Power converters with quasi-zero power consumption

A power converter system, method and device powers a load when coupled to the load and draws a quasi-zero amount of power from the power supply when not coupled to the load. The power converter system maintains an output voltage such that the power converter system is able to properly “wake-up” when a load is coupled by intermittently operating the power converter for a preselected number of cycles when it is detected that the output voltage has fallen below a threshold level.

FIELD OF THE INVENTION

The present invention relates to the field of power supplies. More particularly, the present invention relates to a power converter system with a quasi-zero power consumption feature.

BACKGROUND

Previously, restrictions on power converter efficiency centered around the efficiency at which the power converter is able to transfer the power received from the mains to the load for consumption. Recently however, greater restrictions have been introduced centering on the efficiency of power converters when no load is present. In particular, this efficiently relates to how much power is consumed by chargers when the device to be charged is disconnected and when cell phones, set top boxes, laptops and other electronic devices are in standby or sleep modes. Thus far, this type of efficiency has been problematic to achieve because it is difficult to design a power converter that does not use much power when a load is not connected, but is able to properly “wake-up” and provide the needed power when a load is connected.

SUMMARY OF THE INVENTION

A power converter system, method and device powers a load when coupled to the load and draws a quasi-zero amount of power from the power supply when not coupled to the load. The power converter system maintains an output voltage such that the power converter system is able to properly “wake-up” when a load is coupled by intermittently operating the power converter for a preselected number of cycles when it is detected that the output voltage has fallen below a threshold level. The small ratio of operation time required to recharge the output voltage compared to the time required for the output voltage to decay enables the power converter system to operate according to an almost or quasi-zero duty cycle. As a result, the efficiency of the power converter when not connected to the load is maximized.

One aspect of the present invention is directed to a power converter system for powering a load when coupled to the load and for drawing a quasi-zero amount of power when not coupled to the load. The system comprises a power supply for supplying an input power, a power converter coupled with the power supply, wherein the power converter produces an output voltage from the input power and a wake-up element coupled to the power converting element, wherein when the load is disconnected from the power converter and the output voltage drops below a threshold voltage the wake-up element causes the power converter to recharge the output voltage to a predefined sleep voltage. The power converter is a switch mode power supply having a switching signal comprising one or more cycles, wherein the switching signal controls when input power is drawn from the power supply to produce the output voltage. In some embodiments, the wake-up element causes the power converter to recharge the output voltage to the predefined sleep voltage by causing the power converter to operate until the wake-up element detects that the output voltage equals the predefined sleep voltage. In some embodiments, the wake-up element causes the power converter to recharge the output voltage to the predefined sleep voltage by causing the power converter to operate for a predetermined number of the switching signal cycles. In some embodiments, the predefined sleep voltage equals the maximum operating voltage of the load and the threshold voltage equals the minimum operating voltage of the load. In some embodiments, the predetermined number of switching signal cycles equals the number of cycles required to maximize the ratio of the time that the output voltage takes to drop to the threshold voltage versus the combined period of the predetermined number of switching signal cycles. In some embodiments, the predetermined number of switching signal cycles equals the number of cycles required to minimize the duty cycle of the power converter while keeping the output voltage above the threshold voltage. In some embodiments, the predetermined number of switching signal cycles equals the minimum amount of cycles required to recharge the output voltage to the predefined sleep voltage. In some embodiments, the power converter and the wake-up element are a part of a single integrated circuit.

A second aspect of the present invention is directed to a power converter device for powering a load when coupled to the load and for drawing a quasi-zero amount of power when not coupled to the load. The device comprises a power converter configured to produce an output voltage from an input power and a wake-up element coupled to the power converter, wherein when the load is disconnected from the power converter and the output voltage drops below a threshold voltage the wake-up element causes the power converter to recharge the output voltage to a predefined sleep voltage. The power converter is a switch mode power supply having a switching signal comprising one or more cycles, wherein the switching signal controls when input power is drawn from the power supply to produce the output voltage. In some embodiments, the wake-up element causes the power converter to recharge the output voltage to the predefined sleep voltage by causing the power converter to operate until the wake-up element detects that the output voltage equals the predefined sleep voltage. In some embodiments, the wake-up element causes the power converter to recharge the output voltage to the predefined sleep voltage by causing the power converter to operate for a predetermined number of the switching signal cycles. In some embodiments, the predefined sleep voltage equals the maximum operating voltage of the load and the threshold voltage equals the minimum operating voltage of the load. In some embodiments, the predetermined number of switching signal cycles equals the number of cycles required to maximize the ratio of the time that the output voltage takes to drop to the threshold voltage versus the combined period of the predetermined number of switching signal cycles. In some embodiments, the predetermined number of switching signal cycles equals the number of cycles required to minimize the duty cycle of the power converter while keeping the output voltage above the threshold voltage. In some embodiments, the predetermined number of switching signal cycles equals the minimum amount of cycles required to recharge the output voltage to the predefined sleep voltage. In some embodiments, the power converter and the wake-up element are a part of a single integrated circuit.

Another aspect of the present invention is directed to a method of powering a load with a power supply when coupled to the load and for drawing a quasi-zero amount of power from the power supply when not coupled to the load. The method comprises detecting if the load is coupled with a power converter with a wake-up element, detecting an output voltage of the power converter with the wake-up element, transmitting a recharge signal from the wake-up element to the power converter if the load is not coupled with the power converter and the output voltage is below a threshold voltage and recharging the output voltage to a predefined sleep voltage with the power converter upon receiving the recharge signal. The power converter is a switch mode power supply having a switching signal comprising one or more cycles wherein the switching signal controls when input power is drawn from the power supply to produce the output voltage. In some embodiments, the recharging comprises operating the power converter until the wake-up element detects that the output voltage equals the predefined sleep voltage. In some embodiments, the recharging comprises operating the power converter for a predetermined number of the switching signal cycles. In some embodiments, the predefined sleep voltage equals the maximum operating voltage of the load and the threshold voltage equals the minimum operating voltage of the load. In some embodiments, the predetermined number of switching signal cycles equals the number of cycles required to maximize the ratio of the time that the output voltage takes to drop to the threshold voltage versus the combined period of the predetermined number of switching signal cycles. In some embodiments, the predetermined number of switching signal cycles equals the number of cycles required to minimize the duty cycle of the power converter while keeping the output voltage above the threshold voltage. In some embodiments, the predetermined number of switching signal cycles equals the minimum amount of cycles required to recharge the output voltage to the predefined sleep voltage. In some embodiments, the power converter and the wake-up element are a part of a single integrated circuit.

DETAILED DESCRIPTION

In the following description, numerous details and alternatives are set forth for the purpose of explanation. However, one of ordinary skill in the art will realize that the invention can be practiced without the use of these specific details. In other instances, well-known structures and devices are shown in block diagram form in order not to obscure the description of the invention with unnecessary detail.

Embodiments of a power converter system, device and method are described herein. The power converter system, device and method power a load when coupled to the load and draw a quasi-zero amount of power from the power supply when not coupled to the load. The power converter system maintains an output voltage such that the power converter system is able to properly “wake-up” when a load is coupled by intermittently operating the power converter for a preselected number of cycles when it is detected that the output voltage has fallen below a threshold level. The small ratio of operation time required to recharge the output voltage compared to the time required for the output voltage to decay enables the power converter system to operate according to an almost or quasi-zero duty cycle. As a result, the efficiency of the power converter when not connected to the load is maximized.

FIG. 1illustrates a functional block diagram of a power converter system100according to some embodiments. As shown inFIG. 1, the system100comprises a power source102, a power converter104, a load106and a wake-up element108. The power source102is electrically coupled with the power converter104which is able to selectively couple or decouple with the load106at a coupling point110. The wake-up element108is electrically coupled between the coupling point110and the power converter104. In some embodiments, two or more of the power converter104, wake-up element108and load106are integrated on a single integrated circuit. Alternatively, one or more of the power converter104, wake-up element108and load106are able to be on separate integrated circuits.

The power source102is able to comprise an AC power source such as a main line or plug outlet. Alternatively, the power source102is able to comprise a DC power supply. The power converter104is able to comprise a power converter circuit, such as a flyback converter. Alternatively, the power converter104is able to comprise other types of circuits that include power converters as are well known in the art. For example, the power converter104is able to comprise a forward converter, a push-pull converter, a half-bridge converter, a full-bridge converter and/or other configurations of switch mode power supplies as are well known in the art. The wake-up element108is able to comprise a low power consuming voltage sensing circuit that is able to monitor the output voltage Vout, and the coupling status of the load106and control the operation of the power converter104accordingly. The load106is able to comprise a mobile phone, laptop, set top box, television or other type of electronic device. The coupling point110is able to be a physical coupling point and/or an electronic coupling point. Specifically, in some embodiments the coupling point110is a physical coupling point wherein, for example, the load106is a cell phone and the power converter104and wake-up element108comprise a cell phone charger such that the load106and the converter104are physically coupled and decoupled as the cell phone is coupled and decoupled from the charger. Alternatively, in some embodiments the coupling point110is an electronic coupling point wherein, for example, the load106, the power converter104and wake-up element108all comprise parts of a laptop computer such that the load106and the converter104are electronically coupled and decoupled as the laptop is put into and out of a sleep/hibernation mode.

In operation, the power converter104draws power from the power source102and produces an output voltage Voutthat is able to be used to power the load106when the load106is coupled to the power converter104. The wake-up element108monitors whether the load106is coupled to the power converter104and the output voltage Vout. If the wake-up element108detects that the load106is not coupled to the power converter104and the output voltage Voutis within a desired range or above a predetermined threshold voltage level, the wake-up element108interrupts or stops the normal operation of the power converter104in order to prevent the converter104from drawing power from the power source. If the wake-up element108detects that the load106is not coupled to the power converter104and the output voltage Voutis outside the desired range or below the predetermined threshold voltage level, the wake-up element108stops interrupting the operation of the power converter104and causes the power converter104to run in order to recharge the voltage Voutwithin the desired range and/or above the predetermined threshold. In some embodiments, the wake-up element108monitors the value of the output voltage Voutwhile causing the power converter104to recharge the output voltage Voutand stops the power converter104from the recharging as soon as the value of the output voltage Voutreaches a desired wake-up voltage value. Alternatively, the wake-up element108is able to be configured to cause the power converter104to recharge the output voltage Voutfor a predetermined wake-up period and to stop the power converter104after the wake-up period has elapsed. In particular, the wake-up period is able to be a number of pulse cycles that will result in increasing the value of the output voltage Vouta desired voltage amount or to a desired voltage level. Alternatively, the wake-up period is able to be a different length of time. As a result, the system100is able to minimize the amount of power consumed from the power source102by the power converter104when the load106is not coupled with the power converter104. Indeed, because the time required to recharge the output voltage Voutis generally orders of magnitude shorter than the time it takes that added voltage to decay from the output voltage Vout, the duty cycle of the power converter104(e.g. the time the converter104is operating compared to the time the converter104is not operating) approaches zero. Thus, the system100provides the benefit of increased power saving efficiency in no load conditions.

FIG. 2illustrates a schematic diagram of a power converter system200according to some embodiments. The schematic diagram is substantially similar to the functional block diagram shown inFIG. 1except the additional details described herein. However, it is understood that alternative schematics are able to be used to implement the functional blocks ofFIG. 2. As shown inFIG. 2, the power converter system200comprises a power source202, a power converter204having a coupling point210, a load206and a wake-up element208. In some embodiments, the system200is contained on a single integrated circuit. Alternatively, one or more of the components of the system200are able to be separate integrated circuits such that the system200is formed by multiple integrated circuits electrically coupled together.

The power source202comprises an AC mains power signal that is electrically coupled with a rectifier218in order to produce a DC input voltage Vin that is electrically coupled to the power converter204. The load206comprises a resistor Rloadthat represents the resistance provided by the load206. In particular, it is understood that the load206is able to comprise numerous different combination of circuitry that are able to be represented by the resistance of the resistor Rload, the details of which are omitted for the sake of brevity. The wake-up element208comprises a wake-up circuit that is able to detect the output voltage Voutand the coupling status of the load206while consuming a minimal amount of power. The power converter204comprises a transformer T1, a transistor212, one or more resistors R1, R2, R3, R4, a controller device214, one or more capacitors C1, Cout, one or more diodes D1, D2and a power saving element216. It is understood however, that one or more of the components of the power source202, the power converter204, the load206and/or the wake-up element208are able to be positioned or duplicated on one or more of the other elements202-210.

A primary end of the transformer T1is electrically coupled between the input voltage Vin received from the power source202and the drain terminal of the transistor212whose gate terminal is electrically coupled with the controller214and source terminal is electrically coupled with ground via the resistor R2. This enables the controller214to draw power into the transformer T1by outputting a transistor control signal to the gate terminal of the transistor212. One of the secondary ends of the transformer T1is electrically coupled across the diode D1and capacitor Coutto the coupling point210and a second of the secondary ends of the transformer T1is electrically coupled between ground and the controller214via the diode D2and the power saving element216. Further, the power saving element216is coupled with the input voltage Vin and ground via the resistor R1and the capacitor C1, respectively. As a result, the power drawn into the primary end of the transformer T1is able to be transferred to the capacitor Coutat the coupling point210via the first secondary end as well as recycled into the capacitor C1and the controller214via the second secondary end. The controller214is electrically coupled with a reference voltage Vref at a node between the resistor R3and ground, and the resistor R4and the output voltage Vout. The wake-up element208is electrically coupled across the output capacitor Coutand the coupling point210in order to detect the output voltage Voutand whether the load206is coupled to the power converter204. The wake-up element208is also electrically coupled with the power saving element216in order to control the power saving element216.

In some embodiments, the transformer T1is a flyback transformer. Alternatively, the transformer T1is able to be other types of transformers or load isolating circuitry as are well known in the art. In some embodiments, the transistor212is a field effect transistor such as a n-type metal-oxide-semiconductor field-effect transistor (MOSFET). Alternatively, the transistor212is able to be other types of transistors or switching circuitry as are well known in the art. In some embodiments, the controller device214is a SR-NOR latch flip flop. Alternatively, the controller214is able to be other types of flip flops, pulse width modulation circuits or signal logic circuitry able to regulate the duty cycle or operation of the transistor212as are well known in the art. In some embodiments, the power saving element216comprises an electrically controlled switch. Alternatively, the power saving element216is able to comprise other types of electric selectively isolating components or combinations of components as are well known in the art. In some embodiments, the size of the output capacitor Coutis selected based on charge decay time such that the length of the decay period between a starting voltage and the threshold voltage is maximized. Alternatively, any size output capacitor Coutis able to be used.

In operation, when the load206is coupled to the power converter204, the controller214of the power converter204outputs a transistor control signal having one or more pulse cycles to the gate terminal of the transistor212that causes the transistor212to repeatedly turn on and off as the pulse cycles alternate between high and low states. As a result, power from the power source202is alternately drawn into the transformer T1and discharged to the output capacitor Coutsuch that the output capacitor Coutis charged to an output voltage Voutthat is supplied to the load206. A portion of the power is discharged to the capacitor C1and the controller214via the power saving element216. This portion of the power is able to be used/recycled by the controller214in order to continue to output the transistor control signal.

Concurrently, the wake-up element208monitors the output voltage Vouton the output capacitor Coutand the load206connection status. If the wake-up element208detects that the load206is coupled with the power converter204, the wake-up element208transmits a command signal to the energy saving element216that causes the energy saving element216to keep the input voltage Vin, the transformer T1and the capacitor C1coupled to the controller214such that the controller214is able to operate normally. Alternatively, the energy saving element216is able to be omitted or able to keep the input voltage Vin, the transformer T1and the capacitor C1coupled to the controller214by default such that the command signal from the wake-up element208is able to be omitted. If the wake-up element208detects that the load206is not coupled with the power converter204and the output voltage Voutis above a threshold voltage or within a desired range, the wake-up element208transmits a command signal to the power saving element216that causes the power saving element216to disconnect or otherwise prevent the input voltage Vin, the transformer T1and the capacitor C1from communicating with the controller214such that the normal operation of the controller214is stopped. Alternatively, the wake-up element208is able to directly couple and send the command signal to the controller214such that although the input voltage Vin, the transformer T1and the capacitor C1remain coupled with the controller214, they are able to be disregarded by the controller214based on the commands received from the wake-up element208and the controller214is prevented from wasting power. In some such embodiments, the power saving element216is able to be incorporated into the controller214or omitted. In some embodiments, the desired range is able to be based on the load206and the threshold voltage is able to be the minimum voltage that the load206is able to receive upon recoupling to the power converter204without resulting in an error. This prevents the controller214from wasting power by continually attempting to recharge the output voltage Vout. In particular, because the output capacitor Coutacts like a battery when the load206is decoupled, the output voltage Vouton the capacitor Couttakes up to hundreds of milliseconds to decay tenths of a volt. As a result, the recharging of the output voltage Voutis able to be delayed for hundreds of milliseconds without the output voltage Voutfalling to too low a value to properly recover when the load206is recoupled.

If the wake-up element208detects that the load206is not coupled with the power converter204and the output voltage Voutis below the threshold voltage or outside the desired range, the wake-up element208transmits a command signal to the energy saving element216that causes the energy saving element216to reconnect or otherwise ensure the input voltage Vin, the transformer T1and the capacitor C1are coupled with the controller214such that the controller begins214to operate for a period of time. Specifically, the command signal of the wake-up element208controls the energy saving element216such that the controller214only outputs a desired number of cycles of the switch command signal to the transistor212before the input voltage Vin, the transformer T1and the capacitor C1are again decoupled from the controller214. In some embodiments, the desired number of cycles is a predetermined number such as three cycles. Alternatively, the desired number of cycles is able to be determined dynamically by the wake-up element208by monitoring the output voltage Voutas the controller214operates and stopping the operation of the controller214when the output voltage Voutis at a desired level or within a desired range. Alternatively, the wake-up element208is able to be directly coupled to the controller214and the wake-up element208is able to transmit the command signal directly to the controller214to cause the controller214to operate for the desired number of cycles while the input voltage Vin, the transformer T1and the capacitor C1remain disconnected by the energy saving element216. In any case, this operation is able to continue in order to maintain the output voltage Voutat the desired level until the load206is recoupled to the coupling point210. As a result, the system200is able to provide the advantage of only drawing minimal amount of power from the power source202necessary to recharge the output voltage Voutto the desired level. In particular, the cumulative period of the number of cycles required to recharge the output voltage Vouton the output capacitor Coutis able to be only tens of microseconds. Thus, when compared to the decay time of the output voltage Vout, for every tens of microseconds of operation the power converter204is able to be off for hundreds of milliseconds. Consequently, the system200provides the advantage of consuming quasi-zero power from the power source202when operating in no-load conditions.

FIG. 3illustrates a flow chart of a method of powering a load with a power supply when coupled to the load and for drawing a quasi-zero amount of power from the power supply when not coupled to the load according to some embodiments. At the step302, the wake-up element208detects if the load206is coupled with the power converter204. At the step304, the wake-up element208detects the output voltage Voutof the power converter204. At the step306, the wake-up element208transmits a recharge signal to the power converter204if the load206is not coupled with the power converter204and the output voltage Voutis below a threshold voltage. At the step308, the power converter204recharges the output voltage Voutto a predefined sleep voltage upon receiving the recharge signal. In some embodiments, the power converter204recharges the output voltage Voutby operating until the wake-up element208detects that the output voltage Voutequals the predefined sleep voltage. In some embodiments, the power converter204recharges the output voltage Voutby operating for a predetermined number of the switch command signal cycles. For example, in some embodiments, the power converter204operates for three cycles of 5 microseconds each in order to recharge the output voltage Voutfrom 4.75 volts to 5 volts. In some embodiments, the predefined sleep voltage equals the maximum operating voltage of the load206and the threshold voltage equals the minimum operating voltage of the load206. In some embodiments, the number of switching cycles that the converter204operates for is adjusted in order to maximize the ratio of the time that the output voltage Vouttakes to drop to the threshold voltage versus the combined period of the predetermined number of switching cycles. As a result, the method provides the benefit of consuming quasi-zero power from the power supply202when the power converter204is not coupled with the load206.

The method, apparatus and system of power converter quasi-zero power consumption in a no load state described herein has many advantages. Specifically, the system prevents the power converter from drawing unnecessary power from the power source when the load is not coupled to the converter and the output voltage does not require recharging, thereby reducing power consumption. Similarly, the system ensures that the minimum amount of power is drawn from the power source in order to recharge the output voltage when the load is not coupled to the converter and the output voltage falls below a minimum voltage threshold value. Accordingly, the power converter with quasi-zero no load power consumption described herein has numerous advantages.

The power converter system has been described in terms of specific embodiments incorporating details to facilitate the understanding of the principles of construction and operation of the power converter system. The specific configurations shown and the methodologies described in relation to the various modules and the interconnections therebetween are for exemplary purposes only. Such reference herein to specific embodiments and details thereof is not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modifications may be made in the embodiments chosen for illustration without departing from the spirit and scope of the power converter system.