Protection circuit, power adapter and protection control method

Abstract

The application discloses a protection circuit, a power adapter and a protection control method. A first input end of the protection circuit is connected to a control end of a rectifier switch tube to obtain a driving signal of the rectifier switch tube to determine a conduction time of the rectifier switch tube, a second input end is connected to a first polarity end of the rectifier switch tube to obtain a drain-source voltage signal of the rectifier switch tube in the conduction time, and the protection circuit receives a sampling voltage signal representing output current information. The drain-source voltage signal is compared with the sampling voltage signal to obtain a comparison result, and according to the comparison result, the protection circuit generates a protection control signal to control the output current of the power adapter. The protection circuit can meet the requirements of a limited power source in the case of short circuit of a sampling resistor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic circuit, more particularly, to a protection circuit, a power adapter and a control method of the protection circuit. BACKGROUND

[0002] A power adapter is a power supply conversion device for small portable electronic devices and electronic appliances, which is used to convert an AC input signal into a DC output voltage. According to the connection method, the power adapter can be divided into a wall plug-in power adapter and a desktop power adapter. The power adapter has been widely matched with intelligent mobile phones, tablet computers, security cameras, set-top boxes, routers and other devices.

[0003] The power adapter usually needs to meet the limited power supply (LPS) requirement to meet the safety requirement. Generally, two ways are adopted to meet the LPS requirement. One is to use an inherent limited power supply, and the output current thereof should not be greater than 8A. The other is to use a non-inherent limited power supply, and the output current thereof should be less than 5A.

[0004] At present, the industry usually adopts a primary side control chip to realize the current limiting of the power adapter. Figure 1 A schematic diagram of a conventional power adapter is shown. As shown in Figure 1 The power adapter 100 includes a primary side power circuit 110, a flyback switching transformer T1, a secondary side power circuit 120 and a primary side control chip 111. The primary side power circuit 110 receives an AC input signal, rectifies the AC input signal to obtain a DC signal, and sends the DC signal to the flyback switching transformer T1. The flyback switching transformer T1 performs voltage conversion processing on the DC signal, and sends the DC signal after voltage reduction to the secondary side power circuit 120. The secondary side power circuit 120 provides a DC output voltage according to the DC signal. After the primary side power circuit 110 obtains the DC signal, the primary side control chip 111 also performs current limiting processing on the DC signal. However, the above-mentioned current limiting method through the primary side control chip is difficult to adapt to the current limiting requirement of the output current, especially when the secondary side circuit is short-circuited, the current limiting requirement cannot be met.

[0005] Therefore, it is desirable to provide an improved protection circuit to effectively meet the current limiting requirement. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a protection circuit, a power adapter and a control method, so as to meet the current limiting requirement when the sampling circuit is short-circuited.

[0007] According to a first aspect of the present application, there is provided a protection circuit of a power adapter, the power adapter being configured to receive an input voltage and generate an output voltage, the power adapter comprising a rectifier switch tube configured to perform a switching action according to a driving signal to obtain the output voltage, the protection circuit having a first input connected to a control terminal of the rectifier switch tube to obtain the driving signal of the rectifier switch tube to determine a conduction time of the rectifier switch tube, and a second input connected to a first polarity terminal of the rectifier switch tube to obtain a drain-source voltage signal of the rectifier switch tube during the conduction time; the protection circuit being configured to receive a sampling voltage signal representing output current information, wherein the drain-source voltage signal is compared with the sampling voltage signal to obtain a comparison result, and the protection circuit is configured to generate a protection control signal to control an output current of the power adapter according to the comparison result.

[0008] Optionally, the protection circuit further comprises a sampling resistor connected between an output terminal of the power adapter and a reference ground, the output terminal being configured to provide the output voltage, and the protection circuit further comprises a third input and a fourth input connected to two ends of the sampling resistor, respectively, to sample the sampling resistor to obtain the sampling voltage signal.

[0009] Optionally, the protection circuit is configured to generate the protection control signal when a ratio of the drain-source voltage signal to a conduction resistance of the rectifier switch tube is not equal to a ratio of the sampling voltage signal to a resistance of the sampling resistor.

[0010] Optionally, when the rectifier switch tube is detected to be connected to a low-voltage side of the output of the power adapter, the protection circuit comprises a first switch tube having a control terminal connected to the control terminal of the rectifier switch tube to receive the driving signal, and a first end connected to the first polarity terminal of the rectifier switch tube to receive the drain-source voltage signal during the conduction time, and a first filter circuit connected to a second polarity terminal of the first switch tube to provide an average voltage of the drain-source voltage signal.

[0011] Optionally, when the rectifier switch tube is detected to be connected to a high-voltage side of the output of the power adapter, the protection circuit comprises a voltage acquisition circuit having a first input connected to the first polarity terminal of the rectifier switch tube and a second input connected to a second polarity terminal of the rectifier switch tube to acquire the drain-source voltage signal, a second switch tube having a control terminal connected to the control terminal of the rectifier switch tube to receive the driving signal, and a first polarity terminal connected to an output terminal of the voltage acquisition circuit to acquire the drain-source voltage signal during the conduction time, and a second filter circuit connected to a second polarity terminal of the second switch tube to provide an average voltage of the drain-source voltage signal.

[0012] According to a second aspect of the present application, a power adapter is provided, comprising a protocol chip, and a protection circuit as described above integrated in the protocol chip to generate a protection control signal to control output current of the power adapter.

[0013] According to a third aspect of the present application, a protection control method is provided for protecting a power adapter comprising a rectifier switch tube and a sampling resistor, characterized in that the control method comprises: obtaining the drive signal of the rectifier switch tube to determine the on-time of the rectifier switch tube; obtaining the drain-source voltage signal of the rectifier switch tube in the on-time; receiving a sampling voltage signal representing output current information; comparing the relationship between the drain-source voltage signal and the sampling voltage signal to obtain a comparison result; and generating a protection control signal to control the output current according to the comparison result.

[0014] Optionally, when the ratio of the drain-source voltage signal to the on-resistance of the rectifier switch tube is not equal to the ratio of the sampling voltage signal to the resistance of the sampling resistor, the protection circuit generates a protection control signal.

[0015] Optionally, the protection control method further comprises: filtering the drain-source voltage signal of the rectifier switch tube to obtain the average voltage.

[0016] Optionally, the protection control method further comprises: when the protection control signal is valid, the power adapter controls the output of the input-side control signal and / or stops supplying power to the load.

[0017] The protection circuit, power adapter and control method provided by the present application utilize the judgment of the on-time of the rectifier switch tube after receiving the drive voltage, and detect the ratio of the average value of the drain-source voltage signal to the sampling voltage signal in the on-time of the rectifier switch tube to determine whether the sampling resistor is short-circuited, so as to further implement the current limiting of the output voltage. This scheme has simple circuit and low power consumption, can meet the current limiting requirement in the case of short-circuit of the sampling resistor, and can be compatible with multiple specifications of current limiting requirements. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments of the present application, taken in conjunction with the accompanying drawings, in which:

[0019] Figure 1 a schematic diagram of a conventional power adapter is shown;

[0020] Figure 2A schematic diagram of a power adapter according to a first embodiment of the present application is shown;

[0021] Figure 3 and 4 schematic diagrams of protection mechanisms of power adapters according to Figure 2

[0022] Figure 5 A schematic diagram of a power adapter according to a second embodiment of the present application is shown;

[0023] Figure 6 A voltage waveform diagram of a power adapter according to Figure 5

[0024] Figure 7 A schematic diagram of a power adapter according to a third embodiment of the present application is shown;

[0025] Figure 8 A flowchart of a control method of a protection circuit according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0026] The present application will be described in more detail by referring to the attached drawings. Like elements are denoted by like reference numerals throughout the various figures. Individual sections of the drawings have not been drawn to scale for purposes of clarity. Also, some portions of the figures can have been omitted.

[0027] Many specific details of the application are described below in order to provide a thorough understanding of the present application. However, as will be understood by one skilled in the art, the present application can be practiced without incorporating these specific details.

[0028] It should be understood that the connection / coupling between A and B in the embodiments of the present application means that A and B can be connected in series or in parallel, or A and B are connected through other devices, which are not limited in the embodiments of the present application.

[0029] The present disclosure provides a protection circuit of a power adapter for receiving an input voltage and generating an output voltage, the power adapter comprising a rectifier switch tube for switching according to a driving signal to obtain the output voltage, a first input terminal of the protection circuit being connected to a control terminal of the rectifier switch tube to obtain the driving signal of the rectifier switch tube to determine a conduction time of the rectifier switch tube, a second input terminal being connected to a first terminal of the rectifier switch tube to obtain a drain-source voltage signal of the rectifier switch tube in the conduction time, and the protection circuit receiving a sampling voltage signal representing output current information, wherein a comparison between the drain-source voltage signal and the sampling voltage signal is obtained to obtain a comparison result, and the protection circuit generates a protection control signal to control the output current according to the comparison result.​​

[0030] In the embodiments of the present disclosure, the protection circuit of the present disclosure obtains the drain-source voltage signal of the rectifier switch tube in the on period, and judges whether the sampling resistor is short-circuited by combining the sampling voltage provided by the sampling resistor, so as to start the protection mechanism of the protection circuit.

[0031] The protection circuit is used for protecting the power adapter. The power adapter further comprises a secondary coil, for example, for receiving an input voltage and generating an output voltage based on the principle of electromagnetic induction. The rectifier switch tube is selectively connected to the high-voltage side or the low-voltage side of the secondary coil. The first input end of the protection circuit is connected to the control end of the rectifier switch tube, so as to synchronously receive the driving signal output by the synchronous rectifier driver, so as to obtain the on time of the rectifier switch tube. The second input end is connected to the first path end of the rectifier switch tube, so as to obtain the voltage value between the drain and the source of the rectifier switch tube.

[0032] In the embodiments of the present disclosure, a power adapter is also provided. The power adapter comprises the protection circuit and a protocol chip, for example, as described above. The protection circuit is integrated in the protocol chip, so as to generate a protection control signal to control the output current of the power adapter. The type of the power adapter is a power delivery (PD) power adapter, for example, which complies with the PD protocol. The protocol chip contained in the power adapter is a PD protocol chip.

[0033] Based on some configurable embodiments, some alternative embodiments are given below to describe the specific circuit structure of the protection circuit. The embodiments of the protection circuit provided in the present application will be described below with reference to the accompanying drawings.

[0034] Figure 2 A schematic diagram of a power adapter according to the first embodiment of the present application is shown.

[0035] As shown in Figure 2 The power adapter 200 comprises a power adapter and a protection circuit. The power adapter comprises a secondary coil N2 and a rectifier switch tube M1, for realizing voltage conversion, and further comprises a sampling resistor R1, a protection circuit 210, and a synchronous rectifier driver (SR driver) 220, for realizing synchronous rectification and circuit protection. The power adapter 200 is used for converting an input signal Vi into an output voltage Vo, and the output voltage Vo provided by the power adapter 200 meets the current limiting requirement and the power limiting requirement.

[0036] In this embodiment, the high voltage side of the secondary coil N2 provides the output voltage Vo, and the low voltage side is connected to the reference ground. The secondary coil N2 is, for example, in the electromagnetic field generated by the input signal in the primary coil N1, and generates the output voltage Vo based on the principle of electromagnetic induction.

[0037] As an example, the power adapter 200 includes a transformer, and the secondary coil N2 is contained in the transformer. In this embodiment, the transformer includes the primary coil N1 and the secondary coil N2, the primary coil N1 receives the input signal Vi, and the secondary coil N2 generates the output voltage Vo based on the principle of electromagnetic induction. The transformer is, for example, a flyback transformer, and the primary coil N1 and the secondary coil N2 are, for example, oppositely arranged coil windings or oppositely wound coil windings wound on the same core, and the primary coil N1 and the secondary coil N2 can be single coil windings or a plurality of coil windings connected in series, respectively, and it should be understood that the transformer, the primary coil N1 and the secondary coil N2 can be formed in various forms of conventional coil windings, and the specific form, material, etc. of the present application are not limited. Optionally, the primary coil N1 is also connected with the primary power circuit, the primary switch and other components (not shown).

[0038] As another example, the secondary coil N2 is in the electromagnetic field generated by the input signal in the primary coil N1, and generates the output voltage Vo based on the principle of electromagnetic induction, and the primary coil N1 and the secondary coil N2 are respectively located in different two devices, for example, the primary coil N1 is located in a wireless charging device for providing electric energy, and the secondary coil N2 is located in a receiving device for receiving electric energy.

[0039] The rectifier switch tube M1 is connected to the high voltage side and / or the low voltage side of the secondary coil N2, and is used to rectify the output voltage Vo according to the drive signal Vg, which is provided by the synchronous rectifier driver 220, for example. The sampling resistor R1 is connected between the secondary coil N2 and the reference ground. The first end of the protection circuit 210 is connected to the control end of the rectifier switch tube M1 to sample the drive signal Vg, the second end of the protection circuit 210 is connected to the first pass end of the rectifier switch tube M1 to obtain the drain-source voltage signal of the rectifier switch tube, and the third end and the fourth end of the protection circuit 210 are respectively connected to the two ends of the sampling resistor R1 to sample the sampling voltage signal of the sampling resistor R1. When the drive signal Vg is in the active time, i.e. the output high level, and when the protection circuit 210 detects that the ratio of the drain-source voltage signal to the sampling voltage signal is not equal to the ratio of the on-resistance of the rectifier switch tube M1 to the resistance value of the sampling resistor R1, it indicates that the power adapter output is abnormal at this time, and the protection circuit 210 generates a protection control signal to control the output current.

[0040] In this embodiment, the meaning of "the ratio of the drain-source voltage signal to the on-state internal resistance of the rectifier switch tube is not equal to the ratio of the sampling voltage signal to the resistance of the sampling resistor" is that during the on-state period of the rectifier switch tube, if the power adapter 200 operates normally, the average current I flowing from the source to the drain of the rectifier switch tube is ds The sampling current I flowing through the sampling resistor should be sense Equal, that is, I=U / R, so the average drain-source voltage V ds_average The on-state resistance R of the rectifier switch tube ds_on The ratio should be equal to the sampling voltage V sense and the sampling resistor value R sense If the sampling resistor of the power adapter 200 is short-circuited during the conduction period of the rectifier switch tube, the sampling voltage sampled by the protection circuit to the sampling resistor will be very small due to the short circuit, and the ideal value is 0, then the sampling voltage V sense and the sampling resistor value R sense The ratio will be close to 0, and the average drain-source voltage V ds_average The on-state resistance R of the rectifier switch tube ds_on The ratio is still the current value in the loop, so "the ratio of the drain-source voltage signal to the on-state internal resistance of the rectifier switch is not equal to the ratio of the sampling voltage signal to the resistance of the sampling resistor" (V ds_average / R ds_on ≠V sense / R sense ).

[0041] In the embodiment of the present disclosure, when the circuit operates normally, the protection circuit 210 can provide current limiting protection for the power adapter. When a short circuit occurs in the circuit, the protection circuit 210 can execute corresponding protection circuits, such as directly cutting off the output voltage, to protect the circuit from being damaged.

[0042] As an example, the protection circuit 210 has a control terminal (not shown) for providing a control signal. When the protection circuit 210 determines that the sampling resistor R1 is short-circuited, the control terminal provides a valid control signal to the high-voltage side of the secondary winding N2 to control the output voltage Vo, thereby achieving the purpose of protecting the circuit. It should be understood that when the protection circuit 210 determines that the sampling resistor R1 is short-circuited, it can use various other methods to control the current of the output voltage Vo to achieve the purpose of circuit protection. This application does not limit the specific method by which the protection circuit 210 controls the output voltage Vo.

[0043] Optionally, the power adapter 200 further comprises a capacitor C1 connected in parallel between the high-voltage side and the low-voltage side of the secondary coil N2, for supplying power to the load when the freewheeling current in the circuit falls to 0, at which time the rectifier switch tube M1 should be in an off state.

[0044] The above describes some examples of the resonant circuit of the embodiments of the application, however, the embodiments of the application are not limited thereto, and other modes of extension and variation are also possible.

[0045] For example, it should be understood that the reference ground potential in the foregoing embodiments can be replaced by other non-zero reference potentials (having a positive voltage amplitude or a negative voltage amplitude) or a controlled varying reference signal in alternative embodiments.

[0046] For another example, the resistors and capacitors provided by the embodiments of the application can be lumped parameter capacitor elements and resistor elements, or other equivalent elements similar to capacitors and resistors, and the equivalent structures described herein include, but are not limited to, microstrip lines, varactor tubes, and conductor structures having a certain pattern, which can provide inductive impedance and / or capacitive impedance.

[0047] Meanwhile, those skilled in the art can realize the described functions by using different configuration methods or adjustment methods for each structure or reasonable variations of the structure in combination with the structures and methods of the examples described in the embodiments disclosed herein, but such implementation should not be considered beyond the scope of the present application. It should be understood that the connection relationship between the various components of the amplifier of the foregoing figures in the embodiments of the application is only illustrative and does not limit the embodiments of the application in any way.

[0048] Based on an exemplary configuration, Figure 3 and 4 respectively show the schematic diagram of the protection mechanism of the power adapter according to Figure 2 On the basis structure of the power adapter 200 as shown in Figure 2 , Figure 3 and the specific protection circuit for current limiting protection is arranged in the power adapter 200 as shown in Figs. 3 and 4, and the basic structure of the power adapter 200 will not be described again. It should be understood that Figure 3 and Figure 4 The mechanism of the protection circuit for current limiting protection as shown in Figs. 3 and 4 is only illustrative, and in the embodiments of the present disclosure, the specific adjustment mode of the protection circuit in the power adapter to the output current is not limited.

[0049] As Figure 3As shown, the power adapter 200 further comprises a switch tube Q1, the first passage end of the switch tube Q1 is connected to the high voltage side of the secondary side coil N2, the second passage end provides the output end of the power adapter 200, and the control end receives the control signal provided by the protection circuit 210. When the protection circuit 210 determines that the power adapter 200 is in a normal working state, the protection circuit 210 outputs a valid state control signal, so that the first passage end and the second passage end of the switch tube Q1 are in a conduction state to provide an effective output voltage Vo, and the protection circuit 210 performs current limiting protection on the output voltage; when the ratio of the leakage source voltage signal and the sampling voltage signal is not equal to the ratio of the on-resistance of the rectifier switch tube M1 and the resistance value of the sampling resistor R1, that is, when the sampling resistor R1 is detected to be short-circuited, the protection circuit 210 outputs an invalid state control signal, so that the first passage end and the second passage end of the switch tube Q1 are in a cut-off state, thereby suspending the provision of the output current.

[0050] Figure 4 A closed-loop regulation output current mode is shown, for the sake of clarity, the primary side PWM chip and the primary side coil N1 are respectively placed on the two sides of the power adapter 200, and it should be understood that the primary side coil N1 and the primary side PWM chip should be electrically connected in the actual circuit. Figure 4 The optical coupler OCEP is further included, the inside of the optical coupler OCEP includes a light-emitting diode and a photoresistor, the high voltage side of the secondary side coil N2 is connected to the anode of the light-emitting diode through a resistor R0, the OPTO pin of the protection circuit 210 is connected to the cathode of the light-emitting diode as a control pin to send a control signal to the light-emitting diode to adjust the size of the light coupling current of the light-emitting diode, thereby adjusting the conduction state of the photoresistor, one end of the photoresistor is connected to the reference ground, and the other end is connected to the compensation (COMP) pin of the primary side PWM chip. The above-mentioned circuit adjusts the size of the light coupling current through the protection circuit 210, and then adjusts the compensation pin voltage of the primary side PWM chip, thereby realizing closed-loop regulation. When the protection circuit 210 determines that the power adapter 200 is in a normal working state, the protection circuit 210 outputs a valid state control signal, so that the light coupling current is small to provide an effective output voltage Vo; when the protection circuit 210 detects that the ratio of the leakage source voltage signal and the sampling voltage signal is not equal to the ratio of the on-resistance of the rectifier switch tube M1 and the resistance value of the sampling resistor R1, that is, when the sampling resistor R1 is detected to be short-circuited, the protection circuit 210 outputs an invalid state control signal, so that the light coupling current is large, thereby pulling down the compensation pin voltage of the primary side PWM chip, that is, the PWM signal transmission is turned off, thereby effectively limiting the size of the output current, and realizing the requirement of the power limiting source.

[0051] Figure 5A schematic diagram of a power adapter according to a second embodiment of the present application is shown; Figure 6 A voltage waveform diagram of a power adapter according to Figure 5 the first embodiment of the present application is shown.

[0052] As shown in Figure 5 the power adapter 300 includes a secondary coil N3, a rectifier switch M2, a sampling resistor R2, a capacitor C2, a protection circuit 310, and a synchronous rectifier driver 320, which is used to convert an input signal Vi into an output voltage Vo, and the output voltage Vo provided thereby satisfies the current limit requirement and the power limit requirement. Figure 5 The secondary coil N3, the rectifier switch M2, the sampling resistor R2, the protection circuit 310, and the synchronous rectifier driver 320 provided thereby correspond one-to-one to the secondary coil N2, the rectifier switch M1, the sampling resistor R1, the capacitor C1, the protection circuit 210, and the synchronous rectifier driver 220 provided in the power adapter 200, respectively, and have substantially the same functions, and the same parts are not described again here. Figure 2

[0053] In this embodiment, the rectifier switch M2 is connected to the low voltage side of the secondary coil N3, and the power adapter 300 further includes a first switch Q2 and a first filter circuit 3102. As shown in Figure 5 the control terminal of the first switch Q2 receives a driving voltage Vg from the synchronous rectifier driver 320, which is synchronized with the conduction time of the rectifier switch M2, and the first filter circuit 3102 is used to convert the voltage at one end of the first switch Q2 during the conduction period of the first switch Q2 into an average voltage Vds_average. The first end of the protection circuit 310 is connected to the second end of the first switch Q2 via the first filter circuit 3102 to receive the filtered drain-source voltage signal Vds (i.e., the average voltage Vds_average).

[0054] As an example, the first filter circuit 3102 is an RC filter, which includes a resistor R3 and a capacitor C3, the resistor R3 is connected between the first switch Q2 and the first end of the protection circuit 310, and the capacitor C3 is connected between the first end of the protection circuit 310 and the reference ground.

[0055] In this embodiment, the rectifier switch M2 is connected to the low voltage side of the secondary coil N3, as shown in Figure 6 the t1-t4 time is one period of the rectifier switch controlled in the power adapter, V GT is a driving signal output by the synchronous rectifier driver, and V DS ​For the drain-source voltage of the rectifier switch tube, t2-t3 is the on time of the rectifier switch tube. In the time of t2-t3, the ratio of the drain-source voltage signal to the sampling voltage signal is not equal to the ratio of the on resistance of the rectifier switch tube M2 to the resistance value of the sampling resistor R2. The protection circuit 210 determines that the sampling resistor R1 is short-circuited, and generates a protection control signal to control the current of the output voltage Vo, that is, to perform a protection action.

[0056] Figure 7 A schematic diagram of a power adapter according to a third embodiment of the present application is shown.

[0057] As Figure 7 shown, the power adapter 400 includes a secondary side coil N4, a rectifier switch tube M3, a sampling resistor R4, a capacitor C3, a protection circuit 410, a synchronous rectifier driver 420, a voltage acquisition circuit 4101, a second filter circuit 4102, and a second switch tube Q3. The power adapter 400 is used to convert an input signal Vi into an output voltage Vo, and the output voltage Vo provided by the power adapter 400 meets the current limiting requirement and the power source limiting requirement. Figure 7 The secondary side coil N4, the rectifier switch tube M3, the sampling resistor R4, the protection circuit 410, and the synchronous rectifier driver 420 provided in the power adapter 400 are the same as Figure 5 The secondary side coil N3, the rectifier switch tube M2, the sampling resistor R2, the capacitor C2, the protection circuit 310, the synchronous rectifier driver 320, and the rectifier circuit 330 provided in the power adapter 300 are one-to-one corresponding and have the same basic functions. The same parts are not described here. In this embodiment, as Figure 7As shown, the control terminal of the second switch tube Q3 receives the driving voltage Vg of the synchronous rectification driver 420, which is synchronized with the conduction time of the rectification switch tube M3. The second filter circuit 4102 is used to convert the voltage at one end of the second switch tube Q3 during the conduction of the second switch tube Q3 into an average voltage Vds_average. The first end of the protection circuit 410 is connected to the second end of the second switch tube Q3 via the second filter circuit 4102 to receive the filtered drain-source voltage signal Vds (i.e. the average voltage Vds_average). Since it is connected to the high-voltage side, the waveform of the high-voltage side voltage Vds is composed of the winding voltage, and the drain of the rectification switch tube M3 is not grounded, so the voltage acquisition circuit 4101 is needed to acquire the drain-source voltage signal of the rectification switch tube M3. The first input end of the voltage acquisition circuit 4101 is connected to the first passage end of the rectification switch tube M3, the second input end is connected to the second passage end of the rectification switch tube M3, and the output end is connected to the first passage end of the second switch tube Q3, for outputting the obtained drain-source voltage signal. When the ratio of the drain-source voltage signal to the sampling voltage signal is not equal to the ratio of the conduction resistance of the rectification switch tube M3 to the resistance value of the sampling resistor R4, the protection circuit 410 determines that the sampling resistor R4 is short-circuited, and generates a protection control signal to control the current of the output voltage Vo, i.e. to perform a protection action.

[0058] As an example, the second filter circuit 4102 is an RC filter, which includes a resistor R5 and a capacitor C5. The resistor R5 is connected between the second switch tube Q3 and the first end of the protection circuit 410, and the capacitor C5 is connected between the first end of the protection circuit 410 and the reference ground.

[0059] As an example, the voltage acquisition circuit 4101 can be a differential circuit to acquire the drain-source voltage of the rectification switch tube M3.

[0060] In the embodiments shown in Figure 2 , Figure 5 and Figure 7 , the ratio of the drain-source voltage signal to the sampling voltage signal and the ratio of the conduction resistance of the rectification switch tube M3 to the resistance value of the sampling resistor R4 are directly used to determine whether the sampling resistor is short-circuited, so that the power adapter 200 / 300 / 400 can adopt the same protection circuit, and the protection circuit can be used to distinguish and control the power adapter 200 / 300 / 400. Specifically, after receiving the driving voltage Vg, the first end of the protection circuit determines the conduction time of the rectification switch tube, and during the conduction time of the rectification switch tube, the protection circuit detects the ratio of the average value of the drain-source voltage signal to the sampling voltage signal to determine whether the sampling resistor is short-circuited.

[0061] It should be understood that in Figure 5 and Figure 7In the shown embodiment, the protection circuit can use the protection mechanism as shown in Figure 3 and / or 4 to achieve the purpose of circuit protection, or use the traditional protection mechanism to achieve the purpose of circuit protection in the form of current limiting protection. The present application does not limit the specific implementation of the protection circuit to achieve circuit protection.

[0062] Figure 8 A flow chart of a control method of a protection circuit according to an embodiment of the present application is shown. The control method of the protection circuit includes steps S801-S805, and is used to protect a power adapter for receiving an input voltage and generating an output voltage. The protection circuit can be applied to any one of the power adapters or protection circuits as shown in Figure 3 、 Figure 5 and Figure 7 .

[0063] In step S801, a drive signal of a rectifier switch tube is obtained to determine the conduction time of the rectifier switch tube.

[0064] In step S802, a drain-source voltage signal of the rectifier switch tube in the conduction time is obtained.

[0065] In step S803, a sampling voltage signal representing output current information is received.

[0066] In step S804, the relationship between the drain-source voltage signal and the sampling voltage signal is compared to obtain a comparison result.

[0067] In step S805, a protection control signal is generated according to the comparison result to control the output current.

[0068] Optionally, when the ratio of the drain-source voltage signal to the sampling voltage signal is not equal to the ratio of the conduction resistance value of the rectifier switch tube to the resistance value of the sampling resistor, the protection circuit generates the protection control signal.

[0069] Optionally, the drain-source voltage signal of the rectifier switch tube is filtered to obtain an average voltage.

[0070] It is to be understood that the phrases such as first and second, and the like, used herein are merely used to differentiate one from the other and do not imply or require any actual relationship or order between the entities or operations. Also, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0071] In accordance with the practices of the present application, these embodiments have been described in relation to the above-described embodiments, which are intended to be illustrative only and not restrictive of the application. There many modifications and variations to the embodiments described herein that will be apparent to those of ordinary skill in the art. It is therefore contemplated that the application shall not be limited to the particular embodiments described herein, but rather the scope of the present application is to be accorded the broadest possible interpretation so as to encompass all such modifications and equivalent arrangements.

Claims

1. A protection circuit of a power adapter, the power adapter being configured to receive an input voltage and generate an output voltage, the power adapter comprising a rectifier switch tube configured to switch according to a driving signal to obtain the output voltage, characterized in that, a first input of the protection circuit is connected to a control terminal of the rectifier switch tube to obtain the driving signal of the rectifier switch tube to determine a conduction time of the rectifier switch tube, and a second input of the protection circuit is connected to a first polarity terminal of the rectifier switch tube to obtain a drain-source voltage signal of the rectifier switch tube in the conduction time; the protection circuit receives a sampling voltage signal representing output current information, wherein the drain-source voltage signal is compared with the sampling voltage signal to obtain a comparison result, and according to the comparison result, the protection circuit generates a protection control signal to control an output current of the power adapter; when the rectifier switch tube is connected to a low voltage side of an output of the power adapter, the protection circuit comprises: a first switch tube, a control terminal of the first switch tube being connected to the control terminal of the rectifier switch tube to receive the driving signal, and a first polarity terminal of the first switch tube being connected to the first polarity terminal of the rectifier switch tube to receive the drain-source voltage signal in the conduction time; and a first filter circuit connected to a second polarity terminal of the first switch tube to provide an average voltage of the drain-source voltage signal. Further comprising: a sampling resistor connected between an output of the power adapter and a reference ground, the output being configured to provide the output voltage, wherein a third input and a fourth input of the protection circuit are connected to two ends of the sampling resistor to sample the sampling resistor to obtain the sampling voltage signal. The protection circuit generates the protection control signal when a ratio of the drain-source voltage signal to a conduction resistance of the rectifier switch tube is not equal to a ratio of the sampling voltage signal to a resistance of the sampling resistor.

4. A protection circuit of a power adapter, the power adapter being configured to receive an input voltage and generate an output voltage, the power adapter comprising a rectifier switch tube configured to switch according to a driving signal to obtain the output voltage, characterized in that, a first input of the protection circuit is connected to a control terminal of the rectifier switch tube to obtain the driving signal of the rectifier switch tube to determine a conduction time of the rectifier switch tube, and a second input of the protection circuit is connected to a first polarity terminal of the rectifier switch tube to obtain a drain-source voltage signal of the rectifier switch tube in the conduction time; the protection circuit receives a sampling voltage signal representing output current information, wherein the drain-source voltage signal is compared with the sampling voltage signal to obtain a comparison result, and according to the comparison result, the protection circuit generates a protection control signal to control an output current of the power adapter; when the rectifier switch tube is connected to a high voltage side of an output of the power adapter, the protection circuit comprises: ​ ​ ​ 2. The protection circuit of claim 1, wherein ​ ​ ​ 3. The protection circuit of claim 2, wherein ​ ​ ​ ​ ​ ​ a voltage acquisition circuit, a first input terminal of the voltage acquisition circuit is connected with the first polarity terminal of the rectifier switch tube, and a second input terminal of the voltage acquisition circuit is connected with the second polarity terminal of the rectifier switch tube, for acquiring the drain-source voltage signal; a second switch tube, a control terminal of the second switch tube is connected with the control terminal of the rectifier switch tube, for receiving the driving signal, and a first polarity terminal of the second switch tube is connected with an output terminal of the voltage acquisition circuit to obtain the drain-source voltage signal in the on-time; and a second filter circuit, connected with a second polarity terminal of the second switch tube, for providing an average voltage of the drain-source voltage signal.

5. A power adapter, characterized by comprising: a protocol chip; and the protection circuit according to any one of claims 1 to 4, integrated in the protocol chip, for generating the protection control signal to control the output current of the power adapter.

6. A protection control method applied to the protection circuit according to any one of claims 1 to 4, for protecting a power adapter, the power adapter comprising a rectifier switch tube and a sampling resistor, characterized in that, the control method comprises: obtaining the driving signal of the rectifier switch tube to determine the on-time of the rectifier switch tube; obtaining the average voltage of the drain-source voltage signal of the rectifier switch tube in the on-time; receiving a sampling voltage signal representing the output current information; comparing the relationship between the average voltage of the drain-source voltage signal and the sampling voltage signal to obtain a comparison result; and generating a protection control signal to control the output current according to the comparison result.

7. The protective control method according to claim 6, characterized by, the protection control signal is generated when the ratio of the drain-source voltage signal to the on-resistance of the rectifier switch tube is not equal to the ratio of the sampling voltage signal to the resistance of the sampling resistor.

8. The protective control method according to claim 6, characterized by, the control method further comprises: filtering the drain-source voltage signal of the rectifier switch tube to obtain the average voltage of the drain-source voltage signal.

9. The protective control method according to claim 6, characterized by, the control method further comprises: when the protection control signal is valid, the power adapter controls the output of the input-side control signal and / or stops supplying power to the load.

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