US-12625831-B2 - Dynamic load current adjustment to avoid PFM frequency in audio range

Abstract

In an embodiment of the techniques presented herein, a universal serial bus power delivery (USB-PD) power adaptor includes a USB port, and a USB controller configured to deliver power to the USB port, wherein the USB controller includes a voltage regulator configured to generate a power supply voltage based on a pulse frequency modulation (PFM) signal, and a variable current bleed unit configured to generate a variable current bleed load on the voltage regulator based on a frequency of the PFM signal to maintain the frequency of the PFM signal above an audible frequency range.

Inventors

• Ravi Theja KONDURU
• Hemant Vispute
• Yeshwanth KALIGONAHALLI THIPPESWAMY

Assignees

• CYPRESS SEMICONDUCTOR CORPORATION

Dates

Publication Date

20260512

Application Date

20231222

Claims (20)

1. 1 . A universal serial bus power delivery (USB-PD) power adaptor comprising: a USB port; and a USB controller configured to deliver power to the USB port, wherein the USB controller comprises: a voltage regulator configured to generate a power supply voltage dependent on a load current of the USB controller based on a pulse frequency modulation (PFM) signal having a switching frequency; and a variable current bleed unit comprising a control unit configured to generate a variable current bleed load on the voltage regulator based on the switching frequency and an audible frequency threshold to add a bleed current not dependent on the load current of the USB controller to the load current to maintain a frequency of the PFM signal above an audible frequency range.
2. 2 . The USB-PD power adaptor of claim 1 , wherein: the variable current bleed unit comprises a digital variable current bleed unit.
3. 3 . The USB-PD power adaptor of claim 2 , wherein the control unit in the digital variable current bleed unit comprises: a frequency calculator configured to determine the frequency of the PFM signal; a current digital to analog converter configured to generate the variable current bleed load based on a current code; and a controller configured to generate the current code based on the frequency of the PFM signal.
4. 4 . The USB-PD power adaptor of claim 1 , wherein: the variable current bleed unit comprises an analog variable current bleed unit.
5. 5 . The USB-PD power adaptor of claim 4 , wherein the control unit in the analog variable current bleed unit comprises: a frequency-to-voltage converter configured to generate a control voltage as a function of the frequency of the PFM signal; and a voltage-to-current converter configured to generate the variable current bleed load based on the control voltage.
6. 6 . The USB-PD power adaptor of claim 5 , wherein the frequency-to-voltage converter comprises: a pulse generator configured to generate a pulse based on a time interval between PFM pulses in the PFM signal; a rising edge reset unit configured to generate a reset signal for the pulse generator to terminate the pulse based on a rising edge of the PFM signal; and a filter configured to generate the control voltage based on the pulse.
7. 7 . The USB-PD power adaptor of claim 6 , wherein the pulse generator comprises: a current source; a capacitor connected to the current source; a switch controlled by the reset signal to discharge the capacitor; and a comparator configured to generate the pulse based on a reference voltage and a voltage on the capacitor.
8. 8 . The USB-PD power adaptor of claim 5 , wherein the voltage-to-current converter comprises a transconductance amplifier.
9. 9 . A method for operating a universal serial bus power delivery (USB-PD) power adaptor comprising: delivering power to a USB port using a USB controller; generating a power supply voltage dependent on a load current of the USB controller in a voltage regulator based on a pulse frequency modulation (PFM) signal having a switching frequency; and generating a variable current bleed load on the voltage regulator based on the switching frequency and an audible frequency threshold to add a bleed current not dependent on the load current of the USB controller to the load current to maintain a frequency of the PFM signal above an audible frequency range.
10. 10 . The method of claim 9 , wherein generating the variable current bleed load comprises: configuring a digital variable current bleed unit based on the frequency of the PFM signal.
11. 11 . The method of claim 10 , wherein configuring the digital variable current bleed unit comprises: determining the frequency of the PFM signal in a frequency calculator; generating the variable current bleed load in a current digital to analog converter based on a current code; and generating the current code based on the frequency of the PFM signal.
12. 12 . The method of claim 9 , wherein generating the variable current bleed load comprises: configuring an analog variable current bleed unit based on the frequency of the PFM signal.
13. 13 . The method of claim 12 , wherein configuring the analog variable current bleed unit comprises: generating a control voltage in a frequency-to-voltage converter as a function of the frequency of the PFM signal; and generating the variable current bleed load in a voltage-to-current converter based on the control voltage.
14. 14 . The method of claim 13 , wherein generating the control voltage in the frequency-to-voltage converter comprises: generating a pulse in a pulse generator based on a time interval between PFM pulses in the PFM signal; generating a reset signal for the pulse generator based on a rising edge of the PFM signal to terminate the pulse; and generating the control voltage based on the pulse.
15. 15 . The method of claim 14 , wherein generating the pulse in the pulse generator comprises: charging a capacitor with a current source; generating the pulse based on a reference voltage and a voltage on the capacitor; and controlling a switch based on the reset signal to discharge the capacitor to terminate the pulse.
16. 16 . The method of claim 13 , wherein generating the variable current bleed load in the voltage-to-current converter comprises: generating the variable current bleed load in a transconductance amplifier.
17. 17 . A universal serial bus power delivery (USB-PD) power adaptor comprising: a USB port; a power switch connected between a voltage input terminal and the USB port; and a USB controller configured to control the power switch to deliver power to the USB port from the voltage input terminal, wherein the USB controller comprises: a voltage regulator configured to generate a power supply voltage dependent on a load current of the USB controller based on a pulse frequency modulation (PFM) signal having a switching frequency; and a variable current bleed unit comprising a control unit configured to generate a variable current bleed load on the voltage regulator based on the switching frequency and an audible frequency threshold to add a bleed current not dependent on the load current of the USB controller to the load current to maintain the frequency of a PFM signal above an audible frequency range.
18. 18 . The USB-PD power adaptor of claim 17 , wherein the variable current bleed unit comprises a digital variable current bleed unit, and the control unit comprises: a frequency calculator configured to determine the frequency of the PFM signal; a current digital to analog converter configured to generate the variable current bleed load based on a current code; and a controller configured to generate the current code based on the frequency of the PFM signal.
19. 19 . The USB-PD power adaptor of claim 17 , wherein the variable current bleed unit comprises an analog variable current bleed unit, and the control unit comprises: a frequency-to-voltage converter configured to generate a control voltage as a function of the frequency of the PFM signal; and a voltage-to-current converter configured to generate the variable current bleed load based on the control voltage.
20. 20 . The USB-PD power adaptor of claim 19 , wherein: the frequency-to-voltage converter comprises: a pulse generator configured to generate a pulse based on a time interval between PFM pulses in the PFM signal; a rising edge reset unit configured to generate a reset signal for the pulse generator to terminate the pulse based on a rising edge of the PFM signal; and a filter configured to generate the control voltage based on the pulse; and the voltage-to-current converter comprises a transconductance amplifier.

Description

BACKGROUND Various electronic devices (e.g., such as smartphones, tablets, notebook computers, laptop computers, hubs, chargers, adapters, etc.) are configured to transfer power through Universal Serial Bus (USB) connectors according to USB power delivery protocols defined in various revisions of the USB Power Delivery (USB-PD) specification. Alternating current to direct current (AC-DC) converters convert power from an alternating current (AC) source to a direct current (DC) source at a specified voltage level. A buck converter is a DC-DC switching converter that steps down an input voltage while increasing load current. One technique for controlling a buck converter is a pulse frequency modulation (PFM) techniques that controls the switching using a signal that changes the pulse frequency as a function of load current to maintain the output voltage. As the load current increases, the PFM frequency increases, and as the load current decreases the PFM frequency decreases. SUMMARY This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key factors or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. In an embodiment of the techniques presented herein, a universal serial bus power delivery (USB-PD) power adaptor comprises a USB port, and a USB controller configured to deliver power to the USB port, wherein the USB controller comprises a voltage regulator configured to generate a power supply voltage based on a pulse frequency modulation (PFM) signal, and a variable current bleed unit configured to generate a variable current bleed load on the voltage regulator based on a frequency of the PFM signal to maintain the frequency of the PFM signal above an audible frequency range. In an embodiment of the techniques presented herein, a method for operating a universal serial bus power delivery (USB-PD) power adaptor comprises delivering power to a USB port using a USB controller, generating a power supply voltage for the USB controller in a voltage regulator based on a pulse frequency modulation (PFM) signal, and generating a variable current bleed load on the voltage regulator based on a frequency of the PFM signal to maintain the frequency of the PFM signal above an audible frequency range. In an embodiment of the techniques presented herein, a system for operating a universal serial bus power delivery (USB-PD) power adaptor comprises means for delivering power to a USB port using a USB controller, means for generating a power supply voltage for the USB controller in a voltage regulator based on a pulse frequency modulation (PFM) signal, and means for generating a variable current bleed load on the voltage regulator based on a frequency of the PFM signal to maintain the frequency of the PFM signal above an audible frequency range. In an embodiment of the techniques presented herein, a universal serial bus power delivery (USB-PD) power adaptor comprises a USB port, a power switch connected between a voltage input terminal and the USB port, and a USB controller configured to control the power switch to deliver power to the USB port from the voltage input terminal, wherein the USB controller comprises a voltage regulator configured to generate a power supply voltage based on a pulse frequency modulation (PFM) signal, and a variable current bleed unit configured to generate a variable current bleed load on the voltage regulator based on a frequency of the PFM signal to maintain the frequency of the PFM signal above an audible frequency range. To the accomplishment of the foregoing and related ends, the following description and annexed drawings set forth certain illustrative aspects and implementations. These are indicative of but a few of the various ways in which one or more aspects may be employed. Other aspects, advantages, and novel features of the disclosure will become apparent from the following detailed description when considered in conjunction with the annexed drawings. DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a universal serial bus (USB) power delivery (USB-PD) adaptor, in accordance with some embodiments. FIG. 2 is a diagram illustrating the operation of a high voltage regulator, in accordance with some embodiments. FIG. 3 is a block diagram of a digital variable current bleed unit, in accordance with some embodiments. FIG. 4A is a block diagram of an analog variable current bleed unit, in accordance with some embodiments. FIG. 4B is a circuit diagram of the analog variable current bleed unit, in accordance with some embodiments. FIG. 5 is a diagram illustrating the operation of the analog variable current bleed unit as a function of load current, i_L, in accordance with some embodiments. FIG. 6 is a diagram illustrating the operation of the digital variable current bleed u