CN210518115U - Protection circuit of sampling resistor, flyback converter and switching power supply - Google Patents
Protection circuit of sampling resistor, flyback converter and switching power supply Download PDFInfo
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- CN210518115U CN210518115U CN201921699191.XU CN201921699191U CN210518115U CN 210518115 U CN210518115 U CN 210518115U CN 201921699191 U CN201921699191 U CN 201921699191U CN 210518115 U CN210518115 U CN 210518115U
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 5
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- 239000010703 silicon Substances 0.000 claims description 5
- 230000001629 suppression Effects 0.000 claims description 4
- 230000001052 transient effect Effects 0.000 claims description 4
- 230000001419 dependent effect Effects 0.000 claims 1
- 238000010586 diagram Methods 0.000 description 4
- 238000004804 winding Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
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Abstract
The utility model discloses a sampling resistor's protection circuit, flyback converter and switching power supply, protection circuit includes the clamp component, the clamp component with sampling resistor parallel connection, the clamp component is in the voltage difference at sampling resistor both ends does not reach the turn-on pressure drop of clamp component is cut off, the clamp component is in the voltage difference reaches turn-on pressure drop switches on, with will the voltage difference at sampling resistor both ends presss from both sides extremely the turn-on pressure drop of clamp component. The utility model discloses can avoid the condition that sampling resistor burns out when bearing the high pressure, improve the security that has sampling resistor's circuit.
Description
Technical Field
The utility model belongs to the technical field of the circuit, especially, relate to a sampling resistor's protection circuit, flyback converter and switching power supply.
Background
At present, some circuits can adopt a sampling resistor to sample some sampling points in the circuit, for example, current sampling is carried out on current sampling points, when the voltage of the current sampling points is increased, high voltage is directly applied to two ends of the sampling resistor, so that the sampling resistor is burnt, and arc discharge is likely to occur seriously to generate spark to spray outwards, so that the circuit is burnt.
For example, a current-controlled switching power supply generally employs a sampling resistor to perform power sampling on a bus voltage, and since a power input at one end of a transformer of the current-controlled switching power supply is a dc bus voltage obtained from a three-phase ac output, and the dc bus voltage is boosted to about 700 + 800V, when a switching element of the switching power supply fails and is shorted, the dc voltage of the bus is directly applied to two ends of the sampling resistor, which may cause the sampling resistor to be burned.
SUMMERY OF THE UTILITY MODEL
An embodiment of the utility model provides a sampling resistor's protection circuit, flyback converter and switching power supply to sampling resistor burns out easily and leads to taking place dangerous problem among the solution prior art.
A first aspect of an embodiment of the present invention provides a protection circuit for a sampling resistor, where the protection circuit includes a clamping element, and the clamping element is connected in parallel with the sampling resistor;
the clamping element is cut off when the voltage difference between the two ends of the sampling resistor does not reach the conduction voltage drop of the clamping element;
and the clamping element is conducted when the voltage difference reaches the conduction voltage drop, so that the voltage difference at two ends of the sampling resistor is clamped to the conduction voltage drop of the clamping element.
Optionally, the clamping element includes a diode, an anode of the diode and a positive end of the sampling resistor are both connected to the current sampling point, and a cathode of the diode and a negative end of the sampling resistor are both connected to the voltage reference point.
Optionally, the diode comprises a normal diode or a unidirectional transient suppression diode.
Optionally, when the clamping element includes more than two diodes, the more than two diodes are connected in series in the same direction, the conduction voltage drop of the clamping element is the sum of the conduction voltage drops of the diodes, and the sum of the conduction voltage drops of the diodes is not greater than the product of the resistance value of the sampling resistor and the maximum allowable current of the sampling resistor.
Optionally, the diodes are silicon tubes, and the conduction voltage drop of the clamping element is 0.7 times the number of the diodes.
Optionally, the sampling resistor includes an up-sampling resistor and a down-sampling resistor connected in series, a positive end of the up-sampling resistor is connected to the current sampling point, and a negative end of the down-sampling resistor is connected to the voltage reference point;
the clamping element comprises a three-terminal voltage-stabilizing tube, the input end of the three-terminal voltage-stabilizing tube is connected to the current sampling point, the output end of the three-terminal voltage-stabilizing tube is connected to the voltage reference point, and the middle end of the three-terminal voltage-stabilizing tube is connected to a connection point between the negative end of the upper sampling resistor and the positive end of the lower sampling resistor.
Optionally, the sampling resistor is a chip resistor.
A second aspect of the embodiments of the present invention provides a flyback converter, which includes an input power supply, a transformer, a switch element, and a sampling resistor, wherein a positive terminal of the sampling resistor is connected to a drain of the switch element, an output of the drain is used as a current sampling point, a negative terminal of the sampling resistor is grounded, and a ground terminal voltage is used as a voltage reference point;
the flyback converter further comprises a protection circuit of the sampling resistor.
Optionally, the flyback converter further includes a fuse connected between the input power supply and the transformer, and configured to be disconnected when a current flowing through the fuse is greater than a preset current threshold, where the current threshold is determined by a peak current of the current sampling point when the clamping element is turned on.
A third aspect of the embodiments of the present invention provides a switching power supply, which includes a flyback converter as in any one of the above.
Compared with the prior art, the embodiment of the utility model beneficial effect who exists is:
the utility model discloses a for the parallelly connected clamper element of sampling resistor in the circuit, this clamper element does not reach at the voltage difference at sampling resistor both ends cut off when pressing from both sides the turn-on voltage drop of clamper element for input voltage can normally pass through sampling resistor place loop, and this clamper element reaches at the voltage difference at sampling resistor both ends turn on when pressing from both sides the turn-on voltage drop of clamper element to with the voltage difference clamper at sampling resistor both ends to the turn-on voltage drop of clamper element, the turn-on voltage drop of clamper element designs for safe value usually, because the voltage difference at sampling resistor both ends is by clamper to this safe value when the clamper element switches on, thereby can avoid the sampling resistor to take place the condition of burning out when input voltage is higher than above-mentioned default, improve the security that has the circuit of sampling resistor.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments or the prior art descriptions will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive labor.
Fig. 1 is a schematic diagram of a protection circuit of a sampling resistor according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a protection circuit of a sampling resistor according to another embodiment of the present invention;
fig. 3 is a schematic diagram of a protection circuit of a sampling resistor according to another embodiment of the present invention.
Detailed Description
In order to make the technical solution better understood by those skilled in the art, the technical solution in the embodiment of the present invention will be clearly described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is a part of the embodiment of the present invention, and not a whole embodiment. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present disclosure without any creative effort shall fall within the protection scope of the present disclosure.
The terms "include" and any other variations in the description and claims of this document and the above-described figures, mean "include but not limited to", and are intended to cover non-exclusive inclusions and not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc. are used to distinguish between different objects and are not used to describe a particular order.
The following detailed description of the implementations of the present invention is made with reference to the accompanying drawings:
fig. 1 shows a schematic diagram of a protection circuit of a sampling resistor provided in an embodiment of the present invention, and for convenience of description, only the portions related to the embodiment of the present invention are shown, and detailed descriptions are as follows:
as shown in fig. 1, the protection circuit (the portion in the dashed line frame in fig. 1) of the sampling resistor according to the embodiment of the present invention includes a clamping element D, and the clamping element D is connected in parallel to the sampling resistor R.
The clamping element D is cut off when the voltage difference at the two ends of the sampling resistor R does not reach the conduction voltage drop of the clamping element, the conduction voltage drop can be selected based on the safe voltage of the sampling resistor D, the conduction voltage drop is related to the voltage drop of a specific element included in the clamping element D when the specific element is conducted, and the clamping element D is conducted when the voltage difference at the two ends of the sampling resistor R reaches the conduction voltage drop of the clamping element D, so that the voltage difference at the two ends of the sampling resistor R is clamped to the conduction voltage drop of the clamping element D.
For example, the clamping element D may be turned off when the voltage applied thereto is less than 0.7 v, so that the voltage applied thereto is normally applied to the sampling resistor R, and the circuit is in a normal current sampling state, where the input terminal of the sampling resistor R is connected to the current sampling point, and the output terminal of the sampling resistor R may be connected to a voltage reference point, which may be ground.
For example, the clamping element D may be turned on when the voltage applied thereto is not less than 0.7 v, and may be constantly maintained at a voltage drop of 0.7 v after being turned on, so that, since the sampling resistor R and the clamping element D are connected in parallel, the voltage drop across the clamping element D, which is constantly maintained at 0.7 v, is the voltage across the sampling resistor R, that is, even if the voltage at the input end of the sampling resistor R is increased, the voltage borne by the sampling resistor R may not exceed the voltage drop across the clamping element D by 0.7 v due to the turning on of the clamping element D. Thereby ensuring the safety of the sampling resistor R.
It is from top to bottom visible, the utility model discloses a for sampling resistor parallel connection clamp element in the circuit, this clamp element does not reach at the voltage difference at sampling resistor both ends the clamp element switch on when dropping, make input voltage can normally pass through sampling resistor place loop, this clamp element reaches at the voltage difference at sampling resistor both ends switch on when dropping of clamp element to with the voltage difference clamp at sampling resistor both ends to the voltage drop that switches on of clamp element, clamp element's the voltage drop that switches on designs for safe value usually, because the voltage difference at sampling resistor both ends is by the clamp to this safe value when clamp element switches on, thereby can avoid the sampling resistor to take place the condition of burning out when input voltage is higher than above-mentioned default, improve the security of the circuit that has sampling resistor.
In an alternative embodiment, the clamping element may be a diode having an anode connected to the current sampling point and a cathode connected to a voltage reference point (e.g., ground). The conduction voltage drop of the diode is the conduction voltage drop of the clamping element.
In an alternative embodiment, the clamping element may be a unidirectional Transient suppression (TVS) diode, an anode of the TVS diode and a positive terminal (input terminal) of the sampling resistor are both connected to the current sampling point, and a cathode of the TVS diode and a negative terminal (output terminal) of the sampling resistor are both connected to the voltage reference point (ground). In this embodiment, the ground point is used as a voltage reference point, the TVS diode is turned off when the voltage applied to the anode thereof is smaller than the voltage drop thereof, and is turned on when the voltage applied to the anode thereof is not smaller than the voltage drop thereof, and the two ends thereof maintain a constant voltage drop after being turned on.
In an alternative embodiment, the clamping element may be two or more diodes (D1, D2), as shown in fig. 2, the two or more diodes (D1, D2) are connected in series in the same direction, the anode of the upper diode is connected to the current sampling point, the anode of the lower diode is connected to the cathode of the upper diode, and the cathode of the lower diode is grounded, and the diodes may be normal diodes or unidirectional transient suppression diodes.
When the clamping element comprises more than two diodes, the more than two diodes are connected in series in the same direction, at the moment, the conduction voltage drop of the clamping element is the sum of the conduction voltage drops of the diodes, the sum of the conduction voltage drops of the diodes is not more than the product of the resistance value of the sampling resistor and the maximum allowable current of the sampling resistor, for example, when the product of the resistance value of the sampling resistor and the maximum allowable current of the sampling resistor is 1.4, the clamping element at most comprises two silicon diodes.
Optionally, the diodes may be all silicon tubes, and if the conduction voltage drop of the silicon tubes is 0.7 v, the conduction voltage drop of the clamping element may be 0.7 times the number of the diodes. For example, when the number of the diodes is two, the conduction voltage drop of the clamping element is 1.4 v, that is, the voltage across the sampling resistor is clamped to 1.4 v when the input voltage rises.
In an alternative embodiment, as shown in fig. 3, the sampling resistor D may include an up-sampling resistor R1 and a down-sampling resistor R2 connected in series, the positive terminal of the up-sampling resistor R1 being connected to the current sampling point (the drain output of the switching element S), and the negative terminal of the down-sampling resistor R2 being connected to the voltage reference point (ground).
The clamping element D can be a three-terminal voltage-stabilizing tube, the input end of the three-terminal voltage-stabilizing tube is connected to the current sampling point, the output end of the three-terminal voltage-stabilizing tube is connected to the voltage reference point, and the middle end of the three-terminal voltage-stabilizing tube is connected to the connection point between the negative end of the upper sampling resistor R1 and the positive end of the lower sampling resistor R2.
In an optional embodiment, the sampling resistor is a chip resistor, and the chip resistor has a relatively large linear inductance, and the sampling resistor is used for overcurrent detection, so that a current peak value is weakened due to the linear inductance, the judgment of the current peak value is insensitive, and the peak value protection function is lost.
An embodiment of the present invention further provides a flyback converter (e.g., fig. 1, fig. 2, and fig. 3), which may include an input power source, a transformer T, a switching element S, and a sampling resistor R.
The input power supply is connected to the input end of the primary winding of the transformer T, the source electrode of the switching element S is connected to the output end of the primary winding of the transformer T, the positive end of the sampling resistor R is connected to the drain electrode of the switching element S, the output of the drain electrode of the switching element S can be used as a current sampling point, the input end of the sampling resistor R is connected to the drain electrode of the switching element S, the output end of the sampling resistor R is grounded, and the voltage of the grounding point is used as a voltage reference point.
The flyback converter can further comprise a protection circuit of the sampling resistor, so that the safety of the sampling resistor and the flyback converter is guaranteed.
Optionally, the flyback converter may further include a fuse F, which may be a fuse and is connected between the input power source and the input end of the primary winding of the transformer, and the fuse F is configured to be turned off when a current flowing through the fuse is greater than a preset current threshold, where the current threshold is determined by a peak current (Ipeak) of a current sampling point when the clamping element D is turned on. Specifically, when the clamping element D is turned off, the input voltage does not go through the branch where the clamping element D is located, when the clamping element D is turned on, the branch where the clamping element D is located is gone, and when the branch where the clamping element D is located is gone, the circuit can alarm to indicate that the peak current at the current sampling point exceeds the standard, and a fault that the switching element S is short-circuited may exist. Therefore, on one hand, when the clamping element D is switched on, the clamping element D clamps the voltages at two ends of the sampling resistor, so that the sampling resistor is protected; on the other hand, the fuse with the corresponding current threshold value can be selected according to the peak current of the current sampling point, and the purpose is that when the peak current of the current sampling point exceeds the standard, the current passing through the fuse also exceeds the current threshold value of the fuse, so that the fuse is disconnected, and the safety of the whole circuit is guaranteed.
The embodiment of the utility model provides a still provide a switching power supply, this switching power supply can include as above-mentioned arbitrary flyback converter to when the input end voltage of sampling resistance that can be in switching power supply risees, guarantee sampling resistance's safety, and guarantee whole switching power supply circuit's safety.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.
Claims (10)
1. The protection circuit of the sampling resistor is characterized by comprising a clamping element, wherein the clamping element is connected with the sampling resistor in parallel;
the clamping element is cut off when the voltage difference between the two ends of the sampling resistor does not reach the conduction voltage drop of the clamping element;
and the clamping element is conducted when the voltage difference reaches the conduction voltage drop, so that the voltage difference at two ends of the sampling resistor is clamped to the conduction voltage drop of the clamping element.
2. The protection circuit of claim 1, wherein the clamping element comprises a diode, an anode of the diode and a positive terminal of the sampling resistor are both connected to a current sampling point, and a cathode of the diode and a negative terminal of the sampling resistor are both connected to a voltage reference point.
3. The sampled resistor protection circuit of claim 2, wherein the diode comprises a normal diode or a unidirectional transient suppression diode.
4. The protection circuit of claim 3, wherein when the clamping element comprises more than two diodes, the more than two diodes are connected in series in the same direction, the conduction voltage drop of the clamping element is the sum of the conduction voltage drops of the diodes, and the sum of the conduction voltage drops of the diodes is not more than the product of the resistance value of the sampling resistor and the maximum allowable current of the sampling resistor.
5. The sampled resistor protection circuit of claim 4, wherein the diodes are silicon transistors, and the conducting voltage drop of the clamping element is 0.7 times the number of the diodes.
6. The protection circuit of the sampling resistor as claimed in claim 1, wherein the sampling resistor comprises an up-sampling resistor and a down-sampling resistor connected in series, the positive terminal of the up-sampling resistor is connected to the current sampling point, and the negative terminal of the down-sampling resistor is connected to the voltage reference point;
the clamping element comprises a three-terminal voltage-stabilizing tube, the input end of the three-terminal voltage-stabilizing tube is connected to the current sampling point, the output end of the three-terminal voltage-stabilizing tube is connected to the voltage reference point, and the middle end of the three-terminal voltage-stabilizing tube is connected to a connection point between the negative end of the upper sampling resistor and the positive end of the lower sampling resistor.
7. The protection circuit of any one of claims 1 to 6, wherein the sampling resistor is a chip resistor.
8. The flyback converter is characterized by comprising an input power supply, a transformer, a switching element and a sampling resistor, wherein the positive end of the sampling resistor is connected to the drain electrode of the switching element, the output of the drain electrode is used as a current sampling point, the negative end of the sampling resistor is grounded, and the voltage of the ground end is used as a voltage reference point;
the flyback converter further comprises a protection circuit of the sampling resistor as claimed in any one of claims 1 to 7.
9. The flyback converter of claim 8 further comprising a fuse connected between the input power source and the transformer, the fuse configured to open when a current flowing through the fuse is greater than a preset current threshold, the current threshold dependent on a peak current of the current sampling point when the clamping element is on.
10. A switching power supply, characterized in that it comprises a flyback converter as claimed in claim 8 or 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921699191.XU CN210518115U (en) | 2019-10-11 | 2019-10-11 | Protection circuit of sampling resistor, flyback converter and switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921699191.XU CN210518115U (en) | 2019-10-11 | 2019-10-11 | Protection circuit of sampling resistor, flyback converter and switching power supply |
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| Publication Number | Publication Date |
|---|---|
| CN210518115U true CN210518115U (en) | 2020-05-12 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201921699191.XU Active CN210518115U (en) | 2019-10-11 | 2019-10-11 | Protection circuit of sampling resistor, flyback converter and switching power supply |
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| Country | Link |
|---|---|
| CN (1) | CN210518115U (en) |
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- 2019-10-11 CN CN201921699191.XU patent/CN210518115U/en active Active
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