External power supply and method to enhance the output power delivered by an external power supply
The present disclosure provides various embodiments of an external power supply and methods to enhance the output power delivered by an external power supply to a power consuming load. As described in more detail below, the embodiments disclosed herein enable an external power supply to deliver a higher than maximum output power for short periods of time when ambient temperatures within the external power supply are low. As the ambient temperature increases, the embodiments disclosed herein throttle (or incrementally reduce) the output power delivered by the external power supply until the maximum output power specified for the power supply is reached. Although not strictly limited to such, the external power supply may be a Universal Serial Bus (USB)-enabled AC/DC adapter, and more specifically, a USB Power Deliver (USB-PD) AC/DC adapter, in some embodiments.
1. A method to enhance an output power delivered by an external power supply to a power consuming load, wherein the external power supply has a maximum output power rating and comprises a transformer coupled to transform an input power to the output power delivered by the external power supply, wherein the method comprises:
detecting an ambient temperature within the external power supply;
comparing the ambient temperature to a plurality of temperature threshold values; and
determining if current and/or voltage settings for the transformer should be adjusted based on the comparison;
wherein if the method determines that the current and/or voltage settings for the transformer should be adjusted, the method further comprises:
selecting, from a plurality of current/voltage (I/V) curves, an I/V curve corresponding to a lowest temperature threshold value met or exceeded by the ambient temperature; and
using the selected I/V curve to select I/V settings for the transformer that maximize the output power delivered by the external power supply at the ambient temperature.
2. The method as recited in claim 1 , wherein said determining comprises determining the current and/or voltage settings for the transformer should be adjusted if the ambient temperature meets or exceeds at least one the plurality of temperature threshold values.
3. The method as recited in claim 1 , wherein the plurality of I/V curves comprise either 3 or 4 IV curves, and wherein each of plurality of I/V curves corresponds to a different one of the plurality of temperature threshold values.
4. The method as recited in claim 1 , wherein one or more of the plurality of I/V curves are used to select I/V settings that enable the transformer to provide more output power than the maximum output power rating specified for the external power supply when the ambient temperature is equal to or less than 70° F.
5. The method as recited in claim 1 , wherein the plurality of I/V curves provide over temperature protection (OTP), under voltage protection (UVP), over current protection (OCP) and over power protection (OPP) for the external power supply.
6. The method as recited in claim 1 , further comprising:
repeating the steps of detecting the ambient temperature within the external power supply and comparing the ambient temperature to the plurality of temperature threshold values to determine if the current and/or voltage settings for the transformer should be readjusted based on the comparison;
wherein each time the ambient temperature meets or exceeds a new temperature threshold value, the method further comprises selecting a new I/V curve corresponding to the new temperature threshold value to change the I/V curve supported by the external power supply over time, as the ambient temperature rises.
7. The method as recited in claim 1 , further comprising:
communicating the selected I/V settings and the output power of the external power supply to the power consuming load; and
re-negotiating a new power contract to establish a new power supply relationship between the external power supply and the power consuming load.
8. An external power supply coupled to convert alternating current (AC) power received from an AC power source to a direct current (DC) output current supplied to a power consuming load, where a maximum output power rating is specified for the external power supply, and wherein the external power supply comprises:
a rectifier circuit coupled to receive the AC power from the AC power source and configured to convert the AC power to DC power;
a transformer coupled to receive a DC input current from the rectifier circuit on a primary side of the transformer, and configured to provide a DC output current and a DC output voltage on a secondary side of the transformer; and
a controller coupled to monitor the DC output current and the DC output voltage, along with an ambient temperature detected within the external power supply, wherein the controller is configured to dynamically determine and select current/voltage (I/V) settings for the transformer that maximize an output power delivered by the external power supply to the power consuming load based on an internal thermal headroom within the external power supply.
9. The external power supply as recited in claim 8 , wherein the controller utilizes an adaptive I/V control method, which dynamically determines and selects the I/V settings for the transformer based on the DC output current, the DC output voltage and the ambient temperature.
10. The external power supply as recited in claim 9 , wherein the I/V settings selected by the adaptive I/V control method enable the transformer to deliver more output power than the maximum output power rating specified for the external power supply when the ambient temperature is equal to or less than 70° F.
11. The external power supply as recited in claim 10 , wherein as the ambient temperature increases, the controller utilizes the adaptive I/V control method to select new I/V settings that reduce the output power provided by the transformer until the maximum output power rating specified for the external power supply is reached.
12. The external power supply as recited in claim 8 , wherein the controller comprises a micro-controller unit (MCU) digital core that is configured to store an adaptive I/V control algorithm, wherein when the external power supply is in use, the MCU digital core executes program instructions within the adaptive I/V control algorithm to:
monitor the ambient temperature detected within the external power supply;
compare the ambient temperature to a plurality of temperature threshold values;
select, from a plurality of I/V curves, an I/V curve corresponding to a lowest temperature threshold value met or exceeded by the ambient temperature; and
use the selected I/V curve to select I/V settings for the transformer that maximize the output power delivered by the external power supply at the ambient temperature.
13. The external power supply as recited in claim 12 , wherein the plurality of I/V curves comprise either 3 or 4 I/V curves, and wherein each of plurality of I/V curves corresponds to a different one of the plurality of temperature threshold values.
14. The external power supply as recited in claim 12 , wherein one or more of the plurality of I/V curves are used by the MCU digital core to select I/V settings for the transformer that enable the external power supply to provide more output power than the maximum output power rating when the ambient temperature is equal to or less than 70° F.
15. The external power supply as recited in claim 12 , wherein the plurality of I/V curves provide over temperature protection (OTP), under voltage protection (UVP), over current protection (OCP) and over power protection (OPP) for the external power supply.
16. The external power supply as recited in claim 12 , wherein the controller further comprises:
a first comparator coupled to sense the DC output voltage;
a second comparator coupled to compare the DC output voltage sensed by the first comparator to a current threshold value selected by the MCU digital core; and
a third comparator may be coupled to compare a feedback voltage provided to the controller to a voltage threshold value selected by the MCU digital core.
17. The external power supply as recited in claim 16 , wherein the controller further comprises:
a first N-channel metal-oxide-semiconductor (NMOS) transistor having a gate terminal coupled to the output of the second comparator, a source terminal coupled to a ground pin of the controller and a drain terminal coupled to an optocoupler pin of the controller;
wherein when the DC output voltage is less than the current threshold value selected by the MCU digital core, the second comparator outputs a logic low value to the gate terminal of the first NMOS transistor, which turns the first NMOS transistor off and causes the DC output current to be increased.
18. The external power supply as recited in claim 16 , wherein the controller further comprises:
a second N-channel metal-oxide-semiconductor (NMOS) transistor having a gate terminal coupled to the output of the third comparator, a source terminal coupled to a ground pin of the controller and a drain terminal coupled to an optocoupler pin of the controller;
wherein when the feedback voltage is less than the voltage threshold value selected by the MCU digital core, the third comparator outputs a logic low value to the gate terminal of the second NMOS transistor, which turns the second NMOS transistor off and causes the DC output voltage to be increased.
19. The external power supply as recited in claim 16 , wherein each time the ambient temperature meets or exceeds a new one of the temperature threshold values, the MCU digital core executes the program instructions within the adaptive I/V control algorithm to select a new current threshold value and/or a new voltage threshold value corresponding to that temperature threshold value to change the I/V curve supported by the external power supply over time, as the ambient temperature rises.
20. The external power supply as recited in claim 12 , wherein once the I/V settings are selected, the MCU digital core executes the program instructions within the adaptive I/V control algorithm to:
communicate the selected I/V settings and the output power of the external power supply to the power consuming load; and
re-negotiate a new power contract to establish a new power supply relationship between the external power supply and the power consuming load.
21. The external power supply as recited in claim 20 , wherein the MCU digital core uses Universal Serial Bus (USB) Power Delivery (PD) messages to communicate the selected I/V settings and the output power of the external power supply to the power consuming load and to re-negotiate the new power contract.