Power supply system with wide voltage adjusting range

Abstract

The invention discloses a power supply system with a wide voltage regulation range, which comprises a circuit with a wide voltage regulation range, and is characterized in that the circuit with the wide voltage regulation range comprises a full-bridge LLC resonant circuit, a resonant transformer, a full-bridge BUCK circuit and a follow current circuit; the full-bridge LLC resonant circuit is connected with the full-bridge BUCK circuit and the follow current circuit through a resonant transformer, and the follow current circuit and the full-bridge BUCK circuit are connected by sharing at least two diodes. Zero-voltage switching of a switching tube is realized through the full-bridge LLC resonant circuit, so that the circuit efficiency is improved, meanwhile, most of output power of a secondary side of the transformer is transmitted to a load through the follow current circuit, and the rest small part of output power is provided with relatively low efficiency through the full-bridge BUCK circuit, and the output voltage is adjusted. The power supply system provided by the invention has an adjustable wide voltage output range while having high-efficiency conversion capability.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a power supply system with a wide voltage adjustment range. Background Art

[0002] As electronic devices continue to develop, the performance of the power supply system is crucial. Traditional power supply systems have obvious shortcomings. Their voltage adjustment range is relatively narrow. In most cases, they can only operate stably within a limited input voltage range. Once this range is exceeded, it is difficult to ensure stable voltage output, which will not only cause abnormal operation of the equipment, but may also directly damage the equipment, greatly reducing the reliability and service life of the equipment. Therefore, it is very necessary to realize a power supply system with a wide voltage adjustment range.

[0003] In the face of application scenarios that require a wide range of output voltage, the output voltage of the traditional LLC resonant circuit in the power supply system mainly depends on the resonance parameters and the input voltage, and its output voltage adjustment range is relatively narrow, so it is difficult to meet the demand by relying solely on the LLC circuit. In the prior art, there is a solution that uses a traditional LLC resonant circuit cascaded with a BUCK circuit. Although this solution can achieve a wider output voltage adjustment range to a certain extent, its overall efficiency is the multiplication of the efficiencies of the two circuits, and its efficiency is not as good as that of the traditional LLC resonant circuit. Summary of the invention

[0004] The purpose of the present invention is to provide a power supply system with a wide voltage adjustment range, which has high-efficiency conversion capability and an adjustable wide voltage output range.

[0005] To achieve the above objectives, an embodiment of the present invention provides a power supply system with a wide voltage adjustment range, including a circuit with a wide voltage adjustment range, wherein the circuit with a wide voltage adjustment range includes a full-bridge LLC resonant circuit, a resonant transformer, a full-bridge BUCK circuit and a freewheeling circuit;

[0006] The full-bridge LLC resonant circuit is connected to the full-bridge BUCK circuit and the freewheeling circuit through the resonant transformer, and the freewheeling circuit is connected to the full-bridge BUCK circuit by sharing at least two diodes;

[0007] The full-bridge LLC resonant circuit is used to operate at a fixed resonant frequency and a preset dead time to achieve zero voltage switching of the switch tube in the full-bridge LLC resonant circuit; the freewheeling circuit is used to transmit the first part of the output power; the full-bridge BUCK circuit is used to adjust the output voltage and provide the second part of the output power; wherein the first part of the output power is greater than the second part of the output power.

[0008] In an optional embodiment, the full-bridge BUCK circuit includes a full-bridge rectifier circuit, a fifth switch tube, a filter circuit and an output circuit;

[0009] One end of the full-bridge rectifier circuit is connected to one end of the filter circuit, the other end of the filter circuit is connected to the source of the fifth switch tube, the drain of the fifth switch tube is connected to one end of the output circuit, and the other end of the output circuit is respectively connected to the other end of the full-bridge rectifier circuit and one end of the freewheeling circuit.

[0010] In an optional embodiment, the freewheeling circuit includes at least one freewheeling diode;

[0011] The freewheeling circuit is used to cooperate with the full-bridge BUCK circuit to deliver the first part of the output power when the fifth switch tube is turned off.

[0012] In an optional embodiment, the full-bridge BUCK circuit is used to adjust the duty cycle of the fifth switch tube to adjust the output voltage, and the full-bridge rectifier circuit is used to provide the second part of the output power.

[0013] In an optional embodiment, the full-bridge rectifier circuit includes a first rectifier diode, a second rectifier diode, a third rectifier diode and a fourth rectifier diode; the freewheeling circuit includes the third rectifier diode, the fourth rectifier diode, a first freewheeling diode and a second freewheeling diode;

[0014] Wherein, the anode of the first rectifier diode is connected to the same-name end of the first secondary winding of the resonant transformer, the cathode of the first rectifier diode is respectively connected to the cathode of the second rectifier diode and one end of the filter circuit, the other end of the filter circuit is connected to the drain of the fifth switch tube, the source of the fifth switch tube is respectively connected to the cathode of the first freewheeling diode and one end of the output circuit, and the other end of the output circuit is respectively connected to the anode of the third rectifier diode, the anode of the fourth rectifier diode, and the anode of the second freewheeling diode;

[0015] The cathode of the third rectifier diode is respectively connected to the anode of the first rectifier diode and the like-name end of the first secondary winding of the resonant transformer, the cathode of the fourth rectifier diode is respectively connected to the non-like-name end of the second secondary winding of the resonant transformer and the anode of the second rectifier diode, and the cathode of the second freewheeling diode is respectively connected to the non-like-name end of the first secondary winding of the resonant transformer, the like-name end of the second secondary winding of the resonant transformer, and the anode of the first freewheeling diode.

[0016] In an optional embodiment, during the positive half cycle,

[0017] When the fifth switch tube is in the on state, the second part of the output power is provided through the first rectifier diode and the fourth rectifier diode, and the output voltage is adjusted by adjusting the duty cycle of the fifth switch tube;

[0018] When the fifth switch tube is in the off state and the induced voltage is positive, the first part of the output power is transmitted through the first freewheeling diode and the fourth rectifier diode;

[0019] When the fifth switch tube operates in the off state and the voltage provided by the full-bridge LLC resonant circuit cannot turn on the first rectifier diode, the second rectifier diode, the third rectifier diode, the fourth rectifier diode, the first freewheeling diode, and the second freewheeling diode, the loop is completed through the output circuit.

[0020] In an optional embodiment, during the negative half cycle,

[0021] When the fifth switch tube is in the on state, the second part of the output power is provided through the second rectifier diode and the third rectifier diode, and the output voltage is adjusted by adjusting the duty cycle of the fifth switch tube;

[0022] When the fifth switch tube operates in an off state and the induced voltage is negative, a first part of the output power is transmitted through the first freewheeling diode and the second freewheeling diode;

[0023] When the fifth switch tube operates in the off state and the voltage provided by the full-bridge LLC resonant circuit cannot turn on the first rectifier diode, the second rectifier diode, the third rectifier diode, the fourth rectifier diode, the first freewheeling diode, and the second freewheeling diode, the loop is completed through the output circuit.

[0024] In an optional embodiment, the full-bridge LLC resonant circuit includes a full-bridge inverter circuit and a resonant network;

[0025] The full-bridge inverter circuit includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; the resonant network includes a resonant inductor, an excitation inductor and a resonant capacitor.

[0026] In an optional embodiment, the output voltage gain of the circuit with a wide voltage adjustment range is calculated by the following formula:

[0027] (n2+n3)*(1+D) / 2*n1;

[0028] Among them, n1 represents the number of turns of the primary winding of the resonant transformer, n2 represents the number of turns of the first secondary winding of the resonant transformer, n3 represents the number of turns of the second secondary winding of the resonant transformer, and D represents the duty cycle of the fifth switch tube.

[0029] Compared with the prior art, the embodiment of the present invention provides a power supply system with a wide voltage adjustment range. By making the full-bridge LLC resonant circuit operate at a fixed frequency and a preset dead time, zero voltage switching of the switch tube is realized, thereby improving the efficiency of the circuit; at the same time, most of the output power of the secondary side of the transformer is delivered to the load through the freewheeling circuit composed of the secondary side diodes, and the remaining small part of the output power is provided at a relatively low efficiency through the full-bridge BUCK circuit and the output voltage is adjusted; compared with the solution of using the traditional LLC resonant circuit cascade BUCK circuit, most of the power in the embodiment of the present invention can be directly transmitted to the load through the freewheeling circuit, and the full-bridge BUCK circuit only needs to process a small part of the insufficient voltage and power, thereby realizing the shunting of the full-bridge BUCK circuit and the freewheeling circuit, so that the power supply system has high-efficiency conversion capability and an adjustable wide voltage output range. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present invention, the drawings used in the implementation mode will be briefly introduced below. Obviously, the drawings described below are only some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a circuit schematic diagram of a power supply system with a wide voltage adjustment range provided by an embodiment of the present invention;

[0032] Figure 2 It is a circuit diagram of a positive half-cycle state 1 of a power supply system with a wide voltage adjustment range provided by an embodiment of the present invention;

[0033] Figure 3 It is a circuit diagram of a positive half-cycle state 2 of a power supply system with a wide voltage adjustment range provided by an embodiment of the present invention;

[0034] Figure 4 It is a circuit diagram of a positive half-cycle state three of a power supply system with a wide voltage adjustment range provided by an embodiment of the present invention;

[0035] Figure 5 It is a circuit diagram of a negative half-cycle state 1 of a power supply system with a wide voltage adjustment range provided by an embodiment of the present invention;

[0036] Figure 6It is a circuit diagram of a negative half-cycle state 2 of a power supply system with a wide voltage adjustment range provided by an embodiment of the present invention;

[0037] Figure 7 It is a circuit diagram of negative half-cycle state three of a power supply system with a wide voltage adjustment range provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] It should be noted that when an element is referred to as being "connected to" another element, it can be directly connected to another element or indirectly connected to the other element. It is understandable that the "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if the connected circuits, modules, units, etc. have the transmission of electrical signals or data to each other. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. "At least one" means one or more, and "multiple" means two or more.

[0040] See also Figure 1 , Figure 1 FIG. 1 is a circuit diagram of a power supply system with a wide voltage adjustment range provided by an embodiment of the present invention. Figure 1 As shown, the power supply system with a wide voltage adjustment range includes a circuit with a wide voltage adjustment range, and the circuit with a wide voltage adjustment range includes a full-bridge LLC resonant circuit, a resonant transformer, a full-bridge BUCK circuit and a freewheeling circuit;

[0041] The full-bridge LLC resonant circuit is connected to the full-bridge BUCK circuit and the freewheeling circuit through the resonant transformer, and the freewheeling circuit is connected to the full-bridge BUCK circuit by sharing at least two diodes;

[0042] The full-bridge LLC resonant circuit is used to operate at a fixed resonant frequency and a preset dead time to achieve zero voltage switching of the switch tube in the full-bridge LLC resonant circuit; the freewheeling circuit is used to transmit the first part of the output power; the full-bridge BUCK circuit is used to adjust the output voltage and provide the second part of the output power; wherein the first part of the output power is greater than the second part of the output power.

[0043] Exemplarily, the circuit with a wide voltage adjustment range includes a full-bridge LLC resonant circuit at the front stage of the resonant transformer, and the rear stage of the transformer is divided into a two-phase circuit, one phase of which is a freewheeling circuit and the other phase is a full-bridge BUCK circuit. The full-bridge LLC circuit at the front stage operates at the resonant frequency and the preset dead time to achieve ZVS (zero voltage switching) of its switch tube. The full-bridge BUCK circuit is used to adjust the output voltage. At the same time, most of the output power is delivered to the load through the freewheeling circuit. The non-regulated output voltage should be lower than the required output voltage, so the full-bridge BUCK circuit is also used to provide the remaining output power at a relatively low efficiency. The embodiment of the present invention divides the power between the full-bridge BUCK circuit and the freewheeling circuit, so that the power supply system shows a high-efficiency conversion capability, which can not only achieve a wide voltage output, but also improve the overall efficiency of the power supply system.

[0044] like Figure 1 As shown, in an optional embodiment, the full-bridge LLC resonant circuit includes a full-bridge inverter circuit and a resonant network; the full-bridge inverter circuit includes a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, and a fourth switch tube Q4; the resonant network includes a resonant inductor Lr, an excitation inductor Lm, and a resonant capacitor Cr;

[0045] Among them, the drain of the first switch tube Q1 and the drain of the third switch tube Q3 are respectively connected to the positive end of the input power supply voltage, the source of the first switch tube Q1 and the drain of the second switch tube Q2 are respectively connected to the first end of the resonant inductor Lr, the second end of the resonant inductor Lr is connected to the first end of the excitation inductor Lm and the same-name end of the primary winding n1 of the resonant transformer, the second end of the excitation inductor Lm is respectively connected to the non-same-name end of the primary winding of the resonant transformer and the first end of the resonant capacitor Cr, the second end of the resonant capacitor Cr is respectively connected to the source of the third switch tube Q3 and the drain of the fourth switch tube Q4, the source of the fourth switch tube Q4 and the source of the second switch tube Q2 are respectively connected to the negative end of the input power supply voltage.

[0046] It should be noted that in the full-bridge LLC resonant circuit, the full-bridge inverter circuit is composed of four power switching tubes (such as MOSFET or IGBT) to form an H-bridge structure. The four switching tubes are turned on and off according to a certain timing to generate a high-frequency square wave voltage. Generally, pulse width modulation (PWM) or pulse frequency modulation (PFM) control methods are used to adjust the output voltage.

[0047] The LLC resonant network consists of a resonant inductor Lr, a magnetizing inductor Lm, and a resonant capacitor Cr. The magnetizing inductor Lm is related to the magnetizing inductor of the transformer. These three components form a resonant circuit and determine the resonant characteristics of the circuit. When a high-frequency square wave voltage is applied to the LLC resonant network, the resonant inductor Lr, the magnetizing inductor Lm, and the resonant capacitor Cr resonate. During the resonance process, the waveforms of the current and voltage will show a specific change pattern. When the switching frequency is equal to the resonant frequency, the circuit resonates. At this time, the phase relationship between the current and the voltage enables the switch tube to achieve zero voltage switching (ZVS) or zero current switching (ZCS), thereby reducing switching losses.

[0048] like Figure 1 As shown, in an optional embodiment, the full-bridge BUCK circuit includes a full-bridge rectifier circuit, a fifth switch tube Q5, a filter circuit and an output circuit;

[0049] One end of the full-bridge rectifier circuit is connected to one end of the filter circuit, the other end of the filter circuit is connected to the drain of the fifth switch tube, the source of the fifth switch tube Q5 is connected to one end of the output circuit, and the other end of the output circuit is respectively connected to the other end of the full-bridge rectifier circuit and one end of the freewheeling circuit.

[0050] It should be noted that the full-bridge BUCK circuit is used to adjust the duty cycle of the fifth switch tube Q5 to adjust the output voltage, and the full-bridge rectifier circuit is used to provide the second part of the output power.

[0051] Further, the freewheeling circuit includes at least one freewheeling diode;

[0052] The freewheeling circuit is used to cooperate with the full-bridge BUCK circuit to deliver the first part of the output power when the fifth switch tube Q5 is turned off.

[0053] It is worth noting that in the entire power supply system, the freewheeling circuit and the full-bridge BUCK circuit have a close synergistic relationship. When the fifth switch tube is turned off, the current direction in the circuit will change. At this time, the freewheeling circuit will intervene in time to allow the current to continue to flow, thereby stably transmitting the first part of the output power. This not only avoids the interruption of power transmission, but also maintains the stability of the current of the entire system, greatly enhances the stability of the system operation, and ensures that the load can work normally when the switch tube state is switched. The full-bridge BUCK circuit is the core part of adjusting the output voltage. It mainly adjusts the duty cycle of the fifth switch tube to achieve precise control of the output voltage. In actual operation, with the fluctuation of the input voltage and the change of load demand, the full-bridge BUCK circuit can respond quickly and flexibly change the on-time and off-time ratio of the fifth switch tube, thereby stabilizing the output voltage at the set value, meeting the strict requirements for voltage stability in different power usage scenarios. Specifically, the full-bridge rectifier circuit is responsible for providing the second part of the output power. In the process of converting AC to DC, the full-bridge rectifier circuit uses its own bridge structure to efficiently and stably convert AC into DC, and smoothly incorporates this part of the power into the entire power output system, cooperating with the first part of the power transmitted by the freewheeling circuit to provide sufficient and stable power supply for the load and ensure the normal operation of various equipment.

[0054] In an alternative embodiment, Figure 1 As shown, the full-bridge rectifier circuit includes a first rectifier diode D1, a second rectifier diode D2, a third rectifier diode D3 and a fourth rectifier diode D4, the output circuit includes an output inductor L2, an output capacitor C2 and an output resistor R, and the filter circuit includes a filter capacitor C1 and a filter inductor L1;

[0055] It is worth noting that the output circuit can effectively suppress the sudden change of current, making the output current smoother and more stable. When the current fluctuates, it will generate a reverse electromotive force, hindering the rapid change of current, thereby providing a relatively stable current source for the subsequent load. The output capacitor C2 is mainly used to further smooth the output voltage, store and release charges, compensate for the instantaneous change of current, reduce the voltage ripple, and ensure the stability of the output voltage. The output resistor R, as the equivalent resistance of the load, cooperates with the output inductor L2 and the output capacitor C2 to jointly determine the working state and load characteristics of the output circuit, directly affecting the size and efficiency of the output power. The function of the filter capacitor C1 is to bypass high-frequency clutter signals, short-circuit the high-frequency noise in the circuit to the ground, make the output electric energy purer, and reduce the impact of high-frequency interference on the entire system. The filter inductor L1 is mainly used to block high-frequency current, allow low-frequency signals to pass, and further enhance the filtering effect of high-frequency clutter. It forms a low-pass filter with the filter capacitor C1, which effectively suppresses the high-frequency components in the input signal, so that the filtered electric energy can be transmitted to the output circuit with lower noise and interference levels, providing a solid guarantee for the stable operation of the entire system.

[0056] Specifically, the freewheeling circuit includes the third rectifier diode D3, the fourth rectifier diode D4, the first freewheeling diode D5 and the second freewheeling diode D6;

[0057] Wherein, the anode of the first rectifier diode D1 is connected to the same-name end of the first secondary winding n2 of the resonant transformer, the cathode of the first rectifier diode D1 is respectively connected to the cathode of the second rectifier diode D2 and the first end of the filter inductor L1, the second end of the filter inductor L1 is respectively connected to the first end of the filter capacitor C1 and the drain of the fifth switch tube Q5, the source of the fifth switch tube Q5 is respectively connected to the cathode of the first freewheeling diode D5 and the first end of the output inductor L2, the second end of the output inductor L2 is respectively connected to the first end of the output capacitor C2 and the first end of the output resistor R, the second end of the output capacitor C2 and the second end of the output resistor R are respectively connected to the anode of the third rectifier diode D3, the anode of the fourth rectifier diode D4, and the anode of the second freewheeling diode D6;

[0058] The cathode of the third rectifier diode D3 is respectively connected to the anode of the first rectifier diode D1 and the like-name end of the first secondary winding of the resonant transformer, the cathode of the fourth rectifier diode D4 is respectively connected to the non-like-name end of the second secondary winding of the resonant transformer and the anode of the second rectifier diode D2, and the cathode of the second freewheeling diode D6 is respectively connected to the non-like-name end of the first secondary winding of the resonant transformer, the like-name end of the second secondary winding n3 of the resonant transformer, and the anode of the first freewheeling diode D5.

[0059] It is worth noting that the freewheeling circuit can ensure that the circuit maintains the continuous flow of current at a specific stage, thereby ensuring the stable operation of the entire system. Specifically, the diodes in the freewheeling circuit perform their respective duties and cooperate with each other to provide strong support for the stable operation of the circuit. The third rectifier diode D3 and the fourth rectifier diode D4 undertake the key task of rectification in the freewheeling circuit. In the conduction phase of the circuit, they can accurately convert alternating current into direct current so that the current flows in a predetermined direction. This not only ensures the effective transmission of electric energy, but also avoids the damage that the reverse flow of current may cause to the circuit. The first freewheeling diode D5 and the second freewheeling diode D6 are mainly responsible for providing a freewheeling path for energy storage elements such as inductors when the switch element is turned off. When the switch element (such as the fifth switch tube) in the circuit is switched from the on state to the off state, the energy stored in the inductor needs to be released, otherwise an excessively high voltage spike will be generated, which may damage the circuit elements. At this time, the first freewheeling diode D5 and the second freewheeling diode D6 will be turned on in time to form a freewheeling loop, so that the current in the inductor can continue to flow and slowly release the stored energy. In this way, the impact of voltage spikes on the circuit is avoided, the continuity of the current is guaranteed, electromagnetic interference is reduced, and the stability and reliability of the circuit are improved. In addition, the freewheeling circuit composed of these four diodes also has the advantage of fast response speed. At the moment when the state of the switching element changes, they can respond quickly and adjust the conduction state of the circuit in time to ensure the smooth progress of the freewheeling process. Moreover, the structure of this freewheeling circuit is relatively simple, the cost is low, it is easy to implement and maintain, and it has high practicality and economy. By reasonably selecting the parameters of the diode, the performance of the freewheeling circuit can also be optimized according to different circuit requirements, further improving the performance and stability of the entire circuit system.

[0060] Exemplarily, an embodiment of the present invention provides a power supply system with a wide voltage adjustment range. When working, after the input voltage is sent to the full-bridge LLC resonant circuit of the front stage, the duty cycle of the first switch tube Q1 and the third switch tube Q3 can be controlled to be 50% and unchanged, and the dead time is set to enter the resonant network; Exemplarily, the dead time is set to 5% of the cycle of the first switch tube Q1. Then, the duty cycle of the fifth switch tube Q5 in the full-bridge BUCK circuit of the rear stage is adjusted to adapt to the change of the input voltage, thereby adjusting the output voltage to make the output voltage stable. Exemplarily, a voltage closed loop is used to adjust the duty cycle of the fifth switch tube Q5 in the full-bridge BUCK circuit of the rear stage.

[0061] like Figures 2 to 4 As shown, when the power supply system is working, in the positive half cycle, the two diagonal switch tubes (such as the first switch tube Q1 and the fourth switch tube Q4) in the full-bridge LLC resonant circuit are turned on, and the other two switch tubes (the second switch tube Q2 and the third switch tube Q3) are turned off, and the input power is supplied to the resonant network through the turned-on switch tubes. The current starts from the positive electrode of the power supply, passes through the first switch tube Q1, the resonant inductor Lr, the excitation inductor Lm and the resonant capacitor Cr, the primary winding of the resonant transformer, and the fourth switch tube Q4, and returns to the negative electrode of the power supply.

[0062] There are three working states in the positive half cycle, the states are as follows Figure 2 As shown, when the fifth switch tube is in the on state, the voltage of the same-name terminal of n2 is V*(n2+n3) / n1. At this time, the same-name terminal of n2 completes the loop through the first rectifier diode D1, the filter inductor L1, the fifth switch tube Q5, the output inductor L2, the output resistor R, the output capacitor C2 and the fourth rectifier diode D4 in sequence. At this time, the circuit provides the second part of the output power (a small part of the output power) through the first rectifier diode D1 and the fourth rectifier diode D4 with relatively low efficiency and adjusts the output voltage by adjusting the duty cycle of the fifth switch tube Q5.

[0063] Positive half cycle state Figure 3 As shown, when the fifth switch tube Q5 is in the off state and the induced voltage is positive, the voltage at the same-name end of n3 is V*n3 / n1. At this time, the same-name end of n3 completes the loop through the first freewheeling diode D5, the output inductor L2, the output resistor R, the output capacitor C2 and the fourth rectifier diode D4. At this time, the first part of the output power of the circuit (most of the output power) is transmitted to the load through the first freewheeling diode D5 and the fourth rectifier diode D4 with relatively high efficiency.

[0064] Positive half cycle state three Figure 4As shown, when the fifth switch tube Q5 is operating in the off state, and the voltage provided by the full-bridge LLC resonant circuit cannot turn on the first rectifier diode D1, the second rectifier diode D2, the third rectifier diode D3 and the fourth rectifier diode D4, the first freewheeling diode D5, and the second freewheeling diode D6, that is, when the primary side of the transformer cannot provide energy, the circuit is provided with energy by the output inductor L2 and the output capacitor C, and the output resistor R consumes energy to complete the loop.

[0065] Similarly, if Figures 5 to 7 As shown, when the power supply system is working, in the negative half cycle, opposite to the positive half cycle, the second switch tube Q2 and the third switch tube Q3 at the diagonal of the full-bridge LLC resonant circuit are turned on, and the first switch tube Q1 and the fourth switch tube Q4 are turned off. At this time, the current starts from the positive electrode of the power supply, passes through the third switch tube Q3, the resonant inductor Lr, the excitation inductor Lm and the resonant capacitor Cr, the primary winding of the resonant transformer, and the second switch tube Q2 to return to the negative electrode of the power supply.

[0066] There are three working states in the negative half cycle. The negative half cycle states are as follows: Figure 5 As shown, when the fifth switch tube Q5 is in the on state, the non-same-name end of n3 completes the loop through the second rectifier diode D2, the filter inductor L1, the fifth switch tube Q5, the output inductor L2, the output resistor R, the output capacitor C2 and the third rectifier diode D3. At this time, the circuit provides the second part of the output power through the second rectifier diode D2 and the third rectifier diode D3 with relatively low efficiency, and adjusts the output voltage by adjusting the duty cycle of the fifth switch tube Q5.

[0067] Negative half cycle state Figure 6 As shown, when the fifth switch tube Q5 is in the off state and the induced voltage is negative, the voltage of the non-same-name terminal of n2 is V*n2 / n1. At this time, the non-same-name terminal of n2 completes the loop through the first freewheeling diode D5, the output inductor L2, the output resistor R, the output capacitor C2 and the third rectifier diode D3. At this time, the first part of the output power of the circuit (most of the power) is transmitted to the load through the first freewheeling diode D5 and the second freewheeling diode D6 with relatively high efficiency.

[0068] Negative half cycle state three Figure 7 As shown, when the fifth switch tube Q5 is operating in the off state, and the voltage provided by the full-bridge LLC resonant circuit cannot turn on the first rectifier diode D1, the second rectifier diode D2, the third rectifier diode D3 and the fourth rectifier diode D4, the first freewheeling diode D5, and the second freewheeling diode D6, that is, when the primary side of the transformer cannot provide energy, the circuit is provided with energy by the output inductor L2 and the output capacitor C, and the output resistor R consumes energy to complete the loop.

[0069] Therefore, in one switching cycle of the circuit with a wide voltage adjustment range, according to the volt-second balance principle of the output inductor L2, the output voltage gain of the circuit can be obtained as:

[0070] (n2+n3)*(1+D) / 2*n1;

[0071] Among them, n1 represents the number of turns of the primary winding of the resonant transformer, n2 represents the number of turns of the first secondary winding of the resonant transformer, n3 represents the number of turns of the second secondary winding of the resonant transformer, and D represents the duty cycle of the fifth switch tube Q5.

[0072] In summary, the embodiment of the present invention provides a power supply system with a wide voltage adjustment range, which realizes ZVS of the switch tube Q1-4 by making the full-bridge LLC resonant circuit work at a fixed frequency, thereby improving the efficiency of the circuit; at the same time, most of the output power of the secondary side of the transformer is delivered to the load through the freewheeling circuit composed of the secondary diodes D3-D6, and the non-adjusted output voltage should be lower than the required output voltage, so the remaining output power is provided by D1-D4 in the full-bridge BUCK circuit with relatively low efficiency and the output voltage is adjusted; compared with the solution of using the traditional LLC resonant circuit cascade BUCK circuit, most of the power in the embodiment of the present invention is directly transmitted to the load through the freewheeling circuit, and the full-bridge BUCK circuit only needs to process a small part of the insufficient voltage and power, realizing the shunting of the full-bridge BUCK circuit and the freewheeling circuit, so that the power supply system has high-efficiency conversion capability and an adjustable wide voltage output range. In addition, the circuit structure of the embodiment of the present invention is simple, the design adjustment is flexible, the control method is simple, and it has strong practicality. It can be used in power supply systems that require wide input, such as new energy, computers, and automobiles, thereby effectively improving the power density and overall efficiency of the power supply system.

[0073] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A power supply system with a wide voltage adjustment range, characterized in that: The invention comprises a circuit with a wide voltage adjustment range, wherein the circuit with a wide voltage adjustment range comprises a full-bridge LLC resonant circuit, a resonant transformer, a full-bridge BUCK circuit and a freewheeling circuit; The full-bridge LLC resonant circuit is connected to the full-bridge BUCK circuit and the freewheeling circuit through the resonant transformer, and the freewheeling circuit is connected to the full-bridge BUCK circuit by sharing at least two diodes; The full-bridge LLC resonant circuit is used to operate at a fixed resonant frequency and a preset dead time to achieve zero voltage switching of the switch tube in the full-bridge LLC resonant circuit; the freewheeling circuit is used to transmit the first part of the output power; the full-bridge BUCK circuit is used to adjust the output voltage and provide the second part of the output power; wherein the first part of the output power is greater than the second part of the output power.

2. The power supply system with a wide voltage adjustment range as claimed in claim 1, characterized in that: The full-bridge BUCK circuit includes a full-bridge rectifier circuit, a fifth switch tube, a filter circuit and an output circuit; One end of the full-bridge rectifier circuit is connected to one end of the filter circuit, the other end of the filter circuit is connected to the source of the fifth switch tube, the drain of the fifth switch tube is connected to one end of the output circuit, and the other end of the output circuit is respectively connected to the other end of the full-bridge rectifier circuit and one end of the freewheeling circuit.

3. The power supply system with a wide voltage adjustment range as claimed in claim 2, characterized in that: The freewheeling circuit comprises at least one freewheeling diode; The freewheeling circuit is used to cooperate with the full-bridge BUCK circuit to deliver the first part of the output power when the fifth switch tube is turned off.

4. The power supply system with a wide voltage adjustment range as claimed in claim 3, characterized in that: The full-bridge BUCK circuit is used to adjust the duty cycle of the fifth switch tube to adjust the output voltage, and the full-bridge rectifier circuit is used to provide the second part of the output power.

5. The power supply system with a wide voltage adjustment range as claimed in claim 3, characterized in that: The full-bridge rectifier circuit includes a first rectifier diode, a second rectifier diode, a third rectifier diode and a fourth rectifier diode; the freewheeling circuit includes the third rectifier diode, the fourth rectifier diode, a first freewheeling diode and a second freewheeling diode; Wherein, the anode of the first rectifier diode is connected to the same-name end of the first secondary winding of the resonant transformer, the cathode of the first rectifier diode is respectively connected to the cathode of the second rectifier diode and one end of the filter circuit, the other end of the filter circuit is connected to the drain of the fifth switch tube, the source of the fifth switch tube is respectively connected to the cathode of the first freewheeling diode and one end of the output circuit, and the other end of the output circuit is respectively connected to the anode of the third rectifier diode, the anode of the fourth rectifier diode, and the anode of the second freewheeling diode; The cathode of the third rectifier diode is respectively connected to the anode of the first rectifier diode and the like-name end of the first secondary winding of the resonant transformer, the cathode of the fourth rectifier diode is respectively connected to the non-like-name end of the second secondary winding of the resonant transformer and the anode of the second rectifier diode, and the cathode of the second freewheeling diode is respectively connected to the non-like-name end of the first secondary winding of the resonant transformer, the like-name end of the second secondary winding of the resonant transformer, and the anode of the first freewheeling diode.

6. The power supply system with a wide voltage adjustment range as claimed in claim 5, characterized in that: In the positive half cycle, When the fifth switch tube is in the on state, the second part of the output power is provided through the first rectifier diode and the fourth rectifier diode, and the output voltage is adjusted by adjusting the duty cycle of the fifth switch tube; When the fifth switch tube is in the off state and the induced voltage is positive, the first part of the output power is transmitted through the first freewheeling diode and the fourth rectifier diode; When the fifth switch tube operates in the off state and the voltage provided by the full-bridge LLC resonant circuit cannot turn on the first rectifier diode, the second rectifier diode, the third rectifier diode, the fourth rectifier diode, the first freewheeling diode, and the second freewheeling diode, the loop is completed through the output circuit.

7. The power supply system with a wide voltage adjustment range as claimed in claim 6, characterized in that: In the negative half cycle, When the fifth switch tube is in the on state, the second part of the output power is provided through the second rectifier diode and the third rectifier diode, and the output voltage is adjusted by adjusting the duty cycle of the fifth switch tube; When the fifth switch tube operates in an off state and the induced voltage is negative, a first part of the output power is transmitted through the first freewheeling diode and the second freewheeling diode; When the fifth switch tube operates in the off state and the voltage provided by the full-bridge LLC resonant circuit cannot turn on the first rectifier diode, the second rectifier diode, the third rectifier diode, the fourth rectifier diode, the first freewheeling diode, and the second freewheeling diode, the loop is completed through the output circuit.

8. The power supply system with a wide voltage adjustment range according to any one of claims 1, characterized in that: The full-bridge LLC resonant circuit includes a full-bridge inverter circuit and a resonant network; The full-bridge inverter circuit includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; the resonant network includes a resonant inductor, an excitation inductor and a resonant capacitor.

9. The power supply system with a wide voltage adjustment range as claimed in claim 2, characterized in that: The output circuit includes an output inductor, an output capacitor and an output resistor, and the filter circuit includes a filter capacitor and a filter inductor.

10. The power supply system with a wide voltage adjustment range according to any one of claims 2 to 9, characterized in that: The output voltage gain of the circuit with a wide voltage adjustment range is calculated by the following formula: (n2+n3)*(1+D) / 2*n1; Among them, n1 represents the number of turns of the primary winding of the resonant transformer, n2 represents the number of turns of the first secondary winding of the resonant transformer, n3 represents the number of turns of the second secondary winding of the resonant transformer, and D represents the duty cycle of the fifth switch tube.

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