CN219145247U - Dummy load switching circuit and switching power supply - Google Patents
Dummy load switching circuit and switching power supply Download PDFInfo
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- CN219145247U CN219145247U CN202223100790.XU CN202223100790U CN219145247U CN 219145247 U CN219145247 U CN 219145247U CN 202223100790 U CN202223100790 U CN 202223100790U CN 219145247 U CN219145247 U CN 219145247U
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Abstract
The utility model provides a dummy load switching circuit which is applied to a positive-negative double-circuit output switching power supply, wherein the positive-negative double-circuit output switching power supply comprises a first dummy load branch and a second dummy load branch, a first input end of the first dummy load branch is connected with one end of the second dummy load branch and is used for being connected with a positive output end of the switching power supply, a second input end of the first dummy load branch is connected with a voltage division point of the second dummy load branch, an output end of the first dummy load branch is grounded, and the other end of the second dummy load branch is used for being connected with a negative output end of the switching power supply; when the negative output end of the switching power supply is short-circuited, the first dummy load branch is switched to be used as a dummy load of the positive and negative double-circuit output switching power supply so as to pull down the output voltage of the positive output end of the switching power supply; when the switching power supply works normally, the second dummy load branch is switched to be used as a dummy load of the positive and negative double-circuit output switching power supply, so that the dummy load impedance is improved.
Description
Technical Field
The present utility model relates to switching power supplies, and more particularly, to a dummy load switching circuit and a switching power supply.
Background
In a high-reliability switching power supply, an output short-circuit protection function is a basic and necessary function, and can effectively protect the switching power supply itself and equipment at the rear end thereof from damage when the output end is abnormally short-circuited. At present, in a positive-negative double-circuit output switching power supply, a working mode of one closed-circuit output and one open-circuit output is generally adopted, one positive-voltage output is generally a closed-circuit output, one negative-voltage output is generally an open-circuit output, and the closed-circuit output and the open-circuit output are commonly grounded. And when the output voltage of the closed loop output circuit is detected to be continuously lower than the set voltage value, the switching power supply enters a short-circuit protection state.
Ideally, the transformer winding of the closed loop output path and the transformer winding of the open loop output path are completely coupled, wherein when one path is short-circuited, the output voltage of the other path is close to 0V, so when the open loop output path is short-circuited, the voltage of the closed loop output path is close to 0V, and the switching power supply enters a short-circuit protection state after detecting that the voltage of the closed loop output path is continuously lower than a set value. However, in the practical application process, the two transformer windings cannot be completely coupled under the influence of factors such as materials, processes and the like, and certain transformer leakage inductance energy exists. Therefore, in practical application, when the open-loop output circuit is short-circuited, the leakage inductance energy of the transformer still provides energy for the closed-loop output circuit, wherein one part of the leakage inductance energy of the transformer is consumed by the load of the closed-loop output circuit, and the other part of the leakage inductance energy is stored in the filter capacitor of the closed-loop output circuit; if the closed loop output circuit is in light load or no load, most of leakage inductance energy of the transformer is stored in the filter capacitor, so that the voltage at the output end of the closed loop output circuit is continuously increased until the voltage is stabilized at a set voltage value, and under the wrong feedback information, the switching power supply cannot enter a short circuit protection state, so that the switching power supply is damaged due to over-power.
To solve this problem, the prior art solution is to connect a resistive dummy load in parallel at the filter capacitor of the closed loop output circuit, as shown in fig. 1; when no load or light load is output, leakage inductance energy of the transformer is rapidly consumed through the dummy load, so that the closed loop output circuit maintains low voltage, and the short circuit protection state is achieved. However, there are problems in that: in order to quickly consume the leakage inductance energy of the transformer, the current flowing through the resistor dummy load needs to reach several mA or even tens mA, so that when the switching power supply works normally, the static power consumption of the switching power supply with the power lower than 30W is often increased by 1-2 times due to the existence of the dummy load. When the power of the switching power supply is larger, the leakage inductance energy of the transformer is larger, and the current flowing through the dummy load is also required to be larger, so that the static power consumption is also larger; therefore, although the scheme of the prior art ensures high reliability of the switching power supply, due to the existence of the dummy load connected in parallel with the closed loop output circuit, the static power consumption of the switching power supply is greatly increased, the loss of the dummy load is converted into the internal heat of the power supply, and the heat dissipation requirement is required to be additionally increased.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present utility model is to provide a dummy load switching circuit, so as to enable the switching power supply to enter a short-circuit protection state when the open-loop output circuit of the positive and negative two-way output switching power supply is short-circuited, and improve the reliability of the switching power supply; meanwhile, when the positive and negative double-circuit output switching power supply works normally, the switching power supply is reduced, and the switching power supply conversion efficiency is improved.
As a first aspect, the present utility model provides a dummy load switching circuit according to the following technical scheme:
the dummy load switching circuit is applied to a positive-negative double-circuit output switching power supply and comprises a first dummy load branch and a second dummy load branch, wherein a first input end of the first dummy load branch is connected with one end of the second dummy load branch and is used for being connected with a positive output end of the switching power supply, a second input end of the first dummy load branch is connected with a voltage division point of the second dummy load branch, an output end of the first dummy load branch is grounded, and the other end of the second dummy load branch is used for being connected with a negative output end of the switching power supply; when the negative output end of the switching power supply is short-circuited, the first dummy load branch is switched to serve as a dummy load of the positive and negative double-circuit output switching power supply so as to pull down the output voltage of the positive output end of the switching power supply; and when the switching power supply works normally, switching to the second dummy load branch as the dummy load of the positive and negative double-way output switching power supply so as to improve the dummy load impedance.
Further, the first dummy load branch comprises a first switching tube, one end of the first switching tube is a first input end of the first dummy load branch, the control end is a second input end of the first dummy load branch, and the other end of the first switching tube is an output end of the first dummy load branch.
Further, the first dummy load branch includes a first switching tube and a voltage dividing resistor R3, one end of the resistor R3 is a first input end of the first dummy load branch, the other end of the resistor R3 is connected with one end of the first switching tube, a control end of the first switching tube is a second input end of the first dummy load branch, and the other end of the first switching tube is an output end of the first dummy load branch.
Further, the first switching tube is an NPN type triode Q1, the collector electrode of the triode Q1 is one end of the first switching tube, the base electrode is the control end of the first switching tube, and the emitter electrode is the other end of the first switching tube.
Further, the second dummy load branch comprises a first voltage dividing device and a second voltage dividing device, one end of the first voltage dividing device is one end of the second dummy load branch, the other end of the first voltage dividing device is connected with one end of the second voltage dividing device to serve as a voltage dividing point of the second dummy load branch, and the other end of the second voltage dividing device is the other end of the second dummy load branch.
Further, the first voltage dividing device and/or the second voltage dividing device is a resistor.
The utility model provides a dummy load switching circuit, is applied to positive and negative double-circuit output switching power supply, switching power supply includes first output winding, second output winding, first rectifying tube, second rectifying tube, first filter capacitor C1, second filter capacitor C2, positive output and negative output, its characterized in that: the dummy load switching circuit comprises a first voltage dividing resistor R1, a second voltage dividing resistor R2 and a switching tube Q1; the same-name end of the first output winding is connected with one end of the first rectifying tube, the other end of the first rectifying tube is connected with one end of the capacitor C1, one end of the resistor R1 and one end of the switching tube Q1 and is used for being connected with a positive output end of a switching power supply, the other end of the resistor R1 is connected with one end of the resistor R2 and a control end of the switching tube Q1, the different-name end of the first output winding is connected with the same-name end of the second output winding, the other end of the capacitor C1, one end of the capacitor C2 and the other end of the switching tube Q1 are used for being grounded, the different-name end of the second output winding is connected with one end of the second rectifying tube, and the other end of the second rectifying tube is connected with the other end of the capacitor C2 and the other end of the resistor R2 and is used for being connected with a negative output end of the switching power supply.
The utility model provides a dummy load switching circuit, is applied to positive and negative double-circuit output switching power supply, switching power supply includes first output winding, second output winding, first rectifying tube, second rectifying tube, first filter capacitor C1, second filter capacitor C2, positive output and negative output, its characterized in that: the dummy load switching circuit comprises a first voltage dividing resistor R1, a second voltage dividing resistor R2, a third voltage dividing resistor R3 and a switching tube Q1; the same-name end of the first output winding is connected with one end of the first rectifying tube, the other end of the first rectifying tube is connected with one end of the capacitor C1, one end of the resistor R1 and one end of the resistor R3 and is used for being connected with a positive output end of a switching power supply, the other end of the resistor R3 is connected with one end of the switching tube Q1, the other end of the resistor R1 is connected with one end of the resistor R2 and a control end of the switching tube Q1, the different-name end of the first output winding is connected with the same-name end of the second output winding, the other end of the capacitor C1, one end of the capacitor C2 and the other end of the switching tube Q1 are grounded, the different-name end of the second output winding is connected with one end of the second rectifying tube, and the other end of the resistor R2 are connected with the other end of the second rectifying tube and are used for being connected with a negative output end of the switching power supply.
Further, the first rectifying tube is a diode D1, an anode of the diode D1 is one end of the first rectifying tube, and an cathode of the diode D1 is the other end of the first rectifying tube; the second rectifying tube is a diode D2, the cathode of the diode D2 is one end of the second rectifying tube, and the anode of the diode D2 is the other end of the second rectifying tube; the switching tube Q1 is an NPN triode, the collector electrode of the triode is one end of the switching tube, the base electrode of the triode is the control end of the switching tube, and the emitter electrode of the triode is the other end of the switching tube.
As a second aspect, the present utility model provides a dummy load switching circuit according to the following technical scheme:
a switching power supply comprising the dummy load switching circuit of any one of the first aspects above.
The working principle of the utility model is analyzed in detail by combining with specific embodiments, and details are not repeated here.
1. When the open-loop output path of the positive and negative double-path output switching power supply is short-circuited, the first dummy load branch is switched to serve as a dummy load of the positive and negative double-path output switching power supply, so that the output voltage of the positive output end of the switching power supply is pulled down to be continuously lower than the set value of the output voltage, the switching power supply is further enabled to enter a short-circuit protection state, and the reliability of the switching power supply is improved.
2. When the positive and negative double-circuit output switching power supply works normally, the second dummy load branch is used as the dummy load of the positive and negative double-circuit output switching power supply, so that the dummy load impedance is improved, the static power consumption of the switching power supply is further reduced, the switching power supply conversion efficiency is improved, and meanwhile, the problem of local heating caused by loss of the switching power supply can be further reduced;
3. the dummy load switching circuit does not need to be controlled by an IC, and has the advantages of simple circuit, few devices, low cost and easy realization.
Drawings
FIG. 1 is a schematic circuit diagram of a prior art dummy load applied to a switching power supply;
FIG. 2 is a schematic circuit diagram of a dummy load switching circuit applied to a switching power supply according to a first embodiment of the present utility model;
fig. 3 is a schematic circuit diagram of a dummy load switching circuit applied to a switching power supply according to a second embodiment of the present utility model.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present utility model can be understood in detail, a more particular description of the utility model, briefly summarized below, may be had by reference to embodiments, some of which are illustrated in the appended drawings. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.
It should be noted that the terms "comprising" and "having," and any variations thereof, as described in the specification and claims of this application are intended to cover a non-exclusive inclusion, for example, comprising a series of elements or unit circuits that are not necessarily limited to those elements or unit circuits explicitly listed, but may include elements or unit circuits that are not explicitly listed or inherent to such circuits.
In addition, embodiments and features of embodiments in this application may be combined with each other without conflict.
It will be understood that, in the description and in the claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element or "connected" to the other element through a third element.
First embodiment
FIG. 2 is a schematic circuit diagram of a dummy load switching circuit applied to a switching power supply according to a first embodiment of the present utility model; the switching power supply comprises a first output winding, a second output winding, a first diode D1, a second diode D2, a first filter capacitor C1, a second filter capacitor C2, a positive output end +VO and a negative output end-VO; the dummy load switching circuit comprises a first voltage dividing resistor R1, a second voltage dividing resistor R2 and an NPN triode Q1; the same-name end of the first output winding is connected with the anode of the diode D1, the cathode of the diode D1 is connected with one end of the capacitor C1, one end of the resistor R1 and the collector of the triode Q1 and is used for being connected with the positive output end of the switching power supply, the other end of the resistor R1 is connected with one end of the resistor R2 and the base of the triode Q1, the different-name end of the first output winding is connected with the same-name end of the second output winding, the other end of the capacitor C1, one end of the capacitor C2 and the other end of the triode Q1 and is used for being grounded GND, the different-name end of the second output winding is connected with the cathode of the diode D2, and the anode of the diode D2 is connected with the other end of the capacitor C2 and the other end of the resistor R2 and is used for being connected with the negative output end of the switching power supply.
The working principle of this embodiment is as follows:
when the open-loop output circuit of the positive-negative double-circuit output switching power supply is short-circuited, namely the negative output end and the output ground end of the switching power supply are short-circuited, the connection point of the resistor R1 and the base electrode of the triode Q1 is positive pressure relative to the output ground end and reaches the threshold voltage of the triode Q1, the triode Q1 is conducted, a low-impedance dummy load loop is provided for the closed-loop output circuit, leakage inductance energy of a transformer is consumed through the low-impedance loop, the output voltage of the positive output end of the switching power supply is pulled down, the output voltage is continuously lower than an output voltage set value, the control circuit of the switching power supply detects that the voltage of the closed-loop output circuit is abnormal, and therefore the switching power supply enters a short-circuit protection state, and the reliability of the switching power supply is improved;
when the short circuit of the open loop output path of the positive and negative two-way output switching power supply is abnormally withdrawn, the output voltage of the switching power supply is recovered to be normal, and as long as the resistance value of the resistor R1 is larger than that of the resistor R2, the voltage of the base electrode of the triode Q1 relative to the output ground terminal is changed into negative pressure, the triode Q1 is cut off, and the serial branch of the resistor R1 and the resistor R2 is used as a dummy load of the output end of the positive and negative two-way output switching power supply. Because the resistor R1 and the resistor R2 only need to provide uA-level base current for the triode Q1, the resistor R1 and the resistor R2 can select higher resistance values, so that the current flowing through the resistor R1 and the resistor R2 is uA-level, the static power consumption of the switching power supply is further reduced, the switching power supply conversion efficiency is improved, and meanwhile, the problem of local heating caused by loss of the switching power supply can be further reduced.
Second embodiment
Fig. 3 is a schematic circuit diagram of a second embodiment of a dummy load switching circuit applied to a switching power supply according to the present utility model, wherein the difference between the present embodiment and the first embodiment is that: and a third voltage dividing resistor R3 is added, one end of the resistor R3 is connected with one end of the resistor R1, one end of the capacitor C1 and the cathode of the diode D1, and is used for being connected with the positive output end of the switching power supply, and the other end of the resistor R3 is connected with the collector of the triode Q1.
This embodiment is similar in principle to the first embodiment, except that: when the open-loop output path of the positive-negative two-way output switching power supply is short-circuited, the triode Q1 is conducted, the resistor R3 is used as a part of a low-impedance dummy load loop, and leakage inductance energy of the transformer is consumed, so that the triode Q1 is prevented from being damaged due to overcurrent, and the triode Q1 is also convenient to select.
The foregoing is illustrative of the preferred embodiments of the present utility model, and it should be noted that the foregoing is not to be construed as limiting the utility model, and that modifications and adaptations to those skilled in the art may be made without departing from the spirit and scope of the utility model, which is also intended to be covered by the appended claims.
Claims (10)
1. The utility model provides a dummy load switching circuit, is applied to positive and negative double-circuit output switching power supply which characterized in that: the switching power supply comprises a first dummy load branch and a second dummy load branch, wherein a first input end of the first dummy load branch is connected with one end of the second dummy load branch and is used for being connected with a positive output end of the switching power supply, a second input end of the first dummy load branch is connected with a voltage division point of the second dummy load branch, an output end of the first dummy load branch is grounded, and the other end of the second dummy load branch is used for being connected with a negative output end of the switching power supply; when the negative output end of the switching power supply is short-circuited, the first dummy load branch is switched to serve as a dummy load of the positive and negative double-circuit output switching power supply so as to pull down the output voltage of the positive output end of the switching power supply; and when the switching power supply works normally, switching to the second dummy load branch as the dummy load of the positive and negative double-way output switching power supply so as to improve the dummy load impedance.
2. The dummy load switching circuit of claim 1, wherein: the first dummy load branch circuit comprises a first switch tube, one end of the first switch tube is a first input end of the first dummy load branch circuit, the control end is a second input end of the first dummy load branch circuit, and the other end of the first switch tube is an output end of the first dummy load branch circuit.
3. The dummy load switching circuit of claim 1, wherein: the first dummy load branch circuit comprises a first switch tube and a voltage dividing resistor R3, one end of the resistor R3 is a first input end of the first dummy load branch circuit, the other end of the resistor R3 is connected with one end of the first switch tube, the control end of the first switch tube is a second input end of the first dummy load branch circuit, and the other end of the first switch tube is an output end of the first dummy load branch circuit.
4. A dummy load switching circuit according to claim 2 or claim 3, wherein: the first switching tube is an NPN triode Q1, the collector electrode of the triode Q1 is one end of the first switching tube, the base electrode is the control end of the first switching tube, and the emitter electrode is the other end of the first switching tube.
5. The dummy load switching circuit of claim 1, wherein: the second dummy load branch circuit comprises a first voltage dividing device and a second voltage dividing device, one end of the first voltage dividing device is one end of the second dummy load branch circuit, the other end of the first voltage dividing device is connected with one end of the second voltage dividing device to serve as a voltage dividing point of the second dummy load branch circuit, and the other end of the second voltage dividing device is the other end of the second dummy load branch circuit.
6. The dummy load switching circuit of claim 5, wherein: the first voltage dividing device and/or the second voltage dividing device is/are a resistor.
7. The utility model provides a dummy load switching circuit, is applied to positive and negative double-circuit output switching power supply which characterized in that: the switching power supply comprises a first output winding, a second output winding, a first rectifying tube, a second rectifying tube, a first filter capacitor C1, a second filter capacitor C2, a positive output end and a negative output end, and is characterized in that: the dummy load switching circuit comprises a first voltage dividing resistor R1, a second voltage dividing resistor R2 and a switching tube Q1; the same-name end of the first output winding is connected with one end of the first rectifying tube, the other end of the first rectifying tube is connected with one end of the capacitor C1, one end of the resistor R1 and one end of the switching tube Q1 and is used for being connected with a positive output end of a switching power supply, the other end of the resistor R1 is connected with one end of the resistor R2 and a control end of the switching tube Q1, the different-name end of the first output winding is connected with the same-name end of the second output winding, the other end of the capacitor C1, one end of the capacitor C2 and the other end of the switching tube Q1 are used for being grounded, the different-name end of the second output winding is connected with one end of the second rectifying tube, and the other end of the second rectifying tube is connected with the other end of the capacitor C2 and the other end of the resistor R2 and is used for being connected with a negative output end of the switching power supply.
8. The utility model provides a dummy load switching circuit, is applied to positive and negative double-circuit output switching power supply which characterized in that: the switching power supply comprises a first output winding, a second output winding, a first rectifying tube, a second rectifying tube, a first filter capacitor C1, a second filter capacitor C2, a positive output end and a negative output end, and is characterized in that: the dummy load switching circuit comprises a first voltage dividing resistor R1, a second voltage dividing resistor R2, a third voltage dividing resistor R3 and a switching tube Q1; the same-name end of the first output winding is connected with one end of the first rectifying tube, the other end of the first rectifying tube is connected with one end of the capacitor C1, one end of the resistor R1 and one end of the resistor R3 and is used for being connected with a positive output end of a switching power supply, the other end of the resistor R3 is connected with one end of the switching tube Q1, the other end of the resistor R1 is connected with one end of the resistor R2 and a control end of the switching tube Q1, the different-name end of the first output winding is connected with the same-name end of the second output winding, the other end of the capacitor C1, one end of the capacitor C2 and the other end of the switching tube Q1 are grounded, the different-name end of the second output winding is connected with one end of the second rectifying tube, and the other end of the resistor R2 are connected with the other end of the second rectifying tube and are used for being connected with a negative output end of the switching power supply.
9. The dummy load switching circuit according to claim 7 or claim 8, wherein: the first rectifying tube is a diode D1, the anode of the diode D1 is one end of the first rectifying tube, and the cathode of the diode D1 is the other end of the first rectifying tube; the second rectifying tube is a diode D2, the cathode of the diode D2 is one end of the second rectifying tube, and the anode of the diode D2 is the other end of the second rectifying tube; the switching tube Q1 is an NPN triode, the collector electrode of the triode is one end of the switching tube, the base electrode of the triode is the control end of the switching tube, and the emitter electrode of the triode is the other end of the switching tube.
10. A switching power supply, characterized by: comprising a dummy load switching circuit according to any of claims 1 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202223100790.XU CN219145247U (en) | 2022-11-22 | 2022-11-22 | Dummy load switching circuit and switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202223100790.XU CN219145247U (en) | 2022-11-22 | 2022-11-22 | Dummy load switching circuit and switching power supply |
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| Publication Number | Publication Date |
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| CN219145247U true CN219145247U (en) | 2023-06-06 |
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| CN202223100790.XU Active CN219145247U (en) | 2022-11-22 | 2022-11-22 | Dummy load switching circuit and switching power supply |
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| CN (1) | CN219145247U (en) |
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