DE-112024002932-T5 - INTERFACE CONTROL OF A FED DEVICE

DE112024002932T5DE 112024002932 T5DE112024002932 T5DE 112024002932T5DE-112024002932-T5

Abstract

An interface control for a powered device (PD) is provided, including a switch and a control circuit. The switch controls the current to a PD from a power supply unit (PSE). The PD draws power from a network cable carrying data, and the PSE supplies power to the network cable. The PD also draws power from an auxiliary power source. The control circuit detects a switchover from the auxiliary power source to the PSE as the power source. The control circuit turns on the switch to control the current to a short-circuit current limit, greater than the PD's inrush current limit, for a duration less than the short-circuit time limit, to charge a buffer capacitor in the PD. The control circuit then fully turns on the switch to allow current to flow to the PD.

Inventors

PEKER ARKADIY
DARSHAN YAIR
JACUBOVSKI MIGUEL

Assignees

MICROCHIP TECH INC

Dates

Publication Date: 20260507
Application Date: 20240702
Priority Date: 20240104

Claims (18)

Interface control of a powered device, comprising: a switch for controlling the current to a powered device from a power supply unit that provides power to the powered device via a network cable, wherein the powered device is also configured to receive power from an auxiliary power source; and control circuitry configured at least to: detect a switchover from the auxiliary power source to the power supply unit as the power source for the powered device; at least in response to the detection of the switchover from the auxiliary power source to the power supply unit as the power source for the powered device, control the switch to control the current to the powered device from the power supply unit to a short-circuit current limit for a duration less than a short-circuit time limit in order to charge a buffer capacitor of the powered device, wherein this short-circuit current limit is greater than a starting inrush current limit of the powered device; and subsequently, to control the switch to control the current to the powered device from the power supply unit to the short-circuit current limit level for a duration that is less than a short-circuit time limit, fully opening the switch, in order to allow the current to flow from the power supply unit to the powered device.
Interface control of a powered device according to Claim 1 , wherein, before the switch is fully turned on to allow current to flow from the power supply device to the powered device, after the current to the powered device from the power supply device has been controlled to the short-circuit current limit level for a duration less than a short-circuit time limit, the control circuit is designed to detect that a charge level of the buffer capacitor is at least equal to a threshold charge level.
Interface control of a powered device according to Claim 2 , wherein the control circuit is designed to detect that the charge level of the buffer capacitor is at least equal to the threshold charge level in response to a measurement of a voltage drop across the switch.
Interface control of a powered device according to Claim 1 , wherein, before the switch is fully opened to allow current to flow from the power supply device to the powered device, and after controlling the current to the powered device from the power supply device to the short-circuit current limit level for a duration less than a short-circuit time limit, the control circuit is designed to: detect that a charge level of the buffer capacitor is below the threshold charge level; at least in part in response to detecting that the charge level of the buffer capacitor is below the threshold charge level, switch off a power converter of the powered device; following the switch-off of the power converter, actuate the switch to control the current from the power supply device to the starting inrush current limit of the powered device in order to charge the buffer capacitor; detect that the charge level of the buffer capacitor is at least equal to the threshold charge level; and at least partly in response to the recognition that the charge level of the buffer capacitor corresponds at least to the threshold charge level, switching on the power converter.
Interface control of a powered device according to Claim 1 , wherein during an inrush current stage the control circuit is designed to: switch on the switch to control the current from the power supply device to the inrush current limit of the powered device in order to charge the buffer capacitor; and subsequently to control the current from the power supply device to the inrush current limit of the powered device in order to charge the buffer capacitor, fully switch on the switch to allow the current from the power supply device to flow to the powered device.
Interface control of a powered device according to Claim 1 , wherein the switching is a second switching, and the control circuit is designed to: detect a first switching from the power supply device to the auxiliary power source as the power source for the powered device; and at least in part as a reaction to the detection of the first switchover from the power supply unit to the auxiliary power source as the power source for the powered device, switching off the switch to interrupt the current to the powered device from the power supply unit.
Powered device comprising: a power converter for providing a regulated voltage to a load from a power source, wherein the powered device is configured to receive current from a power supply unit that provides current to the powered device via a network cable, and wherein the powered device is further configured to receive current from an auxiliary power source; a buffer capacitor coupled to an input of the power converter; and an interface controller of a powered device for controlling the current to the powered device from the power supply unit, the interface controller of a powered device comprising at least the following: detecting a switch from the auxiliary power source to the power supply unit as the power source for the powered device; at least in part in response to the detection of the switchover from the auxiliary power source to the power supply unit as the power source for the powered device, controlling the current to a short-circuit current limit for a duration less than a short-circuit time limit in order to charge the buffer capacitor, the short-circuit current limit being greater than a starting current limit of the powered device; and subsequently, controlling the current to the short-circuit current limit for a duration less than the short-circuit time limit, allowing the current to flow freely from the power supply unit to the powered device.
Powered device according to Claim 7 , wherein, before the interface control of the powered device allows the current to flow freely from the power supply device to the powered device, after the control of the current to the powered device from the power supply device to the short-circuit current limit level, for a duration less than a short-circuit time limit, the interface control of the powered device is designed to detect that a charge level of the buffer capacitor corresponds to at least a threshold charge level.
Powered device according to Claim 8 , wherein the interface control of the powered device is designed to detect that the charge level of the buffer capacitor is at least equal to the threshold charge level in response to a measurement of a voltage drop across a switch.
fed device according to Claim 7 , wherein, before the interface control of the powered device allows current to flow freely from the power supply unit to the powered device, and after controlling the current to the powered device from the power supply unit to the short-circuit current limit level, for a duration less than a short-circuit time limit, the interface control of the powered device is designed to: detect that the charge level of the buffer capacitor is below the threshold charge level; at least in part in response to detecting that the charge level of the buffer capacitor is below the threshold charge level, switch off the power converter of the powered device; following the switch-off of the power converter of the powered device, control the current from the power supply unit to the inrush current limit of the powered device in order to charge the buffer capacitor; detect that the charge level of the buffer capacitor is at least equal to the threshold charge level; and at least partly in response to the recognition that the charge level of the buffer capacitor corresponds at least to the threshold charge level, switching on the power converter.
fed device according to Claim 7 , wherein during an inrush current stage the interface control of the powered device is designed to: control the current from the power supply device to the powered device to the inrush current limit of the powered device in order to charge the buffer capacitor; and subsequently to control the current from the power supply device to the powered device to the inrush current limit of the powered device in order to charge the buffer capacitor, allowing the current to flow freely from the power supply device to the powered device.
fed device according to Claim 7 , where the switching is a second switching is and the interface control of a powered device is designed to: detect an initial switchover from the power supply unit to the auxiliary power source as the power source for the powered device; and, at least in part, in response to the detection of the initial switchover from the power supply unit to the auxiliary power source as the power source for the powered device, interrupt the current to the powered device from the power supply unit.
A method comprising: detecting a switch from an auxiliary power source to a power supply unit as the power source for a powered device in a Power-over-Ethernet system; at least in part in response to the detection of the switch from the auxiliary power source to the power supply unit as the power source for the powered device, controlling the current to the powered device from the power supply unit to a short-circuit current limit for a duration less than a short-circuit time limit in order to charge a buffer capacitor of the powered device, wherein the short-circuit current limit is greater than a starting current limit of the powered device; and subsequently, to control the current to the powered device from the power supply unit to the short-circuit current limit for a duration less than a short-circuit time limit, allowing the current to flow freely from the power supply unit to the powered device.
Procedure according to Claim 13 , wherein, before allowing the current to flow freely from the power supply device to the powered device, after controlling the current to the powered device from the power supply device to the short-circuit current limit level for a duration less than a short-circuit time limit, the method includes detecting that a charge level of the buffer capacitor is at least equal to a threshold charge level.
Procedure according to Claim 14 , wherein the charge level of the buffer capacitor is at least equal to the threshold charge level and is detected in response to a measurement of a voltage drop across a switch.
Procedure according to Claim 13 , wherein, before allowing current to flow freely from the power supply device to the powered device, and after controlling the current to the powered device from the power supply device to the short-circuit current limit level for a duration less than a short-circuit time limit, the method comprises: detecting that the charge level of the buffer capacitor is below the threshold charge level; at least in part in response to detecting that the charge level of the buffer capacitor is below the threshold charge level, switching off a power converter of the powered device; after switching off the power converter of the powered device, controlling the current to the starting inrush current limit of the powered device in order to charge the buffer capacitor; detecting that the charge level of the buffer capacitor is at least equal to the threshold charge level; and at least partly in response to the recognition that the charge level of the buffer capacitor corresponds at least to the threshold charge level, switching on the power converter.
Procedure according to Claim 13 , wherein during an inrush current stage the method comprises: controlling the current from the power supply device to the powered device to the inrush current limit of the powered device in order to charge the buffer capacitor; and subsequently, to control the current from the power supply device to the powered device to the inrush current limit of the powered device in order to charge the buffer capacitor, allowing the current to flow freely from the power supply device to the powered device.
Procedure according to Claim 13 , wherein the switching is a second switching, and the method comprises: detecting a first switching from the power supply device to the auxiliary power source as the power source for the powered device; and at least partially in response to the detection of the first switching from the power supply device to the auxiliary power source as the power source for the powered device, interrupting the power to the powered device from the power supply device.

Description

REFERENCE TO RELATED REGISTRATION(S) The present application claims priority over the provisional application US patent application no. 63/525,815 titled: Change-Over from Auxiliary Power in a Power over Ethernet System, submitted July 10, 2023 , and non-provisional US patent application no. 18/404,554 , submitted on January 4, 2024, entitled: Powered Device Interface Controller, the contents of which are hereby incorporated in their entirety by reference. TECHNOLOGICAL AREA The present disclosure relates generally to Power-over-Ethernet (PoE) and in particular to the implementation of auxiliary power in a PoE system. BACKGROUND Power over Ethernet (PoE) is a technology that allows electrical power and data to be transmitted over a standard Ethernet network cable. It eliminates the need for separate power cables, enabling devices to receive both power and network connectivity over a single Ethernet cable. There are several versions of PoE. IEEE 802.3af is the original PoE standard. IEEE 802.3at is a newer standard that provides higher power output than IEEE 802.3af. IEEE 802.3bt is the latest standard and can deliver even higher power levels. Power over Ethernet (PoE) allows devices such as Internet Protocol cameras (IP cameras), wireless access points, Voice over IP phones (VoIP phones), and other networked devices to be powered directly via the Ethernet infrastructure. This simplifies the installation and deployment of these devices, especially in situations where power outlets may not be readily available. PoE works by using wires in the Ethernet cable to transmit electrical power along with data signals. This is achieved by injecting power into the cable at a power supply unit (PSE), which may be located at a PoE-enabled switch or a PoE midspan injector. The power is then drawn from a powered device interface (PD interface) located at the power- and data-receiving PD. The PD may include a power converter, typically a DC-DC converter, to convert the received power from the PD interface into a suitable voltage level for the PD; and the PD may include a buffer capacitor to smooth out voltage ripples or fluctuations caused by variations at the power converter's input. Many PoE applications also use auxiliary power sources, such as an AC-powered wall adapter (WA) connected to the PD. In these applications, the auxiliary power can supplement or replace the power supplied over Ethernet. PoE can then provide redundancy and backup power for the PD. SUMMARY In many PoE systems, the PD draws no significant current from the PSE when an auxiliary power supply is connected to the PD. Conversely, the PD draws current from the PSE when the auxiliary power supply is disconnected. These operations can be managed with a switch at the PD, such as a transistor in series with the current path from the PSE to the PD. When the auxiliary power supply is connected, the switch might not be able to disconnect the PD immediately before it draws significant current from the PSE, thus enabling a seamless transition from the PSE to the auxiliary power supply as the PD's power source. A seamless transition from the auxiliary power supply to the PSE is also advantageous, and in this case, the switch might need to turn on more quickly to prevent the voltage at the PD from dropping below an undervoltage lockout (UVLO) level. Seamless switching to the PSE from the auxiliary power source can be achieved by continuously operating the PD's power converter. In cases where the auxiliary power source voltage is higher than the PSE voltage, the PD's buffer capacitor can simply discharge until it reaches the PSE voltage. However, in other cases, the auxiliary power source voltage is lower than the PSE voltage. In these other cases, the buffer capacitor may need to be charged to the PSE voltage. In many PoE systems, the PD charges the buffer capacitor during a startup current stage by controlling a switch on the PD interface to limit the current from the PSE to the PD to a startup current limit (e.g., up to 400 mA). However, if the auxiliary power source voltage is lower than the PSE voltage, the PD can enter inrush current mode, i.e., switch to the inrush current stage to charge the buffer capacitor when the auxiliary power source is disconnected. In the inrush current stage, the PD can use the starting inrush current limit, but if the If the power converter current exceeds the inrush current limit, the buffer capacitor can discharge, causing the power converter to shut down. This can occur with PoE Type 3 and Type 4, which allow power outputs of up to 60 watts and 90 watts, respectively, with a power converter current of up to 1.93 A. The switch and control circuitry of the PD interface can be collectively referred to as the PD interface controller. Exemplary implementations of the present disclosure are aimed at implementing auxiliary power in a PoE system. According to exemplary implementations, when switching from an auxiliary power source to