Power adapter with limited power source capability and control method thereof

Abstract

A power adapter with limited power source capability and a control method thereof. The power adapter includes a power path, a current detection resistor, a control unit, and a protection switch. The power path is coupled between a 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 detection resistor. The protection switch is coupled to the power path. When the control unit determines that a detection voltage of the current detection resistor is less than a first threshold value and a level signal voltage of the control unit is greater than a second threshold value, the control unit controls the protection switch to be non-conductive.

Description

Technical Field

[0001] This invention relates to a power adapter and its control method, and more particularly to a power adapter with limited power source capability and its control method. Background Technology

[0002] The information technology equipment safety standard IEC / EN / UL 60950-1-2 specifies limited power sources (LPS) for power supplies, power adapters, and other power-related products. Under this standard, information technology equipment must have a fire-resistant enclosure. However, if the main circuit of the equipment is powered by an LPS, meaning the voltage, current, and energy in the circuit all meet or fall below the values ​​specified in Table 2B of UL 60950-1-2, then in the event of a hazard, the equipment does not need a high-fire-resistant enclosure as a hazard mitigation measure. In other words, an enclosure material with an HB flammability rating as specified in UL 94 can be used. HB-rated enclosure materials are not only inexpensive but also possess superior physical properties and easily meet environmental requirements. Furthermore, this requirement (specification) also applies to power adapters with Universal Serial Bus Power Delivery (USB PD) functionality.

[0003] To meet the LPS standard requirements, power adapters can be classified in two ways: inherently limited power sources and non-inherently limited power sources. In short, to comply with the LPS standard, power supplies with inherently limited power sources must not exceed 8A / 100VA in output; for non-inherently limited power sources, the current rating of their current limiting protection device (e.g., fuse) should not exceed 5A. If no current limiting protection device is used at the output, for systems with an output voltage less than 30V, the output current during a single fault test at 20V must not exceed 5A, and the total output power must not exceed 100VA. Exceeding these current or power limits requires activation of a protection mechanism, which can be current limiting or shutdown, typically through latch-off or autorecovery, and the total output power must not exceed 100VA.

[0004] However, with the development of consumer electronics and the increasing demand for power, the rated normal output current or output power of power adapters with large output power capabilities (such as 90-96W) may be very close to the limits specified by the LPS standard (8A or 100VA). If the output power limit of the LPS standard is to be met, and current limiting protection devices are not installed on the output side to reduce costs, then overcurrent (OCP) or overpower (OPP) protection points may be too close to the rated output, making design difficult. Furthermore, during mass production, the protection points of products may vary due to the inherent errors of the components used, leading to quality issues such as the protection being prone to false triggering in some products. Therefore, power adapters with such large output power generally find it difficult to meet the LPS standard specifications and obtain certification.

[0005] Therefore, how to design a power adapter with power limiting capability and its control method, by obtaining the node voltage related to the output power (output load) of the power adapter for judgment and control, to simplify circuit design, and to achieve accurate limitation and protection of the output power of the power adapter with large output power to meet the standard specifications, is an important research topic of the inventors of this disclosure. Summary of the Invention

[0006] The purpose of this invention is to provide a power adapter with limited power source capability, thereby solving the problems of the prior art.

[0007] To achieve the aforementioned objectives, the power adapter with limited power source capability proposed in this invention includes a power path, a current sensing resistor, a control unit, and a protection switch. The power path is coupled between the transformer and the output side of the power adapter. The current sensing resistor is coupled to the power path. The control unit is coupled to the current sensing resistor. The protection switch is coupled to the power path. When the control unit determines that the voltage detected by the current sensing resistor is less than a first threshold and the voltage level signal of the control unit is greater than a second threshold, the control unit controls the protection switch to remain closed.

[0008] In one embodiment, when the control unit determines that the detected voltage is less than a first threshold and the voltage level signal is greater than a second threshold for a period of time exceeding the threshold, the control unit controls the protection switch to not conduct.

[0009] In one embodiment, when the detection voltage is equal to 0 volts and the level signal voltage is greater than a second threshold, the control unit controls the protection switch to not conduct.

[0010] In one embodiment, the power adapter with limited power source capability further includes a synchronous rectification circuit. The synchronous rectification circuit is coupled to a transformer and a protective switch. The level signal voltage is the node voltage of the synchronous rectification circuit.

[0011] In one embodiment, the synchronous rectification circuit includes a rectification control unit, a switch, and a capacitor. The rectification control unit is coupled to a first terminal on the secondary side of the transformer and a protective switch. The switch is coupled to the first terminal, the rectification control unit, and the protective switch, or coupled to a second terminal on the secondary side and the rectification control unit. The capacitor is coupled to the first terminal and the rectification control unit.

[0012] In one embodiment, the level signal voltage is the node voltage where the capacitor and the first terminal are connected together.

[0013] In one embodiment, the level signal voltage is the node voltage shared by the capacitor and the rectifier control unit.

[0014] In one embodiment, the second threshold is 1.1 volts.

[0015] In one embodiment, the threshold time is 500 milliseconds.

[0016] In one embodiment, the power adapter has a power transmission function.

[0017] By using the proposed power adapter with limited power source capability, and by obtaining the node voltage related to the power adapter's output power (output load) for judgment and control, circuit design can be simplified, and precise limitation and protection of the power adapter's output power, which is close to the regulatory limit, can be achieved to comply with the LPS standard specifications.

[0018] Another objective of this invention is to provide a control method for a power adapter with limited power source capability, thereby solving the problems of the prior art.

[0019] To achieve the aforementioned objectives, the present invention proposes a control method for a power adapter with limited power source capability. The power adapter provides a power path between its output side and a transformer. The power adapter includes a current sensing resistor coupled to the power path, a control unit, and a protection switch. The control method includes: under normal on-load operation, comparing the detection voltage of the current sensing resistor with a first threshold; comparing the level signal voltage of the control unit with a second threshold; and controlling the protection switch to not conduct when the detection voltage is less than the first threshold and the level signal voltage is greater than the second threshold.

[0020] In one embodiment, before controlling the protection switch to not conduct, the method further includes: determining whether the detection voltage is less than a first threshold and the level signal voltage is greater than a second threshold for a period of time; and if the detection voltage is less than a first threshold and the level signal voltage is greater than a second threshold for a period of time, controlling the protection switch to not conduct.

[0021] In one embodiment, when the detection voltage is equal to 0 volts and the level signal voltage is greater than a second threshold, the control protection switch is not turned on.

[0022] In one embodiment, the second threshold is 1.1 volts.

[0023] In one embodiment, the threshold time is 500 milliseconds.

[0024] The proposed control method for a power adapter with limited power source capability simplifies circuit design by using node voltages related to the power adapter's output power (output load) for judgment and control. It also enables precise limiting and protection of the output power of power adapters with large output power that is close to regulatory limits, in order to comply with LPS standard specifications.

[0025] To gain a deeper understanding of the techniques, means, and effects employed by this invention to achieve its intended purpose, please refer to the following detailed description and accompanying drawings. It is believed that the purpose, features, and characteristics of this invention can be understood in a thorough and specific manner from these drawings. However, the drawings are provided for reference and illustration only and are not intended to limit the scope of this invention. Attached Figure Description

[0026] Figure 1 : This is a circuit block diagram of the power adapter with limited power source capability of the present invention.

[0027] Figure 2 : This is a circuit diagram of one embodiment of the power adapter with limited power source capability of the present invention.

[0028] Figure 3 This is a flowchart of the first embodiment of the control method for a power adapter with limited power source capability according to the present invention.

[0029] Figure 4 : This is a flowchart of a second embodiment of the control method for a power adapter with limited power source capability according to the present invention.

[0030] The reference numerals in the attached figures are explained as follows:

[0031] P O Power path

[0032] R CS Current sensing resistor

[0033] CON PD Control Unit

[0034] Q P : Protective switch

[0035] T R :transformer

[0036] SR: Synchronous Rectifier Circuit

[0037] So: Output side

[0038] 10: Adjusting the circuit

[0039] CON SR : Rectifier control unit

[0040] Q SR :switch

[0041] C SR :capacitance

[0042] P1: First node

[0043] P2: Second node

[0044] V RCS Detection voltage

[0045] V IC1 Level signal voltage

[0046] V TH1 First threshold

[0047] V TH2 Second threshold

[0048] T TH Threshold time

[0049] S11~S15: Steps Detailed Implementation

[0050] The technical content and detailed description of the present invention are explained below with reference to the accompanying drawings.

[0051] Please see Figure 1 The diagram shown is a circuit block diagram of a power adapter with limited power source capability according to the present invention. The power adapter with limited power source capability includes a power path P. O Current sensing resistor R CS Control Unit CON PD and protection switch Q P Power path P O Coupled to transformer T R Between the power adapter's output side So. For example... Figure 1 As shown, the power path P O It is made by transformer T R The path for transmitting (sending) power from the secondary side to the output side So of the power adapter. In this invention, the power adapter may have Universal Serial Bus Power Delivery (USB PD) functionality. Therefore, if the power adapter has power delivery (PD) functionality, the control unit CON... PD This is a power transmission (PD) controller. The system's communication, feedback control, protection control, and other functions can all be handled by the control unit CON. PD accomplish.

[0052] Current sensing resistor R CS Coupled power path P O Control Unit CON PD Coupling current sensing resistor R CS Protection switch Q P Coupled power path P O This is used to provide a circuit-breaking function for protection. Specifically, it involves controlling the protection switch Q. P Whether the protection switch Q is on or off determines whether the power adapter outputs power. That is, when the protection switch Q is off... P When the circuit is on, the power adapter can output power on the output side So; conversely, when the protection switch Q is off... P When not conducting, the power adapter does not output power.

[0053] Specifically, the control unit CON PD Determine the current sensing resistor R CS Detection voltage V RCS Less than the first threshold V TH1 And the control unit CON PD Level signal voltage V IC1 Greater than the second threshold V TH2 At that time, control protection switch Q P The circuit is not conductive, preventing the power adapter from outputting power. The second threshold V... TH2 For example, but not limited to, 1.1 volts. Wherein, the detection voltage V RCS For current sensing resistor R CS The current and the current sensing resistor R CS The product of , therefore, when the current sensing resistor R CS When the value is constant, the detection voltage V RCS This can represent the current sensing resistor R flowing through. CS The magnitude of the current, i.e., the detection voltage V. RCS The larger the value, the more current flows through the current sensing resistor R. CS The larger the current; the higher the detection voltage V RCS The smaller the value, the more current flows through the current sensing resistor R. CS The smaller the current, the better. Therefore, when the detection voltage V... RCS Less than the preset first threshold V TH1 This could indicate that the power adapter is not currently outputting current to the load, or that the current sensing resistor R is faulty. CS The relevant circuitry malfunctions (e.g., a short circuit occurs, or the power adapter is undergoing short circuit protection testing or LPS testing).

[0054] Furthermore, due to the voltage V of the level signal IC1 The magnitude is related to the output power (output load) of the power adapter, i.e., the voltage level signal V. IC1The larger the value, the greater the output power of the power adapter; voltage level (V) IC1 The smaller the value, the lower the output power of the power adapter. Therefore, by simultaneously judging the current sensing resistor R... CS Detection voltage V RCS (Is it less than the first threshold V?) TH1 ) and control unit CON PD Level signal voltage V IC1 (Is it greater than the second threshold V?) TH2 Furthermore, when both conditions are met, the current sensing resistor R of the current power adapter is determined. CS It may be short-circuited but still continue to output current to the load, meaning the power adapter may be under short-circuit protection testing or LPS testing. In this case, the control unit CON... PD Immediately control the protection switch Q P The circuit is not conductive, so the power adapter does not output power.

[0055] In another embodiment of the present invention, the detection voltage V is determined. RCS Less than the first threshold V TH1 It can be used to determine the detection voltage V RCS It equals 0 volts. Therefore, when the detection voltage V... RCS Equal to 0 volts and level signal voltage V IC1 Greater than the second threshold V TH2 At that time, control protection switch Q P The circuit is not conductive, so the power adapter does not output power.

[0056] Another embodiment of the present invention further includes determining a time condition, namely, the control unit CON. PD Determine the detection voltage V RCS Less than the first threshold V TH1 And the level signal voltage V IC1 Greater than the second threshold V TH2 For a period of time T that exceeds the threshold TH At that time, control protection switch Q P The circuit is not conducting, preventing the power adapter from outputting power. The threshold time T... TH For example, but not limited to 500 milliseconds. Therefore, the timing judgment condition can prevent the aforementioned two voltage judgment conditions from being met due to transient or instantaneous abnormal (unexpected) circuit operation, thus avoiding the false triggering of the protection switch Q. P Non-conductive protection mechanism.

[0057] like Figure 1 As shown, the power adapter with limited power source capability also includes a synchronous rectification circuit SR. The synchronous rectification circuit SR is coupled to a transformer T. R With protective switch Q PLevel signal voltage V IC1 This is the node voltage of the synchronous rectifier circuit SR.

[0058] Please see Figure 2 The diagram shown is a circuit diagram of one embodiment of the power adapter with limited power source capability of the present invention. The synchronous rectification circuit SR includes a rectification control unit, a switch, and a capacitor. The synchronous rectification circuit SR is used to rectify AC voltage into DC voltage for use at the system output. The rectification control unit CON... SR Coupler transformer T R The non-grounded terminal on the secondary side and the protective switch Q P Switch Q SR Coupled to the ungrounded terminal, rectifier control unit CON SR and protection switch Q P Capacitor C SR The ungrounded terminal is coupled to the rectifier control unit CON. SR .

[0059] In one embodiment, the level signal voltage V IC1 For switch Q SR Capacitor C SR And the node voltage shared by the non-grounded terminals, i.e. Figure 2 The node voltage of the first node P1 is indicated. Therefore, by determining the detected voltage V... RCS Less than the first threshold V TH1 And the level signal voltage V IC1 (i.e., the node voltage of the first node P1) is greater than the second threshold V. TH2 At that time, control protection switch Q P The circuit is not conducting, preventing the power adapter from outputting power. Specifically, the node voltage of the first node P1 is adjusted by the regulating circuit 10, which has rectification and voltage division functions, to a level suitable for the control unit CON. PD The operating voltage level, therefore, the adjusted voltage level is provided to the control unit CON. PD For example, control unit CON PD The first pin (e.g.) Figure 1 (As shown).

[0060] In one embodiment, the level signal voltage V IC1 For capacitor C SR With rectifier control unit CON SR Common node voltage, i.e. Figure 2 The node voltage of the second node P2 is indicated. Therefore, by determining the detected voltage V... RCS Less than the first threshold V TH1 And the level signal voltage V IC1 (That is, the node voltage of the second node P2) is greater than the second threshold V. TH2At that time, control protection switch Q P The circuit is not conducting, preventing the power adapter from outputting power. Specifically, the node voltage of the second node P2 is adjusted by the regulating circuit 10, which has rectification and voltage division functions, to a level suitable for the control unit CON. PD The operating voltage level, therefore, the adjusted voltage level is provided to the control unit CON. PD For example, control unit CON PD The first pin (e.g.) Figure 1 (As shown).

[0061] However, this invention does not limit the node voltage of the first node P1 and the node voltage of the second node P2 for power supply detection to be used as the level signal voltage V. IC1 A judgment is made. The node voltage detected at each node in the synchronous rectifier circuit SR can be used as the level signal voltage V. IC1 Make a judgment.

[0062] It is worth mentioning that the synchronous rectifier switch Q of the synchronous rectifier circuit SR SR The configurable location is not limited to Figure 2 The high-side (current output side) of the secondary side shown can also be configured on the low-side (current return side) of the secondary side. Therefore, regardless of the synchronous rectifier switch Q... SR Whether configured on the high side or the low side, it is applicable to the judgment and control method of the present invention.

[0063] Please see Figure 3 The diagram shown is a flowchart of a first embodiment of the control method for a power adapter with limited power source capability according to the present invention. The output side So of the power adapter is connected to the transformer T. R Provides a power path P between them O The power adapter includes components coupled to the power path P. O Current sensing resistor R CS Control Unit CON PD and protection switch Q P The control method includes the following steps: First, under normal on-load operation (S11), the current sensing resistor R is compared. CS Detection voltage V RCS With the first threshold V TH1 (S12). Then, compare the control unit CON. PD Level signal voltage V IC1 With the second threshold V TH2 (S13). Then, determine whether the detection voltage is less than the first threshold V. TH1 And the level signal voltage V IC1 Greater than the second threshold V TH2 (S14). When the detected voltage VRCS Less than the first threshold V TH1 And the level signal voltage V IC1 Greater than the second threshold V TH2 At that time, control protection switch Q P Non-conductive (S15).

[0064] In another embodiment of the present invention, the detection voltage V is determined. RCS Less than the first threshold V TH1 It can be used to determine the detection voltage V RCS It equals 0 volts. Therefore, in step (S15), when the detected voltage V... RCS Equal to 0 volts and level signal voltage V IC1 Greater than the second threshold V TH2 At that time, control protection switch Q P The circuit is not conductive, so the power adapter does not output power.

[0065] Please see Figure 4 The diagram shown is a flowchart of a second embodiment of the control method for a power adapter with limited power source capability according to the present invention. Figure 4 and Figure 3 The biggest difference is that step (S14) includes a time condition for judgment, namely, judging the detection voltage V. RCS Less than the first threshold V TH1 And the level signal voltage V IC1 Greater than the second threshold V TH2 Does it continue for more than the threshold time T? TH (S14'). If both of the aforementioned voltage judgment conditions are met (i.e., the judgment result of step (S14') is "yes"), then control the protection switch Q. P If the circuit is not turned on (S15), the power adapter will not output power. Conversely, if either of the two voltage judgment conditions mentioned above is not met (i.e., the judgment result of step (S14') is "no"), then return to step (S12) and re-execute the comparison and detection of voltage V. RCS With the first threshold V TH1 (S12), and perform comparison level signal voltage V IC1 With the second threshold V TH2 (S13).

[0066] In summary, the present invention has the following features and advantages: by obtaining the node voltage of the synchronous rectification circuit related to the output power (output load) of the power adapter as a basis for judgment and control, the circuit design can be simplified, and even when the output power of the power adapter is large and very close to the LPS standard limit, the output power of the power adapter with large output power can be accurately limited and protected to comply with the LPS standard specification.

[0067] The above description is merely a detailed explanation and accompanying drawings of preferred embodiments of the present invention, and the features of the present invention are not limited thereto, nor are they intended to limit the present invention. The entire scope of the present invention should be determined by the following claims. All embodiments that conform to the spirit of the claims of the present invention and similar variations thereof should be included in the scope of the present invention. Any variations or modifications that can be easily conceived by those skilled in the art within the field of the present invention can be covered by the following claims of the present disclosure.

Claims

1. A power adapter with limited power source capability, comprising: a power path coupled between a transformer and an output side of the power adapter; a current detection resistor coupled to the power path; a control unit coupled to the current detection resistor; a protection switch coupled to the power path; and a synchronous rectification circuit coupled to the transformer and the protection switch, the synchronous rectification circuit comprising: a rectification control unit coupled to a first terminal of a secondary side of the transformer and the protection switch; a switch coupled to the first terminal, the rectification control unit, and the protection switch or coupled to a second terminal of the secondary side and the rectification control unit; and a capacitor coupled to the first terminal and the rectification control unit, wherein the control unit controls the protection switch to be non-conductive when a detection voltage of the current detection resistor is less than a first threshold and a level signal voltage of the control unit is greater than a second threshold, wherein the level signal voltage is a node voltage of the synchronous rectification circuit, and the level signal voltage is positively related to an output power of the power adapter. the control unit controls the protection switch to be non-conductive when the detection voltage is less than the first threshold and the level signal voltage is greater than the second threshold for more than a threshold time. the control unit controls the protection switch to be non-conductive when the detection voltage is equal to 0 volt and the level signal voltage is greater than the second threshold.

2. The power adapter with limited power source capability of claim 1, wherein, the level signal voltage is the node voltage shared by the capacitor and the first terminal.

3. The power adapter with limited power source capability of claim 1, wherein, the level signal voltage is the node voltage shared by the capacitor and the rectification control unit.

4. The power adapter with limited power source capability of claim 1, wherein, the second threshold is 1.1 volt.

5. The power adapter with limited power source capability of claim 1, wherein, the threshold time is 500 milliseconds.

6. The power adapter with limited power source capability of claim 1, wherein, the power adapter has a universal serial bus power delivery function.

7. The power adapter with limited power source capability of claim 2, wherein, the power adapter comprises a current detection resistor, a control unit, and a protection switch coupled to a power path, the power adapter further comprises a synchronous rectification circuit coupled to the transformer and the protection switch, the synchronous rectification circuit comprising: a rectification control unit coupled to a first terminal of a secondary side of the transformer and the protection switch; a switch coupled to the first terminal, the rectification control unit, and the protection switch or coupled to a second terminal of the secondary side and the rectification control unit; and a capacitor coupled to the first terminal and the rectification control unit, 8. The power adapter with limited power source capability of claim 1, wherein, the control method comprises:

9. A control method of a power adapter having a limited power source capability, the power adapter providing a power path between an output side of the power adapter and a transformer, wherein, comparing a detection voltage of the current detection resistor with a first threshold in a normal operation with load; comparing a level signal voltage of the control unit with a second threshold; and controlling the protection switch to be non-conductive when the detection voltage is less than the first threshold and the level signal voltage is greater than the second threshold, wherein the level signal voltage is a node voltage of the synchronous rectification circuit, and the level signal voltage is positively related to an output power of the power adapter. before controlling the protection switch to be non-conductive, further comprising: determining whether the detection voltage is less than the first threshold and the level signal voltage is greater than the second threshold for more than a threshold time; and controlling the protection switch to be non-conductive if the detection voltage is less than the first threshold and the level signal voltage is greater than the second threshold for more than the threshold time. ​ 10. The control method of a power adapter having a limited power source capability as claimed in claim 9, wherein, ​ ​ ​ 11. The control method of a power adapter having a limited power source capability as claimed in claim 9, wherein, when the detection voltage is equal to 0 volts and the level signal voltage is greater than the second threshold, controlling the protection switch to be non-conductive.

12. The control method of a power adapter having a limited power source capability as claimed in claim 9, wherein, The second threshold is 1.1 volts.

13. The control method of a power adapter having a limited power source capability as claimed in claim 10, wherein, The threshold time is 500 milliseconds.

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