Patent Publication Number: US-8981736-B2

Title: High efficiency, thermally stable regulators and adjustable zener diodes

Description:
CLAIM OF PRIORITY 
     This patent application claims the benefit of priority, under 35 U.S.C. Section 119(e), to Dunipace, U.S. Provisional Patent Application Ser. No. 61/408,879, entitled “HIGH EFFICIENCY, THERMALLY STABLE REGULATORS AND ADJUSTABLE ZENER DIODES,” filed on Nov. 1, 2010, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Electric utilities have recently begun to monitor customer power usage using “smart” electrical meters. In addition to the overall amount of energy consumed at a location, the smart meters can monitor the quality of the energy and the particular time when the energy was used. The information can be used to more accurately bill a customer. In addition, the smart meters can transmit the energy information to a central location without the need for personnel to observe the meter. In certain examples, the smart meter may require 8 watts to transmit the energy information. When not transmitting, the smart meter may only use 0.25 watts of power. Typical power supply regulators can use 48 milliwatts (mW) or more of power. During non-transmission times, the regulator may use about 20% of the meter power. This is wasted energy. This wasted energy is characteristic of other devices that monitor conditions during standby, such as devices that can be used with a remote control. Significant energy savings can be realized with more efficient power supply regulators. 
     OVERVIEW 
     This overview is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application. 
     This document refers to, among other things, apparatus for high-efficiency, thermally-compensated regulators. In an example, a regulator can include a zener diode having a first temperature coefficient, the zener diode configured couple to an output and to provide at least a portion of a reference voltage, a transistor having a second temperature coefficient, the transistor configured to receive the reference voltage, to receive a representation of the output, and to provide feedback information indicative of an error of the output using the representation of the output voltage and the reference voltage, and wherein the first temperature coefficient and the second temperature coefficient are configured to reduce at least a portion of a temperature drift effect of the zener diode and the transistor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
         FIG. 1  illustrates generally a power supply including a high-efficiency, thermally stable regulator. 
         FIG. 2  illustrates generally an example inverting, non-isolated, high-efficiency, thermally-compensated regulator. 
         FIG. 3  illustrates generally an example isolated, high-efficiency, thermally-compensated regulator. 
         FIG. 4  illustrates generally an example high-efficiency, thermally-compensated, precision zener. 
         FIG. 5  illustrates generally an example high-efficiency, thermally-compensated, primary regulator. 
         FIG. 6  illustrates generally an example high-current shunt regulator. 
         FIG. 7  illustrates generally a thermally compensated precision current source. 
     
    
    
     DETAILED DESCRIPTION 
     Power levels for smart meters can range between 1 watt (W) and 15 W. Non-smart meters can have power levels of around 1 W. In certain examples, smart meter specifications can allow continuous transmission of energy information so the power supplies need to be dimensioned for the high power levels used during transmission. In certain examples, a smart meter can use about 0.25 watts between transmissions for housekeeping. (˜99% of the time). Power that is used by a secondary power supply regulator can significantly impact the overall efficiency of the power supply during housekeeping intervals. Traditional regulators can require 1 mA worst-case keep-alive, plus 0.5 to 1 mA for the reference divider, plus any current needed for an optical isolator if the regulator is isolated. Overall, this can amount to 48 mW. In power supplies with low power outputs such as 250 mW output this can amount to ˜19.2% power loss. 
     The present inventor has recognized, among other things, example zener-based regulators including thermal compensation based upon a thermal gradient of a transistor junction such as the base-emitter thermal gradient of a BJT transistor, to provide a high quality, thermally stable, low-current references at low power and price. Example regulators can use only a few milliwatts in certain examples and are capable of significantly improving overall efficiency of power supplies used in low power applications. 
     In certain examples, a high-efficiency regulator can use less than 6.24 mW. (At 250 mW output ˜3% loss). If 10 million smart meters are installed using a high-efficiency regulator, the power saving can be around 500,000 watts. 
       FIG. 1  illustrates generally a block diagram of a power supply  100  including an example high-efficiency regulator  101 . The power supply  100  can include a power supply controller  102 , power electronics  103 , and the regulator  101 . In certain examples, the power supply controller  102  and the power electronics  103  can include fly back topologies, buck topologies, half bridge drivers, full bridge driver, power factor correction (PFC) controllers, pulse width modulation (PWM) controllers, resonant type topologies or combinations thereof. In an example, the power supply controller  102  can include a pulse width modulated controller and the power electronics  103  can include one or more power switches, rectifiers, isolation components, or combinations thereof. The power supply  100  can receive an input voltage V IN  at the power electronics  103 . The power supply controller  102  can provide command signal to control the power electronics  103  to provide a desired output voltage V OUT  or current. In certain examples, the regulator  101  can compare the output voltage V OUT  to a reference (not shown) and can provide feedback information  104  to the power supply controller  102 . The power supply controller  102  can modify the control of the power electronics  103  to correct any output voltage or current error received in the feedback information  104 . 
       FIG. 2  illustrates generally an example inverting, non-isolated, high-efficiency, thermally-compensated regulator  201 . The regulator  201  can include a voltage divider  205  including a zener diode  206  and first and second resistors  207 ,  208 . The voltage divider  205  can be coupled to the output voltage V OUT . A bias node  209  of the voltage divider  205  can be coupled to a control node of a transistor  210 , such as, but not limited to, a base node of a bipolar junction (BJT) transistor. In certain examples, the transistor  210  can include a gain of about 400. As the output voltage V OUT  fluctuates, the impedance of the transistor  210  can vary inversely with the output voltage V OUT . In an example, the transistor  210  can provide feedback information  204  and can be coupled to a feedback input of a power supply controller to close a loop of the power supply. In certain examples, the regulator  201  can operate with nominal bias current of about 50 microamps (μA). In certain examples, the zener diode  206 , the first resistor  207 , and the second resistor  208  can be selected for a particular output voltage, V OUT . Table 1 below illustrates particular device selections for various output voltages. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Transistor 
                   
                   
                   
                   
                   
               
               
                 Zener 
                 Zener Diode 
                 210 
               
               
                 Diode 
                 206 
                 B-E 
                   
                   
                   
                   
                 Regulator 
               
               
                 206 
                 Temperature 
                 Temperature 
                   
                   
                   
                 Regulator 
                 Temperature 
               
               
                 Voltage 
                 Coefficient 
                 Coefficient 
                 First 
                 Desired 
                 Second 
                 Temperature 
                 Coefficient 
               
               
                 25° C. 
                 mV/° C. 
                 mV/° C. @ 
                 Resistor 
                 Regulator 
                 Resistor 
                 Coefficient 
                 Error 
               
               
                 @50 uA 
                 @50 uA 
                 0.5 uA 
                 207 Kohms 
                 Voltage 
                 208 Kohms 
                 mV/° C. 
                 ppm/° C. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 6.742 
                 2.855 
                 −2.18 
                 11.7 
                 8 
                 13.54 
                 −1.831 
                 −228.8 
               
               
                 8.253 
                 4.618 
                 −2.18 
                 11.7 
                 9 
                 5.72 
                 1.382 
                 153.6 
               
               
                 9.035 
                 5.500 
                 −2.18 
                 11.7 
                 10 
                 7.45 
                 1.944 
                 194.5 
               
               
                 10.068 
                 6.553 
                 −2.18 
                 11.7 
                 12 
                 30.53 
                 −1.282 
                 −106.8 
               
               
                 13.037 
                 9.500 
                 −2.18 
                 11.7 
                 15 
                 33.41 
                 1.131 
                 75.4 
               
               
                 15.814 
                 11.487 
                 −2.18 
                 11.7 
                 18 
                 35.99 
                 2.639 
                 146.6 
               
               
                 14.783 
                 10.053 
                 −2.18 
                 11.7 
                 18 
                 54.82 
                 −2.286 
                 −127.0 
               
               
                 17.926 
                 13.921 
                 −2.18 
                 11.7 
                 20 
                 38.17 
                 4.669 
                 233.5 
               
               
                 19.590 
                 15.250 
                 −2.18 
                 11.7 
                 24 
                 79.96 
                 −1.750 
                 −72.9 
               
               
                   
               
            
           
         
       
     
     In addition to providing a low power, high efficiency regulator, the example regulator  201  can also improve the temperature drift performance of a power supply. Performance of electrical components, in general, can vary as temperature of the power supply components change. The measure of the change can be represented by a temperature coefficient and the change in a device operating condition can be known as a temperature drift effect. In certain examples, the temperature coefficient of the zener diode  206  and the temperature coefficient of the base-emitter junction of the transistor  210  can be configured to reduce at least a portion of a temperature drift effect of the zener diode and the transistor as well as the combined temperature drift effect of the regulator. The example regulator of  FIG. 2  can be temperature compensated via the complimentary temperature coefficients of the zener diode  206  and the base-emitter junction of the transistor  210 . In an example, a zener diode for a 24 volt regulator can have a temperature coefficient of about 15 millivolts per degree Celsius (mV/° C.) and the temperature coefficient of the base-emitter junction of a transistor can be about −2.18 mV/° C. The temperature coefficient of the example regulator of  FIG. 1  using the zener diode and the transistor can be as low as −1.750 mV/° C. In certain examples, the thermal coefficient of the zener and the transistor junction can be selected such that the zener diode thermal coefficient is substantially equal to the transistor junction thermal coefficient times the ratio of the resistance of the second resistor  208  to the resistance of the first resistor  207 . In certain examples, the regulator can include a filter  211  to ensure regulation loop stability. In certain examples, an integrated circuit can include the transistor  210  and the zener diode  206 . The transistor  210  and the zener diode  206  can be configured to provide a thermally compensated regulator. In such an example, components external to the integrated circuit, such as the first resistor  207  and the second resistor  208 , can be selected to provide a desired output voltage, V OUT . In certain examples, the regulator  301  can regulate output current. In certain examples, an upper limit of the output voltage can be determined by the capabilities of the transistor  210 . In certain examples, a lower limit of the output voltage can be determined by the zener voltage of the zener diode  206 . In certain examples, low voltage regulator can use an light emitting diode (LED) to provide the zener voltage. For example, red LEDs can provide a zener voltage of about 1.65 volts. 
     In certain examples, the regulator  201  can recursively regulate the current that produces the voltage drop across the zener diode  206 , thus, providing additional output voltage V OUT  stability. 
       FIG. 3  illustrates generally an example isolated, high-efficiency, thermally-compensated regulator  301 . The regulator  301  can include a voltage divider  305  including first and second resistors  307 ,  308 , a bias resistor  312 , a zener diode  306 , a transistor  310 , and a feedback optical isolator  313  with a current limit resistor  314 . In certain examples, the zener diode  306  can provide a reference voltage at the emitter of the transistor  310  and the voltage divider  305  can provide a representation of the output voltage V OUT  at the control node of the of the transistor  310 . The transistor  310  can compare the values and provide feedback information  304 , including an indication of the output voltage error, using the current of the feedback optical isolator  313 . Table 2 includes example values of device characteristics of the example regulator  301  to provide regulation of various values of an output voltage V OUT . In certain examples, the output voltage V OUT  can be selected from a range including from about 8 volts to about 100 volts. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 Transitor 
                   
                   
                   
                   
                   
               
               
                 Zener 
                 Zener Diode 
                 310 
               
               
                 Diode 
                 306 
                 B-E 
               
               
                 306 
                 Temperature 
                 Temperature 
                   
                   
                   
                 Output 
                 Output 
               
               
                 Voltage 
                 Coefficient 
                 Coefficient 
                 First 
                 Second 
                   
                 Temperature 
                 Temperature 
               
               
                 25° C. 
                 mV/° C. 
                 mV/° C. @ 
                 Resistor 
                 Resistor 
                 Regulator 
                 Coefficient 
                 Coefficient 
               
               
                 @250 uA 
                 @250 uA 
                 0.5 uA 
                 307 Kohms 
                 308 Kohms 
                 Voltage 
                 mV/° C. 
                 ppm/° C. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 25.5 
                 8 
                 −0.1924 
                 −24.05 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 45.3 
                 9 
                 −0.2163 
                 −24.03 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 66.5 
                 10 
                 −0.2401 
                 −24.01 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 86.6 
                 11 
                 −0.2640 
                 −24.00 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 107.0 
                 12 
                 −0.2878 
                 −23.99 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 127.0 
                 13 
                 −0.3117 
                 −23.98 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 169.0 
                 15 
                 −0.3594 
                 −23.96 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 232.0 
                 18 
                 −0.4310 
                 −23.94 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 267.0 
                 20 
                 −0.4787 
                 −23.93 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 348.0 
                 24 
                 −0.5741 
                 −23.92 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 590.0 
                 36 
                 −0.8603 
                 −23.90 
               
               
                 6.103 
                 2.013 
                 −2.18 
                 137.0 
                 845.0 
                 48 
                 −1.1465 
                 −23.89 
               
               
                   
               
            
           
         
       
     
     In certain examples, the output voltage V OUT  can be selected, or the various values of the regulated can be selected, using the following general formula: 
                 V   OUT     =       V   REF     ⁡     (     1   +     (       R   1       R   2       )       )         ,         
where V REF  includes the voltage across the zener diode  306  and the base-emitter junction of the transistor  310 , R1 includes the value of the first resistor  307 , and R2 includes the value of the second resistor  308 .
 
     In addition to providing a low power, high efficiency regulator, the example regulator  301  can also improve the temperature drift performance of a power supply. The example regulator  301  of  FIG. 3  is temperature compensated via the complimentary temperature coefficients of the zener diode  306  and the base-emitter junction of the transistor  310 . Table 2 illustrates that with the selected zener and transistor, the output temperature coefficient error is about −24 ppm/° C. over the entire output voltage range. In certain examples, the regulator can include a filter  311  to ensure regulator stability. In certain examples, an integrated circuit can include the transistor  310  and the zener diode  306 . The transistor  310  and the zener diode  306  can be configured to provide a thermally compensated regulator. In such an example, components external to the integrated circuit, such as the first resistor  307  and the second resistor  308 , can be selected to provide a desired output voltage, V OUT . In certain examples, the regulator  301  can regulate output current. 
     In an example, such as for a 12 volt power supply, the current limit resistor  314  can be about 2.2 kohms, and the bias resistor  312  can be about 510 kohms. In such an example, the operating current of the regulator can be about 260 μA. 
       FIG. 4  illustrates generally an example thermally-compensated precision zener diode  420 . The thermally-compensated precision zener diode  420  can include a voltage divider  405  including a first resistor  407  and a second resistor  408 , a zener diode  406 , and a transistor  410 . In an example, the transistor  410  compares a representation of an output voltage V OUT  to a reference voltage across the zener diode  406 . In an example, the thermally-compensated precision zener diode  420  can form at least a portion of a primary regulator. In certain examples, the thermally-compensated precision zener diode  420  can include a third resistor  412  to keep the zener diode conducting current at low voltages. In an example, the thermally-compensated precision zener diode  420  can regulate a 12 volt output voltage V OUT . In such an example, the regulator  401  can include a zener diode  406  having a 6.2 breakdown voltage, the first resistor  407  can be about 137 kohms, the second resistor  408  can be about 86.6 kohms and the bias resistor can be about 430 kohms. The operating current of the regulator can be about 60 μA. In addition, the configuration of the zener diode  406  and the base emitter junction of the transistor  410  can provide thermally compensation of the precision zener diode  420 . such that the temperature coefficient error of the output voltage V OUT  is about −24 ppm/° C. It is understood that other component values and other output voltages can be realized using the thermally-compensated precision zener diode  420  of  FIG. 4 . For example, the output voltages listed in Table 2 can be realized using the corresponding resistance values for the first and second resistors  407 ,  408  and the corresponding zener voltage for the zener diode  406 . In certain examples, an integrated circuit can include the transistor  410  and the zener diode  406 . In such an example, components external to the integrated circuit, such as the first resistor  407  and the second resistor  408  can be selected to provide a desired output voltage, V OUT . In an example, the second resistor  408  can be adjustable to allow selection of the output voltage via the adjustable second resistor  408 . 
       FIG. 5  illustrates generally an example high-efficiency, thermally-compensated, primary regulator  501 . The regulator  501  can include a zener diode  506 , a first transistor  510 , a pull-up resistor  515 , an output pass transistor  516 , and a voltage divider  505  including a first resistor  507  and a second resistor  508 . In an example, the regulator  501  can include an output pass transistor  516  to receive feedback information  504  from the collector of the first transistor  510  and can modulate the output voltage V OUT  using a supply voltage V S . In an example, the feedback information  504  can include information indicative of an error of the output voltage V OUT . In certain examples, the output pass transistor  516  can include a high gain transistor such as a Darlington transistor or a metal-oxide-semiconductor field-effect transistor (MOSFET). In certain examples, the output voltage V OUT  of the regulator  501  can be used to power other components of a power supply such as the power supply controller. In an example using a bipolar junction transistor, the pull-up resistor  515  can be about 300 kohms and the zener diode  506  can have a breakdown voltage of about 6.8 volts. The first resistor  507  can be about 162 kohms and the second resistor  508  can be about 324 kohms. Such a regulator can provide an output voltage of about 12 volts using about 35 μA. In certain examples, the regulator  501  can include a filter  511  to ensure loop stability. In certain examples, the filter  511  can include a resistor and a capacitor coupled in series between the control nodes of the first transistor  510  and the second transistor  515 . In addition to providing a high efficiency regulator, the example regulator  501  of  FIG. 5  can provide a thermal compensation. In an example, a zener diode  506 , with a zener voltage of about 6.8 volts, can have a temperature coefficient of about 2.658 mV/C. In combination with the first transistor  510 , such as a first transistor having a base-emitter temperature coefficient of about −2.18 mV/C, the regulator  501  can have an output temperature coefficient of about 0.72 mV/C or about 60 ppm/° C. for a 12 volt output. In certain examples, an integrated circuit can include the transistor  510  and the zener diode  506 . The transistor  510  and the zener diode  506  can be provide with complementary thermal coefficients to provide a thermally compensated regulator. In such an example, components external to the integrated circuit, such as the first resistor  507  and the second resistor  508  can be selected to provide a desired output voltage, V OUT . The illustrated examples of  FIGS. 2-5  employ a bipolar junction transistor, however, it is understood that other types of transistors can be used to provide a thermally-compensated, zener diode based regulator without departing from the scope of the present subject matter. In certain examples, the regulator  501  can regulate output current such as the current through the output pass transistor  516 . 
       FIG. 6  illustrates generally an example high-current shunt regulator  600  including a zener diode  606 , transistor  610 , a voltage divider  605 , a pull-up resistor  632 , a current limit resistor  631 , and a power transistor  630 . In an example, the power transistor can include, but is not limited to, a bipolar transistor or a MOSFET. In certain examples, the voltage divider  605  can include a first resistor  607  and a second resistor  608 . In certain examples, the zener diode and junction of the transistor define a reference voltage, V REF . The output voltage V OUT  can be substantially proportional to the reference voltage by the ratio of the resistance R2 of the second resistor  608  to the resistance R1 of the first resistor  607  such that, 
               V   OUT     =         V   REF     ⁡     (     1   +       R   ⁢           ⁢   2       R   ⁢           ⁢   1         )       .           
In an example, as the output voltage V OUT  is pulled higher or lower by changes in the input voltage V IN , the voltage divider  605  can exert a corresponding change to V REF . In response to the exertion to change V REF , the transistor  610  can change voltage at the gate of the power transistor  630  to maintain the V OUT  established by the equation above. For example, if the input voltage V IN  rises, exerting an increase on V REF  and V OUT , the power transformer  630  can increase shunt current resulting in more current through the limit resistor  631  thus creating a larger voltage drop across the limit resistor  631  to maintain the desired lower output voltage V OUT . If the input voltage V IN  decreases, exerting a decrease on the reference voltage V REF  and the output voltage V OUT , the power transistor  630  can reduce the shunt current resulting in less current through the current limit resistor  631  thus reducing the voltage drop across the limit resistor  631  and maintaining the desired higher output voltage V OUT .
 
     In an example, the second resistor  608  can be adjustable such that the output voltage V OUT  can be selected via the adjustment of the second resistor  608 . In certain examples, the transistor  610  and the zener diode  606  can be selected to have complementary thermal coefficients such that the high-current shunt regulator is thermally compensated. In an example, an integrated circuit can include the transistor  610  and the zener diode  606 . 
       FIG. 7  illustrates generally a thermally compensated precision current source  700  that can include a zener diode, a transistor  710 , a sense resistor  740 , a pull-up resistor  741 , and a power transistor  742 . IN an example, the power transistor  742  can include, but is not limited to a bipolar transistor or a MOSFET. In certain examples, the output current I OUT  can be selected independent of the input voltage V IN . In certain examples, selection of the transistor  710  and the zener voltage of the zener diode  706  and the resistance value RS of the sense resistor  740  can determine the value of the output current I OUT  such that, 
     
       
         
           
             
               
                 I 
                 OUT 
               
               = 
               
                 
                   V 
                   REF 
                 
                 RS 
               
             
             , 
           
         
       
     
     where V REF  can be the voltage across the zener diode and the junction of the transistor coupled to the zener diode. The input voltage V IN  can disable the precision current source by not maintain a voltage high enough to maintain V REF . In an example, the sense resistor  740  can be adjustable such that the output current I OUT  can be selected via the adjustment of the sense resistor  740 . In certain examples, the transistor  710  and the zener diode  706  can be selected to have complementary thermal coefficients such that the precision current source is thermally compensated. In an example, an integrated circuit can include the transistor  710  and the zener diode  706 . 
     In certain examples, a kit can include an integrated circuit and instructions for making examples circuits such as those illustrated in  FIGS. 2-7 . In an example, the integrated circuit of the kit can include a transistor and a zener diode having complementary thermal coefficients for making one or more thermally compensated or low-power circuits of  FIGS. 2-7 . 
     Additional Notes 
     In Example 1, a regulator can include a zener diode having a first temperature coefficient, the zener diode configured to couple to a power supply output and to provide at least a portion of a reference voltage, a transistor having a second temperature coefficient, the transistor configured to receive the reference voltage, to receive a representation of the power supply output, and to provide feedback information indicative of an error of the power supply output using the representation of the power supply output and the reference voltage, and wherein the first temperature coefficient and the second temperature coefficient are configured to reduce at least a portion of a temperature drift effect of the zener diode and the transistor. 
     In Example 2, the regulator of Example 1 optionally includes a first resistor coupled to the power supply output, a second resistor coupled to ground in series with the first resistor, and wherein a control node of the transistor is configured to receive the at least portion of the reference voltage from a node coupled to the first resistor and the second resistor. 
     In Example 3, the zener diode of any one or more of Examples 1-2 is optionally coupled between the transistor and ground. 
     In Example 4, the power supply output of any one or more of Examples 1-3 is optionally configured to provide an output current, such as a regulated output current. 
     In Example 5, the power supply output of any one or more of Examples 1-4 is optionally configured to provide an output voltage, such as a regulated output voltage. 
     In Example 6, the output voltage, V OUT , of any one or more of Examples 1-5 is optionally given by,
 
 V   OUT   =V   REF (1+ R   1   /R   2 ),
 
wherein V REF  is the reference voltage, R 1  is a resistance value of the first resistor, and R 2  is a resistance value of the second resistor.
 
     In Example 7, the zener diode of any one or more of Examples 1-2 is optionally coupled in series with the first resistor and the second resistor. 
     In Example 8, the power supply output of any one or more of Examples 1-7 is configured to provide an output current, such as a regulated output current. 
     In Example 9, the power supply output of any one or more of Examples 1-8 is optionally configured to provide an output voltage, such as a regulated output voltage. 
     In example 10, a ratio of the first thermal coefficient to the second thermal coefficient of any one or more of Examples 1-9 is optionally substantially equal to a ratio of a resistance of the first resistor to a resistance of the second resistor. 
     In Example 11, the first temperature coefficient of any one or more of Examples 1-10 optionally includes a positive voltage change with increasing temperature and the second temperature coefficient of any one or more of Examples 1-10 optionally includes a negative voltage change with increasing temperature. 
     In Example 12, the first temperature coefficient of any one or more of Examples 1-10 optionally includes a negative voltage change with increasing temperature and the second temperature coefficient of any one or more of Examples 1-10 optionally includes a positive voltage change with increasing temperature. 
     In Example 13, an integrated circuit of any one or more of Examples 1-12 optionally includes the transistor and the zener diode. 
     In Example 14, a power supply can include a power supply controller, power electronics configured to receive an input voltage and to provide an output using command signals from the power supply controller, and a regulator configured receive the output and to provide feedback information to the power supply controller. the regulator can include a zener diode having a first temperature coefficient, the zener diode configured to couple to the output and to provide at least a portion of a reference voltage, a transistor having a second temperature coefficient, the transistor configured to receive the reference voltage, to receive a representation of the output, and to provide the feedback information using the representation of the output and the reference voltage, the feedback information indicative of an error of the output, and wherein the first temperature coefficient and the second temperature coefficient are configured to reduce at least a portion of a temperature drift effect of the zener diode and the transistor. 
     In Example 15, the power supply controller of any one or more of Examples 1-14 optionally includes a pulse width modulated controller and the power electronics include a power transistor. 
     In Example 16, the power supply controller of any one or more of Examples 1-5 optionally includes a flyback power supply controller. 
     In Example 17, the power supply controller of any one or more of Examples 1-16 optionally includes a half bridge driver. 
     In Example 18, the power supply controller of any one or more of Examples 1-17 optionally includes a full bridge driver. 
     In Example 19, a method for regulating an output can include providing at least a portion of a reference voltage using an power supply output coupled to a zener diode, the zener diode having a first thermal coefficient, receiving the reference voltage at a transistor coupled to the zener diode, receiving a representation of the power supply output at the transistor, providing feedback information indicative of an error of the power supply output using the representation of the power supply output and the reference voltage, and reducing at least a portion of a temperature drift effect of the zener diode and the transistor using the first temperature coefficient and the second temperature coefficient. 
     The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls. 
     In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. 
     The above description is intended to be illustrative, and not restrictive. For example, although the examples above may have been described relating to NPN devices, one or more examples can be applicable to PNP devices or MOSFET devices in some application. In other examples, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.