Power supply and overpower protection value adjusting method thereof

Abstract

The invention discloses a power supply, which provides an output voltage to supply power to a load, and comprises an overpower protection circuit, and the overpower protection circuit comprises a switch, a first resistor and a second resistor. When the output voltage is at the first level, the overpower protection circuit conducts the switch according to the output voltage at the first level so as to provide a first resistance value where the first resistor and the second resistor are connected in parallel, and therefore the overpower protection value of the power converter is adjusted to be a first value. When the output voltage is at the second level, the overpower protection circuit turns off the switch according to the output voltage at the second level to provide a second resistance value of the second resistor, so that the overpower protection value is adjusted to be a second value.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Taiwan Patent Application No. 112146613 filed on November 30, 2023, which is incorporated herein by reference for all purposes as if fully set forth herein. Technical Field

[0003] The present invention relates to a power supply and an operating method thereof, and in particular to a power supply with over-power protection value adjustment and an over-power protection value adjustment method thereof. Background Art

[0004] In recent years, the problem of global warming has become increasingly serious, especially carbon emissions have attracted widespread attention. In order to reduce the adverse impact on the environment, energy saving has become a key issue. In this case, the power loss limit of power supplies for electronic products has become more stringent.

[0005] Among them, the power supply generally adjusts the working state according to the demand of the load coupled at the back end, which can be simply divided into normal working state and standby state. Taking the back end load as a printer as an example, the printer is in standby state for most of the time, and it still consumes power continuously in standby state. Therefore, in recent years, the power consumption requirements for electronic products when they are in standby mode have become more and more stringent. In order to ensure that the power supply can minimize power consumption in standby mode, the system can usually provide one or more sets of drive signals to instruct the power supply to adjust the output voltage to the minimum voltage required for the system standby or sleep mode. When the power supply adjusts the output voltage, it can also significantly reduce the operating voltage and operating frequency of the internal controller of the power supply, thereby reducing the power consumption of the controller and the energy loss of the switching components.

[0006] However, after the output voltage of a conventional power supply is reduced, its over-power protection value is usually not adjusted at the same time, which will inevitably cause the problem of over-power protection failure. For example, when the power supply is operating in normal working mode, its output voltage is 24V. At this time, if the maximum value of the output current is set to 4A, the over-power protection value is 96W, and when the output exceeds this value, the power supply will perform over-power protection. However, under the same conditions, and when the power supply is operating in standby mode, the output voltage is 5V. At this time, if the over-power protection value is not adjusted accordingly, then under the output voltage condition of 5V, the output current when entering the over-power protection will be as high as 19.2A. In this way, the entire system is bound to withstand such a high current and is prone to system overheating, internal electronic components burning, and even burning.

[0007] Therefore, how to design a power supply and a method for adjusting the over-power protection value thereof, so as to correspondingly adjust the output over-power protection value under output voltages of different levels to comply with the relevant specifications of a limited power source is a major topic that the present applicant desires to research. Summary of the Invention

[0008] To solve the above problems, the present invention provides a power supply to overcome the problems of the prior art. Therefore, the power supply of the present invention supplies power to a load by providing an output voltage at an output end. The power supply includes an over-power protection circuit, and the over-power protection circuit includes a switch, a first resistor, and a second resistor. The switch includes a first end and a second end. The first end is coupled to a power switch and a controller of the power supply, and the controller sets the over-power protection value of the power supply according to the voltage at the first end. One end of the first resistor is coupled to the second end. One end of the second resistor is coupled to the first end, and the other end is coupled to the other end of the first resistor. Wherein, when the output voltage is at a first level, the over-power protection circuit turns on the switch according to the output voltage at the first level to provide a first resistance value of the first resistor and the second resistor in parallel, thereby adjusting the over-power protection value to a first value; when the output voltage is at a second level less than the first level, the over-power protection circuit turns off the switch according to the output voltage at the second level to provide a second resistance value of the second resistor, thereby adjusting the over-power protection value to a second value.

[0009] To solve the above problems, the present invention further provides a method for adjusting an over-power protection value to overcome the problems of the prior art. Therefore, the method for adjusting the over-power protection value of the present invention is applied to a power supply having a power switch and a controller, and the controller sets the over-power protection value according to a voltage. The method for adjusting the over-power protection value includes the following steps: (a) Turning on a switch connected in series with the power switch according to the output voltage of the power supply being at a first level. (b) Providing a first resistance value according to the turning on of the switch, thereby adjusting the over-power protection value to a first value according to the voltage corresponding to the first resistance value. (c) Turning off the switch according to the output voltage being at a second level. (d) Providing a second resistance value according to the turning off of the switch, thereby adjusting the over-power protection value to a second value according to the voltage corresponding to the second resistance value. Wherein, the first level is greater than the second level, and the first resistance value is less than the second resistance value.

[0010] The main object and effect of the present invention is that the power supply of the present invention can correspondingly adjust the output over-power protection value under output voltages of different levels to comply with the relevant specifications of a limited power source (LPS; Limit Power Source), and is particularly preferably applicable to the output over-power protection having a normal operating mode and a standby mode.

[0011] To further understand the technology, means, and effects adopted by the present invention to achieve the predetermined purpose, please refer to the following detailed description and drawings of the present invention. It is believed that the purpose, features, and characteristics of the present invention can be deeply and specifically understood therefrom. However, the drawings are only for reference and illustration purposes and are not used to limit the present invention. Description of the Drawings

[0012] Figure 1 It is a circuit block diagram of a power supply with an over-power protection value adjustment function according to the present invention;

[0013] Figure 2 Shown is a detailed circuit block diagram of the first embodiment of a power supply with an over-power protection value adjustment function according to the present invention;

[0014] Figure 3A It is a current path diagram when the output voltage of the power supply in the first embodiment of the present invention is at the first level;

[0015] Figure 3B It is a current path diagram when the output voltage of the power supply in the first embodiment of the present invention is at the second level;

[0016] Figure 4 Shown is a detailed circuit block diagram of the second embodiment of a power supply with an over-power protection value adjustment function according to the present invention;

[0017] Figure 5A It is a current path diagram when the output voltage of the power supply in the second embodiment of the present invention is at the first level;

[0018] Figure 5B It is a current path diagram when the output voltage of the power supply in the second embodiment of the present invention is at the second level; and

[0019] Figure 6 It is a method flow chart of an over-power protection value adjustment method applicable to a power supply according to the present invention;

[0020] Wherein, reference numerals:

[0021] 100: Power supply;

[0022] 100-1: Input terminal;

[0023] 100-2: Output terminal;

[0024] 100A: Conversion circuit;

[0025] Q1: Power switch;

[0026] T: Transformer;

[0027] T1: Primary side winding;

[0028] T2: Secondary side winding;

[0029] D1, Co: Filter circuit;

[0030] CL: Controller;

[0031] Pc: Current detection pin;

[0032] 100B: Overpower protection circuit;

[0033] Q2: Switch;

[0034] A: First terminal;

[0035] B: Second terminal;

[0036] C: Control terminal;

[0037] Ra: First resistor;

[0038] Rb: Second resistor;

[0039] Cc: Control circuit;

[0040] OC: Optocoupler;

[0041] OCA: Transmitting end;

[0042] OCB: Receiving end;

[0043] Q3: Detection switch;

[0044] R1: First voltage-dividing resistor;

[0045] R2: Second voltage-dividing resistor;

[0046] Rx, Ry: Current-limiting resistors;

[0047] T3: Auxiliary winding;

[0048] D2: Diode;

[0049] Cb: Energy storage capacitor;

[0050] ZD: Voltage regulation circuit;

[0051] 200: Load;

[0052] Vin: Input voltage;

[0053] Vo: Output voltage;

[0054] V1: First level;

[0055] V2: Second level;

[0056] Va: Voltage;

[0057] Vc: Control voltage;

[0058] Vcc: Operating voltage;

[0059] V3: Third level;

[0060] V4: Fourth level;

[0061] I: Current;

[0062] Sc: Control signal;

[0063] Ss: Detection signal;

[0064] Pp: Over - power protection value. Detailed implementation

[0065] Regarding the technical content and detailed description of the present invention, it is described as follows in conjunction with the accompanying drawings:

[0066] Please refer to Figure 1 is a circuit block diagram of a power supply with an over - power protection value adjustment function according to the present invention. The power supply 100 receives an input voltage Vin from an input terminal 100 - 1, and converts the input voltage Vin into an output voltage Vo, so as to supply the output voltage Vo to a load 200 through an output terminal 100 - 2. The power supply 100 includes a conversion circuit 100A and an over - power protection circuit 100B, and the conversion circuit 100A is coupled to the over - power protection circuit 100B. The conversion circuit 100A is used to convert the input voltage Vin into the output voltage Vo, and the over - power protection circuit 100B is used to perform over - power protection on the conversion circuit 100A. Among them, the main purpose and effect of the present invention is that the power supply 100 of the present invention can adjust the output over - power protection value correspondingly under different levels of the output voltage Vo to meet the relevant specifications of a limited - power source (LPS; Limit Power Source), and is particularly preferably applicable to over - power protection of an output with a normal operating mode and a standby mode.

[0067] As Figure 2 shown is a detailed circuit block diagram of the first embodiment of a power supply with an over - power protection value adjustment function according to the present invention, and also refer to Figure 1. The conversion circuit 100A includes a power switch Q1, a transformer T, a filter circuit D1, Co, and a controller CL. The transformer T includes a primary side winding T1 and a secondary side winding T2, dividing the conversion circuit 100A into a primary side and a secondary side. The power switch Q1 and the input terminal 100-1 are arranged on the primary side and are coupled to the primary side winding T1. The filter circuit D1, Co, and the output terminal 100-2 are arranged on the secondary side and are coupled to the secondary side winding T2. The controller CL is coupled to the power switch Q1 and controls the conversion circuit 100A to convert the input voltage Vin into the output voltage Vo by providing a control signal Sc to control the turn-on and turn-off of the power switch Q1. Among them, the control signal Sc can be a pulse width modulation signal. The controller CL, for example but not limited to, can adjust the pulse width through the feedback of the output voltage Vo to control and stabilize the voltage level of the output voltage Vo.

[0068] On the other hand, in Figure 2 , the input voltage Vin received by the conversion circuit 100A can be a DC voltage, and the DC input voltage Vin is converted into a DC output voltage Vo, but not limited thereto. The conversion circuit 100A can additionally configure a bridge circuit at the input terminal 100-1 to convert the AC input voltage Vin into a DC output voltage Vo. In addition, Figure 2 The conversion circuit 100A of uses the circuit architecture of a flyback converter as a schematic example, but not limited thereto. The applicable types of the conversion circuit 100A will be further described later.

[0069] . The over-power protection circuit 100B includes a switch Q2, a first resistor Ra, and a second resistor Rb. The switch Q2 includes a first terminal A, a second terminal B, and a control terminal C. The first terminal is coupled to the power switch Q1 and the controller CL of the conversion circuit 100A, and the controller CL sets the over-power protection value Pp of the power supply 100 according to the voltage Va at the first terminal A. One end of the first resistor Ra is coupled to the second terminal B, and the other end of the first resistor Ra is coupled to the ground terminal. One end of the second resistor Rb is coupled to the first terminal A, and the other end of the second resistor Rb is coupled to the other end of the first resistor Ra and the ground terminal. Therefore, when the control voltage Vc at the control terminal C controls the switch Q2 to turn off, the over-power protection circuit 100B can provide a larger resistance value, and when the control voltage Vc at the control terminal C can control the switch Q2 to turn on, the over-power protection circuit 100B can provide a smaller resistance value.

[0070] Furthermore, when the power supply 100 has different operating modes such as a normal operating mode and a standby mode, the controller CL can adjust the level of the output voltage Vo according to the different modes. Taking the power supply 100 having a normal operating mode and a standby mode as an example, when the power supply 100 operates in the normal operating mode, the output voltage Vo is at a first level V1 (for example but not limited to, 24V). When the power supply 100 operates in the standby mode, the output voltage Vo is at a second level V2 (for example but not limited to, 5V). Generally, the output voltage Vo in the standby mode is less than the output voltage Vo in the normal operating mode, which means that the second level V2 is generally less than the first level V1. When the output voltage Vo is at the first level V1, the over-power protection circuit 100B turns on the switch Q2 according to the output voltage Vo at the first level V1. When the switch Q2 is turned on, the first resistor Ra and the second resistor Rb are in parallel, so as to provide a first resistance value of the parallel connection of the first resistor Ra and the second resistor Rb. Therefore, when the power switch Q1 is turned on, the current I flows from the primary side winding T1 through the first resistor Ra and the second resistor Rb, causing a voltage Va formed by the current I and the first resistance value to be generated at the first terminal A. Therefore, the controller CL can correspondingly adjust the over-power protection value Pp to a first value according to the voltage Va at the first terminal A.

[0071] Conversely, when the output voltage Vo is at the second level V2, the over-power protection circuit 100B turns off the switch Q2 according to the output voltage Vo at the second level V2. When the switch Q2 is turned off, the first resistor Ra and the first terminal A are open-circuited, so as to provide a second resistance value of the second resistor Rb. Therefore, when the power switch Q1 is turned on, the current I flows from the primary side winding T1 through the second resistor Rb, causing a voltage Va formed by the current I and the second resistance value to be generated at the first terminal A. Therefore, the controller CL can correspondingly adjust the over-power protection value Pp to a second value according to the voltage Va at the first terminal A.

[0072] Then, the controller CL detects and judges the output power by detecting the current at a specific point of the conversion circuit 100A from the current detection pin Pc of the controller CL according to whether the over-power protection value Pp is the first value or the second value. Among them, the current detection pin Pc can be coupled to any current detection point of the conversion circuit 100A (such as but not limited to the output terminal 100-2 or the power switch Q1 and other conventional positions) through various current detection circuits and current sensors. Then, the output power of the conversion circuit 100A at present is calculated through the current and voltage, and the current output power is compared with the over-power protection value Pp to judge whether to perform protection. Among them, the over-power protection circuit 100B controls the on / off of the switch Q2 according to the voltage level of the output voltage Vo to adjust the resistance value, which may include various implementation manners and will be further described below.

[0073] In Figure 2In an embodiment, the over-power protection circuit 100B further includes a control circuit Cc. The control circuit Cc is coupled to the output terminal 100-2 and the control terminal C of the switch Q2, and the control circuit Cc receives an external detection signal Ss. The detection signal Ss is mainly used to indicate that the power supply 100 operates in a normal working mode or a standby mode (taking the above situation as an example). When the detection signal Ss indicates that the power supply 100 operates in the normal working mode, it means that the output voltage Vo is at the first level V1. Therefore, the control circuit Cc controls the switch Q2 to turn on to provide a first resistance value of the parallel connection of the first resistor Ra and the second resistor Rb. On the contrary, when the detection signal Ss indicates that the power supply 100 operates in the standby mode, it means that the output voltage Vo is at the second level V2. Therefore, the control circuit Cc controls the switch Q2 to turn off to provide a second resistance value of the second resistor Rb. Among them, the detection signal Ss can be provided by the backend load 200, or the detection signal Ss can also be provided by a device such as the controller CL inside the power supply 100 after judging the operation mode.

[0074] Furthermore, in one embodiment of the control circuit Cc, the control circuit Cc includes an optocoupler OC and a detection switch Q3. The optocoupler OC is coupled to the output terminal 100-2 and the control terminal C of the switch Q2. Among them, the optocoupler OC includes a transmitting end OCA and a receiving end OCB. The transmitting end OCA is coupled to the output terminal 100-2, and the receiving end OCB is coupled to the control terminal C of the switch Q2. The detection switch Q3 is coupled to the transmitting end OCA of the optocoupler OC, and the control terminal of the detection switch Q3 receives the detection signal Ss. It is worth mentioning that in one embodiment, the switch Q2 and the detection switch Q3 are preferably made of metal-oxide-semiconductor field-effect transistors (MOSFETs), but this is not limited thereto. All electronic components that can implement the on / off according to the signal level should be included in the scope of this embodiment.

[0075] Specifically, when the detection signal Ss corresponds to the output voltage Vo at the first level V1 (taking the low-level detection signal Ss as an example here), the control terminal of the detection switch Q3 receives the low-level detection signal Ss and turns off. The optocoupler OC disconnects the coupling relationship between the control terminal C and the ground terminal through the turn-off of the detection switch Q3, so that the control terminal C receives the control voltage Vc and turns on. On the contrary, when the detection signal Ss corresponds to the output voltage Vo at the second level V2 (taking the high-level detection signal Ss as an example here), the control terminal of the detection switch Q3 receives the high-level detection signal Ss and turns on. At this time, the transmitting end OCA of the optocoupler OC emits light due to the flow of current, and the receiving end OCB of the optocoupler OC receives the light source emitted by the transmitting end OCA and turns on. Therefore, the control terminal C is coupled to the ground terminal through the turn-on of the receiving end OCB.

[0076] On the other hand, the control circuit Cc may optionally include a voltage dividing circuit, and the voltage dividing circuit includes a first voltage dividing resistor R1 and a second voltage dividing resistor R2. One end of the first voltage dividing resistor R1 receives the operating voltage Vcc, and the other end of the first voltage dividing resistor R1 is coupled to the receiving end OCB and the control end C of the optocoupler OC. One end of the second voltage dividing resistor R2 is coupled to the other end of the first voltage dividing resistor R1, and the other end of the second voltage dividing resistor R2 is coupled to the ground terminal. Therefore, when the optocoupler OC opens the coupling relationship between the control end C and the ground terminal, the voltage dividing circuit divides the operating voltage Vcc through the first voltage dividing resistor R1 and the second voltage dividing resistor R2 to establish a control voltage Vc that meets the breakdown voltage specification of the switch Q2 at the control end C to turn on the switch Q2. Conversely, when the receiving end OCB of the optocoupler OC receives the light source emitted by the transmitting end OCA and conducts, the control end C is coupled to the ground terminal through the conduction of the receiving end OCB, so that the voltage received by the control end C is lower than the critical voltage of the switch Q2 and cannot conduct.

[0077] In addition, the control circuit Cc may further include current limiting resistors Rx and Ry. The current limiting resistor Rx is coupled to the output terminal 100-2 and the transmitting end OCA, mainly to avoid excessive current flowing through this path, resulting in excessive power loss and even the risk of overcurrent damage to the electronic components on the path. The current limiting resistor Ry is coupled to the detection switch Q3, and its function is similar to that of the current limiting resistor Rx, which will not be elaborated here. It is worth mentioning that in one embodiment, when the voltage value of the operating voltage Vcc already meets the breakdown voltage specification of the switch Q2, the voltage dividing circuit may not be required, and the operating voltage Vcc can be used as the control voltage Vc. In addition, in another embodiment, the source of the operating voltage Vcc is not limited. It can be the voltage at any point of the power supply 100 as the power source, or it can be externally powered. Therefore, in summary, the over-power protection circuit 100B can be configured not only in converters with isolation transformers. As long as the power supply 100 that uses the voltage provided by the resistor to set the over-power protection value by the controller CL, the over-power protection circuit 100B can be used to adjust the over-power protection value accordingly based on different levels of the output voltage Vo.

[0078] Please refer to Figure 3A the current path diagram when the output voltage of the power supply of the first embodiment of the present invention is at the first level, Figure 3B the current path diagram when the output voltage of the power supply of the first embodiment of the present invention is at the second level, and also refer to Figures 1 - 2 . Taking Figure 3A and 3B as examples, they correspond to the normal operating mode and the standby mode of the power supply 100 respectively, and the output voltages of the normal operating mode and the standby mode are 24V and 5V respectively as illustrative examples. As Figure 3AAs shown, when the load 200 (or the entire system) enters the normal operating mode, the output voltage Vo is at the first level V1 (for example, but not limited to, 24V). The control terminal of the detection switch Q3 receives a low-level detection signal Ss, causing the gate-source bias voltage Vgs of the detection switch Q3 to be lower than its threshold voltage Vth (Threshold Value), resulting in the detection switch Q3 turning off. At this time, no current flows through the diode terminal (i.e., the emitter terminal OCA) of the optocoupler OC. The operating voltage Vcc received on the primary side provides the gate-source bias voltage Vgs (i.e., the control voltage Vc) of the switch Q2 via the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2. Since the gate-source bias voltage Vgs (i.e., the control voltage Vc) of the switch Q2 is greater than its threshold voltage Vth, the switch Q2 conducts, paralleling the first resistor Ra and the second resistor Rb, and the equivalent resistance value of their parallel connection is the first resistance value. At this time, after the current I flowing through the power switch Q1 passes through the first resistor Ra and the second resistor Rb, a voltage Va is generated and provided to the controller CL. After the controller CL calculates the over-power protection value Pp of the output voltage Vo corresponding to the first level V1 based on the voltage Va, it detects the output power through the current detection pin Pc of the controller CL. Among them, the current I is affected by inductive components such as the primary side winding T1 and is generally a continuous triangular waveform with its value varying between high and low. Therefore, preferably, the controller CL can usually set the over-power protection value Pp according to a specific value (such as the peak value or the average value) of the current I.

[0079] As Figure 3B shown, when the load 200 (or the entire system) enters the standby mode, the output voltage Vo is at the second level V2 (for example, but not limited to, 5V). The control terminal of the detection switch Q3 receives a high-level detection signal Ss, causing the gate-source bias voltage Vgs of the detection switch Q3 to be higher than its threshold voltage Vth, resulting in the detection switch Q3 conducting. At this time, current flows through the diode terminal (i.e., the emitter terminal OCA) of the optocoupler OC and emits light, and the receiving terminal OCB of the optocoupler OC receives the light source emitted by the emitter terminal OCA and conducts. The operating voltage Vcc received on the primary side reduces the gate-source bias voltage Vgs of the switch Q2 to less than its threshold voltage Vth via the first voltage-dividing resistor R1 and the transistor terminal (i.e., the receiving terminal OCB) of the optocoupler OC, causing the switch Q2 to turn off, and the resistance value of the second resistor Rb is used as the second resistance value. At this time, after the current I flowing through the power switch Q1 passes through the second resistor Rb, a voltage Va is generated and provided to the controller CL. After the controller CL calculates the over-power protection value Pp of the output voltage Vo corresponding to the second level V2 based on the voltage Va, it detects the output power through the current detection pin Pc of the controller CL.

[0080] Therefore, when the power supply 100 operates in the normal working mode, and when the over-power protection value Pp is calculated by the controller CL to be 96W, the maximum output current will be limited to 4A, and when the output current exceeds 4A, the power supply 100 will perform over-power protection accordingly. On the contrary, when the power supply 100 operates in the standby mode, and when the over-power protection value Pp is calculated by the controller CL to be 20W, the maximum output current will also be limited to 4A, and when the output current exceeds 4A, the power supply 100 will also perform over-power protection accordingly. Therefore, it will not be like the conventional technology where the over-power protection is triggered only when the output current needs to be as high as 19.2A.

[0081] Furthermore, under normal operating conditions, when the power supply 100 operates in the normal working mode, the first resistance value of the first resistor Ra and the second resistor Rb in parallel is relatively small (for example, but not limited to 3 ohms), but the current I is relatively large (for example, but not limited to 4A). On the contrary, when the power supply 100 operates in the standby mode, the first resistance value is relatively large (for example, but not limited to 6 ohms), but the current I will be relatively small (for example, but not limited to 2A). Therefore, the voltage Va obtained by multiplying the two can be equal or approximately the same (12V) under specific conditions, and different over-power protection values Pp can be obtained after calculation by the controller CL (for example, in cooperation with detecting the current, voltage, etc. at other points).

[0082] Please refer to Figure 4 FIG. shows the detailed circuit block diagram of the second embodiment of the power supply of the present invention having an over-power protection value adjustment function, and also refer to Figures 1 - 3B . Figure 4 The power supply 100 of Figure 2 is different in that the power supply 100 has an auxiliary power supply circuit, and the auxiliary power supply circuit includes an auxiliary winding T3, a diode D2, and an energy storage capacitor Cb. In addition, the over-power protection circuit 100B includes a voltage stabilizing circuit ZD. Among them, Figure 2 The power supply 100 of

[0083] Specifically, when the output voltage Vo is at the first level V1 (for example, but not limited to, 24V), the operating voltage Vcc provided by the auxiliary power supply circuit is at the third level V3 corresponding to the first level V1 (for example, but not limited to, 50V), and the voltage regulator circuit ZD establishes a control voltage Vc at the control terminal C based on the fact that the operating voltage Vcc at the third level V3 is higher than the clamping voltage of the voltage regulator circuit ZD (for example, but not limited to, 30V). Conversely, when the output voltage Vo is at the second level V2 (for example, but not limited to, 5V), the operating voltage Vcc provided by the auxiliary power supply circuit is at the fourth level V4 corresponding to the second level V2 (for example, but not limited to, 10V), and the voltage regulator circuit limits the voltage at the control terminal C to be lower than the critical voltage Vth of the switch Q2 based on the fact that the operating voltage Vcc at the fourth level V4 is lower than the clamping voltage (for example, but not limited to, 30V).

[0084] Among them, the voltage regulator circuit ZD preferably can be a Zener diode, but is not limited thereto. Any circuit that can control the conduction or cutoff of the switch Q2 by adjusting the voltage at the control terminal C based on different operating voltages Vcc should be included in the scope of this embodiment. Taking the Zener diode as an example, when the operating voltage Vcc is higher than the breakdown voltage of the Zener diode (i.e., the clamping voltage, for example, but not limited to, 30V), a voltage difference of 30V is established across both ends of the Zener diode, and the sum of the operating voltage Vcc and the breakdown voltage (i.e., the clamping voltage) can establish a control voltage Vc (for example, but not limited to, 20V) at the control terminal C that can turn on the switch Q2. Conversely, when the operating voltage Vcc is not higher than the breakdown voltage of the Zener diode, the Zener diode is reverse-biased and cut off to limit the voltage at the control terminal C to be lower than the critical voltage Vth of the switch Q2.

[0085] On the other hand, in Figure 4 it may also selectively include a voltage dividing circuit, and the voltage dividing circuit includes a first voltage dividing resistor R1 and a second voltage dividing resistor R2. One end of the first voltage dividing resistor R1 is coupled to the voltage regulator circuit ZD, and the other end is coupled to the control terminal C. One end of the second voltage dividing resistor R2 is coupled to the other end of the first voltage dividing resistor R1, and the other end of the second voltage dividing resistor R2 is coupled to the ground terminal. Therefore, when the operating voltage Vcc is higher than the clamping voltage, an operating voltage is established at one end of the first voltage dividing resistor R1, and the operating voltage is the sum of the operating voltage Vcc at the third level V3 and the clamping voltage. The voltage dividing circuit divides the operating voltage through the first voltage dividing resistor R1 and the second voltage dividing resistor R2 to establish a control voltage Vc at the control terminal C to turn on the switch Q2. Taking the Zener diode as an example, the sum of the 50V operating voltage Vcc and the 30V breakdown voltage (i.e., the clamping voltage) is 20V, and after the 20V is divided by the voltage dividing circuit, a control voltage Vc that meets the voltage withstand specification of the switch Q2 is established at the control terminal C to turn on the switch Q2. It is worth mentioning that in one embodiment, Figure 4Circuit components, connection relationships, and operation methods not described are all similar to Figure 2 , and will not be elaborated here.

[0086] Please refer to Figure 5A for the current path diagram when the output voltage of the power supply of the second embodiment of the present invention is at the first level, Figure 5B and for the current path diagram when the output voltage of the power supply of the second embodiment of the present invention is at the second level. Also, please refer to Figures 1 - 4 . Taking Figure 5A and 5B as examples, they respectively correspond to the normal working mode and standby mode of the power supply 100, and the output voltages in the normal working mode and standby mode are 24V and 5V respectively as illustrative examples. In addition, the voltage stabilizing circuit ZD takes the zener diode as an example. As Figure 5A shows, when the load 200 (or the entire system) enters the normal working mode, the output voltage Vo is at the first level V1 (for example, but not limited to, 24V). At this time, the auxiliary power supply circuit generates a working voltage Vcc at a higher third level (for example, but not limited to, 50V) due to the coupling transformer T. Since the working voltage Vcc is higher than the clamping voltage of the voltage stabilizing circuit ZD (for example, but not limited to, 30V), the operating voltage (20V) after being clamped by the voltage stabilizing circuit ZD provides the gate-source bias voltage Vgs (i.e., the control voltage Vc) of the switch Q2 via the first voltage dividing resistor R1 and the second voltage dividing resistor R2. Since the gate-source bias voltage Vgs (i.e., the control voltage Vc) of the switch Q2 is greater than its threshold voltage Vth, the switch Q2 is turned on to parallel the first resistor Ra and the second resistor Rb, and the equivalent resistance value of their parallel connection is the first resistance value.

[0087] As Figure 5B shows, when the load 200 (or the entire system) enters the standby mode, the output voltage Vo is at the second level V2 (for example, but not limited to, 5V). At this time, the auxiliary power supply circuit generates a working voltage Vcc at a lower fourth level (for example, but not limited to, 10V) due to the coupling transformer T. Since the working voltage Vcc is lower than the clamping voltage of the voltage stabilizing circuit ZD (for example, but not limited to, 30V), the voltage stabilizing circuit ZD is reversely biased and cut off, resulting in the gate-source bias voltage Vgs of the switch Q2 dropping to less than its threshold voltage Vth, and causing the switch Q2 to turn off, and the resistance value of the second resistor Rb is taken as the second resistance value. It is worth mentioning that in one embodiment, Figure 5A , 5B Circuit components, connection relationships, and operation methods not described are all similar to Figure 3A , 3B , and will not be elaborated here.

[0088] Please refer to Figure 6This is a flowchart of a method for adjusting the over-power protection value of a power supply unit according to the present invention. Referring to Figures 1 - 5B . The over-power protection value adjustment method of the present invention is mainly applied to a power supply unit 100 having a power switch Q1 and a controller CL, and the controller CL can set the over-power protection value Pp according to the voltage level of the output voltage Vo of the power supply unit 100. Therefore, the over-power protection value adjustment method includes turning on a switch (S100) connected in series to the power switch according to the output voltage of the power supply unit being at a first level. When the power supply unit 100 operates in, for example but not limited to, a normal operating mode, the output voltage Vo is at a first level V1 (for example but not limited to, 24V). When the output voltage Vo is at the first level V1, the over-power protection circuit 100B turns on the switch Q2 according to the output voltage Vo at the first level V1.

[0089] Then, according to the conduction of the switch, a first resistance value is provided, and thus the over-power protection value is adjusted to a first value according to the voltage corresponding to the first resistance value (S120). A preferred embodiment is that when the switch Q2 is turned on, the parallel connection of resistors (for example but not limited to, the first resistor Ra and the second resistor Rb in parallel) is used to provide a smaller first resistance value. Therefore, when the power switch Q1 is turned on, the product of the current I and the first resistance value is the voltage Va, and the controller CL can adjust the over-power protection value Pp to the first value accordingly according to the voltage Va corresponding to the first resistance value.

[0090] Then, the switch is turned off according to the output voltage being at a second level (S140). On the contrary, when the power supply unit 100 operates in, for example but not limited to, a standby mode, the output voltage Vo is at a second level V2 (for example but not limited to, 5V), and generally the first level V1 is greater than the second level V2. When the output voltage Vo is at the second level V2, the over-power protection circuit 100B turns off the switch Q2 according to the output voltage Vo at the second level V2. Finally, a second resistance value is provided according to the turn-off of the switch, and thus the over-power protection value is adjusted to a second value according to the voltage corresponding to the second resistance value (S160). A preferred embodiment is that when the switch Q2 is turned off, a single resistor (for example but not limited to, a single second resistor Rb) is used to provide a larger second resistance value. Therefore, when the power switch Q1 is turned on, the product of the current I and the second resistance value is the voltage Va, and the controller CL can adjust the over-power protection value Pp to the second value accordingly according to the voltage Va corresponding to the second resistance value.

[0091] It is worth mentioning that in one embodiment, for the detailed steps not described in the above method flow, reference can be made to Figures 2 - 5B , and details will not be elaborated here. In addition, in Figure 6In the method steps, the coupling relationship of each component is not limited. As long as the coupling relationship that can obtain the required parameters according to the actions of each component, it should be included in the scope of this embodiment.

[0092] As described above, it is only the detailed description and drawings of the preferred specific embodiment of the present invention. However, the features of the present invention are not limited thereto, and it is not used to limit the present invention. The entire scope of the present invention should be subject to the scope of the patent application. All embodiments that conform to the spirit of the scope of the patent application of the present invention and its similar variations should be included in the scope of the present invention. Any changes or modifications that can be easily thought of by those skilled in the art within the field of the present invention can be covered within the scope of the patent of the present invention.

Claims

1. A power supply, characterized in that, it supplies power to a load by providing an output voltage from an output terminal, and the power supply includes: an over-power protection circuit, including: a switch, including a first terminal and a second terminal, the first terminal being coupled to a power switch and a controller of the power supply, and the controller setting an over-power protection value of the power supply according to a voltage at the first terminal; a first resistor, one end of which is coupled to the second terminal; and a second resistor, one end of which is coupled to the first terminal and the other end of which is coupled to the other end of the first resistor; wherein, when the output voltage is at a first level, the over-power protection circuit turns on the switch according to the output voltage at the first level to provide a first resistance value of the first resistor and the second resistor in parallel, thereby adjusting the over-power protection value to a first value; when the output voltage is at a second level less than the first level, the over-power protection circuit turns off the switch according to the output voltage at the second level to provide a second resistance value of the second resistor, thereby adjusting the over-power protection value to a second value.

2. The power supply according to claim 1, characterized in that, the over-power protection circuit further includes: a control circuit, coupled to the output terminal and a control terminal of the switch, and receiving a detection signal; wherein, when the detection signal indicates that the output voltage is at the first level, the control circuit controls the switch to turn on, and when the detection signal indicates that the output voltage is at the second level, the control circuit controls the switch to turn off.

3. The power supply according to claim 2, characterized in that, the power supply has a primary side and a secondary side, the power switch is disposed on the primary side, and the output terminal is disposed on the secondary side, and the control circuit includes: an optocoupler, coupled to the output terminal and the control terminal of the switch; and a detection switch, coupled to the optocoupler and receiving the detection signal; wherein, when the detection signal corresponds to the output voltage at the first level, the detection switch turns off, and the optocoupler opens the coupling relationship between the control terminal and a ground terminal through the turn-off of the detection switch, so that the control terminal receives a control voltage; when the detection signal corresponds to the second level, the detection switch turns on, and the optocoupler couples the control terminal to the ground terminal through the turn-on of the detection switch.

4. The power supply according to claim 3, characterized in that, the control circuit further includes: a voltage dividing circuit, including: a first voltage dividing resistor, one end of which receives a working voltage and the other end of which is coupled to the optocoupler and the control terminal; and a second voltage dividing resistor, one end of which is coupled to the other end of the first voltage dividing resistor and the other end of which is coupled to the ground terminal; wherein, the voltage dividing circuit divides the working voltage through the first voltage dividing resistor and the second voltage dividing resistor to establish the control voltage at the control terminal to turn on the switch.

5. The power supply according to claim 1, characterized in that, the power supply has a transformer and an auxiliary power supply circuit, the auxiliary power supply circuit is coupled to the transformer to provide a working voltage, and the over-power protection circuit further includes: A voltage stabilizing circuit is coupled to a control terminal of the switch and receives the operating voltage; Wherein, when the output voltage is at the first level, the operating voltage provided by the auxiliary power supply circuit is a third level corresponding to the first level, and the voltage stabilizing circuit establishes a control voltage at the control terminal according to the operating voltage of the third level being higher than a clamping voltage of the voltage stabilizing circuit; when the output voltage is at the second level, the operating voltage provided by the auxiliary power supply circuit is a fourth level corresponding to the second level, and the voltage stabilizing circuit restricts the voltage at the control terminal to be lower than a critical voltage according to the operating voltage of the fourth level being lower than the clamping voltage.

6. The power supply according to claim 5, characterized in that, the voltage stabilizing circuit further comprises: a voltage dividing circuit, comprising: a first voltage dividing resistor, one end of which is coupled to the voltage stabilizing circuit and the other end of which is coupled to the control terminal; and a second voltage dividing resistor, one end of which is coupled to the other end of the first voltage dividing resistor and the other end of which is coupled to a ground terminal; wherein, the voltage dividing circuit divides a operating voltage through the first voltage dividing resistor and the second voltage dividing resistor to establish the control voltage at the control terminal to turn on the switch, and the operating voltage is the sum of the operating voltage of the third level and the clamping voltage.

7. The power supply according to claim 5, characterized in that, the voltage stabilizing circuit is a zener diode, when the operating voltage is at the third level, the zener diode breaks down to establish the clamping voltage, and when the operating voltage is at the fourth level, the zener diode is reverse biased and cut off.

8. An over-power protection value adjustment method, characterized in that, applied to a power supply having a power switch and a controller, and the controller sets an over-power protection value according to a voltage, the over-power protection value adjustment method comprises the following steps: Turn on a switch connected in series with the power switch according to an output voltage of the power supply being at a first level; Provide a first resistance value according to the turn-on of the switch, and thus adjust the over-power protection value to a first value according to the voltage corresponding to the first resistance value; Turn off the switch according to the output voltage being at a second level; and Provide a second resistance value according to the turn-off of the switch, and thus adjust the over-power protection value to a second value according to the voltage corresponding to the second resistance value; wherein, the first level is greater than the second level, and the first resistance value is less than the second resistance value.

9. The over-power protection value adjustment method according to claim 8, characterized in that, further comprises the following steps: Receive a detection signal; Turn off a detection switch according to the detection signal corresponding to the output voltage of the first level; Provide a control voltage to a control terminal of the switch through the turn-off of the detection switch; Turn on the detection switch according to the detection signal corresponding to the output voltage of the second level; and Couple the control terminal to a ground terminal through the turn-on of the detection switch.

10. The over-power protection value adjustment method according to claim 8, characterized in that, further comprises the following steps: Generate an operating voltage of a third level corresponding to the output voltage being at the first level; Establish a control voltage at a control terminal of the switch according to that the operating voltage of the third level is higher than a clamping voltage of a voltage stabilizing circuit; Generate an operating voltage of a fourth level correspondingly according to that the output voltage is at the second level; and Limit the voltage at the control terminal to be lower than a critical voltage according to that the operating voltage of the fourth level is lower than the clamping voltage.

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