CN216215853U - Overvoltage protection circuit - Google Patents
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- CN216215853U CN216215853U CN202122324580.8U CN202122324580U CN216215853U CN 216215853 U CN216215853 U CN 216215853U CN 202122324580 U CN202122324580 U CN 202122324580U CN 216215853 U CN216215853 U CN 216215853U
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Abstract
The embodiment of the utility model relates to the technical field of electronic circuits, in particular to an overvoltage protection circuit. An embodiment of the present invention provides an overvoltage protection circuit, including: the device comprises a transformer, a power management unit, a first overvoltage protection unit and a second overvoltage protection unit; in the circuit, when the voltage at the input end of the transformer is overvoltage, the first overvoltage protection unit generates a voltage signal to pull down the starting voltage of the power management unit so as to turn off the power management unit, when the first output end of the transformer is overvoltage, the second overvoltage protection unit generates a feedback signal, the power management unit is turned off after receiving the feedback signal, and therefore the transformer has the functions of input voltage overvoltage protection and output voltage overvoltage protection by arranging the first overvoltage protection unit at the input end of the transformer and arranging the second overvoltage protection unit at the first output end.
Description
Technical Field
The embodiment of the utility model relates to the technical field of electronic circuits, in particular to an overvoltage protection circuit.
Background
A flyback transformer, which is also called a single-ended flyback or "Buck-Boost" converter, is usually provided in the flyback circuit. The power source is connected with the primary winding and the output end of the primary winding. The flyback converter is very popular with development engineers due to the simple circuit structure and low cost.
However, in the existing transformer, due to the fluctuation of the power grid voltage, especially when the power grid voltage has sudden overvoltage and the voltage exceeds the insulation strength and the voltage withstanding value of the electric appliance, the electric appliance is broken down, burned and even ignited.
SUMMERY OF THE UTILITY MODEL
The technical problem mainly solved by the embodiment of the utility model is to provide an overvoltage protection circuit which can cut off a power supply in time when the voltage is too large, so that electrical equipment is effectively protected.
The embodiment of the utility model adopts a technical scheme that: there is provided an overvoltage protection circuit comprising: the device comprises a transformer, a power management unit, a first overvoltage protection unit and a second overvoltage protection unit; the first overvoltage protection unit is connected with the input end of the transformer and the power management unit respectively, and is used for generating a voltage signal to the power management unit according to the voltage of the input end of the transformer so as to switch off the power management unit; the second overvoltage protection unit is connected with the first output end of the transformer and the power management unit respectively, and the second overvoltage protection unit is used for generating a feedback signal to the power management unit according to the voltage of the first output end of the transformer so as to switch off the power management unit.
In some embodiments, the first overvoltage protection unit includes a first voltage division module, a second voltage division module, and a first switch module; the first end of the first voltage division module is connected with the input end of the transformer and used for generating a first driving signal according to the voltage of the input end of the transformer so as to drive the first switch module to be closed; the second end of the first voltage division module is connected with the first end of the second voltage division module through the first switch module, the second end of the second voltage division module is connected with the power management unit, and the second voltage division module generates the voltage signal according to the closing state of the first switch module.
In some embodiments, the second overvoltage protection unit includes a third voltage division module, a fourth voltage division module, and a second switch module; the first end of the third voltage division module is connected with the first output end of the transformer and used for generating a second driving signal according to the voltage of the first output end of the transformer so as to drive the second switch module to be closed; the second end of the third voltage division module is connected with the first end of the fourth voltage division module through the second switch module, the second end of the fourth voltage division module is connected with the power management unit, and the fourth voltage division module generates the feedback signal according to the closing state of the second switch module.
In some embodiments, the first voltage-dividing module comprises a first voltage-dividing resistor, a second voltage-dividing resistor, and a third voltage-dividing resistor; a first end of the first voltage-dividing resistor is connected to the input end of the transformer, a second end of the first voltage-dividing resistor is connected to a first end of the second voltage-dividing resistor, a second end of the second voltage-dividing resistor is respectively connected to a first end of the third voltage-dividing resistor and the first switch module, and a second end of the third voltage-dividing resistor is grounded.
In some embodiments, the first switching module comprises a first controllable precision regulator; the reference end of the first controllable precise voltage-stabilizing source is connected with the second end of the first voltage-dividing module, the cathode of the first controllable precise voltage-stabilizing source is connected with the first end of the second voltage-dividing module, and the anode of the first controllable precise voltage-stabilizing source is grounded.
In some embodiments, the second voltage divider module comprises a fourth voltage divider resistor and a fifth voltage divider resistor; the first end of the fourth voltage-dividing resistor is connected with the first switch module, the second end of the fourth voltage-dividing resistor is respectively connected with the power supply end of the power supply management unit and the first end of the fifth voltage-dividing resistor, and the second end of the fifth voltage-dividing resistor is connected with the second output end of the transformer.
In some embodiments, the third voltage division module includes a sixth voltage division resistor and a seventh voltage division resistor; the first end of the sixth voltage-dividing resistor is connected with the first output end of the transformer, the second end of the sixth voltage-dividing resistor is respectively connected with the second switch module and the first end of the seventh voltage-dividing resistor, and the second end of the seventh voltage-dividing resistor is grounded.
In some embodiments, the second switching module comprises a second controllable precision regulator; the reference end of the second controllable precise voltage-stabilizing source is connected with the second end of the third voltage-dividing module, the cathode of the second controllable precise voltage-stabilizing source is connected with the first end of the fourth voltage-dividing module, and the anode of the second controllable precise voltage-stabilizing source is grounded.
In some embodiments, the fourth voltage division module comprises an eighth voltage division resistor, a ninth voltage division resistor and an optical coupling isolation unit; the first end of the eighth voltage-dividing resistor is connected with the first output end of the transformer, the second end of the eighth voltage-dividing resistor is respectively connected with the first end of the primary side of the optical coupling isolation unit and the first end of the ninth voltage-dividing resistor, the second end of the ninth voltage-dividing resistor is respectively connected with the second end of the primary side of the optical coupling isolation unit and the second switch module, the first end of the secondary side of the optical coupling isolation unit is connected with the feedback end of the power management unit, and the second end of the secondary side of the optical coupling isolation unit is grounded.
In some embodiments, the overvoltage protection circuit further comprises a first spike absorption unit; the first end of the first peak absorption unit is connected with the input end of the transformer, and the second end of the first peak absorption unit is connected with the input end of the power management unit.
The beneficial effects of the embodiment of the utility model are as follows: in contrast to the prior art, an embodiment of the present invention provides an overvoltage protection circuit, including: the device comprises a transformer, a power management unit, a first overvoltage protection unit and a second overvoltage protection unit; the first overvoltage protection unit is respectively connected with the input end of the transformer and the power management unit, and is used for generating a voltage signal to the power management unit according to the voltage of the input end of the transformer so as to switch off the power management unit; the second overvoltage protection unit is connected with the first output end of the transformer and the power management unit respectively, and the second overvoltage protection unit is used for generating a feedback signal to the power management unit according to the voltage of the first output end of the transformer so as to turn off the power management unit. In the circuit, when the voltage at the input end of the transformer is overvoltage, the first overvoltage protection unit generates a voltage signal, wherein the voltage signal is lower than the starting voltage of the power management unit, namely, the voltage signal cannot enable the power management unit to work, and then the power management unit is turned off; when the first output end of the transformer is in overvoltage, the second overvoltage protection unit generates a feedback signal, and the power management unit is turned off after receiving the feedback signal. That is, in the embodiment of the present invention, the overvoltage protection units are disposed at both the input end and the output end of the transformer, so that the voltage conditions of the input end and the output end of the transformer can be detected simultaneously, and the power management unit can be turned off in time to cut off the power supply when the input end and/or the output end is/are in overvoltage, thereby effectively protecting the electrical equipment.
Drawings
One or more embodiments are illustrated by the accompanying figures in the drawings that correspond thereto and are not to be construed as limiting the embodiments, wherein elements/modules and steps having the same reference numerals are represented by like elements/modules and steps, unless otherwise specified, and the drawings are not to scale.
Fig. 1 is a schematic structural block diagram of an overvoltage protection circuit according to an embodiment of the present invention;
FIG. 2 is a block diagram of another embodiment of an overvoltage protection circuit according to the present invention;
fig. 3 is a schematic circuit diagram of an overvoltage protection circuit according to an embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the utility model, but are not intended to limit the utility model in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the utility model. All falling within the scope of the present invention.
In order to facilitate an understanding of the present application, the present application is described in more detail below with reference to the accompanying drawings and specific embodiments. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It should be noted that, if not conflicted, the various features of the embodiments of the utility model may be combined with each other within the scope of protection of the present application. In addition, although the functional blocks are divided in the device diagram, in some cases, the blocks may be divided differently from those in the device. Further, the terms "first," "second," and the like, as used herein, do not limit the data and the execution order, but merely distinguish the same items or similar items having substantially the same functions and actions.
In a first aspect, an embodiment of the utility model provides an overvoltage protection circuit, referring to fig. 1, the overvoltage protection circuit 100 includes: the transformer 10, the power management unit 20, the first overvoltage protection unit 30 and the second overvoltage protection unit 40.
The first overvoltage protection unit 30 is connected to the input terminal of the transformer 10 and the power management unit 20, and the first overvoltage protection unit 30 is configured to generate a voltage signal to the power management unit 20 according to a voltage at the input terminal of the transformer 10 to turn off the power management unit 20; the second overvoltage protection unit 40 is connected to the first output terminal of the transformer 10 and the power management unit 20, and the second overvoltage protection unit 40 is configured to generate a feedback signal to the power management unit 20 according to the voltage at the first output terminal of the transformer 10, so as to turn off the power management unit 20.
In the overvoltage protection circuit, when the voltage at the input end of the transformer 10 is overvoltage, the first overvoltage protection unit 30 generates a voltage signal, wherein the voltage signal is lower than the enabling voltage of the power management unit 20, that is, the voltage signal cannot enable the power management unit 20 to work, so as to turn off the power management unit 20; when the first output terminal of the transformer 10 is over-voltage, the second over-voltage protection unit 40 will generate a feedback signal, and the power management unit 20 is turned off after receiving the feedback signal. That is, in the embodiment of the present invention, the overvoltage protection units are disposed at both the input end and the output end of the transformer, so that the voltage conditions of the input end and the output end of the transformer can be detected simultaneously, and the power management unit can be turned off in time to cut off the power supply when the input end and/or the output end is/are in overvoltage, thereby effectively protecting the electrical equipment.
In some embodiments, referring to fig. 2, the first overvoltage protection unit 30 includes a first voltage dividing module 31, a second voltage dividing module 32, and a first switch module 33; a first end of the first voltage division module 31 is connected with the input end of the transformer 10, and is used for generating a first driving signal according to the voltage of the input end of the transformer 10 to drive the first switch module 33 to close; the second end of the first voltage division module 31 is connected with the first end of the second voltage division module 32 through the first switch module 33, the second end of the second voltage division module 32 is connected with the power management unit 20, and the second voltage division module 32 generates a voltage signal according to the closed state of the first switch module 33.
Specifically, the primary side of the transformer has a primary winding 11 and an auxiliary winding 12, a first end of the primary winding 11 is connected to a first end of the first voltage division module 31, the first end of the primary winding 11 is further used for connecting an external power supply 200, and a second end of the primary winding 11 is connected to an output end of the power management unit 20; the first end of the auxiliary winding 12 is connected to the power end of the power management unit 20 and the first end of the second voltage division module 32, respectively, the second end of the auxiliary winding 12 is grounded, and the auxiliary winding 12 is used for supplying power to the power management unit 20.
The power management unit 20 is generally a power chip with a built-in MOS transistor, such as a PN8175 chip, or any other suitable ac/dc conversion chip that is applicable to a transformer and has a built-in self-powered module. Generally, the input terminal of the power management unit 20 is a drain pin of a high voltage MOS transistor of the power chip, so that after the power management unit 20 receives power supply, the transformer can be controlled to operate by controlling the on/off of the MOS transistor. It can be understood that the power management unit may also be a power chip without a built-in MOS transistor, and at this time, only one MOS transistor needs to be built between the second end of the primary winding and the input end of the power management unit, and the circuit structure of the power management unit refers to a circuit structure in the prior art, which is not limited herein.
Specifically, in the overvoltage protection circuit, when the primary winding 11 is connected to the external power supply 200, the external power supply may be 220V, and the auxiliary winding 12 provides voltage to the power management unit 20, so that the power management unit 20 may operate to control the operation of the transformer by controlling the on/off of the built-in MOS transistor.
Then, if the input voltage input to the primary winding 11 by the external power supply 200 exceeds the first voltage threshold, the first voltage division module 31 generates a first driving signal to the first switch module 33, and the first switch module 33 is turned on according to the first driving signal, so that the second voltage division module 32 generates a voltage signal according to the turned-on state of the first switch module 33, and pulls down the supply voltage of the power management unit 20, so that the supply voltage is lower than the turn-off voltage of the power management unit 20, and the power management unit 20 is disabled when power is lost, thereby performing the function of overvoltage protection of the input voltage.
In some embodiments, referring to fig. 3, the first voltage dividing module 31 includes a first voltage dividing resistor Rf1, a second voltage dividing resistor Rf2 and a third voltage dividing resistor Rf 3; a first end of the first voltage-dividing resistor Rf1 is connected to the input end of the transformer 10, a second end of the first voltage-dividing resistor Rf1 is connected to a first end of the second voltage-dividing resistor Rf2, a second end of the second voltage-dividing resistor Rf2 is connected to a first end of the third voltage-dividing resistor Rf3 and the first switch module 33, respectively, and a second end of the third voltage-dividing resistor Rf3 is grounded. In practical applications, the number and the resistance of the voltage dividing resistors of the first voltage dividing module can be set according to actual needs, and the limitation in this embodiment is not required.
In some embodiments, referring to fig. 3, the second voltage dividing module 32 includes a fourth voltage dividing resistor Rf4 and a fifth voltage dividing resistor Rf 5; a first terminal of the fourth voltage-dividing resistor Rf4 is connected to the first switch module 31, a second terminal of the fourth voltage-dividing resistor Rf4 is connected to the power source terminal of the power management unit 20 and a first terminal of the fifth voltage-dividing resistor Rf5, and a second terminal of the fifth voltage-dividing resistor Rf5 is connected to the second output terminal of the transformer. In practical applications, the number and the resistance of the voltage dividing resistors of the second voltage dividing module can be set according to actual needs, and the limitation in this embodiment is not required.
In some embodiments, referring to fig. 3, the second voltage dividing module further includes a first filter capacitor C1, and the first filter capacitor C1 is connected in parallel with the third voltage dividing resistor Rf 3. The first filter capacitor C1 can filter the voltage signal collected by the second voltage division module 32, so that the circuit operates stably.
In some embodiments, with continued reference to fig. 3, the first switch module 33 includes a first controllable precision voltage regulator U1; the reference end of the first controllable precise voltage-stabilizing source U1 is connected with the second end of the first voltage-dividing module 31, the cathode of the first controllable precise voltage-stabilizing source U1 is connected with the first end of the second voltage-dividing module 32, and the anode of the first controllable precise voltage-stabilizing source U1 is grounded.
The first controllable precision voltage regulator U1 may be a TL431 chip, a TL432 chip, or any other suitable controllable precision voltage regulator, and the process of setting the first voltage threshold is explained below with the TL431 chip as the first controllable precision voltage regulator U1. At this time, referring to fig. 3, a first end of the first voltage-dividing resistor Rf1 is connected to a first end of the primary winding 11, a second end of the fifth voltage-dividing resistor Rf5 is connected to a first end of the auxiliary winding 12 of the transformer, a reference end of the first TL431 chip U1 is connected to a first end of the third voltage-dividing resistor Rf3, and since the TL431 chip will conduct an anode and a cathode of the TL431 chip when the reference end exceeds 2.5V, the first TL431 chip U1 will conduct a connection between the auxiliary winding 12 and ground when the reference end exceeds 2.5V, so that when the first TL431 chip U1 is triggered and conducted, the first end of the auxiliary winding, the fifth voltage-dividing resistor, the fourth voltage-dividing resistor, the first controllable precision voltage-stabilizing source, and a discharge loop are formed, and the magnitude of the supply voltage output from the auxiliary winding to the power management unit is reduced, so that the power management unit is de-powered. It can be seen that the input voltage overvoltage protection is triggered when the voltage of the first terminal of the third voltage dividing resistor Rf3 exceeds 2.5V, and then the first voltage threshold can be set according to the voltage of the first terminal of the third voltage dividing resistor Rf3 being 2.5V, the resistance values of the first voltage dividing resistor, the second voltage dividing resistor and the third voltage dividing resistor. Then, the controllable precise voltage-stabilizing source is arranged as the first switch module, the first voltage threshold value can be precisely set, and when the input voltage exceeds the first voltage threshold value, the voltage of the reference end of the controllable precise voltage-stabilizing source exceeds the threshold value, so that the input voltage overvoltage protection is precisely triggered.
In some embodiments, with continued reference to fig. 3, the overvoltage protection circuit 100 further includes a first rectifying diode D1 and a second smoothing capacitor C2, an anode of the first rectifying diode D1 is connected to the first end of the auxiliary winding 12, a cathode of the first rectifying diode D1 is connected to the second end of the fifth voltage-dividing resistor Rf5, a second smoothing capacitor C2 is connected in series between a cathode of the first rectifying diode D1 and ground, and the first rectifying diode D1 and the second smoothing capacitor C2 together form a half-wave smoothing circuit, so that the auxiliary winding 12 can provide operating power for the power management unit 20.
In some embodiments, referring to fig. 2, the second overvoltage protection unit 40 includes a third voltage dividing module 41, a fourth voltage dividing module 42 and a second switch module 43; a first end of the third voltage division module 41 is connected to the first output end of the transformer 10, and is configured to generate a second driving signal according to a voltage at the first output end of the transformer 10 to drive the second switch module 43 to be closed; a second end of the third voltage dividing module 41 is connected to a first end of the fourth voltage dividing module 42 through a second switch module 43, a second end of the fourth voltage dividing module 42 is connected to the power management unit 20, and the fourth voltage dividing module 42 generates a feedback signal according to a closed state of the second switch module 43.
Specifically, the secondary side of the transformer has a secondary winding 13, a first end of the secondary winding 13 is connected to a first end of the third voltage division module 41, and a second end of the secondary winding 13 is grounded. In the overvoltage protection circuit, when the output voltage of the secondary winding 13 exceeds the second voltage threshold, the third voltage dividing module 41 outputs a second driving signal to the second switching module 43, the second switching module 43 is closed according to the second driving signal, so that the fourth voltage dividing module generates a feedback signal, and after the feedback end of the power management unit 20 receives the feedback signal, the built-in MOS transistor is controlled to be turned on, so that the primary winding 11 is controlled to stop supplying energy to the secondary winding 13, and the output voltage overvoltage protection function is realized.
In some embodiments, referring to fig. 3, the third voltage dividing module 41 includes a sixth voltage dividing resistor Rf6 and a seventh voltage dividing resistor Rf 7; a first end of the sixth voltage-dividing resistor Rf6 is connected to the first output end of the transformer 10, a second end of the sixth voltage-dividing resistor Rf6 is connected to the first ends of the second switch module 43 and the seventh voltage-dividing resistor Rf7, and a second end of the seventh voltage-dividing resistor Rf7 is grounded. Specifically, the first ends of the fourth voltage dividing resistors Rf4 are respectively connected to the first ends of the secondary windings 13. In practical application, the number and the resistance of the voltage dividing resistors of the third voltage dividing module can be set according to actual needs, and are not limited herein.
In some embodiments, please refer to fig. 3, the fourth voltage dividing module 42 includes an eighth voltage dividing resistor Rf8, a ninth voltage dividing resistor Rf9 and an optical coupling isolation unit U3; the first end of the eighth voltage-dividing resistor Rf8 is connected to the first output end of the transformer 10, the second end of the eighth voltage-dividing resistor Rf8 is connected to the first end of the primary side of the opto-isolation unit U3 and the first end of the ninth voltage-dividing resistor Rf9, the second end of the ninth voltage-dividing resistor Rf9 is connected to the second end of the primary side of the opto-isolation unit U3 and the second switch module 43, the first end of the secondary side of the opto-isolation unit U3 is connected to the feedback end of the power management unit 20, and the second end of the secondary side of the opto-isolation unit U3 is grounded.
Similarly, in order to accurately trigger the output voltage over-voltage protection when the output voltage exceeds the second voltage threshold, in some embodiments, referring to fig. 3, the second switch module 43 includes a second controllable precision regulator U2; the reference end of a second controllable precise voltage-stabilizing source U2 is connected with the second end of the third voltage-dividing module 41, the cathode of the second controllable precise voltage-stabilizing source U2 is connected with the first end of the fourth voltage-dividing module 42, and the anode of the second controllable precise voltage-stabilizing source U2 is grounded. Similarly, the second controllable precision voltage regulator U2 may be TL431, TL432, or any other suitable controllable precision voltage regulator, wherein the setting of the second voltage threshold may refer to the setting of the first voltage threshold, and will not be described herein again.
In some embodiments, the overvoltage protection circuit further includes a third filter capacitor C3, one end of the third filter capacitor C3 is connected to the feedback terminal of the power management unit 20, and the other end of the third filter capacitor C3 is grounded.
In some embodiments, the overvoltage protection circuit further includes a compensation circuit connected in series between the reference terminal of the second controllable precision voltage regulator and the cathode of the second controllable precision voltage regulator, and in particular, referring to fig. 3, the compensation circuit includes a compensation resistor R1 and a compensation capacitor C4 connected in series.
In some embodiments, referring to fig. 3 again, the overvoltage protection circuit 100 further includes an input interface CN1, a fuse F1, a varistor ZNR1, a rectifier bridge BR1, and an input filter capacitor C5, the input interface CN1 is configured to be connected to an external power supply, the fuse F1 is connected in series to a first end of the input interface CN1 and a first input end of the rectifier bridge BR1, a second end of the input interface CN1 is connected to a second input end of the rectifier bridge BR1, the varistor ZNR1 is connected in series to the first input end of the rectifier bridge BR1 and a second input end of the rectifier bridge BR1, a first output end of the rectifier bridge BR1 is connected to the first end of the primary winding 11, a second output end of the rectifier bridge BR1 is connected to ground, and the input filter capacitor C5 is connected in series between the first output end of the rectifier bridge BR1 and the second output end of the rectifier bridge BR 1. The input interface CN1 is used for connecting with an external power supply, and the fuse F1 plays a role in overload protection to prevent a fire caused by a short circuit of a circuit. The piezoresistor ZNR1 can play a role of surge protection together with the fuse F1. For example, when the voltage exceeds the voltage-sensitive voltage, the varistor ZNR1 is short-circuited, resulting in short-circuiting of the fuse F1, so that it is possible to prevent a high voltage from being introduced into the back-end circuit and to avoid circuit damage. The rectifier bridge BR1 can be used for converting the alternating current of external power supply into direct current power supply, and input filter capacitor C5 can be used for filtering out alternating current component, makes the direct current of output to the transformer more smooth.
In some embodiments, the overvoltage protection circuit further includes a first peak absorbing unit, a first end of the first peak absorbing unit is connected to the input end of the transformer, and a second end of the first peak absorbing unit is connected to the input end of the power management unit. Specifically, referring to fig. 3, the first spike absorption circuit includes a first capacitor C6, a first resistor R2, and a diode D2. After being connected in parallel with the first resistor R2, the first capacitor C6 is connected in series between the first end of the primary winding 11 and the cathode of the diode D2, and the anode of the diode D2 is connected to the second end of the primary winding 11. The first peak absorption unit can be used for absorbing peak energy generated by leakage inductance of the transformer.
In some embodiments, referring to fig. 3, the overvoltage protection circuit further includes a second capacitor CY1 and a second rectifying diode D3, the second capacitor CY1 is connected in series between the first end of the primary winding 11 and the first end of the secondary winding 13, and the second rectifying diode D3 is connected in series between the first end of the secondary winding 13 and the first end of the third voltage division module 41. Common mode interference can be eliminated by providing the second capacitor CY 1.
In some embodiments, the overvoltage protection circuit further comprises a second spike absorption unit, wherein the second spike absorption unit is connected in parallel with the second rectifier diode. Specifically, referring to fig. 3, the second peak absorption unit is formed by connecting a third resistor R3 and a third capacitor C7 in series, and the second peak absorption unit can be used for absorbing peak energy generated by leakage inductance of the transformer.
In some embodiments, referring to fig. 3, the overvoltage protection circuit further includes a first output filter capacitor C1, a second output filter capacitor C2, and a fourth resistor R4, wherein the first output filter capacitor C1, the second output filter capacitor C2, and the fourth resistor R4 are respectively connected in series between the cathode of the rectifier diode D3 and the ground.
The operation of the overvoltage protection circuit provided by the utility model is explained in detail below with reference to the embodiment shown in fig. 3. The first controllable precise voltage stabilizing source U1 and the second controllable precise voltage stabilizing source U2 both adopt TL431 chips.
In the overvoltage protection circuit, after the input interface CN1 is connected to an external power supply, ac power of the external power supply is rectified by the rectifier bridge BR1 and then transmitted to the primary winding 11 in the form of dc power, and the auxiliary winding 12 provides voltage to the power management unit 20, so that the power management unit 20 operates, and the operation of the overvoltage protection circuit 100 can be controlled by controlling the on/off of a built-in MOS transistor.
Then, if the input voltage input to the primary winding 11 exceeds the first voltage threshold, the second end voltage of the second voltage-dividing resistor Rf2 will exceed 2.5V, that is, the reference end voltage of the first controllable precise voltage-stabilizing source U1 exceeds 2.5V, so that the anode and the cathode of the first controllable precise voltage-stabilizing source U1 are turned on, then the voltage generated by the auxiliary winding 12 is divided by the first diode D1, the fifth voltage-dividing resistor Rf5, the fourth voltage-dividing resistor Rf4 and the first controllable precise voltage-stabilizing source U1, so that the supply voltage output by the auxiliary winding 12 to the power management unit 20 will be reduced, and by setting the resistance values of the fifth voltage-dividing resistor Rf5 and the fourth voltage-dividing resistor Rf4, the supply voltage can be lower than the off voltage of the power management unit 20, so that the power management unit 20 does not work, and the function of input voltage loss protection is realized.
In addition, if the output voltage of the secondary winding 13 exceeds the second voltage threshold, the voltage of the second end of the sixth voltage-dividing resistor Rf6 will exceed 2.5V, that is, the voltage of the reference end of the second controllable precision voltage-stabilizing source U2 exceeds 2.5V, so that the anode and the cathode of the second controllable precision voltage-stabilizing source U2 are turned on, then the primary diode of the optical coupling isolation unit U3 is turned on, so that the secondary side of the optical coupling isolation unit U3 is turned on, the feedback end of the power management unit 20 is pulled down, and after the feedback end of the power management unit 20 detects a low level signal, the built-in MOS transistor is turned on, so as to control the primary winding 11 to stop providing energy to the secondary winding 13, and store the energy in the primary winding 11, thereby playing a role of output voltage overvoltage protection.
In the overvoltage protection circuit 100, the first overvoltage protection unit 30 is arranged on the primary side of the transformer, and the second overvoltage protection unit 40 is arranged on the secondary side of the transformer, so that the transformer has both the input voltage overvoltage protection function and the output voltage overvoltage protection function, and the safety and reliability of the transformer are improved. And the voltage is sampled and detected through the resistor voltage dividing circuit, and then trigger protection is performed through the controllable precise voltage stabilizing source, so that the protection precision is high.
An embodiment of the present invention provides an overvoltage protection circuit, including: the device comprises a transformer, a power management unit, a first overvoltage protection unit and a second overvoltage protection unit; the first overvoltage protection unit is respectively connected with the input end of the transformer and the power management unit, and is used for generating a voltage signal to the power management unit according to the voltage of the input end of the transformer so as to switch off the power management unit; the second overvoltage protection unit is connected with the first output end of the transformer and the power management unit respectively, and the second overvoltage protection unit is used for generating a feedback signal to the power management unit according to the voltage of the first output end of the transformer so as to turn off the power management unit. In the circuit, when the voltage at the input end of the transformer is overvoltage, the first overvoltage protection unit generates a voltage signal to pull down the voltage of the power management unit so as to turn off the power management unit, when the first output end of the transformer is overvoltage, the second overvoltage protection unit generates a feedback signal, the power management unit is turned off after receiving the feedback signal, and therefore the transformer has the functions of input voltage overvoltage protection and output voltage overvoltage protection by arranging the first overvoltage protection unit at the input end of the transformer and arranging the second overvoltage protection unit at the first output end.
It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; within the idea of the utility model, also technical features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the utility model as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. An overvoltage protection circuit, comprising: the device comprises a transformer, a power management unit, a first overvoltage protection unit and a second overvoltage protection unit;
the first overvoltage protection unit is connected with the input end of the transformer and the power management unit respectively, and is used for generating a voltage signal to the power management unit according to the voltage of the input end of the transformer so as to switch off the power management unit;
the second overvoltage protection unit is connected with the first output end of the transformer and the power management unit respectively, and the second overvoltage protection unit is used for generating a feedback signal to the power management unit according to the voltage of the first output end of the transformer so as to switch off the power management unit.
2. The overvoltage protection circuit according to claim 1, wherein the first overvoltage protection unit comprises a first voltage division module, a second voltage division module and a first switch module;
the first end of the first voltage division module is connected with the input end of the transformer and used for generating a first driving signal according to the voltage of the input end of the transformer so as to drive the first switch module to be closed;
the second end of the first voltage division module is connected with the first end of the second voltage division module through the first switch module, the second end of the second voltage division module is connected with the power management unit, and the second voltage division module generates the voltage signal according to the closing state of the first switch module.
3. The overvoltage protection circuit according to claim 1, wherein the second overvoltage protection unit comprises a third voltage division module, a fourth voltage division module and a second switch module;
the first end of the third voltage division module is connected with the first output end of the transformer and used for generating a second driving signal according to the voltage of the first output end of the transformer so as to drive the second switch module to be closed;
the second end of the third voltage division module is connected with the first end of the fourth voltage division module through the second switch module, the second end of the fourth voltage division module is connected with the power management unit, and the fourth voltage division module generates the feedback signal according to the closing state of the second switch module.
4. The overvoltage protection circuit of claim 2, wherein the first voltage-dividing module comprises a first voltage-dividing resistor, a second voltage-dividing resistor, and a third voltage-dividing resistor;
a first end of the first voltage-dividing resistor is connected to the input end of the transformer, a second end of the first voltage-dividing resistor is connected to a first end of the second voltage-dividing resistor, a second end of the second voltage-dividing resistor is respectively connected to a first end of the third voltage-dividing resistor and the first switch module, and a second end of the third voltage-dividing resistor is grounded.
5. The overvoltage protection circuit of claim 2, wherein the first switch module includes a first controllable precision voltage regulator;
the reference end of the first controllable precise voltage-stabilizing source is connected with the second end of the first voltage-dividing module, the cathode of the first controllable precise voltage-stabilizing source is connected with the first end of the second voltage-dividing module, and the anode of the first controllable precise voltage-stabilizing source is grounded.
6. The overvoltage protection circuit of claim 2, wherein the second voltage divider module comprises a fourth voltage divider resistor and a fifth voltage divider resistor;
the first end of the fourth voltage-dividing resistor is connected with the first switch module, the second end of the fourth voltage-dividing resistor is respectively connected with the power supply end of the power supply management unit and the first end of the fifth voltage-dividing resistor, and the second end of the fifth voltage-dividing resistor is connected with the second output end of the transformer.
7. The overvoltage protection circuit of claim 3, wherein the third voltage-dividing module comprises a sixth voltage-dividing resistor and a seventh voltage-dividing resistor;
the first end of the sixth voltage-dividing resistor is connected with the first output end of the transformer, the second end of the sixth voltage-dividing resistor is respectively connected with the second switch module and the first end of the seventh voltage-dividing resistor, and the second end of the seventh voltage-dividing resistor is grounded.
8. The overvoltage protection circuit of claim 3, wherein the second switch module includes a second controllable precision voltage regulator;
the reference end of the second controllable precise voltage-stabilizing source is connected with the second end of the third voltage-dividing module, the cathode of the second controllable precise voltage-stabilizing source is connected with the first end of the fourth voltage-dividing module, and the anode of the second controllable precise voltage-stabilizing source is grounded.
9. The overvoltage protection circuit of claim 3, wherein the fourth voltage division module comprises an eighth voltage division resistor, a ninth voltage division resistor, and an opto-coupler isolation unit;
the first end of the eighth voltage-dividing resistor is connected with the first output end of the transformer, the second end of the eighth voltage-dividing resistor is respectively connected with the first end of the primary side of the optical coupling isolation unit and the first end of the ninth voltage-dividing resistor, the second end of the ninth voltage-dividing resistor is respectively connected with the second end of the primary side of the optical coupling isolation unit and the second switch module, the first end of the secondary side of the optical coupling isolation unit is connected with the feedback end of the power management unit, and the second end of the secondary side of the optical coupling isolation unit is grounded.
10. The overvoltage protection circuit according to any one of claims 1-9, further comprising a first spike absorption unit;
the first end of the first peak absorption unit is connected with the input end of the transformer, and the second end of the first peak absorption unit is connected with the input end of the power management unit.
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| CN202122324580.8U CN216215853U (en) | 2021-09-23 | 2021-09-23 | Overvoltage protection circuit |
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| CN202122324580.8U CN216215853U (en) | 2021-09-23 | 2021-09-23 | Overvoltage protection circuit |
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