Abstract:
A removably connected power supply for supplying external power to an electronic product. An output unit supplies power to the electronic product. A switching unit selects whether to supply the power to the output unit, and a switching apparatus turns on the switching unit in response to being connected with the electronic product and turns off the switching unit in response to being disconnected from the electronic product. The switching apparatus includes a switch which performs a switching operation in response to the connection or disconnection with the electronic product from the output unit. A switching element controls operation of the switching unit in response to the operation of the switch. Thus, the power supply is operated in a power saving mode and unnecessary power consumption and damage caused by voltage or current spikes are prevented.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the benefit of Korean Application No. 2002-3174 filed Jan. 19, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a power supply, and more particularly, to a power supply having a function of a power saving mode.  
           [0004]    2. Description of the Prior Art  
           [0005]    As shown in FIG. 1, a conventional SMPS (switching modulation power supply) has an input unit  1 , a rectification unit  2 , a switching unit  3 , a feedback unit  4 , and an output unit  5 .  
           [0006]    External AC power is supplied through the input unit  1 , and the input AC power is converted into DC power by a bridge diode in the rectification unit  2 . The rectified power is supplied to the output unit  5 , through a transformer in response to an operation of the switching unit  3 .  
           [0007]    The feedback unit  4  detects a ripple in a reference voltage (+5V) output by the transformer, and feedbacks the increase and the decrease of ripple to a feedback terminal FB of a PWM-IC  31  through photo couplers PC 1 - 1  and PC 1 - 2  and an associated photo transistor.  
           [0008]    The PWM-IC  31  maintains an output voltage as a constant voltage by controlling the power output to the output unit  5  through PWM (pulse width modulation) based on the feedback signal from the output unit  5 .  
           [0009]    As shown in FIG. 2, the output unit  5  has a power supply terminal  51  for supplying input power input to an electronic product, and a general ground terminal  52 . Where the output unit  5  is connected to the electronic product, the electronic product is operated by using a predetermined power output from the power supply terminal  51  of the output unit  5  as an operational power.  
           [0010]    Where the power supply is used, the power supply is connected and disconnected to and from the electronic product in a state where external power is being supplied to the power supply.  
           [0011]    For example, where the power supply is disconnected from the electronic product, there is a problem of damage to internal elements of the power supply and consuming unnecessary power due to unnecessary operation of the power supply because the external power is constantly being supplied to the power supply.  
           [0012]    Moreover, there is another problem of damage of the electronic product and the power supply due to a peak electric current and voltage such as the spike voltage T shown in region R of FIG. 3. Where the power supply is connected to the electronic product while the power supply is being supplied with the external power, the peak electric current and voltage are generated. That is, the spike is generated by an inrush current to the electronic product. The inrush current occurs due to suddenly connecting the electronic product to the power supply while the output of the power supply is available.  
           [0013]    Therefore, the conventional power supply has a problem of damage and consumption of unnecessary power in a long-term aspect.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention has been made to overcome the above-mentioned problem of the related art. Accordingly, it is an object of the present invention to provide a power supply which prevents the generation of a peak (spike) electrical current on connection to an electronic product and which has a function of saving electric power.  
           [0015]    Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention.  
           [0016]    The above and other objects of the present invention are accomplished by providing a removably connectable power supply for supplying external power to an electronic product, comprising: an output unit which supplies input power to the electronic product; a switching unit which selects whether to supply the power to the output unit; and a switching apparatus which turns on the switching unit where the output unit is connected with the electronic product and turns off the switching unit where the output unit is disconnected from the electronic product.  
           [0017]    The switching apparatus comprises a switch which performs a switching operation in response to a state of connection or disconnection with the electronic product and the output unit, and a switching element which controls an operation of the switching unit in response to the operation of the switch.  
           [0018]    The switch may be disposed at a power supply terminal of the output unit in order to be grounded with a ground terminal of the output unit. In this state, the switching element is turned on and the operation of the switching unit is interrupted, thus the power supply to the output unit is interrupted as well. In other words, the electric power is in a power-saving mode.  
           [0019]    The switch becomes an open state with the ground terminal where the output unit is connected in the electronic product. In this state, the switching element is turned off and the switching unit is operated, thus the power is supplied to the output unit.  
           [0020]    Therefore, where the electric power supply is not connected with the electric product, the electric power supply is in the power saving mode, thus unnecessary consumption of the power can be prevented. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The above-mentioned objects and features of the present invention will become more apparent by describing the preferred embodiment of the present invention by referring to the appended drawings, in which:  
         [0022]    [0022]FIG. 1 is a detailed diagram of a conventional SMPS power supply;  
         [0023]    [0023]FIG. 2 is a view showing an appearance of an output unit of FIG. 1;  
         [0024]    [0024]FIG. 3 is an output wave form of an output of the power supply of FIG. 1 appearing in an oscilloscope;  
         [0025]    [0025]FIG. 4 is a detailed diagram of a power supply of the present invention;  
         [0026]    [0026]FIG. 5 is an enlarged view of portions of the power supply illustrated in FIG. 4;  
         [0027]    [0027]FIG. 6A is a view illustrating an appearances of the output unit of FIG. 4 in a state where the output unit is disconnected from an electronic product;  
         [0028]    [0028]FIG. 6B is a view illustrating an appearance of the output unit of FIG. 4 in a state where the output unit is connected to the electronic product;  
         [0029]    [0029]FIG. 7 is a view correlating a portion of the connection diagram shown in FIG. 5 and the appearance of the output unit of FIG. 4; and  
         [0030]    [0030]FIG. 8 is an output wave form of an output of the power supply of FIG. 4 appearing in an oscilloscope. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]    Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.  
         [0032]    As shown in FIG. 4, the power supply of the present invention comprises an input unit  10 , a rectification unit  20 , a PWM switching unit  30 , a feedback unit  40 , and an output unit  50 .  
         [0033]    Where the input unit  10  is connected with an external AC power source, AC power is input to the power supply. The rectification unit  20  rectifies the input external AC power, and converts the AC power into DC power.  
         [0034]    The PWM switching unit  30  is disposed at a first part of a transformer. A first DC power is coupled to a second part through the transformer by the operation of the PWM switching unit  30 , and is rectified to a second DC power through a predetermined diode and a capacitor. After that, the second DC power is supplied to the output unit  50 .  
         [0035]    The feedback unit  40  detects a ripple element in a reference voltage (+5V) output by the transformer, and transmits variations of the ripple to a feedback end VFB of a PW-MIC  310  through a photo coupler PC 1 - 1  and an associated photo transistor PC 1 - 2 . The PWM-IC  310  maintains a voltage output to a power supply terminal  510  of the output unit  50  through PWM (pulse width modulation).  
         [0036]    [0036]FIG. 5 is an enlarged view of portions of the power supply illustrated in FIG. 4. The output unit  50  outputs a predetermined DC power by the operation of the PWM switching unit  30  at the power supply terminals  510  and  520 . The power supply supplies a predetermined power to an electronic product (not shown) through the power supply terminal  510  and a ground terminal  520 .  
         [0037]    The output unit  50  comprises a switch  61  which performs a switching operation according to whether the output unit  50  and the electronic product (not shown) are connected, and a photo coupler  62   a  which optically communicates with a photo transistor  62   b  to control the operation of the PWM switching unit  30  in response to the switching operation of the switch  61 .  
         [0038]    As shown in FIG. 7, the switch  61  of the output unit  50  is integrally constructed with the power supply terminal  510  of the output unit  50 .  
         [0039]    Where the output unit  50  is disconnected from the electronic product, contacts  61   a  of the switch  61  contact the ground terminal  520  of the output unit  50  as shown in FIG. 6A. Where the output unit  50  is connected in the electronic product, the contacts  61   a  of the switch  61  are separated from the ground terminal  520  and thus the switch  61  is opened from the ground terminal  520 .  
         [0040]    In other words, the operation of the PWM switching unit  30  is controlled as the photo coupler  62   a  and the photo transistor  62   b  are operated in response to the states of closed and open of the switch  61 .  
         [0041]    The controlling of the switch  61  of the output unit  50  and the PWM switching unit  30  in response to the operation of the photo coupler  62   a  and the photo transistor  62   b  will be described in further detail.  
         [0042]    When the external AC power is input through the input unit  10  of the SMPS (switching modulation power supply), the AC power is rectified by the rectification unit  20 , and the rectified first DC power is provided to the first part of the transformer. In addition, the rectified first DC power is supplied as an operation power Vcc of the PWM-IC  310  of the PWM switching unit  30  through a predetermined resistance. Where the PWM-IC  310  is operated, the first DC power of the first part of the transformer is coupled to the second part of the transformer by a switching operation of a field effect transistor FET. After that, the transformer coupled power is rectified to a second DC power by a diode and filtered by a capacitor. The rectified second DC power supplies the power (+5V) to the electronic product connected with the output unit  50  through the power supply terminal  510  of the output unit  50 .  
         [0043]    The feedback unit  40  detects the ripple element in the reference voltage (+5V) output by the transformer and diode, and transmits the variations of the ripple to the feedback end VFB of the PWM-IC  310  through the photo coupler PC 1 - 1  and the photo transistor PC 1 - 2 . The PWM-IC  310  maintains the voltage output to the power supply terminal  510  of the output unit  50  through the PWM (pulse width modulation).  
         [0044]    The operation of the PWM switching unit  30  is controlled according to the operation of the switch  61 , the photo coupler  62   a  and the photo transistor  62   b.    
         [0045]    As shown in FIG. 6A, when the power supply is disconnected from the electronic product, the switch  61  of the output unit  50  of the power supply is grounded with the ground terminal  520 . Under this condition, the photo coupler  62   a  emits light and the photo transistor  62   b  is operated. The photo transistor has a collector which is connected with a CS terminal of the PWM-IC  310  of the PWM switching unit  30  and an emitter which is connected to ground. Where the photo coupler  62   a  emits light, the photo transistor  62   b  conducts, thus the CS terminal of the PWM-IC  310  is grounded, and the operation of the PWM-IC  310  is stopped. The operation of the PWM-IC 310  is stopped such that the rectification unit  20  and the second part are electrically disconnected from each other. However, the magnetic energy is only transmitted between the rectification unit  20  and the second part by the transformer. Thus, the operation of the photo coupler  62   a  is possible although the operation of the PWM-IC 310  is stopped.  
         [0046]    Accordingly, the photo couplers  62   a  and  62   b  are operated such that the CS terminal of the PWM-IC 310  is grounded. Therefore, the power supply is in a power saving mode and unnecessary power consumption is prevented.  
         [0047]    For example, a result of an experiment where the external power is supplied in a state that the power supply is disconnected from the electronic product is as follows. The power consumption of the conventional power supply is 2.75W, and the power consumption of the power supply according to the present invention is 0.78W. It will be recognized that this is a remarkable effect of power saving. Thus, where the power supply and the electronic product are disconnected from each other, there is hardly any power consumption in the power supply.  
         [0048]    Where the power supply is connected in the electronic product, the switch  61  of the output unit  50  is opened from the ground terminal  520  by a connection unit (not shown) of the electronic product. Where the switch is opened, the photo coupler  62   a  ceases to emit light and the photo transistor  62   b  stops conducting, releasing the PWM-IC  310  terminal CS from ground potential so that the PWM-IC  310  begins a switching operation. In other words, the potential of the CS terminal of the PWM-IC  310  of the PWM switching unit  30  becomes a normal operation state.  
         [0049]    When the operation of the PWM switching unit  30  becomes the normal state, the input external power is supplied to the power supply terminal  510  of the output unit  50  like the operation of the SMPS described before, and the power (+5V) is supplied to the electronic product connected with the output unit  50 .  
         [0050]    In the embodiment described above, the operation of the PWM-IC  310  is stopped as the CS terminal of the PWM-IC  310  is grounded. It will be appreciated that where a PWM-IC element has another characteristic different from the PWM-IC  310 , the operation of the PWM-IC may be controllable by controlling a different predetermined terminal of the alternate PWM-IC.  
         [0051]    Accordingly, where the power supply is connected to the electronic product, the power input through the input unit  10  is supplied to the electronic product as a predetermined power. Where the power supply is disconnected from the electronic product, the power supply is operated in a power saving mode which stops operation of portions of the power supply which are not necessary to maintain the power supply in a standby or power saving mode.  
         [0052]    Where the power supply is generally connected to the electronic product, the power supply and the electronic product are protected from the suddenly generated peak electric current and voltage.  
         [0053]    Where the power supply is disconnected in the electronic product, the power supply is operated in the power saving mode. Thus, the output voltage of the power supply is zero. Therefore, as shown in FIG. 8, even where the power supply is connected in the electronic product, the peak electric current and voltage caused by the sudden application of the voltage and sudden flow of current is not generated.  
         [0054]    As described above, even where the external power is supplied in the state that the power supply is operated in the power saving mode, unnecessary power consumption is prevented.  
         [0055]    Additionally, as the peak electric current and voltage generated by the sudden current and voltage is eliminated, the damage of the electronic product and the power supply is prevented.  
         [0056]    According to the present invention, since the operation of the power supply is controlled in response to whether the power supply is connected in the electronic product, where the power supply is not used, the power supply is operated in the power saving mode. Thus, unnecessary power consumption is prevented, and the damage caused by the peak electric current and voltage is also prevented.  
         [0057]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.