Abstract:
A power supply circuit includes a power output port, an operational amplifier, a voltage adjusting circuit, a feedback circuit, and a current controlling circuit. The power output port connects with an electronic device under test and provides a power supply which in all respects simulates the behavior of a battery being discharged as it supplies working power, the circuit also mimics the behavior of a battery in testing the battery-recharging abilities of the electronic device.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to circuits, and particularly to a power supply circuit for simulating battery function. 
         [0003]    2.Description of Related Art 
         [0004]    Electronic devices, such as mobile phones and tablet computers usually include a number of functioning parts, such as a processor, a display, and software applications, and a battery to power these functioning parts. Usually, in order to guarantee the quality of the functioning parts, tests for the functioning parts are needed before the devices leaving the factory. However, during testing the functioning parts, a battery powering the functioning parts will be discharged and recharged quite a few times, which decreases the life of the battery. 
         [0005]    A power supply circuit to overcome the described limitations is thus needed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Many aspects of the present disclosure are better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
           [0007]      FIG. 1  is a block diagram of one embodiment of a power supply circuit to simulate battery power. 
           [0008]      FIG. 2  is a circuit diagram of one embodiment of the power supply circuit of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Embodiments of the present disclosure will be described with reference to the accompanying drawings. 
         [0010]      FIG. 1  illustrates a block diagram of a power supply circuit  1  to simulate battery power. Instead of using a battery, an electronic device  2  is powered by the power supply circuit  1  when functioning parts  200  of the electronic device  2  are being tested. 
         [0011]    The simulating circuit  1  includes a power output port Vout, an operational amplifier  10 , a voltage adjusting circuit  20 , a current controlling circuit  30 , a feedback circuit  40 , and a driving circuit  50   
         [0012]    The power output port Vout connects with the electronic device  2 . The operational amplifier  10  is connected to the voltage adjusting circuit  20 , the current controlling circuit  30 , the feedback circuit  40 , and the driving circuit  50 . 
         [0013]    The operational amplifier  10  includes a non-inverting input port  101 , an inverting input port  102 , a first output port  12 , a positive driving port V+, and a negative driving port V−. 
         [0014]    The non-inverting input port  101  is grounded. The voltage adjusting circuit  20  includes a voltage input port  201  and a voltage output port  202 . The voltage input port  201  receives a reference voltage Vref, the voltage output port  202  is connected to the inverting input port  102  of the operational amplifier  10 . The voltage adjusting circuit  20  converts the reference voltage Vref to an operational signal and provides the operational signal to the inverting input port  102  of the operational amplifier  10  via the voltage output port  202 . 
         [0015]    In the embodiment, the operational amplifier  10  outputs an electric signal according to the operational signal received by the inverting input port  102  of the operational amplifier  10 . 
         [0016]    The driving circuit  50  is connected to the positive driving port V+, the negative driving port V−, and a power voltage Vcc. The driving circuit  50  converts the power voltage Vcc to a positive voltage U+ and a negative voltage U−, and provides the positive voltage U+ and the negative voltage U− to the positive driving port V+ and the negative driving port V− respectively of the operational amplifier  10 . In the embodiment, the operational amplifier  10  is in the working state when the positive driving port V+ and the negative driving port V− respectively receive the positive voltage U+ and the negative voltage U−. In the embodiment, the driving circuit  50  is a Buck-Boost conversion circuit, the positive voltage U+ output by the driving circuit  50  is greater than the power voltage Vcc and the negative voltage U− output by the driving circuit  50  is less than the power voltage Vcc. For example, the power voltage Vcc is 5 volts, the positive voltage U+ is 10 volts, and the negative voltage U− is −5 volts. 
         [0017]    In the embodiment, the power voltage Vcc is provided by an external power source (not shown). 
         [0018]    In the embodiment, the voltage input port  201  of the voltage adjusting circuit  20  is connected to the driving circuit  50  and receives the negative voltage U− from the driving circuit  50 . The reference voltage Vref herein is the negative voltage U−. 
         [0019]    The feedback circuit  40  includes a feedback input port  401 , a feedback output port  402 , and a second output port  403 . The feedback input port  401  is electrically connected to the first output port  12  of the operational amplifier  10 . The feedback output port  402  is connected to the inverting input port  102  of the operational amplifier  10 . The feedback circuit  40  feeds back the electric signal output by the first output port  12  of the operational amplifier  10  to the inverting port  102  of the operational amplifier  10 , and then forms a degenerative circuit. The feedback circuit  40  outputs a power supply voltage Vo to the power output port Vout based on the operational signal output by the voltage adjusting circuit  20 . 
         [0020]    The current controlling circuit  30  includes a control port  301  and a transmission port  302 . The control port  301  is connected to the first output port  12 , and the transmission port  32  is electrically connected to the power output port Vout. The current controlling circuit  30  outputs a power supply current Io to the power output port Vout according to the electric signal output by the first output port  12 . In the embodiment, the power supply current Io provided to the output port Vout is not greater than a predetermined value due to the controlling carried out by the current controlling circuit  30 . 
         [0021]    Therefore, The feedback circuit  40  outputs the power supply voltage Vo and the current controlling circuit  30  outputs the power supply current Io to the power output port Vout, and then powers the functioning parts  200  of the electronic device  2 . The power supply circuit  1  thus simulates a battery for powering the functioning parts  200  of the electronic device  2 . 
         [0022]    In the embodiment, the power supply circuit  1  also includes a protection circuit  60 . The protection circuit  60  is connected between the feedback circuit  40  and the power output port Vout, and is also connected between the current controlling circuit  30  and the power output port Vout. 
         [0023]    The protection circuit  60  includes a voltage driving port  601 , a first conduction port  602 , and a second conduction port  603 . The voltage driving port  601  is electrically connected to the power voltage Vcc. The first conduction port  602  is connected to the second output port  403  of the feedback circuit  40  and the transmission port  302  of the current controlling circuit  30 . The second conduction port  603  is electrically connected to the power output port Vout. The protection circuit  60  is used to establish a connection between the first conduction port  602  and the second conduction port  603 , or cut off the connection between the first conduction port  602  and the second conduction port  603 , according to state of the power voltage Vcc. 
         [0024]    In detail, when the state of the power voltage Vcc is abnormal, such as the power voltage Vcc exceeding an allowable value, the protection circuit  60  cuts off the connection between the first conduction port  602  and the second conduction port  603 , and thus cuts off connection between the second output port  403 , the transmission port  302 , and the power output port Vout. The power supply circuit  1  stops outputting the power supply voltage Vo and the power supply current Io via the power output port Vout. When the state of the power voltage Vcc is normal, the protection circuit  60  establishes the connection between the first conduction port  602  and the second conduction port  603 , and thus establishes the connection between the second output port  403 , the transmission port  302 , and the power output port Vout. The power supply circuit  1  outputs the power supply voltage Vo and the power supply current Io to the power output port Vout, and then powers the functioning parts  200  of the electronic device  2 . 
         [0025]    Referring also to  FIG. 2 , in the embodiment, the voltage adjusting circuit  20  includes a voltage regulator diode  21 , a first voltage-dividing resistor  22 , a second voltage-dividing resistor  23 , and an input resistor  24 . A cathode of the voltage regulator diode  21  is grounded, an anode of the voltage regulator diode  21  is electrically connected to the voltage output port  202  via the second voltage-dividing resistor  23  and the input resistor  24 . The first voltage-dividing resistor  22  is connected between the anode of the voltage regulator diode  21  and the voltage input port  201 . In another embodiment, the second voltage-dividing resistor  23  and the input resistor  24  can be replaced by a single resistor. 
         [0026]    The feedback circuit  40  includes a first feedback resistor  411 , a second feedback resistor  412 , and a third feedback resistor  413 . A connection node P 1  of the first feedback resistor  411  and the second feedback resistor  412  constitutes the second output port  403 , and a voltage of the connection node P 1  is the power supply voltage Vo provided to the power output port Vout. The third feedback resistor  413  is connected between the second output port  403  and ground. 
         [0027]    The feedback circuit  40  also includes a high frequency restraining circuit  420 . The high frequency restraining circuit  420  is connected between the feedback input port  401  and the feedback output port  402 , and restrains self-excited high frequency signals of the feedback input port  401  and the feedback output port  402 . In the embodiment, the high frequency restraining circuit  420  includes a high frequency restraining capacitor C, and the high frequency restraining capacitor C is connected between the feedback input port  401  and the feedback output port  402 . In the embodiment, the level of the capacitance value of the high frequency restraining capacitor C is in picofards (PF). 
         [0028]    The current controlling circuit  30  also includes a first switch unit  31  and a second switch unit  32 . The first switch unit  31  and the second switch unit  32  are electrically connected between the control port  301  and the transmission port  302 . The control port  301  controls the first switch unit  31  and the second switch unit  32  to turn on or turn off. In detail, the control port  301  controls the first switch unit  31  to turn on and controls the second switch unit  32  to turn off at the same time. At this time, the first switch unit  31  outputs the power supply current Io to the transmission port  302 . The control port  301  also controls the first switch unit  31  to turn off and controls the second switch unit  32  to turn on at the same time. At this time, any current flowing through the transmission port  302  is discharged to ground via the turned on second switch unit  32 . 
         [0029]    In the embodiment, the first switch unit  31  includes a first control terminal  310 , a first input terminal  311 , and a first output terminal  312 . The first control terminal  310  is electrically connected to the control port  301 , the first input terminal  311  is connected to the power voltage Vcc, and the first output terminal  312  is electrically connected to the transmission port  302 . 
         [0030]    The second switch unit  32  includes a second control terminal  320 , a second input terminal  321 , and a second output terminal  322 . The second control terminal  320  is electrically connected to the control port  301 , the second input terminal  321  is electrically connected to the transmission port  302 , and the second output terminal  322  is grounded. 
         [0031]    In the embodiment, the first switch unit  31  is an N-channel metal oxide semiconductor Field Effect Transistor (NMOSFET) Q 1 . A gate, a source, and a drain of the NMOSFET Q 1  respectively constitute the first control terminal  310 , the first input terminal  311 , and the first output terminal  312  of the first switch unit  31 . The second switch unit  32  is a P-channel metal oxide semiconductor Field Effect Transistor (PMOSFET) Q 2 . A gate, a source, and a drain of the PMOSFET Q 2  respectively constitute the second control terminal  320 , the second input terminal  321 , and the second output terminal  322  of the second switch unit  32 . A current flowing through the drains of the NMOSFET Q 1  and the PMOSFET Q 2  is the current flowing through the transmission port  302 . The current able to flow through the drains of the NMOSFET Q 1  and the PMOSFET Q 2  is limited to a predetermined value, thus the current flowing through the transmission port  302  is also limited to the predetermined value. 
         [0032]    When the functioning parts  200  of the electronic device  2  are being tested, the power output port Vout of the power supply circuit  1  is connected to the electronic device  2  and the power supply circuit  1  is in the working state to provide power to the functioning parts  200  of the electronic device  2 . 
         [0033]    The driving circuit  50  converts the power voltage Vcc to the positive voltage U+ and the negative voltage U−, and respectively outputs the positive voltage U+ and the negative voltage U− to the positive driving port V+ and the negative driving port V− of the operational amplifier  10 . Thus, the operational amplifier  10  is driven to work. 
         [0034]    The voltage adjusting circuit  20  receives the negative voltage U− from the driving circuit  50  via the power input port  201 . The negative voltage U− is divided via the first voltage-dividing resistor  22 , the second voltage-dividing resistor  23 , and the input resistor  24 . In the embodiment, the voltage regulator diode  21  regulates a voltage of a connection node P 2  between the first voltage-dividing resistor  22  and the second voltage-dividing resistor  23  to a regulated voltage U 2 . The voltage of the connection node P 2  is negative. Assuming that resistance values of the second voltage-dividing resistor  23  and the input resistor  24  are respectively R 1  and R 2 , then the current output via the voltage output port  202  is U 2 /(R 1 +R 2 ). 
         [0035]    Based on a virtual short principle and virtual open principle of the operational amplifier  10 , a current flowing through the feedback output port  402  and the first feedback resistor  411  is equal to the current output via the voltage output port  202 . That is, the current flowing through the feedback output port  402  and the first feedback resistor  411  also is U 2 /(R 1 +R 2 ). Assuming a resistance value of the first feedback resistor  411  is Rf, then the voltage of the second output port  403  is U 2 *Rf/R 1 +R 2 . 
         [0036]    Therefore, because the negative voltage U− is divided via the first voltage-dividing resistor  22 , the second voltage-dividing resistor  23 , and the input resistor  24 , the voltage of the inverting input port  102  connected to the input resistor  24  is also negative. Thus, the voltage of the inverting input port  102  is less than the voltage of the non-inverting input port  101 , and the first output port  12  of the operational amplifier  10  outputs a digital high signal. 
         [0037]    The NMOSFET Q 1  is turned on when the gate of the NMOSFET Q 1  receives the digital high signal. The PMOSFET Q 2  is turned off when the gate of the PMOSFET Q 2  receives the digital high signal. 
         [0038]    The protection circuit  60  establishes the connection between the first conduction port  602  and the second conduction port  603  when the power voltage Vcc is normal. Thus, the voltage output by the second output port  403  and the current output by the transmission port  302  are provided to the functioning parts  200  of the electronic device  2  via the power output port Vout. Therefore, in providing power, the power supply circuit  1  simulates a discharging process of a battery. 
         [0039]    When the power output port Vout provides a voltage higher than the voltage output by the second output port  403 , or provides a current higher than the current output by the transmission port  302 , the power supply circuit  1  is charged. In detail, the power output port Vout provides current to the feedback circuit  40  and the current controlling circuit  30 , the inverting input port  102  is at high voltage now. At this time, the voltage of the inverting input port  102  is higher than the voltage of the non-inverting port  101 , and the operational amplifier  10  outputs a digital-low signal. 
         [0040]    Thus, the gates of the NMOSFET Q 1  and the PMOSFET Q 2  receive the digital-low signal, the first NMOSFET Q 1  is turned off accordingly and the PMOSFET Q 2  is turned on accordingly. The current input by the power output port Vout is discharged to ground via the turned on PMOSFET Q 2 . Thus, the power supply circuit  1  also simulates a battery in accepting a battery recharging process. 
         [0041]    In the embodiment, because the voltage output by the second output port  403  is U 2 *Rf/R 1 +R 2 , the voltage output by the second output port  403  can be adjusted by changing the resistance values of the second voltage-dividing resistor  23 , the input resistor  24 , or the first feedback resistor  411 . In the embodiment, through using different NMOSFET Q 1  and PMOSFET Q 2 , namely, using NMOSFET and PMOSFET with different attributes, the drain current is different and the current flowing through the power output port Vout also is different. Therefore, the power supply circuit  1  can simulate batteries with different voltages and currents. 
         [0042]    In the embodiment, when the power supply circuit  1  is working, the self-excited high frequency signals of the inverting input port  102  and the first output port  12  are restrained by the high frequency restraining capacitor C. 
         [0043]    In another embodiment, when the power supply circuit  1  only needs to simulate the process of a battery being discharged as power is provided, the second switch unit  32  can be omitted. Obviously, when the power voltage Vcc is stable, the protection circuit  60  also can be omitted. 
         [0044]    It is understood that the present embodiments and their advantages will be understood from the foregoing description, and various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being exemplary embodiments of the present disclosure.