CN102158085B - Digital automatic frequency-selecting direct current converter - Google Patents
Digital automatic frequency-selecting direct current converter Download PDFInfo
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- CN102158085B CN102158085B CN 201110058461 CN201110058461A CN102158085B CN 102158085 B CN102158085 B CN 102158085B CN 201110058461 CN201110058461 CN 201110058461 CN 201110058461 A CN201110058461 A CN 201110058461A CN 102158085 B CN102158085 B CN 102158085B
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Abstract
The invention belongs to the technical field of direct current converters, in particular discloses a digital automatic frequency-selecting direct current converter. The direct current converter mainly comprises a Buck circuit, a digital control circuit and an analog-to-digital converter (ADC), wherein the digital control circuit comprises a phase-locking loop, a digital compensator module, a dither structure digital pulse width modulator, a clock generating module, a nonlinear control module, a finite state machine control module, and the like. The digital automatic frequency-selecting direct current converter is realized in a digital way, the output voltage of the Buck circuit is monitored and controlled by the digital control circuit to form negative feedback loop control, a stable direct current voltage is output, the working frequency can be automatically selected and higher frequency can be maintained in a wide load range. The invention has the advantages of reducing the complexity of a system, being realized by a hardware description language, simplifying the design process and being better than an analog product in aspects of economy, reconfigurability and control precision.
Description
Technical field
The invention belongs to the direct current transducer technical field, the digital switch direct current transducer that is specifically related to use in the mobile device.
Background technology
Along with the progress at full speed of large scale integrated circuit technology, just constantly advance towards multi-functional, high performance direction based on battery powered mobile electronic equipment for consumption, but the thing followed is the system power dissipation that day by day increases.In order to improve the duration of equipment, the effect of high efficiency direct current transducer is most important.Generally, mobile device exists high capacity work and two kinds of mode of operations of low load standby.Take mobile phone as example, when being in talking state, mobile phone just is operated in the high capacity pattern, and when standby, then is operated under the low load model.Such characteristics have determined that direct current transducer need to all keep high conversion efficiency in a very wide loading range.
The direct current transducer of traditional pulse-width modulation (Pulse Width Modulation, PWM) mode can be kept very high efficient under high load condition; And under low loading condition, the shared ratio of the power consumption that drives along with switch power consumption and door is increasing, efficient along with load current reduce more and more lower.In order to solve the low efficiency problem under the low loading condition, usually need to adopt the multimode control program.Main multimode control program is to adopt the PWM mode to control under high load condition at present, adopts pulse frequency modulation (Pulse Frequency Modulation, PFM) mode to control under low loading condition.Adopt the direct current transducer of this multimode control program under low loading condition, to utilize PFM significantly to reduce switching frequency, thereby to have improved efficient.But multimode is controlled at the switch clock and drives lower work, can produce other sensitive chip in the mobile device to disturb, even directly affect its normal operation.So the direct current transducer rear class needs filtering usually, reduce electromagnetic interference (Electromagnetic Interference, EMI).Under the PWM pattern, the system switching frequency is fixed, and harmonic component can be carried out effective filtering also at the multiple place of fixed frequency; But under the PFM pattern, switching frequency is that the EMI circuit can't effectively be processed along with load current changes and wide variation.So in responsive occasion, the multimode direct current transducer still can forced working in the PWM pattern, efficient is lower.
Therefore, Tsz Yin Man etc. has proposed the scheme of a kind of select frequency automatically (Auto Selectable Frequency PWM, ASFPWM).Direct current transducer all uses the PWM mode to modulate between whole load region.In high load condition lower time, PWM adopts high operate frequency, and under low loading condition, the 1/N(N that operating frequency is reduced to high operate frequency is a fixing constant, usually gets 2n), reduced switching loss, solved problem inefficient under the low loading condition.Simultaneously, no matter still hanging down under the loading condition under high load condition, direct current transducer all is operated in several fixing preset switches frequencies, can effectively process in rear class by the rational EMI filter circuit of design parameter, significantly reduces the interference to other chips.
There is certain problem in the ASFPWM that adopts analog form to realize: 1, be disturbed easily; 2, when load current hour, there is certain error in current sampling circuit, can't accurately judge load current; 3, because when load changing, frequency is switched simultaneously, the system transients characteristic is relatively poor.
Summary of the invention
For overcoming the deficiencies in the prior art, the invention provides a kind of high accuracy number automatic frequency-selecting direct current converter.
The direct current transducer that adopts digital form to realize is not subject to the interference of external environment, and stability is high, and digital circuit is subjected to process deviation influence little, and rate of finished products is high.Because the limitation of current sampling circuit, the present invention proposes a kind of method of new estimation load current interval.The method judges that in conjunction with the duty cycle signals under Buck circuit working mode signal and the DCM pattern load current is interval, still can reach higher precision under low loading condition, has saved simultaneously current sampling circuit.For the transient response of system, add the nonlinear Control module in addition, can effectively reduce overshoot.
High accuracy number automatic frequency-selecting direct current converter provided by the invention, hardware comprise step-down Buck circuit, analog to digital converter ADC, digital control circuit.Wherein: digital control circuit links to each other with step-down Buck circuit, analog to digital converter ADC respectively; Analog to digital converter ADC links to each other with step-down Buck circuit; The three consists of feedback loop, the output of controlled hypotension Buck circuit voltage.Structure as shown in Figure 1.
Among the present invention, described step-down Buck circuit is an integrated circuit (IC) chip.It comprises a Vx point zero-crossing comparator.
Among the present invention, described digital control circuit comprises: phase-locked loop, clock generating module, finite states machine control module, Error processing module, digital compensator module, digital pulse-width modulator and nonlinear Control module.Its annexation is as follows: phase-locked loop links to each other with external clock Sys_clk signal, clock generating module respectively; The clock generating module links to each other with phase-locked loop, finite states machine control module, digital compensator module, digital pulse-width modulator respectively; The finite states machine control module links to each other with clock generating module, digital compensator module, Vx point zero-crossing comparator output signal respectively; The Error processing module links to each other with external digital reference voltage level VID_I signal, digital compensator module, analog to digital converter ADC respectively; The digital compensator module links to each other with clock generating module, Error processing module, finite states machine control module, digital pulse-width modulator respectively; Digital pulse-width modulator links to each other with clock generating module, digital compensator module, nonlinear Control module respectively; The nonlinear Control module links to each other with analog to digital converter ADC, digital pulse-width modulator module respectively.As shown in Figure 2.
Among the present invention, the output voltage of described step-down Buck circuit is converted to 8 digit numeric codes and is input in the digital control circuit after sampling through analog to digital converter ADC, is processed by digital control circuit.In digital control circuit, at first by the Error processing module 8 voltage digital codes and reference voltage digital code are subtracted each other, obtain the digital error signal between direct current transducer output voltage and the reference voltage; After this error signal process digital compensator module for compensating, be input in the digital pulse-width modulator, be converted to pulse-width signal by digital pulse-width modulator and export to the Buck circuit, so just consisted of a feedback loop, can the stable output direct voltage.
Among the present invention, described digital control circuit can be worked under several fixing frequencies; Can automatically select to be operated in some frequencies according to loading condition.Described digital control circuit also by finite states machine control module monitors mode of operation index signal and duty cycle signals, is judged loading condition, output control signal control clock generating module and digital compensator module.When load changes, adjust clock output by finite states machine control module controls clock generating module, automatic switchover loop operating frequency is exported control signal simultaneously to the digital compensator module, selects suitable compensating form.
In the described digital control circuit, the nonlinear Control module is used for improving the circuit transient response, and monitoring Error processing module output error signal is if this error signal exceeds the threshold range of setting, nonlinear Control module output 0 or 1 retracts output voltage rapidly near the reference voltage.
In the described digital control circuit, the clock generating module can produce several different clock frequencies according to finite states machine control module output control signal.
In the described digital control circuit, the digital compensator module can be carried out PID compensation or PI compensation according to finite states machine control module output control signal.
In the described digital control circuit, the digital pulse-width modulator module adopts the Dither structure.
Described digital control circuit can select FPGA or CPLD to realize.
The present invention adopts digital form to realize, and by digital control circuit the direct current transducer output voltage is monitored and controlled, the direct voltage of stable output, and by automatically selecting operating frequency, in wide loading range, keep higher efficient.The present invention has reduced the complexity of system, can realize with hardware description language, has simplified design cycle, is better than analog equipment from economical, reconfigurability and control precision aspect.
Description of drawings
Fig. 1 is the structured flowchart of high accuracy number automatic frequency-selecting direct current converter.
Fig. 2 is the concrete structure figure of high accuracy number automatic frequency-selecting direct current converter.
Fig. 3 is the flow chart of finite state controller.
Embodiment
The invention discloses a kind of high accuracy number automatic frequency-selecting direct current converter, mainly comprise step-down Buck circuit, digital control circuit, analog to digital converter modules A DC.Described digital control circuit is comprised of phase-locked loop, digital compensator module, dither structure high accuracy number pulse width modulator, clock generating module, nonlinear Control module and finite states machine control module etc.Its structure as shown in Figure 1.
High accuracy number automatic frequency-selecting direct current converter elementary cycle control principle is as follows: the output voltage V o of Buck circuit is converted to 8 digit numeric code input digit control circuits and processes after sampling through ADC.In digital control circuit, at first by the Error processing module 8 voltage digital codes and reference voltage digital code are subtracted each other, obtain the digital error signal between direct current transducer output voltage and the reference voltage; After this error signal process digital compensator module for compensating, be input in the digital pulse-width modulator, be converted to pulse-width signal by digital pulse-width modulator and export to the Buck circuit, so just consisted of a feedback loop, can the stable output direct voltage.
In the Buck circuit, designed a Vx point zero-crossing comparator.When the Vx zero passage, the output services mode indication signal is high, and expression Buck circuit enters the DCM pattern; As Vx not during zero passage, the output services mode indication signal is low, and expression Buck circuit working is in the CCM pattern.
Direct current transducer transfer function under CCM, the DCM is different, thus the digital compensator modular design two kinds of compensation ways respectively the loop of two kinds of mode of operations is compensated.In native system, when Buck circuit working during in the CCM pattern, adopt the PID mode to compensate, when being operated in the DCM pattern, adopt the PI mode to compensate, judge load current condition by FSM Controller after the output control signal select.
When load changes, mode of operation index signal and duty cycle signals by finite states machine control module (FSM Controller) monitoring Buck circuit, judge loading condition, control clock generating module (Clock Generator) is adjusted clock output, automatic switchover frequency loop.
Finite states machine control module Rule of judgment is as follows: when the mode of operation index signal was low, the Buck circuit working judged that in the CCM pattern load current is positioned at the high load currents interval; When the mode of operation index signal was high, the Buck circuit working was in the DCM pattern, and load current is lower, judged the concrete interval that load current is positioned at by duty ratio again.
Interval according to the load current of judging, finite states machine control module controls state transition is realized the automatic switchover of frequency.Finite states machine control module flow chart as shown in Figure 3.The IDLE state is system's idle condition, and the SOFT_START state is the soft start state of system when powering on, and PID, PI1, PI2, PI3 state are working state of system, separately corresponding operating frequency.IS1, IS2, IS3, IS4 are that the load current of Buck circuit is interval, and IS1〉IS2〉IS3〉IS4.
When system started, FSM at first entered the SOFT_START state, carried out soft start operation, and output voltage rises to reference voltage level gradually within the time of 2ms.After soft start was finished, system at first entered the PID state, carried out state transition according to the load current interval again.The supposing the system lowest operating frequency is f
0Load current is larger, and when being positioned at the IS1 interval, the finite states machine control module is in the PID state, and under this state, the Buck circuit work frequency is 8f
0, being in the CCM pattern, loop compensates with PID.When load current is reduced to gradually less than I
Th1After, the Buck circuit enters the DCM pattern, and system will jump to PI1, PI2, PI3 state, and loop adopts PI to compensate.PI1, PI2, PI3 state respectively corresponding load current are positioned at IS2, IS3, the operating state when IS4 is interval, and operating frequency reduces along with reducing of load current, is followed successively by 4f
0, 2f
0, f
0If the system load electric current is ascendant trend, the system mode jump procedure is opposite with jump procedure noted earlier, and operating frequency rises.
For preventing near the unnecessary redirect of state critical value, all can count frequency redirect condition before each redirect, satisfying the continuous several all after dates of state transition condition, system just can carry out the frequency redirect.Simultaneously, during the frequency redirect, system is usually located at transient process, and duty cycle signals is unstable.Therefore, the state after the frequency redirect is counted, only when the state after the redirect keep several periodic systems approach stable after, just the state transition condition is restarted counting.
If the minimum quantization voltage of digital pulse-width modulator is less than the minimum quantization voltage of analog to digital converter ADC, limit cycle may appear in system, and output voltage shakes.In native system, for satisfying the minimum quantization voltage conditions of digital pulse-width modulator, digital pulse-width modulator is got 10.
If adopt common attribute digital pulse-width modulator, then digital pulse-width modulator needs the clock of 4 GHz, is difficult to reach for circuit is realized.Therefore, digital pulse-width modulator selects the Dither structure to realize, adopt 4 Dither, after the 6 digit counter structures, clock only needs 256 MHz, is easy to realize.
In design of Compensator, for the acute variation that prevents duty ratio affects state transition, must be less with the bandwidth Design of compensator, but this can affect system's transient response, therefore, has added the nonlinear Control module.According to output voltage reference value V
RefSet two upper lower threshold value V
L, V
H, V
L=V
Ref– V
Th_gap, V
H=V
Ref+ V
Th_gap, V wherein
Th_gapBe the nonlinear Control interval.When analog to digital converter ADC output signal is positioned at V
L, V
HBetween the time, the output duty cycle pulse signal is the duty cycle pulse signal that digital compensator linear feedback loop produces.When analog to digital converter ADC output signal at interval V
L, V
HOutside, loop enters nonlinear Control: analog to digital converter ADC output signal is less than V
LThe time, duty cycle pulse signal output 1; Analog to digital converter ADC output signal is greater than V
HThe time, duty cycle pulse signal output 0.When output voltage exceeds threshold range, by this nonlinear Control mode, can retract as early as possible reference voltage, improve transient response.
The High Precision Automatic frequency-selective digital direct current transducer of the present invention's design, the operating frequency that under the different loads current condition, automaticallyes switch, the harmonic component under each operating frequency is fixed, and can effectively process by filter circuit, significantly reduces electromagnetic interference; Operating frequency is lower with the load current reduction, has all kept higher efficient in wide loading range; When load current generation saltus step, the nonlinear Control module has guaranteed that system's overshoot is less; Be applicable to require wide load, high efficiency, low-voltage overshoot, the environment of low electromagnetic interference.
Claims (8)
1. digital automatic frequency-selecting direct current converter, it is characterized in that: hardware comprises step-down Buck circuit, analog to digital converter ADC, digital control circuit; Wherein, described digital control circuit links to each other with described step-down Buck circuit, analog to digital converter ADC respectively; Described analog to digital converter ADC links to each other with step-down Buck circuit; The three consists of the output of feedback loop controlled hypotension Buck circuit voltage; Wherein:
Described step-down Buck circuit is an integrated circuit (IC) chip, wherein includes a Vx point zero-crossing comparator;
Described digital control circuit comprises: phase-locked loop, clock generating module, finite states machine control module, Error processing module, digital compensator module, digital pulse-width modulator and nonlinear Control module; Wherein annexation is as follows: phase-locked loop links to each other with external clock Sys_clk signal, clock generating module respectively; The clock generating module links to each other with phase-locked loop, finite states machine control module, digital compensator module, digital pulse-width modulator respectively; The finite states machine control module links to each other with clock generating module, digital compensator module, Vx point zero-crossing comparator output signal respectively; The Error processing module links to each other with external digital reference voltage level VID_I signal, digital compensator module, analog to digital converter ADC respectively; The digital compensator module links to each other with clock generating module, Error processing module, finite states machine control module, digital pulse-width modulator respectively; Digital pulse-width modulator links to each other with clock generating module, digital compensator module, nonlinear Control module respectively; The nonlinear Control module links to each other with analog to digital converter ADC, digital pulse-width modulator respectively.
2. digital automatic frequency-selecting direct current converter according to claim 1 is characterized in that: described digital control circuit, automatically select to be operated in certain frequency according to loading condition.
3. digital automatic frequency-selecting direct current converter according to claim 1, it is characterized in that: described digital control circuit, judge loading condition by finite states machine control module monitors mode of operation index signal and duty cycle signals, output control signal control clock generating module and digital compensator module.
4. digital automatic frequency-selecting direct current converter according to claim 1, it is characterized in that: described nonlinear Control module is used for improving the circuit transient response, monitoring Error processing module output error signal, if this error signal exceeds the threshold range of setting, nonlinear Control module output 0 or 1 retracts output voltage rapidly near the reference voltage.
5. digital automatic frequency-selecting direct current converter according to claim 1 is characterized in that: described clock generating module produces different clock frequencies according to the control signal of finite states machine control module output.
6. digital automatic frequency-selecting direct current converter according to claim 1 is characterized in that: described digital compensator module, carry out PID compensation or PI compensation according to the control signal of finite states machine control module output.
7. digital automatic frequency-selecting direct current converter according to claim 1 is characterized in that: described digital pulse-width modulator employing Dither structure.
8. digital automatic frequency-selecting direct current converter according to claim 1 is characterized in that: be designed with a Vx point zero-crossing comparator in described Buck circuit; When the Vx zero passage, the output services mode indication signal is high, and expression Buck circuit enters the DCM pattern; As Vx not during zero passage, the output services mode indication signal is low, and expression Buck circuit working is in the CCM pattern;
Described digital compensator modular design has two kinds of compensation ways respectively the loop of two kinds of mode of operations to be compensated: when Buck circuit working during in the CCM pattern, adopt the PID mode to compensate; When Buck circuit working during in the DCM pattern, adopt the PI mode to compensate; Selected by output control signal after the finite states machine control module judgement load current condition.
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| CN104092359B (en) * | 2014-07-29 | 2016-08-17 | 东南大学 | A kind of control cyclic system for multi-mode digital Switching Power Supply |
| CN104201887B (en) * | 2014-09-01 | 2017-03-01 | 矽力杰半导体技术(杭州)有限公司 | Zero adjustment circuit and the method excessively of buck convertor |
| ITUB20160548A1 (en) | 2016-02-08 | 2017-08-08 | St Microelectronics Srl | RESISTIVE SENSOR INTERFACE |
| CN116250376A (en) * | 2020-08-14 | 2023-06-09 | 赤多尼科两合股份有限公司 | Control circuit, LED driver and control method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101252311A (en) * | 2007-02-23 | 2008-08-27 | 英特尔公司 | Adaptive controller with mode tracking and parametric estimation for digital power converters |
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| JP3718830B2 (en) * | 2001-02-26 | 2005-11-24 | 株式会社日立製作所 | Power converter |
| TWI255088B (en) * | 2004-05-24 | 2006-05-11 | Anpec Electronics Corp | DC converting controller with mode-switching and over-current protection by using multifunctional pin and its method |
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| CN101252311A (en) * | 2007-02-23 | 2008-08-27 | 英特尔公司 | Adaptive controller with mode tracking and parametric estimation for digital power converters |
Non-Patent Citations (2)
| Title |
|---|
| 《An Auto-Selectable-Frequency Pulse-Width Modulator for Buck Converters with Improved Light-Load Efficiency》;Tsz Yin Man等;《ISSCC 2008》;20081231;第440-441，626页 * |
| Tsz Yin Man等.《An Auto-Selectable-Frequency Pulse-Width Modulator for Buck Converters with Improved Light-Load Efficiency》.《ISSCC 2008》.2008,第440-441，626页. |
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