Switching power supply multipath isolation drive circuit

Abstract

The utility model discloses a switching power supply multipath isolation drive circuit comprising a primary side circuit comprising a totem pole amplification circuit and an RLC series resonance circuit which are connected with each other; the secondary side circuit comprises a plurality of groups of output channels which are identical and isolated from one another, and each group of output channels are independently connected with respective power tubes to be driven; and the primary side of the pulse transformer T3 is provided with the primary side circuit, and the secondary side of the pulse transformer T3 is provided with the secondary side circuit. Single-path or multi-path driving can be carried out by increasing or decreasing the number of secondary windings of the isolation transformer; an isolation power supply does not need to be added for power supply, and the defect that the operation reliability of the power tube becomes poor due to the fact that the driving voltage of the isolation circuit for driving the power tube exceeds the Vgs voltage range of the power tube is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of switching power supplies, and more specifically, to a multi-channel isolation drive circuit for a switching power supply. Background Art

[0002] With the wide application of switching power supplies, the key device, the power switch tube, needs to continuously operate under high-frequency and high-voltage conditions. Since the driving ability of the power control chip to output PWM is limited, it is usually necessary to amplify and isolate the high-frequency driving signal provided by the control chip to drive the power switch tube. The synchronization of the driving circuit signal and the reliability of the switch are crucial for the long-term reliable operation of the power tube.

[0003] For multi-channel isolation drive, one common method currently is to use an optocoupler to complete signal amplification and isolation. However, an isolated power supply needs to be added to the secondary side of the optocoupler, which increases the complexity of the circuit design, and the signal transmission delay of the optocoupler is relatively large, which is not conducive to the rapid adjustment and control of the PWM signal of the switching power supply. Another method is to use a transformer isolation drive. For a conventional transformer isolation drive, after passing through a DC-blocking capacitor, it then drives the power tube via a current-limiting resistor. The positive and negative voltage amplitudes of the driving voltage vary with the duty cycle, which may cause the voltage to exceed the Vgs voltage range of the power tube, resulting in poor reliability of the power tube operation. Summary of the Utility Model

[0004] The technical problem to be solved by the present application is to provide a multi-channel isolation drive circuit for a switching power supply to increase the driving ability, while meeting the dynamic response of the driving voltage, adjusting the driving voltage and switching time of the switch tube according to actual needs, improving the reliability of the power tube operation; and effectively preventing the isolation transformer from saturating.

[0005] The present application adopts the following technical solutions to solve the above technical problems:

[0006] A multi-channel isolation drive circuit for a switching power supply, characterized by comprising:

[0007] A primary side circuit, including a totem pole amplifier circuit and an RLC series resonance circuit connected to each other;

[0008] A secondary side circuit, including multiple groups of output channels that are exactly the same and isolated from each other, and each group of output channels is separately connected to its respective power tube to be driven;

[0009] And a pulse transformer T3, with the primary side provided with the primary side circuit and the secondary side provided with the secondary side circuit.

[0010] In the above technical solution, in the primary side circuit, the resistor R2, the resistor R3, the DC-blocking capacitor C1 and the primary inductance of the pulse transformer T3 are connected in series to form an RLC series resonance circuit; a totem pole amplifier circuit and a voltage limiting circuit are arranged between the resistor R1 and the resistor R3; the NPN transistor T1 and the PNP transistor T2 form a totem pole amplifier circuit, and the diodes D1 and D2 form a voltage limiting circuit.

[0011] In the above technical solution, in the primary side circuit, the RLC series resonance circuit is configured according to the following relationship:

[0012] Damping ratio ;

[0013] The primary resonance frequency f1 =

[0014] The driving signal frequency fsw = (10~20)×f1;

[0015] where: Lp is the primary inductance of the transformer, Lk is the leakage inductance of the transformer, and Ls is the secondary inductance of the transformer.

[0016] In the above technical solution, in the secondary side circuit, each output channel includes a DC-blocking capacitor, three diodes, and three resistors; among them, two zener diodes are connected in series to form a positive and negative voltage limiting circuit, the first resistor is a power tube turn-on circuit, and another diode is connected in series with the second resistor and then in parallel with the first resistor to form a power tube turn-off circuit, and the third resistor forms a power tube static charge discharge circuit; the corresponding power tube to be driven of this output channel is connected in parallel after the third resistor.

[0017] In the above technical solution, in the secondary side circuit, it includes 3-8 groups of completely identical and isolated output channels, and each group of channels drives the corresponding power tube to be driven separately.

[0018] In the above technical solution, in the secondary side circuit, it includes 4 groups of completely identical and isolated output channels, and each group of channels drives the corresponding power tube to be driven separately.

[0019] In the above technical solution, the turns ratio of the primary and secondary sides of the transformer and the voltage of the zener diode are set according to the required driving voltage.

[0020] In the above technical solution, to meet the dynamic response of the system, the secondary resonance frequency , and fsw is configured to be dozens of times f2.

[0021] In the above technical solution, the first resistor is configured to adjust the turn-on time of the power tube, the second resistor is configured to adjust the turn-off time of the power tube; the third resistor discharges the static charge of the gate-source stage of the switching tube to prevent the switching tube from being accidentally turned on when powered on.

[0022] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0023] A multi-channel isolated drive circuit for a switching power supply is provided, which can perform single-channel or multi-channel drive by increasing or decreasing the number of secondary windings of the isolation transformer; there is no need to increase the isolated power supply, and it also avoids the defect that the drive voltage of the isolation circuit driving the power transistor exceeds the Vgs voltage range of the power transistor, resulting in poor operating reliability of the power transistor.

[0024] The control signal passes through the totem pole drive circuit, which can increase the drive ability.

[0025] The primary current-limiting resistor and DC-blocking capacitor of the transformer can effectively prevent the isolation transformer from saturating;

[0026] The turn-on and turn-off times of the power transistor can be adjusted separately, which can optimize the turn-on and turn-off losses and EMI characteristics of the power transistor, and improve the operating reliability of the power transistor;

[0027] The positive and negative limiting voltages of the drive voltage of the power transistor are adjustable to ensure the operating reliability of the power transistor. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 It is a structural diagram of the multi-channel isolated drive circuit of the switching power supply for the embodiment of the present application. Detailed Embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Usually, the components of the embodiments of the present application described and illustrated herein can be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application claimed, but merely represents the selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0032] It should be noted that like reference numerals and letters indicate like items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0033] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship in which the product of this application is usually placed during use. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0034] In addition, terms such as "horizontal", "vertical", "hanging" do not mean that the components are required to be absolutely horizontal or hanging, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0035] In the description of the present application, it should also be noted that unless otherwise clearly specified and defined, the terms "set", "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; 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 communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0036] In the present application, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features between them. Moreover, the first feature being "above", "over" and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "under" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or only means that the horizontal height of the first feature is lower than that of the second feature.

[0037] The features and performance of the present application will be further described in detail below in conjunction with embodiments.

[0038] Embodiment 1

[0039] In view of the technical deficiencies of the existing solutions, this embodiment constructs a multi-channel isolated drive circuit for a switching power supply, which includes a primary-side circuit, a pulse transformer T3, and a secondary-side circuit. The primary-side circuit and the secondary-side circuit form a step-down regulation system through the pulse transformer T3.

[0040] The primary-side circuit includes resistors R1, R2, R3, an NPN transistor T1, a PNP transistor T2, diodes D1, D2, and a DC-blocking capacitor C1. The resistor R1 is a current-limiting resistor for the transistor base. The NPN transistor T1 and the PNP transistor T2 form a totem-pole amplifier circuit to increase the driving ability through the totem-pole amplifier circuit.

[0041] The diodes D1 and D2 form a voltage-limiting circuit. The resistors R2, R3, the DC-blocking capacitor C1, and the primary inductance of the pulse transformer T3 form an RLC series resonance circuit.

[0042] The secondary-side circuit includes four identical and isolated output channels from each other. Each channel individually drives the corresponding power transistor (Q1, Q2, Q3, or Q4).

[0043] Taking the first group of output channels that individually drive the corresponding power transistor Q1 as an example, the circuit of the first group of output channels includes a capacitor C2, two zener diodes ZD7, ZD8, another diode D6, and three resistors R7, R11, and R12. Among them, the capacitor C2 is a DC-blocking capacitor. The zener diodes ZD7 and ZD8 form a positive and negative voltage limiting circuit. The first resistor R7 is a power transistor turn-on circuit. The diode D6 is connected in series with the second resistor R11 and then connected in parallel with the first resistor R7 to form a power transistor turn-off circuit. The third resistor R12 forms a power transistor static charge discharge circuit. The other three groups of output channels are the same.

[0044] And so on, the structures of the second group of output channels, the third group of output channels, and the fourth group of output channels are the same as those of the first group, and will not be elaborated here.

[0045] Preferably, the RLC series resonance circuit is configured according to the following relationship:

[0046] Damping ratio ;

[0047] Primary resonance frequency f1 =

[0048] Drive signal frequency fsw = (10~20)×f1; where:

[0049] Lp is the primary inductance of the transformer, Lk is the leakage inductance of the transformer, and fsw is the drive signal frequency.

[0050] Preferably, set the turns ratio of the primary and secondary sides of the transformer and the zener diode voltage according to the required drive voltage:

[0051] Secondary side resonance frequency , configure fsw to be dozens of times of f2 to meet the system dynamic response; where Ls is the inductance of the secondary side of the transformer;

[0052] Configure resistor R7 to adjust the turn-on time of the power transistor, configure R11 to adjust the turn-off time of the power transistor; configure R12 to discharge the static charge of the gate-source stage of the switching transistor to prevent the switching transistor from being erroneously turned on when powered on;

[0053] Through the above configuration, multi-channel isolated drive of the switching power supply is satisfied, and the drive voltage and switching time of the switching transistor can be adjusted according to actual needs.

[0054] Embodiment 2

[0055] Based on the embodiment, there are changes, for example, the secondary side circuit includes 3-8 groups of identical and isolated output channels from each other, and each group of channels drives the corresponding power transistor separately.

[0056] Within the range that the front-end primary side circuit can load, those skilled in the art can adjust the number of channels of the secondary side circuit according to requirements. It does not constitute a limitation to this embodiment.

[0057] The embodiments described above are some embodiments of the present application, rather than all embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application.

Claims

1. A switching power supply multi-channel isolation drive circuit, characterized in that include: A primary side circuit includes a totem pole amplifier circuit and an RLC series resonant circuit connected to each other; The secondary side circuit includes a plurality of groups of output channels that are identical and isolated from each other, and each group of output channels is individually connected to its own power tube to be driven; And a pulse transformer T3, the primary side is provided with the primary side circuit, and the secondary side is provided with the secondary side circuit.

2. The switching power supply multi-channel isolation drive circuit according to claim 1, characterized in that In the primary side circuit, resistor R2, resistor R3, DC blocking capacitor C1 and primary inductor of pulse transformer T3 are connected in series to form an RLC series resonant circuit; a totem pole amplifier circuit and a voltage limiting circuit are arranged between resistor R1 and resistor R3; NPN transistor T1 and PNP transistor T2 form a totem pole amplifier circuit, and diodes D1 and D2 form a voltage limiting circuit.

3. The switching power supply multi-channel isolation drive circuit according to claim 1, characterized in that The RLC series resonant circuit is configured according to the following relationship: Damping ratio ; Primary resonance frequency f1= Driving signal frequency fsw=(10~20)×f1; Where: Lp is the primary inductance of the transformer, Lk is the leakage inductance of the transformer, and Ls is the secondary inductance of the transformer.

4. The switching power supply multi-channel isolation drive circuit according to claim 1, characterized in that In the secondary side circuit, each output channel includes a DC blocking capacitor, three diodes, and three resistors; wherein two voltage stabilizing diodes are connected in series to form a positive and negative voltage limiting circuit, the first resistor is a power tube turn-on circuit, another diode is connected in series with the second resistor and then in parallel with the first resistor to form a power tube turn-off circuit, and the third resistor constitutes a power tube static charge discharge circuit; the power tube to be driven corresponding to the output channel is connected in parallel after the third resistor.

5. The switching power supply multi-channel isolation drive circuit according to claim 1, characterized in that The secondary side circuit includes 3-8 groups of output channels that are completely identical and isolated from each other, and each group of channels independently drives the corresponding power tube to be driven.

6. The switching power supply multi-channel isolation drive circuit according to claim 1, characterized in that The secondary side circuit includes 4 groups of output channels that are completely identical and isolated from each other, and each group of channels independently drives the corresponding power tube to be driven.

7. The switching power supply multi-channel isolation drive circuit according to claim 1, characterized in that Set the transformer primary-to-secondary turns ratio and Zener diode voltage according to the required drive voltage.

8. The switching power supply multi-channel isolation drive circuit according to claim 1, characterized in that Set the secondary resonant frequency , configure fsw to be dozens of times of f2.

9. The switching power supply multi-channel isolation drive circuit according to claim 1, characterized in that The first resistor is configured to adjust the power tube turn-on time, and the second resistor is configured to adjust the power tube turn-off time; the third resistor is configured to discharge the static charge of the gate-source level of the switch tube to prevent the switch tube from being turned on by mistake when power is turned on.

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