US-12620998-B2 - Methods and circuits for electrical power supply

US12620998B2US 12620998 B2US12620998 B2US 12620998B2US-12620998-B2

Abstract

A circuit includes at least one coupling node configured to be coupled, via a cable, to a load to transmit a supply voltage thereto. The circuit includes test circuitry configured to sense at least one sensing signal indicative of a value of the cable impedance and/or of the cable voltage across the cable, to perform a comparison between the at least one sensing signal and at least one threshold indicative either of a threshold resistance value for the cable impedance or indicative of a threshold voltage value for the cable voltage, produce a comparison signal as a result of the comparison.

Inventors

Alberto Bianco
Francesco CIAPPA
Donato BONDETTI

Assignees

STMICROELECTRONICS S.R.L.

Dates

Publication Date: 20260505
Application Date: 20240117
Priority Date: 20230120

Claims (13)

1 . A circuit, comprising: at least one coupling node configured to be coupled, via a cable, to a load to transmit a supply voltage thereto, the cable having a cable impedance and configured to carry a cable voltage; and test circuitry coupled to the at least one coupling node, the test circuitry configured to: sense at least one sensing signal indicative of a value of the cable impedance and/or of a cable voltage across the cable; perform a comparison between the at least one sensing signal and at least one threshold indicative either of a threshold resistance value for the cable impedance or indicative of a threshold voltage value for the cable voltage; produce a comparison signal as a result of the comparison, the comparison signal having a first logic value or a second logic value, as a result of the at least one sensing signal reaching or failing to reach the at least one threshold; and assert a flag signal based on the logic value of the comparison signal, the flag signal being indicative of the value of the cable impedance being lower than the threshold resistance value or being indicative of a cable voltage across the wired cable being greater than the threshold voltage value, wherein the test circuit includes: an I/O node configured to provide the sensing signal; at least one Zener diode interposed to the at least one resistive element of the coupling circuit and the I/O node; a capacitive element coupled between ground and the I/O node; an analog-to-digital converter circuit coupled to the I/O node to sense the sensing signal therefrom, the analog-to-digital converter circuit configured to perform the comparison and to produce the comparison signal based on the comparison; and a logic unit coupled to the ADC circuit to receive the comparison signal from the analog-to-digital converter circuit, wherein the ADC circuit is configured to produce the comparison signal having the first logic value or the second logic value based on the at least one sensing signal reaching or failing to reach the at least one threshold and the logic unit is configured to assert the flag signal based on the logic value of the comparison signal.
2 . The circuit of claim 1 , wherein the test circuitry includes: a digital buffer circuit coupled to the logic unit and to the I/O node, the digital buffer circuit configured to receive a drive signal from the logic unit and to apply a first voltage level or a second voltage level to the I/O node in response to the logic unit asserting the drive signal with a first logic value or a second logic value, wherein the test circuitry is configured to: assert the drive signal with the first logic value during a first time-interval to initiate charging the capacitive element; after lapse of the first time-interval, leave floating the drive signal during a second time interval to initiate discharging of the capacitive element; assert the drive signal after lapse of the second time-interval to reset the capacitive element to a discharged state; perform the comparison between the at least one sensing signal and at least one threshold indicative of a threshold resistance value for the cable impedance during the discharge of the capacitive element at lapse of the second time interval and to produce the comparison signal as a result of the comparison, the comparison signal having a first logic value or a second logic value based on the at least one sensing signal reaching or failing to reach the at least one threshold; and assert the flag signal based on the logic value of the comparison signal being indicative of the value of the cable impedance being lower than the threshold resistance value.
3 . The circuit of claim 2 , further comprising at least one resistive element coupled to the test circuitry.
4 . The circuit of claim 1 , comprising: a digital buffer coupled to the logic unit and to the I/O node, the digital buffer circuit configured to receive a drive signal from the logic unit and to apply a first voltage level or a second voltage level to the I/O node based on the logic unit asserting the drive signal with a first logic value or a second, logic value, wherein the test circuitry is configured to: assert the drive signal with the first logic value during a first time-interval to initiate charging the capacitive element; leave floating the drive signal after lapse of the first time-interval, to initiate discharging of the capacitive element; perform the comparison between the at least one sensing signal and at least one threshold indicative of a threshold resistance value for the cable impedance and to produce the comparison signal as a result of the comparison, the comparison signal having a first logic value logic value or a second logic value, as a result of the at least one sensing signal reaching, resp. failing to reach, the at least one threshold; in response to the comparison signal having the second logic value, calculate a decay time interval between a first time instant of assertion of the drive signal and a second time instant at which the comparison signal transitions from the first logic value to the second logic value; compute a value of the cable resistance based on the calculated decay time interval; and provide the computed cable resistance value to a user circuit.
5 . The circuit of claim 1 , wherein the cable is compliant with the universal serial bus standard.
6 . A method, comprising: coupling at least one coupling node, via a cable, to a load to transmit a supply voltage thereto, the cable having a cable impedance and configured to carry a cable voltage; sensing at least one sensing signal indicative of a value of the cable impedance or of the cable voltage across the cable; performing a comparison between the at least one sensing signal and at least one threshold indicative either of a threshold resistance value for the cable impedance or indicative of a threshold voltage value for the cable voltage; producing a comparison signal as a result of the comparison, the comparison signal having a first logic value or a second logic value based on the at least one sensing signal reaching or failing to reach the at least one threshold; asserting a flag signal based on the logic value of the comparison signal, the asserted flag signal being indicative of the value of the cable impedance being lower than the threshold resistance value, or being indicative of a cable voltage across the wired cable being greater than the threshold voltage value; and asserting a drive signal with the first logic value during a first time-interval; after lapse of the first time-interval, leaving the drive signal floating during a second time interval; asserting the drive signal after lapse of the second time-interval; performing the comparison between the at least one sensing signal and at least one threshold indicative a threshold resistance value for the cable impedance during the discharge of the capacitive element at lapse of the second time interval, producing the comparison signal as a result of the comparison, the comparison signal having a first logic value or a second logic value, as a result of the at least one sensing signal reaching or failing to reach, the at least one threshold; and asserting the flag signal based on the logic value of the comparison signal being indicative of the value of the cable impedance being lower than the threshold resistance value.
7 . The method of claim 6 , comprising: asserting the drive signal with the first value during a first time-interval; initiating discharging of the capacitive element by leaving the drive signal floating after lapse of the first time-interval; performing the comparison between the at least one sensing signal and at least one threshold indicative a threshold resistance value for the cable impedance and producing the comparison signal as a result of the comparison, the comparison signal having a first logic value or a second logic value, as a result of the at least one sensing signal reaching or failing to reach the at least one threshold; in response to the comparison signal having the second logic value, calculating a decay time interval between a first time instant of assertion of the drive signal and a second time instant at which the comparison signal transitions from the first logic value to the second logic value; computing a value of the cable resistance based on the calculated decay time interval; and providing the computed cable resistance value to a user circuit.
8 . The method of claim 6 , wherein the cable is compliant with the universal serial bus standard.
9 . A device, comprising: a transmission interface including: a first coupling node configured to be coupled to a cable; a sensing circuit coupled to the first coupling node and configured to sense an electrical quantity of the cable via the first coupling node, wherein the sensing circuit includes a first resistor coupled to the first coupling node and a Zener diode coupled to the first resistor; a testing circuit coupled to the sensing circuit and configured to provide a signal indicative of an operational condition of the cable based on the electrical quantity; and a control circuit coupled to the testing circuit and configured to drive the testing circuit block to perform a test on the coupling node and to receive the signal from the testing circuit based on the test, wherein the control circuit includes a single bit ADC configured to receive the signal from the testing circuit, a logic circuit coupled to an output of the single-bit ADC and configured to assert a flag indicative of a fault in the cable based on the signal, and a tri-state buffer including an input coupled to the logic circuit and an output coupled to the input of the single-bit ADC.
10 . The device of claim 9 , wherein the transmission interface includes a second coupling node configured to be coupled to the cable, wherein the sensing circuit includes a second resistor coupled between the second coupling node and the first resistor.
11 . The device of claim 9 , wherein the testing circuit includes a capacitor coupled between the Zener diode and ground.
12 . The device of claim 11 , wherein the testing circuit includes a limiting resistor coupled to the capacitor and the Zener diode.
13 . The device of claim 9 , comprising: a plug configured to be coupled to a socket to receive an AC voltage; and an AC/DC converter coupled to the plug to receive the AC voltage and to provide a supply voltage based on the AC voltage; wherein the transmission interface is coupled to the AC/DC converter to receive the supply voltage therefrom and is configured to transmit the supply voltage to a load via the cable.

Description

BACKGROUND Technical Field The description relates to methods and circuits for providing an electrical power supply to load circuitry. For instance, the description relates to detecting fault conditions such as low impedance and/or overvoltage which may occur in input/output (briefly, I/O) cables and circuitry during power supply operations. One or more embodiments may be applied to connectors for electrical power supply designed according to the Universal Serial Bus (briefly, USB) standard, such as type-C USB connectors, for instance. Description of the Related Art Over time, USB has evolved from being a data interface capable of supplying limited power to becoming a power provider with an auxiliary data interface. While connected to a power supply, a USB cable for power delivery (briefly, USB-PD) may accidentally be damaged, for instance an internal short circuit among internal wires may be the due to pets chewing on the cable or to a conductive liquid (such as milk, for instance) accidentally wetting the free end of the cable. In these scenarios, there is an interest in controlling the power delivery in order to limit damages to the cable and the power supply. BRIEF SUMMARY One or more embodiments contribute in addressing the issues discussed in the foregoing. One or more embodiments may be equipped on a (e.g., USB) power adapter for battery-powered electronic devices, for instance. One or more embodiments facilitate detecting an impedance across USB cables using a single node, such as a general purpose I/O node. One or more embodiments advantageously use relatively simple means to adapt to any microcontroller device. One or more embodiments facilitate interrupting power delivery in response to fault detection (e.g., due to reduced impedance or overvoltage). One or more embodiments envisage periodically testing the USB cable conditions without affecting normal operation. In one embodiment, a circuit includes at least one coupling node configured to be coupled, via a cable, to a load to transmit a supply voltage thereto, the cable having a cable impedance and configured to carry a cable voltage and test circuitry coupled to the at least one coupling node. The test circuitry is configured to sense at least one sensing signal indicative of a value of the cable impedance and/or of a cable voltage across the cable and perform a comparison between the at least one sensing signal and at least one threshold indicative either of a threshold resistance value for the cable impedance or indicative of a threshold voltage value for the cable voltage. The test circuitry is configured to produce a comparison signal as a result of the comparison, the comparison signal having a first logic value or a second logic value, as a result of the at least one sensing signal reaching or failing to reach the at least one threshold and assert a flag signal based on the logic value of the comparison signal, the flag signal being indicative of the value of the cable impedance being lower than the threshold resistance value or being indicative of a cable voltage across the wired cable being greater than the threshold voltage value. In one embodiment, a method includes coupling at least one coupling node, via a cable, to a load to transmit a supply voltage thereto, the cable having a cable impedance and configured to carry a cable voltage and sensing at least one sensing signal indicative of a value of the cable impedance or of the cable voltage across the cable. The method includes performing a comparison between the at least one sensing signal and at least one threshold indicative either of a threshold resistance value for the cable impedance or indicative of a threshold voltage value for the cable voltage and producing a comparison signal as a result of the comparison, the comparison signal having a first logic value or a second logic value based on the at least one sensing signal reaching or failing to reach the at least one threshold. The method includes asserting a flag signal based on the logic value of the comparison signal, the asserted flag signal being indicative of the value of the cable impedance being lower than the threshold resistance value, or being indicative of a cable voltage across the wired cable being greater than the threshold voltage value. In one embodiment, a device includes a transmission interface. The transmission interface includes a first coupling node configured to be coupled to a cable, a sensing circuit coupled to the first coupling node and configured to sense an electrical quantity of the cable via the first coupling node, and a testing circuit coupled to the sensing circuit and configured to provide a signal indicative of an operational condition of the cable based on the electrical quantity. The interface includes a control circuit coupled to the testing circuit and configured to drive the testing circuit block to perform a test on the coupling node and to receive the signal from the testing circui