Method for reducing standby power and related controller and switch mode power supply

Abstract

The present application relates to methods for reducing standby power and related controllers and switch-mode power supplies. In a power supply having a control circuit for regulating a power supply output and for connecting the output to a load device, a method for reducing standby power includes determining whether a load device is connected to the power supply. If no load device is connected, the load switch is turned off and the power supply enters a standby mode, the standby mode including a first time period of an alternating power saving mode and a second time period of a regulation mode. In the power saving mode, the control circuit stops regulating the output of the power supply and turns off one or more functional blocks to allow the output to decrease until the output reaches a preset low output limit. In the regulation mode, the control circuit turns on the functional blocks and regulates the power supply to allow the output to increase until the output reaches a preset high output limit.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to commonly assigned U.S. Provisional Patent Application No. 62 / 816,062, filed on March 9, 2019, entitled “CIRCUIT AND METHOD FOR REDUCING STANDBY POWER,” which is incorporated herein by reference in its entirety for all purposes. Technical Field

[0003] The present invention relates to switched mode power supplies and more particularly to methods and apparatus for reducing power consumption of switched mode power supplies. Background Art

[0004] Regulated power supplies are essential in modern electronics. For example, power supplies in personal computers often need to receive power input from various sockets. Desktop and laptop computers often have regulated power supplies on the motherboard to power the CPU, memory, and peripheral circuits. Mobile devices require chargers that provide regulated charging power. Switch-mode controllers quickly turn power transistors on and off with variable duty cycles or variable frequencies and provide an average output that is the desired output voltage or output current.

[0005] Universal Serial Bus (USB) is an industry standard for establishing the specifications of cables, connectors and protocols for connection, communication and power supply between computers, peripheral devices and other computers. The USB Developer Forum (USB IF) released the USB Power Delivery (PD) function and Type-C connector for general 3C products in 2014. USB PD and Type-C are for connecting all devices in one connector. The power delivery (PD) controller is a secondary side controller for handling USB Type-C connectors. USB-C connectors and cables can be connected to both the host and the device, thereby replacing various electrical connectors including USB-B and USB-A, HDMI, DisplayPort and 3.5mm audio cables and connectors. The USB PD controller includes many circuit blocks for handling complex functions. For example, in order to change the voltage and communication to meet the PD function, the system requires additional components such as PD decoders. Therefore, the system consumes more power.

[0006] Therefore, a more power efficient secondary side controller for SMPS supporting USB PD functionality is highly desirable. Summary of the invention

[0007] The inventors have recognized that a USB PD controller needs to support complex functions and consume more power than previous controllers. The USB-C connector is connected to the output of the converter via a load switch. When the USB-C controller detects that no load device is connected to the converter, the controller turns off the load switch to disconnect the power provided to the USB-C connector and the load device. In conventional USB PD products, even when no load device is connected, the power supply maintains a constant output voltage Vout, and the USB PD integrated circuit (PDIC) remains active and consumes power.

[0008] The present invention teaches a USB PD controller that continuously monitors the state of the USB interface to determine whether a load device is connected. If no load device is connected, in addition to turning off the load switch to disconnect the power output from the USB connector. The USB PD controller also forces the feedback voltage (VFB) to reach a preset low value to cause the primary side controller to stop regulating the output voltage. Under this condition, the power output voltage Vout is maintained by the capacitance of the system, which provides operating power to the active circuit blocks. In order to further reduce power consumption in the standby state, the USB PD controller turns off the power supply to all functional blocks in the USB PD controller, except for the circuit for continuing to monitor the state of the load device and the circuit for monitoring the output voltage of the converter. As the capacitance of the system discharges, the power output voltage Vout begins to drop. Once the power output voltage Vout drops to the preset low voltage limit V L , the USB PD controller raises the VFB signal to start regulation, which causes the converter output voltage Vout to increase. When Vout reaches the preset high voltage limit V H When no USB device is connected, the USB PD controller causes the primary-side controller to stop regulating. This cycle repeats until the USB PD controller senses that a USB device has been connected, the USB PD controller wakes up the primary-side controller to resume normal regulation functions, restores power to all its functional blocks, and turns on the load switch to connect the power output to the USB connector.

[0009] For example, the present invention teaches a method for reducing standby power in a power supply having a control circuit for regulating the output of the power supply and a load switch for connecting the output of the power supply to a load device. The method includes determining whether a load device is connected to the power supply. In response to determining that no load device is connected to the power supply, the load switch is turned off to disconnect from the load device, and the power supply enters a standby mode. The standby mode includes a first time period of an alternating power saving mode and a second time period of a regulation mode. In the power saving mode, the control circuit stops regulating the output of the power supply and turns off one or more functional blocks to allow the output to decrease until the output reaches a preset low output limit. In the regulation mode, the control circuit turns on the functional blocks and regulates the power supply to allow the output to increase until the output reaches a preset high output limit, at which time the power supply enters the power saving mode. In response to determining that the load device is connected to the power supply, the power supply enters a normal mode, wherein the control circuit regulates the output of the power supply, the functional blocks in the control circuit are powered on, and the load switch is turned on to connect the load device to the power supply.

[0010] The present invention also teaches a universal serial bus power delivery (USB PD) controller, which includes: a first terminal for coupling to a secondary winding of a switch mode power supply (SMPS) to receive operating power; a second terminal for providing a control signal to a load switch coupled between the secondary winding and a USB connector; and a third terminal for providing a feedback signal to a primary side controller of the SMPS. The USB PD controller also includes a decoder for monitoring CC1 and CC2 signals from the USB connector to determine whether a USB device is connected. In addition, the USB PD controller also has control logic, which is configured to monitor CC1 and CC2 signals from the USB connector to determine whether a USB load device is connected. After determining that no USB load device is connected to the USB connector, the controller turns off the load switch to disconnect the secondary winding from the USB connector and enter a standby mode. The standby mode includes a first time period of an alternating power saving mode and a second time period of a regulating mode. In the power saving mode, the control logic stops regulating the output of the power supply and turns off one or more functional blocks to allow the output to drop until the output reaches a preset low output limit. In the regulation mode, the control logic turns on the functional blocks and regulates the power supply to allow the output to increase until the output reaches the preset high output limit. After determining that a USB load device is connected to the USB connector, the power supply enters the normal mode, in which the control logic regulates the output of the power supply, the functional blocks are powered on, and the load switch is turned on to connect the load device to the power supply.

[0011] The present invention also teaches a switch mode power supply (SMPS) having a universal serial bus power delivery (USB PD) controller. The SMPS includes: a transformer having a primary winding for coupling to an external input voltage and a secondary winding for providing an output voltage of the SMPS; a load switch coupling the secondary winding to a USB connector; and a power switch for coupling to the primary winding of the SMPS. The SMPS also has a primary side controller coupled to the power switch to control the power switch, the primary side controller including a feedback terminal for receiving a feedback signal representing the output voltage of the SMPS via an optocoupler. The primary side controller is configured to regulate the output voltage of the SMPS at a target voltage by generating a control signal for turning the power switch on and off based on at least the feedback signal. The primary side controller can operate in a pulse width modulation (PWM) mode during normal operation, and the primary side controller operates in a burst mode during low load or no load conditions. The SMPS also has a USB PD controller coupled to the secondary winding for providing support for USB power delivery operations, wherein the USB PD controller is configured to monitor CC1 and CC2 signals from the USB connector. In active mode, the USB PD controller causes the SMPS to enter standby mode after determining that no USB load device is connected to the USB connector.

[0012] In the above SMPS, in the standby mode, after determining that the USB load device is connected to the USB connector, the USB PD controller causes the SMPS to enter the active mode. In order to cause the SMPS to enter the standby mode, the USB PD controller is configured to turn off the load switch to disconnect the output voltage of the SMPS from the USB connector, turn off one or more functional blocks in the USB PD controller, and monitor the output voltage of the SMPS. After determining that the output voltage is higher than the high standby voltage limit (which may be a preset high voltage limit), the USB PD controller sets the feedback signal to the primary side controller via the optocoupler at a first value, so that the primary side controller stops regulating the output voltage and allows the output voltage to drop. After determining that the output voltage is lower than the low standby voltage limit (which may be a preset low voltage limit), the USB PD controller sets the feedback signal to the primary side controller via the optocoupler at a second value, so that the primary side controller starts regulating the output voltage and allows the output voltage to increase. To cause the SMPS to enter the active mode, the USB PD controller is configured to turn on the one or more functional blocks in the USB PD controller, set the feedback signal to the primary side controller via the optocoupler at the second value to cause the primary side controller to start regulating the output voltage in the active mode, and turn on the load switch to connect the output voltage of the SMPS to the USB connector.

[0013] definition

[0014] The terms used in this disclosure generally have their ordinary meaning in the technical field within the context of the present invention. Specific terms are discussed below to provide additional guidance to practitioners about the description of the present invention. It should be understood that the same thing can be stated in more than one way. Therefore, alternative wording and synonyms can be used.

[0015] As used herein, a power switch refers to a semiconductor switch, such as a transistor, that is designed to handle high power levels.

[0016] A power MOSFET is a specific type of metal oxide semiconductor field effect transistor (MOSFET) designed to handle significant power levels. An example of a power MOSFET used for switching operations is called double diffused MOS or simply DMOS.

[0017] A power converter is an electrical or electromechanical device used to convert electrical energy, for example between AC and DC or to change the voltage, current or frequency or some combination of these conversions. A power converter often includes voltage regulation.

[0018] A voltage stabilizer or voltage regulator is a device used to automatically maintain a constant voltage level.

[0019] A switching regulator or switched mode power supply (SMPS) is a power converter that uses active devices that switch on and off to maintain an average value of the output. In contrast, a linear regulator is manufactured to work like a variable resistor, continuously adjusting a voltage divider network to maintain a constant output voltage, and continuously dissipating power.

[0020] A voltage reference is an electronic device that ideally produces a fixed (constant) voltage regardless of the load on the device, power supply variations, temperature changes, and the passage of time.

[0021] The reference voltage is a voltage value used as a target for comparison operation.

[0022] When the term "same" is used to describe two quantities, it means that the values ​​of the two quantities are determined to be the same within the limits of measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a simplified block diagram illustrating a system having a power supply for providing power to a USB device embodying certain aspects of the present invention;

[0024] Figure 2 is a simplified flow chart illustrating a method for reducing standby power using a USB Power Delivery (USB PD) controller embodying certain aspects of the present invention;

[0025] Figure 3is a graph showing the voltage of Vout and Vbus with respect to the time axis under standby conditions in a conventional system;

[0026] Figure 4 is a graph showing waveforms of Vout and Vbus with respect to time under standby conditions embodying certain aspects of the present invention;

[0027] Figure 5 is a simplified schematic diagram illustrating a system having a power supply providing power to a USB PD device embodying certain aspects of the present invention;

[0028] Figure 6 is a simplified block diagram of a primary side controller of a switch mode power supply embodying certain aspects of the present invention;

[0029] Figure 7 is a simplified block diagram of a secondary side controller of a switch mode power supply embodying certain aspects of the present invention; and

[0030] Figure 8 is a simplified flow chart illustrating a method for reducing standby power in a power supply embodying certain aspects of the present invention. DETAILED DESCRIPTION

[0031] Figure 1 is a simplified block diagram showing a system having a power supply providing power to a USB PD device embodying certain aspects of the present invention. Figure 1 As shown in FIG, system 100 includes a power supply 110, which may be a switch mode power supply (SMPS), providing power to a USB load device 120. Load device 120 may be any electronic device having a compatible USB connector, such as a personal computer, laptop computer, mobile device, or charger.

[0032] As combined with the following Figure 5 As described, in a flyback converter such as a switch mode power supply (SMPS) 110, a primary side controller (e.g., a PWM controller) regulates the current in a transformer via a power switch in response to a feedback voltage (VFB) representing the converter output voltage to provide a constant output voltage (or current). The feedback voltage is sampled on the output side of the transformer and coupled back to the primary side controller via an interface device such as an optocoupler.

[0033] exist Figure 1In the present invention, a USB PD controller integrated circuit (PDIC) 130 is coupled to the secondary side of the transformer to perform various control functions related to USB PD. The PDIC 130 is coupled to a load switch 140, which connects the power supply 110 to the USB load device 120. The output voltage of the power supply 110 is Vout, and the voltage provided to the USB load device 120 is Vbus. The USB PD controller 130 continuously monitors the status of the USB interface to manage power consumption in the system, as described below with reference to Figure 2 The flowchart and Figure 3 and 4 Described in the diagram.

[0034] Figure 2 2 is a simplified flow chart illustrating a method 200 for reducing standby power using a USB power delivery (USB PD) controller embodying certain aspects of the present invention. As shown in the flow chart, at 210, the USB PD controller monitors a status signal from a CC pin of a USB interface, such as a USB connector. At 220, the USB PD controller determines whether the power supply should be in standby mode. If so, the method proceeds to 230. Otherwise, the method transitions to normal operating mode 270. As an example, if no USB device is connected to the power supply, the power supply may be placed in standby mode. On the other hand, if a USB device is connected, the power supply is in normal operating mode.

[0035] At 230, when the USB PD controller determines that the power supply should be in standby mode, it turns off the load switch 140. At 240, the USB PD controller continues to check the standby condition. If the standby condition should be maintained, at 250, the USB PD controller sends a signal to the primary side controller to stop regulation and stop providing power to the output. The USB PD controller only maintains the circuit blocks required to monitor the output status and turns off the unused circuit blocks in the USB PD controller to reduce power consumption. At this point, the power in the system is provided by the charge remaining on the capacitors in the system. At 260, the USB PD controller continues to check the standby condition.

[0036] Figure 3 is a graph showing the voltage of Vout and Vbus relative to the time axis in a conventional system under standby conditions. It can be seen that in standby mode, the load switch is turned off and the voltage provided to the USB connector is 0V. However, the output of the power supply is still maintained at Vout. In addition, the USB PD controller is still fully functional and continues to consume power.

[0037] Figure 4 is a graph showing the waveforms of Vout and Vbus relative to the time axis under standby conditions embodying certain aspects of the present invention. Figure 4As shown in FIG. 4 , if no load device is connected, the load switch 140 is turned off and Vbus 410 is equal to 0V. In addition, the USB PD controller causes the primary side controller to stop regulating the output voltage. The USB PD controller is also set in a standby mode, in which the power supply to all functional blocks in the USB PD controller is turned off except for the circuits required to continue monitoring the status of the load device and the circuits used to monitor the output voltage of the converter. For example, this can be achieved by setting the feedback voltage (VFB) to a preset low value, such as in combination with Figures 5 to 8 Under this condition, the output voltage Vout 420 starts to decrease, as shown in FIG. Figure 4 During this time, the active circuit blocks can receive operating power from the charge stored in the capacitors in the system. Once the power supply output voltage Vout drops to the preset low voltage limit V L , the USB PD controller causes the primary side controller to start regulating, for example, by increasing the VFB signal, which causes the converter output voltage Vout to increase. When Vout increases and reaches the preset high voltage limit V H When no USB device is connected, the USB PD controller again causes the primary-side controller to stop regulating. L It can be a preset minimum operating voltage for the USB PD controller, which is sufficient to keep the remaining circuit blocks operating. As an example, the target converter output voltage Vout can be 5V, and the preset high voltage limit V H Can be 5V, and preset low voltage limit V L Can be 3V.

[0038] like Figure 4 As shown in FIG. 4 , Vout 420 exhibits a sawtooth shape with a first time period T1 of a decreasing voltage and a recovery to V H During the first time period T1, the operating power of the system is provided by the charge stored in the capacitors in the system. The USB PD controller shuts down unused circuit blocks during the second time period T1 to reduce power consumption, maintaining the remaining active circuit blocks without the power regulation function providing power. During the time period T1, the system is in power saving mode. During the time period T2, the system is in regulation mode. Therefore, the standby mode period can be described as having alternating time periods of power saving mode and regulation mode. Figure 4 The sawtooth cycle in is repeated until the USB PD controller senses that a USB device is connected. Therefore, a longer time period T1 may result in reduced power consumption. For example, depending on the circuit implementation and application, T1 may be in the range of 1-5 seconds or longer, and T2 may be in the range of 40-400 microseconds or shorter. Figure 4Also shown is Vout 430 during standby in a conventional system. Compared to the conventional system, Figure 1-4 The method described in the invention can produce a significantly reduced standby power. For example, the specification of the standby power of different switching power supplies can vary in the range of, for example, 15 mW to 75 mW. Using the techniques described in this article, by Figure 4 The standby power savings between the systems shown in FIG. 4A and FIG. 4B may be 10%-30% or more.

[0039] When the power supply is in standby mode, Figure 4 The sawtooth cycle in repeats until the USB PD controller senses that a USB device has been connected. At this point, the USB PD controller wakes up the primary side controller to resume normal regulation functions. In addition, the USB PD controller exits standby mode and restores power to all its functional blocks. Figure 5-8 Describe additional details.

[0040] According to certain aspects of the present invention, a method is presented that can reduce power consumption under standby conditions. Figure 1-4 In the embodiment, USB PD and Type-C devices are shown as examples. However, it should be understood that the method can be applied to any load device and power source. In addition, the PDIC circuit is only an example of a power management device disposed between the power source and the load device. In addition, the load switch is a power switch that can be an independent device, or the load switch can be integrated in a power management device such as a PD. In other words, the PDIC and the load switch can be two separate IC chips or built into a single chip. In other examples, the power management device (e.g., Figure 1 PDIC) and power switches (e.g. Figure 1 The load switch in the power supply can be integrated into the power supply.

[0041] In the method described above, a power management device (e.g., a PDIC) may include various functional blocks for implementing power management functions. In a normal operating mode, the power management device has full operational capabilities, with many or all functional blocks powered on. In a power saving mode, only the functional blocks required to monitor status signals from load devices and circuits required to control load switches are powered on. All other blocks may be powered off.

[0042] In other instances, other functions in the power management device may need to be activated.In the power save mode, functional blocks in the power management device may be selectively powered down depending on the particular application.

[0043] Figure 5 is a simplified schematic diagram showing a system having a power supply providing power to a USB PD device embodying certain aspects of the present invention. Figure 5As shown, SMPS 500 is a switch mode power supply having a universal serial bus power delivery (USB PD) controller 550. SMPS 500 includes a transformer 510 having a primary winding 511, a secondary winding 512, and an auxiliary winding 513 coupled in series to a power transistor 515. The primary winding 511 is used to couple to an alternating current power source AC via a rectifier circuit, which as an example includes a diode bridge formed by four diodes D1-D4 and a capacitor C1. The rectifier circuit provides a rectified DC voltage Vin to the SMPS. The secondary winding 512 is configured to provide an output voltage Vout of the SMPS to a load device.

[0044] A power switch 515 (also referred to as a power transistor) is coupled to the primary winding 511 for controlling the current flow in the primary winding. The primary side controller 520 receives a feedback signal 533 via a feedback input terminal FB and a current sensing signal 534 via a CS input terminal. The primary side controller 520 is configured to turn on and off the power switch 515 to regulate the SMPS. When the power switch 515 is turned on, the primary current Ip accumulates in the primary winding 511, thus storing energy. The energy stored in the primary winding 511 is transferred to the secondary winding 512 during the off time interval of the power switch 515. Rectifier elements such as a diode D6 and a smoothing capacitor C3 connected to the secondary winding 512 are configured to convert the secondary voltage Vs into a DC voltage Vout to supply to a load device.

[0045] exist Figure 5 In the example of , the load device is a USB device. SMPS 500 has a load switch 525 that couples secondary winding 512 to USB connector 570, which can be connected to USB device 590. USB connector 570 includes several pins, some of which are listed below:

[0046] Vo-used to receive the voltage supply Vsub from the SMPS 500;

[0047] GND - used to provide electrical grounding for load devices;

[0048] D- and D+- serial data interface pins; and

[0049] CC1 and CC2 - Configuration channels used for detecting signal direction and channel configuration.

[0050] The primary side controller 520 is configured to generate a control signal for turning on and off the power switch based on at least the feedback signal to regulate the output voltage of the SMPS at a target voltage. For example, the primary side controller may operate in a pulse width modulation (PWM) mode during normal operation. The primary side controller may operate in a burst mode during low load or no load conditions. In burst mode, one or more bursts of on pulses are issued at relatively long intervals to maintain the output voltage of the power supply at a target voltage.

[0051] like Figure 5 As shown, the USB PD controller 550 is coupled to the secondary winding 512 for providing support for USB power delivery operations. The USB PD controller 550 monitors the CC1 and CC2 signals from the USB connector 570 to determine whether a USB load device is connected to the SMPS, as well as other connection information. After determining that no USB load device is connected to the USB connector, the USB PD controller 550 causes the SMPS 500 to enter a standby mode. After determining that a USB load device is connected to the USB connector, the USB PD controller 550 causes the SMPS to enter an active mode.

[0052] As an example, to cause the SMPS 500 to enter the standby mode, the USB PD controller 550 turns off the load switch 525 to disconnect the output voltage Vout of the SMPS from the USB connector 570 and turns off one or more functional blocks in the USB PD controller 550. Figure 1-4 As described, the USB PD controller 550 causes the primary side controller to stop regulating, and monitors the output voltage Vout of the SMPS 500, and maintains the output voltage Vout within a range just sufficient to maintain the necessary functions to support the standby mode in order to reduce power consumption, such as Figure 4 For example, after determining that the output voltage Vout is higher than the high standby voltage limit VH, the USB PD controller 550 sets the feedback signal 533 to the feedback terminal of the primary side controller 520 to a first value to cause the primary side controller 520 to stop regulating the output voltage Vout and allow the output voltage Vout to drop. Figure 5 In the example of , the USB PD controller 550 sends a feedback signal 533 via the optocoupler 531. After determining that the output voltage Vout is lower than the low standby voltage limit VL, the USB PD controller 550 sets the feedback signal 533 to the primary side controller 520 via the optocoupler 531 to a second value, so that the primary side controller 520 starts to regulate the output voltage Vout and allows the output voltage to increase. This cycle repeats until a USB load device is connected and the USB PD controller 550 sets the SMPS 500 to the active mode.

[0053] In order to cause the SMPS 500 to enter the active mode, the USB PD controller 550 sets the feedback signal to the primary side controller 550 via the optocoupler 531 to a third value to cause the primary side controller to start regulating the output voltage in the active mode. For example, in the active mode, the primary side controller 550 may operate in a pulse width modulation (PWM) mode. The SB PD controller 550 also turns on the one or more functional blocks in the USB PD controller 550 to allow it to have full functionality. In addition, the USB PD controller 550 also turns on the load switch 525 to connect the output voltage Vout of the SMPS to the USB connector 570.

[0054] Figure 6 is a simplified block diagram of a primary side controller of a switch mode power supply embodying certain aspects of the present invention. Figure 6 As shown, the controller 600 is usable as Figure 5 An example of a controller of the primary side controller 520 of the SMPS 500 in FIG. Figure 6 As shown, the controller 600 has terminals VCC, GND, Vaus, FB, CS, SRC and OUT, etc. The controller 600 receives operating power via the input terminal VCC, and the GND terminal provides electrical grounding for the controller. At the Vaux terminal, the controller 600 senses a voltage related to the current of the auxiliary winding, which represents the state of the SMPS output. Several circuit blocks receive signals from the Vaux terminal and perform various functions. For example, circuit block 612 is configured for line compensation, circuit block 614 is configured for load detection, and circuit block 616 is configured to detect the valley line start function. The outputs from these control blocks are coupled to the logic control block 620, which performs various functions as described below. Block 662 is a startup regulator, and block 664 includes various protection circuits and support circuits.

[0055] exist Figure 6 In the example of , the logic control block 620 may send a control signal to the gate driver block 640 to turn on the power switch in response to the turn-on signal from the secondary side, and turn off the power switch when the primary current reaches a peak current reference level, which is also referred to as a primary current reference level or a peak primary current level. Figure 6 As shown, the turn-on signal from the secondary side is received at the FB terminal, which is coupled to the current source 634 and the input of the comparator 632. Another input of the comparator 632 is coupled to the reference signal Vref1. The comparator 632 provides the PW_ON signal to the logic control block 620, which is coupled to the gate drive block to provide a control signal for turning on the power switch at the OUT terminal.

[0056] The other terminal of the comparator 654 receives a voltage signal Vcs, which is related to the limit of the peak primary current. Figure 6 In the example of , the logic control block 620 provides the Vcs signal via a digital / analog converter (DAC) 652. When the current sense signal at the terminal CS reaches the peak current reference signal Vcs, the comparator 654 sends a signal Tonp to the logic control block 620, which sends a control signal at the OUT terminal via the gate driver 640 to turn off the power switch.

[0057] In some instances, the logic control block 620 may provide a pulse width modulation (PWM) signal to control the power switch to regulate the power supply in normal mode operation. In low load or no load conditions, the logic control block 620 may operate in a burst mode, in which bursts of on pulses are issued at relatively long intervals to maintain the output voltage of the power supply at a target voltage. In addition, in standby mode or power save mode, the logic control block 620 may stop regulating the power supply and allow the secondary side controller to monitor the output voltage. In this case, the secondary side controller may issue a wake-up signal to cause the primary side controller to resume the regulation function. For example, the standby mode may be triggered by the primary side controller receiving a signal at the FB terminal that is lower than the Vref1 reference voltage. The wake-up signal may be a signal at the FB terminal that is higher than the Vref1 reference voltage. In Figure 5 In the example of , the FB terminal receives a feedback signal via an optocoupler 531. If the feedback signal is lower than, for example, 0.6V, the primary side controller stops regulating the power switch.

[0058] Figure 7 is a simplified block diagram of a secondary side controller of a switch mode power supply embodying certain aspects of the present invention. Figure 7 As shown, Figure 7 The secondary side controller 700 is usable as Figure 5 The USB PD controller 550 in the SMPS 500 is an example of a controller, and is referred to in the following description. Figure 5Components in. The controller 700 includes: a first terminal VCC for coupling to the secondary winding 512 of the SMPS 500 to provide an output voltage Vout to the USB connector 570; a second terminal PWR_EN, providing a control signal to a load switch 525 coupled between the secondary winding and the USB connector; and a third terminal OCDRV, for driving the optocoupler 531 to provide a feedback signal 533 to the primary side controller of the SMPS. The secondary side controller 700 also includes terminals D+, D-, CC1 and CC2 for receiving corresponding signals from the USB connector 570. The secondary side controller 700 also includes additional terminals. For example, the GND terminal provides electrical grounding, the ISEN terminal is used to sense the current in the secondary winding, and the VBUS terminal is connected to the voltage VBUS provided to the USB connector 570, and so on.

[0059] The secondary side controller 700 includes several functional blocks. For example, the control logic 710 works with other functional blocks to implement the functions of the secondary side controller 700. The USB block 720 receives signals from the USB connector 570 and is responsible for the power delivery protocol for communication between the adapter and the device. For example, the USB block 720 may include a decoder 721 for monitoring the CC1 and CC2 signals from the USB connector to determine whether the USB device is connected. The OSC block provides an oscillator for the controller. The LDO (low dropout) circuit provides a regulated voltage for the controller and the connector. The ROM block provides a read-only memory. The SENSE block performs output current sensing and feedback for overcurrent protection and current control. Block 730 provides constant voltage (CV) and constant current (CC) control, as further described below.

[0060] The secondary side controller 700 is coupled to the secondary winding for providing constant voltage (CV) and constant current (CC) control of the SMPS. The secondary side controller 700 may receive an output selection signal. For example, the output selection signal may be received at the D+ and D- terminals. Based on the output selection signal, the secondary side controller 700 may select a target voltage reference signal and / or select a target current reference signal. The secondary side controller 700 may monitor the output voltage and output current of the SMPS to determine whether the output voltage is lower than the target voltage reference signal, and whether the output current is lower than the target current reference signal. After determining that the output voltage is lower than the selected voltage reference signal and the output current is lower than the selected current reference signal, the secondary side controller 700 may provide a turn-on signal to the primary side controller to turn on the power switch. The primary side controller may turn on the power switch in response to the turn-on signal from the secondary side. In some embodiments, the primary side controller may turn off the power switch when the primary current reaches a peak primary current reference level.

[0061] exist Figure 7In the embodiment of the present invention, the selected voltage reference signal CV_vref is coupled to the comparator CV_comp (722), and the selected current reference signal CC_vref is coupled to another comparator CC_comp (724). The controller 700 also monitors the output voltage and output current of the SMPS. The VCC terminal provides information about the output of the SMPS, and the ISEN terminal is configured to provide information about the current in the secondary winding. Based on the information provided by the comparators 722 and 724, the CV&CC logic circuit 726 in the controller 700 determines whether the output voltage is lower than the selected voltage reference signal, and whether the output current is lower than the selected current reference signal. After determining that the output voltage is lower than the selected voltage reference signal and the output current is lower than the selected current reference signal, the control circuit 700 further provides a turn-on signal to the primary side controller to turn on the power switch. In this example, the turn-on signal is coupled to the terminal OCDRV, and the terminal OCDRV is coupled to the optocoupler for providing the signal to the primary side controller. In other embodiments, the communication between the primary side controller and the secondary side controller can be achieved by different means, such as via inductive coupling through a transformer.

[0062] The control logic 710 provides control for the power saving functions described above. For example, the control logic 710 monitors the CC1 and CC2 signals from the USB connector to determine whether a USB load device is connected. After determining that the USB load device is connected to the USB connector, the control logic 710 causes the SMPS to enter a standby mode. After determining that the USB load device is connected to the USB connector, the control logic 710 causes the SMPS to enter an active mode. In the standby mode, the control logic 710 turns off the load switch to disconnect the output voltage of the SMPS from the USB connector, and turns off one or more functional blocks in the USB PD controller to reduce power consumption. For example, in the standby mode, the block 730 may be turned off together with the protection block, the SENSE block, the switch coupled to the VBUS terminal, and the portion of the USB block 720 that handles the PD prototype function, etc.

[0063] The control logic 710 also monitors the output voltage of the SMPS and performs the following functions. Upon determining that the output voltage is above the high standby voltage limit, the control logic 710 sends a first feedback signal to the primary side controller via the optocoupler to cause the primary side controller to stop regulating the output voltage and allow the output voltage to drop. Upon determining that the output voltage is below the low standby voltage limit, the control logic 710 sends a second feedback signal to the primary side controller via the optocoupler to cause the primary side controller to start regulating the output voltage and allow the output voltage to increase.

[0064] To enter the active mode, the control logic 710 sends a third feedback signal to the primary side controller 550 via the optocoupler 531 to cause the primary side controller to start regulating the output voltage in the active mode. The control logic 710 also turns on the one or more functional blocks in the USB PD controller 550 to allow it to have full functionality. In addition, the control logic 710 also turns on the load switch 525 to connect the output voltage Vout of the SMPS to the USB connector 570.

[0065] Figure 7 An example of a secondary side controller that can be used as a universal serial bus power delivery (USB PD) controller has a first terminal for coupling to a secondary winding of a switch mode power supply (SMPS) to receive operating power, a second terminal for providing a control signal to a load switch coupled between the secondary winding and a USB connector, and a third terminal for providing a feedback signal to a primary side controller of the SMPS. The USB PD controller also has a decoder for monitoring CC1 and CC2 signals from the USB connector to determine whether a USB device is connected. The control logic in the USB PD controller is configured to monitor CC1 and CC2 signals from the USB connector to determine whether a USB load device is connected. After determining that no USB load device is connected to the USB connector, the control logic turns off the load switch to disconnect the secondary winding from the USB connector and enter a standby mode. The standby mode includes a first time period of an alternating power saving mode and a second time period of a regulating mode. In the power saving mode, the control logic stops regulating the output of the power supply and turns off one or more functional blocks to allow the output to drop until the output reaches a preset low output limit. In the regulation mode, the control logic turns on the functional block and regulates the power supply to allow the output to increase until the output reaches the preset high output limit. After determining that a USB load device is connected to the USB connector, the control logic enters the normal mode, in which the control logic regulates the output of the power supply, the functional block is powered on, and the load switch is turned on to connect the load device to the power supply.

[0066] Figure 8is a simplified flow chart illustrating a method for reducing standby power in a power supply embodying certain aspects of the present invention. In one example, the power supply has a control circuit for regulating the output of the power supply, and a load switch for connecting the output of the power supply to a load device. The method includes determining whether a load device is connected to the power supply. In response to determining that no load device is connected to the power supply, the method includes turning off the load switch to disconnect from the load device and entering a standby mode. The standby mode includes alternating a first time period of a power saving mode and a second time period of a regulation mode. In the power saving mode, the control circuit stops regulating the output of the power supply and turns off one or more functional blocks to allow the output to decrease until the output reaches a preset low output limit. In the regulation mode, the control circuit turns on the functional blocks and regulates the power supply to allow the output to increase until the output reaches a preset high output limit. On the other hand, in response to determining that a load device is connected to the power supply, the method includes entering a normal mode in which the control circuit regulates the output of the power supply, the functional blocks in the control circuit are energized, and the load switch is turned on to connect the load device to the power supply. Figure 8 An example is further shown in the flowchart in .

[0067] like Figure 8 As shown, method 800 starts at 801 and includes determining whether a load device is connected to the output of a power supply at 803. For the USB PD example described above, process 803 may include checking the CC pin to determine whether a USB PD protocol is detected to determine whether a USB device is connected. However, other connections and protocols may also be used. If a load device is connected, then at 805, the power supply is set to normal mode, the power supply is adjusted to provide the desired output, and the load switch is turned on to connect the load device. After determining that no load device is connected, at 807, the method sets the power supply to standby mode.

[0068] Standby mode Figure 8 The dashed box in FIG. 1 shows that the load switch is turned off and includes a first time period of alternating power saving mode and a second time period of regulating mode. Figure 4 In the example shown in FIG. 1 , the power saving mode is a first time period T1 and the regulation mode is a second time period T2. In the power saving mode, the control circuit stops regulating the output of the power supply and turns off one or more functional blocks to allow the output to decrease until the output reaches a preset low output limit. In the regulation mode, the control circuit turns on the functional blocks and regulates the power supply to allow the output to increase until the output reaches a preset high output limit.

[0069] At 811, similar to 803, the method checks whether a load device is connected. If so, then at 805 the power supply enters normal mode. If no device is connected, then at 813 the output (voltage or current) of the power supply is checked to see if a preset low output limit is reached. If not, then at 815 regulation of the power supply is stopped, unused functional blocks are shut down, and the output is allowed to drop. The method then loops to 811.

[0070] At 813 , if the output drops below the preset low output limit, the method proceeds to 825 where the power supply is set to a regulation mode and the output is regulated and allowed to increase.

[0071] From 825, the method proceeds to 821, where the connection of the load device is checked again. If the load device is connected, the method proceeds to 805 to enter the normal mode. If no load device is connected, at 823, the output of the power supply is compared with the preset high output limit.

[0072] At 823, if the preset high output limit is reached, the method proceeds to 815 to enter a power saving mode to maintain the output within a range between a preset low output limit and a preset high output. If the output has not reached the preset high output limit, the power supply stays in the regulation mode.

[0073] exist Figure 1-7 In an example, in the power saving mode, the secondary side controller turns off the load switch and turns off unused functional blocks. The method 800 may also include the secondary side controller sending a first feedback signal to the primary side controller, and in response, the primary side controller stops regulating the power supply. The method 800 may also include the secondary side controller sending a second feedback signal to the primary side controller, and in response, the primary side controller stops regulating the power supply and further turns off one or more functional blocks in the primary side controller to further reduce power consumption. The method 800 may also include the secondary side controller sending a third feedback signal to the primary side controller, and in response, the primary side controller turns on the functional block and starts regulating the power supply.

[0074] Reference is made above in the context of an SMPS with a secondary side controller acting as a USB PD controller. Figure 1-7An example of method 800 is described. The method may also include the secondary side controller sending a first feedback signal to the primary side controller, and in response, the primary side controller stops regulating the power supply. Alternatively, the method may also include the secondary side controller sending a second feedback signal to the primary side controller, and in response, the primary side controller stops regulating the power supply and shuts down one or more functional blocks in the primary side controller to further reduce power consumption. In addition, the method may include the secondary side controller sending a third feedback signal to the primary side controller, and in response, the primary side controller turns on one or more functional blocks and regulates the power supply.

[0075] It should be understood that the examples and embodiments described herein are for illustrative purposes only, and that various modifications or changes thereto should be thought of by a person skilled in the art and be included in the spirit and scope of the present application and the scope of the present invention. For example, in the examples described above, the output voltage is referred to as a control parameter. However, the power supply also includes a current regulation function, and the output of the power supply may also refer to the output current, or both the output voltage and the output current. In addition, the power supply is not limited to a switch mode power supply. Although a pulse width modulation (PWM) controller is used in the above description, a pulse frequency modulation (PFM) controller may also be used. In addition, the method may also be implemented in other power supplies or converters without substantial modification. For example, Figure 8 The method shown in can also be applied to isolated and non-isolated converters and linear regulators, etc.

Claims

1. A universal serial bus power delivery USB PD controller, comprising: a first terminal VCC for coupling to a secondary winding of a switch mode power supply SMPS to receive an output voltage of said SMPS for operating power; a second terminal PWR_EN providing a control signal to a load switch coupled between the secondary winding and a USB connector; a third terminal OCDRV for providing a feedback signal to a primary side controller of the SMPS; a decoder for monitoring CC1 and CC2 signals from the USB connector to determine whether a USB device is connected; a constant voltage and constant current control circuit block comprising a constant voltage circuit having a first input coupled to the first terminal for receiving the output voltage and a second input coupled to a voltage reference signal for comparing the output voltage of the SMPS with a voltage reference signal, the control circuit block providing the feedback signal to the primary side controller; as well as Control logic; The USB PD controller is configured to: monitoring CC1 and CC2 signals from the USB connector to determine whether a USB load device is connected; after determining that no USB load device is connected to the USB connector, turning off the load switch to disconnect the secondary winding from the USB connector and entering a standby mode; wherein the standby mode comprises alternating first time periods of a power saving mode and second time periods of a regulation mode; In the power save mode, the USB PD controller stops regulating the output of the power supply and shuts down one or more functional blocks to allow the output to decrease until the output reaches a preset low output limit, at which time the control circuit block sets the feedback signal to a first value to cause the primary side controller to enter the regulation mode to allow the output to increase; and In the regulation mode, the USB PD controller turns on the functional block and regulates the power supply to allow the output to increase until the output reaches a preset high output limit, at which time the control circuit block sets the feedback signal to a second value to cause the primary side controller to enter the power save mode and stop regulation; After determining that a USB load device is connected to the USB connector, the normal mode is entered, wherein the USB PD controller: Setting the voltage reference signal in the control circuit block of the USB PD controller as a target voltage reference signal, and sending the feedback signal to the primary-side controller, so that the primary-side controller starts regulating the output voltage under the control of the USB PD controller; and The load switch is turned on to connect the output voltage of the SMPS to the load device. 2 . The Universal Serial Bus Power Delivery (USB PD) controller of claim 1 , wherein the USB PD controller is configured to send a feedback signal to the primary-side controller via an optocoupler.

3. A switch mode power supply (SMPS) having a universal serial bus power delivery (USB PD) controller, comprising: a transformer having a primary winding for coupling to an external input voltage and a secondary winding for providing an output voltage of the SMPS; a load switch coupling the secondary winding to a USB connector; a power switch for coupling to the primary winding of the SMPS; a primary side controller coupled to the power switch to control the power switch, the primary side controller comprising a feedback terminal FB for receiving a feedback signal representative of the output voltage of the SMPS via an optocoupler, wherein: The primary side controller is configured to generate a control signal for turning the power switch on and off based at least on the feedback signal to regulate the SMPS to allow the output to increase; and The primary side controller operates in a pulse width modulation (PWM) mode during normal operation, and the primary side controller operates in a burst mode during low load or no load conditions; A USB PD controller is coupled to the secondary winding for providing support for USB power delivery operations, the USB PD controller comprising: a first terminal VCC for coupling to a secondary winding of a switch mode power supply SMPS to receive an output voltage of the SMPS for operating power; a second terminal PWR_EN providing a control signal to a load switch coupled between the secondary winding and a USB connector; a third terminal OCDRV for providing the feedback signal to a primary side controller of the SMPS; a decoder for monitoring CC1 and CC2 signals from the USB connector to determine whether a USB device is connected; and a control circuit block (730) comprising a constant voltage CV control circuit for comparing the output voltage of the SMPS with a voltage reference signal, the control circuit block providing the feedback signal to the third terminal; and Control logic; The USB PD controller is configured as follows: monitoring CC1 and CC2 signals from the USB connector; In active mode, upon determining that no USB load device is connected to the USB connector, causing the SMPS to enter standby mode; and In the standby mode, upon determining that a USB load device is connected to the USB connector, causing the SMPS to enter an active mode; Wherein, in order to cause the SMPS to enter the standby mode, the USB PD controller is configured to: turning off the load switch to disconnect the output voltage of the SMPS from the USB connector; shutting down one or more functional blocks in the USB PD controller; monitoring the output voltage of the SMPS; After determining that the output voltage is higher than a high standby voltage limit, setting the feedback signal to the primary-side controller via the optocoupler to a second value lower than a preset voltage value, so that the primary-side controller stops regulating the output voltage and allows the output voltage to drop; and After determining that the output voltage is below a low standby voltage limit, setting the feedback signal to the primary side controller via the optocoupler to a first value so that the primary side controller begins regulating the output voltage and allows the output voltage to increase; and Wherein, in order to cause the SMPS to enter the active mode, the USB PD controller is configured to: Turning on the one or more functional blocks in the USB PD controller; setting the voltage reference signal in the control circuit block of the USB PD controller to a target voltage reference signal and sending the feedback signal to the primary-side controller via the optocoupler to cause the primary-side controller to start regulating the output voltage under the control of the USB PD controller; and The load switch is turned on to connect the output voltage of the SMPS to the USB connector.

4. The switch mode power supply of claim 3, wherein the load switch is a MOS transistor.

5. A method for reducing standby power in a switch mode power supply (SMPS), the switch mode power supply having a transformer including a primary winding and a secondary winding, a power switch coupled to the primary winding, a primary side controller, a secondary side controller, and a load switch coupled between the primary winding and an output connector, wherein the secondary side controller comprises a control circuit block, the control circuit block comprising a constant voltage circuit for comparing an output voltage of the SMPS with a voltage reference signal, the control circuit block providing a feedback signal to a third terminal, the method comprising: In the secondary side controller, determining whether a load device is connected to the output connector; After determining that a load device is connected to the SMPS, operating the SMPS in a normal mode, wherein the secondary-side controller turns on the load switch and sets the voltage reference signal in the control circuit block of the secondary-side controller to a target voltage reference signal, and sends the feedback signal to the primary-side controller, so that the primary-side controller starts regulating the output voltage under the control of the secondary-side controller; After determining that no load device is connected to the SMPS, turning off the load switch and operating the SMPS in a standby mode, which includes alternating a first time period of a power saving mode and a second time period of a regulation mode, wherein: In the power save mode, the secondary side controller stops regulating the output of the power supply and shuts down one or more functional blocks to allow the output to decrease until the output reaches a preset low output limit, at which time the control circuit block sets the feedback signal to a first value to cause the primary side to enter the regulation mode to allow the output to increase under the control of the secondary side controller; and In the regulation mode, the secondary side controller turns on the functional block and regulates the power supply to allow the output to increase until the output reaches a preset high output limit, at which time the control circuit block sets the feedback signal to a second value to cause the primary side to enter the power save mode and stop regulating. The method of claim 5 , wherein the secondary-side controller is a Universal Serial Bus Power Delivery (USBPD) controller. 7 . The method of claim 6 , further comprising monitoring CC1 and CC2 signals to determine whether a PD protocol is detected and whether a load device is connected to the SMPS. The method of claim 5 , wherein the power supply is a non-isolated power supply.

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