A multi-output soft-switching power supply

Abstract

The present invention discloses a multi-output soft-switching power supply, which includes an input Vin, a capacitor C1, a capacitor C2, a switching transistor S1, a switching transistor S2, a switching transistor S3, a diode D1, a diode D2, an inductor L1, an inductor Lm, an inductor Lr, a main resonant transformer T1, an auxiliary flyback transformer T2, a main output Vo1, an auxiliary output Vo2, an output rectification circuit, and a drive control circuit. Beneficial effects: The present invention strongly ensures the zero-voltage turn-on of the main switching transistor S2 and also realizes the zero-voltage turn-on of the switching transistor S3; while being independently controllable, frequency synchronization is achieved, reducing the difficulty of EMC design; compared with traditional multi-output circuit combinations, the circuit is simple, the control is convenient, the conversion efficiency is high, the circuit cost is low, and there are many beneficial effects in implementation.

Description

Technical Field

[0001] The invention relates to the field of power supplies, and in particular to a multi-channel output soft switching power supply. Background Art

[0002] In the field of power supply, high power density, high efficiency and low cost driving power supply are more competitive. Usually, the driving power supply will choose the resonant circuit to achieve the purpose of high power density and high efficiency. The resonant circuit can realize the zero voltage turn-on of two or more switching tubes on the primary side and the zero current turn-off of the secondary side rectifier diode, which can reduce the switching loss of the power supply and improve the efficiency and power density of the power converter.

[0003] In practical applications, the system often requires multiple output power supplies to supply power to different module units. Generally, the main load unit consumes a relatively high power, and the power requirements of other auxiliary units are relatively lower. Generally, a flyback converter is selected, but the leakage inductance energy of an ordinary single-tube flyback transformer cannot be transferred to the secondary side, which will generate stress spikes and can only be dissipated, with low conversion efficiency. In addition, the operating frequencies of the two power supplies are not synchronized, which can easily cause EMC beat frequency ringing problems.

[0004] In view of this, providing a high-efficiency and low-cost multi-output power supply has become a technical problem that needs to be solved urgently by those skilled in the art.

[0005] Currently, no effective solution has been proposed for the problems in the related technologies. Summary of the invention

[0006] In view of the problems in the related art, the present invention proposes a multi-output soft switching power supply to overcome the above technical problems existing in the existing related art.

[0007] To this end, the specific technical solution adopted by the present invention is as follows:

[0008] A multi-output soft-switching power supply includes an input Vin, a capacitor C1, a capacitor C2, a switching transistor S1, a switching transistor S2, a switching transistor S3, a diode D1, a diode D2, an inductor L1, an inductor Lm, an inductor Lr, a main resonant transformer T1, an auxiliary flyback transformer T2, a main output Vo1, an auxiliary output Vo2, an output rectification circuit, and a drive control circuit; the input Vin is connected in parallel with the capacitor C1, the positive electrode of the capacitor C1 is sequentially connected to the first end of the switching transistor S1 and the negative electrode of the diode D1, the negative electrode of the capacitor C1 is sequentially connected to the second end of the switching transistor S2, one end of the capacitor C2, and the second end of the switching transistor S3 and is grounded, the second end of the switching transistor S1 is sequentially connected to one end of the inductor L1, one end of the inductor Lr, and the first end of the switching transistor S2, the other end of the inductor L1 is connected to the first input terminal of the main resonant transformer T1, the second input terminal of the main resonant transformer T1 is connected to the other end of the capacitor C2, the output terminal of the main resonant transformer T1 is connected in parallel with the output rectification circuit, the output rectification circuit is connected in parallel with the main output Vo1, the other end of the inductor Lr is sequentially connected to one end of the inductor Lm and the first input terminal of the auxiliary flyback transformer T2, the second input terminal of the auxiliary flyback transformer T2 is sequentially connected to the other end of the inductor Lm, the first end of the switching transistor S3, and the positive electrode of the diode D1, the first output terminal of the auxiliary flyback transformer T2 is connected to the positive electrode of the diode D2, the negative electrode of the diode D2 is connected to the positive electrode of the auxiliary output Vo2, the negative electrode of the auxiliary output Vo2 is connected to the second output terminal of the auxiliary flyback transformer T2 and is grounded, the third output terminal of the auxiliary flyback transformer T2 is grounded, the fourth output terminal of the auxiliary flyback transformer T2 is connected to the ZCD terminal of the drive control circuit, the first end of the drive control circuit is connected to the third end of the switching transistor S1, the second end of the drive control circuit is connected to the third end of the switching transistor S2, and the third end of the drive control circuit is connected to the third end of the switching transistor S3.

[0009] Further, the capacitor C1 is a polarized capacitor.

[0010] Further, the main output Vo1 is a polarized capacitor.

[0011] Further, the auxiliary output Vo2 is a polarized capacitor.

[0012] Further, the main resonant circuit adopts frequency feedback control of the output voltage or output current, symmetrically and complementarily drives S1 and S2, and obtains the set output voltage Vo or output current Io through frequency control.

[0013] Further, the turn-on of the auxiliary road control switch, i.e., the switching transistor S3, is basically synchronized with the turn-off edge of the switching transistor S2; the switching transistor S3 turns on earlier than the switching transistor S1; the switching transistor S3 turns off earlier than the switching transistor S1, and the duty cycle is always less than 0.5. Similar to the dual-switch flyback circuit, its duty cycle is controlled by load feedback. The larger the duty cycle, the greater the output energy.

[0014] Further, when the switching transistor S2 turns off, the switching transistor S3 is immediately turned on with zero voltage switching (ZVS); after a dead time delay, the switching transistor S1 turns on.

[0015] Further, the auxiliary winding of the auxiliary flyback transformer T2 provides a zero-crossing detection (ZCD) signal; after the diode D2 turns off with zero current, the switching transistors S1 and S3 are turned on; in case of an abnormal condition, when the switching transistor S2 turns off, if the drive control circuit does not detect the ZCD signal, it will wait with a time delay until the ZCD signal is detected, and the switching transistor S3 is turned on at the valley voltage, and then the switching transistor S3 is turned off before the switching transistor S1 turns off under the control of the circuit feedback.

[0016] The beneficial effects of the present invention are as follows:

[0017] (1) The main circuit and the auxiliary circuit of the present invention share the switching transistor S1, which not only ensures the zero-voltage turn-on of the main circuit switching transistor S2, but also recovers the leakage inductance energy of the auxiliary transformer, reduces the device stress of the switching transistor S3, and realizes the zero-voltage turn-on of the switching transistor S3 through control optimization; while being independently controllable, frequency synchronization is achieved, and the difficulty of EMC design is reduced.

[0018] (2) The multi-output soft-switching power supply of the present invention is simpler in circuit, more convenient to control, higher in conversion efficiency, lower in circuit cost, and has more beneficial effects compared with the traditional multi-output circuit combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings without creative efforts based on these drawings.

[0020] Figure 1 is a schematic diagram of a multi-output soft-switching power supply according to an embodiment of the present invention;

[0021] Figure 2 is Figure 1 the voltage waveform diagram in DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] To further illustrate the embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0023] According to an embodiment of the present invention, a multi-output soft-switching power supply is provided.

[0024] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation manners. As Figure 1 shown, the multi-output soft-switching power supply according to an embodiment of the present invention includes an input Vin, a capacitor C1, a capacitor C2, a switching transistor S1, a switching transistor S2, a switching transistor S3, a diode D1, a diode D2, an inductor L1, an inductor Lm, an inductor Lr, a main resonance transformer T1, an auxiliary flyback transformer T2, a main output Vo1, an auxiliary output Vo2, an output rectification circuit, and a drive control circuit; the input Vin is connected in parallel with the capacitor C1, the positive electrode of the capacitor C1 is sequentially connected to the first end of the switching transistor S1 and the negative electrode of the diode D1, the negative electrode of the capacitor C1 is sequentially connected to the second end of the switching transistor S2, one end of the capacitor C2, and the second end of the switching transistor S3 and grounded, the second end of the switching transistor S1 is sequentially connected to one end of the inductor L1, one end of the inductor Lr, and the first end of the switching transistor S2, the other end of the inductor L1 is connected to the first input terminal of the main resonance transformer T1, the second input terminal of the main resonance transformer T1 is connected to the other end of the capacitor C2, the output terminal of the main resonance transformer T1 is connected in parallel with the output rectification circuit, the output rectification circuit is connected in parallel with the main output Vo1, the other end of the inductor Lr is sequentially connected to one end of the inductor Lm and the first input terminal of the auxiliary flyback transformer T2, the second input terminal of the auxiliary flyback transformer T2 is sequentially connected to the other end of the inductor Lm, the first end of the switching transistor S3, and the positive electrode of the diode D1, the first output terminal of the auxiliary flyback transformer T2 is connected to the positive electrode of the diode D2, the negative electrode of the diode D2 is connected to the positive electrode of the auxiliary output Vo2, the negative electrode of the auxiliary output Vo2 is connected to the second output terminal of the auxiliary flyback transformer T2 and grounded, the third output terminal of the auxiliary flyback transformer T2 is grounded, the fourth output terminal of the auxiliary flyback transformer T2 is connected to the ZCD terminal of the drive control circuit, the first end of the drive control circuit is connected to the third end of the switching transistor S1, the second end of the drive control circuit is connected to the third end of the switching transistor S2, and the third end of the drive control circuit is connected to the third end of the switching transistor S3.

[0025] In one embodiment, the capacitor C1 is a polarized capacitor.

[0026] In one embodiment, the main circuit output Vo1 is a polarized capacitor.

[0027] In one embodiment, the auxiliary output Vo2 is a polarized capacitor.

[0028] In one embodiment, the main resonant circuit adopts frequency feedback control of the output voltage or output current. Its control method is similar to that of a general series resonant or series - parallel resonant circuit. Symmetric complementary driving S1 and S2, through frequency control, the set output voltage Vo or output current Io is obtained.

[0029] In one embodiment, the turning - on of the auxiliary control switch, i.e., the switching transistor S3, is basically synchronous with the turning - off edge of the switching transistor S2. Because there is a dead - time between the driving of the switching transistor S1 and the switching transistor S2, in the normal state, the switching transistor S3 turns on earlier than the switching transistor S1. In the abnormal state, the switching transistor S1 turns on slightly later to ensure the excitation reset of the auxiliary flyback transformer T2, and then turns on to avoid the losses and device stress spikes caused by reverse recovery. The switching transistor S3 turns off earlier than the switching transistor S1, and the duty cycle is always less than 0.5. Similar to the double - transistor flyback circuit, its duty cycle is controlled by load feedback. The larger the duty cycle, the greater the output energy. For the auxiliary circuit, the switching transistors S1 and S3 actually form a double - transistor flyback, and the energy of the inductor Lr can be recycled and will not be dissipated. The energy of the auxiliary circuit is controlled by the conduction duty cycle of the switching transistor S3. The device stress of the switching transistor S3 is equal to the input voltage Vin, and compared with the single - transistor flyback, the device stress is greatly reduced. Compared with the ordinary double - transistor flyback, since the switching transistor S1 of the main circuit is reused here, the high - end switching transistor and its complex isolation driving circuit of the double - transistor flyback circuit are saved, and the circuit is simpler and the cost is lower.

[0030] In one embodiment, different from the single - transistor and double - transistor flybacks, during the conduction period of the switching transistor S2, the static voltage of the switching transistor S3 is zero. As long as the inductors Lr and Lm are reset, the switching transistor S3 will quickly stabilize to zero voltage. Therefore, the switching transistor S3 has the natural ZVS (zero - voltage switching) turn - on condition. The switching transistor S3 turns on ZVS immediately when the switching transistor S2 turns off. After a dead - time delay, the switching transistor S1 turns on. In this way, both the switching transistor S1 and the switching transistor S3 can ensure ZVS turn - on, reducing the turn - on loss.

[0031] In one embodiment, the auxiliary winding of the auxiliary flyback transformer T2 provides a ZCD signal, which is used to determine whether the magnetizing inductance current of the auxiliary flyback transformer T2 has returned to zero, that is, whether the diode D2 has been turned off by ZCS (zero-current turn-off); after the diode D2 is turned off with zero current, the switch tube S1 and the switch tube S3 are turned on, which can ensure that there is no reverse recovery loss; in the event of an abnormal condition, when the switch tube S2 is turned off, if the drive control circuit does not detect the ZCD signal, it will wait with a time delay until the ZCD signal is detected, and the switch tube S3 is turned on at the valley voltage, and then the switch tube S3 is turned off before the switch tube S1 is turned off under the control of the circuit feedback.

[0032] In one embodiment, when the main circuit is lightly loaded, the magnetizing inductance current of the main resonant transformer T1 decreases, and it is often impossible to ensure the effective ZVS turn-on of the switch tube. Through analysis, we know that when the switch tube S1 is turned off, due to the energy stored additionally in the auxiliary flyback transformer T2, acting together with the magnetizing energy of the main resonant transformer T1, it can ensure that the switch tube S2 can be turned on with zero voltage. And before the switch tube S2 is turned off, the energy of the inductor Lr has already been released, so it will not affect the original ZVS turn-on condition of the switch tube S1; in view of the above analysis, the main circuit and the auxiliary circuit share the switch tube S1, and the beneficial implementation effect is very obvious.

[0033] In one embodiment, when more output paths are required, it is easy for those skilled in the art to deduce that sharing the switch tube S1 can achieve more output paths and obtain the same beneficial implementation effect.

[0034] To facilitate the understanding of the above technical solutions of the present invention, the working principle or operation mode of the present invention in the actual process will be described in detail below.

[0035] In actual application, when the switch tube S1 is turned on, the switch tube S2 is turned off, and the switch tube S3 is turned on, the main circuit current passes through the switch tube S1, the inductor L1, the transformer T1, the resonant capacitor C2, and the capacitor C1. The auxiliary circuit current passes through the switch tube S1, the auxiliary flyback transformer T2, and the capacitor C1;

[0036] When the switch tube S1 is turned on, the switch tube S2 is turned off, and the switch tube S3 is turned off, the main circuit current passes through the switch tube S1, the inductor L1, the transformer T1, the resonant capacitor C2, and the capacitor C1. The auxiliary circuit current passes through the switch tube S1, the auxiliary flyback transformer T2, and the diode D1;

[0037] When the switching transistor S1 is turned off, the switching transistor S2 is turned on, and the switching transistor S3 is turned off, the main circuit current passes through the switching transistor S2, the inductor L1, the transformer T1, and the resonant capacitor C2. The leakage inductance current of the auxiliary circuit passes through the switching transistor S2, the inductor Lr, the transformer T2, the diode D1, the input capacitor C1, and the excitation inductor Lm of the auxiliary circuit releases stored energy to the auxiliary output Vo2 through the auxiliary flyback transformer T2 and the diode D2;

[0038] The main circuit resonant circuit provides energy to the main circuit output Vo1 load through the main resonant transformer T1 and the output rectifier circuit.

[0039] In summary, the main circuit and the auxiliary circuit of the present invention reuse the switching transistor S1, which not only ensures the zero-voltage turn-on of the main circuit switching transistor S2, but also recovers the leakage inductance energy of the auxiliary circuit transformer, reduces the device stress of the switching transistor S3, and realizes the zero-voltage turn-on of the switching transistor S3 through control optimization; while being independently controllable, frequency synchronization is achieved, and the difficulty of EMC design is reduced. The multi-output soft-switching power supply of the present invention is simpler in circuit, more convenient to control, higher in conversion efficiency, lower in circuit cost, and has more beneficial effects compared with the traditional multi-output circuit combination.

[0040] In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "setting", "connection", "fixation", "rotation connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two components or the interaction relationship between two components. Unless otherwise clearly limited, for those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0041] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-output soft-switching power supply, characterized in that, It includes an input Vin, a capacitor C1, a capacitor C2, a switching transistor S1, a switching transistor S2, a switching transistor S3, a diode D1, a diode D2, an inductor L1, an inductor Lm, an inductor Lr, a main resonant transformer T1, an auxiliary flyback transformer T2, a main path output Vo1, an auxiliary output Vo2, an output rectifying circuit, and a drive control circuit; Among them, the input Vin is connected in parallel with the capacitor C1. The positive pole of the capacitor C1 is sequentially connected to the first end of the switching transistor S1 and the negative pole of the diode D1. The negative pole of the capacitor C1 is sequentially connected to the second end of the switching transistor S2, one end of the capacitor C2, and the second end of the switching transistor S3 and grounded. The second end of the switching transistor S1 is sequentially connected to one end of the inductor L1, one end of the inductor Lr, and the first end of the switching transistor S2. The other end of the inductor L1 is connected to the first input terminal of the main resonant transformer T1. The second input terminal of the main resonant transformer T1 is connected to the other end of the capacitor C2. The output terminal of the main resonant transformer T1 is connected in parallel with the output rectifying circuit. The output rectifying circuit is connected in parallel with the main path output Vo1. The other end of the inductor Lr is sequentially connected to one end of the inductor Lm and the first input terminal of the auxiliary flyback transformer T2. The second input terminal of the auxiliary flyback transformer T2 is sequentially connected to the other end of the inductor Lm, the first end of the switching transistor S3, and the positive pole of the diode D1. The first output terminal of the auxiliary flyback transformer T2 is connected to the positive pole of the diode D2. The negative pole of the diode D2 is connected to the positive pole of the auxiliary output Vo2. The negative pole of the auxiliary output Vo2 is connected to the second output terminal of the auxiliary flyback transformer T2 and grounded. The third output terminal of the auxiliary flyback transformer T2 is grounded. The fourth output terminal of the auxiliary flyback transformer T2 is connected to the ZCD terminal of the drive control circuit. The first end of the drive control circuit is connected to the third end of the switching transistor S1. The second end of the drive control circuit is connected to the third end of the switching transistor S2. The third end of the drive control circuit is connected to the third end of the switching transistor S3; The on and off edges of the auxiliary path control switch, i.e., the switching transistor S3, are synchronized with the off edge of the switching transistor S2; the switching transistor S3 turns on earlier than the switching transistor S1; the switching transistor S3 turns off earlier than the switching transistor S1, and the duty cycle is always less than 0.

5. Similar to the double-switch flyback circuit, its duty cycle is controlled by load feedback. The larger the duty cycle, the greater the output energy; When the switching transistor S2 turns off, the switching transistor S3 is immediately turned on with zero voltage switching (ZVS); after a dead time delay, the switching transistor S1 is turned on.

2. The multi-output soft-switching power supply according to claim 1, characterized in that, The capacitor C1 is a polarized capacitor.

3. A multi-output soft-switching power supply according to claim 1, characterized in that, The main path output Vo1 is a polarized capacitor.

4. A multi-output soft-switching power supply according to claim 1, characterized in that, The auxiliary output Vo2 is a polarized capacitor.

5. The multi-output soft-switching power supply according to claim 1, wherein The main resonant circuit adopts frequency feedback control of the output voltage or output current, symmetrically complementary drives S1 and S2, and obtains the set output voltage Vo or output current Io through frequency control.

6. The multi-output soft-switching power supply according to claim 1, wherein The auxiliary winding of the auxiliary flyback transformer T2 provides a ZCD signal; after the diode D2 turns off with zero current, the switch tube S1 and the switch tube S3 are turned on; in the event of an abnormal condition, when the switch tube S2 turns off, if the drive control circuit does not detect the ZCD signal, it will wait with a delay until the ZCD signal is detected, turn on the switch tube S3 at the valley voltage, and then turn off the switch tube S3 before the switch tube S1 turns off under the feedback control of the circuit.

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