a BUCK buck circuit, an active clamp circuit, a full-bridge primary circuit and a full-bridge rear-stage synchronous rectification circuit, wherein the input end of the BUCK buck circuit is connected to an input voltage, the output end of the BUCK buck circuit is connected to the input end of the active clamp circuit, the output end of the active clamp circuit is connected to the input end of the full-bridge primary circuit, the output end of the full-bridge primary circuit is connected to the input end of the full-bridge rear-stage synchronous rectification circuit, and the output end of the full-bridge rear-stage synchronous rectification circuit is connected to the output voltage; The BUCK step-down circuit includes a BUCK upper tube Q10 and a BUCK lower tube Q11, and the BUCK upper tube Q10 and the BUCK lower tube Q11 are alternately and complementary turned on; The MOS tubes of the full-bridge primary circuit all operate in a duty cycle mode greater than 50%; The active clamping circuit is used to absorb the MOS tube turn-off stress of the full-bridge primary circuit when the full-bridge primary circuit is in a common state.

2. The BUCK-BOOST full-bridge isolated converter circuit according to claim 1, characterized in that: The BUCK step-down circuit further includes a capacitor C14, a capacitor C15, a capacitor C16, a capacitor C17, a diode D3, a resistor R1, a resistor R2, a resistor R4, a resistor R5, a resistor R8, a resistor R78 and an energy storage inductor L1. One end of the capacitor C14, one end of the capacitor C15, one end of the capacitor C16, one end of the capacitor C17 and a first end of the BUCK upper tube Q10 are all connected to the positive electrode of the input voltage. The second end of the BUCK upper tube Q10 is respectively connected to the first end of the BUCK lower tube Q11, the first end of the resistor R4 and one end of the inductor. The second end of the BUCK upper tube Q10 is respectively connected to one end of the resistor R1, one end of the resistor R2 and one end of the resistor R 4, the other end of the resistor R1 is connected to the other end of the resistor R2 and the first driving signal respectively after passing through the diode D3, the other end of the capacitor C14, the other end of the capacitor C15, the other end of the capacitor C16, the other end of the capacitor C17, one end of the resistor R8, one end of the resistor R78 and the second end of the buck lower tube Q11 are all connected to the negative electrode of the input voltage, the third end of the buck lower tube Q11 is respectively connected to one end of the resistor R5 and the other end of the resistor R8, the other end of the resistor R5 is connected to the second driving signal, the other end of the resistor R78 is grounded, and the other end of the energy storage inductor L1 is connected to the input end of the active clamping circuit.

3. The BUCK-BOOST full-bridge isolated converter circuit according to claim 1, characterized in that: The active clamping circuit includes a MOS tube Q5, a capacitor C4, a capacitor C13, a resistor R15, a diode D1, and a diode D2. One end of the capacitor C4 and one end of the capacitor C13 are both connected to the output end of the BUCK step-down circuit. The first end of the MOS tube Q5 is respectively connected to the other end of the capacitor C4, the other end of the capacitor C13, one end of the diode D1, and one end of the diode D2. The second end of the MOS tube Q5, one end of the resistor R15, the other end of the diode D1, and the other end of the diode D2 are all grounded. The third end of the MOS tube Q5 is respectively connected to the other end of the resistor R15 and the third drive signal.

4. The BUCK-BOOST full-bridge isolated converter circuit according to claim 3, characterized in that: When the full-bridge primary circuit is in a common state, the MOS transistor Q5 is in a closed state, and the capacitor C4 and the capacitor C13 absorb the MOS transistor turn-off stress of the full-bridge primary circuit.

5. The BUCK-BOOST full-bridge isolated converter circuit according to claim 3, characterized in that: The active clamping circuit further includes an RC absorption circuit composed of a resistor R14 and a capacitor C3, one end of the resistor R14 is connected to the output end of the BUCK step-down circuit, and the other end of the resistor R14 is grounded after passing through the capacitor C3.

6. The BUCK-BOOST full-bridge isolated converter circuit according to claim 1, characterized in that: The full-bridge primary circuit includes a MOS upper tube Q1, a MOS lower tube Q2, a MOS lower tube Q3, and a MOS upper tube Q4. The first end of the MOS upper tube Q1 and the first end of the MOS upper tube Q4 are both connected to the output end of the BUCK step-down circuit. The second end of the MOS upper tube Q1 and the first end of the MOS lower tube Q2 are respectively connected to one end of the primary side of the transformer T2. The first end of the MOS lower tube Q3 and the second end of the MOS upper tube Q4 are respectively connected to the other end of the primary side of the transformer T2. The second end of the MOS lower tube Q2 and the second end of the MOS lower tube Q3 are both grounded. The third end of the MOS upper tube Q1, the third end of the MOS lower tube Q2, the third end of the MOS lower tube Q3, and the third end of the MOS upper tube Q4 are respectively connected to the fourth drive signal, the fifth drive signal, the sixth drive signal, and the seventh drive signal.

7. The BUCK-BOOST full-bridge isolated converter circuit according to claim 6, characterized in that: The MOS upper tube Q1 and the MOS lower tube Q2 are alternately and complementary turned on, the MOS lower tube Q3 and the MOS upper tube Q4 are alternately and complementary turned on, the timing pulse width of the MOS upper tube Q1 and the MOS lower tube Q3 are the same, and the timing pulse width of the MOS lower tube Q2 and the MOS upper tube Q4 are the same.

8. The BUCK-BOOST full-bridge isolated converter circuit according to claim 7, characterized in that: When the full-bridge primary circuit is in a common state, the MOS upper tube Q1 and the MOS lower tube Q2 or the MOS lower tube Q3 and the MOS upper tube Q4 are short-circuited to the ground, so as to store energy for the energy storage inductor L1 of the BUCK step-down circuit; The energy storage inductor L1 of the BUCK step-down circuit discharges energy when the MOS upper tube Q1, the MOS lower tube Q2, the MOS lower tube Q3 and the MOS upper tube Q4 work alternately, thereby achieving a boosting effect.

9. The BUCK-BOOST full-bridge isolated converter circuit according to claim 6, characterized in that: The full-bridge primary circuit further includes a resistor R3, a resistor R6, a resistor R7, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R25, a capacitor C1, and a capacitor C2. The third end of the MOS upper tube Q1 is connected to one end of the resistor R7 and the resistor R9 respectively, the other end of the resistor R7 is connected to the fourth drive signal, the other end of the resistor R9 is connected to the second end of the MOS upper tube Q1, the first end of the MOS lower tube Q2, one end of the resistor R6, one end of the capacitor C1, and one end of the capacitor C2 respectively, the other end of the resistor R6, the other end of the capacitor C1, and the other end of the capacitor C2 are all connected to the transformer T 2, a third end of the MOS lower tube Q2 is connected to one end of the resistor R11 and the resistor R12 respectively, the other end of the resistor R12 is connected to the fifth driving signal, a third end of the MOS lower tube Q3 is connected to one end of the resistor R13 and the resistor R25 respectively, the other end of the resistor R13 is connected to the sixth driving signal, the other end of the resistor R11 and the other end of the resistor R25 are grounded, a third end of the MOS upper tube Q4 is connected to one end of the resistor R3 and the resistor R10 respectively, the other end of the resistor R10 is connected to the seventh driving signal, and the other end of the resistor R3 is connected to the other end of the primary side of the transformer T2.

10. The BUCK-BOOST full-bridge isolated converter circuit according to claim 6, characterized in that: The full-bridge rear-stage synchronous rectification circuit includes a MOS upper tube Q6, a MOS upper tube Q7, a MOS lower tube Q8, a MOS lower tube Q9 and an output LC filter circuit, wherein the first end of the MOS upper tube Q6 and the first end of the MOS upper tube Q7 are both connected to one end of the output LC filter circuit, the second end of the MOS upper tube Q6 and the first end of the MOS lower tube Q8 are respectively connected to one end of the secondary side of the transformer T2, the second end of the MOS upper tube Q7 and the first end of the MOS lower tube Q8 are respectively connected to the other end of the primary side of the transformer T2, the second end of the MOS lower tube Q8 and the second end of the MOS lower tube Q9 are both grounded, the third end of the MOS upper tube Q6, the third end of the MOS upper tube Q7, the third end of the MOS lower tube Q8 and the third end of the MOS lower tube Q9 are respectively connected to the eighth drive signal, the ninth drive signal, the tenth drive signal and the eleventh drive signal, and the other end of the output LC filter circuit is connected to the output voltage.

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