Abstract:
A power controller in a multi-chip module is disclosed. The power controller comprises a power controller die, an ultra-high voltage startup die, and a multi-chip module. The power controller die is operable to control a power switch when powered by an operation power source. The operation power source has a maximum voltage limit of tens volt. The ultra-high voltage startup die comprises an ultra-high voltage pad tolerable to receiving an input line voltage higher than one hundred volt. During a startup procedure the ultra-high voltage startup die charges the operation power source, and during a normal operation the ultra-high voltage startup die substantially performs an open-circuit. The multi-chip module packages both the power controller die and the ultra-high voltage startup die.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Taiwan Application Series Number 102127029 filed on Jul. 29, 1013, which is incorporated by reference in its entirety. 
       BACKGROUND 
       [0002]    The present disclosure relates generally to power controllers suitable for switching mode power supplies, more particularly, to power controllers with ultra-high voltage startup. 
         [0003]    A switching mode power supply normally employs at least one power switch to manipulate the current through an inductive device. In comparison with other kinds of power supplies, switching mode power supplies enjoy compact product size and excellent power conversion rate, and accordingly are popular and welcome in the field of power supply manufacturing. 
         [0004]      FIG. 1  demonstrates a conventional switching mode power supply  8 . Power controller  14 , which is an integrated circuit individually packaged, controls a power switch  10  to be open-circuit or closed-circuit, thereby controlling the current flowing through the primary winding  16 . Input power source V IN , which might be generated by using a bridge rectifier to rectify the alternative-current (AC) mains voltage from a power plug, could be as high as 500 volt. Based on the terminology in the art, here in this specification, high voltage refers to as the voltage with ten to tens volt, and ultra-high voltage refers to as the voltage with more than one hundred volt. When input power source V IN  just happens, such as at the moment when switching mode power supply  8  is just connected to AC mains voltage, ultra-high voltage startup circuit  12 , which is another integrated circuit individually packaged, starts charging capacitor  18  to build up operation power source V CC . Only when the operation power source V CC  is high enough in volt, the ultra-high voltage startup circuit  12  then stops the charging. Before the charging is stopped, power controller  14  could start manipulating the current flowing through the primary winding  16 , causing an auxiliary winding  20  to generate current and charge the capacitor  18 . 
         [0005]    Simply put, ultra-high voltage startup circuit  12 , as it is named, works only during a startup procedure for roughly building up the operation power source V CC . After that startup procedure, power controller  14  normally turns on and off the power switch  10 , and ultra-high voltage startup circuit  12  is OFF to substantially perform as an open-circuit, which consumes no current or electrical energy. 
         [0006]      FIG. 2  demonstrates another switching mode power supply, where power controller  22  alone performs ultra-high voltage startup and the control of the power switching  10 . Simply speaking, power controller  22  is a single integrated circuit package, in which only one semiconductor die is packaged while it implements the functions of both the power controller  14  and the ultra-high voltage startup circuit  12 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following drawings. In the drawings, like reference numerals refer to like parts throughout the various figures unless otherwise specified. These drawings are not necessarily drawn to scale. Likewise, the relative sizes of elements illustrated by the drawings may differ from the relative sizes depicted. 
           [0008]    The invention can be more fully understood by the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0009]      FIG. 1  demonstrates a conventional switching mode power supply; 
           [0010]      FIG. 2  demonstrates another switching mode power supply; 
           [0011]      FIG. 3  demonstrates a power controller according to embodiments of the invention; 
           [0012]      FIG. 4  demonstrates some circuits in the ultra-high voltage startup die and the PWM controller die of  FIG. 3 ; 
           [0013]      FIG. 5  demonstrates another power controller according to embodiments of the invention; 
           [0014]      FIG. 6  shows a power controller, which is a chip-stack package; and 
           [0015]      FIG. 7  demonstrates a power controller in an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 3  demonstrates a power controller  30  according to embodiments of the invention. In one embodiment, the power controller  30  replaces the power controller  22  in  FIG. 2 . 
         [0017]    Separately positioned inside the power controller  30  are a PWM controller die  36  and an ultra-high voltage startup die  38 , packaged together inside a multi-chip module  33 , which has a leadframe with a die paddle  32  and leads  34   a ˜ 34   h . The PWM controller die  36  and the ultra-high voltage startup die  38  could be fixed on the die paddle  32 , using conductive glue such as silver paste. The lead  34   d  extends to connect with the die paddle  32 , and acts as a ground pin GND. PWM controller die  36  could send PWM signal to pin GATE for turning on or off an external power switch, such as the power switch  10  in  FIG. 2 . 
         [0018]    In one embodiment, the maximum input voltage limit of the ultra-high voltage startup die  38  that does not cause damage is at least 500V, and that of the PWM controller die  36  is at least 40V. More specifically, the maximum voltage limit at pin UHV that causes no harm to the ultra-high voltage startup die  38  is at least 500V, and that maximum voltage limit at pin VCC that causes no harm to the PWM controller die  36  is at least 40V. 
         [0019]    The ultra-high voltage startup die  38  is positioned in one corner of the die paddle  32 , which is the closest to lead  34   h , and away from the other corners. The lead  34   h  is also referred to as the ultra-high voltage input pin UHV. In  FIG. 3 , leads  34   a ,  34   d , and  34   h  are referred to in this specification as corner leads because that their locations are in corners of a leadframe. One end of the bonding wire  40  is on the lead  34   h  (or pin UHV), and the other end on an ultra-high voltage pad, which locates in a central portion of the ultra-high voltage startup die  38  and is tolerable to receiving an input line voltage higher than 500v. The bonding wire  46  electrically connects a charging pad of the ultra-high voltage startup die  38  to the PWM controller die  36 . The bonding wire  44  electrically connects a ground pad of the ultra-high voltage startup die  38  to the die paddle  32 , in order to provide a ground voltage to the ultra-high voltage startup die  38 . The bonding wire  48  connects a control pad in the ultra-high voltage startup die  38  to the PWM controller die  36 , which accordingly controls the ultra-high voltage startup die  38 . Shown in  FIG. 3 , the ultra-high voltage startup die  38  has only four kinds of pads, consisting of ultra-high voltage pad, charging pad, ground pad, and control pad. 
         [0020]      FIG. 4  demonstrates some circuits in the ultra-high voltage startup die  38  and the PWM controller die  36 . In one embodiment, the ultra-high voltage startup die  38  has only two active devices, JFET  50  and MOSFET  52 , and both are ultra-high voltage tolerable devices. As demonstrated in  FIG. 4 , the PWM controller die  36  includes a zener diode  54  and a current-limiting resistor  56 . Inside the ultra-high voltage startup die  38 , the drain and the source of JFET  50  are connected to the drain and the gate of MOSFET  52 , respectively. The drain and the source of the MOSFET  52  are connected via bonding wires to pin UHV and a diode  57  in the PWM controller die  36 . Via a control pad and at least one associated bonding wire, the gate of the MOSFET  52  is electrically connected to the zener diode in the PWM controller die  36 . The zener diode  54  and the current-limiting resistor  56  function together as a voltage-clamping circuit to limit the maximum voltage on the control pad. In one embodiment, the threshold voltage for the JFET  50  is negative. During a startup procedure when the PWM controller die  36  keeps a power switch open, the JFET  50  conducts a relatively-small current to charge the gate of the MOSFET  52 . When a gate-to-source voltage of the MOSFET  52  exceeds a threshold voltage, the MOSFET  52  conducts a relatively-large current to charge and build, via the diode  57 , the operation power source V CC  on pin VCC. In the same time, the JFET  50  is turned off by itself because of body effect and the raised voltage at its source electrode. For example, the JFET  50  could be designed to be off if the gate voltage of the MOSFET  52  is equal to or exceeds 15V. In case that the threshold voltage of the MOSFET  52  is about 5V, the ultra-high voltage startup die  38  will charge the operation power source V CC  to be as high as 10V (15V-5V) during the startup procedure, after which a normal operation follows. During the normal operation, the PWM controller die  36  turns on and off a power switch, and the gate voltage of the MOSFET  52  and the operation power source V CC  are maintained to be higher than or equal to 15V and 10V, respectively. It can be derived that both the MOSFET  52  and the JFET  50  are in an off state during the normal operation, such that the ultra-high voltage startup die  38  performs an open-circuit, substantially consuming no electric current or power. 
         [0021]    Following exemplifies some benefits introduced by the power controller  30  in  FIG. 3 . 
         [0022]    1. Semiconductor manufacturing simplification: In light of semiconductor manufacturing process, the process flow for making the ultra-high voltage startup die  38  differs largely to that for making the PWM controller die  36 , and they&#39;d better be separately manufactured to enjoy optimized process recipes. Otherwise, if they are merged in one die, the high-temperature diffusion process needed for manufacturing ultra-high voltage devices, for example, will degrade the performance of the high voltage devices or enlarge the silicon area required for the high voltage devices. Individual and separated manufacturing processes for the PWM controller die  36  and the ultra-high voltage startup die  38  could realize compact die sizes and improved yields thereof, saving the silicon cost. 
         [0023]    2. Noise isolation: In comparison with the single die in  FIG. 2 , the PWM controller die  36  and the ultra-high voltage startup die  38  are formed on two different and separated substrates. Therefore, the noise in one die that is unwelcome by analog circuits will not go to the other die via a common substrate. In case that some noise occurs to the substrate of the ultra-high voltage startup die  38  for example, it will be first conducted by the die paddle  32  to a ground, rather than disturbing the substrate of the PWM controller die  36 . 
         [0024]    3. Component storage management: The PWM controller die  36  and the ultra-high voltage startup die  38  together are packaged in one single multi-chip module  33 , to be the power controller  30  in  FIG. 3 . In appearance, the power controller  30  is a single packaged integrated circuit, just the same as the power controller  22  in  FIG. 2 . Unlike the switching mode power supply in  FIG. 1  that has two components respectively functioning for pulse-width modulation and ultra-high voltage startup, a power converter system using the power controller  30  could enjoy low component count and easy storage management during manufacturing. 
         [0025]      FIG. 5  demonstrates another power controller  30   a  according to embodiments of the invention, where the PWM controller die  36  is positioned on the die paddle  32  in a tilted way that its edges are not parallel to the edges of the die paddle  32 , while the edges of the ultra-high voltage startup die  38  are. The titled way is to make a larger space in the top-right corner of the die paddle  32 , to hold the ultra-high voltage startup die  38  therein. This enlarged space can only be achieved when the PWM controller die  36  is separated from the ultra-high voltage startup die  38 . 
         [0026]    Shown in  FIG. 6  is a power controller  30   b , which is a chip-stack package. The ultra-high voltage startup die  38  and the PWM controller die  36  are stacked sequentially on the die paddle  32  while bonding wires and some conductive material provide electrical interconnection. In  FIG. 6 , the ultra-high voltage startup die  38  are the topmost die, locating in the corner of a die paddle closest to pin UHV. 
         [0027]    In one embodiment, an ultra-high voltage startup die substantially consists of a JFET and a MOSFET, as demonstrated in  FIGS. 3 and 4 . Of course, there must be several passive or parasitic devices, such as resistors or capacitors in the ultra-high voltage startup die  38 , and they are not shown in  FIGS. 3 and 4 . In another embodiment, an ultra-high voltage startup die has no MOSFET and substantially consists of one or more JFETs.  FIG. 7  demonstrates a power controller  30   c , where the PWM controller die  36  and the ultra-high voltage startup die  60  together are packaged in one single multi-chip module. The ultra-high voltage startup die  60  substantially has only one active device, JEFT  62 , while passive devices in the ultra-high voltage startup die  60  are not shown. For example, JFET  62  is turned off by itself if a charging pad connecting the JFET  62  to the diode  57  has a voltage more than 11V. Demonstrated in  FIG. 7 , the ultra-high voltage startup die  60  only has three kinds of pads, consisting of ultra-high voltage pad, charging pad, and ground pad, respectively connected to ultra-high voltage input pin UHV, the diode  57  in the PWM controller die  36 , and a ground voltage. 
         [0028]    While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.