A control method of a synchronous rectifier converter with wide voltage regulation capability

Abstract

The application discloses a synchronous rectification converter control method with wide voltage regulation capability, comprising the following steps: obtaining a voltage signal at both ends of a load, and then controlling the frequency of a first primary switch, a second primary switch, a third primary switch and a fourth primary switch according to the voltage signal at both ends of the load, and meanwhile, the output voltage gain of the converter is controlled by controlling the leading conduction angle or the lagging turn-off angle of a first secondary switch, a second secondary switch, a third secondary switch and a fourth secondary switch, so that the output voltage gain of the LLC converter can be further improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronic converters, and relates to a synchronous rectification converter control method with wide voltage regulation capability. BACKGROUND

[0002] In the current era of rapid development of electric energy conversion devices, higher efficiency, power density and other characteristics have become the main direction of the development of switching converters. In a series of small and medium power DC-DC converter occasions such as adapter power supply, vehicle-mounted power supply, lighting power supply, LLC converter is widely used in such switching power supplies due to its good soft switching characteristics. However, since the traditional LLC converter needs to adjust the switching frequency to change the output voltage gain, the wide range of switching frequency adjustment has become a disadvantage of LLC converter.

[0003] In the current technical development, some methods for improving the output voltage gain of LLC converter topology reconstruction or adding resonant elements to change the gain characteristics have been produced, but such technologies need to add additional components and require complex control methods. Therefore, without changing the traditional LLC converter circuit topology and parameter design, how to further improve the output voltage gain of the converter has become the focus and difficulty of current research. SUMMARY

[0004] The purpose of the application is to overcome the shortcomings of the prior art, and provide a synchronous rectification converter control method with wide voltage regulation capability, which can further improve the output voltage gain of LLC converter.

[0005] To achieve the above purpose, the synchronous rectification converter control method with wide voltage regulation capability comprises the following steps:

[0006] The voltage signal across the load is obtained, and the frequency of the primary side first switch, the primary side second switch, the primary side third switch and the primary side fourth switch is controlled according to the voltage signal across the load, and the leading conduction angle of the secondary side first switch, the secondary side second switch, the secondary side third switch and the secondary side fourth switch is controlled or the lagging turn-off angle The output voltage gain of the converter is controlled.

[0007] The converter comprises a DC power supply, a first inductor, a second inductor, a third inductor, a transformer, a filter capacitor, an input capacitor, a load, a controller, a primary side first switch, a primary side second switch, a primary side third switch, a primary side fourth switch, a secondary side first switch, a secondary side second switch, a secondary side third switch and a secondary side fourth switch.

[0008] The positive pole of the direct current power supply is connected with one end of the input capacitor, one end of the primary side first switch and one end of the primary side second switch, the negative pole of the direct current power supply is connected with the other end of the input capacitor, one end of the primary side third switch and one end of the primary side fourth switch, the other end of the primary side first switch, the other end of the primary side third switch and one end of the first inductor are connected, the other end of the primary side second switch, the other end of the primary side fourth switch and one end of the second inductor are connected, the other end of the first inductor is connected with one end of the primary side winding in the transformer and one end of the third inductor, the other end of the second inductor is connected with the other end of the primary side winding in the transformer and the other end of the third inductor;

[0009] One end of the secondary side winding in the transformer is connected with one end of the secondary side first switch and one end of the secondary side third switch, the other end of the secondary side winding in the transformer is connected with one end of the secondary side second switch and one end of the secondary side fourth switch, the other end of the secondary side first switch, the other end of the secondary side second switch, one end of the filter capacitor and one end of the load are connected, the other end of the secondary side third switch, the other end of the secondary side fourth switch, the other end of the filter capacitor and the other end of the load are connected;

[0010] The controller is connected with the control end of the primary side first switch, the control end of the primary side second switch, the control end of the primary side third switch, the control end of the primary side fourth switch, the control end of the secondary side first switch, the control end of the secondary side second switch, the control end of the secondary side third switch and the control end of the secondary side fourth switch.

[0011] When it is needed to improve the output voltage gain, the frequency of the primary side first switch, the primary side second switch, the primary side third switch, the primary side fourth switch, the secondary side first switch, the secondary side second switch, the secondary side third switch and the secondary side fourth switch is reduced.

[0012] The minimum frequency fsmin is set, when the pulse frequency modulation reaches fsmin and it is needed to be further reduced, the frequency of the primary side first switch, the primary side second switch, the primary side third switch, the primary side fourth switch, the secondary side first switch, the secondary side second switch, the secondary side third switch and the secondary side fourth switch is fixed as fsmin, at the same time, the secondary side first switch, the secondary side second switch, the secondary side third switch and the secondary side fourth switch are turned on in advance, the advance turn-on angle is increased to improve the output voltage gain; when the primary side second switch and the primary side third switch are turned on, the resonant current is equal to the excitation inductance current, that is, the circuit enters the O mode, through the circuit parameter design, it is ensured that during the O mode, the voltage across the secondary side first switch and the secondary side fourth switch is oscillated, when the voltage across the secondary side first switch and the secondary side fourth switch is the oscillation valley value, even the serious oscillation occurs and the oscillation valley value voltage is zero, the secondary side first switch and the secondary side fourth switch are turned on, the switch loss is reduced or the zero voltage turn-on soft switch is realized;

[0013] When the primary side first switch and the primary side fourth switch are turned on, the resonant current is equal to the excitation inductance current, and the circuit enters the O mode, through the circuit parameter design, the voltage at the two ends of the secondary side second switch and the secondary side third switch is oscillated during the O mode, when the voltage at the two ends of the secondary side second switch and the secondary side third switch is the oscillation valley value, or even the oscillation valley value voltage is zero, the secondary side second switch and the secondary side third switch are turned on, and the switching loss is reduced or the zero voltage turn-on soft switch is realized.

[0014] The maximum frequency fsmax is set, when the pulse frequency modulation reaches fsmax and needs to be further increased, the frequencies of the primary side first switch, the primary side second switch, the primary side third switch, the primary side fourth switch, the secondary side first switch, the secondary side second switch, the secondary side third switch and the secondary side fourth switch are fixed as a preset value less than the resonant frequency, and the secondary side first switch, the secondary side second switch, the secondary side third switch and the secondary side fourth switch are hysteresis turned off, and the hysteresis turn-off angle is increased to reduce the output voltage gain;

[0015] When the primary side second switch and the primary side third switch are turned on, the resonant current is equal to the excitation inductance current, that is, the circuit enters the O mode, then the secondary side second switch and the secondary side third switch are kept turned on, and then the secondary side second switch and the third switch are turned off, when the primary side first switch and the primary side fourth switch are turned on, the resonant current is equal to the excitation inductance current, that is, the circuit enters the O mode, then the secondary side first switch and the secondary side fourth switch are kept turned on, and then the secondary side second switch and the secondary side third switch are turned off.

[0016] The primary side first switch, the primary side second switch, the primary side third switch, the primary side fourth switch, the secondary side first switch, the secondary side second switch, the secondary side third switch and the secondary side fourth switch are wide band gap semiconductor devices, field effect tubes or crystal triodes.

[0017] The conversion is an LLC converter or an LCC converter.

[0018] The present application has the following beneficial effects:

[0019] The synchronous rectifier control method with wide voltage regulation capability in the specific operation controls the frequency of the primary side first switch, the primary side second switch, the primary side third switch and the primary side fourth switch according to the voltage signal at the two ends of the load, and controls the advance turn-on angle or the hysteresis turn-off angle of the secondary side first switch, the secondary side second switch, the secondary side third switch and the secondary side fourth switch, so that the output voltage gain of the converter is controlled, the output voltage gain of the LLC converter is greatly improved, the switching frequency range of the LLC converter is reduced, the parameter design of the LLC converter is facilitated, high efficiency, high power density and wide input and output voltage regulation capability are realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the structural diagram of LLC converter;

[0021] Figure 2a Schematic diagram of the synchronous control strategy for the traditional LLC converter;

[0022] Figure 2b This is a schematic diagram of the LLC converter early turn-on synchronous finishing control strategy proposed by the present invention;

[0023] Figure 2c Schematic diagram of the LLC converter hysteresis shutdown synchronous finishing control strategy proposed by the present invention;

[0024] Figure 3 Schematic diagram of drain-source voltage waveforms during the O mode period of the secondary-side first switch, the secondary-side second switch, the secondary-side third switch, and the secondary-side fourth switch under specific parameter designs of the present invention;

[0025] Figure 4 The figure is a comparison diagram of the output voltage gain under the control method of the present invention and the traditional LLC synchronous rectifier. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0027] The accompanying drawings illustrate schematic diagrams of the structures of the disclosed embodiments of the present invention. These figures are not drawn to scale; for the purpose of clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0028] refer to Figure 1The LLC converter comprises a DC power supply, a first inductor, a second inductor, a third inductor, a transformer, a filter capacitor, an input capacitor, a load, a controller, a primary first switch, a primary second switch, a primary third switch, a primary fourth switch, a secondary first switch, a secondary second switch, a secondary third switch and a secondary fourth switch.

[0029] The positive pole of the DC power supply is connected with one end of the input capacitor, one end of the primary first switch and one end of the primary second switch, the negative pole of the DC power supply is connected with the other end of the input capacitor, one end of the primary third switch and one end of the primary fourth switch, the other end of the primary first switch, the other end of the primary third switch and one end of the first inductor are connected, the other end of the primary second switch, the other end of the primary fourth switch and one end of the second inductor are connected, the other end of the first inductor is connected with one end of the primary winding of the transformer and one end of the third inductor, the other end of the second inductor is connected with the other end of the primary winding of the transformer and the other end of the third inductor.

[0030] One end of the secondary winding of the transformer is connected with one end of the secondary first switch and one end of the secondary third switch, the other end of the secondary winding of the transformer is connected with one end of the secondary second switch and one end of the secondary fourth switch, the other end of the secondary first switch, the other end of the secondary second switch, one end of the filter capacitor and one end of the load are connected, the other end of the secondary third switch, the other end of the secondary fourth switch, the other end of the filter capacitor and the other end of the load are connected.

[0031] The controller is connected with the control end of the primary first switch, the control end of the primary second switch, the control end of the primary third switch, the control end of the primary fourth switch, the control end of the secondary first switch, the control end of the secondary second switch, the control end of the secondary third switch and the control end of the secondary fourth switch.

[0032] The method for controlling the synchronous rectifier converter with wide voltage regulation capability comprises the following steps: the controller acquires a voltage signal between the load, and controls the frequency of the primary first switch, the primary second switch, the primary third switch and the primary fourth switch according to the voltage signal between the load, and controls the leading conduction angle of the secondary first switch, the secondary second switch, the secondary third switch and the secondary fourth switch or the lagging turn-off angle to control the output voltage gain of the LLC converter.

[0033] Embodiment one

[0034] Figure 1 For the circuit diagram of the LLC DC-DC converter, in the application, the switching frequency is always lower than the series resonance frequency, and the converter works in the OPO mode, the PO mode, the PON mode and other modes containing the O mode.Figure 1 The synchronous rectification control method proposed in the patent is applicable to synchronous rectification LLC or LCC converters of various structures.

[0035] The application collects the voltage signal at the load end as feedback, and controls the frequency of the primary first switch, the primary second switch, the primary third switch, the primary fourth switch, the secondary first switch, the secondary second switch, the secondary third switch and the secondary fourth switch. When a higher output voltage gain is needed, the frequency of the primary first switch, the primary second switch, the primary third switch, the primary fourth switch, the secondary first switch, the secondary second switch, the secondary third switch and the secondary fourth switch is reduced to achieve a high output voltage gain. To reduce the switching frequency range, a minimum frequency fsmin smaller than the resonant frequency and a maximum frequency fsmax larger than the resonant frequency are set.

[0036] The synchronous rectifier control method comprises the following steps:

[0037] When the conventional pulse frequency modulation reaches fsmin and needs to be further reduced, the frequency of the primary first switch, the primary second switch, the primary third switch, the primary fourth switch, the secondary first switch, the secondary second switch, the secondary third switch and the secondary fourth switch is fixed at fsmin, and the secondary first switch, the secondary second switch, the secondary third switch and the secondary fourth switch are turned on in advance, so that the advance conduction angle is increased The output voltage gain is improved. When the primary second switch and the primary third switch are turned on, the resonant current is equal to the excitation inductance current, i.e. the circuit enters the O mode, through circuit parameter design, the voltage across the secondary first switch and the secondary fourth switch is oscillated to zero during the O mode, the voltage across the secondary first switch and the secondary fourth switch is detected, and when the voltage across the secondary first switch and the secondary fourth switch is zero, the secondary first switch and the secondary fourth switch are turned on, realizing zero voltage conduction soft switch. When the primary first switch and the primary fourth switch are turned on, the resonant current is equal to the excitation inductance current, i.e. the circuit enters the O mode, through circuit parameter design, the voltage across the secondary second switch and the secondary third switch is oscillated to zero during the O mode, the voltage across the secondary second switch and the secondary third switch is detected, and when the voltage across the secondary second switch and the secondary third switch is zero, the secondary second switch and the secondary third switch are turned on, realizing zero voltage conduction soft switch.

[0038] When the traditional pulse frequency modulation reaches fsmax and needs to be further increased, the frequencies of the primary first switch, the primary second switch, the primary third switch, the primary fourth switch, the secondary first switch, the secondary second switch, the secondary third switch and the secondary fourth switch are fixed as a preset value less than the resonance frequency, and all the synchronous rectification switch tubes are made to lag behind in being turned off, so as to increase the lagging-off angle When the primary second switch and the primary third switch are turned on, the resonance current is equal to the excitation inductance current, i.e. the circuit enters the O mode, the secondary second switch and the secondary third switch are kept on, and then the secondary second switch and the secondary third switch are turned off. When the primary first switch and the primary fourth switch are turned on, the resonance current is equal to the excitation inductance current, i.e. the circuit enters the O mode, the secondary first switch and the secondary fourth switch are kept on, and then the secondary second switch and the secondary third switch are turned off.

[0039] The primary first switch, the primary second switch, the primary third switch, the primary fourth switch, the secondary first switch, the secondary second switch, the secondary third switch and the secondary fourth switch are wide-band semiconductor devices, field effect tubes or crystal triodes.

[0040] Figure 4 The output voltage gain of the traditional LLC synchronous rectification control mode and the present application under the same circuit parameters in the embodiment is shown. Figure 4 It can be seen that, under the control strategy of the synchronous rectification switch tube being turned on in advance, under the same excitation inductance and resonance inductance ratio K, the output voltage gain of the synchronous rectification LLC converter adopting the control strategy of the synchronous rectification switch tube being turned on in advance is greatly improved. Under the same output gain, the switching frequency variation range can be greatly reduced.

[0041] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "one example", "some examples", "a specific example", or "some specific examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0042] The above is a further detailed description of the present application in combination with specific embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, some simple deductions or replacements can be made without departing from the concept of the present application.

Claims

1. A control method for a synchronous rectifier converter with wide voltage regulation capability, characterized in that: The following steps are involved: Acquire a voltage signal across the load, and then control the frequencies of the primary first switch, the primary second switch, the primary third switch, and the primary fourth switch according to the voltage signal across the load, and simultaneously control the output voltage gain of the converter by controlling the advance conduction angle φ1 or the lag turn-off angle φ2 of the secondary first switch, the secondary second switch, the secondary third switch, and the secondary fourth switch; The converter includes a DC power supply, a first inductor, a second inductor, a third inductor, a transformer, a filter capacitor, an input capacitor, a load, a controller, a first primary switch, a second primary switch, a third primary switch, a fourth primary switch, a first secondary switch, a second secondary switch, a third secondary switch, and a fourth secondary switch; The positive electrode of the DC power supply is connected to one end of the input capacitor, one end of the primary first switch, and one end of the primary second switch. The negative electrode of the DC power supply is connected to the other end of the input capacitor, one end of the primary third switch, and one end of the primary fourth switch. The other end of the primary first switch, the other end of the primary third switch, and one end of the first inductor are connected. The other end of the primary second switch, the other end of the primary fourth switch, and one end of the second inductor are connected. The other end of the first inductor is connected to one end of the primary winding of the transformer and one end of the third inductor. The other end of the second inductor is connected to the other end of the primary winding of the transformer and the other end of the third inductor. One end of the secondary winding of the transformer is connected to one end of the secondary first switch and one end of the secondary third switch, the other end of the secondary winding of the transformer is connected to one end of the secondary second switch and one end of the secondary poisoning switch, the other end of the secondary first switch, the other end of the secondary second switch, one end of the filter capacitor, and one end of the load are connected, and the other end of the secondary third switch, the other end of the secondary fourth switch, the other end of the filter capacitor, and the other end of the load are connected; The controller is connected to the control end of the first primary switch, the control end of the second primary switch, the control end of the third primary switch, the control end of the fourth primary switch, the control end of the first secondary switch, the control end of the second secondary switch, the control end of the third secondary switch, and the control end of the fourth secondary switch; A minimum frequency fsmin is set. When the pulse frequency modulation reaches fsmin and needs to be further reduced, the frequencies of the primary first switch, the primary second switch, the primary third switch, the primary fourth switch, the secondary first switch, the secondary second switch, the secondary third switch, and the secondary fourth switch are fixed at fsmin. At the same time, the secondary first switch, the secondary second switch, the secondary third switch, and the secondary fourth switch are turned on in advance. By increasing the advance conduction angle φ1, the output voltage gain is improved. When the primary second and third switches are turned on, the resonant current is equal to the excitation inductor current, that is, when the circuit enters the O mode, the circuit parameters are designed so that during the O mode, the voltage across the secondary first switch and the secondary fourth switch oscillates. When the voltage across the secondary first switch and the secondary fourth switch reaches the oscillation valley, the secondary first switch and the secondary fourth switch are turned on, thereby reducing switching losses or achieving zero voltage turn-on soft switching. When the first and fourth primary switches are turned on, the resonant current is equal to the magnetizing inductor current, and the circuit enters the O mode, the circuit parameters are designed so that the voltage across the second and third secondary switches oscillates during the O mode. When the voltage across the second and third secondary switches reaches the valley value of the oscillation, the second and third secondary switches are turned on, thereby reducing switching losses or achieving zero-voltage soft switching.

2. The control method of a synchronous rectifier converter with wide voltage regulation capability according to claim 1, wherein: When the output voltage gain needs to be increased, the frequencies of the primary first switch, the primary second switch, the primary third switch, the primary fourth switch, the secondary first switch, the secondary second switch, the secondary third switch and the secondary fourth switch are reduced.

3. The control method of a synchronous rectifier converter with wide voltage regulation capability according to claim 1, wherein: A maximum frequency fsmax is set. When the pulse frequency modulation reaches fsmax and needs to be further increased, the frequencies of the primary first switch, the primary second switch, the primary third switch, the primary fourth switch, the secondary first switch, the secondary second switch, the secondary third switch, and the secondary fourth switch are fixed to a preset value less than the resonant frequency. At the same time, the secondary first switch, the secondary second switch, the secondary third switch, and the secondary fourth switch are turned off with hysteresis. By increasing the hysteresis turn-off angle φ2, the output voltage gain is reduced. When the second and third switches on the primary side are turned on and the resonant current is equal to the excitation inductor current, that is, the circuit enters the O mode, the second and third switches on the secondary side continue to be turned on, and then the second and third switches on the secondary side are turned off. When the first and fourth switches on the primary side are turned on and the resonant current is equal to the excitation inductor current, that is, the circuit enters the O mode, the first and fourth switches on the secondary side continue to be turned on, and then the second and third switches on the secondary side are turned off.

4. The control method of a synchronous rectifier converter with wide voltage regulation capability according to claim 1, wherein: The primary first switch, the primary second switch, the primary third switch, the primary fourth switch, the secondary first switch, the secondary second switch, the secondary third switch and the secondary fourth switch are wide bandgap semiconductor devices, field effect transistors or transistors.

5. The control method of a synchronous rectifier converter with wide voltage regulation capability according to claim 1, wherein: The converter is an LLC converter or an LCC converter.

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