FR3080195A1 - METHOD AND CONTROLLER FOR MANAGING THE OUTPUT POWER SUPPLY VOLTAGE OF A USB SOURCE DEVICE SUPPORTING THE USB POWER DELIVERY MODE - Google Patents

Abstract

The method of managing the supply voltage (V_BUS1) on an output power pin (VBUS) of a USB source device (2) supporting the USB power delivery mode and coupled to a USB receiver device (4) ), the USB source device (2) comprising a power converter (7) delivering the supply voltage (V BUS1) and a capacitive network (9) coupled to the power converter (7), the method comprises in response to a request to reduce the supply voltage (V BUS1) by the USB receiver device (4) to a target voltage (VF), a discharge of the capacitive network (9) so as to reduce the supply voltage (V BUS1), and a delivery to the power converter (7) of a setpoint voltage (Vc) for the supply voltage (V BUS1), the value of the target voltage (Vc) being reduced in a non-linear manner to maintain the temporal variation of the reference voltage (Vc) lower than that of the a supply voltage (V BUS1).

Description

Method and controller for managing the output supply voltage of a USB source device supporting the USB power delivery mode

Modes of implementation and embodiment of the invention relate to universal serial bus devices ("Universal Serial Bus": USB in English), in particular universal serial bus devices supporting the USB power delivery mode commonly known by a person skilled in the art under the English acronym "USB PD" ("USB Power Delivery Mode" in English), more particularly the adjustment of the voltage transmitted over a USB cable connecting a USB device called "source" and a USB device called "receiver".

Theoretically, USB devices supporting the USB PD power delivery mode make it possible to transmit, via output power pins commonly known to those skilled in the art under the acronym "VBUS", up to 100 W power on a maximum voltage of 20 V and a maximum current of 5 A.

As a result, a USB source device supporting the USB PD mode and delivering a first power to a USB receiving device, is capable of delivering in response to a power change request by the USB receiving device, a second power different from the first. power.

In a case where the second power requested is less than the first power, the USB source device is configured to develop on the output power supply pin VBUS a second voltage corresponding to the second power instead of a first voltage corresponding to the first power. The second voltage is generally lower than the first voltage.

In general, the second voltage is produced by a decrease in the first voltage via discharges from decoupling capacitors and a regulation of the voltage delivered to the output power supply pin VBUS in a standardized development period, commonly known by a person skilled in the art under the English acronym "tSrcReady" ("Source Ready time" in English "), namely generally equal to 270 ms.

However, such a decrease in the first voltage generally leads to an undershoot of the voltage delivered to the VBUS output power pin.

If this voltage delivered to the VBUS output power pin falls below a low threshold for validating the USB source device, commonly known to those skilled in the art under the acronym "vSrcValidlo", the device USB receiver may unexpectedly stop working.

In addition, if the speed of the regulation of said delivered voltage becomes greater than that of the decrease in the delivered voltage linked to discharges from the decoupling capacitors, said regulation is saturated causing the USB source device to go into standby mode for a time of rest (“blanking time” in English).

However, as the discharge of the capacitive network continues to decrease said delivered voltage while the USB source device is in standby mode and as the regulation will be reactivated only at the end of the rest time, the value of said delivered voltage may pass below the “vSrcValid lo” threshold before reactivation of the regulation or not being able to reach the target voltage before the end of the standard development period “tSrcReady”.

A conventional solution consists in developing a constant current to discharge the voltage delivered to the output power pin, but such a solution requires an adaptation of the constant current for each application of the USB source device.

Another conventional solution provides for linear regulation of the voltage delivered to the output power pin and a discharge of the decoupled capacitors by fixed resistors.

However, in order to maintain the functioning of the regulation, this solution requires the use of small resistors, which increases the consumption of the USB source device.

There is thus a need to propose a technical solution with low complexity and low consumption making it possible to ensure the proper functioning of a USB source device in response to a request to decrease the voltage delivered on an output power pin and to avoid possible under-oscillation of said delivered voltage.

According to one aspect, a method of managing the supply voltage on an output power pin of a USB source device supporting the USB power delivery mode and coupled to a USB receiver device is proposed. The USB source device comprises a power converter delivering the supply voltage and a capacitive network coupled to the power converter.

The method comprises in response to a request to decrease the supply voltage by the USB receiving device to a target voltage, discharging the capacitive network so as to reduce the supply voltage, and delivering to the power converter a set voltage for the supply voltage, the value of the set signal being decreased in a non-linear fashion to keep the time variation of the set voltage lower than that of the supply voltage.

Advantageously, such a method makes it possible to ensure that, during the development of the target voltage, the speed of regulation of the supply voltage is always less than the decrease in the supply voltage as a function of the discharge of the capacitive network. without additional implementation of the USB source device such as a programmable power source.

Consequently, the supply voltage regulation is in operation during the development of the target voltage so as to avoid under-oscillation of the supply voltage or even disconnection of the USB receiver device.

In addition, the non-linear decrease in the setpoint voltage advantageously allows the use of discharge resistors having higher values so as to reduce the consumption of the USB source device.

According to one mode of implementation, the value of the setpoint voltage is decreased in stages to the target voltage, the march between two neighboring stages being fixed, and the duration of each stage being equal to the product of a fixed duration by a variable first number.

By way of nonlimiting example, each first variable number can be determined as a function of the fixed duration, the set voltage, and said step.

As a variant, the value of the setpoint voltage can for example be selectable from among several predetermined values of the supply voltage, the value of the target voltage being one of the predetermined values, and the value of the setpoint signal can for example be decreased in stages up to the target voltage. The stages correspond respectively to said predetermined values comprised between the value of the reference voltage and the target voltage. The duration of each level is equal to the product of a fixed duration by a second variable number. And the second variable number is determined based on the current setpoint voltage, the predetermined value immediately below the current setpoint voltage, and a fixed duration.

According to another embodiment, the predetermined values of the supply voltage include 20V, 15V, 12V, 9V and 5V.

According to another aspect, a controller for managing the supply voltage is proposed on an output supply pin of a USB source device supporting the USB power delivery mode and coupled to a USB receiver device, the device USB source comprising a power converter delivering the supply voltage and a capacitive network coupled to the power converter. The controller comprises discharge means configured to, in response to a request to decrease the supply voltage by the USB receiver device to a target voltage, discharge the capacitive network so as to reduce the supply voltage, and control means configured to, in response to said request, deliver to the power converter a setpoint voltage for the supply voltage, and decrease the value of the setpoint signal in a non-linear manner to maintain the time variation of the setpoint voltage lower than that of the supply voltage.

According to one embodiment, the control means are configured to decrease in stages to the target voltage, the march between two neighboring stages being fixed and the duration of each stage being equal to the product of a fixed duration by a first number variable.

By way of non-limiting indication, the control means can also be configured to determine the variable number as a function of the fixed duration, the current setpoint voltage, and said step.

According to another embodiment, the value of the setpoint signal is selectable from among several predetermined values of the supply voltage and the value of the target voltage is one of the predetermined values.

The control means are configured to decrease the value of the setpoint signal in stages to the target voltage. The stages correspond respectively to said predetermined values comprised between the value of the setpoint voltage and the target voltage. The duration of each stage is equal to the product of a fixed duration by a second variable number. And the control means are also configured to determine the second variable number as a function of the current setpoint voltage, of the predetermined value immediately lower than the current setpoint voltage, and of a fixed duration.

According to yet another embodiment, the predetermined values of the supply voltage include 20V, 15V, 12V, 9V and 5V.

By way of nonlimiting example, the controller can be made in an integrated manner.

According to another aspect, a USB source device is proposed which supports the USB power delivery mode comprising at least one controller as defined above.

The USB source device can for example be a USB type C source device.

According to yet another aspect, an electronic device is proposed, such as cellular cellular telephone, tablet, or portable computer, comprising at least one USB source device as defined above.

Other advantages and characteristics of the invention will appear on examining the detailed description of modes of implementation and embodiments, in no way limiting, and the appended drawings in which:

- Figures 1 to 5 schematically illustrate modes of implementation and embodiment of the invention.

The reference 1 in FIG. 1 designates an electronic device, here for example a portable computer, comprising a device called “source” USB 2 supporting the USB power delivery mode, being for example compatible with the USB 3.1 standard, and comprising by example a reversible USB 3 connector which does not impose a direction of connection, commonly known to those skilled in the art as type C.

The connector 3 of type C is connected, via a USB cable 6 of type C, to a device known as “receiver” USB 4 also supporting the mode of delivery of power USB, here for example a portable telephone of the smart telephone type (“Smart Phone ”also includes a USB 5 type C connector.

The USB source device 2 and the USB receiver device 4 each have at least one channel configuration pin

CCI, at least one VBUS1 output supply voltage pin and at least one GND ground pin (Figure 2). The pins of the same kind are connected to each other by the USB cable 6.

It should be noted that the USB source and receiver devices mentioned above are illustrated by way of non-limiting example. The USB source device 2 can for example function as a USB receiving device while the USB receiving device 4 can for example function in certain cases as a USB source device.

Referring now to Figure 2 to illustrate in more detail an embodiment of the USB source device 2 further comprising an electrical power converter 7, a power line 8, a capacitive network 9, and a power controller 10.

The electrical power converter 7 is for example a converter of the alternating / continuous type (AC / DC) called "Flyback" in English.

A power input 7EA of this converter 7 is coupled to a power supply network 11 operating as a power source for the USB source device 2.

A control input 7EC of this converter 7 is coupled to the power controller 10.

An output 7S of this converter 7 is coupled to said at least one output supply pin VBUS1 via the supply line 8.

The electrical power converter 7 is configured to deliver to the supply line 8 a supply voltage VBUSl under the control of the supply controller 10.

The capacitive network 9 comprises a first capacitor C1 coupled between the output 7S of the electrical power converter 7 and the ground GND and a second capacitor C2 coupled between the output power supply pin VBUS1 and the ground GND.

The power supply controller 10 is made in an integrated manner, for example in the form of a microcontroller and comprises discharge means 12, feedback means 13, and control means 14.

The discharge means 12 comprise a first discharge stage 12a coupled between the output SI of the electric power converter 7 and the ground GND, and configured to discharge the first capacitor C1 under the control of the control means 14, and a second discharge stage 12b coupled between said at least one output supply pin VBUS1 and ground GND, and configured to discharge the second capacitor C2 under control of the control means 14.

For example, the first discharge stage 12a comprises a first discharge resistance RDI and a first switch IPT1 under control of the control means 14, and the second discharge stage 12b comprises a second discharge resistance RD2 and a second switch IPT2 under control of the control means 14.

Each of the first and second switches IPT1, IPT2 can for example be made in the form of a transistor and is configured to be in its state passing under the control of the control means 14 during said discharge from the capacitive network 9.

The feedback means 13 comprise a detection input 13ED coupled to the output 7S of the electric power converter 7 and intended to receive the supply voltage V BUS1 delivered by the electric power converter 7, a control input 13EC coupled to the means control 14 and intended to receive a reference voltage Vc, and an output 13S coupled to the control input 7EC of the electric power converter 7.

The feedback means 13 are configured to supply the electrical power converter 7 with a feedback voltage as a function of a comparison between the supply voltage V BUS1 and the reference voltage Vc so as to regulate the supply voltage VBUSl to the setpoint voltage Vc.

By way of non-limiting indication, the feedback means 13 may include a voltage divider bridge with variable resistances, a controllable current source, an opto-coupling device or a regulation loop known to those skilled in the art.

The control means 14 are coupled to at least one CCI channel configuration pin and comprise a first control module MCI coupled to the first and second discharge stages 12a and 12b and configured to control their discharges, and a second control module MC2 coupled to the control input 7EC of the electrical power converter 7 and configured to deliver to the feedback means 13 the reference signal SC so as to control the regulation of the supply voltage V BUS1 via the feedback means 13.

The second control module MC2 comprises a digital-analog converter 15 (“digital-analog converter”: DAC in English) configured to deliver the reference voltage Vc under the control of a control signal SC, and a control stage 16 configured to deliver to the digital-analog converter 15 the control signal SC so as to control the variation of the reference signal SC.

When the USB receiver device 4 (FIG. 1) requests a power supply lower than the supply voltage V BUS1 delivered by the USB source device 2, the USB receiver device 4 is configured to deliver to the control means 14 of the source device USB 2 via the CCI channel configuration pin, a request to decrease the supply voltage V BUSl to a target voltage VF.

The first MCI control module is configured to discharge the capacitive network 9 so as to reduce the supply voltage V BUS1 and the second MC2 control module is configured to control the regulation of the reference voltage which the voltage must follow. VBUSl power supply.

By way of nonlimiting example, the supply voltage VBUSl before the decrease request is 20V and the target voltage is 5V.

Depending on the resolution of the digital analog converter 15, a minimum voltage variation step Vstep (“voltage step”) is obtained at its output, corresponding to the minimum variation attainable by the digital analog converter 15, here for example Vstep = 12.5mV. The time necessary to carry out a minimum step of variation in voltage Vstep, in other words a minimum step of variation in time ("time step" in English), is determined by a clock signal from the power supply controller 10, here for example we have Tstep = l / 32768s.

A conventional solution of the prior art consists in linearly decreasing the value of the reference voltage Vc which the supply voltage V BUSl must follow.

However, in order to maintain the operation of the feedback means 13, the time variation of the setpoint voltage Vc, in other words the derivative with respect to time of the setpoint voltage Vc, must be less than the rate of change of the voltage V BUSl.

As the supply voltage V BUSl continues to decrease, it is the target voltage VF which is critical for ensuring the proper functioning of the feedback means 13. We therefore have dVc VF ~ dF ^< RC where R is the equivalent resistance of the resistors discharge RDI and RD2 of the first discharge stage 12a and of the second discharge stage 12b and C is the equivalent capacity of the capacitors Cl and C2 of the capacitive network 9.

For the so-called “Flyback” converter 7 with VF = 5V, C = 1000pF and - = 15V / 200ms, the equivalent resistance R must be less than 66 ohms.

It should be noted that the converter 7 can also be a switching power supply or a DC / DC type converter called "Buck" known to those skilled in the art. In a case where VF = 5V, C = 200pF and - = 15V / 200ms, the equivalent resistance R must be less than 330 ohms.

With these values of the equivalent resistance R, the discharge current at the start of the discharge of the capacitive network 9 as well as the consumption of the USB source device 2 are high.

Thus, according to one aspect of the invention, the power controller 10 is configured to, on receiving the request to decrease the power supply voltage VBUSl, discharge the capacitive network 9 so as to reduce the power supply voltage V BUSl , and deliver to the power converter 7 the reference voltage Vc which the supply voltage V BUS1 must follow.

The value of the setpoint voltage Vc is reduced in a non-linear fashion.

More precisely, the value of the setpoint voltage Vc is decreased in stages to the target voltage VF.

The step between two landings is fixed. The duration of each level is variable and equal to the product of a fixed duration by a first variable number.

The step between two bearings is here the minimum step of variation in voltage Vstep. The fixed duration is here the minimum step of variation in time Tstep.

The first variable number Nstepl is determined as a function of the fixed duration Tstep, of the current setpoint voltage Vc, and of said step Vstep.

We have for example

Tstep * R * C

Nstepl =

Vstep * Vc where the symbol [1 represents the notation of the whole part by excess (“ceiling” in English).

It should be noted that the setpoint voltage decreases as a function of time. Consequently, the first variable number Nstepl increases as a function of time.

FIG. 3 illustrates an example of variation of the first variable number Nstepl as a function of the reference voltage Vc.

When the value of the setpoint voltage Vc is greater than 17V, the first number Nstepl is equal to 3. The value of the first number Nstepl reaches 10 when the setpoint voltage Vc is equal to the target voltage VF, i.e. - say 5V.

As illustrated in FIG. 3, the speed of variation of the reference voltage Vc at the start of the discharge of the capacitive network 9 is higher. More precisely, the setpoint voltage Vc is reduced by a minimum step of variation in voltage Vstep after three minimum steps of variation in time Tstep.

On the other hand, the speed of variation of the reference voltage Vc at the end of the discharge of the capacitive network 9 is lower, it is necessary to wait ten minimum steps of variation in time Tstep to have a decrease of a minimum step of variation in voltage Vstep on the setpoint voltage Vc. Otherwise, it is advantageous to have a lower discharge current at the end of the discharge.

Therefore, a greater equivalent resistance R, for example of 120 ohms, can advantageously be used in a configuration for example with a so-called “flyback” converter, so as to reduce the consumption of the USB source device.

As a variant, the second control module MC2 of the USB source device 2 may comprise (FIG. 4) instead of the digital analog converter 15, a voltage divider 17, known to those skilled in the art, so as to deliver the reference voltage Vc whose value is selectable from a series of predetermined values Vp of the supply voltage V BUS1.

These predetermined values Vp of the supply voltage V_BUS1 comprise for example 20V, 15V, 12V, 9V, 5V, in accordance with the USB 3.1 standard and the target voltage VF is for example also selected from these predetermined values.

In this case, the control means 10 are configured to decrease the value of the setpoint voltage Vc in stages to the target voltage VF.

The stages correspond respectively to said predetermined values comprised between the set value Vc and the target voltage VF.

For example, for a request to decrease the supply voltage V BUSl from 20V to 9V, the value of the setpoint voltage Vc must be decreased from 20V to 15V, and then from 15V to 12V, and finally from 12V to 9V. The corresponding steps are 20V, 15V, 12V and 9V.

The duration of each level is variable and equal to the product of a fixed duration by a second variable number.

In other words, the current setpoint voltage Vc is switched to the predetermined value Vci immediately lower than the current setpoint voltage Vc at the end of said duration.

The fixed duration can for example also be the minimum step of variation in time Tstep.

The second variable number Nstep2 is determined as a function of the current setpoint voltage Vc, of the predetermined value Vci immediately lower than the current setpoint voltage Vc, and of the fixed duration Tstep.

The second variable number Nstep2 is calculated for example as below:

R "C * ln (Is)

Nstep2 = --- Tstep where R is the equivalent resistance of the discharge resistors RDI and RD2 of the first discharge stage 12a and the second discharge stage 12b and C is the equivalent capacity of the capacitors Cl and C2 of the capacitive network 9.

With for example R = 120 ohms, C = 100 pF, one can find on figure 5 the values of the second variable number Nstep2 calculated.

If the current setpoint voltage Vc is 20V and the target voltage is 5V, it is first necessary to wait for 1130 minimum steps of variation in time Tstep before switching to the predetermined value Vci immediately below the current setpoint voltage Vc , namely at 15V.

And then the current setpoint voltage Vc becomes 15V and the second variable number Nstep 2 is determined as a function of this current setpoint value Vc, of the predetermined value Vci immediately lower than the current setpoint voltage Vc, that is to say 12V , and the fixed duration Tstep. It is then necessary to wait for 887 Tstep before switching the setpoint voltage Vc from 15V to 12V.

Similarly, we wait 1130 Tstep before switching the setpoint voltage Vc from 12V to 9V and finally 2309 Tstep before switching the setpoint voltage Vc from 9V to 5V.

Thus, a non-linear regulation of the supply voltage is obtained on an output supply pin of a USB source device, making it possible not only to avoid possible under-oscillations of the supply voltage so as to ensure the correct operation of the USB source device and also to use a higher resistance, for example 120 ohms instead of 66 ohms in the case of a so-called “flyback” converter, so as to save consumption without making any additional modifications to the structure of the USB source device.

Claims (14)

1. Method for managing the supply voltage (VBUSl) on an output power supply pin (VBUS) of a USB source device (2) supporting the USB power delivery mode and coupled to a USB receiver device ( 4), the USB source device (2) comprising a power converter (7) delivering the supply voltage (VBUSl) and a capacitive network (9) coupled to the power converter (7), the method comprising in response to a request to decrease the supply voltage (V BUSl) by the USB receiver device (4) to a target voltage (VF), discharge the capacitive network (9) so as to decrease the supply voltage (V BUSl), and a supply to the power converter (7) of a setpoint voltage (Vc) for the supply voltage (V BUSl), the value of the setpoint voltage (Vc) being decreased in a non-linear fashion to keep the time variation of the setpoint voltage (Vc) lower to that of the supply voltage (V BUSl). 2. Method according to claim 1, in which the value of the setpoint voltage (Vc) is decreased in stages to the target voltage (VF), the march (Vstep) between two neighboring stages being fixed and the duration of each level being equal to the product of a fixed duration (Tstep) by a first variable number (Nstepl). 3. Method according to claim 2, in which each first variable number (Nstepl) is determined as a function of the fixed duration (Tstep), of the current setpoint voltage (Vc), and of said step (Vstep). 4. Method according to claim 1, in which the value of the setpoint voltage (Vc) is selectable from among several predetermined values (Vp) of the supply voltage (V BUSl), the value of the target voltage (VF) being one of said predetermined values (Vp), and the value of the setpoint voltage (Vc) is decreased in stages to the target voltage (VF), the stages respectively corresponding to said predetermined values comprised between the value of the setpoint voltage and the target voltage, the duration of each plateau being equal to the product of a fixed duration (Tstep) by a second variable number (Nstep2), and the second variable number (Nstep2) being determined as a function of the setpoint voltage (Vc) current, of the predetermined value (Vci) immediately below the current setpoint voltage (Vc), and of a fixed duration (Tstep). 5. The method of claim 4, wherein the predetermined values (Vp) of the supply voltage (VBUSl) include 20V, 15V, 12V, 9V and 5V. 6. Supply voltage management controller (V BUSl) on an output supply pin (VBUS) of a USB source device (2) supporting the USB power delivery mode and coupled to a USB receiver device (4), the USB source device (2) comprising a power converter (7) delivering the supply voltage (VBUSl) and a capacitive network (9) coupled to the power converter (7), the controller (10) comprising discharge means (12) configured to, in response to a request to decrease the supply voltage (V BUSl) by the USB receiver device (4) to a target voltage (VF), discharge the capacitive network ( 9) so as to reduce the supply voltage (VBUSl), and control means (14) configured to, in response to said request, deliver to the power converter (7) a reference voltage (Vc) for the supply voltage (V BUSl), and decrease the value of the tensio n setpoint (Vc) nonlinearly to keep the time variation of the setpoint voltage (Vc) lower than that of the supply voltage (VBUSl). 7. Controller according to claim 6, wherein the control means (14) are configured to decrease in stages to the target voltage (VF), the march (Vstep) between two neighboring stages being fixed and the duration of each stage being equal to the product of a fixed duration (Tstep) by a first variable number (Nstepl). 8. Controller according to claim 7, in which the control means (14) are further configured to determine the first variable number (Nstepl) as a function of the fixed duration (Tstep), of the current reference voltage (Vc), and said step (Vstep). 9. Controller according to claim 6, in which the value of the setpoint voltage (Vc) is selectable from among several predetermined values (Vp) of the supply voltage (V BUSl), the value of the target voltage (VF) being one of the predetermined values (Vp) of the supply voltage (V BUSl), and the control means (14) are configured to decrease the value of the setpoint voltage (Vc) in stages to the target voltage (VF ), the stages corresponding respectively to said predetermined values (Vp) comprised between the value of the setpoint voltage and the target voltage, the duration of each stage being equal to the product of a fixed duration (Tstep) by a second variable number (Nstep2 ), and the control means (14) being further configured to determine the second variable number (Nstep2) as a function of the current setpoint voltage (Vc), of the predetermined value (Vci) immediately below the co voltage nsign (Vc) current, and of a fixed duration (Tstep). 10. Controller according to claim 9, wherein the predetermined values (Vp) of the supply voltage include 20V, 15V, 12V, 9V and 5V. 11. Controller according to any one of claims 6 to 10, produced in an integrated manner. 12. USB source device supporting the USB power delivery mode comprising at least one controller (10) according to any one of claims 6 to 11. 13. Device according to claim 12, is a USB type C source device. 14. An electronic device, such as a cellular portable telephone, tablet, or portable computer, comprising at least one device (2) according to claim 12 or 13.