Patent Document

BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a driving circuit and a light emitting diode (LED) driving controller, and more particularly to the LED driving circuit and the driving controller having a function of latch protection. 
         [0003]    2. Description of Related Art 
         [0004]    Reference is made to  FIG. 1  showing a schematic diagram of the conventional driving circuit. The driving circuit has a converting circuit including an inductor L, a diode D, a transistor switch SW, and a capacitor C, and a controller  10 . The driving circuit is used to drive a load  30 , and a resistor R couples to this load  30  which generates a feedback signal FB according to the current flowing through the load  30 . The controller  10  then generates a control signal Gate to control on or off state of the transistor switch SW according to the feedback signal FB. Accordingly, an electric power transferred from an inputted voltage VIN to an output end of the converting circuit is modulated to stabilize the current flowing through the load  30 . 
         [0005]    The controller  10  includes an error amplification circuit  12 , an oscillation circuit  14 , a pulse width modulation circuit  16 , a driving control circuit  18 , and a protection circuit  20 . The error amplification circuit  12  receives a reference voltage Vref and the feedback signal FB, and accordingly generates an error amplification signal COMP. The pulse width modulation circuit  16  receives the error amplification signal COMP and a ramp signal SAW outputted from the oscillation circuit  14 , in order to generate a pulse width modulation signal PWM. The driving control circuit  18  generates the control signal Gate to control the transistor switch SW according to this pulse width modulation signal PWM. The protection circuit  20  outputs a protection signal PROT to the driving control circuit  18  when the driving circuit operates abnormally. Thus, the driving control circuit  18  may temporarily stop outputting the control signal Gate to stop the transfer of the inputted voltage VIN to the converting circuit. When the abnormally condition is removed, the protection circuit  20  stops outputting the protection signal PROT, and thus the driving control circuit  18  could re-transmit the control signal Gate to switch the on/off state of the transistor switch SW. 
         [0006]    However, the root cause of abnormality may not be identified and eliminated by the stoppage of the transmission of the control signal Gate. The driving circuit may still operate abnormally again when the control signal Gate is re-transmitted to control the on/off state of the transistor switch SW. Therefore, the conventional approach may cause more power consumption, and more un-stable, and even increase the likelihood of damaging it. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the drawback of the conventional technology may incur unnecessary power consumption, destabilize the whole circuitry, or even increase the likelihood of damaging it when operating abnormally, a driving circuit and a driving controller for the driving circuit in accordance with the present invention is disclosed. The driving controller for controlling the same according to present invention may remain in a protection mode when operating abnormally until the driving controller is restarted. Furthermore, the present invention may prevent misjudgment associated with abnormal operation. 
         [0008]    In order to achieve the above purpose, the present invention provides an LED driving controller for controlling an LED driving circuit to drive an LED module. The LED driving controller includes a feedback control unit and a protection unit. This feedback control unit outputs a control signal for adjusting a driving current in accordance with a current feedback signal indicative of the driving current flowing through the LED module. The protection unit determines whether or not generating a protection signal based on the current feedback signal to stop the LED driving circuit from outputting the driving current until the LED driving controller is restarted. 
         [0009]    The present invention also provides a driving circuit for driving a load. The driving circuit comprises a driving power supply and a controller. The driving power supply supplies a first power source to drive the load. The controller is coupled to a second power source to receive an electric power for operating, and controls the driving power supply to supply the first power source to the load when operating in a first mode, and stops the driving power supply from supplying the first power source to the load when operating in a second mode. Wherein, the controller exclusively operates in the first mode before the driving power supply provides the first power source. 
         [0010]    In order to further understand the characteristics and technical contents of the present invention, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The foregoing aspects and many of the attendant advantages of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
           [0012]      FIG. 1  shows a schematic diagram of the conventional driving circuit; 
           [0013]      FIG. 2  is a circuit diagram illustrating a driving circuit in accordance with one embodiment of the present invention; 
           [0014]      FIG. 3  a circuit diagram illustrating a driving circuit in accordance with one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Please refer to  FIG. 2  of a circuit diagram illustrating a driving circuit in accordance with one embodiment of the present invention. The driving circuit includes a controller  100  and a driving power supply for driving a load  145 . The driving power supply includes a switch  140 , an inductance  142 , a diode  144 , and an output capacitor  146 . In one implementation, the driving power supply is a direct current to direct current (DC-DC) boost converting circuit for converting an inputted voltage VIN, coupled to the inductance  142 , into an outputted voltage VOUT. The controller  100  receives a voltage feedback signal VFB generated from a voltage detection circuit  134 . This voltage feedback signal VFB is indicative of a value of the outputted voltage VOUT. A control signal S 1  is thus generated accordingly for controlling the switch  140  so as to stabilize the outputted voltage VOUT. 
         [0016]    The controller  100  includes a feedback control unit  110  and a protection unit  120 . The feedback control unit  110  includes an oscillation unit  102 , an error amplification unit  104 , a pulse width modulation unit  106 , and a driving control unit  108 . The error amplification unit  104  receives the voltage feedback signal VFB and a reference signal Vr 1 , and accordingly generates an error amplification signal Vea. The pulse width modulation unit  106  is coupled to the oscillation unit  102  and the error amplification unit  104  for receiving the error amplification signal Vea and a triangle wave signal generated by the oscillation unit  102 . 
         [0017]    The pulse width modulation unit  106  thus may generate a pulse width modulation signal  107 . The driving control unit  108  is coupled to the pulse width modulation unit  106  and the protection unit  120  for receiving the pulse width modulation signal  107  and a protection signal PROT generated by the protection unit  120 . The driving control unit  108  adjusts a duty cycle of a control signal S 1  in accordance with the pulse width modulation signal  107 . The adjustment of the duty cycle is the basis for adjusting the power supplied to the load  145 . And the driving control unit  108  further determines whether to stop the power supplied to the load  145  according to the protection signal PROT. 
         [0018]    The controller  100  further has an overly-low voltage comparison unit  122 , an overly-high voltage comparison unit  124 , an overly-low current comparison unit  126 , and an overly-high current comparison unit  128 . The overly low voltage comparison unit  122  receives the voltage feedback signal VFB and an overly low voltage reference signal Vuvp. When the level of the voltage feedback signal VFB is lower than the level of the overly-low voltage reference signal Vuvp (i.e., the output voltage VOUT is lower than a predetermined overly-low voltage threshold), the overly-low voltage comparison unit  122  may output an over-low voltage protection signal UVP. Further, the overly-high voltage comparison unit  124  receives the voltage feedback signal VFB and an overly-high voltage reference signal Vovp. When the level of the voltage feedback signal VFB is higher than the level of the overly high voltage reference signal Vovp (i.e., the output voltage VOUT is higher than a predetermined overly-high voltage threshold), the overly-high voltage comparison unit  124  outputs an overly-high voltage protection signal OVP. 
         [0019]    Further, the overly-low current comparison unit  126  receives an overly-low current reference signal Vucp, and a current feedback signal IFB generated by a current detection circuit  132 . It is noted that the current feedback signal IFB represents a level of a driving current Iload flowing through the load  145 . When the level of the current feedback signal IFB is lower than the level of the overly-low current reference signal Vucp (i.e., the current Iload is lower than a predetermined overly-low current threshold), an overly-low current protection signal UCP is outputted. Still further, the overly-high current comparison unit  128  receives the current feedback signal IFB and an overly-high current reference signal Vocp. When the level of the current feedback signal IFB is higher than the level of the overly-high current reference signal Vocp (i.e., the driving current Iload is higher than a predetermined overly-high current threshold), an overly high current protection signal OCP is outputted. When the protection unit  120  receives the overly-low voltage protection signal UVP, the overly-high voltage protection signal OVP, the overly-low current protection signal UCP, or the overly-high current protection signal OCP, the protection signal PROT is outputted to stop the controller  100  from outputting the control signal S 1 . The stoppage of the output of the control signal S 1  causes the driving power supply not to transfer the power to the load  145  until the controller  100  is restarted. In other words, in order to prevent the circuit from repeatedly attempting to back to the normal operation, the controller  100  is latched into a protection mode once the controller  100  operates abnormally. 
         [0020]    In general, the controller  100  may release the protection unit  120  from the “latched” state for stopping outputting the protection signal PROT by sending an external re-started signal (not shown) to the protection unit  120 . Alternatively, the internal circuit of the controller  100  can be reset by stopping supplying the power to the controller  100 . 
         [0021]    In addition to having the controller  100  enter into the protection mode when the controller operates abnormally, another implementation of the present invention relies on whether any one of protection detecting signals is generated for a predetermined period of time. For example, the overly-low voltage protection signal UVP, the overly-high voltage protection signal OVP, the overly-low current protection signal UCP, the overly-high current protection signal OCP, or other like protection detecting signal has been present for a corresponding predetermined period of time. If so, the protection unit  120  then outputs the protection signal PROT for preventing the controller  100  from being shut down merely because of temporary abnormality, which may be caused by accidental slight removal or touch. 
         [0022]    Moreover, one implementation in accordance with the present invention may count the number of the occurrences of the protection detecting signals and determine whether the number exceed a predetermined threshold. If so, the protection unit  120  then outputs the protection signal PROT. In one implementation, the predetermined threshold is three. In doing so, the present invention may minimize the possibility of misjudgment as the result of temporary abnormality associated with the circuit. 
         [0023]    The above-described embodiment is an exemplary example that depicts the DC-DC boost converting circuit being controlled by feedback voltage. The present invention is applicable to any driving circuit having protective function. Please  FIG. 3  is a circuit diagram illustrating a driving circuit in accordance with on embodiment of the present invention. The driving circuit is  FIG. 3  particularly associates with a dual power circuit system having two independent power sources for loads and a controller. 
         [0024]    In  FIG. 3 , the driving circuit includes a controller  200  and a driving power supply  250 . The driving power supply  250  is used to supply a first power source VDDH to drive the load  245 . In one implementation, the load  245  is an LED module. The controller  200  is coupled to a second power source VDDL for receiving the required electric power. When no abnormal condition occurs in the driving circuit, the controller  200  operates in a normal mode. In the meantime, the controller  200  outputs a control signal S 2  to control the switch  240 , which in turn controls the power supply provided by the driving power supply  250  to the load  245 . Once the controller  200  detects that the driving circuit operates abnormally, the controller  200  may operate in a protection mode in order to stop the driving power supply  250  from supplying the power to the load  245 . It is worth noting that the controller  200  may make a misjudgment when an input of the first power source VDDH is later than that of the second power source VDDL. For handling the above-mentioned misjudgment, the controller  200  in accordance with the present invention may determine whether the driving power supply  250  starts to provide the first power source VDDH or not. When the first power source VDDH has not yet being supplied, the controller  200  may not operate in the protection mode. 
         [0025]    In particular, the controller  200  includes a feedback control unit  210  and a protection unit  220 . The feedback control unit  210  includes an error amplification unit  212  and an AND gate  214 . The error amplification unit  212  receives a reference signal Vr 2  and a current feedback signal Cs generated by a current detection circuit  232 . The current feedback signal Cs may represent the level of the driving current flowing through the load  245 . The control signal S 2  may be generated according to the level of the driving current flowing through the load  245 . In one implementation, the control signal S 2  is used to control an equivalent resistance of the switch, so as to stabilize the driving current through the load  245  at a predetermined level. The AND gate is coupled to the error amplification unit  212  and the protection unit  220 , and receives a light modulation signal DIM and a protection signal PROT generated by the protection unit  220 . Further, whether the power is supplied to the load  245  may hinge on the protection signal PROT and the light modulation signal DIM. 
         [0026]    The controller  200  further includes a protection starting unit  215 , an overly-low voltage comparison unit  222 , an overly-high voltage comparison unit  224 , an overly-low current comparison unit  226 , and an overly-high current comparison unit  228 . The protection starting unit  215  includes an inverter  216 , and a one shot circuit  218 . The protection starting unit  215  is coupled to the overly-low current comparison unit  226  and the protection unit  220 . 
         [0027]    Further, the overly-low current comparison unit  226  receives a current feedback signal Cs and an overly-low current reference signal Vucp. When the first power source VDDH is not yet provided to the load  245 , the level of the current feedback signal Cs is lower than the level of the overly-low current reference signal Vucp. As such, the overly-low current comparison unit  226  may output the overly-low current protection signal UCP of a “high” level. This “high” level overly-low current protection signal UCP may cause the protection unit  220  to remain inactivated since such overly-low current protection signal UCP in inverted to a low level signal through the inverter  216 , which causes the one shot circuit  218  to output a low level protection starting signal. Consequently, the controller  200  may not activate the protective function when the first power source VDDH is not provided to the load  245  and thus the controller  200  may not operate in the protection mode. 
         [0028]    Once the first power source VDDH is supplied to the load  245 , the level of the current feedback signal Cs is higher than the level of the overly-low current reference signal Vucp. The overly-low current comparison unit  226  outputs a low level overly-low current protection signal UCP. Through the inverter  216 , the low level overly-low current protection signal UCP is inverted to a high level. Therefore, the one shot circuit  218  may be triggered to output the high level protection starting signal, so as to start the protection unit  220 . 
         [0029]    After the protection unit  220  is started, if the level of the current feedback signal Cs is lower than the level of the overly-low current reference signal Vucp (i.e., the current flowing through the load  245  is lower than a predetermined overly-low current threshold), an overly-low current protection signal UCP is generated. The overly-low voltage comparison unit  222  receives an overly-low voltage reference signal Vuvp and a voltage feedback signal Vs. This voltage feedback signal Vs represents the driving voltage of the first power source VDDH. 
         [0030]    When the level of the voltage feedback signal Vs is lower than the level of the overly-low voltage reference signal Vuvp (i.e., the driving voltage of the first power source VDDH is lower than a predetermined overly-low voltage threshold), an overly-low voltage protection signal UVP is outputted. The overly-high voltage comparison unit  224  receives the voltage feedback signal Vs and an overly-high voltage reference signal Vovp. When the level of the voltage feedback signal Vs is higher than the level of the overly high voltage reference signal Vovp, (i.e., the driving voltage of the first power source VDDH is higher than a predetermined overly high voltage threshold), an overly-high voltage protection signal OVP is generated. The overly-high current comparison unit  228  receives the current feedback signal Cs and an overly-high current reference signal Vocp. When the level of the current feedback signal Cs is higher than the level of the overly-high current reference signal Vocp (i.e., the current flowing through the load  245  is higher than a predetermined overly-high current threshold), an overly-high current protection signal OCP is outputted. Once the protection unit  220  receives the overly-low voltage protection signal UVP, the overly-high voltage protection signal OVP, the overly-low current protection signal UCP, or the overly-high current protection signal OCP, the protection signal PROT is outputted for stopping the controller  200  from outputting the control signal S 2 . Consequently, the first power source VDDH is no longer provided to the load  245  until the controller  200  is restarted. 
         [0031]    In accordance with another embodiment of the present invention, the protection unit  220  outputs the protection signal PROT as the mentioned protection signals UVP, OVP, UCP, OCP or other like protection signals of the driving circuit have been generated for a predetermined period of time. Alternatively, the protection unit  220  outputs the protection signal PROT when the number of the occurrences of one of the protection signals UVP, OVP, UCP, OCP, or other like protection signal has been detected for more than a predetermined value in order to avoid any misjudgment associated with temporarily circuit abnormality. 
         [0032]    Though the controller  200  may determine whether the first power source VDDH is provided to the load  245  via the state of detection point A, in another implementation the controller  200  may determine the same by detecting any one point (such as point B or C shown in  FIG. 3 ) coupled to the driving power supply  250 . 
         [0033]    The above-mentioned descriptions represent merely the preferred embodiment of the present invention, without any intention to limit the scope of the present invention thereto. Various equivalent changes, alternations or modifications based on the claims of present invention are all consequently viewed as being embraced by the scope of the present invention.

Technology Category: 5