CN219351551U

CN219351551U - Power adapter

Info

Publication number: CN219351551U
Application number: CN202223459872.3U
Authority: CN
Inventors: 林政毅; 黄钰伦
Original assignee: Delta Electronics Inc
Current assignee: Delta Electronics Inc
Priority date: 2022-12-23
Filing date: 2022-12-23
Publication date: 2023-07-14
Anticipated expiration: 2032-12-23

Abstract

The power adapter comprises a power path, a current detection resistor, a control unit, a protection switch, a synchronous rectification circuit and a feedback circuit. The power path is coupled between the transformer and an output side of the power adapter. The current detection resistor is coupled to the power path. The control unit is coupled to the current detecting resistor. The protection switch is coupled to the power path. The synchronous rectification circuit is coupled with the transformer and the protection switch. The feedback circuit is coupled between the synchronous rectification circuit and the control unit to feed back a voltage signal of the output voltage of the synchronous rectification circuit to the control unit. When the control unit judges that the detection voltage of the current detection resistor is smaller than a first threshold value and the output voltage of the synchronous rectification circuit is larger than a second threshold value, the control unit controls the protection switch to be not conducted.

Description

Power adapter

Technical Field

The present disclosure relates to a power adapter, and more particularly to a power adapter with power source limiting capability.

Background

In the information technology equipment safety standard IEC/EN/UL 60950-1-2, a power source (limited power source, LPS) safety standard for power source type products such as power supplies and power adapters is established. In the safety standard, the information technology equipment is provided with a fireproof shell; however, if the main circuit of the device is powered by the LPS power supply, that is, the voltage, current and energy in the circuit are all below the specified values in the UL60950-1-2table 2b standard, the device does not need to have a high fire-class housing (fire enclosure), in other words, the device can use the housing material of the HB combustion class specified in UL 94. The HB combustion grade shell material has lower price, better physical property and easy meeting the environmental protection requirement. In addition, the aforementioned standards and specifications are equally applicable to power adapters having universal serial bus power transfer (universal serial bus power delivery, USB PD) functionality.

There are two ways to achieve the LPS standard requirement of the power adapter, one is an inherent power limiting source (inherently limited power source) and the other is an extrinsic power limiting source (non-inherently limited power source). In short, if the requirements of the LPS standard are met, the output of the power adapter adopting the inherent power limiting source is not more than 8A/100VA; while for power adapters employing extrinsic limited power sources, the current rating of the current limiting protection devices (e.g., fuses) should be no greater than 5A. In addition, if the output end is not provided with a current limiting protection device, the output voltage of the current limiting protection device is less than 30V, and when the single fault (single fault) test is performed in the system, if the output voltage is 20V, the output current cannot exceed 5A, and the total output power cannot exceed 100VA. If the current or power limit is exceeded, a protection mechanism, such as current limiting, shutdown, latch off, or auto recovery (auto recovery), is activated.

However, as consumer electronics evolve and power requirements increase, power adapters with greater output power capabilities (e.g., 90-96W) may have rated output currents or powers approaching the upper limits (8A and 100 VA) specified by the LPS standard. If the output power limitation standard of the LPS standard is to be met, and meanwhile, the cost is reduced without arranging a current limiting protection device on the output side, the over-current or over-power protection point is possibly caused to be too close to the rated output current or power, so that the design is difficult, or the protection points of products are different due to the errors of the used elements during mass production, and further, the protection of some products is easy to be triggered by mistake, so that the quality problem is generated. Therefore, such power adapters with larger output power are generally more difficult to meet the specifications of the LPS standard and to get certification.

Therefore, how to develop a power adapter that can improve the above prior art is an urgent need at present.

Disclosure of Invention

The present disclosure is directed to a power adapter, which is based on the output voltage of a synchronous rectification circuit in the power adapter to simplify the circuit design, and thereby achieve the precise limitation and protection of the output power of the power adapter, so that the power adapter with a larger output power meets the specification of the LPS standard.

In order to achieve the above objective, the present disclosure provides a power adapter, which includes a power path, a current detection resistor, a control unit, a protection switch, a synchronous rectification circuit and a feedback circuit. The power path is coupled between the transformer and an output side of the power adapter. The current detection resistor is coupled to the power path. The control unit is coupled to the current detecting resistor. The protection switch is coupled to the power path. The synchronous rectification circuit is coupled with the transformer and the protection switch. The feedback circuit is coupled between the synchronous rectification circuit and the control unit to feed back a voltage signal of the output voltage of the synchronous rectification circuit to the control unit. When the control unit judges that the detection voltage of the current detection resistor is smaller than a first threshold value and the output voltage of the synchronous rectification circuit is larger than a second threshold value, the control unit controls the protection switch to be not conducted.

In one embodiment, the output voltage of the synchronous rectification circuit is positively correlated with the output power of the power adapter.

In an embodiment, when the control unit determines that the detected voltage is less than the first threshold and the output voltage of the synchronous rectification circuit is greater than the second threshold for more than a threshold time, the control unit controls the protection switch to be non-conductive.

In one embodiment, the threshold time is 500 milliseconds.

In an embodiment, when the control unit determines that the detection voltage is zero and the output voltage of the synchronous rectification circuit is greater than the second threshold value, the control unit controls the protection switch to be non-conductive.

In an embodiment, the power adapter further includes an adjusting circuit coupled to the feedback circuit and the control unit, wherein the adjusting circuit has rectifying, filtering and voltage dividing functions, and the adjusting circuit adjusts the voltage signal of the output voltage fed back by the feedback circuit to a target voltage level and provides the target voltage level to the control unit.

In one embodiment, the control unit receives the voltage signal of the output voltage fed back by the feedback circuit, and captures a target voltage level of the voltage signal of the output voltage.

In one embodiment, the second threshold is 1.1 volts.

In one embodiment, the power adapter has a universal serial bus power transfer function.

Drawings

FIG. 1 is a schematic diagram of a power adapter according to an embodiment of the disclosure;

FIG. 2 is a schematic circuit diagram of an embodiment of the power adapter of FIG. 1;

FIG. 3 is a schematic circuit diagram of another embodiment of the power adapter of FIG. 1;

FIG. 4 is a flow chart of a control method of a power adapter according to an embodiment of the disclosure;

fig. 5 is a flowchart illustrating a variation of the control method of fig. 4.

[ symbolic description ]

P _O : power supply path

R _CS : current detecting resistor

CON _PD : control unit

Q _P : protective switch

SR: synchronous rectifying circuit

And (B): feedback circuit

T _R : variable pressureDevice for preventing and treating cancer

S _O : output side

V _O : output voltage

V _RCS : detecting voltage

V _TH1 : first threshold value

V _TH2 : second threshold value

T _TH : threshold time

CON _SR : rectifying control unit

Q _SR : synchronous rectification switch

P1: first port

P2: second port

10: adjusting circuit

S11, S12, S13, S14, S15, S16: step (a)

Detailed Description

Some exemplary embodiments that exhibit the features and advantages of the present disclosure are described in detail in the following description. It will be understood that various changes can be made in the above-described embodiments without departing from the scope of the utility model, and that the description and illustrations are intended to be by way of illustration only and not to be limiting.

Referring to fig. 1, fig. 1 is a schematic circuit architecture diagram of a power adapter according to an embodiment of the disclosure. The power adapter with power source limiting capability comprises a power path P _O Current detecting resistor R _CS Control unit CON _PD Protection switch Q _P The synchronous rectification circuit SR and the feedback circuit FB. Power supply path P _O Is coupled to the transformer T _R With the output side S of the power adapter _O Between them. As shown in fig. 1, a power supply path P _O Is composed of a transformer T _R To the output side S of the power adapter _O A path for transmitting power in the direction. In some embodiments, the power adapter has USB PD function, and correspondingly, the control unit CON _PD The system is a power transmission (PD) controller, and the functions of communication, feedback control, protection control and the like of the system can be realized through a control unit CON _PD Realizing the method.

Current detection resistor R _CS Coupled to the power path P _O . Control unit CON _PD Coupled current detecting resistor R _CS . Protection switch Q _P Coupled to the power path P _O And is used for providing a protective circuit breaking function. Control unit CON _PD By controlling the protection switch Q _P Whether or not to turn on determines whether or not the power adapter outputs power, specifically, the protection switch Q _P When conducting, the power adapter is at the output side S _O Output power, conversely, protection switch Q _P When the power adapter is not conducted, the power adapter does not output power.

The synchronous rectification circuit SR is coupled to the transformer T _R Protection switch Q _P And is used for the transformer T _R Providing an output voltage V after synchronous rectification of the voltage on the secondary side of (2) _O To power supply path P _O . The feedback circuit FB is coupled to the synchronous rectification circuit SR and the control unit CON _PD To output voltage V of synchronous rectification circuit SR _O Voltage signal (i.e. reflecting output voltage V _O Voltage signal of (a) is fed back to the control unit CON _PD Causing the control unit CON to _PD Knowing the output voltage V of the synchronous rectification circuit SR by the voltage signal _O . Control unit CON _PD According to the output voltage V of the synchronous rectification circuit SR _O And a current detecting resistor R _CS Is a detection voltage V of (1) _RCS Decision control protection switch Q _P Conducting or non-conducting.

Specifically, in the control unit CON _PD Judging current detecting resistor R _CS Is a detection voltage V of (1) _RCS Less than a first threshold V _TH1 And the output voltage V of the synchronous rectification circuit SR _O Greater than a second threshold V _TH2 At this time, the control unit CON _PD Control protection switch Q _P Non-conduction, so that the power adapter does not output power, wherein the second threshold V _TH2 May be, for example, but not limited to, 1.1 volts. Due to the detection voltage V _RCS For flowing through the current detecting resistor R _CS Current and current detecting resistor R _CS So that when the current detecting resistor R is _CS When the resistance value is a fixed value, the voltage V is detected _RCS Can reflect the current flowing through the detecting circuitR resistance _CS The magnitude of the current, i.e. the detection voltage V _RCS The larger the current is, the more the current is detected by the resistor R _CS The larger the current of (2), the conversely, the detection voltage V _RCS The smaller the current flowing through the current detecting resistor R _CS The smaller the current of (2). Therefore, when detecting the voltage V _RCS Less than a preset first threshold V _TH1 In this case, it may be represented that the power adapter does not output current to the load terminal or the current detection resistor R _CS An anomaly occurs in the associated circuitry of (e.g., a short circuit occurs or the power adapter is being under short circuit protection test or LPS test).

Furthermore, due to the output voltage V of the synchronous rectification circuit SR _O The magnitude of (a) is positively correlated with the output power (output load) of the power adapter, i.e. the output voltage V of the synchronous rectification circuit SR _O The larger the output power of the power adapter is, the larger; output voltage V of synchronous rectification circuit SR _O The smaller the output power of the power adapter is. Thus, the control unit CON _PD Judging current detecting resistor R _CS Is a detection voltage V of (1) _RCS Whether or not it is smaller than a first threshold value V _TH1 And simultaneously judge the output voltage V of the synchronous rectification circuit SR _O Whether or not it is greater than a second threshold value V _TH2 And when the two judging results are yes, the current detecting resistor R is obtained _CS May be shorted but the power adapter still continues to output current to the output side S _O (load), i.e. the power adapter may be in a short-circuit protection test or an LPS test, when the control unit CON _PD Immediate control protection switch Q _P Is non-conductive so that the power adapter does not output power.

In some embodiments, the control unit CON _PD The duration for which the determination condition is satisfied is also considered in making the foregoing determination. Specifically, in the control unit CON _PD Judging the detected voltage V _RCS Less than a first threshold V _TH1 And the output voltage V of the synchronous rectification circuit SR _O Greater than a second threshold V _TH2 For exceeding a threshold time T _TH At this time, the control unit CON _PD Control protection switch Q _P Is non-conductive so that the power adapter does not output power. Threshold valueTime T _TH May be, for example, but not limited to, 500 milliseconds. By considering the duration of the establishment of the judgment conditions, the establishment of the two voltage judgment conditions due to the abnormal (unexpected) operation of the transient or instantaneous circuit can be avoided, and the false triggering of the control protection switch Q _P A non-conductive protection mechanism.

Furthermore, in other embodiments, the control unit CON _PD Can be changed to judge the detected voltage V _RCS Whether equal to 0 volt replaces the detection voltage V _RCS Whether or not it is smaller than a first threshold value V _TH1 . In this case, in the control unit CON _PD Judging the detected voltage V _RCS Output voltage V of synchronous rectification circuit SR equal to 0V _O Greater than a second threshold V _TH2 At this time, the control unit CON _PD Control protection switch Q _P Is non-conductive so that the power adapter does not output power.

Referring to fig. 2, fig. 2 is a schematic circuit diagram of an embodiment of the power adapter of fig. 1. As shown in fig. 2, the synchronous rectification circuit SR is subjected to its rectification control unit CON _SR Control to drive the transformer T _R Is rectified to an output voltage V _O It should be noted that the synchronous rectification circuit SR may adopt a corresponding topology according to practical requirements, and is not limited to the embodiment illustrated in fig. 2. In addition, the synchronous rectification switch Q of the synchronous rectification circuit SR _SR The installation position of the switch is not limited to the high-side (high-side) of the secondary side shown in fig. 2, but can be also arranged at the low-side (low-side) of the secondary side, so that no matter the synchronous rectification switch Q _SR The power adapter is applicable to the power adapter disposed on the high side or the low side of the secondary side.

The first port P1 and the second port P2 of the feedback circuit FB are respectively coupled to the output end of the synchronous rectification circuit SR and the control unit CON _PD The first port P1 receives the output voltage V of the synchronous rectification circuit SR _O And then output voltage V _O The voltage signal of (1) is transmitted through the feedback circuit FB and then provided to the control unit CON through the second port P2 _PD . It should be noted that the feedback circuit FB can adopt a corresponding topology according to actual requirements withoutIs limited to the aspect illustrated in fig. 2.

In addition, in the embodiment shown in fig. 2, the second port P2 of the feedback circuit FB is directly connected to the control unit CON _PD Control unit CON _PD Directly receiving the output voltage V fed back by the feedback circuit FB _O And extract the output voltage V _O For determining and operating the target voltage level of the voltage signal. In this case, the control unit CON _PD Such as, but not limited to, a relatively powerful Microcontroller (MCU).

In other embodiments, as shown in FIG. 3, the power adapter further includes a conditioning circuit 10. The adjusting circuit 10 is coupled to the second port P2 of the feedback circuit FB and the control unit CON _PD And has rectifying, filtering and voltage dividing functions, wherein the regulating circuit 10 outputs the output voltage V from the second port P2 of the feedback circuit FB _O Is adapted to the control unit CON _PD The voltage level of the operation and provides the adjusted voltage level to the control unit CON _PD . It should be noted that the adjusting circuit 10 may adopt a corresponding topology according to actual requirements, and is not limited to the embodiment illustrated in fig. 3.

Referring to fig. 4, fig. 4 is a flow chart of a control method of a power adapter according to an embodiment of the present disclosure, and the control method shown in fig. 4 is applicable to the power adapter of the foregoing embodiments. As shown in fig. 4, the control method of the power adapter includes the following steps. First, when the power adapter is in the loaded normal operation (step S11), the current detection resistor R is compared _CS Is a detection voltage V of (1) _RCS And a first threshold V _TH1 (step S12) and compares the output voltage V of the synchronous rectification circuit SR _O And a second threshold V _TH2 (step S13). Then, judging whether to detect the voltage V _RCS Less than a first threshold V _TH1 And the output voltage V of the synchronous rectification circuit SR _O Greater than a second threshold V _TH2 (step S14). If the determination result in step S14 is yes, the voltage V is detected _RCS Less than a first threshold V _TH1 And the output voltage V of the synchronous rectification circuit SR _O Greater than a second threshold V _TH2 Then control and protectSwitch Q _P Non-conduction (step S15); otherwise, if the determination result in step S14 is no, steps S12 and S13 are executed again.

In some embodiments, when the determination condition of step S14 is satisfied (i.e., the determination result is yes), the duration for which the determination condition is satisfied is further considered. In this case, as shown in fig. 5, the control method of the power adapter further includes a step S16, and when the determination result of the step S14 is yes, the step S16 is executed to determine the detection voltage V _RCS Less than a first threshold V _TH1 And the output voltage V of the synchronous rectification circuit SR _O Greater than a second threshold V _TH2 Whether or not to last beyond the threshold time T _TH . If the determination result in step S16 is yes, the voltage V is detected _RCS Less than a first threshold V _TH1 And the output voltage V of the synchronous rectification circuit SR _O For exceeding a threshold time T _TH Step S15 is performed to control the protection switch Q _P Non-conduction; otherwise, if the determination in step S16 is negative, the voltage V is detected _RCS Less than a first threshold V _TH1 And the output voltage V of the synchronous rectification circuit SR _O Does not last beyond the threshold time T _TH Steps S12 and S13 are executed again. In this embodiment, when the determination results of steps S14 and S16 are both yes, step S15 is performed to control the protection switch Q _P And is not conducted, and if the judgment result of any one of the steps S14 and S16 is negative, the steps S12 and S13 are executed again.

In summary, the present disclosure provides a power adapter, which performs judgment and control based on an output voltage of a synchronous rectification circuit in the power adapter, so as to simplify a circuit design, and thereby achieve precise limitation and protection of an output power of the power adapter, so that the power adapter with a larger output power meets a specification of an LPS standard.

It should be noted that the foregoing description of the preferred embodiments is provided for illustration only, and the scope of the present utility model is not limited to the embodiments described herein, but is defined by the claims. And that the present utility model may be modified in various ways by those skilled in the art without departing from the scope of the claims.

Claims

1. A power adapter, comprising:

a power path coupled between a transformer and an output side of the power adapter;

a current detecting resistor coupled to the power path;

a control unit coupled to the current detection resistor;

a protection switch coupled to the power path;

the synchronous rectification circuit is coupled with the transformer and the protection switch; and

a feedback circuit coupled between the synchronous rectification circuit and the control unit for feeding back the voltage signal of the output voltage of the synchronous rectification circuit to the control unit;

when the control unit judges that a detection voltage of the current detection resistor is smaller than a first threshold value and the output voltage of the synchronous rectification circuit is larger than a second threshold value, the control unit controls the protection switch to be not conducted.

2. The power adapter of claim 1 wherein the output voltage of the synchronous rectification circuit is positively correlated with the output power of the power adapter.

3. The power adapter of claim 1, wherein the control unit controls the protection switch to be non-conductive when the control unit determines that the detected voltage is less than the first threshold and the output voltage of the synchronous rectification circuit is greater than the second threshold for more than a threshold time.

4. A power adapter as claimed in claim 3, characterized in that the threshold time is 500 milliseconds.

5. The power adapter of claim 1, wherein the control unit controls the protection switch to be non-conductive when the control unit determines that the detection voltage is zero and the output voltage of the synchronous rectification circuit is greater than the second threshold.

6. The power adapter of claim 1, further comprising an adjusting circuit coupled to the feedback circuit and the control unit, wherein the adjusting circuit has rectifying, filtering and voltage dividing functions, and the adjusting circuit adjusts the voltage signal of the output voltage fed back by the feedback circuit to a target voltage level and provides the target voltage level to the control unit.

7. The power adapter of claim 1, wherein the control unit receives the voltage signal of the output voltage fed back by the feedback circuit and captures a target voltage level of the voltage signal of the output voltage.

8. The power adapter of claim 1 wherein the second threshold is 1.1 volts.

9. The power adapter of claim 1 wherein the power adapter has a universal serial bus power transfer function.