CN103178718B - Digital-control constant-power DC/DC converter - Google Patents
Digital-control constant-power DC/DC converter Download PDFInfo
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Abstract
The invention discloses a low-cost digital-control constant-power DC/DC converter which comprises a flyback conversion circuit, a single chip microcomputer controller and a PWM (pulse width modulation) controller. A first input end of the single chip microcomputer controller is connected with a sampling end of a converter output voltage sampling circuit, a second input end of the single chip microcomputer controller is connected with a sampling end of a converter output current sampling circuit, and an output port of the single chip microcomputer controller is connected with a control port of the PWM controller; signals outputted by the PWM controller are used for controlling on and off of a switch tube of the flyback conversion circuit; and an output end of the single chip microcomputer controller is serially connected with a control voltage conversion circuit and is used for converting current control signals into current error signals, and output of the control voltage conversion circuit is used as a control signal for the PWM controller. The digital-control constant-current DC/DC converter has the advantages of low design cost of the circuits, short delay time of a digital feedback circuit and capability of precisely controlling output constant power.
Description
Technical Field
The invention relates to improvement of a constant-power DC/DC converter, in particular to a low-cost digital control constant-power DC/DC converter.
Background
The direct-current distributed power supply system has the advantages of high reliability, convenience in maintenance and the like, and is widely applied to the fields of aerospace, automobiles, ships, communication and the like. The intermediate bus converter, which is a key component of the distributed power system, generally operates in a constant power feedback mode. Unlike conventional voltage and current feedback control schemes, the constant power feedback scheme places higher demands on the control system.
Conventional constant power DC/DC converters are typically implemented using analog or all-digital control. After the analog control converter detects the output voltage and current signals, the voltage and current are multiplied through an analog multiplier to obtain a signal value which is in direct proportion to the output power, and the signal value is fed back to the front end to be compared with a reference power signal to generate an error control signal so as to control the duty ratio change of the switching tube. The disadvantage of the analog multiplier is that its inherent offset drift reduces the accuracy of power calculation, and the analog control has poor flexibility, and the adjustment of the output constant power value must change the parameters of the hardware circuit.
At present, the full digital control technology is gradually applied to a DC/DC switching power supply, and a feedback control loop adopts chips such as an ADC (analog to digital converter), a DSP (digital signal processor), a DAC (digital to analog converter) and the like to realize digitization. The full digital control mode realizes signal conversion, signal processing and PWM signal generation through the command of software codes, can easily complete the voltage and current detection and power calculation of the load, and realizes the constant power or variable power adjustment of a closed loop. The full digital control mode has high calculation precision and flexible control, and the output constant power value can be adjusted at will by changing the software code. The most significant disadvantage of the all-digital control method is the high cost of circuit design, because the control chip must use the digital chip with high bus frequency, such as DSP, etc., and the delay effect introduced by the ADC, DPWM, etc., also reduces the dynamic characteristics of the converter closed-loop system.
Disclosure of Invention
The invention aims to design a low-cost digital control constant-power DC/DC converter, the circuit adopts a combined control framework of a single chip microcomputer and a PWM power supply management chip, the sampling and calculation of output signals are realized by the low-cost single chip microcomputer chip, and PWM driving signals are realized by an analog chip. The design cost of the circuit is low, the analog chip outputs PWM driving signals, a feedback channel does not need to adopt a DPWM module, the delay time of a closed-loop control loop is reduced, and the dynamic characteristic of the system is improved.
The technical scheme adopted by the invention for realizing the purpose is as follows:
the invention provides a digital control constant power DC/DC converter, which comprises a flyback conversion circuit, a single chip microcomputer controller and a PWM controller; the first input end of the single chip microcomputer controller is connected with an output voltage sampling end of the flyback conversion circuit, the second input end of the single chip microcomputer controller is connected with an output current sampling end of the flyback conversion circuit, and an output port of the single chip microcomputer controller is connected with a control port of the PWM controller; and the output signal of the PWM controller is used for controlling the on and off of a switch tube in the flyback conversion circuit.
Further, the single chip microcomputer controller comprises an ADC module, a multiplier module, a compensator and a reference module; the ADC module is used for performing analog-to-digital conversion on the voltage sampling signal and the current sampling signal; the multiplier module is used for calculating the transient power value of the signal of which the output voltage and the current are subjected to analog-to-digital conversion; the reference module is used for storing a reference power value; the compensator is used for carrying out digital compensation on the power difference signal of the transient power value and the reference power value and outputting a current control signal.
Further, the converter output voltage sampling circuit adopts a resistance voltage division mode, and the output current sampling circuit adopts a current detection resistance mode.
The input end of the control voltage conversion circuit is connected with a current control signal output by the singlechip controller, the output end of the control voltage conversion circuit is connected with the control end of the PWM controller, and the control voltage conversion circuit is used for converting the current control signal output by the singlechip into a current error signal.
Further, the control voltage conversion circuit comprises an operational amplifier and an RC filter; the non-inverting input end of the operational amplifier is connected with an output current sampling signal; the inverting input end of the operational amplifier is connected with an output signal of the RC filter; and a feedback resistor is connected between the inverting input end and the output end of the operational amplifier.
Further, the RC filter includes a resistor and a capacitor (connected in series with each other); the RC filter is arranged between the single chip microcomputer controller and the operational amplifier and used for processing a current control signal output by the single chip microcomputer controller.
Furthermore, the singlechip controller adopts a low-cost 8-bit singlechip chip.
Further, the PWM controller employs a fixed frequency voltage mode controller.
Further, the single chip microcomputer controller is realized by adopting MC68HC908JK 3.
Further, the PWM controller is implemented using MC 33060A.
The invention has the advantages that: compared with the existing analog control circuit, the invention has the following advantages: 1) the calculation, comparison and compensation of the output power realize digitization, and the constant power control precision is higher; 2) the adjustment of the output constant power value is realized by changing the software code, the structure and the parameters of a hardware circuit do not need to be changed, and the design cost is reduced. Compared with the existing full digital control circuit, the invention has the following advantages: 1) the control circuit adopts a low-cost 8-bit singlechip chip, so that the design cost of a hardware circuit and a software program is reduced; 2) the PWM driving signal is generated by the analog PWM controller, and a feedback control loop does not need to adopt a DPWM module, so that the delay time of the closed-loop control loop is reduced, and the dynamic characteristic of a closed-loop system is improved.
Drawings
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings, in which:
fig. 1 is a schematic diagram of a switching power supply circuit according to an embodiment of the present invention;
fig. 2 is a block diagram of constant power closed loop control provided in the embodiment of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings; it should be understood that the preferred embodiments are illustrative of the invention only and are not limiting upon the scope of the invention.
Example 1
Fig. 1 is a schematic diagram of a switching power supply circuit provided in an embodiment of the present invention, and fig. 2 is a block diagram of constant power closed loop control provided in an embodiment of the present invention, as shown in the figure: the invention provides a digital control constant power DC/DC converter, which comprises a flyback conversion circuit, a single chip microcomputer controller, a PWM controller and a control voltage conversion circuit, wherein the flyback conversion circuit is connected with the single chip microcomputer controller through a power line; the first input end of the single chip microcomputer controller is connected with an output voltage sampling end of the flyback conversion circuit, the second input end of the single chip microcomputer controller is connected with an output current sampling end of the flyback conversion circuit, and an output port of the single chip microcomputer controller is connected with a control port of the PWM controller; and the output signal of the PWM controller is used for controlling the on and off of a switch tube in the flyback conversion circuit.
The single chip microcomputer controller comprises an ADC module, a multiplier module, a compensator and a reference module; the ADC module is used for performing analog-to-digital conversion on the voltage sampling signal and the current sampling signal; the multiplier module is used for calculating the transient power value of the signal of which the output voltage and the current are subjected to analog-to-digital conversion; the reference module is used for storing a reference power value; the compensator is used for carrying out digital compensation on the power difference signal of the transient power value and the reference power value and outputting a current control signal.
The circuit of the output voltage sampling end of the flyback conversion circuit adopts a resistance voltage division mode, and the circuit of the output current sampling end adopts a current detection resistance mode.
The input end of the control voltage conversion circuit is connected with a current control signal output by the singlechip controller, the output end of the control voltage conversion circuit is connected with the control end of the PWM controller, and the control voltage conversion circuit is used for converting the current control signal output by the singlechip into a current error signal.
The control voltage conversion circuit comprises an operational amplifier and an RC filter; the non-inverting input end of the operational amplifier is connected with an output current sampling signal; the inverting input end of the operational amplifier is connected with an output signal of the RC filter; a feedback resistor is connected between the inverting input end and the output end of the operational amplifier; the RC filter comprises a resistor and a capacitor (which are connected in series with each other); the RC filter is arranged between the single chip microcomputer controller and the operational amplifier and used for processing a current control signal output by the single chip microcomputer controller.
The single chip microcomputer controller adopts a low-cost 8-bit single chip microcomputer chip. The single chip microcomputer controller is realized by MC68HC908JK 3.
The PWM controller adopts a fixed frequency voltage mode controller. The PWM controller is implemented using MC 33060A.
Example 2
The single chip microcomputer controller in this embodiment is used as a control center U2 of a feedback loop, and an 8-bit single chip microcomputer MC68HC908JK3 is adopted. After voltage sampling signals Vout of the load impedance R are divided by a resistor R3 and a resistor R4, the voltage sampling signals Vout are input to an 8-bit ADC converter port PTB3 arranged in the single chip microcomputer; the load current signal Iout is collected by the current detection resistor R5 and then input to the ADC port PTB 2. The singlechip is used for calculating and analyzing the digital conversion value of the output voltage and current signal based on a constant power control algorithm, and a timer port PTD4 is used for outputting a current control signal Vcon. The control signal is a square wave signal, and is processed by an RC filter consisting of R6 and C5 to obtain a direct current control signal, namely the RC filter is equivalent to a DAC (digital-to-analog converter).
The current control signal Vcon and the output current sampling signal Iout are compared by an operational amplifier U3, and the generated error signal is input to a feedback control port of the PWM controller U1. The U1 adopts constant frequency PWM to manage the chip MC33060A, and the comparison of the error signal and the internal oscillating sawtooth wave of chip U1 produces the PWM drive signal, and the amplitude of error signal determines the duty cycle of PWM signal, and the signal frequency is produced by resistance R1 and electric capacity C4. When the output power needs to be adjusted, the U2 chip changes the parameter of the current control signal Vcon in real time, and the amplitude of the error signal changes, so that the duty ratio of the PWM driving signal is adjusted, and the load current is controlled to follow the reference current Iref. Therefore, after the single chip microcomputer detects the output voltage, the output current value is adjusted based on the current feedback mode, and the output power can be adjusted to be a set value.
The control block diagram of the DC/DC converter operating in constant power mode is shown in fig. 2. The load working voltage Vout and the current Iout are processed by the sampling circuit and then input to the single chip microcomputer control chip, and the built-in ADC module completes analog-to-digital conversion. The transient power Pout is calculated by a single chip microcomputer program and compared with a reference power value Pref, the obtained difference value Perr is adjusted by a digital compensator, a current control signal Vcon is output, the control signal realizes digital-to-analog conversion by a filter, the output analog signal is used as a feedback control signal of a PWM power supply management chip, the conduction duty ratio of a power circuit is changed, the output power of a regulating converter is kept consistent with the reference power, and therefore constant power closed-loop feedback control is achieved.
The transient power Pout is calculated by a single chip microcomputer program and compared with a reference power value Pref, the obtained difference value Perr is adjusted by a digital compensator to output a current control signal Vcon, the control signal realizes digital-to-analog conversion by a filter, the output analog signal is used as a feedback control signal of a PWM power supply management chip to change the conduction duty ratio of a power circuit, and the output power of the regulating converter is kept consistent with the reference power, so that constant-power closed-loop feedback control is realized, and a constant-power load shows a negative resistance characteristic in the working process, so that the DC/DC converter is equivalent to a current source, and the control of the output power can be realized based on a current feedback mode. Firstly, calculating a current reference signal according to the reference power and the current load voltage value:
（1）
wherein,indicates the current load reference current value,Represents the current load voltage value,Representing the reference power.
The error signal obtained by comparing the reference power and the real-time output power is as follows:
（2）
namely: (3)
whereinIs a current error signal.
Digital compensatorAnd (3) obtaining an output control signal by adopting a PI control algorithm:
(4)
wherein,to control the proportionality constant in the parameter,for integration constants in control parameters
Substituting formula (3) into formula (4) to obtain:
(5)
the parameter self-tuning PI control algorithm based on the current error signal is determined by the formula (5), and the control parameter needs to be adjusted on line in real time according to the current load voltage value:
(6)
wherein,to representkThe proportionality constant at the moment in time,to representkThe integral constant at the instant of time is,to representk-a proportionality constant at time 1,to representk-integration constant at time 1.
Therefore, the constant power control of the DC/DC converter is realized by adopting a current feedback control mode based on a parameter real-time self-tuning PI control algorithm.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and it is apparent that those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (9)
1. The constant power DC/DC converter of digital control, characterized by: the flyback converter comprises a flyback conversion circuit, a single-chip microcomputer controller and a PWM controller; the first input end of the single chip microcomputer controller is connected with an output voltage sampling end of the flyback conversion circuit, the second input end of the single chip microcomputer controller is connected with an output current sampling end of the flyback conversion circuit, and an output port of the single chip microcomputer controller is connected with a control port of the PWM controller; the output signal of the PWM controller is used for controlling the on and off of a switch tube in the flyback conversion circuit;
the input end of the control voltage conversion circuit is connected with the current control signal output by the singlechip controller, the output end of the control voltage conversion circuit is connected with the control end of the PWM controller, and the control voltage conversion circuit is used for converting the current control signal output by the singlechip into a current error signal.
2. The digitally controlled constant power DC/DC converter of claim 1, wherein: the single chip microcomputer controller comprises an ADC module, a multiplier module, a compensator and a reference module; the ADC module is used for performing analog-to-digital conversion on the voltage sampling signal and the current sampling signal; the multiplier module is used for calculating the transient power value of the signal of which the output voltage and the current are subjected to analog-to-digital conversion; the reference module is used for storing a reference power value; the compensator is used for carrying out digital compensation on the power difference signal of the transient power value and the reference power value and outputting a current control signal.
3. The digitally controlled constant power DC/DC converter of claim 1, wherein: the converter output voltage sampling circuit adopts a resistance voltage division mode, and the output current sampling circuit adopts a current detection resistance mode.
4. The digitally controlled constant power DC/DC converter of claim 1, wherein: the control voltage conversion circuit comprises an operational amplifier and an RC filter; the non-inverting input end of the operational amplifier is connected with an output current sampling signal; the inverting input end of the operational amplifier is connected with an output signal of the RC filter; and a feedback resistor is connected between the inverting input end and the output end of the operational amplifier.
5. The digitally controlled constant power DC/DC converter of claim 4, wherein: the RC filter comprises a resistor and a capacitor which are connected in series; the RC filter is arranged between the single chip microcomputer controller and the operational amplifier and used for processing a current control signal output by the single chip microcomputer controller.
6. The digitally controlled constant power DC/DC converter of claim 1, wherein: the single chip microcomputer controller adopts a low-cost 8-bit single chip microcomputer chip.
7. The digitally controlled constant power DC/DC converter of claim 1, wherein: the PWM controller adopts a fixed frequency voltage mode controller.
8. The digitally controlled constant power DC/DC converter of claim 1, wherein: the single chip microcomputer controller is realized by MC68HC908JK 3.
9. The digitally controlled constant power DC/DC converter of claim 1, wherein: the PWM controller is implemented using MC 33060A.
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| CN103731033A (en) * | 2013-12-19 | 2014-04-16 | 山东艾诺仪器有限公司 | Wide-range DC power supply with constant power output characteristic |
| CN103997215A (en) * | 2014-05-13 | 2014-08-20 | 重庆大学 | Numerically-controlled power-adjustable DC/DC converter |
| CN105610302B (en) * | 2014-11-24 | 2020-04-07 | 中兴通讯股份有限公司 | Power control method and device |
| CN105259970A (en) * | 2015-08-14 | 2016-01-20 | 天津市三源电力设备制造有限公司 | Simple maximum power point control circuit for solar cell panel |
| CN105406723B (en) * | 2015-12-24 | 2018-09-18 | 杭州士兰微电子股份有限公司 | Constant-power control circuit and the drive system for including the constant-power control circuit |
| CN107479608A (en) * | 2017-09-18 | 2017-12-15 | 东莞博力威电池有限公司 | A kind of circuit for controlling output constant current |
| CN109460106A (en) * | 2018-08-21 | 2019-03-12 | 山东荣泰感应科技有限公司 | The adaptive power adjustment module and method that intermediate frequency furnace power changes with load |
| CN110083194A (en) * | 2019-06-06 | 2019-08-02 | 西安拓尔微电子有限责任公司 | A kind of circuit and its implementation of the electronic cigarette of achievable constant power output |
| CN110492744B (en) * | 2019-08-19 | 2020-09-22 | 华南理工大学 | Constant power load control method and circuit applied to DC-DC converter |
| CN110896279B (en) * | 2019-10-12 | 2022-12-23 | 深圳市伟鹏世纪科技有限公司 | LED emergency power supply constant power output circuit and working method |
| CN115912936B (en) * | 2023-01-03 | 2023-06-06 | 成都智融微电子有限公司 | Flyback switching power supply circuit, flyback switching power supply control method and power supply equipment |
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| CN101304627A (en) * | 2008-05-23 | 2008-11-12 | 许建炳 | Constant power control method for electric ballast of high-strength air discharge lamp |
| CN201417403Y (en) * | 2009-04-01 | 2010-03-03 | 西南交通大学 | Constant power control device of switch power supply |
| CN201657471U (en) * | 2010-01-21 | 2010-11-24 | 中国电子为华实业发展有限公司 | Constant-power control circuit |
| CN101909391B (en) * | 2010-08-10 | 2013-07-31 | 浙江大学 | Phase-controlled dimming LED drive and driving method thereof |
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