CN113872423A - Protection circuit, power adapter and control method of protection circuit - Google Patents
Protection circuit, power adapter and control method of protection circuit Download PDFInfo
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- CN113872423A CN113872423A CN202111105588.3A CN202111105588A CN113872423A CN 113872423 A CN113872423 A CN 113872423A CN 202111105588 A CN202111105588 A CN 202111105588A CN 113872423 A CN113872423 A CN 113872423A
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- detection signal
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
Abstract
The application discloses a protection circuit, a power adapter and a control method of the protection circuit. The first end of the protection circuit is connected to one end of the rectifier switching tube to obtain a first detection signal related to the switching time of the rectifier switching tube, and the protection circuit receives a second detection signal representing output current information, wherein when the first detection signal is within a first threshold range and the second detection signal is within a second threshold range, the protection circuit generates a protection control signal to control the output current. The protection circuit can meet the requirement of a power limiting source under the condition that the sampling resistor is short-circuited.
Description
Technical Field
The present invention relates to the field of electronic circuit technologies, and in particular, to a protection circuit, a power adapter, and a control method of the protection circuit.
Background
Power adapters (Power adapters) are Power supply conversion devices for small portable electronic devices and electronic appliances, and are used to convert ac input signals into dc output voltages, and the types of Power adapters can be divided into wall-mounted Power adapters and desktop Power adapters according to the connection mode. The power adapter is widely matched with equipment such as a smart phone, a tablet computer, a security camera, a set-top box and a router.
Power adapters typically require products to meet Limited Power Supply (LPS) to meet security requirements. Typically, LPS requirements are met in two ways, one with an inherently limited power source whose output current must not exceed 8A, and the other with an inherently limited power source whose output current should be less than 5A.
Currently, it is common practice in the industry to implement current limiting for the power adapter through the primary control chip. Fig. 1 shows a schematic diagram of a conventional power adapter, as shown in fig. 1, a power adapter 100 includes a primary rectifier circuit 110, a flyback switching transformer T1, a secondary rectifier circuit 120, and a primary control chip 111, where the primary rectifier 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 rectifier circuit 120, and the secondary rectifier circuit 120 provides a dc output voltage according to the dc signal. After the primary side rectifying 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 by the primary side control chip is difficult to adapt to the current limiting requirement of the output current, and especially when the secondary side circuit is short-circuited, the current limiting requirement cannot be satisfied.
Accordingly, it is desirable to provide an improved protection circuit to effectively meet current limiting requirements.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a protection circuit, a power adapter, and a control method, which can satisfy a current limiting requirement in the case of a short circuit of a sampling circuit.
According to a first aspect of the present invention, a protection circuit of a power adapter is provided, the power adapter is configured to receive an input voltage and generate an output voltage, the power adapter includes a rectifying switch tube configured to perform a switching action according to a driving signal to obtain the output voltage, a first end of the protection circuit is connected to one end of the rectifying switch tube to obtain a first detection signal related to a switching time of the rectifying switch tube, and the protection circuit receives a second detection signal representing output current information, wherein when the first detection signal is within a first threshold range and the second detection signal is within a second threshold range, the protection circuit generates a protection control signal to control an output current of the power adapter.
Optionally, the method further includes: the sampling resistor is connected between the output end of the power adapter and a reference ground, the output end is used for providing the output voltage, and the second end and the third end of the protection circuit are respectively connected to the two ends of the sampling resistor so as to sample the sampling resistor to obtain the second detection signal.
Optionally, the protection circuit compares the first detection signal with a reference voltage to obtain a square wave signal representing the switching time of the rectifier switching tube, and a duty ratio of the square wave signal greater than a first predetermined value represents that the first detection signal is within the first threshold range.
Optionally, if the protection circuit detects that the peak voltage of the first detection signal is less than/equal to a predetermined voltage, the reference voltage is set between 0 and a first level, and if the protection circuit detects that the peak voltage of the first detection signal is greater than the predetermined voltage, the reference voltage is set between the output voltage and the sum of the output voltage and the first level.
Optionally, when detecting the average voltage of the first detection signal, the protection circuit further includes: and the filter circuit is connected between the first end of the protection circuit and one end of the rectifying switch tube and is used for providing the average voltage, wherein the protection circuit compares the average voltage with a second preset value, and the average voltage is larger than the second preset value and indicates that the first detection signal is in the first threshold range.
Optionally, the second detection signal is a sampling voltage, the protection circuit compares the sampling voltage with a threshold voltage, and the sampling voltage being smaller than the threshold voltage indicates that the second detection signal is within the second threshold range.
Optionally, the method further includes: the anode of the diode is connected to one end of the rectifying switching tube, which is used for providing the first detection signal, and the cathode of the diode is connected to the protection circuit; and a resistor connected between the cathode of the diode and a reference ground, wherein the diode and the resistor form a rectifying circuit to rectify the first detection signal.
Optionally, the control end of the rectification switch tube receives the driving signal, the first path end of the rectification switch tube is connected to a node of a power loop of the power adapter, the second path end of the rectification switch tube provides the output voltage, and the first end of the protection circuit is connected to any one of the control end, the first path end and the second path end of the rectification switch tube, so that the first detection signal is any one of the driving signal, the output voltage, superposition of the driving signal and the output voltage, and the output voltage after rectification.
According to a second aspect of the present invention, there is provided a power adapter comprising: a protocol chip; and the protection circuit is integrated in the protocol chip to generate the protection control signal to control the output current of the power adapter.
According to a third aspect of the present invention, there is provided a control method of a protection circuit for protecting a power adapter, the power adapter being configured to receive an input voltage and generate an output voltage, and perform a switching operation according to a driving signal by using a rectifying switching tube to obtain the output voltage, the control method comprising: obtaining a first detection signal related to the switching time of the rectifying switching tube; and receiving a second detection signal representing output current information, wherein when the first detection signal is within a first threshold range and the second detection signal is within a second threshold range, a protection control signal is generated to control the output current of the power adapter.
Optionally, the first detection signal is compared with a reference voltage to obtain a square wave signal representing the switching time of the rectifier switching tube, and a duty ratio of the square wave signal being greater than a first predetermined value represents that the first detection signal is within the first threshold range.
Optionally, if the peak voltage of the first detection signal is less than/equal to a predetermined voltage, the reference voltage is set between 0 and a first level, and if the peak voltage of the first detection signal is greater than the predetermined voltage, the reference voltage is set between the output voltage and the sum of the output voltage and the first level.
Optionally, when detecting the average voltage of the first detection signal, the control method further includes: filtering the voltage on one end of the rectifying switch tube to obtain the average voltage; and comparing the average voltage to a second predetermined value, the average voltage being greater than the second predetermined value being indicative of the first detection signal being within the first threshold range.
Optionally, the second detection signal is a sampling voltage, and the sampling voltage is compared with a threshold voltage, where the sampling voltage being smaller than the threshold voltage indicates that the second detection signal is within the second threshold range.
Optionally, the method further includes: and rectifying the first detection signal.
Optionally, the first detection signal is any one of the driving signal, the output voltage, a superposition of the driving signal and the output voltage, and the rectified output voltage.
The protection circuit, the power adapter and the control method provided by the invention judge whether the sampling resistor is short-circuited by detecting the first detection voltage related to the switching time of the rectification output tube and the second detection signal of the sampling resistor so as to further realize the current limiting of the output voltage.
Furthermore, the protection circuit, the power adapter and the control method can be compatible with the forms that the rectification output tube is positioned on the high-voltage side and the low-voltage side of the secondary coil, and the compatibility of the circuit is further improved.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:
FIG. 1 illustrates a schematic diagram of a conventional power adapter;
FIG. 2a shows a schematic diagram of a power adapter according to a first embodiment of the invention;
FIG. 2b shows a voltage waveform diagram of the power adapter according to FIG. 2 a;
FIGS. 2c and 2d respectively show schematic diagrams of a protection mechanism of the power adapter according to FIG. 2 a;
FIG. 3a shows a schematic diagram of a power adapter according to a second embodiment of the invention;
FIG. 3b shows a voltage waveform diagram of the power adapter according to FIG. 3 a;
FIG. 4a shows a schematic diagram of a power adapter according to a third embodiment of the invention;
FIG. 4b shows a voltage waveform diagram of the power adapter according to FIG. 4 a;
FIG. 5 shows a schematic diagram of a power adapter according to a fourth embodiment of the invention;
FIG. 6 shows a schematic diagram of a power adapter according to a fifth embodiment of the invention;
fig. 7 shows a flowchart of a control method of a protection circuit according to an embodiment of the present invention.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown in the figures.
In the following description, numerous specific details of the invention, such as structure, materials, dimensions, processing techniques and techniques of the devices are described in order to provide a more thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.
It should be understood that, in the embodiments of the present application, a and B are connected/coupled, which means that a and B may be connected in series or in parallel, or a and B may pass through other devices, and the embodiments of the present application do not limit this.
The utility model provides a protection circuit of power adapter, power adapter is used for receiving input voltage and produces output voltage, power adapter includes the rectification switch tube, be used for according to drive signal switching action, in order to obtain output voltage, protection circuit first end is connected to the one end of rectification switch tube, in order to obtain the first detected signal that is relevant with the on-off time of rectification switch tube, and protection circuit receives the second detected signal that represents output current information, wherein, when first detected signal is in first threshold range, and the second detected signal is in the second threshold range, produce the protection control signal in order to control the output current of protection circuit.
In the embodiment of the present disclosure, the meaning of "the first detection signal related to the switching time of the rectifier switching tube" means that the high-low transition of the first detection signal can indicate the switching period of the rectifier switching tube, for example, the high level of the first detection signal indicates the on state of the rectifier switching tube, and the low level of the first detection signal indicates the off state of the rectifier switching tube. The protection circuit of the embodiment of the disclosure obtains a first detection signal representing the switching period of the rectifier switching tube, and can judge whether the sampling resistor is short-circuited or not by combining the sampling current/sampling voltage provided by the sampling resistor, thereby starting the protection mechanism of the protection circuit.
The protection circuit is used for protecting a power adapter, and the power adapter further comprises a secondary coil which is used for receiving an input voltage and generating an output voltage based on the electromagnetic induction principle. The rectification switch tube is selectively connected to the high-voltage side or the low-voltage side of the secondary side coil, the first end of the protection circuit is connected to any one of the control end, the first path end and the second path end of the rectification switch tube, so that the first detection signal is any one of the driving signal, the output voltage, the superposition of the driving signal and the output voltage and the rectified output voltage, the signals can represent the switching period of the rectification switch tube, and namely the first detection signal can represent the switching period of the rectification switch tube.
In an embodiment of the present disclosure, there is also provided a power adapter, for example, including the protection circuit and the protocol chip as described above, where the protection circuit is integrated inside the protocol chip to generate a protection control signal to control an output current of the power adapter. The type of Power adapter is, for example, a Power Delivery (PD) Power adapter, which complies with a PD protocol and includes a PD protocol chip.
Based on some configurable embodiments, some alternative embodiments are given below to describe the specific circuit structure of the protection circuit, and embodiments of the protection circuit provided in the present application will be described below with reference to the accompanying drawings.
FIG. 2a shows a schematic diagram of a power adapter according to a first embodiment of the invention; fig. 2b shows a voltage waveform diagram of the power adapter according to fig. 2 a.
As shown in fig. 2a, the power adapter 200 includes a power adapter and a protection circuit, wherein the power adapter includes a secondary winding N2 and a rectifying switch tube M1 for implementing voltage conversion, and the protection circuit includes a sampling resistor R1, a protection circuit 210, and a Synchronous Rectifier Driver (SR Driver)220 for implementing Synchronous rectification and circuit protection. The power adapter 200 is used to convert an input signal Vi into an output voltage Vo, and the output voltage Vo provided by the power adapter meets the current limiting requirement and the power limiting source requirement.
In this embodiment, the high side of the secondary winding N2 provides the output voltage Vo, and the low side is connected to a 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.
As an example, the power adapter 200 includes a transformer in which the secondary winding N2 is included. In this embodiment, the transformer includes a primary winding N1 and a secondary winding N2, the primary winding N1 receives an input signal Vi, and the secondary winding N2 generates an output voltage Vo based on the principle of electromagnetic induction. The transformer is, for example, a flyback transformer, the primary coil N1 and the secondary coil N2 are, for example, coil windings arranged oppositely or coil windings wound on the same iron core in opposite winding directions, and the primary coil N1 and the secondary coil N2 may be single coil windings or formed by connecting a plurality of coil windings in series, respectively, it should be understood that the form of the transformer, the primary coil N1 and the secondary coil N2 may be formed by using various conventional coil windings, and the specific form, material and the like of the transformer are not limited in the present application. Optionally, the primary winding N1 is further connected to a primary rectifying circuit, a primary switch, and other components (not shown).
As another example, the secondary coil N2 is in an electromagnetic field generated by an input signal in the primary coil N1 and generates an output voltage Vo based on the principle of electromagnetic induction, the primary coil N1 and the secondary coil N2 are respectively located in two different devices, for example, the primary coil N1 is located in a wireless charging device for supplying power, and the secondary coil N2 is located in a receiving device for receiving power.
The rectifying switching tube M1 is connected to the high-voltage side and/or the low-voltage side of the secondary winding N2 for rectifying the output voltage Vo according to a driving signal Vg supplied from, for example, the synchronous rectifier driver 220. The sampling resistor R1 is connected between the secondary winding N2 and ground reference. The first end of the protection circuit 210 is connected to the control end of the rectifier switch tube M1 to sample the driving signal Vg, the second end and the third end of the protection circuit 210 are respectively connected to the two ends of the sampling resistor R1 to sample the second detection signal of the sampling resistor R1, when the driving signal Vg is within the first threshold range and the second detection signal is within the second threshold range, the representation is that the overload output is performed and the short circuit is performed at the moment, and the protection circuit 210 generates a protection control signal to control the output current.
As an example, the second detection signal includes a sampling current, and the protection circuit 210 compares a duty ratio of the driving signal Vg with a first predetermined value, and compares the sampling current with a threshold current, wherein the duty ratio of the driving signal Vg being greater than the first predetermined value indicates that the driving signal Vg is within a first threshold range, and the sampling current being less than a second predetermined value indicates that the second detection signal is within a second threshold range.
In this embodiment, the rectifying switch tube M1 is connected to the low-voltage side of the secondary winding N2, and the reference voltage is set between 0 and a first level, such as the level of the power source VCC or the gate-source voltage of the rectifying switch tube M1, and when the driving signal Vg is greater than the reference voltage Vg _ threshold (the reference voltage Vg _ threshold is selected from 0 to the first level), it is considered as the effective duty time of the driving signal Vg. When the duty ratio is greater than the first predetermined value and the sampling current is less than the threshold current, 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, performs a protection operation.
In the embodiment of the disclosure, when the circuit normally works, the protection circuit 210 may perform current-limiting protection on the power adapter, and when the circuit is short-circuited, the protection circuit 210 may perform a corresponding protection circuit, for example, directly cut off the output voltage to protect the circuit from being damaged.
As shown in fig. 2b, in an exemplary driving period Ts, the driving signal Vg is switched from a high level to a low level, and the duty ratio thereof is D, and in the driving period Ts, when the driving signal Vg is greater than the reference voltage Vg _ threshold, the driving signal Vg is regarded as the effective duty ratio time D × Ts of the driving signal Vg, that is, the duty ratio D of the driving signal Vg can be obtained. If the protection circuit 210 detects that the duty ratio D is greater than the first predetermined value Dref and if the protection circuit 210 further detects that the sampling current is less than the threshold current Iref, the protection circuit 210 determines that the sampling resistor R1 is short-circuited, and generates a protection control signal to control the output voltage Vo, i.e., to perform a protection operation, e.g., to turn off the current of the output voltage Vo.
As an example, the protection circuit 210 has, for example, a control terminal (not shown) for providing a control signal, and when the protection circuit 210 determines that the sampling resistor R1 is short-circuited, the control terminal provides an effective control signal to the high-voltage side of the secondary winding N2 to control the output voltage Vo, thereby achieving the purpose of the protection circuit. It should be understood that when the protection circuit 210 determines that the sampling resistor R1 is short-circuited, the current of the output voltage Vo may be controlled in other various manners to achieve the purpose of circuit protection, and the present application does not limit the manner in which the protection circuit 210 specifically controls the current of the output voltage Vo.
Optionally, the power adapter 200 further includes a capacitor C1, and the capacitor C1 is connected in parallel between the high-voltage side and the low-voltage side of the secondary winding N2, and is used for supplying power to the load when the freewheeling current in the circuit decreases to 0, and at this time, the rectifying switch tube M1 should be in an off state.
Some examples of the resonant circuit of the embodiments of the present invention are described above, however, the embodiments of the present invention are not limited thereto, and there may be other extensions and modifications.
For example, it should be understood that the reference ground potential in the foregoing embodiments may be replaced in alternative embodiments with other non-zero reference potentials (having positive or negative voltage magnitudes) or controlled varying reference signals.
For another example, the resistors and the capacitors provided in the embodiments of the present application may be lumped-parameter capacitor elements and resistor elements, or may be other equivalent elements having functions similar to those of the capacitors and the resistors, where the equivalent structures described herein, such as but not limited to microstrip lines, varactors, conductor structures with certain patterns, and the like, can provide inductive impedance and/or capacitive impedance.
Also, those of ordinary skill in the art will recognize that the various example structures and methods described in connection with the embodiments disclosed herein can be implemented with various configurations or adjustments, with reasonable variations on each structure or structure, but such implementations should not be considered as beyond the scope of the present application. Furthermore, it should be understood that the connection relationship between the various components of the amplifier in the foregoing figures in this application embodiment is an illustrative example, and does not set any limit to this application embodiment.
Fig. 2c and 2d respectively show schematic diagrams of a protection mechanism of the power adapter according to fig. 2a, based on an exemplary configuration. On the basis of the basic structure of the power adapter 200 shown in fig. 2a, a specific circuit for current limiting protection of the protection circuit is provided in the power adapter 200 shown in fig. 2c and 2d, and the basic structure of the power adapter 200 will not be described herein again. It should be understood that the mechanism of current limiting protection by the protection circuit shown in fig. 2c and 2d is only an exemplary illustration, and in the embodiment of the present disclosure, the specific adjustment manner of the output current by the protection circuit in the power adapter is not limited.
As shown in fig. 2c, the power adapter 200 further includes a switch Q1, a first path terminal of the switch Q1 is connected to the high voltage side of the secondary winding N2, a second path terminal provides an output terminal of the power adapter 200, and a control terminal receives the control signal provided by the protection circuit 210. When the protection circuit 210 determines that the power adapter 200 is in the normal operation state, the protection circuit 210 outputs a control signal in an active state, so that the first path terminal and the second path terminal of the switching tube Q1 are in a conducting state to provide an active output voltage Vo, and the protection circuit 210 performs current-limiting protection on the output voltage; when the protection circuit 210 detects that the driving signal Vg is within the first threshold range and the second detection signal Vg is within the second threshold range, that is, detects that the sampling resistor R1 is short-circuited, the protection circuit 210 outputs a control signal in an invalid state, so that the first path terminal and the second path terminal of the switching tube Q1 are in an off state, thereby suspending the supply of the output voltage.
Fig. 2d shows a closed-loop regulation of the output current, and for clarity the primary side PWM chip and the primary side coil N1 are placed on either side of the power adapter 200, it being understood that the primary side coil N1 and the primary side PWM chip should be electrically connected in the actual circuit. In fig. 2d, the optical coupler OCEP is further included, the optical coupler OCEP internally includes a light emitting diode and a photo resistor, the high-voltage side of the secondary winding N2 is connected to the anode of the light emitting diode via a resistor R0, the OPTO pin of the protection circuit 210 serves as a control pin and is connected to the cathode of the light emitting diode to send a control signal to the light emitting diode to adjust the magnitude of the OPTO-coupler current of the light emitting diode, so as to adjust the conduction state of the photo resistor, one end of the photo resistor is connected to the reference ground, and the other end of the photo resistor is connected to a Compensation (COMP) pin of the primary PWM chip. The circuit adjusts the current of the optocoupler through the protection circuit 210, and then adjusts the voltage of a compensation pin of the primary side PWM chip, so that closed-loop adjustment is realized. When the protection circuit 210 determines that the power adapter 200 is in the normal working state, the protection circuit 210 outputs a control signal in an effective state, so that the current of the optocoupler is small to provide an effective output voltage Vo; when the protection circuit 210 detects that the driving signal Vg is within the first threshold range and the second detection signal Vg is within the second threshold range, that is, when the sampling resistor R1 is detected to be short-circuited, the protection circuit 210 outputs a control signal in an invalid state, so that the current of the optocoupler is large, the voltage of the compensation pin of the primary side PWM chip is pulled down, that is, the transmission of the PWM signal is turned off, thereby effectively limiting the magnitude of the output current and realizing the requirement of limiting the power source.
FIG. 3a shows a schematic diagram of a power adapter according to a second embodiment of the invention; fig. 3b shows a voltage waveform diagram of the power adapter according to fig. 3 a.
As shown in fig. 3a, the power adapter 300 includes a secondary winding N3, a rectifying switch tube M2, a sampling resistor R2, a capacitor C2, a protection circuit 310, and a synchronous rectifier driver 320, and the power adapter 300 is used for converting an input signal Vi into an output voltage Vo, and the output voltage Vo provided by the power adapter meets the current-limiting requirement and the power-limiting source requirement. The secondary winding N3, the rectifying switch tube M2, the sampling resistor R2, the protection circuit 310 and the synchronous rectifier driver 320 provided in fig. 3a correspond to the secondary winding N2, the rectifying switch tube M1, the sampling resistor R1, the capacitor C1, the protection circuit 210 and the synchronous rectifier driver 220 provided in fig. 2 one to one, and have the same basic functions, which is not repeated herein.
In this embodiment, the rectifying switching tube M2 is connected to the high-voltage side of the secondary winding N3. As shown in fig. 3b, since it is detected that the switching waveform of the rectifying switching tube M2 connected to the high-voltage side is composed of the driving signal and the winding voltage, and has positive and negative voltages, and direct connection to the chip will affect it, it is necessary to perform a rectifying process on the voltage signal Vg representing the switching waveform. The voltage signal Vg is subjected to a rectification process using, for example, the rectifier circuit 330. The rectifying circuit 330 includes, for example, a diode D1 and a resistor R3, the anode of the diode D1 is connected to the voltage signal Vg, the cathode is connected to the protection circuit 310, and the resistor R3 is connected between the cathode of the diode D1 and the ground reference.
The second detection signal collected by the sampling resistor R2 includes a sampled current. The protection circuit 310 compares the duty ratio of the rectified voltage signal Vg _ sense with a first predetermined value, and compares the sampling current with a threshold current, wherein the duty ratio of the voltage signal Vg is greater than the first predetermined value and indicates that the voltage signal Vg is within a first threshold range, and the sampling current is less than the threshold current and indicates that the second detection signal is within a second threshold range.
In this embodiment, the rectifying switch tube M2 is connected to the high-voltage side of the secondary winding N3, and the reference voltage is set between the output voltage Vo to the sum of the output voltage Vo and a first level, such as the level of the power source VCC or the gate-source voltage of the rectifying switch tube M2, and the effective duty time of the driving signal component of the voltage signal Vg is considered when the time when the rectified voltage signal Vg _ sense is greater than the reference voltage Vg _ threshold (the threshold voltage Vg _ threshold is selected from between the output voltage Vo to the sum of the output voltage Vo and the first level). In an exemplary driving period Ts, the duty ratio of the driving signal component in the rectified voltage signal Vg _ sense is D, and in the driving period Ts, when the voltage signal Vg _ sense is greater than the reference voltage Vg _ threshold, the voltage signal Vg _ sense is regarded as the effective duty ratio time D × Ts of the driving signal, that is, the duty ratio D of the driving signal can be obtained. When the duty ratio is greater than the first predetermined value and the sampling current is less than the threshold current, 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, performs a protection operation.
FIG. 4a shows a schematic diagram of a power adapter according to a third embodiment of the invention; fig. 4b shows a voltage waveform diagram of the power adapter according to fig. 4 a.
As shown in fig. 4a, the power adapter 400 includes a secondary winding N4, a rectifying switch tube M3, a sampling resistor R4, a capacitor C3, a protection circuit 410, a synchronous rectifier driver 420, and a rectifying circuit 430, and the power adapter 400 is used for converting an input signal Vi into an output voltage Vo, and provides the output voltage Vo meeting the current-limiting requirement and the power-limiting source requirement. The secondary winding N4, the rectifying switch tube M3, the sampling resistor R4, the protection circuit 410, and the synchronous rectifier driver 420 provided in fig. 4a correspond to the secondary winding N3, the rectifying switch tube M2, the sampling resistor R2, the capacitor C2, the protection circuit 310, the synchronous rectifier driver 320, and the rectifying circuit 330 provided in fig. 3a one-to-one, and have the same basic functions, which is not repeated herein.
In this embodiment, the rectifying switch transistor M3 is connected to the high-voltage side of the secondary winding N4, and the first terminal of the protection circuit 410 is connected to the high-voltage side of the secondary winding N4 to receive the high-voltage side voltage V _ transfomer of the secondary winding N4. As shown in fig. 4b, the high-side voltage V _ fransformer is related to the driving voltage of the rectifying switch tube M3, and since the rectifying switch tube M3 connected to the high-side has positive and negative voltages and is directly connected to the chip, it is necessary to rectify the high-side voltage V _ fransformer. The high-side voltage V _ transfomer is rectified by, for example, a rectifier circuit 430. The rectifying circuit 430 includes, for example, a diode D2 and a resistor R5, the anode of the diode D2 is connected to the high-voltage side of the secondary winding N4, the cathode is connected to the protection circuit 410, and the resistor R4 is connected between the cathode of the diode D1 and the reference ground.
The second detection signal collected by the sampling resistor R4 includes a sampled current. The protection circuit 410 compares the duty ratio of the rectified voltage signal V _ sense with a first predetermined value, and compares the sampling current with a threshold current, wherein the duty ratio of the voltage signal V _ sense greater than the first predetermined value indicates that the voltage signal V _ sense is within a first threshold range, and the sampling current less than a second predetermined value indicates that the second detection signal is within a second threshold range.
In this embodiment, the rectifying switch tube M3 is connected to the high-voltage side of the secondary winding N4, and the reference voltage is set between the output voltage Vo to the sum of the output voltage Vo and a first level, such as the level of the power source VCC or the gate-source voltage of the rectifying switch tube M3, and the effective duty time of the driving signal component of the high-voltage side voltage V _ transducer is considered when the rectified voltage signal V _ sense is greater than a threshold voltage Vg _ threshold (the threshold voltage Vg _ threshold is selected from the sum of the output voltage Vo to the output voltage Vo and the first level). In an exemplary driving period Ts, the duty ratio of the driving signal component in the rectified voltage signal V _ sense is D, and in the driving period Ts, when the voltage signal V _ sense is greater than the reference voltage Vg _ threshold, the voltage signal V _ sense is regarded as the effective duty ratio time D × Ts of the driving signal, that is, the duty ratio D of the driving signal can be obtained. When the duty ratio is greater than the first predetermined value and the sampling current is less than the threshold current, the protection circuit 410 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, performs a protection operation.
In the embodiments shown in fig. 2a, fig. 3a and fig. 4a, the duty ratio of the first detection signal and the sampling current of the sampling resistor are directly used to determine whether the sampling resistor is short-circuited, so that the power adapter 200/300/400 may use the same protection circuit, and the protection circuit may perform differentiated control on the power adapter 200/300/400. Specifically, after the first end of the protection circuit receives the driving voltage Vg, if the protection circuit detects that the peak voltage of the first end is less than or equal to a predetermined voltage, it is determined that the rectifier switch tube is connected to the low-voltage side of the secondary winding, and the reference voltage is set between 0 and a first level, and if the protection circuit detects that the peak voltage of the first end is greater than the predetermined voltage, it is determined that the rectifier switch tube is connected to the high-voltage side of the secondary winding, and the reference voltage is set between the output voltage Vo and the sum of the output voltage Vo and the first level.
Fig. 5 shows a schematic diagram of a power adapter according to a fourth embodiment of the invention. As shown in fig. 5, the power adapter 500 includes a secondary winding N5, a rectifying switch tube M4, a sampling resistor R7, a capacitor C4, a protection circuit 510, and a synchronous rectifier driver 520, and the power adapter 500 is used for converting an input signal Vi into an output voltage Vo, and provides the output voltage Vo satisfying a current-limiting requirement and a power-limiting source requirement. The secondary winding N5, the rectifying switch tube M4, the sampling resistor R7, the protection circuit 510 and the synchronous rectifier driver 520 provided in fig. 5 correspond to the secondary winding N2, the rectifying switch tube M1, the sampling resistor R1, the capacitor C1, the protection circuit 210 and the synchronous rectifier driver 220 provided in fig. 2 one to one, and have the same basic functions, and the description thereof is omitted here.
In this embodiment, the rectifying switch tube M4 is connected to the low-voltage side of the secondary winding N5, and the power adapter 500 further includes a filter circuit 540, where the filter circuit 540 is configured to convert the voltage at one end of the rectifying switch tube M4 into an average voltage Vg _ average. The first end of the protection circuit 510 is connected to the control end of the rectifying switch tube M4 through the filter circuit 540 to receive the filtered driving signal Vg (i.e., the average voltage Vg _ average), the protection circuit 510 compares the average voltage Vg _ average received by the first end with a second predetermined value, and the average voltage Vg _ average greater than the second predetermined value represents that the driving signal Vg is within the first threshold range. The second end and the third end of the protection circuit 510 are connected in parallel to two ends of the sampling resistor, sampling voltages at two ends of the sampling resistor are collected, the protection circuit 510 compares the sampling voltages with a threshold voltage, and the sampling voltages smaller than the threshold voltage represent that the second detection signal is within a second threshold range.
In this embodiment, if the protection circuit 510 detects that the average voltage Vg _ average is greater than the second predetermined value and the sampling voltage is less than the threshold voltage, the protection circuit 510 determines that the sampling resistor R5 is short-circuited, and generates the protection control signal to control the current of the output voltage Vo, i.e., perform the protection operation.
As an example, the filter circuit 540 is an RC filter, the filter circuit 540 includes a resistor R6 and a capacitor C5, the resistor R6 is connected between the driving signal Vg and the first terminal of the protection circuit 510, and the capacitor C5 is connected between the first terminal of the protection circuit 510 and the reference ground.
Fig. 6 shows a schematic diagram of a power adapter according to a fifth embodiment of the invention. As shown in fig. 6, the power adapter 600 includes a secondary winding N6, a rectifying switch tube M5, a sampling resistor R8, a capacitor C6, a protection circuit 610, a synchronous rectifier driver 620, and a filter circuit 640, where the filter circuit 640 includes a resistor R9 and a capacitor C7, the power adapter 600 is configured to convert an input signal Vi into an output voltage Vo, and the output voltage Vo provided by the power adapter meets the current-limiting requirement and the power-limiting source requirement. The secondary winding N6, the rectifying switch tube M5, the sampling resistor R8, the protection circuit 610, the capacitor C5, the synchronous rectifier driver 620, and the filter circuit 640 provided in fig. 6 correspond to the secondary winding N5, the rectifying switch tube M3, the sampling resistor R7, the capacitor C5, the protection circuit 510, the synchronous rectifier driver 520, and the filter circuit 540 provided in fig. 5 one to one, and have the same basic functions, and the description thereof is omitted here.
In this embodiment, the rectifying switching tube M5 is connected to the high-voltage side of the secondary winding N6. The protection circuit 610 compares the average voltage Vg _ average received by the first terminal with a second predetermined value, and the average voltage Vg _ average larger than the second predetermined value represents that the driving signal Vg is within the first threshold range. The second end and the third end of the protection circuit 610 are connected in parallel to two ends of the sampling resistor R8, sampling voltages at two ends of the sampling resistor R8 are collected, the protection circuit 610 compares the sampling voltages with threshold voltages, and the fact that the sampling voltages are smaller than the threshold voltages indicates that the second detection signal is within a second threshold range.
In this embodiment, if the protection circuit 610 detects that the average voltage Vg _ average is greater than the second predetermined value and the sampling voltage is less than the threshold voltage, the protection circuit 610 determines that the sampling resistor R6 is short-circuited, and generates the protection control signal to control the current of the output voltage Vo, i.e., perform the protection operation.
In the embodiment shown in fig. 5 and 6, since the average value of the high-side voltage V _ fransformer of the secondary winding N5/N6 is 0, the power adapter 500/600 may use the same protection circuit, and the detection mechanism and the control method of the power adapter 500/600 by the protection circuit are the same, and there is no need to perform differential control.
It should be understood that in the embodiments shown in fig. 3a, fig. 4a, fig. 5 and fig. 6, the protection circuit may adopt the protection mechanism shown in fig. 2c and/or fig. 2d to achieve the purpose of circuit protection, and may also adopt a conventional protection mechanism to perform current limiting protection to achieve the purpose of circuit protection, and the present application does not limit the means for specifically implementing circuit protection by the protection circuit.
Fig. 7 shows a flowchart of a control method of a protection circuit according to an embodiment of the present invention. The control method of the protection circuit includes steps S1 to S3, the control method of the protection circuit is used for protecting a power adapter, the power adapter is used for receiving an input voltage and generating an output voltage, and the protection circuit can be applied to any one of the power adapters or the protection circuits shown in fig. 2a, 3a, 4a, 5 and 6.
In step S1, a first detection signal related to the switching time of the rectifying switching tube is obtained.
In step S2, a second detection signal is received that is representative of the output current information.
In step S3, when the first detection signal is within the first threshold range and the second detection signal is within the second threshold range, a protection control signal is generated to control the output current.
Optionally, the first detection signal is compared with a reference voltage to obtain a square wave signal representing the switching time of the rectifier switching tube, and the duty ratio of the square wave signal greater than a first predetermined value represents that the first detection signal is within a first threshold range.
Alternatively, the reference voltage is set between 0 and the first level if the peak voltage of the first detection signal is less than/equal to a predetermined voltage, and the reference voltage is set between the output voltage and the sum of the output voltage and the first level if the peak voltage of the first detection signal is greater than the predetermined voltage.
Optionally, when detecting the average voltage of the first detection signal, the control method further includes: filtering the voltage on one end of the rectifying switch tube to obtain an average voltage; and comparing the average voltage with a second predetermined value, the average voltage being greater than the second predetermined value indicating that the first detection signal is within the first threshold range.
Optionally, the second detection signal is a sampling voltage, the sampling voltage is compared with a threshold voltage, and the sampling voltage being smaller than the threshold voltage indicates that the second detection signal is within a second threshold range.
Optionally, the method further includes: and rectifying the first detection signal.
Optionally, the first detection signal is any one of a driving signal, an output voltage, a superposition of the driving signal and the output voltage, and a rectified output voltage.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation 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 may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.
Claims (16)
1. A protection circuit of a power adapter for receiving an input voltage and generating an output voltage, the power adapter comprising a rectifying switching tube for performing a switching action according to a driving signal to obtain the output voltage,
the first end of the protection circuit is connected to one end of the rectifying switch tube to obtain a first detection signal related to the switching time of the rectifying switch tube, and the protection circuit receives a second detection signal representing output current information,
when the first detection signal is within a first threshold range and the second detection signal is within a second threshold range, the protection circuit generates a protection control signal to control the output current of the power adapter.
2. The protection circuit of claim 1, further comprising: a sampling resistor connected between an output of the power adapter and a reference ground, the output for providing the output voltage,
and the second end and the third end of the protection circuit are respectively connected to two ends of the sampling resistor so as to sample the sampling resistor to obtain the second detection signal.
3. The protection circuit of claim 1, wherein the protection circuit compares the first detection signal to a reference voltage to obtain a square wave signal indicative of a switching time of the rectifier switching tube, wherein a duty cycle of the square wave signal being greater than a first predetermined value is indicative of the first detection signal being within the first threshold range.
4. The protection circuit of claim 3,
if the protection circuit detects that the peak voltage of the first detection signal is less than/equal to a predetermined voltage, the reference voltage is set between 0 and a first level,
the reference voltage is set between the output voltage to a sum of the output voltage and the first level if the protection circuit detects that the peak voltage of the first detection signal is greater than the predetermined voltage.
5. The protection circuit according to claim 1, wherein when detecting the average voltage of the first detection signal, the protection circuit further comprises:
a filter circuit connected between the first end of the protection circuit and one end of the rectification switch tube for providing the average voltage,
wherein the protection circuit compares the average voltage to a second predetermined value, the average voltage being greater than the second predetermined value being indicative of the first detection signal being within the first threshold range.
6. The protection circuit of claim 1 or 2, wherein the second detection signal is a sampled voltage, and wherein the protection circuit compares the sampled voltage to a threshold voltage, wherein a value of the sampled voltage less than the threshold voltage indicates that the second detection signal is within the second threshold range.
7. The protection circuit of claim 1, further comprising:
the anode of the diode is connected to one end of the rectifying switching tube, which is used for providing the first detection signal, and the cathode of the diode is connected to the protection circuit; and
a resistor connected between the cathode of the diode and a ground reference,
the diode and the resistor form a rectifying circuit to rectify the first detection signal.
8. The protection circuit of claim 1, wherein the control terminal of the rectifying switch tube receives the driving signal, a first path terminal of the rectifying switch tube is connected to a node of a power loop of the power adapter, a second path terminal of the rectifying switch tube provides the output voltage,
the first end of the protection circuit is connected to any one of the control end, the first path end and the second path end of the rectification switch tube, so that the first detection signal is any one of the driving signal, the output voltage, superposition of the driving signal and the output voltage and the rectified output voltage.
9. A power adapter, comprising:
a protocol chip; and
the protection circuit of any one of claims 1 to 8, integrated within the protocol chip to generate the protection control signal to control the output current of the power adapter.
10. A control method for a protection circuit, which is used for protecting a power adapter, wherein the power adapter is used for receiving an input voltage and generating an output voltage, and the power adapter performs a switching action according to a driving signal by using a rectifying switch tube so as to obtain the output voltage, and the control method comprises the following steps:
obtaining a first detection signal related to the switching time of the rectifying switching tube; and
receiving a second detection signal indicative of the output current information,
when the first detection signal is within a first threshold range and the second detection signal is within a second threshold range, a protection control signal is generated to control the output current of the power adapter.
11. The control method of claim 10, wherein the first detection signal is compared to a reference voltage to obtain a square wave signal indicative of the switching time of the rectifier switching tube, wherein a duty cycle of the square wave signal greater than a first predetermined value is indicative of the first detection signal being within the first threshold range.
12. The control method according to claim 11, wherein the reference voltage is set between 0 and a first level if a peak voltage of the first detection signal is less than/equal to a predetermined voltage,
the reference voltage is set between the output voltage to a sum of the output voltage and the first level if the peak voltage of the first detection signal is greater than the predetermined voltage.
13. The control method according to claim 10, wherein when detecting the average voltage of the first detection signal, the control method further comprises:
filtering the voltage on one end of the rectifying switch tube to obtain the average voltage; and
comparing the average voltage to a second predetermined value, the average voltage being greater than the second predetermined value being indicative of the first detection signal being within the first threshold range.
14. The control method of claim 10, wherein the second detection signal is a sampled voltage, and wherein comparing the sampled voltage to a threshold voltage, wherein a sampled voltage less than the threshold voltage indicates that the second detection signal is within the second threshold range.
15. The control method according to claim 10, characterized by further comprising: and rectifying the first detection signal.
16. The control method according to claim 10, wherein the first detection signal is any one of the drive signal, the output voltage, a superposition of the drive signal and the output voltage, and the rectified output voltage.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111105588.3A CN113872423A (en) | 2021-09-22 | 2021-09-22 | Protection circuit, power adapter and control method of protection circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111105588.3A CN113872423A (en) | 2021-09-22 | 2021-09-22 | Protection circuit, power adapter and control method of protection circuit |
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| CN113872423A true CN113872423A (en) | 2021-12-31 |
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| CN202111105588.3A Pending CN113872423A (en) | 2021-09-22 | 2021-09-22 | Protection circuit, power adapter and control method of protection circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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