TWI502874B - Electronic apparatus and power adapter thereof and operation method of power adapter - Google Patents

Description

Electronic device and its power adapter and operation method of power adapter

The present invention relates to an electronic device, and more particularly to a power adapter of an electronic device and a method of operating the power adapter.

A power adapter converts utility power to direct current to power the electronics. In general, the rated output voltage of the power adapter must meet the power requirements of different loads within the electronic device. For example, the battery charging module inside the notebook requires 17.8 V (volts), while the chipset inside the notebook requires 5 V. Therefore, the rated output voltage of the power adapter can be set to 19 V to meet the power requirements of the battery charging module and the chipset. Usually, different DC/DC converters or voltage regulators are arranged inside the electronic device to step down the output voltage of the power adapter to the rated operating voltage of the corresponding load.

For the rated operating voltage of the same load, the higher the rated output voltage of the power adapter, the lower the conversion efficiency of the voltage regulator. For example, FIG. 1 is a schematic diagram of a conversion characteristic curve of a voltage regulator, in which the vertical axis represents the conversion efficiency of the voltage regulator, and the horizontal axis represents the output current of the voltage regulator. In Figure 1, The three conversion characteristic curves respectively show the input voltages of the voltage regulators of 5 V, 7 V, and 12 V, and the output voltage of the voltage regulator is set to, for example, 3.3 V. It can be known from FIG. 1 that the higher the rated output voltage of the power adapter is, the larger the difference between the input voltage and the output voltage of the voltage regulator is, and the lower the conversion efficiency of the voltage regulator is.

However, the output voltage of a conventional power adapter is fixed. Conventional power adapters still provide a fixed output voltage to the electronic device when the large voltage load inside the electronic device is disabled and only a small voltage load is required to supply power. For example, when the battery charging module inside the notebook computer no longer needs to be charged, or when the battery is removed, the operating voltage of other loads inside the notebook computer is less than or equal to 5 V. At this point, the traditional power adapter still provides a fixed output voltage (19 V) to the notebook, causing the notebook to waste a lot of power due to poor conversion efficiency of the internal voltage regulator.

The invention provides an electronic device and a power adapter thereof and a method for operating the power adapter to improve the power conversion efficiency of the electronic device.

An electronic device according to an embodiment of the invention includes a host and a power adapter. The host has a power connector. A power adapter is coupled to the power connector to supply an output current and an output voltage to the host. The power adapter adjusts the level of the output voltage according to the magnitude of the output current.

A power adapter of an embodiment of the invention includes a rectifier circuit and a voltage regulation circuit. The rectifier circuit converts the alternating current into direct current. The voltage regulating circuit is coupled to the rectifier circuit. The voltage regulation circuit uses the DC power to supply output current and output The voltage is output to a host external to the power adapter, and the level of the output voltage is adjusted correspondingly according to the output current.

A method for operating a power adapter according to an embodiment of the present invention includes: providing an output current and an output voltage to a host; detecting a magnitude of the output current; and adjusting the output voltage according to the magnitude of the output current Bit.

Based on the above, the power adapter in the embodiment of the present invention adjusts the level of the output voltage according to the magnitude of the output current. When the host enters the light load state, the power adapter can adjust the level of the output voltage accordingly. Therefore, the difference between the input voltage and the output voltage of the internal voltage regulator of the host can be reduced, thereby increasing the conversion efficiency of the voltage regulator.

The above described features and advantages of the invention will be apparent from the following description.

10‧‧‧Electronic devices

11‧‧‧Power adapter

12‧‧‧Host

510‧‧‧Rectifier circuit

520‧‧‧Voltage adjustment circuit

610‧‧‧Main power circuit

620‧‧‧reference voltage generation circuit

630‧‧‧Control unit

710, 742‧‧ ‧ reference voltage source

720, 731, 841, 842, 911, 951, R1‧‧‧ resistance

730, 940‧‧‧ current detection circuit

732, 741, 850‧‧‧ error amplifier

740‧‧‧Comparative circuit

810, 941‧‧‧ transformer

811‧‧‧main coil

812‧‧‧second coil

820‧‧‧ switch

830‧‧‧Rectifier filter circuit

831, 920‧‧ ‧ diode

832, 930‧‧‧ capacitor

840‧‧‧Return circuit

860‧‧‧Opto-coupling components

870‧‧‧Drive circuit

910‧‧‧First reference voltage source

912, 952‧‧ ‧ Zener diode unit

942‧‧‧second diode

943‧‧‧second capacitor

950‧‧‧second reference voltage source

Io‧‧‧ output current

Ith‧‧‧critical current

S31~S33‧‧‧Steps

Sc‧‧‧ control signal

Vac‧‧‧AC

Vdc‧‧‧DC

Vfb‧‧‧ feedback voltage

Vmax‧‧‧Maximum voltage level

Vmin‧‧‧ minimum voltage level

Vo‧‧‧ output voltage

Vp‧‧‧Power supply voltage

Vref‧‧‧reference voltage

Figure 1 is a schematic diagram of a conversion characteristic curve of a voltage regulator.

FIG. 2 is a block diagram showing the function of an electronic device according to an embodiment of the invention.

FIG. 3 is a schematic flow chart illustrating a method of operating a power adapter according to an embodiment of the invention.

4 is a schematic diagram showing a characteristic curve of an output current to an output voltage of a power adapter according to an embodiment of the invention.

FIG. 5 is a block diagram showing a power adapter according to an embodiment of the invention. intention.

FIG. 6 is a block diagram showing a circuit of a voltage regulating circuit according to an embodiment of the invention.

FIG. 7 is a circuit diagram showing the reference voltage generating circuit shown in FIG. 6 according to an embodiment of the present invention.

FIG. 8 is a block diagram showing the circuit of a voltage regulating circuit according to another embodiment of the present invention.

FIG. 9 is a block diagram showing the circuit of a voltage regulating circuit according to still another embodiment of the present invention.

The term "coupled" as used throughout the specification (including the scope of the patent application) may be used in any direct or indirect connection. For example, if the first device is described as being coupled to the second device, it should be construed that the first device can be directly connected to the second device, or the first device can be connected through other devices or some kind of connection means. Connected to the second device indirectly. In addition, wherever possible, the elements and/ Elements/components/steps that use the same reference numbers or use the same terms in different embodiments may refer to the related description.

2 is a functional block diagram of an electronic device 10 according to an embodiment of the invention. The electronic device 10 includes a power adapter 11 and a host 12. The host 12 has a power connector to connect to the power adapter 11. The power adapter 11 supplies the output current Io and the output voltage Vo to the host 12 through the power connector. The host 12 can be any electronic product, such as a notebook computer, a tablet computer, a smart phone. (smart phone) and so on.

FIG. 3 is a flow chart showing a method of operating the power adapter 11 according to an embodiment of the invention. Referring to FIG. 2 and FIG. 3, the power adapter 11 supplies the output current Io and the output voltage Vo to the host 12 in step S31. The power adapter 11 proceeds to step S32 to detect the magnitude of the output current Io. The power adapter 11 proceeds to step S33 to adjust the level of the output voltage Vo in accordance with the magnitude of the output current Io.

In different embodiments, step S33 can take different adjustment schemes. For example, in this embodiment, the power adapter 11 can adjust the output voltage Vo between the maximum voltage level Vmax and the minimum voltage level Vmin according to the output current Io in step S33. The maximum voltage level Vmax can be determined according to the maximum demand voltage of the host 12. For example, if the battery charging module inside the notebook computer (host 12) requires a charging voltage of 17.8 V (volts), the maximum voltage level Vmax of the power adapter 11 can be set to be greater than or equal to 17.8 V (for example, 19). V). The minimum voltage level Vmin can be determined according to the design requirements of the actual product. For example, in some embodiments, the minimum voltage level Vmin can be set to 0V. In other embodiments, the minimum voltage level Vmin can be set to be greater than or equal to the minimum startup voltage of the internal circuitry of the power adapter 11.

FIG. 4 is a schematic diagram showing the characteristic curve of the output current Io of the power adapter 11 versus the output voltage Vo according to an embodiment of the invention. In FIG. 4, the vertical axis represents the output voltage Vo of the power adapter 11, and the horizontal axis represents the output current Io of the power adapter 11. Referring to FIG. 2 to FIG. 4, when the output current Io increases due to the power demand of the host 12, the power adapter 11 correspondingly increases the level of the output voltage Vo in step S33. When the output current Io is reduced due to the power demand of the host 12, the power adapter 11 correspondingly lowers the level of the output voltage Vo in step S33. When the output current Io is 0 due to no load (for example, the power adapter 11 is unplugged from the host 12), the power adapter 11 In step S33, the output voltage Vo is correspondingly adjusted to a minimum voltage level Vmin. When the output current Io increases to the critical current amount Ith (for example, 0.1 A (amperes) or other value), the power adapter 11 correspondingly increases the output voltage Vo to the maximum voltage level Vmax in step S33. When the output current Io is greater than the critical current amount Ith, the power adapter 11 maintains the level of the output voltage Vo at the maximum voltage level Vmax in step S33.

It should be noted that although the embodiment shown in FIG. 4 adjusts the level of the output voltage Vo in a linear manner, the implementation of step S33 should not be limited thereto. For example, in another embodiment, the power adapter 11 can adjust the level of the output voltage Vo in a stepwise manner or in other manners in step S33.

Based on the above, the power adapter 11 in the above embodiment can adjust the level of the output voltage Vo according to the magnitude of the output current Io. Therefore, when the host 12 enters a light load state (for example, a standby mode, a sleep mode, a sleep mode, a no-charge mode, etc.), the power adapter 11 can correspondingly lower the level of the output voltage Vo. Since the power adapter 11 can lower the level of the output voltage Vo during the light load state of the host 12, the difference between the input voltage and the output voltage of the internal voltage regulator of the host 12 can be reduced, thereby allowing the host 12 to The conversion efficiency of the internal voltage regulator is improved.

The power adapter 11 can be implemented in any manner. For example, FIG. 5 is a block diagram showing a circuit of a power adapter 11 according to an embodiment of the invention. In the present embodiment, the power adapter 11 includes a rectifier circuit 510 and a voltage regulation circuit 520. The rectifier circuit 510 can convert an alternating current Vac (eg, mains or other alternating voltage) into a direct current Vdc. Rectifier circuit 510 can be implemented in any manner. For example, in some embodiments, the rectifier circuit 510 can include a half wave rectifier circuit, a full wave rectifier circuit, a bridge rectifier circuit, or other AC to DC conversion circuit.

The voltage regulation circuit 520 is coupled to the rectifier circuit 510. Voltage regulation circuit The 520 uses the direct current Vdc to supply the output current Io and the output voltage Vo to the host 12, and adjusts the level of the output voltage Vo according to the output current Io. The operation method of the voltage adjustment circuit 520 can refer to the related description of FIG. 3, and therefore will not be described again.

Voltage regulation circuit 520 can be implemented in any manner. For example, FIG. 6 is a block diagram showing a circuit of a voltage regulating circuit 520 according to an embodiment of the invention. In the present embodiment, the voltage regulating circuit 520 includes a main power circuit 610, a reference voltage generating circuit 620, and a control unit 630. The main power supply circuit 610 receives the direct current Vdc and supplies the output current Io and the output voltage Vo to the host 12. According to the control signal Sc, the main power supply circuit 610 can adjust the level of the output voltage Vo.

The reference voltage generating circuit 620 is coupled to the control unit 630 to provide a reference voltage Vref to the control unit 630. The control unit 630 is coupled to the main power circuit 610. According to the relationship between the level of the output voltage Vo and the level of the reference voltage Vref, the control unit 630 supplies and adjusts the control signal Sc to the main power circuit 610 to control the main power circuit 610 to adjust the level of the output voltage Vo. The reference voltage generating circuit 620 can further adjust the level of the reference voltage Vref according to the output current Io of the main power circuit 610.

FIG. 7 is a circuit diagram showing the reference voltage generating circuit 620 of FIG. 6 in accordance with an embodiment of the present invention. In the present embodiment, the reference voltage generating circuit 620 includes a reference voltage source 710, a resistor 720, a current detecting circuit 730, and a comparing circuit 740. The reference voltage source 710 provides a second reference voltage relative to the maximum voltage level Vmax. The first end of the resistor 720 is coupled to the reference voltage source 710. The second end of the resistor 720 is coupled to the control unit 630 to provide a reference voltage Vref. When the level of the reference voltage Vref is the level of the second reference voltage, the control unit 630 controls the main power circuit 610 according to the level of the reference voltage Vref such that the level of the output voltage Vo of the main power circuit 610 is the Maximum voltage level Vmax.

The current detecting circuit 730 is coupled to the output of the main power circuit 610 to detect the output current Io and output a detection result. The output of the comparison circuit 740 is coupled to the second end of the resistor 720, and the input of the comparison circuit 740 is coupled to the output of the current detection circuit 730. Wherein, when the detection result indicates that the output current Io is greater than the critical current amount Ith, the output end of the comparison circuit 740 is in a high impedance state. At this time, the level of the reference voltage Vref is the level of the second reference voltage provided by the reference voltage source 710. When the detection result indicates that the output current Io is smaller than the critical current amount Ith, the output voltage of the comparison circuit 740 is correspondingly adjusted in accordance with the magnitude of the output current Io. At this time, the level of the reference voltage Vref is pulled up or pulled low by the output of the comparison circuit 740. When the level of the reference voltage Vref is changed by the comparison circuit 740, the control unit 630 controls the main power supply circuit 610 according to the level of the reference voltage Vref, so that the level of the output voltage Vo of the main power supply circuit 610 is dynamically adjusted to the maximum voltage level. Between the bit Vmax and the minimum voltage level Vmin.

The current detecting circuit 730 and the comparing circuit 740 described above can be implemented in any manner. For example, current sense circuit 730 shown in FIG. 7 includes a resistor 731 and an error amplifier (or voltage comparator) 732, while comparator circuit 740 includes an error amplifier (or voltage comparator) 741. The resistor 731 is disposed on the output current path of the main power supply circuit 610 such that the output current Io flows through the resistor 731. The output current Io flowing through the resistor 731 causes a voltage difference across the resistor 731, which is proportional to the output current Io. The first input end and the second input end of the error amplifier 732 are respectively coupled to both ends of the resistor 731. The error amplifier 732 can compare the voltage difference across the resistor 731 and then output an error voltage corresponding to this voltage difference to the error amplifier 741. The error voltage is responsive to the output current Io.

The error amplifier 741 receives and compares the error voltage output by the error amplifier 732 and the third reference voltage provided by the reference voltage source 742. The third parameter The level of the test voltage is relative to the magnitude of the critical current amount Ith. When the error voltage output by the error amplifier 732 is greater than the third reference voltage provided by the reference voltage source 742, the output of the error amplifier 741 is in a high impedance state. When the error voltage output by the error amplifier 732 is less than the third reference voltage provided by the reference voltage source 742, the voltage at the output of the error amplifier 741 may vary depending on the difference between the error voltage and the third reference voltage. And change.

The main power supply circuit 610, the reference voltage generation circuit 620, and the control unit 630 shown in FIG. 6 can be implemented in any manner. For example, FIG. 8 is a block diagram showing the circuit of voltage regulating circuit 520 in accordance with another embodiment of the present invention. The embodiment shown in FIG. 8 can be analogized with reference to the related description of FIGS. 2 to 7.

Referring to FIG. 8 , in the embodiment, the main power circuit 610 includes a transformer 810 , a switch 820 , and a rectification filter circuit 830 . The transformer 810 includes a primary coil 811 and a secondary coil 812. The first end of the main coil 811 receives the direct current Vdc, and the first end of the secondary coil 812 is coupled to a reference voltage (for example, a ground voltage on the side of the secondary coil, hereinafter referred to as a second ground voltage). The second end of the main coil 811 is coupled to the first end of the switch 820. The second end of the switch 820 is coupled to a reference voltage (eg, a ground voltage on the main coil side, hereinafter referred to as a first ground voltage). The control terminal of the switch 820 serves as a control terminal of the main power supply circuit 610 to be coupled to the control unit 630 to receive the control signal Sc. The input end of the rectifying and filtering circuit 830 is coupled to the second end of the sub-coil 812. The output of the rectification filter circuit 830 provides an output voltage Vo.

The rectification and filtering circuit 830 described above can be implemented in any manner. For example, the rectification filter circuit shown in FIG. 7 includes a diode 831 and a capacitor 832. The anode of the diode 831 is coupled to the second end of the secondary coil 812. The cathode of the diode 831 provides an output voltage Vo. The first end of the capacitor 832 is coupled to the cathode of the diode 831. The second end of the capacitor 832 is coupled to the second ground voltage.

In the present embodiment, the control unit 630 includes a feedback circuit 840, an error amplifier 850, a photocoupler element 860, and a drive circuit 870. The feedback circuit 840 is coupled to the output of the main power circuit 610 to receive the output voltage Vo. The feedback circuit 840 can output a feedback voltage Vfb corresponding to the output voltage Vo. The inverting input of the error amplifier 850 is coupled to the feedback circuit 840 to receive the feedback voltage Vfb. The non-inverting input of the error amplifier 850 is coupled to the reference voltage generating circuit 620 to receive the reference voltage Vref.

The feedback circuit 840 described above can be implemented in any manner. For example, in the embodiment illustrated in FIG. 8, the feedback circuit 840 includes a resistor 841 and a resistor 842. The first end of the resistor 841 is coupled to the output of the main power circuit 610 to receive the output voltage Vo. The second end of the resistor 841 is coupled to the inverting input of the error amplifier 850. The first end of the resistor 842 is coupled to the second end of the resistor 841. The second end of the resistor 842 is coupled to the second ground voltage. Therefore, the feedback circuit 840 can divide the output voltage Vo and output the corresponding feedback voltage Vfb to the inverting input terminal of the error amplifier 850.

The reference voltage generating circuit 620 can adjust the level of the reference voltage Vref according to the output current Io of the main power circuit 610. The feedback circuit 840 can detect the output voltage Vo and then output a feedback voltage Vfb corresponding to the output voltage Vo. The error amplifier 850 correspondingly outputs the comparison result to the photocoupler element 860 in accordance with the voltage difference between the feedback voltage Vfb and the reference voltage Vref.

The light emitting portion of the photocoupler element 860 is coupled to the output of the error amplifier 850. In this embodiment, the light emitting portion may include a light emitting diode, wherein the anode and the cathode of the light emitting diode are respectively coupled to the first end of the resistor R1 and the output end of the error amplifier 850. The second end of the resistor R1 is coupled to a power supply voltage Vp. The power supply voltage Vp may be, for example, a fixed voltage provided by a stable voltage source, Or the output voltage Vo output by the main power circuit 610. In other embodiments, the supply voltage Vp can be any reference voltage.

The photodetecting portion of the photocoupler element 860 is coupled to the input end of the driving circuit 870. In this embodiment, the light detecting portion may include a photoelectric crystal. The emitter of the photo transistor is coupled to the first ground voltage (ground voltage on the main coil side). The collector of the optoelectronic crystal is coupled to the input of the driver circuit 870. The output of the driving circuit 870 is coupled to the control terminal of the main power circuit 610 to provide a control signal Sc. The driving circuit 870 can adjust the control signal Sc correspondingly according to the signal of the input end of the driving circuit 870. This embodiment does not limit the means by which the drive circuit 870 adjusts the control signal Sc. For example, pulse width modulation (PWM) or other modulation/adjustment means can be used to implement drive circuit 870.

Therefore, the control unit 630 can control the main power circuit 610 to adjust the level of the output voltage Vo according to the relationship between the level of the output voltage Vo and the level of the reference voltage Vref. That is to say, the control unit 630 can adjust the level of the output voltage Vo according to the output current Io.

FIG. 9 is a block diagram showing a circuit of a voltage regulating circuit 520 according to still another embodiment of the present invention. The embodiment shown in FIG. 9 can be analogized with reference to the related description of FIGS. 2 to 8. For example, the main power supply circuit 610, the reference voltage generation circuit 620, and the control unit 630 shown in FIG. 9 can be analogized with reference to the descriptions of the main power supply circuit 610, the reference voltage generation circuit 620, and the control unit 630 shown in FIGS. 6 and 8. Different from the embodiment shown in FIG. 8, the reference voltage generating circuit 620 shown in FIG. 9 includes a first reference voltage source 910, a diode 920, a capacitor 930, a current detecting circuit 940, and a second reference voltage source 950.

The output of the first reference voltage source 910 is coupled to the anode of the diode 920 to provide a reference voltage relative to the minimum voltage level Vmin. Dipole The cathode of 920 is coupled to the output of reference voltage generating circuit 620. The first end of the capacitor 930 is coupled to the cathode of the diode 920. The second end of the capacitor is coupled to a reference voltage (eg, a ground voltage on the side of the secondary coil, hereinafter referred to as a second ground voltage).

The current detecting circuit 940 is coupled to the output current path of the main power circuit 610 to detect the output current Io and output the detection result to the second reference voltage source 950. The output of the second reference voltage source 950 is coupled to the cathode of the diode 920. The input end of the second reference voltage source 950 is coupled to the output of the current detecting circuit 940 to receive the detection result of the current detecting circuit 940. When the detection result indicates that the output current Io is greater than the critical current amount Ith, the output of the second reference voltage source 950 provides a reference voltage with respect to the maximum voltage level Vmax. When the detection result indicates that the output current Io is smaller than the critical current amount Ith, the voltage of the output terminal of the second reference voltage source 950 is correspondingly adjusted according to the magnitude of the output current Io.

The first reference voltage source 910 described above can be implemented in any manner. For example, in the embodiment illustrated in FIG. 9 , the first reference voltage source 910 includes a resistor 911 and a Zener diode unit 912 . The first end of the resistor 911 is coupled to the output of the main power circuit 610 to receive the output voltage Vo. The second end of the resistor 911 is coupled to the output end of the first reference voltage source 910. The cathode of the Zener diode unit 912 is coupled to the second end of the resistor 911. The anode of the Zener diode unit 912 is coupled to a second ground voltage (ground voltage on the secondary coil side). The breakdown voltage of the Zener diode unit 912 can provide a reference voltage relative to the minimum voltage level Vmin.

The current detecting circuit 940 described above can be implemented in any manner. For example, in the embodiment illustrated in FIG. 9, the current detecting circuit 940 includes a transformer 941, a second diode 942, and a second capacitor 943. The main coil of the transformer 941 is disposed on the output current path of the main power supply circuit 610 such that the output current Io flows through the main coil of the transformer 941. The first end of the secondary winding of the transformer 941 is coupled to the second ground voltage (the secondary Ground voltage on the coil side). The anode of the second diode 942 is coupled to the second end of the secondary winding of the transformer 941. The cathode of the second diode 942 is coupled to the output of the current detecting circuit 940. The first end of the second capacitor 943 is coupled to the cathode of the second diode 942. The second end of the second capacitor 943 is coupled to the second ground voltage (the ground voltage on the secondary coil side).

The second reference voltage source 950 described above can be implemented in any manner. For example, in the embodiment illustrated in FIG. 9, the second reference voltage source 950 includes a resistor 951 and a Zener diode unit 952. The first end of the resistor 951 is coupled to the input end of the second reference voltage source 940 to receive the detection result of the second reference voltage source 940. The second end of the resistor 951 is coupled to the output of the second reference voltage source 950. The cathode of the Zener diode unit 952 is coupled to the second end of the resistor 951. The anode of the Zener diode unit 952 is coupled to a second ground voltage (ground voltage on the secondary coil side). The breakdown voltage of the Zener diode unit 952 can provide a reference voltage relative to the maximum voltage level Vmax.

When the output current Io is reduced due to the power demand of the host 12, the cathode voltage of the Zener diode unit 952 is less than its breakdown voltage. At this time, before the output voltage of the second reference voltage source 950 is still greater than the output voltage of the first reference voltage source 910, the output of the second reference voltage source 950 determines the reference voltage Vref output by the reference voltage generating circuit 620. . If the output voltage of the second reference voltage source 950 is less than the output voltage of the first reference voltage source 910, the reference voltage Vref output by the reference voltage generating circuit 620 is determined by the output of the first reference voltage source 910. Therefore, the control unit 630 can control the main power circuit 610 to adjust the level of the output voltage Vo according to the relationship between the level of the output voltage Vo and the level of the reference voltage Vref. That is to say, the voltage regulating circuit 520 can adjust the level of the output voltage Vo according to the output current Io.

Zener diode unit when output current Io is greater than critical current amount Ith The cathode voltage of 952 is greater than its breakdown voltage such that the reference voltage Vref is maintained at a reference voltage relative to the maximum voltage level Vmax due to the collapse of the Zener diode unit 952. Therefore, the control unit 630 can control the main power circuit 610 to maintain the level of the output voltage Vo at the maximum voltage level Vmax according to the relationship between the level of the output voltage Vo and the level of the reference voltage Vref.

In summary, the power adapter 11 in the embodiment of the present invention adjusts the level of the output voltage Vo according to the magnitude of the output current Io. When the host 12 enters the light load state (the output current Io becomes small), the power adapter can correspondingly lower the level of the output voltage Vo. Therefore, the difference between the input voltage and the output voltage of the internal voltage regulator of the host 12 can be reduced, thereby increasing the conversion efficiency of the voltage regulator.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

Io‧‧‧ output current

Ith‧‧‧critical current

Vmax‧‧‧Maximum voltage level

Vmin‧‧‧ minimum voltage level

Vo‧‧‧ output voltage

Claims (24)

An electronic device includes: a host having a power connector; and a power adapter coupled to the power connector to supply an output current and an output voltage to the host, wherein the power adapter is configured according to the power adapter The magnitude of the output current is correspondingly adjusted to the level of the output voltage; wherein the power adapter adjusts the output voltage according to the output current to a maximum voltage level and a minimum voltage level; wherein the output current When the load is 0, the power adapter adjusts the output voltage to the minimum voltage level; wherein when the output current increases to a threshold current amount, the power adapter adjusts the output voltage correspondingly Up to the maximum voltage level; and wherein when the output current is greater than the threshold current amount, the power adapter maintains the level of the output voltage at the maximum voltage level. The electronic device of claim 1, wherein when the output current increases due to the power demand of the host, the power adapter adjusts the level of the output voltage correspondingly; and when the output current is When the power consumption requirement of the host is reduced, the power adapter adjusts the level of the output voltage correspondingly. The electronic device of claim 1, wherein the power adapter comprises: a rectifier circuit for converting an alternating current into a direct current; and a voltage regulating circuit coupled to the rectifier circuit, the voltage regulating circuit use The direct current supplies the output current and the output voltage to the host, and adjusts the level of the output voltage according to the output current. The electronic device of claim 3, wherein the voltage regulating circuit comprises: a main power circuit, receiving the direct current, and providing and adjusting the output voltage according to a control signal; a reference voltage generating circuit providing a reference a voltage, wherein the reference voltage generating circuit adjusts the level of the reference voltage according to the output current; and a control unit coupled to the main power circuit and the reference voltage generating circuit, wherein the level of the output voltage is The control unit provides and adjusts the control signal to the main power supply circuit in relation to the level of the reference voltage. The electronic device of claim 4, wherein the main power circuit comprises: a transformer comprising a primary coil and a secondary coil, wherein the first end of the primary coil receives the direct current, and the secondary coil One end is coupled to a second reference voltage; a switch, the first end of the switch is coupled to the second end of the main coil, the second end of the switch is coupled to a third reference voltage, and the switch is The control end is coupled to the control unit to receive the control signal; and a rectifying and filtering circuit, the input end of the rectifying and filtering circuit is coupled to the second end of the sub coil, and the output end of the rectifying and filtering circuit provides the output voltage The third reference voltage is a first ground voltage, and the second reference voltage is a second ground voltage. The electronic device of claim 5, wherein the rectifying and filtering circuit comprises: a diode, an anode of the diode is coupled to the second end of the secondary coil, and a cathode of the diode is provided The output voltage; and a capacitor, the first end of the capacitor is coupled to the cathode of the diode, and the second end of the capacitor is coupled to the second reference voltage. The electronic device of claim 4, wherein the reference voltage generating circuit comprises: a reference voltage source, providing a second reference voltage relative to a maximum voltage level; and a resistor, the first end of the resistor And coupled to the reference voltage source, the second end of the resistor is coupled to the control unit to provide the reference voltage; a current detecting circuit is coupled to the output end of the main power circuit to detect the output current, and output a a detection circuit; and a comparison circuit, the output end of the comparison circuit is coupled to the second end of the resistor, and the input end of the comparison circuit is coupled to the output end of the current detection circuit, wherein the detection result indicates the output When the current is greater than a threshold current amount, the output end of the comparison circuit is in a high impedance state, and when the detection result indicates that the output current is less than the threshold current amount, the output voltage of the comparison circuit corresponds to the magnitude of the output current Adjustment. The electronic device of claim 4, wherein the reference voltage generating circuit comprises: a first reference voltage source, providing a second reference voltage relative to a minimum voltage level; a diode, an anode of the diode coupled to an output of the first reference voltage source, the diode The cathode is coupled to the output of the reference voltage generating circuit; a capacitor, the first end of the capacitor is coupled to the cathode of the diode, the second end of the capacitor is coupled to a second reference voltage; a detection circuit, coupled to an output current path of the main power circuit to detect the output current, and outputting a detection result; and a second reference voltage source, the output end of the second reference voltage source being coupled to the diode a cathode of the body, wherein an input end of the second reference voltage source is coupled to an output end of the current detecting circuit, wherein when the detecting result indicates that the output current is greater than a threshold current amount, an output end of the second reference voltage source Providing a third reference voltage relative to a maximum voltage level, and when the detection result indicates that the output current is less than the threshold current amount, a voltage of an output end of the second reference voltage source along with the output current Small adjustments to correspond; wherein the second reference voltage is a ground voltage. The electronic device of claim 8, wherein the first reference voltage source comprises: a resistor, the first end of the resistor is coupled to the output end of the main power circuit to receive the output voltage, the resistor The second end is coupled to the output end of the first reference voltage source; and a Zener diode unit, the cathode of the Zener diode unit is coupled to the resistor The second end of the Zener diode unit is coupled to the second reference voltage. The electronic device of claim 8, wherein the current detecting circuit comprises: a transformer comprising a main coil and a sub coil, wherein the main coil is disposed on an output current path of the main power circuit so that The output current flows through the primary coil, and the first end of the secondary coil is coupled to the second reference voltage; a second diode, the anode of the second diode is coupled to the second of the secondary coil The cathode of the second diode is coupled to the output of the current detecting circuit; and a second capacitor, the first end of the second capacitor is coupled to the cathode of the second diode, the second The second end of the capacitor is coupled to the second reference voltage. The electronic device of claim 8, wherein the second reference voltage source comprises: a resistor, the first end of the resistor is coupled to the input end of the second reference voltage source to receive the detection result, a second end of the resistor is coupled to the output end of the second reference voltage source; and a Zener diode unit, the cathode of the Zener diode unit is coupled to the second end of the resistor, the Zener diode The anode of the body unit is coupled to the second reference voltage. The electronic device of claim 4, wherein the control unit comprises: a feedback circuit coupled to the output end of the main power circuit to receive the output voltage, and outputting a response corresponding to the output voltage Voltage feedback; an error amplifier, the inverting input of the error amplifier is coupled to the feedback power The circuit is configured to receive the feedback voltage, and the non-inverting input terminal of the error amplifier is coupled to the reference voltage generating circuit to receive the reference voltage; a photoelectric coupling element, a light emitting portion of the photoelectric coupling element is coupled to the An output of the error amplifier; and a driving circuit, the input end of the driving circuit is coupled to a photo detecting portion of the optocoupler device, and an output end of the driving circuit is coupled to the control end of the main power circuit to provide the And a control signal, wherein the driving circuit correspondingly adjusts the control signal according to a signal of an input end of the driving circuit. A power adapter includes: a rectifier circuit that converts an alternating current into a direct current; and a voltage regulating circuit coupled to the rectifier circuit, the voltage regulating circuit uses the direct current to supply an output current and an output voltage to a host external to the power adapter, and correspondingly adjusting the level of the output voltage according to the output current; wherein the voltage adjusting circuit adjusts the output voltage to a maximum voltage level and a minimum voltage according to the output current Between the levels; wherein when the output current is 0 due to no load, the power adapter adjusts the output voltage to the minimum voltage level; wherein when the output current increases to a critical current amount, The voltage regulating circuit correspondingly increases the output voltage to the maximum voltage level; and wherein when the output current is greater than the threshold current amount, the voltage regulating circuit maintains the level of the output voltage at the maximum voltage level. The power adapter of claim 13, wherein the power adapter When the current is increased due to the power demand of the host, the voltage regulating circuit correspondingly increases the level of the output voltage; and when the output current decreases due to the power demand of the host, the voltage regulating circuit correspondingly decreases The level of this output voltage. The power adapter of claim 13, wherein the voltage regulating circuit comprises: a main power circuit, receiving the direct current, and providing and adjusting the output voltage according to a control signal; a reference voltage generating circuit providing a reference voltage, wherein the reference voltage generating circuit adjusts the level of the reference voltage according to the output current; and a control unit coupled to the main power circuit and the reference voltage generating circuit, wherein the output voltage is accurate The control unit provides and adjusts the control signal to the main power supply circuit in relation to the level of the reference voltage. The power adapter of claim 15, wherein the main power circuit comprises: a transformer comprising a primary coil and a secondary coil, wherein the first end of the primary coil receives the direct current, and the secondary coil The first end is coupled to a second reference voltage; the first end of the switch is coupled to the second end of the main coil, the second end of the switch is coupled to a third reference voltage, and the a control end of the switch is coupled to the control unit to receive the control signal; and a rectifying and filtering circuit, an input end of the rectifying and filtering circuit is coupled to the second end of the sub coil, and an output end of the rectifying and filtering circuit provides the An output voltage; wherein the third reference voltage is a first ground voltage, and the second reference voltage Is a second ground voltage. The power adapter of claim 16, wherein the rectifier filter circuit comprises: a diode, an anode of the diode is coupled to the second end of the secondary coil, and the diode is The cathode provides the output voltage; and a capacitor, the first end of the capacitor is coupled to the cathode of the diode, and the second end of the capacitor is coupled to the second reference voltage. The power adapter of claim 15, wherein the reference voltage generating circuit comprises: a reference voltage source, providing a second reference voltage relative to a maximum voltage level; a resistor, the resistor One end is coupled to the reference voltage source, the second end of the resistor is coupled to the control unit to provide the reference voltage; a current detecting circuit is coupled to the output end of the main power circuit to detect the output current, and Outputting a detection result; and a comparison circuit, the output end of the comparison circuit is coupled to the second end of the resistor, and the input end of the comparison circuit is coupled to the output end of the current detection circuit, wherein when the detection result is expressed When the output current is greater than a threshold current amount, the output end of the comparison circuit is in a high impedance state, and when the detection result indicates that the output current is less than the threshold current amount, the output voltage of the comparison circuit follows the magnitude of the output current And the corresponding adjustment. The power adapter of claim 15, wherein the reference The voltage generating circuit includes: a first reference voltage source, providing a second reference voltage relative to a minimum voltage level; a diode, the anode of the diode is coupled to the output end of the first reference voltage source The cathode of the diode is coupled to the output of the reference voltage generating circuit; a capacitor, the first end of the capacitor is coupled to the cathode of the diode, and the second end of the capacitor is coupled to a second a current detecting circuit, coupled to an output current path of the main power circuit to detect the output current, and outputting a detection result; and a second reference voltage source, the output end of the second reference voltage source is coupled Connected to the cathode of the diode, and the input end of the second reference voltage source is coupled to the output end of the current detecting circuit, wherein the second reference is when the detection result indicates that the output current is greater than a threshold current amount The output of the voltage source provides a third reference voltage relative to a maximum voltage level, and when the detection result indicates that the output current is less than the critical current amount, the output of the second reference voltage source is As the magnitude of the output current is adjusted to correspond; wherein the second reference voltage is a ground voltage. The power adapter of claim 19, wherein the first reference voltage source comprises: a resistor, the first end of the resistor is coupled to the output end of the main power circuit to receive the output voltage, a second end of the resistor coupled to the output of the first reference voltage source; a Zener diode unit having a cathode coupled to the second end of the resistor, the anode of the Zener diode unit being coupled to the second reference voltage. The power adapter of claim 19, wherein the current detecting circuit comprises: a transformer comprising a primary coil and a secondary coil, wherein the primary coil is disposed on an output current path of the main power circuit The first output of the secondary coil is coupled to the second reference voltage; a second diode, the anode of the second diode is coupled to the secondary coil a second end, the cathode of the second diode is coupled to the output of the current detecting circuit; and a second capacitor, the first end of the second capacitor is coupled to the cathode of the second diode, The second end of the second capacitor is coupled to the second reference voltage. The power adapter of claim 19, wherein the second reference voltage source comprises: a resistor, the first end of the resistor is coupled to the input end of the second reference voltage source to receive the detection result The second end of the resistor is coupled to the output end of the second reference voltage source; and a Zener diode unit, the cathode of the Zener diode unit is coupled to the second end of the resistor, the Zener The anode of the diode unit is coupled to the second reference voltage. The power adapter of claim 15, wherein the control unit comprises: a feedback circuit coupled to the output of the main power circuit to receive the output voltage, and output corresponding to the output voltage One feedback voltage; An error amplifier having an inverting input coupled to the feedback circuit to receive the feedback voltage, and a non-inverting input of the error amplifier coupled to the reference voltage generating circuit to receive the reference voltage; An optoelectronic coupling component, a light emitting portion of the optoelectronic coupling component is coupled to the output end of the error amplifier; and a driving circuit, the input end of the driving circuit is coupled to a photo detecting portion of the optoelectronic coupling component, The output end of the driving circuit is coupled to the control end of the main power circuit to provide the control signal, wherein the driving circuit correspondingly adjusts the control signal according to the signal of the input end of the driving circuit. A method for operating a power adapter includes: providing an output current and an output voltage to a host; detecting a magnitude of the output current; and adjusting a level of the output voltage according to the magnitude of the output current; wherein The step of adjusting the output voltage includes: adjusting the output voltage according to the output current to be between a maximum voltage level and a minimum voltage level; wherein the adjusting the output voltage to a maximum voltage level and a minimum voltage The step between the levels includes: when the output current increases due to the power demand of the host, correspondingly increasing the level of the output voltage; when the output current is reduced due to the power demand of the host, the corresponding adjustment Lowering the level of the output voltage; When the output current is 0 due to no load, the output voltage is correspondingly adjusted to the minimum voltage level; when the output current is increased to a threshold current amount, the output voltage is correspondingly increased to the maximum voltage level; And when the output current is greater than the threshold current amount, maintaining the level of the output voltage at the maximum voltage level.