Classifications

• • 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

Definitions

• Charge pump regulator circuits may be used to generate an output voltage and current to power a load circuit in an electronic device.
• charge pump regulator circuits There are different types of charge pump regulator circuits, each having different strengths and weaknesses.
• a common feature of such charge pump regulator circuits is an oscillating signal that is used to generate the output voltage and current.
• a generally undesirable result of the use of such an oscillating signal is the presence of noise, i.e. ripple or jitter, in the output current and/or voltage of the charge pump regulator circuit, even after passing the output signal through an appropriate filter.
• noise i.e. ripple or jitter
• Most load circuits though, can tolerate a certain amount of noise. Nevertheless, various trends in the development of new electronic devices make it a necessity to continually strive for lower and lower levels of noise in such regulator circuits.
• the charge pump regulator circuit 100 generally includes a voltage controlled ring oscillator 101 , a high gain buffer 102, a charge pump (a.k.a. voltage multiplier or voltage adder) 103, an RC filter 104 (resistor 105 and capacitor 106), a scaler 107 and an operational amplifier (op-amp) 108.
• the oscillator 101 generally includes a plurality of inverter stages 109 connected in series output-to-input in a ring. (Some other components or connections are implied, but not shown for simplicity.)
• the inverter stages 109 receive a drive voltage (e.g. Vdd) at 1 10 from the output of the op-amp 108. Under the control of the drive voltage, the signal inverting action of the inverter stages 109 generates an oscillating signal at 1 1 1 , e.g. the output of the one of the inverter stages 109 in the ring. A frequency and amplitude of the oscillating signal at 1 1 1 generally depends on a voltage level of the drive voltage.
• the oscillating signal at 1 1 1 is supplied to an input of the buffer 102.
• the buffer 102 generates a positive oscillating signal at 1 12 and a negative oscillating signal at 1 13.
• the positive and negative oscillating signals at 1 12 and 1 13 generally have the same frequency as the oscillating signal at 1 1 1.
• the buffer 102 generally drives an amplitude of the positive and negative oscillating signals at 1 12 and 1 13 from rail to rail, i.e. between the same minimum and maximum levels, regardless of the amplitude of the oscillating signal at 1 1 1 .
• the positive and negative oscillating signals at 1 12 and 1 13 are supplied to a positive phase input ⁇ and a negative phase input ⁇ , respectively, of the charge pump 103.
• the charge pump 103 generally includes a plurality of series- connected charge pump stages (not shown), which use the positive and negative oscillating signals at 1 12 and 1 13 to add voltage to (or subtract from) an initial voltage (not shown) to produce an output current and voltage at 1 14.
• the output at 1 14 of the charge pump 103 is passed through the filter 104 to smooth it out to produce the charge pump regulator circuit output voltage Vout.
• the output voltage Vout is provided to a load circuit (not shown) of the overall electronic device of which the charge pump regulator circuit 100 is a part.
• the output voltage Vout is also provided through the scaler 107 to the op- amp 108 in a feedback loop that controls the current and voltage levels of the output voltage Vout.
• the scaler 107 produces a scaled voltage at 1 15 from the output voltage Vout.
• the scaled voltage is provided to the op-amp 108 along with a reference voltage Vref.
• the op-amp 108 produces the drive voltage at 1 10 for the inverter stages 109 based on the scaled voltage at 1 15 and the reference voltage Vref.
• the op-amp 108 decreases the drive voltage at 1 10.
• the frequency of the oscillating signal at 1 1 1 produced by the inverter stages 109 of the oscillator 101 decreases, thereby reducing the frequency of the positive and negative oscillating signals at 1 12 and 1 13.
• the voltage output at 1 14 by the charge pump 103 is reduced, thereby reversing the increase in the output voltage Vout.
• the output voltage Vout decreases too much, then the opposite effect occurs to reverse the decrease, in this manner, the output voltage Vout is generally maintained at about a desired voltage level within an acceptable tolerance or range of ripple or noise.
• a charge pump regulator circuit includes a voltage controlied oscillator and a plurality of charge pumps.
• the voltage controlled oscillator has a plurality of inverter stages connected in series in a ring.
• a plurality of oscillating signals is generated from outputs of the inverter stages.
• Each oscillating signal has a frequency and amplitude that are variable dependent on a variable drive voltage.
• Each oscillating signal is phase shifted from a preceding oscillating signal.
• Each charge pump is connected to a corresponding one of the inverter stages to receive the oscillating signal produced by that inverter stage.
• Each charge pump outputs a voltage and current. A combination of the currents thus produced is provided at about a voltage level to the load.
• Fig. 1 is a simplified schematic diagram of a prior art charge pump circuit.
• FIG. 2 is a simplified schematic diagram of an electronic device with a charge pump circuit incorporating an embodiment of the present invention.
• FIG. 3 is a simplified schematic diagram of an example charge pump for use in the charge pump circuit shown in Fig. 2 according to an embodiment of the present invention.
• FIG. 4 shows simplified example timing diagrams illustrating the performance of example inverter stages and an output of the charge pump circuit shown in Fig. 2 according to an embodiment of the present Invention.
• FIG. 5 shows simplified example timing diagrams illustrating the performance of an example inverter stage for use in the charge pump circuit shown in Fig. 2 according to an embodiment of the present invention.
• Fig. 6 is a simplified period vs. drive voltage graph illustrating the performance of an example voltage controlled ring oscillator for use in the charge pump circuit shown in Fig. 2 according to an embodiment of the present invention. Detailed Description of the Invention
• the present invention achieves an improved low noise output voltage (at least under some operating conditions) with a charge pump regulator circuit that has a voltage controlled oscillator and a plurality of charge pumps.
• the voltage controlled oscillator has a plurality of inverter stages connected in series in a ring. Each inverter stage produces an oscillating signal that is provided to a next one of the inverter stages. Each oscillating signal has a frequency and amplitude that are variable dependent on a variable drive voltage. (Alternatively, either the frequency or the amplitude, but not both, is variable.)
• Each charge pump is connected to a corresponding one of the inverter stages to receive the oscillating signal produced by that inverter stage.
• the charge pumps output a current at about a voltage level to a load.
• the present invention achieves an improved low noise output voltage (at least under some operating conditions) with a charge pump regulator circuit that has a voltage controlled oscillator and a plurality of charge pumps.
• the voltage controlled oscillator includes a plurality of inverter stages connected in series in a ring. Each inverter stage produces an oscillating signal that is provided to a next one of the inverter stages. Each oscillating signal is phase shifted from a preceding oscillating signal.
• the charge pumps are arranged in parallel. Each charge pump is connected to a corresponding one of the inverter stages to receive the oscillating signal produced by that inverter stage. An output of each charge pump is phase shifted from the outputs of other charge pumps. A combination of the currents thus produced is provided at about a voltage level to a load.
• the present invention achieves an improved low noise output voltage (at least under some operating conditions) with a method that involves generating a plurality of oscillating signals from outputs of inverter stages of a voltage controlled oscillator having a plurality of inverter stages connected in series in a ring. A frequency and/or amplitude of the oscillating signals is varied depending on a variable drive voltage applied to the inverter stages.
• the oscillating signals are provided as inputs to a plurality of charge pumps.
• a plurality of charge pump currents are generated at a voltage level from the oscillating signals.
• a combination of the charge pump currents is provided at the voltage level to a load.
• the electronic device 200 generally includes one or more charge pump regulator circuits 201 that provide power to a load circuit 202.
• the electronic device 200 may be any appropriate electronic device, such as a computer, a phone, a game console, a clock, an automobile control system or a networking device, among many others.
• the charge pump regulator circuit 201 produces power at a generally constant voltage level with a variable current, depending on the activity of the load circuit 202.
• the design of the charge pump regulator circuit 201 described below generally enables a relatively low level of noise in its output, particularly at lower power production levels, where noise can have a greater negative affect on the load circuit 202 in some situations.
• the electronic device 200 is a cell phone (or other similar device)
• the received signal strength can be low in power.
• the noise coupled to the load circuit 202 from the charge pump regulator circuit 201 can interfere with the received signal, thereby degrading the radio link. Therefore, it is generally desirable to have relatively low noise under such operating conditions.
• the present invention may also be used in many other situations.
• the charge pump regulator circuit 201 generally includes a voltage controlled ring oscillator 203, a plurality of charge pumps (a.k.a. voltage multipliers or voltage adders) 204, a filter 205 (e.g. resistor 206 and capacitor 207), a scaler 208 and an op-amp 209.
• the voltage controlled ring oscillator 203 generally includes a plurality of inverter stages 210 connected output-to-input in series in a ring. Each charge pump 204 corresponds to one of the inverter stages 210.
• the charge pump regulator circuit 201 generally does not require the high gain buffer 102 (Fig. 1 ) to provide the input to the charge pumps 204. Additionally, although the charge pump regulator circuit 201 includes more charge pumps 204 than does the prior art circuit 100, and although each charge pump 204 may have a similar geometry to that of the prior art charge pump 103, each charge pump 204 may have a physical size that is scaled down from that of the prior art charge pump 103 by a factor roughly equal to the number of the charge pumps 204. Therefore, the charge pump regulator circuit 201 may have a physical size that is comparable to, or even smaller than, that of the prior art circuit 100. Additionally, the energy used to power the multiple charge pumps 204 may be roughly comparable to that used to power the prior art charge pump 103 at similar power output levels.
• the inverter stages 210 are shown as simple inverters that output an inverted version of their input signal. (Alternatively, the inverter stages 210 may include additional components that produce both an inverted and non-inverted version of their input signal. Other forms of voltage controlled ring oscillators may also be acceptable.) Under power from a drive voltage received from the op-amp
• the response of the inverter stages 210 is to generate an oscillating signal (or series pulses) that propagates through each inverter stage 210 around in a ring.
• Each inverter stage 210 thus, produces approximately the same oscillating signal, except that each oscillating signal in the ring is inverted and phase shifted from the preceding oscillating signal. (The phase shifting is described below with respect to Fig. 4.)
• the phase shift is generally due to a response delay within each inverter stage 210.
• a frequency and amplitude of each oscillating signal and a duration of the delay that produces the phase shift are generally dependent on the voltage level of the drive voltage at 21 1 received from the op-amp 209.
• the oscillating signals are provided, not only to the next inverter stage 210 in the ring, but also to the charge pumps 204.
• Each inverter stage 210 thus, corresponds to one of the charge pumps 204.
• the charge pumps 204 may be any appropriate circuitry that may add or multiply voltage based on the frequency and amplitude of the oscillating signals received from the inverter stages 210. (An example circuit for the charge pumps 204 is described below with respect to Fig. 3. Other types of circuits for the charge pumps 204 are also possible.)
• the charge pumps 204 are generally arranged in parallel, with inputs connected to the outputs of the corresponding inverter stages
• each of the charge pumps 204 generally produces approximately the same current and voltage based on the frequency and amplitude of the oscillating signals and a relatively constant input voltage (not shown).
• the output current and voltage of each charge pump 204 contains some noise, ripple or jitter. The noise is at least partially caused by the oscillation of the oscillating signals. Since the multiple charge pumps 204 are each considerably smaller than the single prior art charge pump 103 (Fig. 1 ), however, the noise produced by each charge pump 204 is considerably smaller than the noise produced by the prior art charge pump 103 when producing a comparable amount of power. Additionally, since the oscillating signals are phase shifted from each other, the outputs of the charge pumps 204 are similarly phase shifted.
• the amplitude of the oscillating signals that drive the charge pumps 204 is variable, unlike the amplitude of the oscillating signal supplied to the prior art charge pump 103 (Fig. 1 ) from the high gain buffer 102.
• the high gain buffer 102 generally drives its output rail-to-raii, i.e. between the same maximum and minimum all the time, in order to properly drive the relatively larger prior art charge pump 103.
• the variability of both the amplitude and frequency of the oscillating signals for the charge pumps 204 generally enables a greater dynamic range for the outputs of the charge pumps 204 than that of the prior art charge pump 103.
• Both the amplitude and the frequency of the oscillating signals contribute to the level of noise in the outputs of the charge pumps 204. Therefore, when the amplitude of the oscillating signals for the charge pumps 204 is reduced, the level of noise in the outputs of the charge pumps 204 is also reduced, A reduced amplitude for the oscillating signals generally corresponds with a low power output for the overall charge pump regulator circuit 201 . Additionally, the reduced amplitude is generally combined with a reduced frequency, or increased cycle period, for the oscillating signals, which further aids in the reduction of noise at low power output. (The relationship between the amplitude and the frequency/period is described below with respect to Figs.
• the noise level may increase along with the amplitude and frequency of the oscillating signals, but generally remains relatively low compared to that of the prior art charge pump regulator circuit 100 at similar power levels. Additionally, many types of load circuits 202 can tolerate a greater amount of noise during higher power operations than at lower power operations. Therefore, the charge pump regulator circuit 201 may be ideally suited for use in designs that require lower noise at lower power consumption operations, such as, but not limited to, wireless communication receivers, as described above.
• the combined output at 212 of the charge pumps 204 is passed through the filter 205 to further smooth out the output voltage Vout of the overall charge pump regulator circuit 201.
• the output voltage Vout is supplied to the load circuit 202 to power at least some of the functions of the electronic device 200. These functions may vary or be turned on and off at different times, so the load placed on the charge pump regulator circuit 201 may vary. This load variation is generally detected and compensated for by a feedback loop involving the scaler 208 and the op-amp 209.
• the scaler 208 receives the output voltage Vout and scales it to a level that the op-amp 209 can handle.
• the op-amp 209 receives the scaled output voltage at 213 and a reference voltage Vref. Based on the scaled output voltage at 213 and the reference voltage Vref, the op-amp 209 produces the drive voltage at 21 1 for the inverter stages 210.
• the output voltage Vout is pulled down, causing the scaled output voltage at 213 to decrease relative to the reference voltage Vref, which causes the op-amp 209 to increase the drive voltage at 21 1 , which causes the inverter stages 210 to increase the frequency and amplitude of the oscillating signals, which causes the charge pumps 204 to increase their output, which increases the output voltage and current and brings the output voltage Vout back to the desired level.
• FIG. 3 An example charge pump (a.k.a. voltage multiplier or voltage adder) 300 that may be used as the charge pumps 204 is shown in Fig. 3.
• the charge pump 300 is shown and described for illustrative purposes only. Other types of charge pumps may also be used for the charge pumps 204, so it is understood that the present invention is not limited to this design, except if and where expressly stated.
• the example charge pump 300 generally includes an oscillating signal splitter 301 and two charge pump stages (or ceils) 302 and 303.
• the oscillating signal splitter 301 generally includes an inverter 304 and a delay buffer 305.
• the charge pump stages 302 and 303 generally include transistors 306, 307, 308 and 309 and capacitors 310 and 31 1.
• the oscillating signal splitter 301 generally converts or splits the oscillating signal received from the corresponding inverter stage 210 (Fig. 2) at 312 into a positive oscillating signal CLK and a negative oscillating signal CLK .
• the delay buffer 305 generates the positive oscillating signal CLK by delaying the incoming oscillating signal at 312 by approximately the same amount as the delay in the inverter 304, so the positive and negative oscillating signals CLK and CLK are approximately matched.
• the positive and negative oscillating signals CLK and CLK do not necessarily have to be exact inversions of each other.
• the inverter 304 and the dela buffer 305 are preferably driven by the same drive voltage at 21 1 (Fig. 2) from the op-amp 209 that drives the inverter stages 210. Additionally, the inverter 304 and the delay buffer 305 preferably have a similar construction as the inverter stages 210. As a result, the frequency and amplitude of the oscillating signals produced by the inverter stages
• the inverter stages 210 produce the oscillating signals in such a manner that either the frequency or amplitude is variable, but not both.
• either the charge pumps 204 or 300 may operate with only one of these parameters being variable, or the oscillating signals may pass through other components (e.g. the inverter 304 and the delay buffer 305) that produce both the frequency and amplitude as variable,
• the inverter stages 210 (Fig. 2) produce both the positive and negative osciiiating signals CLK and CLK and supply them to the charge pumps 204. in this case, the oscillating signal splitter 301 is not needed within the charge pump 300.
• the charge pump stages 302 and 303 are connected in series between a positive voltage node V+ and negative voltage node V-.
• the charge pump stages 302 and 303 are connected in series between a positive voltage node V+ and negative voltage node V-.
• step up or step down i.e. voltage add/subtract or voltage multiply
• the initial input voltage (or ground) is connected to the negative voltage node V-, and the output at 212 is connected to the positive voltage node V+.
• Each charge pump stage 302 and 302 then steps up the voltage from the initial input voltage (or ground) at the negative voltage node V- by an amount based on the frequency and amplitude of the positive and negative osciiiating signals CLK and CLK to produce the output voltage at the positive voltage node V+.
• the initial input voltage (or ground) is connected to the positive voltage node V+, and the output at 212 is connected to the negative voltage node V-.
• Each charge pump stage 302 and 302 then steps down the voltage from the initial input voltage (or ground) at the positive voltage node V+ by an amount based on the frequency and amplitude of the positive and negative osciiiating signals CLK and CLK to produce the output voltage at the negative voltage node V-, (The charge pump 300, thus, sources or sinks current depending on whether the output voltage is positive or negative.)
• the charge pump 300 is shown having two charge pump stages 302 and 303, it is understood that the present invention is not necessarily so limited. Instead, any number of charge pump stages may be used, generally depending on the level of the initial input voltage, the amount that each charge pump stage steps up/down the voltage and the desired level for the output voltage.
• charge pump 300 is shown operating based on the positive and negative oscillating signals CLK and CLK , it is understood that the present invention is not necessarily so limited. Instead, other types of charge pumps may be used, including those that operate with a single oscillating signal.
• Each oscillating signal 401 -405 for each inverter stage 210 is shown inverted and phase shifted by an amount A from the one that precedes if. (The first oscillating signal 401 is likewise inverted and phase shifted from the last oscillating signal 405.)
• the outputs of each charge pump 204 are similarly phase shifted, so that the combined output voltage Vout (graph 408) has relatively little noise.
• FIG. 5 An additional timing diagram 500 illustrating the dependence of the oscillating signals on the drive voltage at 21 1 (Fig. 2) is shown in Fig. 5.
• a ring oscillator period T vs. drive voltage Vdd response curve 800 for the inverter stages 210 is shown in Fig. 6.
• the drive voltage at 21 1 is relatively low (graph 501 , and left end of curve 600)
• the amplitude of the oscillating signals is relatively small and the frequency is relatively low (i.e. the period is relatively large).
• the drive voltage at 21 1 is relatively high (graph 502, and right end of curve 800)
• the amplitude of the oscillating signals is relatively large and the frequency is relatively high (i.e. the period is relatively small).
• embodiments of the present invention take advantage of this relationship to enhance the dynamic range of the charge pump regulator circuit 201 .

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• Engineering & Computer Science (AREA)
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• Dc-Dc Converters (AREA)
• Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)

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• 2012
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• 2013
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