Abstract:
A hybrid power supply architecture including a microcontroller, a linear regulator, a first current sensing unit, a second current sensing unit, a switching regulator, a PWM controller and a hybrid output stage is disclosed. The linear and switching regulators respectively perform linear and switching regulation according to a first enable signal and a second enable signal generated by the microcontroller to generate a linear output power and a switching output power. The first and second current sensing units respectively generate a first current sensing signal and a second current sensing signal by sensing the linear and switching output powers. The microcontroller receives the first and second current sensing signals to determine a loading state. The switching regulator is enabled to actuate in case of heavy loading, and particularly the linear regulator is shut off only when the switching output power is stable, thereby implementing the best conversion efficiency.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Taiwanese patent application No. 103102177, filed on Jan. 21, 2014, which is incorporated herewith by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a hybrid power supply architecture, and more specifically to a hybrid power supply architecture actuating a linear regulator and/or a switching regulator based on a loading state so as to achieve optimal electrical efficiency of seamless switching for supplying hybrid power. 
     2. The Prior Arts 
     For electronic devices with different electrical properties, it is generally needed to provide various power sources having appropriate voltage, current or electric power. For instance, electric motors are actuated by 12 DCV, analog chips are fed with 3.3V, and digital chips operate at 1.8V. Therefore, power management manufacturers have developed kinds of power regulation device to meet the requirement of the market. Additionally, some voltage regulators with the function of stabilizing the output voltage are needed when the original input power is possibly unstable, like the city power resulting in instant fluctuation of the output voltage due to imbalance of loading. Alternatively, when the output voltage or the output current becomes unstable because the ability of the power supply is limited and fierce variation of the loading is not overcome, the voltage regulator is also necessary. 
     Two typical schemes including linear regulation and switching regulation have been widely used in the common application field of electronic devices. Linear regulation generally employs linear electronic components such as operational amplifier to co-operate with some voltage or current sensing circuit so as to control the output unit such as power transistor, thereby generating a stable output power by dynamical regulation according to the loading. For switching regulation, the PWM signal with high frequency component is used to control and turn on/off the specific transistor such that the original input power is converted into the output power with specific voltage, current or electric power. At the same time, noise components in the input power are screened out, achieving the object of power regulation and/or power conversion. 
     Practically, both linear regulation and switching regulation consume part of electric power supplied by the input power, leading to inevitable operation loss which changes with the loading. For example, linear regulation has lower operation loss at light loading, and switching regulation has lower operation loss at heavy loading. In other words, linear regulation is suitable for the application of light loading, and switching regulation is preferred for heavy loading. As a result, it is impossible to use only one of linear regulation and switching regulation to substantially reduce the overall operation loss when the variation range of loading is large, further causing low electrical efficiency. 
     Therefore, it greatly needs a new hybrid power supply architecture to dynamically switch the linear regulation and the switching regulation based on the actual electrical loading. In particular, the purpose of power supply with seamless switching is successfully fulfilled, and low power consumption and stable output power are implemented, thereby overcoming the problems in the prior arts. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a hybrid power supply architecture for converting an input power into an output power with different voltage and current compared to the input power, and further supplying the output power to an external load. The hybrid power supply architecture comprises a microcontroller, a linear regulator, a first current sensing unit, a switching regulator, a second current sensing unit and a hybrid output stage. The linear regulator and the switching regulator respectively perform linear regulation and switching regulation according to the first and second enable signals generated by the microcontroller so as to generate a linear power and a switching power. The first and second current sensing units respectively sense the linear power and the switching power to generate a first current sensing signal and a second current sensing signal. The microcontroller receives the first and second current sensing signals to determine the loading state is light or heavy. Specifically, the microcontroller turns on the linear regulator and turns off the switching regulator at the beginning of supplying the input power, and then turns on the switching regulator when the loading state becomes heavy. 
     In particular, the linear regulator is turned off only when the switching output power is steady. Similarly, the microcontroller turns on the linear regulator when the loading state becomes light, and the switching regulator is turned off only when the linear output power becomes steady. 
     In other words, the present invention may control the linear regulator and the switching regulator based on the loading state such that the linear regulator and/or the switching regulator is turned on/off for light and heavy loading, thereby increasing the efficiency of power conversion. Especially, during the switching period for the light loading or the heavy loading, the linear regulator and the switching regulator are still kept working so as to maintain stability of the output power and achieve seamless switching hybrid power supply, thereby effectively protecting the external load. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be understood in more detail by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein: 
         FIG. 1  is a system diagram of the hybrid power supply architecture according to one embodiment of the present invention; 
         FIG. 2  is an illustrative circuit of the linear regulator of the hybrid power supply architecture according to the present invention; 
         FIG. 3  is an illustrative circuit of the switching regulator of the hybrid power supply architecture according to the present invention; and 
         FIG. 4  is an illustrative circuit of the hybrid output stage of the hybrid power supply architecture according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention may be embodied in various forms and the details of the preferred embodiments of the present invention will be described in the subsequent content with reference to the accompanying drawings. The drawings (not to scale) show and depict only the preferred embodiments of the invention and shall not be considered as limitations to the scope of the present invention. Modifications of the shape of the present invention shall too be considered to be within the spirit of the present invention. 
     Please refer to  FIG. 1  illustrating a system diagram of the hybrid power supply architecture according to one embodiment of the present invention. As shown in  FIG. 1 , the hybrid power supply architecture of the present invention generally comprises a microcontroller  10 , a linear regulator  20 , a first current sensing unit  21 , a switching regulator  30 , a second current sensing unit  31  and a hybrid output stage  40 . The microcontroller  10  is configured to perform a preset control operation such that the input power Vin is converted into the output power Vout supplied to the external load RL. 
     More specifically, the linear regulator  20  provides linear regulation under control of the microcontroller  10 , thereby receiving and converting the input power Vin into a linear output power V 1 . Similarly, the switching regulator  30  performs linear regulation under control of the microcontroller  10  so as to receive and convert the input power Vin into a switching output power V 2 . The hybrid output stage  40  receives and combines the linear output power V 1  and the switching output power V 2  to generate the output power Vout. Furthermore, the hybrid output stage  40  provides a current isolation function to prevent the respective currents of the linear output power V 1  and the switching output power V 2  from interfering with each other. In other words, the current of the linear output power V 1  does not flow into the current of the switching output power V 2 , and accordingly, the current of the switching output power V 2  does not flow into the current of the linear output power V 1 . 
     Additionally, the first current sensing unit  21  and the second current sensing unit  31  respectively sense the linear output power V 1  and the switching output power V 2 , more specifically the respective loading currents of the linear output power V 1  and the switching output power V 2 . The first current sensing signal CS 1  and the second current sensing signal CS 2  are thus generated, representative of the loading state or the loading degree. 
     The microcontroller  10  receives the first current sensing signal CS 1  and the second current sensing signal CS 2  and determines the loading state is light or heavy so as to actuate (turn on) or cease (turn off) the operation of the linear regulator  20  and the switching regulator  30 . 
     In an actual operation, the microcontroller  10  may first turn on the linear regulator  20  and turn off the switching regulator  30  when the input power Vin is supplied at the very beginning. This is because the loading current is initially zero and the loading state is considered to be light. Thus, the output power Vout of the hybrid output stage  40  contains only the linear output power V 1  from the linear regulator  20 . Subsequently, as the loading state gradually reaches a stable state, the first current sensing signal CS 1  from the first current sensing unit  21  by sensing the linear output power V 1  is received by the microcontroller  10  and used to determine whether the current loading state becomes heavy, like the first current sensing signal CS 1  exceeding a preset threshold value. If the loading state is still light, the same as the original state at the beginning, the linear regulator  20  is kept turned on and the switching regulator  30  is turned off. IF the loading state changes from light to heavy, the switching regulator  30  is turned on and at the same time the linear regulator  20  is also turned on, and subsequently the linear regulator  20  is turned off only when the switched output power V 2  of the switching regulator  30  is stable or steady. In other words, during the transient period when the loading state becomes heavy from light and the switched output power V 2  is not stable, the linear regulator  20  and the switching regulator  30  concurrently operate to provide the linear output power V 1  and the switched output power V 2 , respectively. 
     Accordingly, the microcontroller  10  may determine whether the loading state is kept heavy based on the second current sensing signal CS 2  from the second current sensing unit  31 . If the loading state is heavy, the switching regulator  30  is kept turned on and the linear regulator  20  is turned off. When the loading state changes from heavy to light, the microcontroller  10  first turns on the linear regulator  20  and the operation of the switching regulator  30  is still kept working. Only when the linear output power V 1  becomes steady or stable, the switching regulator  30  is turned off. That is, during the transient period when the loading state changes from heavy to light and the linear output power V 1  is not steady, the linear regulator  20  and the switching regulator  30  operate together. 
     Therefore, whether the loading state changes from light to heavy or from heavy to light, the respective normal regulations of the linear regulator  20  and the switching regulator  30  overlap during the transient period so as to fulfill the object of seamless switching, thereby greatly improving stability of the output power Vout. 
     More specifically, the microcontroller  10  performs a control operation consisting of specific steps, which will be described in detail as below. First, when the input power Vin begins to supply, the linear regulator  20  is turned on and the switching regulator  30  is turned off. Next, enter a sensing and determining step for receiving the first and second sensing signals CS 1  and CS 2  and further determining the loading states of the linear output power V 1  and the switching output power V 2  based on the first and second sensing signals CS 1  and CS 2 . More specifically, if the loading state of the linear output power V 1  is still light, the current situation is maintained, including the linear regulator  20  turned on and the switching regulator  30  turned off. If the loading state of the linear output power V 1  changes from light to heavy, the switching regulator  30  is turned on, and subsequently only when the switching output power V 2  of the switching regulator  30  becomes stable or steady, the linear regulator  20  is turned off. Then, if the loading state of the switching output power V 2  is still heavy, the linear regulator  20  is kept turned off and the switching regulator  30  turned on. When the loading state of the switching output power V 2  changes from heavy to light, the linear regulator  20  is immediately turned on with the switching regulator  30  still turned on. Next, the switching regulator  30  is turned off only when the linear output power V 1  of the linear regulator  20  becomes stable or steady. Subsequently, return back to the sensing and determining step and repeat the operations as mentioned above. 
     Please further refer to  FIGS. 2 ,  3  and  4 .  FIG. 2  shows an illustrative circuit of the linear regulator  20  and the first current sensing unit  21  of the present invention,  FIG. 3  illustrates an exemplary circuit of the switching regulator  30  and the second current sensing unit  31  of the present invention, and  FIG. 4  is an illustrative circuit of the hybrid output stage  40  of the present invention. It should be noted that the circuits shown in  FIGS. 2 ,  3  and  4  are typical examples of the present invention and only intended to clearly and practically explain the features of the hybrid power supply architecture according to the present invention. That is, the scope of the present invention is not limited by the above illustrative examples, and the specific electronic components in  FIGS. 2 ,  3  and  4  may substantially include other elements or devices having equivalent electrical functions. 
     As shown in  FIG. 2 , the linear regulator  20  comprises a first buffer BUF 1 , a pull-up resistor R 11 , a pull-down resistor R 12 , an operational amplifier OP and a first transistor MOS 1 , and the first current sensing unit  21  comprises a first operational amplifier OPS 1  and a first sensing resistor RS 1 . 
     The first buffer BUF 1  receives the first enable signal EN 1  from the microcontroller  10 , and generates and transmits a buffered output signal to a non-inverse input port of the operational amplifier OP so as to turn on the linear regulator  20  for linear regulation. The non-inverse input port is further connected to the pull-up resistor R 11  and the pull-down resistor R 12  to perform a clamping effect, thereby preventing the buffered output signal of the first buffer BUF 1  from being too high or too low. As a result, the operational amplifier OP is well protected. Additionally, an inverse input port of the operational amplifier OP is connected to the linear output power V 1  and generates a first control signal fed to a gate of the first transistor MOS 1  for controlling the first transistor MOS 1  to turn on or off. A source of the first transistor MOS 1  generates a first notice signal PG 1 . 
     The first sensing resistor RS 1  is connected between the input power Vin and a drain of the first transistor MOS 1 , and further connected to a non-inverse input port and an inverse input port of the first operational amplifier OPS 1  such that the voltage of the first sensing resistor RS 1  is amplified by the first operational amplifier OPS 1  and the first current sensing signal CS 1  is generated by an output port of the first operational amplifier OPS 1 . 
     As shown in  FIG. 3 , the switching regulator  30  generally comprises a second buffer BUF 2 , a pull-up resistor R 2 , a Pulse Width Modulation (PWM) controller  32 , an another pull-up resistor R 3 , a second transistor MOS 2  and a third transistor MOS 3 , and the second current sensing unit  31  comprises a second operational amplifier OPS 2  and a second sensing resistor RS 2 . 
     The second buffer BUF 2  of the switching regulator  30  is configured to receive the second enable signal EN 2  from the microcontroller  10  and generates and transmits a buffered output signal corresponding to the second enable signal EN 2  to the PWM controller  32  so as to turn on the PWM controller  32  for performing a switching regulation function. At the same time, the PWM controller  32  receives the switching output power V 2  and generates a second notice signal PG 2  indicating that the switching output power V 2  is stable. The second notice signal is further transmitted to the microcontroller. Moreover, the PWM controller  32  generates two PWM signals according to the switching output power V 2  for driving a gate of the second transistor MOS 2  and a gate of the third transistor MOS 3 , respectively. A source of the second transistor MOS 2  is connected to a drain of the third transistor MOS 3 , and a source of the third transistor MOS 3  is grounded. 
     Specifically, the second sensing resistor RS 2  of the second current sensing unit  31  is connected between the input power Vin and a drain of the second transistor MOS 2  and further connected to a non-inverse input port and an inverse input port of the second operational amplifier POS 2 , and an output port of the second operational amplifier OPS 2  generates the second current sensing signal, CS 2 . 
     As shown in  FIG. 4 , the hybrid output stage  40  comprises a first diode D 1 , a choke coil LCH and a second diode D 2 . A positive end of the first diode D 1  is connected to the first notice signal PG 1 , a negative end of the first diode D 1  is connected to the linear output power V 1 . One end of the choke coil LCH is connected to the switching output power V 2 , another end of the choke coil LCH is connected to a positive end of the second diode D 2 , and a negative end of the second diode D 2  is connected to the linear output power V 1 . Therefore, the current of the linear output power V 1  and the switching output power V 2  are electrically isolated with by the second diode D 2  with rectification, thereby achieving the object of preventing the respective currents from interfering with other. 
     From the above mentioned, one aspect of the present invention is that the microcontroller dynamically turns on/off the linear regulator and/or the switching regulator to actuate/cease regulation based on the loading state. In particular, the linear regulator and the switching regulator can perform linear regulation and switching regulation for light and heavy loading, respectively, thereby greatly increasing the overall efficiency of power conversion. 
     Another aspect of the present invention is that the linear regulator and the switching regulator operate together during the transient period when the loading state changes from light to heavy or from heavy to light. The linear regulator is turned off only when the loading state is heavy and the switching output power becomes stable or steady. Similarly, the switching regulator is turned off only when the loading state is light and the linear output power is stable or steady. Therefore, the output power is firmly stabilized so as to fulfill the purpose of power supply with seamless switching. 
     Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.