Abstract:
A power supply and a switch apparatus are disclosed. The power supply is designed for providing a liquid crystal display with a power source. In the present invention, a bouncing switch is used for power-on and power-off functions. When the bouncing switch is activated, the power to the main system is also activated and the supply of power to the main system is maintained. A controller of the main system is then activated to acquire an authorization for controlling the power to the main system so that power is continuously supplied to the main system. Then, the main system sequentially activates the power supply of each sub-system. If the bouncing switch is activated by a second triggering, the main system may sequentially turns off the power module inside each sub-system. Finally, the power to the main system is shut down to lower the static power consumption of the whole system.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority benefit of Taiwan application serial no. 95117080, filed May 15, 2006. All disclosure of the Taiwan application is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a power supply designed for providing a liquid crystal display with a power source and including a sequential activating circuit designed with various power supply methods. 
         [0004]    2. Description of Related Art 
         [0005]    Liquid crystal display (LCD) has the advantage of a slimmer body and occupies less space than the conventional cathode ray tube (CRT). Therefore, an increasing number of liquid crystal displays are used as a large television at home or a viewing panel in public places. The power supply system of a liquid crystal display typically includes power source modules such as a 5V conversion circuit, a VGH conversion circuit, a VGL conversion circuit and a CCFL driving circuit for converting the power source into voltages required by various devices and supplying the devices. 
         [0006]      FIG. 1  is a schematic circuit diagram of a conventional power supply circuit. As shown in  FIG. 1 , when a power source PS input is provided, each of the power modules (the 5V conversion circuit  12 , the VGH conversion circuit  22 , the VGL conversion circuit  24  and the CCFL driving circuit  26 ) begins to operate by supplying power to an LCD module signal control circuit  10  and an LCD module display  20 . The LCD module signal control circuit  10  outputs signal to the LCD module display  20 . According to the received VGL, VGH, 5V voltage signals and the control signal provided by the LCD module signal control circuit  10 , the LCD module display  20  displays an image signal on a screen. However, when the LCD module signal control circuit  10  and the LCD module display  20  are in a standby mode and stop operating, each of the power modules still supply power leading to considerable waste of energy. In particular, for a system powered by a battery, if the power system is not cut off when the LCD module signal control circuit  10  and the LCD module display  20  are not in use, a small current has to be continuously provided to the system. As a result, the continuity of the battery power is weakened. 
         [0007]    Since the current liquid crystal display power supply system has no provision for stopping the supply of power in the idle state, considerable power is wasted. For a portable system operated by battery power, the battery life is lowered significantly. 
       SUMMARY OF THE INVENTION 
       [0008]    Accordingly, at least one objective of the present invention is to provide a power supply mainly designed for providing a liquid crystal display with a power source. The power supply mainly includes a sequential activating circuit and a number of different power supply methods. In the present invention, a bouncing switch is used for power-on and power-off functions. When the bouncing switch is activated, power to the main system is also activated and the supply of power to the main system is maintained. A controller of the main system is then activated to acquire an authorization for controlling the power to the main system so that power is continuously supplied to the main system. Then, the main system sequentially activates the power supply of each sub-system. In addition, if the bouncing switch is activated by a key for a second time, the main system may sequentially turn off the power module inside each sub-system. Finally, the power to the main system is shut down to lower the static power consumption of the whole system. 
         [0009]    To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a power supply. The power supply includes a main switch, a controller, a trigger circuit, a switching device and a maintenance circuit. The main switch is coupled to a power source and the controller is coupled to the main switch for receiving power provided by the main switch. The trigger circuit is coupled to the power source and the switching device is coupled to the trigger circuit and the maintenance circuit for maintaining the state of the main switch. When the switching device is activated by a first triggering, the trigger circuit turns off the main switch so that power is provided to the maintenance circuit and the controller and the maintenance circuit keeps the main switch in the conducting state. After receiving the power and being activated, the controller acquires the authority over the maintenance circuit so that maintenance circuit keeps the main switch in the conducting state. 
         [0010]    The present invention also provides an alternative power supply. The power supply includes a main switch and a sequential control circuit. The main switch is coupled to a power source and the sequential control circuit has a switching device and a maintenance circuit. The switching device of the sequential control circuit is coupled to the power source and the maintenance circuit is coupled to the main switch and the switching device. The sequential control circuit sequentially emits a first group of predetermined control signals on activation. When the switching device is activated by a first triggering, the switching device conducts the main switch so that power is provided to the sequential control circuit. After the receiving the power and being activated, the maintenance circuit keeps the main switch in the conducting state. 
         [0011]    The present invention also provides a switch apparatus. The switch apparatus includes a main switch, a trigger circuit, a switching device and an auxiliary switch. The main switch is coupled to a power source and the trigger circuit is coupled to the power source. The switching device is coupled to the trigger circuit and the auxiliary switch is coupled to the main switch for maintaining the state of the main switch. 
         [0012]    Furthermore, to prevent erroneous operations in a conventional driving circuit due to noise and abnormalities resulting from a switch working in a conducting state for a long time to cause damages to the device, the present invention also provides a driving auxiliary circuit. An input end of the driving auxiliary circuit is coupled to a driving circuit and an output end of the driving auxiliary circuit is coupled to a switch. The driving auxiliary circuit includes a conversion circuit and a level-adjusting circuit. The conversion circuit couples between the driving circuit and the switch for converting a driving signal generated by the driving circuit. The level-adjusting circuit receives the driving signal converted through the conversion circuit and adjusts the level of the driving signal. Hence, when the input duty cycle of pulse width modulation (PWM) is in a normal vibrating state, the output is also in a vibrating state. Moreover, the level can be downward shifted to prevent erroneous operations caused by noise. On the other hand, when the input duty cycle of the PWM signal is 100%, the driving signal is converted into a low level signal to prevent the operating switch from entering into a prolonged conducting state. 
         [0013]    It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
           [0015]      FIG. 1  is a schematic circuit diagram of a conventional power supply circuit. 
           [0016]      FIG. 2A  is a system block diagram of a power supply according to one preferred embodiment of the present invention. 
           [0017]      FIG. 2B  is a schematic circuit diagram of a power supply according to one preferred embodiment of the present invention. 
           [0018]      FIG. 3  is a timing diagram showing the activating sequence of the power supply according to the present invention. 
           [0019]      FIG. 4  is a timing diagram showing the shutting off sequence of the power supply according to the present invention. 
           [0020]      FIG. 5  is a schematic circuit diagram of a 12V/5V conversion circuit of the power module according to an embodiment of the present invention. 
           [0021]      FIG. 6  is a schematic circuit diagram of a 5V/VGH and 5V/VGL conversion circuits of the power module according to an embodiment of the present invention. 
           [0022]      FIG. 7  is a schematic circuit diagram of an LED driving circuit of the power module according to an embodiment of the present invention. 
           [0023]      FIG. 8  is a schematic circuit diagram of a driving auxiliary circuit according to one preferred embodiment of the present invention. 
           [0024]      FIG. 9  is a timing diagram showing input signal and output signal of the driving auxiliary circuit according to one preferred embodiment of the present invention. 
           [0025]      FIG. 10  is a timing diagram showing direct current (DC) input signal and output signal of the driving auxiliary circuit according to one preferred embodiment of the present invention. 
           [0026]      FIG. 11  is a timing diagram showing the activating sequence of the power modules of the sub-system. 
           [0027]      FIG. 12  is a timing diagram showing the shutting off sequence of the power modules of the sub-system. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
         [0029]      FIG. 2A  is a system block diagram of a power supply according to one preferred embodiment of the present invention. As shown in  FIG. 2A , when a switching device  101  is triggered for the first time, an activating signal C 1  is transmitted to a main switch  106  so that the main switch  106  provides power from a power source PS to a maintenance circuit  107  and a controller  110 . After receiving the power and being activated, the controller  110  transmits a maintenance signal C 4  to the maintenance circuit  107  so that the maintenance circuit  107  continuously transmits a maintenance signal C 2  to the main switch  106 . The timing for activating the maintenance circuit  107  can be the time when the main switch  106  starts providing power source PS power or the time when the maintenance circuit  107  receives the maintenance signal C 4 . The actual operation of the present invention is unaffected by whether the maintenance circuit  107  is activated at the two aforementioned timings or anywhere between them. The trigger circuit  102  stops outputting the activating signal C 1  after a predetermined period. At this moment, the maintenance circuit  107  has already transmitted the maintenance signal C 2 . Since the output of either the activating signal C 1  or the maintenance signal C 2  can trigger the main switch  106  to provide power source PS power, the controller  110  acquires the authorization of controlling the power of the system through the maintenance circuit  107 . The controller  110  continuously monitors the state of the switching device  101 . When the detection signal C 3  indicates that the switch is triggered for a second time, the output of the maintenance signal C 4  is stopped. Now that neither the activating signal C 1  nor the maintenance signal C 2  is output, the main switch  106  stops providing power source PS power. Therefore, the system power source in the present invention stops providing any power to maintain the system in an idle state after the system is shut down, thereby eliminating unnecessary power consumption in the idle state. 
         [0030]      FIG. 2B  is a schematic circuit diagram of a power supply according to one preferred embodiment of the present invention. As shown in  FIG. 2B , the power supply includes a switch apparatus  100 , a controller  110  and a sub-system  120 . The switch apparatus  100  has a switching device  101 , a trigger circuit  102 , a main switch  106 , a maintenance circuit  107  and a resistor  108 . The trigger circuit  102  can be a RC circuit comprising a capacitor  104  and a resistor  105 . The switching device  101  is coupled to a main power source PS through the trigger circuit  102 . When the switching device  101  is triggered by a triggering for the first time, it does not matter whether the triggering time is long or short (in other words, the switching device  101  can be a bouncing switch, a mechanical switch, an infrared switch, a transistor switch or an open-to-short operating switch, the switch in  FIG. 2B  is a bouncing switch), this activation process prompts the trigger circuit  102  to transmit an activating signal to turn on the main switch  106  so that the controller  110  starts to operate. When the controller  110  operates, a maintenance signal is transmitted to the maintenance circuit  107  so that the maintenance circuit  107  keeps the main switch  106  in a conducting state. The maintenance circuit  107  can be an auxiliary switch, for example, a MOS transistor. Through the conduction of the auxiliary switch, the main switch  106  is maintained in a conducting state. Meanwhile, the controller  110  acquires the authorization of controlling the power of the main system so that the power source can continue to provide power to the main system. Then, according to a predetermined sequence, the controller  110  sequentially transmits enable signals to control the activation and operation of various power modules in the sub-system  120 . The power module can be the 12V/5V conversion circuit, the 5V/VGH conversion circuit, the 5V/VGL conversion circuit, the 5V/LED conversion circuit as shown in  FIG. 2B  but is not limited as such. 
         [0031]    The controller  110  continues to monitor the state of the switching device  101  after activation. When the switching device  101  is triggered by a triggering for a second time, for example, for a bouncing switch, the voltage suddenly drops from a high level to a low level, or, for a mechanical switch, the voltage suddenly jumps from a low level to a high voltage. When the controller  110  detects a voltage change in the switching device  101 , the controller  110  sequentially outputs disable signals to shut down and stop the operation of various power modules in the sub-system. Furthermore, the controller  110  also transmits an auxiliary shut down control signal to turn off the auxiliary switch  107 . After turning off the auxiliary switch  107 , (directly through the auxiliary switch  107  or) through the trigger circuit  102 , a shut down signal is transmitted to shut down the main switch  106  and stop outputting power to the main system. Thus, after shutting down the power source, there is no need for the power source to provide any power to maintain the main system and the sub-system in an idle state so that the advantage of a low static power consumption of the whole system is achieved. Moreover, in the activation and shut down process, the power modules are sequentially activated and shut down through the controller. Hence, various operations between system circuits within the system can be synchronized to prevent mutual interference or generation of undesired effects. 
         [0032]      FIG. 3  is a timing diagram showing the activating sequence of the power supply according to the present invention. As shown in  FIGS. 2A and 3 , a bouncing switch is used as an example. The bouncing switch  101  is triggered for the first time in time t 1  to generate an activating signal. Then, the main system (the controller  110 ) is activated at time t 2 . At time t 3 , a main system power supply signal is generated through the maintenance circuit  107  to acquire the authorization of controlling the power source of the main system. At time t 4 , the main system sequentially transmits a sub-system power supply signal to the power modules in the sub-system  120  so that various power modules are activated. The activating signal of the bouncing switch  101  stops at time t 4 . The time t 4  must be later than time t 3  to ensure that the controller  110  has already acquired the authorization of controlling the power of the main system. 
         [0033]      FIG. 4  is a timing diagram showing the shutting off sequence of the power supply according to the present invention. As shown in  FIGS. 2A and 4 , when the bouncing switch  101  is triggered for the second time at time t 6 , a shut down signal is generated, and stopped at time t 7 . After the main system (the controller  110 ) has detected the shut down signal, the main system sequentially transmits a sub-system power supply stopping signal to various power modules in the sub-system  120  at time t 8  so that various power modules are turned off in sequence. Then, the controller  110  generates a main system power supply stopping signal through the maintenance circuit  107  at time t 9  to release the authorization of controlling the power of the main system. Afterwards, the supply of the main system power is stopped at time t 10  due to the shut down of the main switch  106 . 
         [0034]    In the following, the circuits of various power modules in the sub-system  120  of  FIG. 2B  are described.  FIG. 5  is a schematic circuit diagram of a 12V/5V conversion circuit of the power module in the present invention. As shown in  FIGS. 2B and 5 , after activating the controller  110 , the controller  110  transmits an enable signal to the 12V/5V conversion circuit to activate the conversion controller  300 . According to the control signal of the conversion controller  300 , the driving circuit  310  transmits a driving signal to control the switching of the power switching circuit in the conversion circuit  320  so that the conversion circuit  320  converts the power from the power source to supply the system. The conversion controller  300  stabilizes the output voltage through the feedback signal of the feedback circuit  330 . When the controller  110  detects the shut down signal (that is, a voltage change in the switch  101 ), disable signal is sequentially transmitted. When the conversion controller  300  receives the disable signal, the conversion controller  300  makes the driving circuit  310  stop outputting power from the power source to the conversion circuit  320 . Furthermore,  FIG. 6  is a schematic circuit diagram of a 5V/VGH and 5V/VGL conversion circuits of the power module according to an embodiment of the present invention.  FIG. 7  is a schematic circuit diagram of an LED driving circuit of the power module according to an embodiment of the present invention. The operating principles of the controllers  400  and  500 , the driving circuits  410  and  510  and the feedback circuits  430  and  530  in the 5V/VGH and 5V/VGL conversion circuits and the LED driving circuit are identical to that of the aforementioned 12V/5V conversion circuit. Hence, a detailed explanation is omitted. The VGH/VGL (positive gate voltage/negative gate voltage) conversion circuit in  FIG. 6  comprises a step-up voltage circuit for generating the VGH voltage and a negative voltage circuit for generating the VGL voltage. The conversion circuit  520  in  FIG. 7  is a step-up voltage circuit for generating a driving voltage to drive the LED light-emitting module  540 . Since the operation of these conversion circuits should be familiar, a detailed description is omitted. 
         [0035]    In addition, in a conventional power module, noise in the driving signal may lead to faulty switching of the power switching circuit. Alternatively, some special, abnormal states (for example, duty cycle at 100% so that the switch is kept in the conducting state at all times) may lead to short circuit, thereby damaging the device. In the present invention, a driving auxiliary circuit between the power switch and the driving circuit may be added. When the input terminal receives no driving signal, the voltage at the output terminal is defined as a low voltage so that the switch in the power switching circuit is kept in a shut down state. When the input terminal receives a driving signal, the output terminal outputs a converted driving signal so that the switch in the power switching circuit is turned off or turned on according to the driving signal. 
         [0036]      FIG. 8  is a schematic circuit diagram of a driving auxiliary circuit according to one preferred embodiment of the present invention. As shown in  FIG. 8 , the auxiliary driving circuit  600  includes a capacitor  602 , a diode  604  and a resistor  606 . The capacitor  602  is coupled between the driving circuit and the switch for filtering and converting the driving signal. The diode  604  and the resistor  606  are connected in parallel between the positive and the negative output terminals so that the level of the driving signal after conversion through the capacitor  602  is defined. Thus, when the input terminal IN of the driving auxiliary circuit  600  receives no signal, the resistor  606  forces the voltage at the output terminal OUT to a zero voltage. When the input terminal IN receives a driving signal, the driving signal converted through the capacitor  602  is output through the output terminal OUT. As shown in  FIG. 9 , if the input signal is a pulse signal produced by an oscillator in a common vibration mode, the output signal is pulled down after conversion through the capacitor  602 . When the duty cycle of an input pulse width modulation (PWM) signal reaches 100%, the switch in the conventional technique is set to a short circuit conducting state for a prolonged period so that the device is very likely damaged. In the present invention, as shown in  FIG. 10 , after filtering out the DC component through the capacitor  602 , a low level function representing a logic signal ‘0’ is output to prevent the operating switch from staying in the conducting state for a prolonged period. 
         [0037]    In actual applications, the power modules in the sub-system of the present embodiment can be any power modules, for example, a voltage step-up power module, a voltage step-down power module, a DC/DC converter, a DC/AC converter, an AC/DC converter, an AC/AC converter. However, the power modules are not limited as such. 
         [0038]    In actual applications, the activation sequence of the power modules in the sub-system is limited by the device to be driven. For example, the power module for driving the LCD module display must be provided with a voltage of 5V before providing the VGH/VGL voltage.  FIG. 11  is a timing diagram showing the activating sequence of the power modules of the sub-system. As shown in  FIG. 11 , the activation sequence of the power modules in the sub-system is the 12V/5V conversion circuit and then the VGH/VGL conversion circuit. The controller  110  in  FIG. 2B  also transmits an enable signal to the 12V/5V conversion circuit and the VGH/VGL conversion circuit in that order. In the process of shutting down the power modules in the sub-system, the VGH/VGL conversion circuit must be shut down before the 12V/5V conversion circuit.  FIG. 12  is a timing diagram showing the shutting down sequence of the power modules in the sub-system. As shown in  FIG. 12 , the controller  110  transmits a disable signal in sequence to the VGH/VGL conversion circuit and the 12V/5V conversion circuit. For some of the conversion circuit having no special activation or sequentially shutting requirements like the LED driving circuit in  FIG. 7  can be independently controlled. In other words, the timing for activating or shutting these conversion circuits can be freely set. However, the timing for activating or shutting off various conversion circuits are preferably set as far apart as possible to prevent high voltage ripple problem caused by the simultaneous activation or shutting of circuits. 
         [0039]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.