Patent Publication Number: US-2021172984-A1

Title: Tracking energy consumption using a buck-boosting technique

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/483,625, filed Apr. 10, 2017, which is a continuation of U.S. patent application Ser. No. 13/940,765, filed Jul. 12, 2013, now U.S. Pat. No. 9,618,545, each of which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an electronic device and a method for tracking the energy consumption, and more specifically to an electronic device and a method for determining energy consumption using the principle of storing energy in an inductor and transferring the energy into output energy storing components. 
     The present application relates to jointly owned U.S. Patent Application corresponding to application Ser. No. 13/329,073 entitled, “Electronic Device and Method for Power Measurement.” 
     BACKGROUND 
     Reducing energy consumption is important in the development and improvement of electronic devices, in particular if they are mobile or portable electronic devices. In order to save energy, electronic devices are more and more controlled by sophisticated schemes in which the magnitude of the consumed currents varies over several decades of magnitude. In low power modes some hundreds of nA (nano-amperes) of a current may be consumed while other operation modes require up to several hundreds of mA (milli-amperes). It is often necessary to measure these currents over a wide range (e.g. from nano-amperes to milli-amperes) with an acceptable accuracy while at the same time being able to track highly dynamic current changes. Furthermore, any side effects due to measuring the consumed energy should be avoided or well controlled. For example, it is preferred that an increase of the energy consumption due to the energy measurement itself not occur. 
     One of the more common techniques for measuring a current is a measurement using a shunt device or a shunt resister. Using a shunt device for the power measurement requires very high precision analogue to digital converters in order to cover the full dynamic range of the possible magnitudes of the currents. For example, when four and a half decades of measurement with one percent precision is required, a 24-Bit-converter would be required. Furthermore, shunt devices generate a voltage drop. This voltage should be compensated, while the compensation circuitry constitutes a potential source of errors. Direct load compensation can be difficult. This means that the measurement range and therefore the circuitry used for measuring the power consumption has to be adapted during the energy measurement procedure. This increases complexity and entails more potential errors. 
     Still further, measuring a current indirectly by measuring the voltage across a shunt device requires an initial voltage change on the target. If a buffer capacitor is coupled to the target side (output side of an energy transfer circuits), the buffer capacitor delivers current immediately and needs to be recharged. This behavior affects the true current response of the device under test. Another approach of measuring the energy consumption employs a current mirror. One side of the current mirror delivers the current to the target including the target capacitor. The other side of the current mirror is coupled to an Ampere meter to which the mirrored current is fed. This approach has the advantage that the distortion caused by the target capacitor is minimized. However, the required pairing of the power and sense field effect transistors (FET) is rather poor and is not capable of tracking the huge current magnitude to be supported. 
     SUMMARY 
     It is an object of the invention to provide an electronic device  200  and a method for measuring energy consumption in an energy consuming system that covers a large range of magnitudes of supply currents, high dynamic current changes and does not affect the basic functionality of the circuit which energy consumption is measured. According to an aspect of the invention, an electronic device  200  is provided that comprises switched mode energy tracking circuitry. The switched mode circuitry comprises one or more switching elements SWA-SWB, SW 1   a -SW 1   b  and SWia-SWib, one or more in inductors, LA-Li, a capacitor CA and compare circuits  406  and  434  that control the output voltage level VO and the output voltage level V 1  respectively. The switching elements, SWA-SWia, are configured to switch current through the inductors LA-Li respectively. The switches, SWA-SWB, SW 1   a -SW 1   ia  and SW 1   b -SW 1   ib , may be transistors. The voltage compare circuits  406  and  434  may be error amplifiers, a voltage comparators, or an A/D converters which conversion result is compared to a reference voltage VL(ref). The ON/OFF generator  408  is configured to control the ON-time and OFF-time of the switching elements, SW 1   a -SW 1   ia  and SW 1   b -SW 1   ib , in order to transfer energy from a primary energy source, e.g. power supply, to the output VO of the energy tracking system and to control the level of the output voltage VO. The electronic device  200  further comprises control logic stages CNTLA, CNTL 1  and CTNLi. A control block  410  comprises an error handling block  420 , reporting block  416 , a calibration block  412 , an accumulator  414  of the individual ON-time events, a sequencing block  422 , a range control block  418  and a demand control block  424 . 
     The control logic stages CTNLA-CNTLi generate the switching signals SWSA, SWS 1   a  to SWSib for the switched transistors, SWA-SWB, SW 1   a -SW 1   ia  and SW 1   b -SW 1   ib , in the form of ON-time pulses and with a constant width ON-time for SW 1   a -SWia. The control logic stages, CTNLA-CNTLi, also control the OFF-time which is used also as an indicator of the energy in the inductors that is transferred to the output VO. The voltage-compare circuits  406  and  432  flag when the next ON-time pulse has to be generated. If the OFF-time is not over before the next ON-time is triggered, the system reports an error condition. An error condition is also reported if the output voltage VL is not within predefined limits. 
     The switching signals, SWS 1   a  to SWSib, are formed according to a pulse density scheme. The highest density of pulses occurs when the ON-time and OFF-time are met at the time another ON-time is requested. Higher density is enabled by default or by control information (e.g. a control bit and this is handled by the control circuit as described previously). In an embodiment of the invention, the pulse accumulator  414  can be in the simplest implementation a digital counter. The counter in this embodiment is then configured to count the number of ON-time pulses for determining the consumed power based on the number of ON-time pulses per time. The constant pulse width of the ON-time pulses makes the influence of the system components such as the non-linear behavior of switched transistors or inductors negligible. The target voltage offset at the output of the energy tracking system is highly reduced. A wide range of magnitudes of the measured current can be covered. 
     According to another aspect of the invention, the electronic device comprises a first capacitor C 1  coupled to the input of the energy tracking system, a second capacitor CA at the input of the energy tracking blocks  204  and  206  and a third capacitor C 2  coupled to the output of the energy tracking system. The ON-time of the switching element in conjunction with the inductor&#39;s L 1  value and the value of the capacitor CA is configured to keep the voltage within the system accuracy requirements. The output capacitor C 2  is of such value that the voltage increase during transferring the energy from the inductor L 1  to Li is within the accuracy expectations. 
     The energy tracking system of this embodiment is contrary to a pulse width modulation scheme and nearly all energy in the inductors, L 1 -Li can be transferred to capacitor C 2 . The frequency of the ON-time pulses is proportional to and practically a linear function of the consumed current. During a settled operation condition, in which the input and output voltages and the charges on the input and output capacitors have settled, each ON-time pulse of the switched transfers about the same amount of energy. 
     According to another embodiment of the invention, a reference impedance  205  or a reference resistor R can be coupled to the output of the energy tracking system in order to make a reference energy measurement. The results of the reference measurement(s) can then be used for calibrating the system to the energy consumption. Therefore, the number of the ON-time pulses can be used for determining the energy consumption during normal operation even with an unknown load (e.g. C 3  &amp; Z). The unknown load according to an embodiment of the invention can be an electronic device. 
     In an embodiment of the invention, the electronic device  200  comprises an energy tracking system with switching components SWA-SWB, SW 1   a -SW 1   ia  and SW 1   b -SW 1   ib , inductors LA, L 1 , Li, transfer support diodes DA-Di. The switching components SWA-SW 1   ia  can then be configured to enable current through the inductors LA-Li respectively. The optional switches SWB-SWib may be used to conduct current during the OFF-time to support the transfer of energy from an inductor to the output. The optional switch SWB does not conduct energy after the energy transfer is completed preventing that energy from flowing back from the output to the input. The optional switches SW 1   b -SWib do not conduct energy after the energy transfer is completed preventing that energy from flowing from the output to input respectively capacitor CA. The voltage compare circuits  406  and  434  can be error comparators or error amplifiers. The voltage compare circuit  406  is configured to send a signal  426  to the control circuit  410  and the ON/OFF generator  408  so that the switching components SW 1   a -SW 1   ia  and SW 1   b -SW 1   ib  can be triggered or be prepared to be triggered. The compare circuits  406  and  434  serve to deliver the demand on energy to maintain a stable output voltage VO and V 1  respectively. The generation and frequency of the ON-time pulses can be controlled in response to a change of the output voltages VO. The ON-time pulses can be combined with a time stamp on an individual basis or on a group of pulses. 
     Another embodiment of the invention includes ON-time pulses that are based on a defined time and the difference to that defined time base is bounded by pulses or a group of pulses. The energy consumption may then be determined based on the number of the ON-time pulses per considered time period. 
     In an aspect of the invention, the energy consumption may then be derived from a phase variation of the ON-time pulses. This aspect allows a quick evaluation of changes of the power consumption. The energy transfer during ON-time pulses usually is significantly smaller than the energy stored on a second capacitor CA coupled to the input of the energy transfer system. The energy withdrawn from the energy source at the input of the energy transfer system influences the energy transferred during the ON-time. The influence of the energy sourcing capability is a factor in the calibration cycle. 
     The energy stored on a second capacitor C 2  coupled to the output of the energy transfer system is also significantly larger than the energy stored in the inductor during the ON-time and transferred to the output and the capacitor C 2  during OFF-time. The energy consumption may be calibrated by coupling one or more reference impedances  205  to the output of the energy transfer system. The result of the calibration may then be used for normalizing the energy consumption during normal operation. During normal operation a target device or a device under test (DUT)  208  is then coupled to the output of the energy transfer system instead of the reference impedance  205 . However, in another embodiment, the reference impedance  205  may be coupled to the output while the target load device or DUT  208  is still coupled to the output. The energy of one or a group of ON-time pulses due to the additional load of the reference load can be evaluated for calibrating the power measurement based on the energy pulse ON-time and OFF-time conditions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a circuit measuring the current, the voltage and the timing relations to calculate the energy consumed within the load of the device-under-test. (Prior Art) 
         FIG. 2 a    is a simplified circuit diagram of an embodiment of the invention. 
         FIG. 2 b    is a simplified circuit diagram of an embodiment of the invention. 
         FIG. 3  is a diagram showing waveforms of signals of the circuit shown in  FIG. 2 a    according to an embodiment of the invention. 
         FIG. 4  is a circuit diagram of an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
       FIG. 1  shows a circuit  101  that measures the load current via a voltage-to-voltage converter  102 , an A/D converter  104  and timer  106 . The energy EL used by the load is calculated in block EL  108 . The voltage VL is measured via the A/D converter  104 . When the A/D converter  104  is used for sequential conversions, phase related errors may occur. A timer  106  is used to create the time base t(b) for the A/D converter  104 . The energy EL used by the load (i.e. DUT) is calculated by the block EL according to equation 1 below. 
         ELx=IL*VL*t ( b ) where  x={ 1 . . .  i}   Equation 1
 
       FIG. 2 a    shows a simplified diagram of an embodiment of the invention. In this embodiment, an energy tracking system  200  comprises energy transfer blocks  202 ,  204 ,  206 , a control circuit  201  and reference impedance  205 . In this embodiment of the invention, energy transfer block  202  is a “buck” circuit that comprises switched transistors SWA and SWB, diode DA, capacitor CA and inductor LA. In this embodiment of the invention, energy transfer blocks  204  and  206  are “boost” circuits. Energy transfer block  204  comprises switched transistors SW 1   a  and SW 1   b , diode D 1 , and inductor L 1 . Energy transfer block  206  comprises switched transistors SWia and SWib, diode Di, and inductor Li. In this example two boost energy transfer blocks  204  and  206  are shown. However, more than two boost energy transfer blocks may be used. 
     In buck block  202 , one terminal of inductor LA is coupled to a first switched transistor SWA, a second switched transistor SWB and to the cathode of diode DA. The other terminal of the inductor LA and a terminal of the capacitor CA are coupled to the output of the energy transfer block  202 . The input of the energy transfer block  202  is coupled to the first switched transistor SWA. The anode of the diode DA, a terminal of the capacitor CA and a terminal of the second switched transistor SWB are connected to ground. The switched transistors SWA and SWB can be referred to as energizing switches. The diode DA may be replaced or complemented by the second switch SWB. The control circuit  201  controls the energy switches SWSA and SWSB. A function of boost block  202  is to transfer or “boost” the voltage on the input to a higher voltage level in order to have enough voltage margin for energy tracking blocks  204  and  206 . The control circuit  201  will be explained in more detail later in the specification. 
     In boost energy transfer block  204 , one terminal of inductor L 1  is coupled to a first switched transistor SW 1   a , a second switched transistor SW 1   b  and to the anode of diode D 1 . The other terminal of the inductor L 1  is coupled to the input of the energy transfer block  204 . The cathode of the diode D 1  and a terminal of the second switched transistor SW 1   b  are connected to the output of the energy transfer block  204 . The switched transistors SW 1   a  and SW 1   b  can be referred to as energizing switches. The diode D 1  may be replaced or complemented by the second switch SW 1   b . The control circuit  201  controls the energy switches SWS 1   a  and SWS 1   b . The control circuit  201  will be explained in more detail later in the specification. 
     In boost energy transfer block  206 , one terminal of inductor Li is coupled to a first switched transistor SWia, a second switched transistor SWib and to the anode of diode Di. The other terminal of the inductor Li is coupled to the input of the energy transfer block  206 . The cathode of the diode Di and a terminal of the second switched transistor SWib are connected to the output of the energy transfer block  206 . The switched transistors SWia and SWib can be referred to as energizing switches. The diode Di may be replaced or complemented by the second switch SWib. The control circuit  201  controls the energy switches SWSia and SWSib. The control circuit  201  will be explained in more detail later in the specification. 
       FIG. 2 b    shows a simplified diagram of an embodiment of the invention. In this embodiment, an energy tracking system  200  comprises energy transfer blocks  209 ,  211 , a control circuit  201  and reference impedance  205 . In this embodiment of the invention, energy transfer blocks  209  and  211  are “buck-boost” circuits. In this example two buck-boost energy transfer blocks  209  and  211  are shown. However, more than two buck-boost energy transfer blocks may be used. 
     In buck-boost energy transfer block  209 , one terminal of inductor L 1   a  is coupled to a first switched transistor SW 1   a , a second switched transistor SW 1   b  and to the cathode of diode D 1   a . A terminal of the first switched transistor SW 1   a  is coupled to an input of the energy transfer block  209 . The anode of the diode D 1   a , a terminal of the capacitor C 1   a , a terminal of the second switched transistor SW 1   b  and a terminal of the third switched transistor SW 1   c  are connected to ground. A terminal of the capacitor C 1   a , a terminal of the inductor L 1   a  and a terminal of the inductor L 1   b  are connected together. A terminal of inductor L 1   b  is coupled to a terminal of the third switched transistor SW 1   c , a terminal of the fourth switched transistor SW 1   d  and to the anode of diode D 1   b . The cathode of diode D 1   b  and a terminal of switched transistor SW 1   c  are connected to the output of the energy transfer block  209 . The switched transistors SWS 1   a , SWS 1   b , SWS 1   ic  and SWS 1   d  can be referred to as energizing switches. The diode D 1   a  may be replaced or complemented by the second switch SW 1   b . The diode D 1   b  may be replaced or complemented by the fourth switch SW 1   d . The control circuit  201  controls the energy switches SWS 1   a , SWS 1   b , SWS 1   c  and SWS 1   d . The control circuit  201  will be explained in more detail later in the specification. 
     In buck-boost energy transfer block  211 , one terminal of inductor Lia is coupled to a first switched transistor SWia, a second switched transistor SWib and to the cathode of diode Dia. A terminal of the first switched transistor SWia is coupled to an input of the energy transfer block  211 . The anode of the diode Dia, a terminal of the capacitor Cia, a terminal of the second switched transistor SWib and a terminal of the third switched transistor SWic are connected to ground. A terminal of the capacitor Cia, a terminal of the inductor Lia and a terminal of the inductor Lib are connected together. A terminal of inductor Lib is coupled to a terminal of the third switched transistor SWic, a terminal of the fourth switched transistor SWid and to the anode of diode Dib. The cathode of diode Dib and a terminal of switched transistor SWic are connected to the output of the energy transfer block  211 . The switched transistors SWSia, SWSib, SWSic and SWSid can be referred to as energizing switches. The diode Dia may be replaced or complemented by the second switch SWib. The diode Dib may be replaced or complemented by the fourth switch SWid. The control circuit  201  controls the energy switches SWSia, SWSib, SWSic and SWSid. The control circuit  201  will be explained in more detail later in the specification. 
       FIG. 3  shows the timing diagram for an energy transfer circuit (shown in  FIG. 2 a   ) that has two transfer paths. The first path has SW 1   a , L 1 , D 1 , and the ON-time signal SWS 1   a  applied to SW 1   a . The switch SW 1   b  shown in energy transfer block  204 , in this example, is not used. The second path has SWia, Li, Di, and the ON-time signal SWSia applied to SWia. The switch SWSib shown in energy transfer block  206 , in this example, is not used. The two energy transfer paths are used mainly to enhance the dynamic range of delivering energy. The optional switches SW 1   b  and SWib may be used to conduct current during the OFF-time to support the transfer of energy from the inductors to the output. The optional switches SW 1   b  and SWib do not conduct energy after the energy transfer is completed preventing that energy from flowing back from the output to the input. The system may have more than 2 paths enabling further spread of the dynamic range of the energy tracking circuits. 
       FIG. 4  shows more detail in the control circuit  201 . The compare circuits  406  and  434  are coupled to receive a reference signal VL(ref) that is used to determine the output voltages VL and V 1 . The output of the compare circuits  406  and  434  are coupled to the control logic stages CNTLA  432 , CNTL 1   402  and CNTLi  404 . The ON-time and OFF-time generator  408  is coupled to feed the ON-time signals TG 1  and TGi to the control logic CNTL 1  and CNTLi respectively. The control logic stage CNTLA provides switching signals SWSA and SWSB for switching the switching element SWA and SWB to generate the voltage V 1 . The control logic stage CNTL 1  provides switching signals SWS 1   a  and SWS 1   b  with constant width ON-time pulses for switching the switching element SW 1   a  and SW 1   b . The control logic stage CNTLi provides switching signals SWS 1   ia  and SWSib with constant width ON-time pulses for switching the switching element SWia and SWib. 
     Issuing the next ON-time pulses is a function of the output signal  426  of the compare circuit  406  and the ON/OFF-time. The constant width ON-time is generated in this embodiment from constant clock CLK (e.g. from a crystal oscillator). Such an implementation eases the calibration situation since the ON-time is nearly independent of the voltage and temperature conditions. The primary side of the energy tracking system is coupled to a first capacitor C 1 . Accordingly, one side of the inductor LA is coupled to one side of the first capacitor CA. The other side of the first capacitor CA is coupled to ground. The primary side of the energy tracking system  204  and  206  is supplied by a stable supply realized by the circuit  202 . The output or secondary side of the energy tracking system is coupled to a second capacitor C 2  for buffering the output voltage VO. A target board or device under test  208  can be coupled to the output of the energy tracking system. The current consumed by the target board or device under test is the load current IL. The level of the output voltage is VO. 
     One or more reference impedances  205  in the form of reference resistor R and a switch LS can be coupled through switch LS to the energy tracking system. Instead of the target board the reference resistor R can be switched to the output VO. However, the target board or DUT may still be coupled to the output during the reference measurement. The result of the reference measurement with the well characterized reference resistor R can then be used to calibrate the measurement for the operation with the unknown load (e.g. C 3  &amp; Z) of the target board  208 . The energy transferred through the switched transistors SW 1   a  and SWib during an ON-time pulse is usually much smaller than the stored energy in the capacitors CA and C 2 . If the energy that is transferred during an ON-time pulse is ESW, the energy on capacitor CA is ECA, the energy on capacitor C 1  is EC 1 , and the energy on capacitor C 2  is EC 2 , the following advantageous ratios are advantageous: 
         EC 1= k 1* ESWA    
     and 
         ECA=k 2*( ESW 1+ . . .  ESWi ) where  X={ 1 . . .  i}   
     and 
         EC 2= k 3*( ESW 1+ . . .  ESWi ) where  X={ 1 . . .  i}   
     with 
         k 1&gt;20, k 2 and  k 3&gt;50. 
     ESWA and the sum of ESW 1  to ESWi are much smaller than EC 1 , ECA and EC 2 . When the output voltage VO has settled, the compare block  406  measures any deviation of target output voltage VL and versus VL(ref). The control blocks CNTL 1  and CNTLi increase or decrease the density of ON-time pulses. The ON-time pulses are generated with a constant width ON-time and a minimum OFF-time. The inductors L 1 , and Li will be charged with a certain amount of energy from the second capacitor CA. During the OFF-time the energy in the inductors is transferred to the third capacitor C 2 . In an embodiment of the invention, the second capacitor CA and the third capacitor C 2  are sized such that this energy transfer does not significantly change the voltages across the second capacitor CA and the third capacitor C 2 . 
     As long as the energy in the third capacitor C 2  is sufficient to maintain the output voltage VO, the compare block will not request another ON-time pulse through switching signal SWS 1   a , SWS 1   b  or SWSia, SWSib. However, if a certain load current IL is consumed by the target board or DUT, the voltage across the second capacitor C 2  is reduced until the voltage compare block VL=VL(ref) determines that the output voltage VO at output node OUT is lower than defined and generates a request signal to CNTL 1  and CNTLi. Another ON-time pulse will then be generated. During normal operation, this causes a pulse density of ON-time pulses of signals SWS 1   a  and SWSia that is proportional to the consumed energy of the DUT/target board  208 . In another embodiment, the number of ON-time pulses per time counted by the accumulator  414  and the current data there reflects and indicates the energy consumption. Under stable input voltage conditions, each ON-time pulse represents approximately the same amount of energy that is transferred during each ON-time pulse. The OFF-time variations of the ON-time pulses of the switching signal SWSi 1  and SWSia also indicate current variations of the load currents IL. 
     A reference measurement on the known reference resistor R can be used for normalizing the measured current. The reference resistors R may be switched on through switch LS in addition to the target board  208 . The influence of the reference resistor R on the OFF-time in signals SWS 1   a  and SWSia can then be evaluated. However, the achieved result can be improved if the reference resistor R is switched on while the target board is not connected. 
       FIG. 3  shows a diagram with waveforms of the load current IL, the output voltage VO, and ON-time signals as applied to switches SW 1   a  and SWS 2   a . The load current IL of the target or DUT increases at a certain point of time. The voltage VO at the output node OUT varies according to a saw tooth scheme around the target output voltage level. The pulse density of the ON-time pulses SWS 1   a  and SWSia increases at a certain point of time or starts (SWSia) depending on the extent of the load current IL. The voltage VO varies according to a saw tooth scheme around the target output voltage level (dashed line). The pulse density of the ON-time pulses increases after the load current IL increases. This change in density of ON-time pulses of both paths is evaluated. 
     Although the invention has been described hereinabove with reference to a specific embodiments, it is not limited to these embodiment and no doubt further alternatives will occur to the skilled person that lie within the scope of the invention as claimed.