US-20260126840-A1 - CONTROL CIRCUIT FOR UNIVERSAL SERIAL BUS

US20260126840A1US 20260126840 A1US20260126840 A1US 20260126840A1US-20260126840-A1

Abstract

A control circuit for a universal serial bus (USB) is provided. The control circuit includes a blocking switch, a current source circuit, a discharge circuit, and a controller. The blocking switch is connected between a power supply terminal of the USB and a bus power terminal of the USB. Before supplying power to the bus power terminal, the controller turns off the blocking switch and controls the discharge circuit to pull down an output voltage value at the bus power terminal. When the output voltage value is lower than or equal to a set voltage value, the discharge circuit stops pulling down the output voltage value, and controls the current source circuit to provide a test current to the bus power terminal. The controller obtains a resistance value at the bus power terminal based on the output voltage value and a current value of the test current.

Inventors

Chih Hsiang CHUNG
Rong-Jie Tu

Assignees

POWER FOREST TECHNOLOGY CORPORATION

Dates

Publication Date: 20260507
Application Date: 20241205
Priority Date: 20241105

Claims (10)

1 . A control circuit for a universal serial bus, comprising: a blocking switch electrically connected between a power supply terminal of the universal serial bus and a bus power terminal of the universal serial bus; a current source circuit electrically connected between the power supply terminal and the bus power terminal; a discharge circuit electrically connected between the bus power terminal and a reference low voltage; and a controller electrically connected to a control terminal of the blocking switch, the current source circuit, and the discharge circuit, wherein before supplying power to the bus power terminal, the controller turns off the blocking switch, and controls the discharge circuit to pull down an output voltage value at the bus power terminal, wherein in response to the output voltage value being lower than or equal to a first set voltage value, the controller controls the discharge circuit to stop pulling down the output voltage value, and controls the current source circuit to provide a test current to the bus power terminal, and wherein the controller obtains a resistance value at the bus power terminal according to the output voltage value and a current value of the test current.
2 . The control circuit according to claim 1 , wherein the current source circuit comprises: a first current source, wherein a first terminal of the first current source is electrically connected to the power supply terminal, and the first current source is configured to generate the test current; and a first switch electrically connected between a second terminal of the first current source and the bus power terminal.
3 . The control circuit according to claim 2 , wherein the discharge circuit comprises: a second current source, wherein a first terminal of the second current source is electrically connected to the bus power terminal, and the second current source is configured to generate a discharge current; and a second switch electrically connected between a second terminal of the second current source and the reference low voltage.
4 . The control circuit according to claim 3 , wherein before supplying power to the bus power terminal, the controller turns off the blocking switch, turns off the first switch, and turns on the second switch.
5 . The control circuit according to claim 3 , wherein in response to the output voltage value being lowered to the first set voltage value, the controller turns off the blocking switch, turns off the second switch, and turns on the first switch.
6 . The control circuit according to claim 1 , wherein during a period when the test current is provided to the bus power terminal, in response to the output voltage value being higher than a second set voltage value, the controller turns on the blocking switch.
7 . The control circuit according to claim 1 , further comprising: a comparator electrically connected to the bus power terminal and the controller, and configured to receive the output voltage value and the first set voltage value, wherein before supplying power to the bus power terminal, the comparator compares the output voltage value and the first set voltage value to generate a comparison signal.
8 . The control circuit according to claim 1 , wherein: before supplying power to the bus power terminal, the controller receives a comparison signal, and in response to the comparison signal indicating that the output voltage value is higher than the first set voltage value, the controller controls the discharge circuit to pull down the output voltage value, and controls the current source circuit to stop providing the test current to the bus power terminal.
9 . The control circuit according to claim 8 , wherein in response to the comparison signal indicating that the output voltage value is lower than or equal to the first set voltage value, the controller controls the discharge circuit to stop pulling down the output voltage value, and controls the current source circuit to provide the test current to the bus power terminal.
10 . The control circuit according to claim 1 , wherein: the control circuit communicates with a power receiving device connected to the bus power terminal to obtain a communication resistance value, and the controller determines whether to control the current source circuit to provide the test current to the bus power terminal according to the communication resistance value.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the priority benefit of Taiwan application serial no. 113211999, filed on November 5, 2024. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. BACKGROUND Technical Field The disclosure relates to a control circuit, and particularly relates to a control circuit for a universal serial bus (USB). Description of Related Art A universal serial bus (USB) includes a bus power terminal (Vbus) and a ground terminal (GND). When the USB is abnormal or incorrectly used, the bus power terminal and the ground terminal of the USB have an abnormal low resistance value. The low resistance value is, for example, tens of ohms (Ω). Such the abnormal low resistance value does not cause a short circuit between the bus power terminal and the ground terminal. However, the local thermal energy generated by the current based on the abnormal low resistance value is sufficient to damage the structure of the USB (such as the tongue plate of the USB). Besides, if a resistance value between the bus power terminal and a power receiving device is low, the normal low resistance value between the bus power terminal and a power receiving device may be judged as the abnormal low resistance value, so as to stop the USB providing a power to the power receiving device. Therefore, how to detect the resistance value at the bus power terminal is one of the issues that need to be worked on in this field. SUMMARY The disclosure provides a control circuit for a universal serial bus (USB), which can detect the resistance value at the bus power terminal. In an embodiment of the disclosure, a control circuit includes a blocking switch, a current source circuit, a discharge circuit, and a controller. The blocking switch is electrically connected between a power supply terminal of a USB and a bus power terminal of the USB. The current source circuit is electrically connected between the power supply terminal and the bus power terminal. The controller is electrically connected to a control terminal of the blocking switch, the current source circuit, and the discharge circuit. Before supplying power to the bus power terminal, the controller turns off the blocking switch, and controls the discharge circuit to pull down an output voltage value at the bus power terminal. In response to the output voltage value being lower than or equal to a first set voltage value, the controller controls the discharge circuit to stop pulling down the output voltage value, and controls the current source circuit to provide a test current to the bus power terminal. The controller obtains a resistance value at the bus power terminal according to the output voltage value and a current value of the test current. In an embodiment of the disclosure, the current source circuit includes a first current source and a first switch. A first terminal of the first current source is electrically connected to the power supply terminal. The first current source generates the test current. The first switch is electrically connected between a second terminal of the first current source and the bus power terminal. In an embodiment of the disclosure, the discharge circuit includes a second current source and a second switch. A first terminal of the second current source is electrically connected to the bus power terminal. The second current source generates a discharge current. The second switch is electrically connected between a second terminal of the second current source and a reference low voltage. In an embodiment of the disclosure, before supplying power to the bus power terminal, the controller turns off the blocking switch, turns off the first switch, and turns on the second switch. In an embodiment of the disclosure, in response to the output voltage value being lowered to the first set voltage value, the controller turns off the blocking switch, turns off the second switch, and turns on the first switch. In an embodiment of the disclosure, during a period when the test current is provided to the bus power terminal, in response to the output voltage value being higher than a second set voltage value, the controller turns on the blocking switch. In an embodiment of the disclosure, the control circuit further includes a comparator. The comparator is electrically connected to the bus power terminal and the controller. The comparator receives the output voltage value and the first set voltage value. Before supplying power to the bus power terminal, the comparator compares the output voltage value and the first set voltage value to generate a comparison signal. In an embodiment of the disclosure, before supplying power to the bus power terminal, the controller receives the comparison signal. In response to the comparison signal indicating that the output voltage value is higher than the first set voltage value, the controller controls the discharge