Magnetic feedback circuit suitable for converter

Abstract

The utility model discloses a magnetic feedback circuit suitable for a converter, comprising a PWM controller and an amplifier EA which are connected with a magnetic isolation feedback circuit, the magnetic isolation feedback circuit comprises a magnetic feedback transformer, a switch device and a bidirectional circuit; the bidirectional circuit is respectively connected with a secondary coil of the magnetic feedback transformer and the switching device, and the bidirectional circuit is also connected with a positive pole input end of the amplifier EA; compared with an existing forward magnetic feedback circuit, the power supply voltage of the secondary signal circuit is provided by the magnetic feedback transformer, the power supply voltage is not influenced by the output voltage, and normal work can still be kept.

Description

Technical Field

[0001] This utility model relates to the field of power supply circuit technology, and specifically to a magnetic feedback circuit suitable for converters. Background Technology

[0002] Switching power supplies and DC / DC converters, which serve as secondary power supplies for systems, are widely used in electronic, communication, and industrial automation equipment. Currently, the most widely used isolation feedback methods are optocoupler isolation feedback and magnetic isolation feedback.

[0003] However, optocouplers are not suitable for scenarios with wide temperature ranges and high dynamic characteristics; magnetic feedback is widely used in power supply design due to its advantages such as high reliability, good temperature stability, strong radiation resistance and long service life.

[0004] Currently, forward magnetic feedback and direct-coupled magnetic feedback are commonly used. While direct-coupled magnetic feedback circuits are simple and easy to implement, their control accuracy is low. Although forward magnetic feedback circuits offer superior control accuracy, they require additional auxiliary circuitry, and... Figure 1 As shown, the power supply voltage of the secondary signal circuit is generally taken from the output voltage. When the DC / DC overcurrent protection or short circuit protection is activated, the output voltage will decrease, causing the secondary signal circuit to malfunction. Utility Model Content

[0005] In view of the deficiencies in the prior art, this utility model provides a magnetic feedback circuit suitable for converters to solve the technical problems mentioned in the background art.

[0006] This utility model provides a magnetic feedback circuit suitable for converters, including a PWM controller and an amplifier EA connected to the magnetic isolation feedback circuit. The magnetic isolation feedback circuit includes a magnetic feedback transformer, a switching device, and a bidirectional circuit. The bidirectional circuit is connected to the secondary coil of the magnetic feedback transformer and the switching device, respectively, and is also connected to the positive input terminal of the amplifier EA.

[0007] Furthermore, the bidirectional circuit includes a first diode, a second diode, a third diode, a fourth diode, a first resistor, and a second resistor;

[0008] One end of the secondary coil, the first diode, the first resistor, and the second resistor are connected in sequence and then connected to the switching device; the common point of the first resistor and the second resistor is connected to the positive input terminal of the amplifier EA;

[0009] The other end of the secondary coil is also connected to the anode of the second diode and the cathode of the fourth diode, respectively. The cathode of the second diode is connected to the switching device. The anode of the fourth diode is connected to ground and the anode of the third diode, respectively. The cathode of the third diode is connected to one end of the secondary coil.

[0010] Furthermore, the first diode and the first resistor are grounded through capacitor C3.

[0011] Furthermore, the switching device is a transistor, specifically a PNP transistor.

[0012] Furthermore, a fifth diode is also deployed between the PWM controller and the primary coil of the magnetic feedback transformer. The anode of the fifth diode is connected to the PWM controller, and the cathode of the fifth diode is connected to the primary coil of the magnetic feedback transformer.

[0013] Furthermore, the anode of the fifth diode is also connected to another capacitor C2.

[0014] Furthermore, the primary and secondary coils of the magnetic feedback transformer have the same number of turns.

[0015] Furthermore, the first diode, the second diode, the third diode, the fourth diode, and the fifth diode are all high-speed switching diodes, and the model number is 1N4148.

[0016] The beneficial effects of this utility model are reflected in:

[0017] This invention provides a magnetic feedback circuit suitable for converters. By constructing a bidirectional circuit in the secondary coil of the magnetic feedback transformer, the forward and flyback modes of the magnetic feedback transformer are switched by using four diodes that alternately conduct within one cycle. In the forward mode, the secondary coil provides a power supply voltage to the subsequent connected secondary signal circuit.

[0018] Compared with existing forward magnetic feedback circuits, the secondary signal circuit is supplied with the power supply voltage by the magnetic feedback transformer. When the DC / DC converter is in an overcurrent or short-circuit state, the power supply voltage is not affected by the output voltage and can still maintain normal operation. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. Other drawings will be readily available to those skilled in the art based on these drawings without any inventive effort.

[0021] Figure 1 A schematic diagram of a forward magnetic feedback circuit provided for the prior art;

[0022] Figure 2 This invention provides a magnetic feedback circuit suitable for converters. Detailed Implementation

[0023] The embodiments of this technical solution will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative and should not be construed as limiting the scope of protection of this utility model.

[0024] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0025] In the description of this application, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly defined.

[0026] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] like Figure 1 As shown, the prior art provides a forward magnetic feedback circuit, where the power supply voltage of the secondary signal circuit (including the secondary operational amplifier, i.e., amplifier EA) is generally taken from the output voltage. Figure 1 VCC is used to represent this and supplies power to the corresponding amplifier EA.

[0028] refer to Figure 2The present invention provides a magnetic feedback circuit suitable for converters, including a PWM controller and an amplifier EA connected to the magnetic isolation feedback circuit. The magnetic isolation feedback circuit includes a magnetic feedback transformer, a switching device, and a bidirectional circuit. The bidirectional circuit is connected to the secondary coil of the magnetic feedback transformer and the switching device, respectively, and is also connected to the positive input terminal of the amplifier EA.

[0029] In this embodiment, the magnetic feedback transformer is represented by T2; the bidirectional circuit includes a first diode, a second diode, a third diode, a fourth diode, a first resistor, and a second resistor;

[0030] One end of the secondary coil, the first diode, the first resistor, and the second resistor are connected in sequence and then connected to the switching device; the common point of the first resistor and the second resistor is connected to the positive input terminal of the amplifier EA;

[0031] The other end of the secondary coil is also connected to the anode of the second diode and the cathode of the fourth diode, respectively. The cathode of the second diode is connected to the switching device. The anode of the fourth diode is connected to ground and the anode of the third diode, respectively. The cathode of the third diode is connected to one end of the secondary coil.

[0032] Specifically, the primary and secondary coils of the magnetic feedback transformer have the same number of turns; that is, the turns ratio is 1:1; the switching device is a transistor, represented by Q3 in the figure, and is a PNP type transistor; in application, the cathode of the second diode is connected to the emitter of the switching device, the base is connected to the output terminal of the amplifier EA, and the collector of the switching device is connected to the output terminal.

[0033] In this embodiment, the first diode and the first resistor are also grounded through capacitor C3;

[0034] A fifth diode is also deployed between the PWM controller and the primary coil of the magnetic feedback transformer. The anode of the fifth diode is connected to the PWM controller, and the cathode of the fifth diode is connected to the primary coil of the magnetic feedback transformer.

[0035] The anode of the fifth diode is also connected to another capacitor C2; the first, second, third, fourth and fifth diodes are all high-speed switching diodes, and the model is 1N4148; the first diode is represented by D1, the second diode by D2, and so on, and the fifth diode by D5, and so on.

[0036] To better understand this technical solution, its working principle is as follows:

[0037] When transistor Q2 is turned on, the voltage of the primary winding of the magnetic feedback transformer is positive, diode D5 is cut off, secondary diodes D2 and D3 are cut off, and D1 and D4 are turned on. T2 works in forward mode, and the primary side transfers energy to the secondary side to provide power supply voltage for the secondary signal circuit.

[0038] When transistor Q2 is turned off, the magnetic feedback transformer begins to demagnetize, the primary winding voltage is negative, diode D5 is turned on, secondary diodes D2 and D3 are turned on, D1 and D4 are turned off, and T2 operates in flyback mode.

[0039] The above scheme constructs a bidirectional circuit in the secondary coil of the magnetic feedback transformer and uses four diodes to alternately conduct within one cycle to achieve the switching between forward and flyback modes of the magnetic feedback transformer; and in the forward operating mode, the secondary coil provides power supply voltage to the subsequently connected secondary signal circuit.

[0040] Compared with existing forward magnetic feedback circuits, the secondary signal circuit is supplied with the power supply voltage by the magnetic feedback transformer. When the DC / DC converter is in an overcurrent or short-circuit state, the power supply voltage is not affected by the output voltage and can still maintain normal operation.

[0041] Finally, it should be noted that the technical features of the technical solution of this application can be combined arbitrarily. In order to simplify the description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0042] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A magnetic feedback circuit suitable for a converter, comprising a PWM controller and an amplifier EA connected to the magnetic feedback circuit, characterized in that, The magnetic feedback circuit includes a magnetic feedback transformer, a switching device, and a bidirectional circuit; the bidirectional circuit is connected to the secondary coil of the magnetic feedback transformer and the switching device, respectively, and is also connected to the positive input terminal of the amplifier EA.

2. The magnetic feedback circuit suitable for converters according to claim 1, characterized in that: The bidirectional circuit includes a first diode, a second diode, a third diode, a fourth diode, a first resistor, and a second resistor; One end of the secondary coil, the first diode, the first resistor, and the second resistor are connected in sequence and then connected to the switching device; the common point of the first resistor and the second resistor is connected to the positive input terminal of the amplifier EA; The other end of the secondary coil is also connected to the anode of the second diode and the cathode of the fourth diode, respectively. The cathode of the second diode is connected to the switching device. The anode of the fourth diode is connected to ground and the anode of the third diode, respectively. The cathode of the third diode is connected to one end of the secondary coil.

3. A magnetic feedback circuit suitable for converters according to claim 2, characterized in that: The first diode and the first resistor are also grounded through capacitor C3.

4. A magnetic feedback circuit suitable for converters according to claim 2, characterized in that: The switching device is a transistor, specifically a PNP transistor.

5. A magnetic feedback circuit suitable for a converter according to claim 3, characterized in that: A fifth diode is also deployed between the PWM controller and the primary coil of the magnetic feedback transformer. The anode of the fifth diode is connected to the PWM controller, and the cathode of the fifth diode is connected to the primary coil of the magnetic feedback transformer.

6. A magnetic feedback circuit suitable for a converter according to claim 5, characterized in that: The anode of the fifth diode is also connected to another capacitor C2.

7. A magnetic feedback circuit suitable for a converter according to claim 6, characterized in that: The primary and secondary coils of the magnetic feedback transformer have the same number of turns.

8. A magnetic feedback circuit suitable for a converter according to claim 7, characterized in that: The first diode, the second diode, the third diode, the fourth diode, and the fifth diode are all high-speed switching diodes, and the model number is 1N4148.

Images