Isolation voltage reduction module for primary side feedback

Abstract

The utility model discloses an isolation step-down module for primary side feedback. The isolation step-down module comprises a power supply chip, a transformer, a first resistor, a first capacitor, a first diode, an mos tube, a second diode, a first filtering module, a second filtering module and an output impedance. The transformer comprises a primary winding, an auxiliary winding and a secondary winding; the first end of the primary winding is grounded through the mos tube; the grid electrode of the mos tube is connected with the output end of the power supply chip; a first triode, a second triode and a second resistor are arranged on a line through which the grid electrode of the mos tube is connected with the power supply chip; the collector of the first triode is connected with the vcc interface, the emitter of the second triode is grounded, and the bases of the first triode and the second triode are connected with the output end of the power supply chip; one end of the second resistor is connected with the emitter of the first triode and the collector of the second triode, and the other end is connected with the output end of the power supply chip. According to the utility model, the isolation step-down module and the primary side feedback circuit are adopted, so that the circuit complexity and cost are reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of step-down modules, and in particular to an isolated step-down module with primary-side feedback. Background Art

[0002] Nowadays, there are many types of switches on the market, but most of them adopt non-isolated design, which is basically fine in most scenarios. However, it is not suitable for harsh and complex environments (such as frequent lightning strikes, static electricity, and unstable voltage). If a conventional non-isolated switch is used, it may not work properly. However, according to the normal isolated design of the switch, the conventional isolation design is composed of power control chip, isolation transformer, optocoupler, three-terminal voltage regulator, etc., and the design cost is relatively high. Utility Model Content

[0003] The technical problem to be solved by the present invention is to provide an isolated buck module with primary-side feedback, which adopts the isolated buck module and the primary-side feedback circuit to reduce circuit complexity and cost.

[0004] In order to solve the above technical problems, the utility model discloses an isolated step-down module with primary-side feedback, comprising a power supply chip, a transformer, a first resistor, a first capacitor, a first diode, a MOS tube, a second diode, a first filter module, a second filter module and an output impedance; the transformer comprises a primary winding, an auxiliary winding and a secondary winding; a first filter module is provided on the line from the power input to the primary winding; the first end of the primary winding passes through the first diode and the first resistor in sequence and then is connected to the second end of the primary winding, and the first resistor is connected in parallel with the first capacitor; the first end of the primary winding is grounded through the MOS tube; the gate of the MOS tube is connected to the output end of the power supply chip; the secondary winding is first connected to the second diode to achieve rectification, and then is connected to the second filter module and the output impedance in sequence; the third end of the auxiliary winding is grounded, and its fourth end is connected to the VCC interface after passing through a diode and a resistor, and the VCC interface is connected to the power input end of the power supply chip;

[0005] In which, a first transistor, a second transistor and a second resistor are also provided on the circuit in which the gate of the MOS tube is connected to the power chip; the collector of the first transistor is connected to the VCC interface, the emitter of the second transistor is grounded, and the bases of the first transistor and the second transistor are connected to the output end of the power chip; one end of the second resistor is connected to the emitter of the first transistor and the collector of the second transistor, and the other end thereof is connected to the output end of the power chip; the first transistor is an NPN transistor, and the second transistor is a PNP transistor.

[0006] As an optional embodiment, it also includes a second capacitor, a third capacitor, a third resistor and a fourth resistor; the first end of the primary winding is grounded via the second capacitor and the third resistor in sequence, and the first end of the primary winding is also grounded via the third capacitor and the fourth resistor in sequence.

[0007] As another optional implementation, the fourth end of the auxiliary winding is grounded via a fifth resistor and a sixth resistor in sequence; and the feedback end of the power chip is connected to the line between the fifth resistor and the sixth resistor.

[0008] As another optional implementation, it further includes a fourth capacitor and a seventh resistor; the fourth capacitor and the seventh resistor are connected in series and then in parallel with the second diode.

[0009] As another optional implementation manner, the MOS tube is an n-type MOS tube.

[0010] As another optional implementation, the power input terminal of the power chip is grounded via a capacitor.

[0011] As another optional embodiment, it also includes an eighth resistor and a ninth resistor, a line is led out between the first filter module and the primary winding, passes through the eighth resistor and the ninth resistor in sequence and is grounded, and the enable end of the power supply chip is connected to the line between the eighth resistor and the ninth resistor.

[0012] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0013] Compared with the conventional isolation design that uses an optocoupler and a three-terminal voltage regulator as back-end feedback, the embodiment of the utility model adopts an isolated step-down module and a primary-side feedback circuit, which reduces circuit complexity and cost; by forming a push-pull circuit with two transistors, wherein the input end of the push-pull circuit is connected to the output end of the power supply chip, and the output end of the push-pull circuit is connected to the gate of the MOS tube, the control accuracy of the power supply chip is improved by the push-pull circuit; when the stored electric energy is released after the primary winding is powered off, the primary winding forms an energy dissipation loop through the first diode and the resistor, and the electric energy released by the primary winding is consumed by the resistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1This is a circuit structure diagram of a primary-side feedback isolated buck module disclosed in an embodiment of the present utility model. DETAILED DESCRIPTION

[0016] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0017] See also Figure 1 The present invention discloses an isolated step-down module with primary-side feedback, comprising a power supply chip U1, a transformer T1, a first resistor R1, a first capacitor C1, a first diode D2, a MOSFET Q3, a second diode D1, a first filter module, a second filter module, and an output impedance. The transformer comprises a primary winding, an auxiliary winding, and a secondary winding. A first filter module is provided on the line from the power input to the primary winding. The first end of the primary winding passes through the first diode D2 and the first resistor R1 in sequence and then connects to the second end of the primary winding. The first resistor R1 is connected in parallel with the first capacitor C1. The first end of the primary winding is grounded via the MOSFET Q3. The gate of the MOSFET Q3 is connected to the output end of the power supply chip U1. The secondary winding is first connected to the second diode D1 for rectification and then connected to the second filter module and the output impedance in sequence. The third end of the auxiliary winding is grounded, and the fourth end thereof is connected to a VCC interface via a diode D4 and a resistor R19. The VCC interface is connected to the power input terminal VCC of the power supply chip U1.

[0018] The gate of the MOSFET Q3 is connected to the power chip U1, and a first transistor Q1, a second transistor Q2, and a second resistor R12 are also provided on the circuit. The collector of the first transistor Q1 is connected to the VCC interface, the emitter of the second transistor Q2 is grounded, and the bases of the first transistor Q1 and the second transistor Q2 are connected to the output terminal of the power chip U1. One end of the second resistor R12 is connected to the emitter of the first transistor Q1 and the collector of the second transistor Q2, and the other end is connected to the output terminal GATE of the power chip U1. The first transistor Q1 is an NPN transistor, and the second transistor Q2 is a PNP transistor. The existing filter module usually consists of two or more capacitors connected in parallel.

[0019] Compared with the conventional isolation design that uses an optocoupler and a three-terminal voltage regulator as back-end feedback, the embodiment of the utility model adopts an isolated step-down module and a primary-side feedback circuit, which reduces the circuit complexity and cost; by forming a push-pull circuit with two transistors, wherein the input end of the push-pull circuit is connected to the output end GATE of the power chip U1, and the output end of the push-pull circuit is connected to the gate of the MOSFET Q3, the control accuracy of the power chip U1 is improved by the push-pull circuit; when the stored electric energy is released after the primary winding is powered off, the primary winding forms an energy dissipation circuit through the first diode D2 and the resistor R1, and the electric energy released by the primary winding is consumed by the resistor R1.

[0020] In an optional embodiment, the present invention further includes a second capacitor C8, a third capacitor C9, a third resistor R9 and a fourth resistor R10; the first end of the primary winding is grounded via the second capacitor C8 and the third resistor R9 in sequence, and the first end of the primary winding is also grounded via the third capacitor C9 and the fourth resistor R10 in sequence, and a protection winding is set by resistors and capacitors.

[0021] In another optional embodiment, the fourth end of the auxiliary winding is grounded via the fifth resistor R15 and the sixth resistor R21 in sequence; the feedback end FB of the power chip U1 is connected to the line between the fifth resistor R15 and the sixth resistor R21 to obtain a feedback signal for feedback control of the power chip U1.

[0022] In another optional embodiment, a fourth capacitor C2 and a seventh resistor R3 are further included; the fourth capacitor C2 and the seventh resistor R3 are connected in series and then in parallel with the second diode D1 to achieve surge absorption.

[0023] In another optional embodiment, the MOS transistor Q3 is an n-type MOS transistor Q3.

[0024] In yet another optional embodiment, the power input terminal VCC of the power chip U1 is grounded via a capacitor C11.

[0025] In another optional embodiment, an eighth resistor R11 and a ninth resistor R13 are further included, a line is led out between the first filter module and the primary winding, and passes through the eighth resistor R11 and the ninth resistor R13 in sequence to be grounded, and the enable terminal EN of the power supply chip U1 is connected to the line between the eighth resistor R11 and the ninth resistor R13.

[0026] It should be noted that when the DC input voltage range is within 8V-80V, the DC voltage will first pass through the three filter capacitors EC1, C6, and C7, and the third pin EN (enable pin) of the power supply chip will be divided by the series resistors R11 and R13 to obtain a driving voltage (about 2.3V). This is also the time to detect whether the voltage meets the requirements (if the voltage is less than 2.3V after the voltage is divided by resistors R11 and R13, the power supply chip will not start); after the power supply chip completes sampling, the DC voltage will reach the isolation transformer part. At this time, the transformer starts to store energy through the input current change. After the energy storage is completed (the input current is stable), After that, the power chip will first output a high level to drive the MOS tube Q3 to turn on. After the MOS tube is turned on, the transformer begins to release energy, and the transformer with the same core but different windings begins to store energy (including primary winding N1, auxiliary winding N2 and secondary winding N3; auxiliary winding N2 is the power supply winding for the power chip VCC and also the feedback winding; secondary winding N3 is responsible for outputting a stable 12V DC voltage). At this time, the N2 and N3 windings repeatedly store and release energy through the transformer. The changes in the voltage and current of the N2 winding will be fed back to the power chip to adjust the duty cycle of the MOS tube (the ratio of the on and off time) to control the stability of the output power. The N3 winding senses the energy changes of the primary winding N1 through coupling, so that it has sufficient energy to meet the power supply of the back-end load. When the primary winding N1 starts to charge (the switching MOS tube is closed), the N3 and N2 windings start to discharge (release energy). At this time, the N3 winding is rectified by a Schottky diode D1, and then filtered out by EC2, C3, C4, and C5 to remove the noise. The back-end obtains a stable 12V DC stable power supply. C2 and R3 in parallel with the rectifier diode D1 are used to absorb the voltage spikes during charging and discharging. When the N1 winding changes energy in the primary winding through the on / off switching of the MOS transistor Q3, the N2 and N3 windings also experience energy changes (corresponding to the voltage and current on the windings). Because the N2 and N3 windings are both secondary windings, the changes in the voltage and current of the N2 winding can equivalently feedback the changes in the voltage and current of the N3 winding. At this time, part of the changing voltage and current on the N2 winding is fed back to the power chip through the voltage divider of resistors R15 and R21. The power chip adjusts the duty cycle of the MOS switch according to the information fed back from the N2 winding to ensure the stability of the voltage and current on the N3 winding. The other part provides a stable voltage to the power chip through the rectifier diode D4, current-limiting resistor R19, and filter capacitors C12 and C14 to ensure normal operation of the power chip.

[0027] The contents disclosed in the embodiments of the present invention only disclose preferred embodiments of the present invention, which are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A primary-side feedback isolated step-down module, comprising a power supply chip, a transformer, a first resistor, a first capacitor, a first diode, a MOSFET, a second diode, a first filter module, a second filter module, and an output impedance; the transformer comprises a primary winding, an auxiliary winding, and a secondary winding; a first filter module is provided on the line from the power input to the primary winding; a first end of the primary winding passes through the first diode and the first resistor in sequence and then connects to the second end of the primary winding, the first resistor being connected in parallel with the first capacitor; the first end of the primary winding is grounded via the MOSFET; the gate of the MOSFET is connected to the output end of the power supply chip; the secondary winding is first connected to the second diode for rectification and then sequentially connected to the second filter module and the output impedance; a third end of the auxiliary winding is grounded, and a fourth end thereof is connected to a VCC interface via a diode and a resistor, and the VCC interface is connected to the power input end of the power supply chip; It is characterized by: A first transistor, a second transistor and a second resistor are also provided on the circuit in which the gate of the MOS tube is connected to the power supply chip; the collector of the first transistor is connected to the VCC interface, the emitter of the second transistor is grounded, and the bases of the first transistor and the second transistor are connected to the output end of the power supply chip; one end of the second resistor is connected to the emitter of the first transistor and the collector of the second transistor, and the other end thereof is connected to the output end of the power supply chip; the first transistor is an NPN transistor, and the second transistor is a PNP transistor.

2. The isolation and voltage reduction module according to claim 1, wherein: It also includes a second capacitor, a third capacitor, a third resistor and a fourth resistor; the first end of the primary winding is grounded via the second capacitor and the third resistor in sequence, and the first end of the primary winding is also grounded via the third capacitor and the fourth resistor in sequence.

3. The isolation and step-down module according to claim 1, characterized in that: The fourth end of the auxiliary winding is grounded via a fifth resistor and a sixth resistor in sequence; the feedback end of the power chip is connected to the line between the fifth resistor and the sixth resistor.

4. The isolation and voltage reduction module according to claim 1, wherein: It also includes a fourth capacitor and a seventh resistor; the fourth capacitor and the seventh resistor are connected in series and then in parallel with the second diode.

5. The isolation and step-down module according to claim 1, characterized in that: The MOS tube is an n-type MOS tube.

6. The isolation and step-down module according to claim 1, characterized in that: The power input terminal of the power chip is grounded via a capacitor.

7. The isolation and voltage reduction module according to claim 1, wherein: It also includes an eighth resistor and a ninth resistor. A line is drawn between the first filter module and the primary winding and passes through the eighth resistor and the ninth resistor in sequence to be grounded. The enable end of the power supply chip is connected to the line between the eighth resistor and the ninth resistor.

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