A flyback switching power supply starting conduction control circuit and device

Abstract

The application discloses a starting conduction control circuit and device of a flyback switching power supply, wherein a first voltage detection module is arranged to obtain the grid power output voltage of the flyback transformer switching power supply circuit, namely the first voltage; a second voltage detection module is arranged to obtain the secondary coil output voltage of the flyback transformer switching power supply circuit, namely the second voltage; and when the first voltage and the second voltage are not zero, the auxiliary coil output voltage of the flyback transformer switching power supply circuit is conducted to the load through a conduction control module, at this time, the flyback power control chip has been started and completed, the auxiliary coil realizes power supply to the flyback power control chip and the load, and the normal starting of the flyback power control chip is not affected; since the series resistance value between the primary coil and the flyback power control chip power input pin does not need to be reduced, and a secondary coil for power supply to the load does not need to be introduced, the problems of increased loss and reduced transformer coil utilization rate do not exist.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a flyback switching power supply startup and conduction control circuit and device. Background Art

[0002] Existing AC-to-DC flyback transformer switching power supply circuits generally consist of a diode bridge rectifier, busbar capacitors, a flyback power supply control chip, a transformer, a diode, and a filter capacitor. The transformer includes a primary coil, a secondary coil, and an auxiliary coil, and the flyback power supply control chip is powered by both the transformer's primary coil and the auxiliary coil. The voltage required for the flyback power supply control chip's initial startup is obtained by connecting a resistor in series with the primary coil to the power input pin. Once the flyback power supply control chip completes startup and a voltage output is generated at the auxiliary coil, the auxiliary coil output voltage then powers the flyback power supply control chip.

[0003] If there are other loads in the circuit that share the output voltage generated by the auxiliary coil of the transformer with the flyback power supply control chip for power supply, it is necessary to reduce the resistance of the series resistor between the primary coil and the power input pin of the flyback power supply control chip, otherwise the flyback power supply control chip will not start normally. At the same time, after the resistance of the series resistor is reduced, the loss on the series resistor increases, thereby increasing the heat generation. In order to cope with the sharp increase in the loss on the series resistor, the traditional method uses multiple resistors in parallel and then in series to reduce the loss on a single resistor to reduce heat generation, or by adding an additional transformer secondary coil to power the load. However, the above two methods will result in a significant increase in the size and weight of the transformer, and adding a secondary coil will reduce the utilization rate of the transformer coil. Summary of the Invention

[0004] The purpose of the present invention is to solve one of the technical problems existing in the prior art to at least a certain extent.

[0005] To this end, an embodiment of the present invention provides a flyback switching power supply startup and conduction control circuit and device, which realizes the power supply of the flyback power supply control chip and the load by the auxiliary coil of the transformer without the problems of increased loss and reduced transformer coil utilization.

[0006] On the one hand, the technical solutions adopted by the embodiments of the present invention include:

[0007] A flyback switching power supply startup and conduction control circuit is applied to a flyback transformer switching power supply circuit, comprising:

[0008] A first voltage detection module is used to obtain a first voltage, where the first voltage is the grid power output voltage of the flyback transformer switching power supply circuit;

[0009] A second voltage detection module is used to obtain a second voltage, where the second voltage is the secondary coil output voltage of the flyback transformer switching power supply circuit;

[0010] A conduction control module is used to conduct the auxiliary coil output voltage of the flyback transformer switching power supply circuit to the load when the first voltage and the second voltage are not zero; and is used to disconnect the auxiliary coil output voltage of the flyback transformer switching power supply circuit from the load when the first voltage is zero or the second voltage is zero.

[0011] As an optional implementation, the first voltage detection module includes a voltage dividing module and an anti-reverse connection module;

[0012] The input end of the anti-reverse connection module is used to connect to the grid power output of the flyback transformer switching power supply circuit, the output end of the anti-reverse connection module is connected to the input end of the voltage divider module, and the output end of the voltage divider module is used to output a third voltage, which is the voltage obtained after the first voltage is divided by the voltage divider module.

[0013] As an optional implementation, the anti-reverse connection module includes a diode, and the voltage divider module includes a first resistor, a second resistor, a third resistor and a capacitor;

[0014] The anode of the diode is used to be connected to the grid power output of the flyback transformer switching power supply circuit, the cathode of the diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the second resistor, the second end of the second resistor is connected to the first end of the third resistor, the second end of the third resistor is grounded, the second end of the third resistor is also connected to the first end of the capacitor, and the second end of the capacitor is connected to the first end of the third resistor;

[0015] The first voltage is divided by the first resistor, the second resistor, and the third resistor, and then output as the third voltage at the first end of the third resistor.

[0016] As an optional implementation, the second voltage detection module includes an optocoupler and a fourth resistor;

[0017] The first end of the optocoupler is used to connect to the secondary coil output of the flyback transformer switching power supply circuit, the second end of the optocoupler is grounded through the fourth resistor, and the fourth end of the optocoupler is grounded;

[0018] When current flows from the first end to the second end of the optical coupler, the third end and the fourth end of the optical coupler are conductive.

[0019] As an optional implementation, the optical coupler includes an input-end diode and an output-end transistor;

[0020] The anode of the input-end diode is used to connect to the secondary coil output of the flyback transformer switching power supply circuit, the cathode of the input-end diode is connected to the first end of the fourth resistor, the second end of the fourth resistor is grounded, and the emitter of the output-end transistor is grounded.

[0021] As an optional implementation, the input diode is a light emitting diode;

[0022] When current flows from the anode to the cathode of the input-end diode, the input-end diode is lit and the output-end transistor is turned on.

[0023] As an optional embodiment, the second end of the fourth resistor is connected to the ground of the output end of the secondary coil of the flyback transformer switching power supply circuit, and the emitter of the output transistor is connected to the ground of the output end of the auxiliary coil of the flyback transformer switching power supply circuit.

[0024] As an optional implementation manner, the conduction control module includes an NMOS tube, a bipolar transistor, a fifth resistor and a sixth resistor;

[0025] The gate of the NMOS tube is connected to the first end of the third resistor, the source of the NMOS tube is connected to the collector of the output transistor, the drain of the NMOS tube is connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the base of the bipolar transistor, the base of the bipolar transistor is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the emitter of the bipolar transistor, the emitter of the bipolar transistor is connected to the auxiliary coil output of the flyback transformer switching power supply circuit, and the collector of the bipolar transistor is used to connect the load of the flyback transformer switching power supply circuit.

[0026] On the other hand, the technical solutions adopted in the embodiments of the present invention include:

[0027] A flyback switching power supply startup and conduction control device comprises the flyback switching power supply startup and conduction control circuit.

[0028] Advantages and beneficial effects of the present invention:

[0029] The flyback switching power supply startup and conduction control circuit and device of the embodiment of the present invention provide a first voltage detection module to obtain the grid power output voltage of the flyback transformer switching power supply circuit, i.e., the first voltage; provide a second voltage detection module to obtain the secondary coil output voltage of the flyback transformer switching power supply circuit, i.e., the second voltage; and conduct the auxiliary coil output voltage of the flyback transformer switching power supply circuit to the load through the conduction control module when the first voltage and the second voltage are not zero. At this time, the flyback power supply control chip has been started up, and the auxiliary coil supplies power to the flyback power supply control chip and the load without affecting the normal startup of the flyback power supply control chip. Since there is no need to reduce the series resistance between the primary coil and the power input pin of the flyback power supply control chip, and there is no need to introduce a secondary coil to supply power to the load, there is no problem of increased loss and reduced transformer coil utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure is a circuit connection diagram of a flyback switching power supply startup and conduction control circuit according to an embodiment of the present invention.

[0031] Figure 2 The figure is a circuit connection diagram of a flyback switching power supply startup and conduction control circuit applied to a flyback transformer switching power supply circuit according to an embodiment of the present invention.

[0032] Figure numerals: 101, first voltage detection module; 102, second voltage detection module; 103, conduction control module; R1, first resistor; R2, second resistor; R3, third resistor; D1, diode; C, capacitor; OCEP, optocoupler; R4, fourth resistor; D2, input diode; Q1, output transistor; Q2, NMOS tube; R5, fifth resistor; R6, sixth resistor; Q3, bipolar transistor. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings 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 in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0034] The terms "first," "second," "third," and "fourth," etc., in the specification and claims of this application and the accompanying drawings are used to distinguish between different objects, rather than to describe a specific order. In addition, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements, but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0035] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0036] Flyback transformer switching power supply circuit: refers to a transformer switching power supply that provides power output to the load only after the excitation voltage of the primary coil of the transformer is turned off, while the secondary coil of the transformer does not provide output power to the load when the primary coil of the transformer is excited by a DC pulse voltage.

[0037] The existing AC-to-DC flyback transformer switching power supply circuit is generally composed of a diode rectifier bridge, a bus capacitor, a flyback power supply control chip, a transformer, a diode, and a filter capacitor. If there are other loads in the circuit that share the output voltage generated by the auxiliary coil of the transformer with the flyback power supply control chip for power supply, it is necessary to reduce the resistance of the series resistor between the primary coil and the power input pin of the flyback power supply control chip, otherwise the flyback power supply control chip will not be able to start normally. At the same time, after the resistance of the series resistor is reduced, the loss on the series resistor increases, thereby increasing the heat generation. In order to cope with the sharp increase in the loss on the series resistor, the traditional method uses multiple resistors in parallel and then in series to reduce the loss on a single resistor to reduce heat generation, or by adding an additional transformer secondary coil to power the load. However, the above two methods will result in a significant increase in the volume and weight of the transformer, and adding a secondary coil will reduce the utilization rate of the transformer coil. To this end, an embodiment of the present invention proposes a flyback switching power supply startup and conduction control circuit and device, which provides a first voltage detection module to obtain the grid power output voltage of the flyback transformer switching power supply circuit, that is, the first voltage, and provides a second voltage detection module to obtain the secondary coil output voltage of the flyback transformer switching power supply circuit, that is, the second voltage. When the first voltage and the second voltage are not zero, the auxiliary coil output voltage of the flyback transformer switching power supply circuit is connected to the load through the conduction control module. At this time, the flyback power supply control chip has been started, and the auxiliary coil is used to supply power to the flyback power supply control chip and the load without affecting the normal startup of the flyback power supply control chip. Since there is no need to reduce the resistance of the series resistance between the primary coil and the power input pin of the flyback power supply control chip, and there is no need to introduce a secondary coil to power the load, there is no problem of increased loss and reduced transformer coil utilization.

[0038] On the one hand, if Figure 1 As shown, an embodiment of the present invention provides a flyback switching power supply startup and conduction control circuit, which is applied to a flyback transformer switching power supply circuit, including:

[0039] A first voltage detection module 101 is configured to obtain a first voltage, where the first voltage is a grid power output voltage of a flyback transformer switching power supply circuit;

[0040] A second voltage detection module 102 is used to obtain a second voltage, where the second voltage is the secondary coil output voltage of the flyback transformer switching power supply circuit;

[0041] The conduction control module 103 is used to conduct the auxiliary coil output voltage of the flyback transformer switching power supply circuit to the load when the first voltage and the second voltage are not zero; and is used to disconnect the auxiliary coil output voltage of the flyback transformer switching power supply circuit from the load when the first voltage is zero or the second voltage is zero.

[0042] Reference Figure 2 It can be seen that the grid power supply output voltage of a conventional flyback transformer switching power supply circuit (excluding the flyback switching power supply startup and conduction control circuit) forms a DC bus voltage VBUS after passing through a rectifier bridge. VBUS is connected to the output end of the auxiliary coil through the primary coil of the transformer and a series resistor, providing the initial power supply for the startup of the flyback power supply control chip. After the flyback power supply control chip is started, the secondary coil of the transformer outputs a stable voltage. After the output voltage of the auxiliary coil stabilizes, the flyback power supply control chip is mainly powered by the output voltage of the auxiliary coil. When other loads share the output voltage generated by the auxiliary coil of the transformer with the flyback power supply control chip for power supply, there is a risk that the flyback power supply control chip will not start normally. In an embodiment of the present invention, a flyback switching power supply startup and conduction control circuit is used to control the path between the auxiliary coil output and the load. The grid power supply output voltage of the flyback transformer switching power supply circuit, i.e., the first voltage, is obtained through the first voltage detection module 101. The secondary coil output voltage of the flyback transformer switching power supply circuit, i.e., the second voltage, is obtained through the second voltage detection module 102. When the first voltage or the second voltage is zero, the path between the auxiliary coil output and the load is disconnected; when the first voltage and the second voltage are not zero, it is considered that the flyback power supply control chip has been started, and the path between the auxiliary coil output and the load is turned on, so that the auxiliary coil output supplies power to the load without affecting the startup process of the flyback power supply control chip.

[0043] As an optional implementation, the first voltage detection module 101 includes a voltage dividing module and an anti-reverse connection module;

[0044] The input end of the anti-reverse connection module is used to connect to the grid power output of the flyback transformer switching power supply circuit, the output end of the anti-reverse connection module is connected to the input end of the voltage divider module, and the output end of the voltage divider module is used to output a third voltage, which is the voltage obtained after the first voltage is divided by the voltage divider module.

[0045] As an optional implementation, the anti-reverse connection module includes a diode D1, and the voltage divider module includes a first resistor R1, a second resistor R2, a third resistor R3 and a capacitor C;

[0046] The anode of the diode D1 is used to be connected to the grid power output of the flyback transformer switching power supply circuit, the cathode of the diode D1 is connected to the first end of the first resistor R1, the second end of the first resistor R1 is connected to the first end of the second resistor R2, the second end of the second resistor R2 is connected to the first end of the third resistor R3, the second end of the third resistor R3 is grounded, the second end of the third resistor R3 is also connected to the first end of the capacitor C, and the second end of the capacitor C is connected to the first end of the third resistor R3;

[0047] After being divided by the first resistor R1 , the second resistor R2 , and the third resistor R3 , the first voltage is output as a third voltage at the first end of the third resistor R3 .

[0048] As an optional implementation, the second voltage detection module 102 includes an optical coupler OCEP and a fourth resistor R4;

[0049] The first end of the optocoupler OCEP is used to connect to the secondary coil output of the flyback transformer switching power supply circuit, the second end of the optocoupler OCEP is grounded through the fourth resistor R4, and the fourth end of the optocoupler OCEP is grounded;

[0050] When current flows from the first terminal to the second terminal of the optical coupler OCEP, that is, when the second voltage is not zero, the third terminal and the fourth terminal of the optical coupler OCEP are conductively connected.

[0051] As an optional implementation, the optocoupler OCEP includes an input-end diode D2 and an output-end transistor Q1;

[0052] The anode of the input diode D2 is used to connect to the secondary coil output of the flyback transformer switching power supply circuit, the cathode of the input diode D2 is connected to the first end of the fourth resistor R4, the second end of the fourth resistor R4 is grounded, and the emitter of the output transistor Q1 is grounded.

[0053] As an optional implementation, the input diode D2 is a light emitting diode.

[0054] When current flows from the anode to the cathode of the input diode D2, the input diode D2 is lit and the output transistor Q1 is turned on.

[0055] It can be understood that when the second voltage is zero (the secondary coil output voltage is not formed), the input end diode D2 does not emit light, and at this time the output end transistor Q1 is not turned on; when the second voltage is not zero (the secondary coil output voltage is formed), the input end diode D2 emits light, thereby causing the output end transistor Q1 to be turned on.

[0056] As an optional implementation, the second end of the fourth resistor R4 is connected to the ground of the secondary coil output end of the flyback transformer switching power supply circuit, and the emitter of the output transistor Q1 is connected to the ground of the auxiliary coil output end of the flyback transformer switching power supply circuit.

[0057] As an optional implementation, the conduction control module 103 includes an NMOS transistor Q2, a bipolar transistor Q3, a fifth resistor R5 and a sixth resistor R6;

[0058] The gate of the NMOS transistor Q2 is connected to the first end of the third resistor R3, the source of the NMOS transistor Q2 is connected to the collector of the output transistor Q1, the drain of the NMOS transistor Q2 is connected to the first end of the fifth resistor R5, the second end of the fifth resistor R5 is connected to the base of the bipolar transistor Q3, the base of the bipolar transistor Q3 is connected to the first end of the sixth resistor R6, the second end of the sixth resistor R6 is connected to the emitter of the bipolar transistor Q3, the emitter of the bipolar transistor Q3 is connected to the auxiliary coil output of the flyback transformer switching power supply circuit, and the collector of the bipolar transistor Q3 is used to connect to the load of the flyback transformer switching power supply circuit.

[0059] As can be seen from the foregoing, when the second voltage is zero (the secondary coil output voltage is not formed), the input diode D2 does not emit light, and the output transistor Q1 is not conducting. When the second voltage is not zero (the secondary coil output voltage is formed), the input diode D2 emits light, thereby conducting the output transistor Q1. In other words, when the second voltage is zero, the source of the NMOS transistor is not connected to ground; when the second voltage is not zero, the source of the NMOS transistor is connected to ground.

[0060] It can be understood that when the first voltage is zero (the grid power supply does not output voltage), the first voltage is divided by the first resistor R1, the second resistor R2 and the third resistor R3 of the first voltage detection module 101 and outputs a low level to the gate of the NMOS tube Q2, and the NMOS tube Q2 is not turned on; when the first voltage is not zero (the grid power supply outputs voltage), the first voltage is divided by the first resistor R1, the second resistor R2 and the third resistor R3 of the first voltage detection module 101 and outputs a high level to the gate of the NMOS tube Q2, and the NMOS tube Q2 is turned on.

[0061] It is understood that when the first voltage and the second voltage are non-zero, the NMOS transistor Q2 and the output transistor Q1 are conductive, and the drain of the NMOS transistor is connected to ground. That is, the auxiliary coil output is connected to ground via the sixth resistor R6, the fifth resistor R5, the NMOS transistor Q2, and the output transistor Q1. At this time, the output voltage of the auxiliary coil is divided by the sixth resistor R6 and the fifth resistor R5, causing the emitter and collector of the bipolar transistor Q3 to be conductive. That is, the output voltage of the auxiliary coil is connected to the load, supplying power to the load. When the first voltage or the second voltage is zero, the path from the auxiliary coil output to ground via the sixth resistor R6, the fifth resistor R5, the NMOS transistor Q2, and the output transistor Q1 is disconnected, resulting in the emitter and collector of the bipolar transistor Q3 being disconnected. That is, the output voltage of the auxiliary coil does not supply power to the load.

[0062] On the other hand, an embodiment of the present invention provides a flyback switching power supply startup and conduction control device, comprising the flyback switching power supply startup and conduction control circuit described above.

[0063] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A flyback switching power supply startup and conduction control circuit, applied to a flyback transformer switching power supply circuit, characterized in that: include: A first voltage detection module is used to obtain a first voltage, where the first voltage is the grid power output voltage of the flyback transformer switching power supply circuit; A second voltage detection module is used to obtain a second voltage, where the second voltage is the secondary coil output voltage of the flyback transformer switching power supply circuit; a conduction control module, configured to conduct the auxiliary coil output voltage of the flyback transformer switching power supply circuit to a load when the first voltage and the second voltage are not zero; Used to disconnect the auxiliary coil output voltage of the flyback transformer switching power supply circuit from the load when the first voltage is zero or the second voltage is zero.

2. A flyback switching power supply startup and conduction control circuit according to claim 1, characterized in that: The first voltage detection module includes a voltage dividing module and an anti-reverse connection module; The input end of the anti-reverse connection module is used to connect to the grid power output of the flyback transformer switching power supply circuit, the output end of the anti-reverse connection module is connected to the input end of the voltage divider module, and the output end of the voltage divider module is used to output a third voltage, which is the voltage obtained after the first voltage is divided by the voltage divider module.

3. The flyback switching power supply startup and conduction control circuit according to claim 2, characterized in that: The anti-reverse connection module includes a diode, and the voltage divider module includes a first resistor, a second resistor, a third resistor and a capacitor; The anode of the diode is used to be connected to the grid power output of the flyback transformer switching power supply circuit, the cathode of the diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the second resistor, the second end of the second resistor is connected to the first end of the third resistor, the second end of the third resistor is grounded, the second end of the third resistor is also connected to the first end of the capacitor, and the second end of the capacitor is connected to the first end of the third resistor; The first voltage is divided by the first resistor, the second resistor, and the third resistor, and then output as the third voltage at the first end of the third resistor.

4. The flyback switching power supply startup and conduction control circuit according to claim 3, characterized in that: The second voltage detection module includes an optocoupler and a fourth resistor; The first end of the optocoupler is used to connect to the secondary coil output of the flyback transformer switching power supply circuit, the second end of the optocoupler is grounded through the fourth resistor, and the fourth end of the optocoupler is grounded; When current flows from the first end to the second end of the optical coupler, the third end and the fourth end of the optical coupler are conductive.

5. The flyback switching power supply startup and conduction control circuit according to claim 4, characterized in that: The optical coupler includes an input-end diode and an output-end transistor; The anode of the input-end diode is used to connect to the secondary coil output of the flyback transformer switching power supply circuit, the cathode of the input-end diode is connected to the first end of the fourth resistor, the second end of the fourth resistor is grounded, and the emitter of the output-end transistor is grounded.

6. The flyback switching power supply startup and conduction control circuit according to claim 5, characterized in that: The input end diode is a light emitting diode; When current flows from the anode to the cathode of the input-end diode, the input-end diode is lit and the output-end transistor is turned on.

7. The flyback switching power supply startup and conduction control circuit according to claim 5, characterized in that: The second end of the fourth resistor is connected to the ground of the output end of the secondary coil of the flyback transformer switching power supply circuit, and the emitter of the output transistor is connected to the ground of the output end of the auxiliary coil of the flyback transformer switching power supply circuit.

8. The flyback switching power supply startup and conduction control circuit according to claim 7, characterized in that: The conduction control module includes an NMOS tube, a bipolar transistor, a fifth resistor and a sixth resistor; The gate of the NMOS tube is connected to the first end of the third resistor, the source of the NMOS tube is connected to the collector of the output transistor, the drain of the NMOS tube is connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the base of the bipolar transistor, the base of the bipolar transistor is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the emitter of the bipolar transistor, the emitter of the bipolar transistor is connected to the auxiliary coil output of the flyback transformer switching power supply circuit, and the collector of the bipolar transistor is used to connect the load of the flyback transformer switching power supply circuit.

9. A flyback switching power supply startup and conduction control device, characterized in that: It comprises the flyback switching power supply startup and conduction control circuit as described in any one of claims 1 to 8.

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