Patent Application
20140013135
The invention relates to a system having a lower power operation mode and a normal operation mode and to a method of controlling a power supply.
The invention can be used in peripheral devices, such as a printer, or in any other electronic system having a lower power mode of operation and a normal power mode of operation, such as a Stand-by mode and a Ready mode.
There are electronic systems, e.g. peripheral devices, which can switch between a low power mode of operation and a normal power mode of operation. The normal operation mode sometimes is called Ready mode where the device performs or is ready to perform its intended functions. The low power mode is sometimes called stand-by mode which is a power saving mode in which the load on the power supply is minimized. Such systems are designed to comply within energy saving regulations which might specify a maximum power consumption at the low power mode of operation, e.g. stand-by mode. Any circuit which is not necessary in the stand-by mode shall be powered-down but will again be supplied with power in the normal operation mode.
These type of power supplies, in which supply and power-down of circuits is controlled for minimizing power consumption in the stand-by mode, can be useful, for example, in printers, such as large format printers, office printers, etc. having an integrated power supply unit for powering internal electronics.
Examples of invention described herein provide a system having a low-power operation mode and a normal operation mode wherein the system is supplied from a power supply unit with at least a first voltage and a second voltage. The system comprises one or more first circuits which operate during the normal operation mode but do not operate during the low-power operation mode. Such circuits can, for example, be part of the printer electronics for controlling the operation of a printer, communication with a host device, and the like. When it is described that a circuit does not operate during the low-power operation mode, this also includes the case that a circuit goes to its lowest power consumption state so that the circuit can be powered-up at any time in a controller manner, as when a “wake-up” event occurs. The system further comprises at least one second circuit which operates during the low-power operation mode. The second circuit, for example, can be a stand-by circuit which operates during a stand-by mode to maintain minimum functions of a system, such as a peripheral device or printer, for example. One of these minimum functions could be a system wake-up function, for example. The first and second voltages provided by the power supply unit could be a normal operating voltage and a stand-by voltage, for example.
The system further comprises a switching unit for selectively supplying the first circuit with the first voltage or the second voltage from the power supply unit wherein the switching unit is controlled based on a power status signal supplied by the power supply unit. According to the status of the power supply unit, it hence is possible to selectively apply the first and second voltages to the first and second circuits or disconnect at least some of the circuits so as to minimize the power consumption, in particular during start-up of the power-supply, and still optimize and safeguard the operation of the system at all times from power-up to power-down.
In one example, the system is implemented in a peripheral device, such as a printer, wherein the second circuit comprises a stand-by circuit of device electronics; and the first circuit comprises another circuit of the device electronics. In the following description, instead of referring to first and second circuits, reference may be made to stand-by circuits and other circuits, wherein it should be understood that the invention is not limited to this example, nor to peripheral devices or printers. On the same token, instead of referring to first and second voltages, reference may be made to a stand-by voltage and a normal operating voltage, wherein it should be understood that the invention is not limited to these specific types of voltages.
In one example, the system is controlled in such a way that these stand-by circuits are always supplied with the stand-by voltage, whether the printer is in a normal operation mode, such as ready, or a low-power operation mode, such as stand-by, or transits between modes, e.g. from off to ready, from ready to stand-by, from stand-by to ready, from ready to off, or from stand-by to off. The other circuit of the device electronics can be disconnected during start-up of the system, can be supplied with the normal operating voltage during the normal operation mode, and can be supplied with the stand-by voltage during a transition from the normal operation mode to the stand-by mode. Connection and disconnection of the other circuits to and from power rails of the power supply unit can be controlled by the switching unit based on a power status signal provided by the power supply unit. The system allows to power only those circuits which are necessary at any particular operation mode, including transitions between modes, such as start-up and a transition from the normal operation mode to the low-power operation mode. The load on the power supply unit hence is reduced while, at all times, safeguarding proper operation of the overall system, including an orderly shut-down and transition to stand-by mode where it might be necessary to store information, reset states of logic and the like.
The power supply unit 10 transforms the mains alternating current (AC) into a direct current (DC) to be used by the internal electronics 20 of the printer system or other device. In the example described, the direct current can be supplied at different rails or outputs 12, 14, which can have different or the same voltage levels. In order to limit the maximum power consumption of the system at any time, supply voltages from the two outputs or rails 12, 14 are supplied to the different circuits 22, 24 of the printer electronics 20 only as needed. Any circuits which are not necessary during particular operation modes, such as a stand-by mode, shall be powered-down and shall be supplied with the operating power from the first output only during the normal operation mode. However, when the printer systems needs to go from a normal operation mode to a low-power mode, circuits 22 necessary for controlling operation of the printer system often should not simply be disconnected from the power supply unit 10 as they might need some additional power to perform an orderly shut-down, e.g. for storing current status information, setting required states of logic or the like. On the other hand, if all of the circuits 22, 24 of the printer electronics were powered from the power supply unit 10 also during start-up of the printer system, malfunctioning of the system could occur because the power supply unit is not yet ready to provide the necessary power level. The present disclosure hence provides an easy and cheap circuit to switch DC voltage rails 12, 14 of the power supply unit 10 to the necessary circuits 22, 24 as needed, avoiding unnecessary power supply from the power supply unit 10 during cold start-up of the printer system but safeguarding necessary power supply during shut-down and transition to stand-by.
In the example described with reference to
For switching the power supply, switching unit 26 is controlled based on the power status signal PWR_OK supplied from the power supply unit 10. The PWR_OK signal can indicate that the power supply unit 10 has fully been powered-up by a transition from a LOW to a HIGH signal state or vice versa, for example. One example of controlling the switching unit 26 is as follows: When the power supply unit is in a start-up mode, the other circuits 22 are disconnected from the power supply unit 10 by the switching unit 10. Once the power supply unit is fully powered-up, as indicated by the power status signal PWR_OK, the printer system can go into a normal operation mode and the other circuits 22 can be connected to the first output 12 of the power supply unit 10, providing the normal operating power 5V. When the printer system transits from the normal operation mode to the low-power operation mode, the other circuits 22 are powered-down in a controlled manner and, for this purpose, are connected to the second output 14, providing the second voltage, such as 5 VSB. This can be accomplished by printer firmware, for example, preparing the printer electronics to transit to the stand-by mode. The stand-by circuit 24 stays connected to the second output 14 of the power supply unit 10 providing the second voltage 5 VSB, during all operation modes, including the normal operation mode, the low-power operation mode and the transition from the normal operation mode to the low-power operation mode.
In order to avoid that the power supply unit 10 needs to supply more power than available at any time, the printer system hence detects a start-up condition, using the power status signal PWR_OK, and avoids feeding the other circuits 22 from either one of the power rails 12, 14 during start-up of the system. When the start-up sequence has been completed, the switching unit 26 can connect the other circuits 22 to the normal operating power 5V at the first output rail 12.
The printer electronics 20 detects a start-up condition, such as cold start-up, based on the power status signal PWR_OK output from the power supply unit 10 at output 16. This signal is included in most power supply units according to the ATX standard and is actively HIGH (1). Of course, the invention is not limited to the use of this particular signal. If the power status signal PWR_OK is in a LOW state, such as 0V, this signals that the low-power voltage, such as 5 VSB, is the only output voltage present at the outputs 12, 14 of the power supply unit 10. After start-up has been completed, the remaining voltage rails, such as normal operating voltage 5V at the first output 12, are ready to use, and the power status signal PWR_OK goes to HIGH state, such as 5V or one (1). If any voltages other than the low-power voltage 5 VSB are switched off, the power status signal PWR_OK goes to the LOW state (0) again.
Accordingly, in the example shown in
In the example shown, the D input 36 of the flip-flop 28 is always connected to the low-power operating voltage, 5 VSB, corresponding to a high voltage level. As soon as a rising edge of the power status signal PWR_OK is present at the CLK input 38, this high level is stored in the flip-flop 28 and transmitted to the Q output 40. This happens when the start-up of the power supply unit 10 is completed and when all rails 12, 14 of the power supply unit 10 are fully available to provide output power, as signaled by the rising edge of the power status signal PWR_OK.
When the Q output 40 of flip-flop 28 goes to a HIGH level (1), the second switch S2 32 is closed, i.e. connected to first pole d, while the first switch S1 30 remains in its default position, at the first pole a. Accordingly, the other circuits 22, i.e. circuits necessary for the normal operation of the printer system, are powered from the normal operating power rail 12 of the power supply unit 10.
When the printer system needs to switch to the low-power mode, printer firmware (not shown) prepares the printer system and drives the first switch S1, 30, to the second pole b so as to connect the other circuits 22 to the second output 14 of the power supply unit 10. At this time, the first or other circuits 22 are powered from the low-power voltage, 5 VSB, so that they are able to orderly go to the low-power mode. The first switch S1, 30, will remain in the second position b so that the other circuits 22 are always powered from 5 VSB during the low-power mode. When the firmware is sending the command to go to low-power mode, all these circuits 22 are going to the lowest power consumption state. This way they are consuming as little as possible from the 5 VSB power supply. But they will be powered all the time, as when a “wake-up” event appears, they have to be able to wake-up in a controller manner. Once the power supply unit 10 has been powered-down, the power status signal PWR_OK goes LOW but the Q output 40 of the flip-flop 28 remains in HIGH state (1) as no rising edge was present sent at CLK input, and no 0 was present at D input. Therefore, second switch S2 remains closed (d position) all the time, Accordingly, during all the low power mode state, the Q output 40 of flip-flop 28 is always HIGH (1) and the switch S2 is always closed, i.e. in d position.
During all times, the second circuit 24 remains connected to the second output 14 of the power supply unit 10. The second voltage or low operating voltage 5 VSB is always present during the normal operation mode, stand-by mode and shut-down, unless the power supply unit 10 is completely switched off turning a respective mechanical switch to the OFF or zero (0) position or unplugging the power cord from the inlet connected to mains. At this time, also the low operating power is off (0V) and the switch S2 shall be open. When the power supply unit 10 is switched on (at cold start-up), there will be a zero (0) at the Q output and the switch S2 hence will be open; only after there is at least low power (5 VSB) at the D input, the switch S2 will close (d position) at the first rising edge at the CLK input.
This disclosure presents a new simple and low-cost circuit to switch the voltage rails of the power supply unit to device circuits only when needed, in particular, avoiding supply power to circuits during the start-up process and hence avoiding malfunctioning of the whole system. On the other hand, when the system goes to a low power mode or is turned off, additional circuits can be provided with power from the stand-by voltage rail to ensure an orderly shut-down. The circuit disclosed detects the status of the power supply unit and controls the power supply to these additional circuits accordingly.
