CN210380686U - Flyback power supply circuit - Google Patents
Flyback power supply circuit Download PDFInfo
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- CN210380686U CN210380686U CN201920227478.6U CN201920227478U CN210380686U CN 210380686 U CN210380686 U CN 210380686U CN 201920227478 U CN201920227478 U CN 201920227478U CN 210380686 U CN210380686 U CN 210380686U
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- 238000001514 detection method Methods 0.000 claims abstract description 121
- 238000004804 winding Methods 0.000 claims abstract description 94
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- 239000003990 capacitor Substances 0.000 claims description 48
- 238000010521 absorption reaction Methods 0.000 claims description 43
- 238000001914 filtration Methods 0.000 claims description 21
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- 230000005347 demagnetization Effects 0.000 claims description 10
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- 238000010586 diagram Methods 0.000 description 16
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Abstract
The present disclosure relates to flyback power supply circuits. The flyback power supply circuit with three windings of the transformer is characterized by comprising the following components: the control circuit is used for controlling the turn-off of the power switching tube through negative pressure detection; the control circuit comprises a driving pin, a grounding pin, a feedback control pin, a power supply pin, a current detection pin, a suspension pin and a power switch drain pin.
Description
Technical Field
The utility model relates to a circuit field, more specifically relates to a flyback power supply circuit.
Background
As the market demand for low end chargers increases, there is a need to control and reduce the cost of the charger. However, the conventional charger has relatively many components, and the cost is difficult to reduce. In addition, with the miniaturization of the charger, the system PCB layout is difficult.
Against this background, a power supply circuit which is miniaturized, low in cost, and high in power density is required.
SUMMERY OF THE UTILITY MODEL
An embodiment of the utility model provides a transformer three-winding's flyback power supply circuit, a serial communication port, include: the control circuit is used for controlling the turn-off of the power switching tube through negative pressure detection; the control circuit comprises a driving pin, a grounding pin, a feedback control pin, a power supply pin, a current detection pin, a suspension pin and a power switch drain pin; the driving pin is connected with the output end of the starting circuit and used for providing working starting voltage of the control circuit; the grounding pin is connected with the first end of the feedback circuit, the second end of the current detection circuit and the negative end of the Vcc capacitor; the feedback control pin is connected with the third end of the feedback circuit and is used for output voltage feedback detection, demagnetization pulse width detection, output overvoltage protection and output undervoltage protection; the power supply pin is connected with the positive end of the Vcc capacitor and used for providing working voltage; the current detection pin is connected with the first end of the current detection circuit, the lower end of the auxiliary winding of the transformer and the output negative end of the EMI filter circuit and is used for detecting current in a negative voltage detection mode; the suspension foot is suspended; and the drain pin of the power switch is connected with the lower end of the primary winding of the transformer and the second end of the absorption circuit and is used for realizing the on-off of the power switch tube through the internal control of the control circuit.
In one embodiment, the flyback power supply circuit further includes: the circuit comprises an alternating current rectifying circuit, an EMI filtering circuit, a starting circuit, a feedback circuit, a current detection circuit, an absorption circuit, a transformer and an output rectifying and filtering circuit.
In one embodiment, the feedback circuit includes a sampling resistor for sensing the output voltage to provide to the control circuit; the first end of the feedback circuit is connected with the second end of the current detection circuit, the negative end of the Vcc capacitor and the grounding pin of the control circuit, the second end of the feedback circuit is connected with the upper end of the auxiliary winding of the transformer, and the third end of the feedback circuit is connected with the feedback control pin of the control circuit.
In one embodiment, the current detection circuit comprises a current detection resistor for outputting different currents by adjusting the size of the current detection resistor; the first end of the current detection circuit is connected with the lower end of the auxiliary winding of the transformer, the output negative end of the EMI filter circuit and the current detection pin of the control circuit, and the second end of the current detection circuit is connected with the first end of the feedback circuit, the negative end of the Vcc capacitor and the grounding pin of the control circuit.
In one embodiment, the transformer includes a primary winding, an auxiliary winding, and a secondary winding for transforming a voltage; the upper end of a primary winding of the transformer is connected with the first end of the absorption circuit, the input end of the starting circuit and the output positive end of the EMI filter circuit, the lower end of the primary winding of the transformer is connected with the second end of the absorption circuit and the drain electrode pin of the power switch of the control circuit, the upper end of an auxiliary winding of the transformer is connected with the second end of the feedback circuit, the lower end of the auxiliary winding of the transformer is connected with the output negative end of the EMI filter circuit, the first end of the current detection circuit and the current detection pin of the control circuit, and the upper end and the lower end of a secondary winding of the transformer are respectively connected with the two input ends of the output rectification filter circuit.
In one embodiment, the control circuit is an OB2514X control chip.
The embodiment of the utility model provides a still provide a flyback power supply circuit of two windings of transformer, include: the control circuit is used for controlling the turn-off of the power switching tube through negative pressure detection; the control circuit comprises a driving pin, a grounding pin, a feedback control pin, a power supply pin, a current detection pin, a suspension pin and a power switch drain pin, wherein the driving pin is connected with the output end of the starting circuit and used for providing working starting voltage of the control circuit; the grounding pin is connected with the first end of the feedback circuit, the second end of the current detection circuit and the negative end of the Vcc capacitor; the feedback control pin is connected with the third end of the feedback circuit and is used for output voltage feedback detection, demagnetization pulse width detection, output overvoltage protection and output undervoltage protection; the power supply pin is connected with the positive end of the Vcc capacitor and used for providing working voltage; the current detection pin is connected with the first end of the current detection circuit, the first end of the absorption circuit and the upper end of the primary winding of the transformer and is used for detecting current in a negative voltage detection mode; the suspension foot is suspended; and the drain pin of the power switch is connected with the output positive terminal of the EMI filter circuit and the input terminal of the starting circuit, and is used for realizing the on-off of the power switch tube through the internal control of the control circuit.
In one embodiment, the flyback power supply circuit further includes: the circuit comprises an alternating current rectifying circuit, an EMI filtering circuit, a starting circuit, a feedback circuit, a current detection circuit, an absorption circuit, a transformer and an output rectifying and filtering circuit.
In one embodiment, the feedback circuit includes a sampling resistor for sensing the output voltage to provide to the control circuit; the first end of the feedback circuit is connected with the second end of the current detection circuit, the negative end of the Vcc capacitor and the grounding pin of the control circuit, the second end of the feedback circuit is connected with the output negative end of the EMI filter circuit, the second end of the absorption circuit and the lower end of the primary winding of the transformer, and the third end of the feedback circuit is connected with the feedback control pin of the control circuit.
In one embodiment, the current detection circuit comprises a current detection resistor for outputting different currents by adjusting the size of the current detection resistor; the first end of the current detection circuit is connected with the current detection pin of the control circuit, the first end of the absorption circuit and the upper end of the primary winding of the transformer, and the second end of the current detection circuit is connected with the first end of the feedback circuit, the negative end of the Vcc capacitor and the grounding pin of the control circuit.
In one embodiment, the transformer includes a primary winding and a secondary winding for transforming a voltage; the upper end of the primary winding of the transformer is connected with the first end of the current detection circuit, the current detection pin of the control circuit and the first end of the absorption circuit, the lower end of the primary winding of the transformer is connected with the output negative end of the EMI filter circuit, the second end of the feedback circuit and the second end of the absorption circuit, and the upper end and the lower end of the secondary winding of the transformer are respectively connected with the two input ends of the output rectifying filter circuit.
In one embodiment, the control circuit is an OB2514X control chip.
According to the utility model discloses flyback power supply circuit provides current detection resistance Rs voltage VCSNegative voltage detection, removal of the external charging loop of capacitor C1 (including rectifier diode and current limiting resistor), and simultaneous transformer two-winding and three-winding applications. The flyback power supply circuit can save a rectifier diode and a current-limiting resistor of an external charging loop of the capacitor C1, and can further save a Naux winding of a transformer, thereby greatly reducing the system cost and improving the power density of the system.
Drawings
The invention may be better understood from the following description of particular embodiments thereof taken in conjunction with the accompanying drawings, in which:
fig. 1 is a diagram showing a power supply circuit of a conventional charger.
Fig. 2 is a diagram illustrating a flyback power supply circuit for a transformer three-winding in accordance with an embodiment of the present invention.
Fig. 3 is a diagram illustrating a filter circuit according to an embodiment of the present invention.
Fig. 4 is a composite functional block diagram illustrating a feedback pin of a control circuit according to an embodiment of the present invention.
Fig. 5 is a diagram illustrating an absorption circuit according to an embodiment of the present invention.
Fig. 6 is a diagram illustrating an output rectifying and filtering circuit according to an embodiment of the present invention.
Fig. 7 is a diagram illustrating a flyback power supply circuit for two windings of a transformer according to an embodiment of the present invention.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. In the drawings, the thickness of regions and layers may be exaggerated for clarity. In the drawings, the same reference numerals denote the same or similar structures, and thus detailed descriptions thereof will be omitted.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the main technical ideas of the invention.
Fig. 1 is a diagram showing a power supply circuit of a conventional charger. As shown in fig. 1, a current detection resistor RSVoltage VCSFor forward voltage detection, the Naux winding charges a capacitor C1 through a current-limiting resistor and a rectifier diode and then supplies power to U1.
According to the utility model discloses flyback power supply circuit provides current detection resistance RSVoltage VCSFor negative voltage detection, the external charging loop (including rectifier diode and current limiting resistor) of the capacitor C1 is removed, and the two-winding and three-winding application schemes of the transformer are considered simultaneously. The flyback power supply circuit can save a rectifier diode and a current-limiting resistor of an external power supply loop of the capacitor C1, can further save a Naux power supply winding of a transformer, greatly reduces the system cost, and simultaneously improves the power density of the system.
Fig. 2 is a diagram illustrating a flyback power supply circuit for a transformer three-winding in accordance with an embodiment of the present invention. As shown in fig. 2, the flyback power circuit according to the embodiment of the present invention can adopt R in the case of three windings of the transformerSVoltage VCSThe rectifying diode and current limiting resistor of the external charging loop of capacitor C1 are removed for negative voltage detection.
In an embodiment, the flyback power supply circuit according to the embodiment of the present invention may include: the circuit comprises an alternating current rectification circuit 1, an EMI filter circuit 2, a starting circuit 3, a feedback circuit 4, a current detection circuit 5, a control circuit 6, an absorption circuit 7, a transformer 8 and an output rectification filter circuit 9.
In an embodiment, two input terminals of the AC rectification circuit 1 may be connected to the AC input, and two output terminals of the AC rectification circuit 1 may be connected to the input positive terminal and the input negative terminal of the EMI filter circuit 2 (i.e., the positive terminal of the DC bulk capacitor and the negative terminal of the DCbulk capacitor), respectively.
In an embodiment, the ac rectification circuit 1 may include: FUSE and rectifier diode for rectifying the alternating voltage. The number of rectifier diodes may be a minimum of two and a maximum of four. The fuse may also be replaced by a fuse resistor or a wire resistor or an inductor.
In an embodiment, the positive input terminal and the negative input terminal of the EMI filter circuit 2 (i.e., the positive terminal of the DC bulk capacitor and the negative terminal of the DCbulk capacitor) may be connected to two output terminals of the ac rectifier circuit 1. The positive output terminal of the EMI filter circuit 2 may be connected to the input terminal of the start circuit 3, the first terminal of the absorption circuit 7, and the upper end of the primary winding Np of the transformer 8, and the negative output terminal of the EMI filter circuit 2 may be connected to the first terminal of the current detection circuit 5, the lower end of the auxiliary winding Naux of the transformer 8, and the current detection pin E of the control circuit 6.
In an embodiment, the EMI filter circuit 2 may include: the high-voltage electrolytic capacitor is used for suppressing EMI and filtering after rectification. Depending on the application, the inductors may comprise two inductors, or one common-mode inductor; the high-voltage electrolytic capacitors can be one or two; ESD discharge resistor R1 may be one or removed. Fig. 3 is various connections of a filter circuit, where R1 is an ESD discharge resistor and may be connected in series or in parallel to achieve a desired resistance value, or may be removed.
In an embodiment, the input terminal of the start-up circuit 3 may be connected to the positive output terminal of the EMI filter circuit 2, the first terminal of the absorption circuit 7, and the upper terminal of the primary winding Np of the transformer 8, and the output terminal of the start-up circuit 3 may be connected to the driving pin a of the control circuit 6.
In an embodiment, the start-up circuit 3 may include: and starting the resistor. The rectified DC Bulk voltage positive terminal provides the operating start voltage to the control circuit 6 through the start resistor and pin a of the control circuit 6.
In an embodiment, a first terminal of the feedback circuit 4 may be connected to the second terminal of the current detection circuit 5, the negative terminal of the Vcc capacitor C1, and the ground pin B of the control circuit 6, a second terminal of the feedback circuit 4 may be connected to the upper terminal of the auxiliary winding Naux of the transformer 8, and a third terminal of the feedback circuit 4 may be connected to the feedback control pin C of the control circuit 6.
In an embodiment, the feedback circuit 4 may include: the sampling resistor is used for proportionally sensing the secondary alternating voltage through an auxiliary winding Naux (shown in FIG. 2) of the transformer 8, and the secondary alternating voltage is sent to a feedback control pin C of the control circuit 6 through the sampling resistor. In principle, no optical coupler and no secondary reference voltage stabilizer exist, so that the cost is greatly reduced. The sampling resistors can be connected in series or in parallel to achieve the required resistance.
In an embodiment, a first terminal of the current detection circuit 5 may be connected to a lower terminal of the auxiliary winding Naux of the transformer 8, an output negative terminal of the EMI filter circuit 2, and a current detection pin E of the control circuit 6, and a second terminal of the current detection circuit 5 is connected to a first terminal of the feedback circuit 4, a negative terminal of the Vcc capacitor C1, and a ground pin B of the control circuit 6.
In an embodiment, the current detection circuit 5 may include: and the current detection resistor is used for outputting different currents by adjusting the size of the current detection resistor.
In an embodiment, the control circuit 6 may comprise 8 functional pins: the circuit comprises a driving pin A, a grounding pin B, a feedback control pin C, a power supply pin D, a current detection pin E, a suspension pin F and a power switch drain pin G/H. The drive pin a of the control circuit 6 may be connected to the output of the start-up circuit 3. Ground pin B of control circuit 6 may be connected to the second terminal of current sensing circuit 5, the first terminal of feedback circuit 4, and the negative terminal of Vcc capacitor C1. The feedback control pin C of the control circuit 6 may be connected to a third terminal of the feedback circuit 4. The supply pin D of the control circuit 6 may be connected to the positive terminal of a capacitor C1. The current detection pin E of the control circuit 6 may be connected to the lower end of the auxiliary winding Naux of the transformer 8, the output negative terminal of the EMI filter circuit 2, and the first terminal of the current detection circuit 5. The free leg F of the control circuit 6 may be free. The power switch drain pin G/H of the control circuit 6 may be connected to the lower end of the primary winding Np of the transformer 8 and to the second end of the absorption circuit 7.
In an embodiment, the control circuit 6 may include: a primary feedback PWM control and Power switching tube, a Power Switch (Power Switch) packaged with SOP7/8, and necessary peripheral accessories, such as OB2514X or similar functional control chips.
In an embodiment, the driving pin a of the control circuit 6 may be used to provide an operation start voltage of the control circuit 6.
In an embodiment, the feedback control pin C of the control circuit 6 may be a multi-function pin, and a detailed functional block diagram is shown in fig. 4. The feedback control pin implements the following 4 functions: 1) output voltage feedback detection: in the demagnetization time, the platform voltage is sampled through a sampling circuit (namely, a feedback circuit 4), the voltage is in a proportional relation with the output voltage, and the voltage is controlled to realize constant-voltage CV control; 2) and (3) demagnetization pulse width detection: detecting the rising edge and the falling edge of the demagnetization pulse width to realize constant current CC control; 3) output overvoltage protection: the sampling circuit can collect output voltage information and can realize output overvoltage protection through logic control; 4) output under-voltage protection: the sampling circuit can collect output voltage information, and output under-voltage protection can be realized through logic control.
In an embodiment, the supply pin D of the control circuit 6 may be used to provide the operating voltage. The current detection pin E of the control circuit 6 may be used to detect the current in a negative voltage detection manner. The free leg F of the control circuit 6 may be free. The power switch drain pin G/H of the control circuit 6 can be used for realizing the on and off of the power switch tube through the internal control of the control circuit 6.
In an embodiment, a first end of the absorption circuit 7 may be connected to an upper end of the primary winding Np of the transformer 8, an input end of the start circuit 3, and a positive output end of the EMI filter circuit 2, and a second end of the absorption circuit 7 may be connected to a lower end of the primary winding Np of the transformer 8 and a drain pin G/H of the power switch of the control circuit 6.
In an embodiment, the absorption circuit 7 may include a resistor, a capacitor, and a diode. In a practical application circuit, the circuit may vary according to different system requirements. The circuit can also be completely removed according to different market requirements, thereby further reducing the cost. Fig. 5 is a diagram illustrating an absorption circuit according to an embodiment of the present invention. The absorption circuit may have a variety of connections.
In an embodiment, the upper end of the primary winding Np of the transformer 8 may be connected to the first end of the absorption circuit 7, the input end of the start circuit 3, and the positive output end of the EMI filter circuit 2, and the lower end of the primary winding Np of the transformer 8 may be connected to the second end of the absorption circuit 7 and the drain pin G/H of the power switch of the control circuit 6. The upper end and the lower end of the secondary winding Ns of the transformer 8 may be connected to two input terminals of the output rectifying and filtering circuit 9, respectively. The upper end of the auxiliary winding Naux of the transformer 8 may be connected to the second end of the feedback circuit 4. The lower end of the auxiliary winding Naux of the transformer 8 may be connected to the output negative terminal of the EMI filter circuit 2, the first terminal of the current detection circuit 5, and the current detection pin E of the control circuit 6.
In an embodiment, the transformer 8 may comprise: a primary winding Np, an auxiliary winding Naux and a secondary winding Ns (shown in fig. 2) for transforming the voltage.
In the embodiment, two input terminals of the output rectifying and smoothing circuit 9 are connected to the upper and lower terminals of the secondary winding Ns of the transformer. Two output ends of the output rectifying and filtering circuit 9 are connected with an output load.
In the embodiment, the output rectifying and filtering circuit 9 includes: the output rectifier diode and the filter capacitor are two main parts, and aiming at different output ripple requirements, the output filter circuit can be added with a pi-type filter circuit or a common-mode filter circuit. Fig. 6 is a diagram illustrating an output rectifying and filtering circuit according to an embodiment of the present invention. The output rectifying and filtering circuit may also be implemented in the manner of fig. 6.
Fig. 7 is a diagram illustrating a flyback power supply circuit for two windings of a transformer according to an embodiment of the present invention. As shown in fig. 7, the flyback power circuit according to the embodiment of the present invention can use the RS voltage VCS as the negative voltage detection under the condition of two windings of the transformer, and remove the rectifier diode, the current limiting resistor and the auxiliary winding Naux of the transformer of the external charging loop of the capacitor C1.
In an embodiment, the flyback power supply circuit according to the embodiment of the present invention may include: the circuit comprises an alternating current rectification circuit 1, an EMI filter circuit 2, a starting circuit 3, a feedback circuit 4, a current detection circuit 5, a control circuit 6, an absorption circuit 7, a transformer 8 and an output rectification filter circuit 9.
In an embodiment, two input terminals of the AC rectification circuit 1 may be connected to the AC input, and two output terminals of the AC rectification circuit 1 may be connected to the input positive terminal and the input negative terminal of the EMI filter circuit 2 (i.e., the positive terminal of the DC bulk capacitor and the negative terminal of the DCbulk capacitor), respectively.
In the embodiment, the alternating current rectification circuit 1 includes: FUSE and rectifier diode for rectifying the alternating voltage. The number of rectifier diodes may be a minimum of two and a maximum of four. The fuse may also be replaced by a fuse resistor or a wire resistor or an inductor.
In an embodiment, the positive input terminal and the negative input terminal of the EMI filter circuit 2 (i.e., the positive terminal of the DC bulk capacitor and the negative terminal of the DCbulk capacitor) may be connected to two output terminals of the ac rectifier circuit 1. The positive output terminal of the filter circuit 2 may be connected to the input terminal of the start circuit 3 and the drain pin G/H of the power switch of the control circuit 6, and the negative output terminal of the EMI filter circuit 2 may be connected to the second terminal of the feedback circuit 4, the second terminal of the absorption circuit 7, and the lower end of the primary winding Np of the transformer 8.
In an embodiment, the EMI filter circuit 2 may include: the high-voltage electrolytic capacitor is used for suppressing EMI and filtering after rectification. Depending on the application, the inductors may comprise two inductors, or one common-mode inductor; the high-voltage electrolytic capacitors can be one or two; ESD discharge resistor R1 may be one or removed. Fig. 3 is various connections of a filter circuit, where R1 is an ESD discharge resistor and may be connected in series or in parallel to achieve a desired resistance value, or may be removed.
In an embodiment, the input terminal of the start-up circuit 3 may be connected to the positive output terminal of the EMI filter circuit 2 and the drain pin G/H of the power switch of the control circuit 6, and the output terminal of the start-up circuit 3 is connected to the driving pin a of the control circuit 6.
In an embodiment, the start-up circuit 3 may include: and starting the resistor. The rectified DC Bulk voltage positive terminal provides the operating start voltage to the control circuit 6 through the start resistor and pin a of the control circuit 6.
In an embodiment, the first terminal of the feedback circuit 4 may be connected to the second terminal of the current detection circuit 5, the negative terminal of the Vcc capacitor C1, and the ground pin B of the control circuit 6. A second terminal of the feedback circuit 4 may be connected to a negative output terminal of the EMI filter circuit 2, a second terminal of the absorption circuit 7, and a lower terminal of a primary winding Np of the transformer 8. The third terminal of the feedback circuit 4 may be connected to a feedback control pin C of the control circuit 6.
In an embodiment, the feedback circuit 4 comprises: the sampling resistor is used for proportionally sensing the secondary alternating-current voltage through a primary winding Np (as shown in fig. 3) of the transformer 8, and the secondary alternating-current voltage is sent to a feedback control pin of the control circuit 6 through the sampling resistor. In principle, no optical coupler and no secondary reference voltage stabilizer exist, so that the cost is greatly reduced. The sampling resistors can be connected in series or in parallel to achieve the required resistance.
In an embodiment, a first terminal of the current detection circuit 5 may be connected to the current detection pin E of the control circuit 6, a first terminal of the snubber circuit 7, and an upper terminal of the primary winding Np of the transformer 8, and a second terminal of the current detection circuit 5 may be connected to the first terminal of the feedback circuit 4, a negative terminal of the Vcc capacitor C1, and a ground pin B of the control circuit 6.
In an embodiment, the current detection circuit 5 may include: and the current detection resistor is used for outputting different currents by adjusting the size of the current detection resistor.
In an embodiment, the control circuit 6 may comprise 8 functional pins: the circuit comprises a driving pin A, a grounding pin B, a feedback control pin C, a power supply pin D, a current detection pin E, a suspension pin F and a power switch drain pin G/H. The drive pin a of the control circuit 6 may be connected to the output of the start-up circuit 3. The ground pin B of the control circuit 6 may be connected to the first terminal of the feedback circuit 4, the second terminal of the current detection circuit 5, and the negative terminal of the Vcc capacitor C1. The feedback control pin C of the control circuit 6 may be connected to a third terminal of the feedback circuit 4. The supply pin D of the control circuit 6 may be connected to the positive terminal of the Vcc capacitor C1. The current detection pin E of the control circuit 6 may be connected to the upper end of the primary winding Np of the transformer 8, the first end of the absorption circuit 7, and the first end of the current detection circuit 5. The free leg F of the control circuit 6 may be free. The power switch drain pin G/H of the control circuit 6 may be connected to the positive output terminal of the EMI filter circuit 2 and the input terminal of the start-up circuit 3.
In an embodiment, the control circuit 6 may include: a primary feedback PWM control and Power switching tube, a Power Switch (Power Switch) packaged with SOP7/8, and necessary peripheral accessories, such as OB2514X or similar functional control chips.
In an embodiment, the driving pin a of the control circuit 6 may be used to provide an operation start voltage of the control circuit 6.
In the embodiment, the feedback control pin C of the control circuit 6 is a multi-function pin, and a detailed functional block diagram is shown in fig. 5. The feedback control pin implements the following 4 functions: 1) output voltage feedback detection: in the demagnetization time, the platform voltage is sampled through a sampling circuit (namely, a feedback circuit 4), the voltage is in a proportional relation with the output voltage, and the voltage is controlled to realize constant-voltage CV control; 2) and (3) demagnetization pulse width detection: detecting the rising edge and the falling edge of the demagnetization pulse width to realize constant current CC control; 3) output overvoltage protection: the sampling circuit can collect output voltage information and can realize output overvoltage protection through logic control; 4) output under-voltage protection: the sampling circuit can collect output voltage information, and output under-voltage protection can be realized through logic control.
In an embodiment, the supply pin D of the control circuit 6 may be used to provide the operating voltage. The current detection pin E of the control circuit 6 may be used to detect the current in a negative voltage detection manner. The free leg F of the control circuit 6 may be free. The power switch drain pin G/H of the control circuit 6 can be used for realizing the on and off of the power switch tube through the internal control of the control circuit 6.
In an embodiment, a first terminal of the absorption circuit 7 may be connected to the first terminal of the current detection circuit 5, the current detection pin E of the control circuit 6, and an upper end of the primary winding Np of the transformer 8, and a second terminal of the absorption circuit 7 may be connected to the output negative terminal of the EMI filter circuit 2, the second terminal of the feedback circuit 4, and a lower end of the primary winding Np of the transformer 8.
In an embodiment, the absorption circuit 7 comprises a resistor, a capacitor and a diode. In a practical application circuit, the circuit may vary according to different system requirements. The circuit can also be completely removed according to different market requirements, thereby further reducing the cost. Fig. 5 is a diagram illustrating an absorption circuit according to an embodiment of the present invention. The absorption circuit may have a variety of connections.
In an embodiment, an upper end of the primary winding Np of the transformer 8 may be connected to the first end of the current detection circuit 5, the current detection pin E of the control circuit 6, and the first end of the absorption circuit 7, and a lower end of the primary winding Np of the transformer 8 may be connected to the output negative terminal of the EMI filter circuit 2, the second end of the feedback circuit 4, and the second end of the absorption circuit 7. The positive terminal and the negative terminal of the secondary winding Ns of the transformer 8 may be connected to two input terminals of the output rectifying and filtering circuit 9, respectively.
In an embodiment, the transformer 8 comprises: primary winding, auxiliary winding (as shown in fig. 7).
In the embodiment, two input terminals of the output rectifying and smoothing circuit 9 are connected to the upper and lower terminals of the secondary winding Ns of the transformer. Two output ends of the output rectifying and filtering circuit 9 are connected with an output load.
In the embodiment, the output rectifying and filtering circuit 9 includes: the output rectifier diode and the filter capacitor are two main parts, and aiming at different output ripple requirements, the output filter circuit can be added with a pi-type filter circuit or a common-mode filter circuit. Fig. 6 is a diagram illustrating an output rectifying and filtering circuit according to an embodiment of the present invention. The output rectifying and filtering circuit may also be implemented in the manner of fig. 6.
According to the utility model discloses flyback power supply circuit provides Rs voltage Vcs and detects for the negative pressure, removes the outside charging circuit of electric capacity C1 (including rectifier diode and current-limiting resistor) to compromise two windings of transformer and three winding application schemes simultaneously. The flyback power supply circuit can save a rectifier diode and a current-limiting resistor of an external charging loop of the capacitor C1, can further save a Naux power supply winding of a transformer, greatly reduces the system cost, and simultaneously improves the power density of the system.
The invention is not limited to the specific configurations described above and shown in the figures. A detailed description of known configurations is omitted herein for the sake of brevity. The configuration of the present invention is not limited to the specific configuration described and illustrated, and various changes, modifications, and additions may be made by those skilled in the art after appreciating the spirit of the present invention.
Claims (12)
1. A flyback power supply circuit with three windings of a transformer is characterized by comprising the following components:
the control circuit is used for controlling the turn-off of the power switching tube through negative pressure detection;
the control circuit comprises a driving pin, a grounding pin, a feedback control pin, a power supply pin, a current detection pin, a suspension pin and a power switch drain pin; and is
The driving pin is connected with the output end of the starting circuit and used for providing working starting voltage of the control circuit;
the grounding pin is connected with the first end of the feedback circuit, the second end of the current detection circuit and the negative end of the Vcc capacitor;
the feedback control pin is connected with the third end of the feedback circuit and is used for output voltage feedback detection, demagnetization pulse width detection, output overvoltage protection and output undervoltage protection;
the power supply pin is connected with the positive end of the Vcc capacitor and used for providing working voltage;
the current detection pin is connected with the first end of the current detection circuit, the lower end of the auxiliary winding of the transformer and the output negative end of the EMI filter circuit and is used for detecting current in a negative voltage detection mode;
the suspension foot is suspended; and is
And the drain pin of the power switch is connected with the lower end of the primary winding of the transformer and the second end of the absorption circuit and is used for realizing the on-off of the power switch tube through the internal control of the control circuit.
2. The flyback power supply circuit of claim 1, further comprising: the circuit comprises an alternating current rectifying circuit, an EMI filtering circuit, a starting circuit, a feedback circuit, a current detection circuit, an absorption circuit, a transformer and an output rectifying and filtering circuit.
3. The flyback power supply circuit of claim 2, wherein the feedback circuit comprises a sampling resistor for sensing the output voltage for supply to the control circuit;
the first end of the feedback circuit is connected with the second end of the current detection circuit, the negative end of the Vcc capacitor and the grounding pin of the control circuit, the second end of the feedback circuit is connected with the upper end of the auxiliary winding of the transformer, and the third end of the feedback circuit is connected with the feedback control pin of the control circuit.
4. The flyback power supply circuit according to claim 2, wherein the current detection circuit includes a current detection resistor for outputting a different current by adjusting a size of the current detection resistor;
the first end of the current detection circuit is connected with the lower end of the auxiliary winding of the transformer, the output negative end of the EMI filter circuit and the current detection pin of the control circuit, and the second end of the current detection circuit is connected with the first end of the feedback circuit, the negative end of the Vcc capacitor and the grounding pin of the control circuit.
5. The flyback power supply circuit of claim 2, wherein the transformer comprises a primary winding, an auxiliary winding, and a secondary winding for transforming the voltage;
the upper end of a primary winding of the transformer is connected with the first end of the absorption circuit, the input end of the starting circuit and the output positive end of the EMI filter circuit, the lower end of the primary winding of the transformer is connected with the second end of the absorption circuit and the drain electrode pin of the power switch of the control circuit, the upper end of an auxiliary winding of the transformer is connected with the second end of the feedback circuit, the lower end of the auxiliary winding of the transformer is connected with the output negative end of the EMI filter circuit, the first end of the current detection circuit and the current detection pin of the control circuit, and the upper end and the lower end of a secondary winding of the transformer are respectively connected with the two input ends of the output rectification filter circuit.
6. The flyback power supply circuit of claim 1, wherein the control circuit is an OB2514X control chip.
7. A flyback power supply circuit of two windings of a transformer is characterized by comprising:
the control circuit is used for controlling the turn-off of the power switching tube through negative pressure detection;
wherein the control circuit comprises a driving pin, a grounding pin, a feedback control pin, a power supply pin, a current detection pin, a suspension pin and a power switch drain pin, and
the driving pin is connected with the output end of the starting circuit and used for providing working starting voltage of the control circuit;
the grounding pin is connected with the first end of the feedback circuit, the second end of the current detection circuit and the negative end of the Vcc capacitor;
the feedback control pin is connected with the third end of the feedback circuit and is used for output voltage feedback detection, demagnetization pulse width detection, output overvoltage protection and output undervoltage protection;
the power supply pin is connected with the positive end of the Vcc capacitor and used for providing working voltage;
the current detection pin is connected with the first end of the current detection circuit, the first end of the absorption circuit and the upper end of the primary winding of the transformer and is used for detecting current in a negative voltage detection mode;
the suspension foot is suspended; and is
The drain pin of the power switch is connected with the output positive terminal of the EMI filter circuit and the input terminal of the starting circuit, and is used for realizing the on-off of the power switch tube through the internal control of the control circuit.
8. The flyback power supply circuit of claim 7, further comprising: the circuit comprises an alternating current rectifying circuit, an EMI filtering circuit, a starting circuit, a feedback circuit, a current detection circuit, an absorption circuit, a transformer and an output rectifying and filtering circuit.
9. The flyback power supply circuit of claim 8, wherein the feedback circuit comprises a sampling resistor for sensing the output voltage for supply to the control circuit;
the first end of the feedback circuit is connected with the second end of the current detection circuit, the negative end of the Vcc capacitor and the grounding pin of the control circuit, the second end of the feedback circuit is connected with the output negative end of the EMI filter circuit, the second end of the absorption circuit and the lower end of the primary winding of the transformer, and the third end of the feedback circuit is connected with the feedback control pin of the control circuit.
10. The flyback power supply circuit of claim 8, wherein the current detection circuit comprises a current detection resistor for outputting a different current by adjusting a size of the current detection resistor;
the first end of the current detection circuit is connected with the current detection pin of the control circuit, the first end of the absorption circuit and the upper end of the primary winding of the transformer, and the second end of the current detection circuit is connected with the first end of the feedback circuit, the negative end of the Vcc capacitor and the grounding pin of the control circuit.
11. The flyback power supply circuit of claim 8, wherein the transformer comprises a primary winding and a secondary winding for transforming the voltage;
the upper end of the primary winding of the transformer is connected with the first end of the current detection circuit, the current detection pin of the control circuit and the first end of the absorption circuit, the lower end of the primary winding of the transformer is connected with the output negative end of the EMI filter circuit, the second end of the feedback circuit and the second end of the absorption circuit, and the upper end and the lower end of the secondary winding of the transformer are respectively connected with the two input ends of the output rectifying filter circuit.
12. The flyback power supply circuit of claim 7, wherein the control circuit is an OB2514X control chip.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201920227478.6U CN210380686U (en) | 2019-02-20 | 2019-02-20 | Flyback power supply circuit |
| TW108204082U TWM584065U (en) | 2019-02-20 | 2019-04-02 | Flyback power circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201920227478.6U CN210380686U (en) | 2019-02-20 | 2019-02-20 | Flyback power supply circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN210380686U true CN210380686U (en) | 2020-04-21 |
Family
ID=68620092
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201920227478.6U Active CN210380686U (en) | 2019-02-20 | 2019-02-20 | Flyback power supply circuit |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN210380686U (en) |
| TW (1) | TWM584065U (en) |
-
2019
- 2019-02-20 CN CN201920227478.6U patent/CN210380686U/en active Active
- 2019-04-02 TW TW108204082U patent/TWM584065U/en unknown
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| Publication number | Publication date |
|---|---|
| TWM584065U (en) | 2019-09-21 |
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