Novel output short-circuit protection circuit and switching power supply

Abstract

The utility model provides a novel output short-circuit protection circuit and a switching power supply. The circuit comprises a sampling current input end, a rectification filter circuit, a first voltage stabilizer, a voltage division circuit, a second voltage stabilizer and a control chip. The rectifying and filtering circuit is used for rectifying and filtering a detection signal input by the sampling current input end; the rectified and filtered detection signal enters the voltage division circuit for voltage division after being higher than a set threshold value of the first voltage stabilizer; after the voltage-divided detection signal is higher than a set threshold value of the second voltage stabilizer, the detection signal enters a Det function pin of the control chip, and whether the circuit is in an output short-circuit state or not is judged according to a set protection value of the Det function pin. By introducing the voltage stabilizer, the Det function pin and the like, the short-circuit protection circuit independent of the CS pin is realized, a more efficient and accurate short-circuit protection function is realized, and the working reliability of the whole circuit is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of power supply circuit especially a novel output short circuit protection circuit and switching power supply. BACKGROUND

[0002] At present, the traditional output short circuit protection in switching power supply is to set the threshold value of power IC detecting power switch tube current CS pin, when exceeding the threshold value set in IC and reaching certain time, considering output short circuit and entering short circuit protection mode. Figure 1 The line graph of output short circuit protection circuit in prior art is shown as Figure 1 When the current of current detection pin ISENSE passes through resistance R1, resistance R2 and resistance R3 voltage division, there is Ir1=Ir2+Ir3, Ur2=Ur3, wherein resistance R2 is high-power wire-wound non-inductive resistance with small resistance value, and resistance R3 is chip resistance with large resistance value, when current increases, Ir2 increases, UR2 also increases, and the voltage of UR3 also increases, when reaching the protection voltage of IC detection pin CS, the chip will enter short circuit protection mode.

[0003] The above circuit is simple in structure, but since the short circuit protection mode depends on the overcurrent protection function of IC CS pin, the short circuit protection of detection pin CS may also affect the overcurrent protection function. SUMMARY

[0004] Therefore, the utility model provides a novel output short circuit protection circuit and switching power supply.

[0005] In the first aspect, the utility model provides a novel output short circuit protection circuit, including: sampling current input terminal, rectifier filter circuit, first stabilizer, voltage division circuit, second stabilizer and control chip,

[0006] The rectifier filter circuit is used for rectifying and filtering the detection signal input by the sampling current input terminal,

[0007] After the rectification and filtering of the detection signal, when the detection signal is higher than the set threshold value of the first stabilizer, the detection signal enters the voltage division circuit for voltage division,

[0008] After the voltage division of the detection signal, when the detection signal is higher than the set threshold value of the second stabilizer, the detection signal enters the Det function pin of the control chip, and whether the circuit is in output short circuit state is judged according to the set protection value of the Det function pin.

[0009] As a preferred embodiment of the utility model, the rectifier filter circuit includes capacitor C1, diode D1 and diode D2.

[0010] One end of the capacitor C1 is connected to the sampling current input end, and the other end of the capacitor C1 is connected to the negative electrode of the diode D1 and the positive electrode of the diode D2.

[0011] As a preferred embodiment of the utility model, the rectifier filter circuit further includes resistance R1 and capacitor C2;

[0012] The negative electrode of the diode D2 is connected to one end of the resistance R1 and one end of the capacitor C2;

[0013] The positive electrode of the diode D1, the other end of the resistance R1 and the other end of the capacitor C2 are all grounded.

[0014] As a preferred embodiment of the utility model,

[0015] The first voltage stabilizer includes first voltage stabilizing diode ZD1;

[0016] The rectifier filter circuit further includes diode D3;

[0017] The positive electrode of the diode D3 is connected to the negative electrode of the diode D2;

[0018] The negative electrode of the diode D3 is connected to the negative electrode of the first voltage stabilizing diode ZD1.

[0019] As a preferred embodiment of the utility model,

[0020] The second voltage stabilizer includes second voltage stabilizing diode ZD2;

[0021] The voltage dividing circuit includes resistance R2 and resistance R3;

[0022] The positive electrode of the first voltage stabilizing diode ZD1 is connected to one end of the resistance R2;

[0023] The other end of the resistance R2 is connected to one end of the resistance R3 and the negative electrode of the second voltage stabilizing diode ZD2;

[0024] The other end of the resistance R3 is grounded.

[0025] As a preferred embodiment of the utility model, the voltage dividing circuit further includes capacitor C3;

[0026] One end of the capacitor C3 is connected to the negative electrode of the second voltage stabilizing diode ZD2;

[0027] The other end of the capacitor C3 is grounded.

[0028] As a preferred embodiment of the utility model, the anode of the second voltage stabilizing diode ZD2 is connected to the Det function pin.

[0029] As a preferred embodiment of the utility model, the control chip further comprises a CS pin, which is used for current detection and realizing overcurrent protection of the circuit.

[0030] As a preferred embodiment of the utility model, the set protection value of the Det function pin is greater than the set protection value of the CS pin.

[0031] In the second aspect, the utility model further provides a switching power supply, which comprises the novel output short-circuit protection circuit in any embodiment of the utility model.

[0032] Compared with the prior art, the utility model has the following beneficial effects:

[0033] The technical scheme of the utility model embodiment introduces a stabilizer and a Det function pin, realizes a short-circuit protection circuit independent of the CS pin, realizes short-circuit protection without affecting the function of the overcurrent protection point of the original CS pin control system circuit, well separates the overcurrent protection function and the short-circuit protection function of the circuit system without mutual interference, realizes more efficient and precise short-circuit protection function, and improves the reliability of overall circuit operation. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or the prior art, the drawings needed in the embodiment or the prior art description will be briefly introduced as follows, and obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative labor.

[0035] Figure 1 It is a circuit diagram of the short-circuit protection circuit in the prior art;

[0036] Figure 2 It is a circuit module schematic diagram of the novel output short-circuit protection circuit in the utility model embodiment;

[0037] Figure 3 It is a circuit diagram of the novel output short-circuit protection circuit in the utility model embodiment. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be described clearly and completely in combination with the drawings in the embodiments of the utility model below. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0039] Embodiments:

[0040] In the first aspect, as Figure 2 indicated, the utility model embodiments provide a novel output short circuit protection circuit, including: sampling current input end 10, rectifier filter circuit 20, first voltage stabilizer 30, voltage dividing circuit 40, second voltage stabilizer 50 and control chip 60.

[0041] The rectifier filter circuit 20 is used for rectifying and filtering the detection signal input by the sampling current input end 10.

[0042] After the rectification and filtering of the detection signal, when the detection signal is higher than the set threshold value of the first voltage stabilizer 30, the detection signal enters the voltage dividing circuit 40 for voltage division.

[0043] After the voltage division of the detection signal, when the detection signal is higher than the set threshold value of the second voltage stabilizer 50, the detection signal enters the Det function pin of the control chip 60, and whether the circuit is in the output short circuit state is judged according to the set protection value of the Det function pin.

[0044] The technical scheme of the utility model embodiments realizes a short circuit protection circuit not dependent on the CS pin by introducing two voltage stabilizing diodes and a Det function pin, realizes the short circuit protection while not affecting the function of the overcurrent protection point of the original CS pin control system circuit, well separates the overcurrent protection function and the short circuit protection function of the circuit system without mutual interference, realizes the higher efficient and precise short circuit protection function, and improves the reliability of the overall circuit work.

[0045] As a preferred embodiment of the utility model, referring to Figure 3 , the rectifier filter circuit includes a capacitor C1, a diode D1 and a diode D2.

[0046] One end of the capacitor C1 is connected to the sampling current input end, and the other end of the capacitor C1 is connected to the negative electrode of the diode D1 and the positive electrode of the diode D2 at the same time.

[0047] The rectification filter circuit is used for rectifying and filtering the detection signal input by the sampling current input end to eliminate the false recognition caused by the possible peak current.

[0048] As a preferred embodiment of the utility model, refer to Figure 3 , the rectification filter circuit further includes resistance R1 and capacitor C2;

[0049] The negative pole of the diode D2 is connected to one end of the resistance R1 and one end of the capacitor C2 simultaneously.

[0050] The positive pole of the diode D1, the other end of the resistance R1 and the other end of the capacitor C2 are all grounded.

[0051] Specifically, the capacitor C2 can be used to divide the voltage of the signal with the capacitor C1; the resistance R1 can further discharge the capacitor to ensure the accuracy of the sampling signal in each cycle.

[0052] As a preferred embodiment of the utility model, refer to Figure 3 , the first voltage stabilizer includes a first voltage stabilizing diode ZD1;

[0053] The rectification filter circuit further includes a diode D3;

[0054] The positive pole of the diode D3 is connected to the negative pole of the diode D2.

[0055] The negative pole of the diode D3 is connected to the negative pole of the first voltage stabilizing diode ZD1.

[0056] The diode D3 can prevent current backflow and protect the electronic components in the circuit.

[0057] As a preferred embodiment of the utility model, refer to Figure 3 , the second voltage stabilizer includes a second voltage stabilizing diode ZD2;

[0058] The voltage dividing circuit includes resistance R2 and resistance R3;

[0059] The positive pole of the first voltage stabilizing diode ZD1 is connected to one end of the resistance R2;

[0060] The other end of the resistance R2 is connected to one end of the resistance R3 and the negative pole of the second voltage stabilizing diode ZD2 simultaneously.

[0061] The other end of the resistance R3 is grounded.

[0062] The resistance values of the resistance R2 and the resistance R3 can be adjusted in coordination with the parameters of the first voltage stabilizing diode ZD1 and the set protection value of the Det function pin.

[0063] As a preferred embodiment of the utility model, refer to Figure 3 , the voltage dividing circuit still includes the capacitor C3;

[0064] One end of the capacitor C3 is connected to the negative pole of the second voltage stabilizing diode ZD2;

[0065] The other end of the capacitor C3 is grounded.

[0066] Specifically, the resistance R2 preferably adopts a small resistance value, can play the current limiting effect, protects the voltage stabilizing diode, and can also play certain filtering effect;Resistance R3 and capacitor C3 are equivalent to parallel with resistance R1, capacitor C2, can play the micro-adjustment effect to signal, improve the stability of circuit.

[0067] As a preferred embodiment of the utility model, the positive pole of the second voltage stabilizing diode ZD2 is connected to the Det function pin.

[0068] The second voltage stabilizing diode ZD2 is used for further voltage stabilization,

[0069] As a preferred embodiment of the utility model, refer to Figure 3 , the control chip still includes CS pin, and the CS pin is used for current detection, realizes the overcurrent protection of circuit.

[0070] As a preferred embodiment of the utility model, the set protection value of the Det function pin is greater than the set protection value of the CS pin.

[0071] The set protection value of the Det function pin is greater than the set protection value of the CS pin, can avoid the intersection existing on overcurrent protection function and short-circuit protection function parameter, thereby avoiding the influence of original overcurrent protection function.

[0072] The working principle of the novel output short-circuit protection circuit of the utility model embodiment is as follows:

[0073] Refer to Figure 3, the current sampling signal is rectified and filtered by capacitor C1, diode D1 and diode D2, if the value of the sampling signal is higher than the threshold value set by first voltage stabilizing diode ZD1, the sampled current signal will continue to pass through the voltage dividing resistor and reach second voltage stabilizing diode ZD2; if it is higher than the threshold value set by second voltage stabilizing diode ZD2, it can enter the Det function pin of the control chip, according to the set protection value of the Det function pin, it can be judged whether the circuit is in the output short circuit state: when the current reaching the Det function pin is greater than the set protection value, it can be considered that the circuit is in the output short circuit state, so that the short circuit protection operation is performed, such as stopping the output inside the circuit.

[0074] The specific protection value size can be adjusted by the parameters of first voltage stabilizing diode ZD1, resistor R2, resistor R3 and second voltage stabilizing diode ZD2, and the related element parameters can also be set and adjusted by the user.

[0075] In the second aspect, the utility model also provides a switching power supply, the switching power supply includes the novel output short circuit protection circuit in any embodiment of the utility model.

[0076] The above is only the preferred embodiment of the utility model patent, but the protection scope of the utility model patent is not limited to this, any skilled person in the art can make equivalent replacement or change according to the technical scheme and the utility model concept of the utility model patent within the range disclosed by the utility model patent, which belongs to the protection scope of the utility model patent.

Claims

1. A novel output short-circuit protection circuit, characterized in that, include: The circuit includes a sampling current input terminal, a rectifier and filter circuit, a first voltage regulator, a voltage divider circuit, a second voltage regulator, and a control chip. The rectifier and filter circuit is used to rectify and filter the detection signal input to the sampling current input terminal; after the rectified and filtered detection signal is higher than the set threshold of the first voltage regulator, it enters the voltage divider circuit for voltage division; after the voltage divider detection signal is higher than the set threshold of the second voltage regulator, it enters the Det function pin of the control chip, and determines whether the circuit is in an output short circuit state according to the set protection value of the Det function pin.

2. The output short-circuit protection circuit according to claim 1, characterized in that, The rectifier and filter circuit includes a capacitor C1, a diode D1, and a diode D2; one end of the capacitor C1 is connected to the sampling current input terminal, and the other end of the capacitor C1 is connected to both the negative terminal of the diode D1 and the positive terminal of the diode D2.

3. The output short-circuit protection circuit according to claim 2, characterized in that, The rectifier and filter circuit also includes a resistor R1 and a capacitor C2; the negative terminal of the diode D2 is connected to one end of the resistor R1 and one end of the capacitor C2; the positive terminal of the diode D1, the other end of the resistor R1, and the other end of the capacitor C2 are all grounded.

4. The output short-circuit protection circuit according to claim 3, characterized in that, The first voltage regulator includes a first Zener diode ZD1; the rectifier filter circuit further includes a diode D3; the anode of the diode D3 is connected to the cathode of the diode D2; the cathode of the diode D3 is connected to the cathode of the first Zener diode ZD1.

5. The output short-circuit protection circuit according to claim 4, characterized in that, The second voltage regulator includes a second Zener diode ZD2; the voltage divider circuit includes a resistor R2 and a resistor R3; the positive terminal of the first Zener diode ZD1 is connected to one end of the resistor R2; the other end of the resistor R2 is connected to both one end of the resistor R3 and the negative terminal of the second Zener diode ZD2; the other end of the resistor R3 is grounded.

6. The output short-circuit protection circuit according to claim 5, characterized in that, The voltage divider circuit also includes a capacitor C3; one end of the capacitor C3 is connected to the negative terminal of the second Zener diode ZD2; the other end of the capacitor C3 is grounded.

7. The output short-circuit protection circuit according to claim 6, characterized in that, The positive terminal of the second Zener diode ZD2 is connected to the Det function pin.

8. The output short-circuit protection circuit according to claim 1, characterized in that, The control chip also includes a CS pin, which is used for current detection to achieve overcurrent protection of the circuit.

9. The output short-circuit protection circuit according to claim 8, characterized in that, The protection value set for the Det function pin is greater than the protection value set for the CS pin.

10. A switching power supply, characterized in that, The novel output short-circuit protection circuit includes any one of claims 1-9.

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