CN210578268U - Secondary side active clamping circuit - Google Patents
Secondary side active clamping circuit Download PDFInfo
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- CN210578268U CN210578268U CN201921777596.0U CN201921777596U CN210578268U CN 210578268 U CN210578268 U CN 210578268U CN 201921777596 U CN201921777596 U CN 201921777596U CN 210578268 U CN210578268 U CN 210578268U
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Abstract
The utility model relates to an active clamp circuit of secondary side, including transformer, power switch tube, clamp circuit, switch circuit and current-limiting circuit, power switch tube's leakage is connected with the primary coil of transformer, power switch tube's source ground, and power switch tube's grid and PWM signal connection, clamp circuit's input and the different name end in the vice limit of transformer are connected, clamp circuit's output and switch circuit's input are connected, switch circuit's output is connected with switching power supply output through current-limiting circuit, and switch circuit's control end and the vice limit of transformer are connected with the same name end. The utility model discloses can transmit the secondary side with the remanence ability of transformer, realize carrying out the clamper to the voltage on the rectifier tube, improve switching power supply efficiency.
Description
Technical Field
The utility model relates to a DC/DC switching power supply field, concretely relates to active clamp circuit of secondary side.
Background
Since the active clamping circuit is provided, the active clamping circuit occupies an important position in the field of switching power supplies, and can clamp the voltage of a power switching tube to enable the power switching tube to be in a soft switching state, so that the efficiency of the switching power supply is improved, and the requirement of the power switching tube is reduced.
The active clamping circuit mainly utilizes MOS (metal oxide semiconductor) transistors as clamping switch transistors, the active clamping circuit is mostly used at the primary side of a switching power supply transformer, and all large chip design companies in the world release own active clamping circuit control chips based on the primary side and used for controlling the clamping switch MOS transistors and the power switch MOS transistors. The current source clamping circuit cannot clamp the voltage on the rectifier tube, and the efficiency of the switch power supply which can be realized by the current source clamping circuit is low.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide an active clamp circuit of secondary side can transmit the secondary side with the remanence ability of transformer, realizes carrying out the clamper to the voltage on the rectifier tube, improves switching power supply efficiency.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
a secondary side active clamping circuit comprises a transformer and a power switch tube, wherein a drain of the power switch tube is connected with a primary coil of the transformer, a source electrode of the power switch tube is grounded, a grid electrode of the power switch tube is connected with a PWM signal, the secondary side active clamping circuit further comprises a clamping circuit, a switching circuit and a current limiting circuit, an input end of the clamping circuit is connected with a secondary side synonym end of the transformer, an output end of the clamping circuit is connected with an input end of the switching circuit, an output end of the switching circuit is connected with an output end of a switching power supply through the current limiting circuit, and a control end of the switching circuit is connected with a secondary side synonym end of the transformer.
As a further improvement of the above technical solution:
the clamping circuit comprises a diode D3 and a capacitor C1, the anode of the diode D3 is connected with the unlike end of the secondary side of the transformer, the cathode of the diode D3 is connected with the input end of the switch circuit, one end of the capacitor C1 is connected with the cathode of the diode D3, and the other end of the capacitor C1 is grounded.
The switching circuit comprises a triode Q1 and a resistor R1, the base electrode of the triode Q1 is connected with the like end of the secondary side of the transformer through the resistor R1, the collector electrode of the triode Q1 is connected with the output end of the clamping circuit, and the emitter electrode of the triode Q1 is connected with the input end of the current limiting circuit.
The current limiting circuit comprises a diode D4 and an inductor L2, the anode of the diode D4 is grounded, the cathode of the diode D4 is connected with one end of an inductor L2, the other end of the inductor L2 is connected with the output end of the switching power supply, and the node between the diode D4 and the inductor L2 is the input end of the current limiting circuit.
According to the above technical scheme, the active clamp circuit of secondary side, not only can transmit the secondary side with the remanence ability of transformer, can also carry out the clamper to the voltage on the rectifier tube to it is in soft off-state, reduces the requirement of rectifier tube, improves switching power supply efficiency. The utility model discloses a switch tube control is simple, by transformer direct control, need not special controller chip, has promoted the new development of active clamp technique, and simultaneously, the clamp switch adopts bipolar transistor, has promoted active clamp circuit's anti irradiation ability.
Drawings
FIG. 1 is a block diagram illustrating the application of the present invention;
fig. 2 is a circuit diagram of the present invention.
Detailed Description
The present invention will be further explained with reference to the accompanying drawings:
as shown in fig. 1, the secondary side active clamp circuit of this embodiment includes a clamp circuit 1, a switch circuit 2 and a current limiting circuit 3, and in a specific application, the switch circuit 2 includes a transformer, a power switch tube and a rectification filter circuit, wherein a drain of the power switch tube is connected to a primary coil of the transformer T, a source of the power switch tube T is grounded, a gate of the power switch tube G is connected to a PWM signal, an input terminal of the clamp circuit 1 is connected to a different name terminal of a secondary side of the transformer T, an output terminal of the clamp circuit 1 is connected to an input terminal of the switch circuit 2, an output terminal of the switch circuit 2 is connected to an output terminal of the switching power supply through the current limiting circuit 3, and a control terminal of the switch circuit 2 is connected to a same name terminal of the secondary side of the.
As shown in fig. 2, the clamp circuit 1 of the present embodiment includes a diode D3 and a capacitor C1, an anode of the diode D3 is connected to the secondary-side synonym terminal of the transformer T, a cathode of the diode D3 is connected to the input terminal of the switch circuit 2, one end of the capacitor C1 is connected to the cathode of the diode D3, and the other end of the capacitor C1 is grounded.
When the power switch tube G1 is turned off, the potential of the opposite end of the secondary side of the transformer T1 is higher than the potential of the same end of the secondary side, the residual magnetic energy of the transformer T1 charges the clamping capacitor C1 through the diode D3, at this time, the leakage inductance of the transformer T resonates with the clamping capacitor C1, the residual magnetic energy of the transformer T flows to the clamping capacitor C1 in a resonant manner, the rectifier tube D1 is clamped, and the drain voltage of the power switch tube G1 is also clamped because the residual magnetic energy is quickly transferred to the clamping capacitor C1. When the current is reversely resonated, the residual magnetic energy of the transformer T is transferred to the clamping capacitor C1 and converted into electric energy for storage because the presence of the diode D3 is prevented.
The switch circuit 2 is composed of a triode Q1 and a resistor R1, the base electrode of the triode Q1 is connected with the same name end of the secondary side of the transformer T through the resistor R1, the collector electrode of the triode Q1 is connected with the node between the diode D3 and the capacitor C1, and the emitter electrode of the triode Q1 is connected with the cathode of the diode D4.
When the power switch G1 is turned on, the switch circuit 2 is configured to make the switch Q1 turned on when the dotted terminal of the transformer T is higher than the dotted terminal, so that the electric energy stored in the capacitor C1 is discharged to the load. The switching tube Q1 of the present embodiment adopts a bipolar transistor, which can improve the radiation resistance of the active clamp circuit.
The current limiting circuit 3 is composed of a diode D4 and an inductor L2, the anode of the diode D4 is grounded, the cathode of the diode D4 is connected with one end of the inductor L2, the other end of the inductor L2 is connected with the output end of the switching power supply, and the node between the diode D4 and the inductor L2 is the input end of the current limiting circuit 3.
The current limiting circuit 3 is used for solving the problem that the leakage current is too large instantaneously due to the potential difference between the potential of the clamping capacitor C1 and the output end of the switching power supply by utilizing the choking effect of the inductor L2 when the triode Q1 is conducted, and the diode D4 is used for magnetic reset of the inductor L2.
The utility model discloses a theory of operation:
when the power switch tube G1 is cut off, the potential of the different-name end of the secondary side of the transformer T1 is higher than the potential of the same-name end of the secondary side, the diode D3 is conducted, the leakage inductance of the transformer T and the clamping capacitor C1 resonate and discharge to the clamping capacitor C1, the rectifier tube D1 is in soft turn-off and the voltage is clamped, and the residual magnetic energy of the transformer T is transferred to the clamping capacitor C1 to form electric energy; at this time, the transistor Q1 is in an off state, the diode D4 is turned on, and the inductor L2 discharges to the load and magnetically resets.
When the power switch tube G1 is switched on, the potential of the dotted terminal of the secondary side of the transformer T1 is higher than the potential of the dotted terminal of the secondary side, the diode D3 is cut off, the potential of the dotted terminal of the secondary side of the transformer T1 is higher than the potential of the emitter of the triode Q1, the triode Q1 is switched on, the clamping capacitor C1 resonates with the inductor L2, and the inductor L2 discharges electricity to the load, so that the residual magnetic energy of the transformer T is discharged to the load.
The above-mentioned embodiments are only for describing the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art without departing from the design spirit of the present invention should fall into the protection scope defined by the claims of the present invention.
Claims (4)
1. A secondary side active clamping circuit comprises a transformer and a power switch tube, wherein the drain of the power switch tube is connected with the primary coil of the transformer, the source of the power switch tube is grounded, and the grid of the power switch tube is connected with a PWM signal, and the secondary side active clamping circuit is characterized in that: the transformer control circuit is characterized by further comprising a clamping circuit, a switching circuit and a current limiting circuit, wherein the input end of the clamping circuit is connected with the different-name end of the secondary side of the transformer, the output end of the clamping circuit is connected with the input end of the switching circuit, the output end of the switching circuit is connected with the output end of the switching power supply through the current limiting circuit, and the control end of the switching circuit is connected with the same-name end of the secondary side of the transformer.
2. The secondary-side active clamp circuit of claim 1, wherein: the clamping circuit comprises a diode D3 and a capacitor C1, the anode of the diode D3 is connected with the unlike end of the secondary side of the transformer, the cathode of the diode D3 is connected with the input end of the switch circuit, one end of the capacitor C1 is connected with the cathode of the diode D3, and the other end of the capacitor C1 is grounded.
3. The secondary-side active clamp circuit of claim 1 or 2, wherein: the switching circuit comprises a triode Q1 and a resistor R1, the base electrode of the triode Q1 is connected with the like end of the secondary side of the transformer through the resistor R1, the collector electrode of the triode Q1 is connected with the output end of the clamping circuit, and the emitter electrode of the triode Q1 is connected with the input end of the current limiting circuit.
4. The secondary-side active clamp circuit of claim 1, wherein: the current limiting circuit comprises a diode D4 and an inductor L2, the anode of the diode D4 is grounded, the cathode of the diode D4 is connected with one end of an inductor L2, the other end of the inductor L2 is connected with the output end of the switching power supply, and the node between the diode D4 and the inductor L2 is the input end of the current limiting circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921777596.0U CN210578268U (en) | 2019-10-22 | 2019-10-22 | Secondary side active clamping circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921777596.0U CN210578268U (en) | 2019-10-22 | 2019-10-22 | Secondary side active clamping circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN210578268U true CN210578268U (en) | 2020-05-19 |
Family
ID=70661792
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201921777596.0U Active CN210578268U (en) | 2019-10-22 | 2019-10-22 | Secondary side active clamping circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN210578268U (en) |
-
2019
- 2019-10-22 CN CN201921777596.0U patent/CN210578268U/en active Active
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