US20180352327A1 - Methods and apparatus for controlling a bias voltage - Google Patents
Methods and apparatus for controlling a bias voltage Download PDFInfo
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- US20180352327A1 US20180352327A1 US15/613,437 US201715613437A US2018352327A1 US 20180352327 A1 US20180352327 A1 US 20180352327A1 US 201715613437 A US201715613437 A US 201715613437A US 2018352327 A1 US2018352327 A1 US 2018352327A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
- H02M3/07—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider using capacitors charged and discharged alternately by semiconductor devices with control electrode, e.g. charge pumps
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R19/00—Electrostatic transducers
- H04R19/005—Electrostatic transducers using semiconductor materials
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
- H04R2201/003—Mems transducers or their use
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2410/00—Microphones
- H04R2410/03—Reduction of intrinsic noise in microphones
Definitions
- the bias voltage required to convert an acoustic signal into an electrical signal is approximately 10V-15V.
- the bias voltage must reach a target value with a specified period of time, for example within milliseconds after start-up, to achieve a stable input/output signal.
- the input/output signal of the system may be diminished and may exhibit a low signal-to-noise ratio.
- Conventional methods employed for reducing noise in the signal such as a low-pass filter, may introduce other negative effects.
- low-pass filters generally exhibit a large time constant, which interferes with the stabilization of the input/output signal.
- Other systems may include additional control terminals to control the bias voltage, which increases the size and cost of the system.
- Various embodiments of the present technology may comprise methods and apparatus for controlling a bias voltage.
- Methods and apparatus for controlling a bias voltage to an electrical device may operate in conjunction with a charge pump and a voltage regulator.
- a pulse generator may be employed to vary the output voltage of the voltage regulator, which in turn, varies the output voltage (bias voltage) generated by the charge pump.
- the pulse generator may be activated at the start-up of the electrical device.
- FIG. 1 is a block diagram of a system in accordance with an exemplary embodiment of the present technology
- FIG. 2A is a desired bias voltage waveform and an actual bias voltage waveform of the system in accordance with an exemplary embodiment of the present technology
- FIG. 2B is a desired input signal waveform and an actual input signal waveform of the system in accordance with an exemplary embodiment of the present technology
- FIG. 3A is a circuit schematic of a charge pump system in accordance with an exemplary embodiment of the present technology
- FIG. 3B is a graph illustrating an output voltage of the charge pump system versus time in accordance with an exemplary embodiment of the present technology
- FIG. 3C is a graph illustrating a bias voltage of the charge pump system versus time, and a bias voltage of a conventional charge pump system versus time in accordance with an exemplary embodiment of the present technology
- FIG. 4A is circuit schematic of a voltage regulator in accordance with a first exemplary embodiment of the present technology
- FIG. 4B is circuit schematic of a voltage regulator in accordance with a second exemplary embodiment of the present technology
- FIG. 4C is a graph illustrating an output voltage of the voltage regulator versus time in accordance with an exemplary embodiment of the present technology
- FIG. 5A is a circuit schematic of a clock driver in accordance with an exemplary embodiment of the present technology
- FIG. 5B is a graph illustrating input and output clock values of the clock driver versus time in accordance with an exemplary embodiment of the present technology
- FIG. 6A is a circuit schematic of a pulse generator in accordance with an exemplary embodiment of the present technology
- FIG. 6B is a graph illustrating an output voltage of the pulse generator circuit versus time in accordance with an exemplary embodiment of the present technology.
- FIG. 6C is a graph illustrating a supply voltage of the pulse generator circuit versus time and an intermediate voltage of the pulse generator circuit versus time in accordance with an exemplary embodiment of the present technology.
- the present technology may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of components configured to perform the specified functions and achieve the various results.
- the present technology may employ various filters, amplifiers, signal converters, drivers, and semiconductor devices, such as transistors, capacitors, and the like, which may carry out a variety of functions.
- the present technology may be practiced in conjunction with any number of electronic systems, such as automotive, aviation, “smart devices,” portables, and consumer electronics, and the systems described are merely exemplary applications for the technology.
- the present technology may employ any number of conventional techniques for pulse generation, clock signal generation, voltage regulation, and the like.
- Methods and apparatus for controlling a bias voltage may operate in conjunction with any suitable electronic system, such as an audio system, a microphone system, a video telephone, an acoustics system, hearing devices, and the like.
- an electronic device may comprise an audio system 100 configured to detect and process sound.
- the system 100 may comprise a micro electro-mechanical system (MEMS) device 110 coupled to an integrated circuit (IC) 105 .
- MEMS micro electro-mechanical system
- IC integrated circuit
- the MEMS device 110 and the IC 105 may be integrated on a single chip.
- the MEMS device 110 may convert acoustic pressure waves into an electrical signal, for example an analog electrical signal with the use of a flexible diaphragm.
- the MEMS device 110 may be fabricated using conventional MEMS processing techniques.
- the source of the analog signal may comprise, however, any suitable source of analog signals, such as a microphone, sensor, or signal generator.
- the IC 105 may be coupled to the MEMS device 110 to provide a bias voltage V B and to receive an input signal IN from the MEMS device 110 .
- the IC 105 may comprise various circuits and/or systems suitably configured to process the input signal IN, regulate the voltage of various circuits and/or systems, and generate the bias voltage.
- the IC 105 may be configured to receive supply voltages, such as a positive supply voltage V DD , and a reference voltage, such as a ground GND and a negative supply voltage V SS .
- the IC 105 may comprise a pulse generator circuit 140 , a voltage regulator circuit 145 , a clock divider circuit 150 , a clock driver circuit 135 , and a charge pump system 130 , which operate in conjunction with each other to generate the bias voltage V B .
- the IC 105 may be further coupled to or include a clock generator or other timing circuit (not shown) for producing a clock signal CLK.
- the clock signal CLK may be transmitted to an input terminal of the IC 105 .
- the clock generator may produce a symmetrical square wave and/or other suitable waveforms.
- the clock generator may be formed from a resonant circuit and an amplifier.
- the clock generator may be formed on the same chip as the IC 105 or on a companion chip.
- the clock divider circuit 150 may comprise any suitable components, logic gates, semiconductor devices, and the like to generate a desired output signal with a desired frequency, given a particular input signal.
- the clock divider 150 may produce a symmetrical square wave or other suitable waveforms.
- the n value may be selected according to any suitable parameter, such as the particular application, power consumption limitations, and the like.
- the clock divider circuit 150 is coupled to and transmits the clock divider output signal C OUT to the clock driver circuit 135 .
- the pulse generator circuit 140 generates a control signal V out .
- the pulse generator circuit 140 may comprise any circuit capable of generating a pulse with a maximum voltage value V max at a start-up (e.g., when the positive supply voltage V DD is applied) of the system 100 .
- the pulse generator circuit 140 may comprise a first RC network 600 comprising a first capacitor 635 in series with a first resistor 625 , and a second RC network 605 comprising a second capacitor 640 in series with a second resistor 630 .
- the first and second RC networks 600 , 605 are coupled via a first inverter chain 610 .
- the pulse generator circuit 140 may further comprise a conventional Schmitt trigger 620 and a second inverter chain 615 , wherein the Schmitt trigger 620 is coupled between the second RC network and the second inverter chain 615 .
- the maximum voltage value V max may be selected according to a particular application, desired bias voltage, and the like, and is influenced by the values of the first and second resistors 625 , 630 and the first and second capacitors 635 , 640 . As such, the values of the first and second resistors 625 , 630 and the first and second capacitors 635 , 640 may be chosen to produce a particular maximum voltage value V max .
- the pulse generator circuit 140 generates a rectangular pulse having a pulse width.
- the pulse generator circuit 140 may be coupled to the positive supply voltage V DD and the negative supply voltage V SS .
- the pulse width may be adjusted by the first and second RC networks 600 , 605 . In general, the pulse width changes by the adjustment of the time constant of the second RC network 605 .
- the slope of V Y changes by the values of the second resistor 630 and the second capacitor 640 , and thus the pulse width also changes.
- the values of the second resistor 630 and the second capacitor 640 may be chosen to produce a particular pulse width.
- the pulse generator circuit 140 may be further coupled to and configured to transmit the control signal V out to the voltage regulator circuit 145 .
- the pulse generator circuit 140 may be integrated within the IC 105 , however in an alternative embodiment, the pulse generator circuit 140 may be formed on a companion chip outside the IC 105 .
- the voltage regulator circuit 145 generates a reference voltage V REF and a regulator voltage V REG .
- the voltage regulator 145 operates in conjunction with the clock driver 135 and the charge pump system 130 to adjust the bias voltage V B .
- the system 100 increases the bias voltage V B for a period of time immediately after start-up,
- the voltage regulator circuit 145 may generate a variable regulator voltage V REG based on the control signal V out from the pulse generator circuit 140 .
- the reference voltage V REF and the regulator voltage V REG may be proportional to the control signal V out .
- the voltage regulator circuit 145 may be coupled to and configured to transmit the regulator voltage V REG to the charge pump system 130 via the clock driver 135 . Therefore, variations in the reference voltage V REF and the regulator voltage V REG affect the bias voltage V B . For example, as the reference voltage V REF increases, the regulator voltage V REG also increases, and the bias voltage V B also increases.
- the voltage regulator circuit 145 may comprise any appropriate circuit and/or system to generate the reference voltage V REF according to the control signal V out , including any appropriate number and type of transistors, capacitive elements, resistive elements, and the like.
- the voltage regulator circuit 145 comprises a primary circuit 400 , a secondary circuit 410 , and a switching circuit 405 .
- the switching circuit 405 selectively couples one of the primary circuit 400 and the secondary circuit 410 to a reference voltage, such as the negative supply voltage V SS , according to the control signal V out from the pulse generator 140 , to effect a change in the reference voltage V REF and the regulator voltage V REG .
- the switching circuit 405 may comprise a switch 420 responsive to the control signal V out and a resistor R A , and the switch 420 may be coupled in series with the resistor R A .
- the switch 420 may operate according to the control signal V out to couple/decouple the resistor R A to/from the negative supply voltage V SS .
- the switching circuit 405 may be coupled to the primary circuit 400 .
- the switching circuit 405 may be coupled to the secondary circuit 410 .
- An exemplary voltage regulator circuit 145 may comprise the primary circuit 400 for generating a variable reference voltage V REF .
- the primary circuit 400 may be configured as a band-gap reference circuit.
- the switching circuit 405 is coupled to one of the primary circuit 400 and the secondary circuit 410 to effect a change in the regulator voltage V REG .
- the primary circuit 400 may comprise a plurality of transistors MP 1 , MP 2 , MP 3 , QN 1 , QN 2 , QN 3 and a plurality of resistive elements, such as resistors R 1 , R 2 .
- the transistor QN 1 has a base-emitter voltage V BE1
- the transistor QN 2 has a base-emitter voltage V BE2
- the transistor QN 3 has a base-emitter voltage V BE3
- the transistor QN 1 has a collector current I 1
- the transistor QN 2 has a collector current I 2
- the transistor QN 3 has a collector current I 3 . Therefore:
- V BE2 V BE1 +R 1 ⁇ I 1 (equation 1).
- V BE ⁇ ⁇ 2 - V BE ⁇ ⁇ 1 k ⁇ T q ⁇ ln ⁇ ( M N ) . ( equation ⁇ ⁇ 2 )
- I 1 1 R 1 ⁇ k ⁇ T q ⁇ ln ⁇ ( M N ) , ( equation ⁇ ⁇ 3 )
- k is Boltzmann's constant
- T is temperature in Kelvin
- V BE1 is a base-emitter voltage of transistor QN 1
- q is the magnitude of the electrical charge on the electron
- M and N are the number of transistors that equal the equivalent transistors QN 1 and QN 2 , respectively.
- V REF the reference voltage V REF
- the primary circuit 400 may exhibit various temperature characteristics.
- the reference voltage V REF does not depend on the positive supply voltage V DD , the primary circuit 400 is capable of producing an accurate reference voltage V REF .
- the secondary circuit 410 may be configured to generate the regulator voltage V REG .
- the secondary circuit may be coupled to the primary circuit 400 and configured to receive the reference voltage V REF .
- the reference voltage V REF affects the regulator voltage V REG .
- the secondary circuit 410 may comprise any suitable components that are capable of operating in conjunction with each other to generate the regulator voltage V REG according to the reference voltage.
- the secondary circuit 410 may comprise an operational amplifier (op-amp) 415 to provide a high DC gain, a transistor MP 4 , and various resistors, such as resistors R 4A , R 4B .
- the resistors R 4A , R 4B and the transistor MP 4 may be coupled in series.
- the secondary circuit 410 may comprise a feedback loop connecting a node N between the resistors to a non-inverting terminal (+) of the op-amp 415 .
- the primary circuit 400 may be coupled to the secondary circuit 410 via an inverting terminal ( ⁇ ) of the op-amp 415 , wherein the op-amp is configured to receive the reference voltage V REF .
- a relationship between the regulator voltage V REG and the reference voltage V REF may be described as:
- V REG ( R 4 ⁇ A R 4 ⁇ B + 1 ) ⁇ V X . ( equation ⁇ ⁇ 7 )
- V REG ( R 4 ⁇ A R 4 ⁇ B + 1 ) ⁇ V REF . ( equation ⁇ ⁇ 8 )
- an equivalent resistance R X can be calculated as follows:
- R X R 1 ⁇ R A R 1 + R A ⁇ R 1 . ( equation ⁇ ⁇ 9 )
- V REF voltage reference V REF
- V REF V BE ⁇ ⁇ 3 + R 2 R X ⁇ k ⁇ T q ⁇ ln ⁇ ( M N ) , ( equation ⁇ ⁇ 10 )
- the reference voltage V REF varies according to the control signal V OUT from the pulse generator circuit 140 .
- the regulation voltage V REG varies as the reference voltage V REF varies, and the reference voltage V REF varies according to the control signal V OUT . Therefore, operation of the pulse generator circuit 140 has an effect on the reference voltage V REF , the regulator voltage V REG , and the bias voltage V B .
- an equivalent resistance R Y can be calculated as follows:
- R Y R 4 ⁇ B ⁇ R A R 4 ⁇ B + R A ⁇ R 4 ⁇ B . ( equation ⁇ ⁇ 11 )
- V REF voltage reference V REF
- V REG ( R 4 ⁇ A R Y + 1 ) ⁇ V REF . ( equation ⁇ ⁇ 12 )
- the regulation voltage V REG varies as the reference voltage V REF varies, and the reference voltage V REF varies according to the control signal V OUT . Therefore, operation of the pulse generator circuit 140 and resulting control signal V OUT has an effect on the reference voltage V REF , the regulator voltage V REG , and the bias voltage V B .
- the clock driver 135 generates a signal with various voltage levels at predetermined rise and fall times.
- the clock driver 135 may receive a clock driver input signal CLK IN , such as the clock driver output signal C OUT , and generate a clock driver output signal CLK OUT .
- the clock driver 135 may comprise a first inverter 520 coupled to a second inverter 525 (also referred to as a non-inverting buffer).
- the first inverter 520 may comprise a first transistor 500 coupled in series with a second transistor 510
- the second inverter 525 may comprise a third transistor 505 coupled in series with a fourth transistor.
- the first and third transistors 500 , 505 may be configured as PMOS transistors, and the first and fourth transistors 510 , 515 may be configured as NMOS transistors.
- the first and second inverters 520 , 525 may be coupled to the voltage regulator circuit 145 and receive the regulator voltage V REG . Accordingly, a voltage level of the clock output signal CLK OUT may be commensurate with the regulator voltage V REG .
- the charge pump system 130 generates the bias voltage V B according to the clock driver output signal CLK OUT .
- the charge pump system 130 may be configured to generate a higher voltage from a lower voltage, generate the desired bias voltage V B within a short period of time (e.g., approximately 10-20 ms), and remove noise from intermediate signals.
- the charge pump system 130 may comprise a charge pump 325 , a low-pass filter 330 , and a diode 310 .
- the charge pump circuit 325 may be configured to generate a charge pump output CP OUT (i.e., the intermediate signal), wherein the charge pump output CP OUT is greater than the positive supply voltage V DD .
- the charge pump circuit 325 may comprise a conventional charge pump circuit with a plurality of charge pump units 300 ( 1 ): 300 (N) and a plurality of capacitors 305 ( 1 ): 305 (N).
- the charge pump circuit 325 may comprise an integrator circuit 335 , such as an RC network, to facilitate proper functioning of the charge pump circuit 325 during start-up and/or operation.
- the integrator circuit 335 may comprise a resistor 340 and capacitor 345 .
- the integrator circuit 335 may be coupled directly to one of the charge pump units 300 , for example, a first charge pump unit 300 ( 1 ).
- a first end of the resistor 340 may be coupled to the same reference voltage as the charge pump circuit 325 , such as a ground GND, and the capacitor 345 may be coupled to the negative supply voltage V SS .
- the low-pass filter 330 may be configured to attenuate various frequencies in the bias voltage V B .
- the low-pass filter 330 is coupled to the charge pump circuit 325 and configured to receive the charge pump output CP OUT .
- the low-pass filter 330 has a low cut-off frequency to remove noise from the charge pump output CP OUT and thus provide a bias voltage V B with minimal noise.
- the low-pass filter 330 may comprise a resistor 315 in series with a capacitor 320 .
- the diode 310 may be configured to provide the desired bias voltage V B within a short period of time and reduce the effects (the long time constant T C ) of the low-pass filter 330 .
- the diode 310 may be coupled in parallel with the resistor 315 . In this way, the diode 310 acts as a short circuit and provides increased current flow, and thus, reduces the effect that the time constant T C has on the bias voltage V B . As a result, the bias voltage V B increases quickly after start-up.
- the diode 310 may be configured as a forward-biased diode with a threshold voltage of approximately 0.5-0.7V.
- a conventional charge pump system 130 that does not incorporate the diode 310 has a bias voltage V B that increases linearly
- a conventional charge pump system 130 that incorporates the diode 310 in parallel with the low-pass filter 330 has a bias voltage V B that increases quickly after start-up and then continues to increase but at a slower rate.
- the quick increase in the bias voltage V B after start-up and slowed increase later is the result of the diode 310 being ON after start-up and turning OFF later due to the reverse bias applied by the capacitor 320 . Accordingly, the bias voltage V B does not follow the charge pump output CP OUT and does not reach the target value until some later time due to the time constant Tc of the low-pass filter 330 .
- the IC 105 may further comprise various circuits and/or systems to process the input signal IN and convert it to a digital signal (i.e., digital data).
- the system 100 may comprise a preamplifier 115 , a filter 120 , and a signal converter, such as an ADC 125 .
- the input signal IN from the MEMS device 110 may be coupled, directly or indirectly, to the IC 105 for processing.
- the preamplifier 115 , the filter 120 , and the ADC 125 may be coupled in series.
- the preamplifier 115 may amplify the input signal IN.
- the preamplifier 115 may comprise any suitable circuit and/or system to receive in the input signal IN and transmit an amplified signal to the filter 120 .
- the preamplifier 115 may be configured in any suitable manner for the particular application and/or environment.
- the IC 105 may process the input signal IN prior to the analog-to-digital conversion, for example to inhibit aliasing and/or produce a signal with a desired precision.
- the filter 120 may comprise a low-pass filter to pass input analog signals with frequencies below a predetermined frequency and attenuate signals with frequencies above a predetermined frequency.
- the filter 120 may be configured as an analog filter and may be fabricated using passive elements, such as a resistive element (not shown) and/or a capacitor (not shown), for example because such passive elements may be small in size and consume less current than active elements, such as a transistor.
- filter 120 is configured to receive the amplified signal from the preamplifier 115 .
- the ADC 125 may convert an analog signal into a digital signal.
- the ADC 125 may comprise any suitable circuit for converting the input signal IN into a digital signal (i.e., digital data).
- the ADC 125 may comprise a delta-sigma ADC or other suitable ADC architecture.
- the ADC 125 may be coupled in series with the filter 120 and/or the pre-amplifier 115 .
- the ADC 125 may be configured in any suitable manner for the particular application and/or environment.
- the IC 105 may generate a bias voltage V B that reaches the target value within a short period of time after start-up and maintains the target value.
- the input signal IN exhibits improved signal quality, which leads to more accurate digital data.
- the IC 105 may be configured to generate various signals that are capable of being adjusted after start-up of the system 100 .
- the pulse generator circuit 140 upon start-up of the system 100 , receives the supply voltage V DD and the pulse generator circuit 140 generates the control signal V OUT .
- the control signal V OUT reaches a maximum value V OUT _ MAX (i.e., control signal maximum value) within a first period T 1 .
- the control signal V OUT forms a square pulse.
- the pulse generator circuit 140 transmits the control signal V OUT to the voltage regulator circuit 145 .
- the voltage regulator circuit 145 responds to the control signal V OUT and generates the regulator voltage V REG according to the control signal V OUT .
- the control signal V OUT when the control signal V OUT is high (“ON”), the reference voltage V REF reaches a maximum value and the regulator voltage V REG reaches a maximum value.
- the control signal when the control signal is low (“OFF”), the reference voltage V REF reaches a minimum value and the regulator voltage V REG reaches a minimum value.
- the regulator voltage V REG increases and reaches a maximum value V REG _ MAX (i.e., regulator maximum value) when the control signal V OUT reaches its maximum value V OUT _ MAX (i.e., control signal maximum value).
- V REG _ MAX i.e., regulator maximum value
- the regulator voltage V REG shifts to a minimum value V REG _ MIN (i.e., regulator minimum value) during a second period T 2 .
- the second period T 2 may immediately follow the first period T 1 .
- the clock driver circuit 135 receives the regulator voltage V REG and the clock divider output signal C OUT .
- the clock driver circuit 135 generates the clock driver output signal CLK OUT according to the regulator voltage V REG and the clock divider output signal C OUT .
- the charge pump system 130 receives the clock driver output signal CLK OUT .
- the charge pump circuit 325 generates the charge pump output CP OUT according to the clock driver output signal CLK OUT .
- the charge pump output CP OUT reaches a maximum value CP OUT _ MAX (i.e., charge pump maximum value) during the first period T 1 when the charge pump system 130 receives the clock driver output maximum CLK OUT _ MAX .
- the charge pump system 130 then passes the charge pump output CP OUT through the low-pass filter 330 to pass desired frequencies and the diode 310 connected in parallel allows for quicker charging of the capacitor 320 .
- the voltage difference between the charge pump maximum value CP OUT _ MAX and a charge pump minimum value CP OUT _ MIN may be set to be equal to the threshold voltage of the diode 310 .
- the charge pump system 130 is able to generate a bias voltage V B that reaches the target value quicker than with a conventional IC and is able to maintain the target value because the regulator voltage V REG is adjusted to compensate for the threshold voltage of the diode 310 and the time constant of the low-pass filter 330 due to the OFF period of the diode 310 is diminished, which improves the input signal IN quality, for example as illustrated in FIGS. 2A and 2B .
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Abstract
Description
- Many electrical systems require a high bias voltage to generate an appropriate input/output signal. For example, in a MEMS (micro electro-mechanical system) microphone system, the bias voltage required to convert an acoustic signal into an electrical signal is approximately 10V-15V. In general, the bias voltage must reach a target value with a specified period of time, for example within milliseconds after start-up, to achieve a stable input/output signal. When an electrical system does not receive the required bias voltage within the specified period of time, the input/output signal of the system may be diminished and may exhibit a low signal-to-noise ratio. Conventional methods employed for reducing noise in the signal, such as a low-pass filter, may introduce other negative effects. For example, low-pass filters generally exhibit a large time constant, which interferes with the stabilization of the input/output signal. Other systems may include additional control terminals to control the bias voltage, which increases the size and cost of the system.
- Various embodiments of the present technology may comprise methods and apparatus for controlling a bias voltage. Methods and apparatus for controlling a bias voltage to an electrical device according to various aspects of the present invention may operate in conjunction with a charge pump and a voltage regulator. A pulse generator may be employed to vary the output voltage of the voltage regulator, which in turn, varies the output voltage (bias voltage) generated by the charge pump. The pulse generator may be activated at the start-up of the electrical device.
- A more complete understanding of the present technology may be derived by referring to the detailed description when considered in connection with the following illustrative figures. In the following figures, like reference numbers refer to similar elements and steps throughout the figures.
-
FIG. 1 is a block diagram of a system in accordance with an exemplary embodiment of the present technology; -
FIG. 2A is a desired bias voltage waveform and an actual bias voltage waveform of the system in accordance with an exemplary embodiment of the present technology; -
FIG. 2B is a desired input signal waveform and an actual input signal waveform of the system in accordance with an exemplary embodiment of the present technology; -
FIG. 3A is a circuit schematic of a charge pump system in accordance with an exemplary embodiment of the present technology; -
FIG. 3B is a graph illustrating an output voltage of the charge pump system versus time in accordance with an exemplary embodiment of the present technology; -
FIG. 3C is a graph illustrating a bias voltage of the charge pump system versus time, and a bias voltage of a conventional charge pump system versus time in accordance with an exemplary embodiment of the present technology; -
FIG. 4A is circuit schematic of a voltage regulator in accordance with a first exemplary embodiment of the present technology; -
FIG. 4B is circuit schematic of a voltage regulator in accordance with a second exemplary embodiment of the present technology; -
FIG. 4C is a graph illustrating an output voltage of the voltage regulator versus time in accordance with an exemplary embodiment of the present technology; -
FIG. 5A is a circuit schematic of a clock driver in accordance with an exemplary embodiment of the present technology; -
FIG. 5B is a graph illustrating input and output clock values of the clock driver versus time in accordance with an exemplary embodiment of the present technology; -
FIG. 6A is a circuit schematic of a pulse generator in accordance with an exemplary embodiment of the present technology; -
FIG. 6B is a graph illustrating an output voltage of the pulse generator circuit versus time in accordance with an exemplary embodiment of the present technology; and -
FIG. 6C is a graph illustrating a supply voltage of the pulse generator circuit versus time and an intermediate voltage of the pulse generator circuit versus time in accordance with an exemplary embodiment of the present technology. - The present technology may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of components configured to perform the specified functions and achieve the various results. For example, the present technology may employ various filters, amplifiers, signal converters, drivers, and semiconductor devices, such as transistors, capacitors, and the like, which may carry out a variety of functions. In addition, the present technology may be practiced in conjunction with any number of electronic systems, such as automotive, aviation, “smart devices,” portables, and consumer electronics, and the systems described are merely exemplary applications for the technology. Further, the present technology may employ any number of conventional techniques for pulse generation, clock signal generation, voltage regulation, and the like.
- Methods and apparatus for controlling a bias voltage according to various aspects of the present technology may operate in conjunction with any suitable electronic system, such as an audio system, a microphone system, a video telephone, an acoustics system, hearing devices, and the like.
- Referring to
FIG. 1 , an electronic device according to various aspects of the present technology may comprise anaudio system 100 configured to detect and process sound. For example, thesystem 100 may comprise a micro electro-mechanical system (MEMS)device 110 coupled to an integrated circuit (IC) 105. In various embodiments, theMEMS device 110 and the IC 105 may be integrated on a single chip. - In various embodiments, the
MEMS device 110 may convert acoustic pressure waves into an electrical signal, for example an analog electrical signal with the use of a flexible diaphragm. TheMEMS device 110 may be fabricated using conventional MEMS processing techniques. The source of the analog signal may comprise, however, any suitable source of analog signals, such as a microphone, sensor, or signal generator. - The IC 105 may be coupled to the
MEMS device 110 to provide a bias voltage VB and to receive an input signal IN from theMEMS device 110. TheIC 105 may comprise various circuits and/or systems suitably configured to process the input signal IN, regulate the voltage of various circuits and/or systems, and generate the bias voltage. TheIC 105 may be configured to receive supply voltages, such as a positive supply voltage VDD, and a reference voltage, such as a ground GND and a negative supply voltage VSS. In an exemplary embodiment, theIC 105 may comprise apulse generator circuit 140, avoltage regulator circuit 145, aclock divider circuit 150, aclock driver circuit 135, and acharge pump system 130, which operate in conjunction with each other to generate the bias voltage VB. - In various embodiments, the IC 105 may be further coupled to or include a clock generator or other timing circuit (not shown) for producing a clock signal CLK. The clock signal CLK may be transmitted to an input terminal of the
IC 105. The clock generator may produce a symmetrical square wave and/or other suitable waveforms. In various embodiments, the clock generator may be formed from a resonant circuit and an amplifier. The clock generator may be formed on the same chip as the IC 105 or on a companion chip. - The
clock divider circuit 150 may be configured to receive an input clock signal CLK with an input frequency fin and generate an output clock signal, such as a clock divider output signal COUT, with an output frequency fout, such as described by: fout=fin/n, where n is an integer. Theclock divider circuit 150 may comprise any suitable components, logic gates, semiconductor devices, and the like to generate a desired output signal with a desired frequency, given a particular input signal. Theclock divider 150 may produce a symmetrical square wave or other suitable waveforms. The n value may be selected according to any suitable parameter, such as the particular application, power consumption limitations, and the like. In an exemplary embodiment, theclock divider circuit 150 is coupled to and transmits the clock divider output signal COUT to theclock driver circuit 135. - The
pulse generator circuit 140 generates a control signal Vout. Thepulse generator circuit 140 may comprise any circuit capable of generating a pulse with a maximum voltage value Vmax at a start-up (e.g., when the positive supply voltage VDD is applied) of thesystem 100. For example, referring toFIG. 6A , thepulse generator circuit 140 may comprise afirst RC network 600 comprising afirst capacitor 635 in series with afirst resistor 625, and asecond RC network 605 comprising asecond capacitor 640 in series with asecond resistor 630. The first andsecond RC networks first inverter chain 610. Thepulse generator circuit 140 may further comprise aconventional Schmitt trigger 620 and asecond inverter chain 615, wherein theSchmitt trigger 620 is coupled between the second RC network and thesecond inverter chain 615. - The maximum voltage value Vmax may be selected according to a particular application, desired bias voltage, and the like, and is influenced by the values of the first and
second resistors second capacitors second resistors second capacitors - Referring to
FIGS. 1 and 6A -C, according to an exemplary embodiment, thepulse generator circuit 140 generates a rectangular pulse having a pulse width. Thepulse generator circuit 140 may be coupled to the positive supply voltage VDD and the negative supply voltage VSS. The pulse width may be adjusted by the first andsecond RC networks second RC network 605. The slope of VY changes by the values of thesecond resistor 630 and thesecond capacitor 640, and thus the pulse width also changes. The values of thesecond resistor 630 and thesecond capacitor 640 may be chosen to produce a particular pulse width. Thepulse generator circuit 140 may be further coupled to and configured to transmit the control signal Vout to thevoltage regulator circuit 145. In an exemplary embodiment, thepulse generator circuit 140 may be integrated within theIC 105, however in an alternative embodiment, thepulse generator circuit 140 may be formed on a companion chip outside theIC 105. - Referring to
FIGS. 4A-B , according to various embodiments, thevoltage regulator circuit 145 generates a reference voltage VREF and a regulator voltage VREG. According to various embodiments, thevoltage regulator 145 operates in conjunction with theclock driver 135 and thecharge pump system 130 to adjust the bias voltage VB. According to various embodiments, thesystem 100 increases the bias voltage VB for a period of time immediately after start-up, For example, according to various embodiments, thevoltage regulator circuit 145 may generate a variable regulator voltage VREG based on the control signal Vout from thepulse generator circuit 140. In an exemplary embodiment, the reference voltage VREF and the regulator voltage VREG may be proportional to the control signal Vout. Thevoltage regulator circuit 145 may be coupled to and configured to transmit the regulator voltage VREG to thecharge pump system 130 via theclock driver 135. Therefore, variations in the reference voltage VREF and the regulator voltage VREG affect the bias voltage VB. For example, as the reference voltage VREF increases, the regulator voltage VREG also increases, and the bias voltage VB also increases. - Referring to
FIGS. 4A-4C , thevoltage regulator circuit 145 may comprise any appropriate circuit and/or system to generate the reference voltage VREF according to the control signal Vout, including any appropriate number and type of transistors, capacitive elements, resistive elements, and the like. In an exemplary embodiment, thevoltage regulator circuit 145 comprises aprimary circuit 400, asecondary circuit 410, and aswitching circuit 405. - The
switching circuit 405 selectively couples one of theprimary circuit 400 and thesecondary circuit 410 to a reference voltage, such as the negative supply voltage VSS, according to the control signal Vout from thepulse generator 140, to effect a change in the reference voltage VREF and the regulator voltage VREG. In various embodiments, theswitching circuit 405 may comprise aswitch 420 responsive to the control signal Vout and a resistor RA, and theswitch 420 may be coupled in series with the resistor RA. For example, theswitch 420 may operate according to the control signal Vout to couple/decouple the resistor RA to/from the negative supply voltage VSS. In one embodiment, and referring toFIG. 4A , theswitching circuit 405 may be coupled to theprimary circuit 400. In an alternative embodiment, and referring toFIG. 4B , theswitching circuit 405 may be coupled to thesecondary circuit 410. - An exemplary
voltage regulator circuit 145 may comprise theprimary circuit 400 for generating a variable reference voltage VREF. For example, theprimary circuit 400 may be configured as a band-gap reference circuit. According to various embodiments, theswitching circuit 405 is coupled to one of theprimary circuit 400 and thesecondary circuit 410 to effect a change in the regulator voltage VREG. - According to various embodiments, the
primary circuit 400 may comprise a plurality of transistors MP1, MP2, MP3, QN1, QN2, QN3 and a plurality of resistive elements, such as resistors R1, R2. The transistor QN1 has a base-emitter voltage VBE1, the transistor QN2 has a base-emitter voltage VBE2, the transistor QN3 has a base-emitter voltage VBE3, the transistor QN1 has a collector current I1, the transistor QN2 has a collector current I2, and the transistor QN3 has a collector current I3. Therefore: -
V BE2 =V BE1 +R 1 ×I 1 (equation 1). - In addition, the transistors MP1 and MP2 have drain currents of I1, I2, respectively, and if transistors MP1 and MP2 are equally sized, then I2=I1. Further, a size ratio of transistors QN1 and QN2 is described by M:N. Therefore, the following is true:
-
- And, therefore, I1 can be written as:
-
- where k is Boltzmann's constant, T is temperature in Kelvin, and VBE1 is a base-emitter voltage of transistor QN1, q is the magnitude of the electrical charge on the electron, and M and N are the number of transistors that equal the equivalent transistors QN1 and QN2, respectively.
- If transistors MP2 and MP3 are equally sized, then I3=I2=I1, and therefore:
-
- and the reference voltage VREF may be described as follows:
-
- The
primary circuit 400 may exhibit various temperature characteristics. For example, the reference voltage VREF can be adjusted to a desired temperature coefficient by, for example, adjusting the value of the resistors R1, R2 since the temperature coefficient of a base-emitter voltage VBE1 is a negative value (e.g., approximately −2 mV/° C.) and the temperature coefficient of a thermal voltage VT, where VT=(k*T)/q, is a positive value (e.g., approximately 0.09 mV/° C.). Therefore, resistors R1, R2 may be adjusted to remove the effects of the thermal voltage by setting R2 equal to q and R1 equal to k×T, and the currents I1 and I3 can be set to a desired value. In addition, since the reference voltage VREF does not depend on the positive supply voltage VDD, theprimary circuit 400 is capable of producing an accurate reference voltage VREF. - The
secondary circuit 410 may be configured to generate the regulator voltage VREG. The secondary circuit may be coupled to theprimary circuit 400 and configured to receive the reference voltage VREF. In this way, the reference voltage VREF affects the regulator voltage VREG. In various embodiments, thesecondary circuit 410 may comprise any suitable components that are capable of operating in conjunction with each other to generate the regulator voltage VREG according to the reference voltage. For example, according to various embodiments, thesecondary circuit 410 may comprise an operational amplifier (op-amp) 415 to provide a high DC gain, a transistor MP4, and various resistors, such as resistors R4A, R4B. The resistors R4A, R4B and the transistor MP4 may be coupled in series. Thesecondary circuit 410 may comprise a feedback loop connecting a node N between the resistors to a non-inverting terminal (+) of the op-amp 415. Theprimary circuit 400 may be coupled to thesecondary circuit 410 via an inverting terminal (−) of the op-amp 415, wherein the op-amp is configured to receive the reference voltage VREF. - According to various embodiments, a relationship between the regulator voltage VREG and the reference voltage VREF may be described as:
-
- and since a DC gain of an operational amplifier is very high,
-
- According to one embodiment, and referring to
FIG. 4A , where theswitching circuit 405 is coupled to theprimary circuit 400, for example between the transistor QN1 and resistor R1, an equivalent resistance RX can be calculated as follows: -
- Therefore the voltage reference VREF may be described by:
-
- where the reference voltage VREF varies according to the control signal VOUT from the
pulse generator circuit 140. As a result, the regulation voltage VREG varies as the reference voltage VREF varies, and the reference voltage VREF varies according to the control signal VOUT. Therefore, operation of thepulse generator circuit 140 has an effect on the reference voltage VREF, the regulator voltage VREG, and the bias voltage VB. - According to an alternative embodiment, and referring to
FIG. 5B , where theswitching circuit 405 is coupled to thesecondary circuit 410, for example the node N of thesecondary circuit 410, an equivalent resistance RY can be calculated as follows: -
- Therefore the voltage reference VREF may be described by:
-
- As a result, the regulation voltage VREG varies as the reference voltage VREF varies, and the reference voltage VREF varies according to the control signal VOUT. Therefore, operation of the
pulse generator circuit 140 and resulting control signal VOUT has an effect on the reference voltage VREF, the regulator voltage VREG, and the bias voltage VB. - The
clock driver 135 generates a signal with various voltage levels at predetermined rise and fall times. For example, and referring toFIGS. 5A-B , theclock driver 135 may receive a clock driver input signal CLKIN, such as the clock driver output signal COUT, and generate a clock driver output signal CLKOUT. In an exemplary embodiment, theclock driver 135 may comprise afirst inverter 520 coupled to a second inverter 525 (also referred to as a non-inverting buffer). Thefirst inverter 520 may comprise afirst transistor 500 coupled in series with asecond transistor 510, and thesecond inverter 525 may comprise athird transistor 505 coupled in series with a fourth transistor. The first andthird transistors fourth transistors second inverters voltage regulator circuit 145 and receive the regulator voltage VREG. Accordingly, a voltage level of the clock output signal CLKOUT may be commensurate with the regulator voltage VREG. - The
charge pump system 130 generates the bias voltage VB according to the clock driver output signal CLKOUT. Thecharge pump system 130 may be configured to generate a higher voltage from a lower voltage, generate the desired bias voltage VB within a short period of time (e.g., approximately 10-20 ms), and remove noise from intermediate signals. For example, and referring toFIGS. 3A-C , thecharge pump system 130 may comprise acharge pump 325, a low-pass filter 330, and adiode 310. - The
charge pump circuit 325 may be configured to generate a charge pump output CPOUT (i.e., the intermediate signal), wherein the charge pump output CPOUT is greater than the positive supply voltage VDD. In an exemplary embodiment, thecharge pump circuit 325 may comprise a conventional charge pump circuit with a plurality of charge pump units 300(1):300(N) and a plurality of capacitors 305(1):305(N). The charge pump output CPOUT may be described according to the following: CPOUT=[unit number]*VDD. Accordingly, the number of charge pump units may be selected according to the particular application, desired charge pump output CPOUT, and other relevant factors. In addition, thecharge pump circuit 325 may comprise anintegrator circuit 335, such as an RC network, to facilitate proper functioning of thecharge pump circuit 325 during start-up and/or operation. Theintegrator circuit 335 may comprise aresistor 340 andcapacitor 345. Theintegrator circuit 335 may be coupled directly to one of thecharge pump units 300, for example, a first charge pump unit 300(1). Moreover, a first end of theresistor 340 may be coupled to the same reference voltage as thecharge pump circuit 325, such as a ground GND, and thecapacitor 345 may be coupled to the negative supply voltage VSS. - The low-
pass filter 330 may be configured to attenuate various frequencies in the bias voltage VB. For example, in an exemplary embodiment, the low-pass filter 330 is coupled to thecharge pump circuit 325 and configured to receive the charge pump output CPOUT. In an exemplary embodiment, the low-pass filter 330 has a low cut-off frequency to remove noise from the charge pump output CPOUT and thus provide a bias voltage VB with minimal noise. The low-pass filter 330 may comprise aresistor 315 in series with acapacitor 320. The low-pass filter 330 may further have a time constant Tc (in seconds) described by: Tc=C*R, where C is a capacitance value of thecapacitor 320 and R is a resistance value of theresistor 315. - The
diode 310 may be configured to provide the desired bias voltage VB within a short period of time and reduce the effects (the long time constant TC) of the low-pass filter 330. For example, thediode 310 may be coupled in parallel with theresistor 315. In this way, thediode 310 acts as a short circuit and provides increased current flow, and thus, reduces the effect that the time constant TC has on the bias voltage VB. As a result, the bias voltage VB increases quickly after start-up. - The
diode 310 may be configured as a forward-biased diode with a threshold voltage of approximately 0.5-0.7V. For example, and referring toFIG. 3C , a conventionalcharge pump system 130 that does not incorporate thediode 310 has a bias voltage VB that increases linearly, while a conventionalcharge pump system 130 that incorporates thediode 310 in parallel with the low-pass filter 330 has a bias voltage VB that increases quickly after start-up and then continues to increase but at a slower rate. The quick increase in the bias voltage VB after start-up and slowed increase later is the result of thediode 310 being ON after start-up and turning OFF later due to the reverse bias applied by thecapacitor 320. Accordingly, the bias voltage VB does not follow the charge pump output CPOUT and does not reach the target value until some later time due to the time constant Tc of the low-pass filter 330. - According to various embodiments, referring again to
FIG. 1 , theIC 105 may further comprise various circuits and/or systems to process the input signal IN and convert it to a digital signal (i.e., digital data). For example, thesystem 100 may comprise apreamplifier 115, afilter 120, and a signal converter, such as anADC 125. The input signal IN from theMEMS device 110 may be coupled, directly or indirectly, to theIC 105 for processing. In various embodiments, thepreamplifier 115, thefilter 120, and theADC 125 may be coupled in series. - The
preamplifier 115 may amplify the input signal IN. Thepreamplifier 115 may comprise any suitable circuit and/or system to receive in the input signal IN and transmit an amplified signal to thefilter 120. Thepreamplifier 115 may be configured in any suitable manner for the particular application and/or environment. - In various embodiments, the
IC 105 may process the input signal IN prior to the analog-to-digital conversion, for example to inhibit aliasing and/or produce a signal with a desired precision. For example, thefilter 120 may comprise a low-pass filter to pass input analog signals with frequencies below a predetermined frequency and attenuate signals with frequencies above a predetermined frequency. In various embodiments, thefilter 120 may be configured as an analog filter and may be fabricated using passive elements, such as a resistive element (not shown) and/or a capacitor (not shown), for example because such passive elements may be small in size and consume less current than active elements, such as a transistor. In an exemplary embodiment,filter 120 is configured to receive the amplified signal from thepreamplifier 115. - The
ADC 125 may convert an analog signal into a digital signal. In various embodiments, theADC 125 may comprise any suitable circuit for converting the input signal IN into a digital signal (i.e., digital data). For example, theADC 125 may comprise a delta-sigma ADC or other suitable ADC architecture. TheADC 125 may be coupled in series with thefilter 120 and/or thepre-amplifier 115. TheADC 125 may be configured in any suitable manner for the particular application and/or environment. - In operation, the
IC 105 may generate a bias voltage VB that reaches the target value within a short period of time after start-up and maintains the target value. As a result, the input signal IN exhibits improved signal quality, which leads to more accurate digital data. According to various embodiments, theIC 105 may be configured to generate various signals that are capable of being adjusted after start-up of thesystem 100. - In an exemplary operation, and referring to
FIGS. 1-6 , upon start-up of thesystem 100, thepulse generator circuit 140 receives the supply voltage VDD and thepulse generator circuit 140 generates the control signal VOUT. The control signal VOUT reaches a maximum value VOUT _ MAX (i.e., control signal maximum value) within a first period T1. In an exemplary embodiment, the control signal VOUT forms a square pulse. Thepulse generator circuit 140 transmits the control signal VOUT to thevoltage regulator circuit 145. Thevoltage regulator circuit 145 responds to the control signal VOUT and generates the regulator voltage VREG according to the control signal VOUT. For example, when the control signal VOUT is high (“ON”), the reference voltage VREF reaches a maximum value and the regulator voltage VREG reaches a maximum value. Alternatively, when the control signal is low (“OFF”), the reference voltage VREF reaches a minimum value and the regulator voltage VREG reaches a minimum value. - In an exemplary embodiment, during the first period T1, and referring to
FIGS. 4C and 6B , when the control signal VOUT is at the maximum value VOUT _ MAX, the regulator voltage VREG increases and reaches a maximum value VREG _ MAX (i.e., regulator maximum value) when the control signal VOUT reaches its maximum value VOUT _ MAX (i.e., control signal maximum value). When the control signal VOUT returns to zero, the regulator voltage VREG shifts to a minimum value VREG _ MIN (i.e., regulator minimum value) during a second period T2. The second period T2 may immediately follow the first period T1. The voltage difference between the regulator maximum value VREG _ MAX and the regulator minimum value VREG _ MIN may be set to be equal to the threshold voltage of thediode 310 divided by the total number (N) of charge pump units in the charge pump circuit 325 (i.e., (VREG _ MAX−VREG _ MIN)=[threshold voltage of diode 310]/[N charge pump units]). - During the first period T1 and after as the
pulse generator circuit 140 transmits the control signal COUT, theclock driver circuit 135 receives the regulator voltage VREG and the clock divider output signal COUT. Theclock driver circuit 135 generates the clock driver output signal CLKOUT according to the regulator voltage VREG and the clock divider output signal COUT. In an exemplary embodiment, and referring toFIGS. 4C, 5B, and 6B , when the regulator voltage VREG is at the regulator maximum value VREG _ MAX, the clock driver output signal CLKOUT reaches a maximum value CLKOUT _ MAX (i.e., clock driver maximum value) coincident with the regulator maximum value VREG _ MAX and the control signal maximum value VOUT _ MAX. When the control signal VOUT returns to zero and the regulator voltage VREG returns to the regulator minimum value VREG _ MIN, the clock driver output signal CLKOUT shifts to a minimum value CLKOUT _ MIN (i.e., clock driver output minimum value) during the second period T2. - During the first period T1 and after the
pulse generator circuit 140 transmits the control signal COUT, thecharge pump system 130 receives the clock driver output signal CLKOUT. In an exemplary embodiment, and referring toFIGS. 3B and 5B , thecharge pump circuit 325 generates the charge pump output CPOUT according to the clock driver output signal CLKOUT. The charge pump output CPOUT reaches a maximum value CPOUT _ MAX (i.e., charge pump maximum value) during the first period T1 when thecharge pump system 130 receives the clock driver output maximum CLKOUT _ MAX. Thecharge pump system 130 then passes the charge pump output CPOUT through the low-pass filter 330 to pass desired frequencies and thediode 310 connected in parallel allows for quicker charging of thecapacitor 320. The voltage difference between the charge pump maximum value CPOUT _ MAX and a charge pump minimum value CPOUT _ MIN may be set to be equal to the threshold voltage of thediode 310. Thus, thecharge pump system 130 is able to generate a bias voltage VB that reaches the target value quicker than with a conventional IC and is able to maintain the target value because the regulator voltage VREG is adjusted to compensate for the threshold voltage of thediode 310 and the time constant of the low-pass filter 330 due to the OFF period of thediode 310 is diminished, which improves the input signal IN quality, for example as illustrated inFIGS. 2A and 2B . - In the foregoing description, the technology has been described with reference to specific exemplary embodiments. The particular implementations shown and described are illustrative of the technology and its best mode and are not intended to otherwise limit the scope of the present technology in any way. Indeed, for the sake of brevity, conventional manufacturing, connection, preparation, and other functional aspects of the method and system may not be described in detail. Furthermore, the connecting lines shown in the various figures are intended to represent exemplary functional relationships and/or steps between the various elements. Many alternative or additional functional relationships or physical connections may be present in a practical system.
- The technology has been described with reference to specific exemplary embodiments. Various modifications and changes, however, may be made without departing from the scope of the present technology. The description and figures are to be regarded in an illustrative manner, rather than a restrictive one and all such modifications are intended to be included within the scope of the present technology. Accordingly, the scope of the technology should be determined by the generic embodiments described and their legal equivalents rather than by merely the specific examples described above. For example, the steps recited in any method or process embodiment may be executed in any order, unless otherwise expressly specified, and are not limited to the explicit order presented in the specific examples. Additionally, the components and/or elements recited in any apparatus embodiment may be assembled or otherwise operationally configured in a variety of permutations to produce substantially the same result as the present technology and are accordingly not limited to the specific configuration recited in the specific examples.
- Benefits, other advantages and solutions to problems have been described above with regard to particular embodiments. Any benefit, advantage, solution to problems or any element that may cause any particular benefit, advantage or solution to occur or to become more pronounced, however, is not to be construed as a critical, required or essential feature or component.
- The terms “comprises”, “comprising”, or any variation thereof, are intended to reference a non-exclusive inclusion, such that a process, method, article, composition or apparatus that comprises a list of elements does not include only those elements recited, but may also include other elements not expressly listed or inherent to such process, method, article, composition or apparatus. Other combinations and/or modifications of the above-described structures, arrangements, applications, proportions, elements, materials or components used in the practice of the present technology, in addition to those not specifically recited, may be varied or otherwise particularly adapted to specific environments, manufacturing specifications, design parameters or other operating requirements without departing from the general principles of the same.
- The present technology has been described above with reference to an exemplary embodiment. However, changes and modifications may be made to the exemplary embodiment without departing from the scope of the present technology. These and other changes or modifications are intended to be included within the scope of the present technology, as expressed in the following claims.
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US16/197,411 US10757504B2 (en) | 2017-06-05 | 2018-11-21 | Methods and apparatus for controlling a bias voltage |
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US10165356B1 (en) | 2018-12-25 |
US20190090054A1 (en) | 2019-03-21 |
CN208079372U (en) | 2018-11-09 |
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