Overvoltage protection circuit of PSR power supply architecture and switching power supply

Abstract

The utility model relates to the related technical field of switching power supplies, and provides an overvoltage protection circuit of a PSR power supply architecture and a switching power supply, a PSR circuit is adopted as an output voltage control circuit, and the PSR circuit comprises a first resistance circuit and a second resistance circuit. The resistance ratio of the first resistance circuit to the second resistance circuit is used for determining the output voltage of the switching power supply; and the second resistor circuit adopts a structure in which a plurality of resistors are connected in series. By improving the structure of the second resistance circuit, the second resistance circuit is improved into a structure in which a plurality of resistors are connected in series, so that the probability that the output resistance of the second resistance circuit is zero is reduced, the overvoltage protection function of the output voltage control circuit, namely the PSR circuit, is realized, and the overvoltage output of the switching circuit is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, and in particular to an overvoltage protection circuit and a switching power supply of a PSR power supply architecture. Background Art

[0002] The statements in this section merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] The flyback topology circuit in the switching power supply is mainly used to output low-power circuits. The control methods mainly include the use of SSR circuit and PSR circuit. The SSR circuit is a voltage stabilization circuit with secondary side feedback, and the PSR voltage stabilization control circuit is a voltage stabilization circuit based on primary side feedback, that is, the voltage feedback point is on the primary side circuit.

[0004] The inventor discovered during research that the existing PSR power supply topology output voltage mode simulates a single failure of a component on the PSR power supply control circuit board during a product reliability overvoltage (OVP) test. When a short circuit occurs at the failed component, the output voltage of the switching power supply will be too high. The excessively high output voltage will cause damage to the electrical products powered by the switching power supply. Utility Model Content

[0005] In order to solve the above problems, the utility model proposes an overvoltage protection circuit and a switching power supply of a PSR power supply architecture, which can control the magnitude of the output voltage to prevent the output voltage from being too high and damaging the powered electrical equipment.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] One or more embodiments provide an overvoltage protection circuit of a PSR power supply architecture, using a PSR circuit as an output voltage control circuit, the PSR circuit includes a first resistance circuit and a second resistance circuit, the resistance ratio of the first resistance circuit to the second resistance circuit is used to determine the output voltage of the switching power supply; the second resistance circuit adopts a structure of multiple resistors connected in series.

[0008] One or more embodiments provide a switching power supply, wherein a voltage control circuit of the switching power supply adopts an overvoltage protection circuit of the above-mentioned PSR power supply architecture.

[0009] Compared with the prior art, the beneficial effects of the utility model are:

[0010] The utility model improves the structure of the second resistance circuit to a structure in which a plurality of resistances are connected in series, thereby reducing the probability that the output resistance of the second resistance circuit is zero, realizing the overvoltage protection function of the output voltage control circuit, namely the PSR circuit, and avoiding overvoltage output of the switch circuit.

[0011] The advantages of the present invention and additional advantages will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute a limitation on the present invention.

[0013] Figure 1 This is a switching power supply circuit diagram of Embodiment 2 of the present utility model;

[0014] Figure 2 is a circuit diagram of an overvoltage protection circuit of a PSR power supply architecture according to Embodiment 1 of the present utility model;

[0015] Figure 3 It is the input rectifier filter circuit of embodiment 2 of the utility model;

[0016] Figure 4 This is the circuit of the transformer primary side connection of Embodiment 2 of the present utility model;

[0017] Figure 5 This is the output rectifier and filter circuit of Embodiment 2 of the utility model;

[0018] Figure 6 It is the output voltage control circuit diagram of the traditional switching power supply described in Example 2 of the utility model. DETAILED DESCRIPTION

[0019] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0020] It should be noted that the following detailed descriptions are exemplary and are intended to provide further description of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0021] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the utility model. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0022] In the technical solutions disclosed in one or more embodiments, Figures 1 to 6As shown, an overvoltage protection circuit of a PSR power supply architecture adopts a PSR circuit as an output voltage control circuit; the PSR circuit includes a first resistance circuit and a second resistance circuit, and the resistance ratio of the first resistance circuit to the second resistance circuit is used to determine the output voltage of the switching power supply; the second resistance circuit adopts a structure of multiple resistors connected in series, so that when a single element of the second resistance circuit has a short circuit fault, it will not cause the output voltage to tend to infinity.

[0023] In this embodiment, by improving the structure of the second resistance circuit, the second resistance circuit is improved into a structure of multiple resistors connected in series, thereby reducing the probability that the output resistance of the second resistance circuit is zero, and realizing the overvoltage protection function of the output voltage control circuit, namely the PSR circuit, to avoid overvoltage output of the switching circuit.

[0024] In one achievable implementation manner, the first resistance circuit may be configured as a variable resistor, a series-parallel circuit of multiple resistors, or a circuit of a single resistor;

[0025] Specifically, in this embodiment, the first resistor circuit is provided with a single resistor R4, and the resistance value is set to a fixed value; the first resistor circuit is used to provide an upper bias resistor Rup of the PSR circuit.

[0026] In a feasible implementation, the second resistance circuit includes a resistance branch composed of a plurality of resistors connected in series, and a capacitance branch composed of a plurality of capacitors connected in series; the resistance branch and the capacitance branch are connected in parallel;

[0027] The resistance value and number of the resistors in the resistor branch can be set according to the output voltage; the capacitor branch has at least two capacitors connected in series;

[0028] Specifically, in this embodiment, the resistor branch is provided with 5 resistors, including resistors R5A, R5B, R5C, R5D and R5E connected in series in sequence, for providing a lower bias resistor Rdown of the PSR circuit;

[0029] In the event that any component of the second resistance circuit fails, Rdown will not tend to zero, and the problem of excessive output voltage will not occur. In addition, the maximum value of the output overvoltage can be adjusted by adjusting the number of Rdown resistors connected in series.

[0030] In a specific embodiment, the resistance value of each resistor branch is equal, and the number of series resistors N is used to adjust the maximum output voltage (OVP) in the failure mode; when any resistor fails: 0→∞ or ∞→0, the circuit's minimum down-bias resistance is R*(N-1), and by setting the size of N, the down-bias resistance Rdown always changes between R*(N-1)-∞, and the down-bias resistance Rdown will not be very small, resulting in the output voltage in the failure mode exceeding the set overvoltage value. In this single failure mode, the power supply output will not generate an excessively high voltage, thereby avoiding abnormal damage to electrical appliances;

[0031] In this embodiment, "∞" represents infinity;

[0032] Specifically, in this embodiment, the capacitor branch is provided with two capacitors, including a capacitor C4A and a capacitor C4B connected in series in sequence. The capacitor branch is used as a bypass capacitor to effectively prevent signal interference.

[0033] To achieve output voltage control, the PSR circuit further includes a switch circuit, and the first resistance circuit and the second resistance circuit are respectively connected to the switch circuit;

[0034] In this embodiment, the switch circuit is configured as a main control chip U1 with a built-in switch tube, the model of which may be Silicon Power SP2689AHF, and the built-in switch tube is a MOS tube;

[0035] Specifically, the main control chip U1 includes pin D, pin S, sampling voltage pin Vref, power supply VCC pin and ground pin GND; pin D is connected to the drain of the built-in switch tube, and pin S is connected to the source of the built-in switch tube; the sampling voltage pin Vref is connected to the first resistance circuit and the second resistance circuit as a sampling point; the power supply VCC pin is connected to the secondary coil Na of the transformer of the switching power supply; pin S is grounded through a current limiting resistor circuit; pin D is connected to the primary coil NP of the switching power supply transformer;

[0036] The current limiting resistor circuit connected to the pin S may include a resistor R6 and a resistor R6A connected in parallel;

[0037] In some embodiments, a rectifier circuit and a filter circuit are provided on a connection path of the power supply VCC pin connected to the secondary coil Na of the transformer of the switching power supply; a connection path of the power supply VCC pin connected to the secondary coil Na of the transformer of the switching power supply is connected to the feedback point of the primary coil of the transformer, that is, connected to the opposite-name end of the primary coil of the transformer through the resistor R1 and the resistor R2;

[0038] Optionally, the rectifier circuit includes a rectifier diode D3, and an RC circuit connected in parallel at both ends of the diode D3, wherein the RC circuit includes a resistor R14 and a capacitor C11 connected in series;

[0039] The role of RC is to protect the rectifier diode. RC can not only absorb the reverse peak voltage induced by the transformer, but also shunt the reverse current of the diode according to the reverse current at high frequency, thereby reducing the load on the diode.

[0040] Optionally, the filter circuit includes a resistor R3 and a capacitor circuit, one end of the capacitor circuit is connected to the resistor, and the other end is grounded; the capacitor circuit includes a capacitor C5 and a capacitor EC3 connected in parallel.

[0041] The output voltage control circuit of this embodiment, as a control circuit of a switching power supply, designs the elements in the second resistance circuit for calculating the output voltage to be connected in series, thereby avoiding the probability of the second resistance circuit tending to zero, thereby reducing the probability of the output voltage being too high.

[0042] Example 2

[0043] Based on Example 1, this embodiment provides a switching power supply, and the voltage control circuit of the switching power supply adopts an overvoltage protection circuit of a PSR power supply architecture described in Example 1.

[0044] A realizable switching power supply circuit structure, such as Figure 1 As shown, it also includes an input rectifier filter circuit, a transformer and an output filter rectifier circuit;

[0045] In some embodiments, the input rectifier and filter circuit is used to convert AC power into DC power that meets the requirements; it includes a lightning protection unit, an electromagnetic interference filter unit circuit, and a rectifier and filter unit circuit;

[0046] Specifically, Figure 3 As shown, the lightning protection unit includes capacitors CY3 and CY4 at the AC input end, fuses F1 and F2 and a thermistor connected in series in the line, and a lightning protection device MOV1;

[0047] Optionally, an electromagnetic interference filter unit circuit is arranged before the rectifier bridge stack BD1 to achieve circuit filtering; it includes a filter capacitor CX1, a bridge balancing circuit and an excitation coil LF1;

[0048] The bridge balancing circuit includes four resistors, which are connected in series in pairs and then in parallel, and are connected by wires; the four resistors are resistor RX1, resistor RX2, resistor RX3 and resistor RX4;

[0049] Optionally, the rectifier and filter unit circuit includes: a rectifier bridge stack BD1 and a primary filter circuit, the primary filter circuit includes a filter capacitor EC1; a resistor R7, a resistor R8 and a diode D2 connected in series to the primary coil of the transformer; the upper end of the resistor R7 is connected to the positive end of the capacitor EC1 and the opposite end of the primary coil of the transformer, and the two ends of the resistor R7 are connected in parallel with a series capacitor C6 and a capacitor C6A; the upper end of the resistor R7 is connected to the output voltage control circuit as the output of the primary feedback.

[0050] When in use, the input AC power passes through the fuse F1, the lightning protection device MOV1 in front of F2, and the rectifier bridge BD1, and then the AC power is converted into DC power. After being smoothed and filtered by EC1, it becomes a DC voltage that meets the requirements.

[0051] The rectified DC power is connected to the main winding Np of the transformer, and then connected to the D-level and S-level switch tubes in the main control chip, and then passes through the current limiting resistor circuit (including resistor R6 and resistor R6A) and then connected to the capacitor ground GND;

[0052] The current limiting resistor circuit R6 and R6A control the output current, and the output current can be controlled by adjusting the size of the two resistors;

[0053] Figure 1 The winding Na of the transformer, the resistor R4, the resistors R5A, R5B, R5C, R5D, R5E, and the reference Vref of the main control chip U1 form a circuit for controlling the output voltage. The output voltage can be set by adjusting the resistors R4, R5A, R5B, R5C, R5D, and R5E. The calculation formula is:

[0054] Vo=Vref*(1+Rup / Rdown)*Ns / Na

[0055] Wherein, Ns / Na is the turns ratio of the transformer winding; Vref is determined by the parameters of the main control chip U1; Rup is the upper bias resistor provided by the first resistor circuit; Rdown is the lower bias resistor provided by the second resistor circuit;

[0056] Rup is the upper bias resistor R4, Rdown is the lower bias resistor including the resistance of the second resistor circuit composed of R5A, R5B, R5C, R5D and R5E in the circuit diagram;

[0057] The output filter rectifier circuit is used to sort and filter the transformer output. The AC signal of the transformer Ns winding is converted into a DC voltage signal through the D1 rectifier tube, and then passes through the filter circuit composed of EC4, EC5, LF2, and EC6 to output a DC voltage that meets the smoothness requirements. C8 and R9 in the figure are used to suppress the interference signal generated by the D1 switching process.

[0058] The overvoltage protection function of the overvoltage protection circuit proposed in this embodiment in a switching power supply is described below with a specific example.

[0059] For example, for a 12V 1.25A PSR circuit, the required output overvoltage (OVP) is 16V maximum. If the traditional upper and lower resistors are used, Figure 6 As shown:

[0060] When R5 is simulating failure and tending to zero, the lower bias resistance Rdown drops to a certain value and the maximum output voltage is 28V, which is far more than the maximum 16V required by the customer. When the lower bias resistance Rdown tends to zero, the output voltage is close to ∞.

[0061] When the voltage reaches 28V, the VCC overvoltage protection of the main control chip will be triggered, so the output voltage will not reach infinity.

[0062] For example: Rup=R4=16K, Rdown=R5=2.78K;

[0063] Vo=2.5*(1+16K / 2.78K)*8 / 11=12.2V, which is normal output;

[0064] The modified circuit of this embodiment is adopted Figure 2 , use 5 resistors in series, then use 556Ω*5, when the minimum value of a single failure resistor is 0, the total value of the lower bias resistor is 556*4=2.224KΩ;

[0065] The maximum output voltage is:

[0066] Vo=2.5*(1+16K / 2.224K)*8 / 11=14.89V

[0067] That is to say, if any of R5A, R5B, R5C, R5D, and R5E fails, the maximum voltage of the circuit is 14.89V;

[0068] The above practical use shows that this circuit can effectively prevent the output voltage from being too high after failure in the single component failure mode test, thus achieving overvoltage protection.

[0069] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

[0070] Although the above describes the specific implementation methods of the utility model in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the utility model. Technical personnel in the relevant field should understand that on the basis of the technical solution of the utility model, various modifications or deformations that can be made by technical personnel in this field without creative work are still within the scope of protection of the utility model.

Claims

1. An overvoltage protection circuit of a PSR power supply architecture, characterized in that: A PSR circuit is used as an output voltage control circuit. The PSR circuit includes a first resistance circuit and a second resistance circuit. The resistance ratio of the first resistance circuit to the second resistance circuit is used to determine the output voltage of the switching power supply. The second resistance circuit adopts a structure in which a plurality of resistors are connected in series.

2. The overvoltage protection circuit of a PSR power supply architecture according to claim 1, characterized in that: The first resistance circuit is configured as a variable resistor, a series-parallel circuit of multiple resistors, or a circuit of a single resistor.

3. The overvoltage protection circuit of a PSR power supply architecture according to claim 1, characterized in that: The second resistance circuit includes a resistance branch composed of a plurality of resistors connected in series, and a capacitance branch composed of a plurality of capacitors connected in series; the resistance branch and the capacitance branch are connected in parallel.

4. The overvoltage protection circuit of a PSR power supply architecture as claimed in claim 3, characterized in that: The resistance value and number of the resistors in the resistor branch are set according to the output voltage.

5. The overvoltage protection circuit of a PSR power supply architecture according to claim 1, characterized in that: The PSR circuit further includes a switch circuit, and the first resistance circuit and the second resistance circuit are respectively connected to the switch circuit.

6. The overvoltage protection circuit of a PSR power supply architecture as claimed in claim 5, characterized in that: The switching circuit adopts the main control chip U1, which includes pin D, pin S, sampling voltage pin Vref, power supply VCC pin and ground pin GND; pin D is connected to the drain of the built-in switching tube, and pin S is connected to the source of the built-in switching tube; the sampling voltage pin Vref is used as a sampling point to connect the first resistance circuit and the second resistance circuit respectively; the power supply VCC pin is connected to the secondary coil Na of the transformer of the switching power supply; pin S is grounded through a current limiting resistor circuit; pin D is connected to the primary coil NP of the switching power supply transformer.

7. The overvoltage protection circuit of a PSR power supply architecture according to claim 6, characterized in that: The current limiting resistor circuit connected to the pin S includes a resistor R6 and a resistor R6A connected in parallel.

8. The overvoltage protection circuit of a PSR power supply architecture as claimed in claim 6, characterized in that: The power supply VCC pin is connected to the connection path of the secondary coil Na of the transformer of the switching power supply. A rectifier circuit and a filter circuit are provided, and the connection path is connected to the feedback point of the primary coil of the transformer.

9. A switching power supply, characterized in that: The voltage control circuit of the switching power supply adopts an overvoltage protection circuit of a PSR power supply architecture as described in any one of claims 1 to 8 as an output voltage control circuit.

10. A switching power supply according to claim 9, characterized in that: The switching power supply circuit also includes an input rectifying and filtering circuit, a transformer and an output filtering and rectifying circuit which are connected in sequence.

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