Power supply apparatus with low power in standby mode

Provided is a power supply apparatus with low power in a standby mode. The apparatus includes a voltage multiplier configured to multiply an input voltage and including a first terminal through which the multiplied voltage is output and a second terminal through which a voltage lower than a voltage of the first terminal is output; a main switch-mode power supply (SMPS) configured to receive the voltage of the first terminal of the voltage multiplier; and a standby SMPS configured to receive a voltage of the second terminal of the voltage multiplier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(a) from Korean Patent Application No. 10-2008-0083521, filed on Aug. 26, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present general inventive concept relates to a power supply apparatus, and more particularly, to a power supply apparatus with low power in a standby mode.

2. Description of the Related Art

In order to reduce the sizes and heat generation of power supply apparatuses and economize on energy of systems, it is absolutely necessary for the power supply apparatuses to convert power at high efficiency. In particular, zero-voltage switching (ZVS) or zero-current switching (ZCS) is enabled using resonant converters with various shapes to minimize heat generation and power consumption of switch devices, so that power supply apparatuses can operate very efficiently at a rated load or higher.

In most resonant converters, as a primary-side circulating current increases, it causes more conduction loss, thereby degrading the efficiency of the resonant converters. Accordingly, it is more desirable to boost an input voltage. Therefore, in order to use a resonant converter in a place with a low input voltage of about 110V, it is necessary to boost the input voltage using a voltage controller, such as a boost-type active power factor correction (PFC) or a voltage multiplier. However, the boosting of the input voltage may result in the reduction of power efficiency in a standby mode. This is because power loss in the standby mode is mainly caused by switching loss, which is proportional to the square of the input voltage.

Therefore, developing a new technique for minimizing power consumption even in the standby mode is needed.

SUMMARY OF THE INVENTION

The present general inventive concept provides a power supply apparatus capable of minimizing power consumption in a standby mode.

The present general inventive concept also provides an image forming apparatus including the power supply apparatus.

Embodiments of the present general inventive concept can be achieved by providing a power supply apparatus including a voltage multiplier configured to multiply an input voltage and including a first terminal through which the multiplied voltage is output and a second terminal through which a voltage lower than the multiplied voltage is output, a main switch-mode power supply (SMPS) configured to receive the voltage of the first terminal of the voltage multiplier, and a standby SMPS configured to receive a voltage of the second terminal of the voltage multiplier.

The voltage multiplier may include a rectifier circuit configured to rectify the input voltage, and a smoothing circuit configured to smooth the rectified voltage and connected in parallel to the rectifier circuit, the smoothing circuit including a first capacitor and a second capacitor connected in series.

The main SMPS may receive voltages from the ends of the serially connected first and second capacitors of the smoothing circuit as input voltages, and the standby SPMS may receive voltage from the ends of the second capacitor of the smoothing circuit as input voltages.

Embodiments of the present general inventive concept can also be achieved by providing an image forming apparatus including a power supply apparatus with low power in a standby mode, and an image formation unit configured to receive power from the power supply apparatus and form images, wherein the power supply apparatus includes a voltage multiplier configured to multiply an input voltage and including a first terminal through which the multiplied voltage is output and a second terminal through which a voltage lower than the multiplied voltage is output, a main SMPS configured to receive the voltage of the first terminal of the voltage multiplier as an input voltage, and a standby SMPS configured to receive a voltage of the second terminal of the voltage multiplier as an input voltage.

Embodiments of the present general inventive concept can also be achieved by providing a power supply apparatus including a rectifier configured to rectify input power, a voltage multiplier configured to multiply the input power, a switch unit configured to switch to the rectifier or the voltage multiplier in response to a predetermined control signal, a main SMPS connected to the rectifier or the voltage multiplier based on the switching of the switch unit, and a standby SMPS connected to the rectifier or the voltage multiplier based on the switching of the switch unit.

The rectifier may rectify the input power and may output power controlled by the switching of the switching unit, and the voltage multiplier may be connected in parallel to the rectifier, multiply the input power, and output the output power controlled by the switching of the switch unit, the voltage multiplier may include a first capacitor and a second capacitor.

The switch unit may switch to the rectifier or the voltage multiplier depending on an external operating mode.

The switch unit may switch to the rectifier or the voltage multiplier depending on output powers of the main SMPS and the standby SMPS.

The foregoing and/or other aspects and utilities of the present general inventive concept can also be achieved by providing an image forming apparatus including the power supply apparatus with low power in the standby mode and an image forming unit.

Embodiments of the present general inventive concept can also be achieved by providing a power supply apparatus may include a first SMPS configured to receive a first voltage of a power source to generate a first power to an electronic device in a first mode of the electronic device, and a second SMPS configured to receive a second voltage of the power source to generate a second power to the electronic device in a second mode of the electronic device.

The second power may be lower than the first power.

The power source may include a voltage multiplier to receive an input voltage, the voltage multiplier having a first terminal to output the first voltage and a second terminal to output the second voltage.

The power supply apparatus may further included a switch unit configured to switch the power source to output the first voltage or the second voltage according to a predetermined control signal.

The power source may include a rectifier to output the first voltage based on the predetermined control signal, and a voltage multiplier to output the second voltage based on the predetermined control signal.

The first mode may correspond to a powered on status of the electronic device, and the second mode may correspond to a standby status of the electronic device

Embodiments of the present general inventive concept can also be achieved by providing an image forming apparatus including an image formation unit configured to receive power from a power supply apparatus with low power in a standby mode, the power supply apparatus may include a first SMPS configured to receive a first voltage of a power source to generate a first power to the image formation unit in a first mode of the image formation unit, and a second SMPS configured to receive a second voltage of the power source to generate a second power to the image formation unit in a second mode of the image formation unit.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1is a block diagram of a power supply apparatus with a double converter structure to which an input voltage multiplication method is applied.

Referring toFIG. 1, an input unit of the power supply apparatus includes a voltage multiplier100. The voltage multiplier100of the input unit may be used to boost the input voltage. In this case, when the power supply apparatus is used in a place with a low alternating-current (AC) input voltage of about 110 Vac (85˜135 Vac), the input voltage of the power supply apparatus may be doubled. That is, assuming that a root mean square (RMS) input voltage is Vin, a direct-current (DC) bulk voltage Vbrectified by the voltage multiplier100is expressed as in Equation 1:
Vb=2√{square root over (2)}Vin(1).

When the input voltage of the power supply apparatus is boosted, a resonant topology, which is widely used for high-efficiency power conversion in a power supply apparatus, may be effectively employed. That is, when the input voltage of the power supply apparatus is boosted, a primary-side circulating current of the resonant topology may be lessened, thereby minimizing power loss during power conversion caused by resonance. Since the resonant topology is mainly highly efficient in a high-capacity device, it may be applied to high-capacity converters. Accordingly, in the power supply apparatus shown inFIG. 1, the resonant topology may be efficiently applied to a main switch-mode power supply (SMPS)120.

However, it is inefficient to apply the resonant topology to a low-capacity converter, such as a standby SMPS140ofFIG. 1, which needs to operate at high efficiency under low-power conditions, such as a standby mode. Since conduction loss caused by a circulating current of the resonance topology continuously occurs even at a low output load, a large amount of power loss is caused as contrasted with output under the low-power conditions, so that power efficiency decreases in the standby mode. Also, since the resonant topology is complex to configure and requires high cost of materials, it is applied not to a low-capacity converter, such as a standby SMPS, but to a flyback converter with the simplest structure. The flyback converter may efficiently operate under low-power conditions because no circulating current is generated unlike in the resonant topology.

However, as illustrated inFIG. 1, when input power is doubled by a voltage multiplication method and rectified, standby-mode efficiency of the flyback converter may be reduced. This is due to the fact that loss of the flyback converter in a low-power state, such as a standby mode, is chiefly caused by switching, and switching loss of a metal-oxide-semiconductor field effect transistor (MOSFET) serving as a main switch is proportional to the square of a voltage applied to both ends of the switch as shown in Equation 2:

wherein Psw,lossdenotes MOSFET switching loss, Cossdenotes MOSFET output capacitance, VDSdenotes drain-to-source voltage, “n” denotes a turn ratio of a transformer, and Vodenotes an output voltage. In Equation 2, when a DC bulk voltage Vbis doubled by the voltage multiplier100, switching loss is also approximately doubled. Accordingly, when an input voltage is boosted using the voltage multiplier100in order to increase the efficiency of the high-capacity main SMPS120, the standby-mode efficiency of the standby SMPS140is reduced.

FIG. 2is a block diagram of a power supply apparatus with low power in a standby mode according to an exemplary embodiment of the present general inventive concept. The power supply apparatus illustrated inFIG. 2adopts a voltage multiplier using an input rectification method in order to improve standby power efficiency.

The power supply apparatus illustrated inFIG. 2may include a voltage multiplier200, a main SMPS220, and a standby SMPS240.

The voltage multiplier200may multiply an input voltage and may include a first terminal215through which the multiplied voltage is output and a second terminal235through which a voltage lower than the voltage of the first terminal215is output. The voltage multiplier200may include a rectifier circuit202and a smoothing circuit204. The rectifier circuit202may rectify the input voltage. The smoothing circuit204may smooth the voltage rectified by the rectifier circuit202and be connected in parallel to the rectifier circuit202. The smoothing circuit204may be embodied by two capacitors connected in series.

The main SMPS220may receive the voltage of the first terminal215of the voltage multiplier200as an input voltage, while the standby SMPS240may receive the voltage of the second terminal235of the voltage multiplier200as an input voltage.

An image forming apparatus according to the present general inventive concept may include the above-described power supply apparatus shown inFIG. 2and an image forming unit250shown inFIG. 2. The image forming apparatus600, as shown inFIG. 6may also include additional elements, such as a feeding unit610and a discharge unit620. The image forming unit250may include a cartridge to eject ink onto a printing medium. The power supply apparatus as shown inFIG. 2may supply power to the image forming apparatus600. Upon receiving a power supply, the printing medium is fed from the feeding unit610to the image forming unit250along path P of the printing medium. An image is formed on the printing medium by the image forming unit250, and the printing medium is discharged by the discharge unit620.

FIG. 3illustrates an example of the power supply apparatus ofFIG. 2. InFIG. 3, the voltage multiplier200ofFIG. 2corresponds to a voltage multiplier300, the rectifier circuit202ofFIG. 2corresponds to a rectifier circuit302, and the smoothing circuit204ofFIG. 2corresponds to a smoothing circuit304. Also, the main SMPS220and the standby SMPS240ofFIG. 2correspond to a main SMPS320and a standby SMPS340, respectively.

The smoothing circuit304may include two capacitors Cb1and Cb2connected in series. The main SMPS320may receive voltages from the ends of the first and second capacitors Cb1and Cb2connected in series as input voltages, while the standby SMPS340may receive voltages from the ends of the second capacitor Cb2of the smoothing circuit304as input voltages.

A power supply apparatus according to the present exemplary embodiment will now be described in more detail. In order to reduce standby-mode power, the main SMPS220(or320) may be turned off, and the power conversion loss of the standby SMPS240(or340) may be reduced using a technique for reducing switching loss, for example, a burst mode or a skip cycle. When the standby SMPS240(or340) is connected to the second capacitor Cb2of the voltage multiplier200(or300), a DC bulk voltage Vbapplied to the standby SMPS240(or 340) may be half a voltage applied to the main SMPS220(or320). Accordingly, switching loss caused to the standby SMPS240(or340) may be calculated as shown in Equation 3:

As can be seen from Equation 3, the standby SMPS240(or340) may reduce a voltage applied to a switch by 33% and also, reduce switching loss by 50%, as compared with when a multiplied output voltage is used. Also, since a voltage applied to a switch of the standby SMPS240(or340) is reduced by half, voltage stress applied to the standby SMPS240(or340) may be lessened and a more inexpensive switch may be used. However, according to the above-described method, since the upper capacitor Cb1has a different load from the lower capacitor Cb2, that is, since the lower capacitor Cb2has a higher load than the upper capacitor Cb1based on the load of the standby SMPS240(or340), there may be a voltage disparity between the capacitors Cb1and Cb2(not shown inFIG. 3). Additionally, a ripple voltage may increase in the capacitor Cb2connected to the standby SMPS240(or340) so that the average voltage applied to both ends of the capacitor Cb2may be reduced by half the ripple voltage. In other words, a ripple voltage that has been smoothed results in a voltage of half the ripple voltage, therefore when the ripple voltage increases, this ratio is preserved, and the average voltage applied to both ends of the capacitor Cb2is reduced by half.

When there is a voltage disparity between the output capacitors Cb1and Cb2of the voltage multiplier200(or300) as described above, the lifespans of the capacitors Cb1and Cb2may be shortened. Accordingly, the above-described method may be employed when a voltage difference between the capacitors Cb1and Cb2is within an allowable limit. For example, when the capacity of the standby SMPS240(or340) is 20% or lower of that of the main SMPS220(or320), the above-described method may be used.

FIG. 4is a block diagram of a power supply apparatus with low power in a standby mode according to another exemplary embodiment of the present general inventive concept. The power supply apparatus shown inFIG. 4adopts a voltage multiplier using an input rectification method in order to improve standby power efficiency.

The power supply apparatus shown inFIG. 4may include a rectifier410, a voltage multiplier420, a switch unit430, a main SMPS440, and a standby SMPS450.

The rectifier410may rectify input power and then output power controlled by the switching of the switch unit430.

The voltage multiplier420, which is connected in parallel to the rectifier410, may multiply the input power and output power controlled by the switching of the switch unit430. The voltage multiplier420may include two capacitors connected in series.

The switch unit430may switch to the rectifier410or the voltage multiplier420in response to a predetermined control signal, which depends on an external operating mode or output powers of the main SMPS440and the standby SMPS450.

The main SMPS440may be connected to the rectifier410or the voltage multiplier420based on the switching of the switch unit430.

The standby SMPS450may be connected to the rectifier410or the voltage multiplier420based on the switching of the switch unit430.

An image forming apparatus according to the present general inventive concept may include the above-described power supply apparatus shown inFIG. 4and an image forming unit460shown inFIG. 4.

FIG. 5illustrates an example of the power supply apparatus shown inFIG. 4. InFIG. 5, the rectifier410ofFIG. 4corresponds to a rectifier510, the voltage multiplier420ofFIG. 4corresponds to a voltage multiplier520, and the switch unit430ofFIG. 4corresponds to a switch unit530. Also, the main SMPS440and the standby SMPS450ofFIG. 4correspond to a main SMPS540and a standby SMPS550, respectively. The rectifier510may be referred to as a bridge diode. The voltage multiplier520may be referred to as a serial capacitor.

As stated above, in the power supply apparatus shown inFIG. 3, when the standby SMPS340has a high capacity, a voltage disparity is caused between the output capacitors Cb1and Cb2of the voltage multiplier300so that a ripple voltage of the DC bulk voltage Vbmay increase and more stress may be applied to the standby SMPS340. Accordingly, when the capacity of the standby SMPS340exceeds 20% of that of the main SMPS320, the structure shown inFIG. 5may be appropriately used.

When the electrically controlled switch unit430(or530) is connected between the bridge diode510and the serial capacitor520, the switch unit430(or530) may be selectively switched between a full-bridge rectification mode and a multiplied voltage rectification mode. Thus, in a steady mode in which the main SMPS440(or540) operates, the switch unit430may enter into the multiplied voltage rectification mode and double an input DC bulk voltage Vbto maximize the efficiency of the main SMPS440(or540). In contrast, in a standby mode in which the main SMPS440(or540) does not operate, the switch unit430may enter into the full-bridge rectification mode and minimize standby-mode power loss of the standby SMPS450(or550). In this case, the standby SMPS450(or550) normally operates in both the multiplied voltage rectification mode and the full-bridge rectification mode. That is, since the standby SMPS450operates within a wide range of input voltages, it may be designed based on a universal input method.

In general, a low-capacity flyback capacitor with high low-power efficiency may be used as the standby SMPS450(or550). The flyback converter may be designed to operate within a wide range of input voltages because it is based on a buck-boost method.

The rectification mode of the switch unit430(or530) may be controlled by applying an external signal according to an operating mode. For example, when an image forming apparatus using the power supply apparatus enters into a standby mode, the standby mode may be used to control the rectification mode of the switch unit430(or530).

Alternatively, the rectification mode of the switch unit430(or530) may be controlled depending on whether the main SMPS440(or540) or the standby SMPS450(or550) is operating based on the output powers thereof. The output powers of the main SMPS440(or540) and the standby SMPS450(or550) may be based, respectively, on the voltages received by the main SMPS440(or540) and the standby SMPS450(or550). An electronic device may be configured to receive the respective output powers of the main SMPS440(or540) and the SMPS450(or550). The electronic device may have a first mode that corresponds to a powered on status, and a second mode that corresponds to a standby status.

In the exemplary embodiment shown inFIG. 2, as compared with when a multiplied output voltage is used as it is, a voltage applied to a switch can be reduced by about 33%, and switching loss can be also reduced by about 50%.

As compared with a case where a multiplied output voltage is used, a voltage applied to a switch can be reduced and switching loss can be also reduced. Also, since a voltage applied to a switch of a standby SMPS is reduced by half, voltage stress applied to the standby SMPS can be lessened and an inexpensive switch may be adopted. However, the power supply apparatus shown inFIG. 2may be used only when the standby SMPS has a low capacity because a voltage disparity may occur between output capacitors connected in series in a voltage multiplier.

In the exemplary embodiment shown inFIG. 4, when a power supply apparatus is in a steady mode, a switch unit may enter into a multiplied voltage rectification mode to maximize the efficiency of a main SMPS; while when the power supply apparatus is in a standby mode, the switch unit may enter into a full-bridge rectification mode to minimize switching loss of a standby SMPS. As a result, even if the standby SMPS has a high capacity, the power of a rectifier capacitor can be uniformly used, thereby preventing occurrence of a voltage disparity.