CN110784104B - PID control circuit of DC-DC switching power supply - Google Patents

PID control circuit of DC-DC switching power supply Download PDF

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CN110784104B
CN110784104B CN201910950026.5A CN201910950026A CN110784104B CN 110784104 B CN110784104 B CN 110784104B CN 201910950026 A CN201910950026 A CN 201910950026A CN 110784104 B CN110784104 B CN 110784104B
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error pulse
error
pulse signal
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CN110784104A (en
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陈宇
陈迪畅
钟坤
康勇
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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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
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters

Abstract

The invention discloses a PID control circuit of a DC-DC switch power supply, belonging to the technical field of switch power supplies, the control circuit comprises: the device comprises a delay link, an error pulse generation link, an integral differential pulse generation link, a phase-shifting carrier generation link and a proportional integral differential pulse combination link. The invention generates pulse width signals after comparing the output voltage of the power circuit with the carrier, and realizes the control strategy by a logic operation method, so that the signals in the control circuit are basically transmitted in a pulse mode, compared with analog control, the circuit of the invention is not easily influenced by the drift of device parameters, and the control effect is similar to digital control; meanwhile, the logic operation of the pulse width in the circuit is simple, can be directly realized through a logic gate, does not need to adopt a digital processor, is compared with digital control, and has low cost.

Description

PID control circuit of DC-DC switching power supply
Technical Field
The invention belongs to the field of switching power supplies, and particularly relates to a PID control circuit of a DC-DC switching power supply.
Background
With the development of science and technology and the improvement of consumption level, more and more mobile devices are applied to daily life, such as smart phones, notebook computers, tablet computers, mobile wearable devices and the like. Most of these mobile devices require a dc power source, and thus have a large demand for a dc power converter. Compared with a linear power supply, the DC-DC switching power supply has low loss, small volume and high efficiency, and is widely applied. The design of the controller has great relation with the performance of the DC-DC switching power supply, and simultaneously, the design and manufacturing cost of the DC-DC switching power supply is influenced to a certain extent, so that the controller has important research value.
The control of the DC-DC switching power supply can be divided into analog control and digital control: the analog control is to build a control circuit by using an analog device, the control strategy is realized by the analog circuit, and the performance of the device used by the circuit and the topology of the circuit determine the quality of the control effect. For example, the invention patent "a advanced-interactive-derivative (PID) analog controller and a method for testing a PID analog controller of a DC/DC converter", publication No. EP2741408, publication No. 2018, 5, 16, proposes a PID analog control based on a DC-DC converter, and a control loop of the PID analog control is formed by a feedback network of an Operational Transconductance Amplifier (OTA) and a PID analog controller; the invention discloses a BUCK controller and a control method of output voltage, and provides a BUCK circuit-based analog control mode for improving the transient response capability of a circuit in publication No. CN106899210B, publication No. 2019, 2 and 26. Analog control has the advantage of low cost and is therefore of great importance in many applications where the cost requirements are stringent. The analog control has the disadvantages that the device is greatly influenced by the environment, the parameter drift of the device can cause a circuit to generate large errors, and the control effect is relatively poor.
The digital control is a control system taking a digital processing chip as a core, a control strategy is stored in the digital processing chip in a program form, and the program can be operated only by a small amount of peripheral circuits so as to realize the required control function. For example, the invention provides a digital PID controller for controlling a DC-DC converter in the invention patent of PID based controller for DC-DC converter with post-processing filters, publication No. US2006023479, published 2006, 2.2.2.2006, the invention converts analog voltage into digital signal through an analog-to-digital converter, obtains error signal through a differential circuit, processes the error signal through a digital compensator, and finally obtains a switch control signal; the invention discloses an adaptive control system of a Boost type DC-DC converter, which is disclosed in patent publication No. CN108539978A, published in 2018, 9 and 14.8.A self-adaptive control system of the Boost type DC-DC converter is provided. The invention discloses a vehicle-mounted DC/DC power supply digital control device based on a DSP (digital signal processor), which is disclosed in the patent of vehicle-mounted DC/DC power supply digital control device with the publication number of CN108880267A, publication number of 2018, 11 and 13. The digital control is digital quantity because of its control signal, so it can not cause large error because of parameter drift of device, and can implement PWM modulation at the same time, and its circuit is simple. However, the price of the digital processing chip is high, especially the price of the digital processing chip with high requirements for operation and storage is very high compared with that of the analog device, so the cost of the digital control is high.
In summary, both digital control and analog control have their own advantages, but also have their own disadvantages. The analog control has the disadvantages that the device is greatly influenced by the environment, the parameter drift of the device can cause a circuit to generate large errors, and the control effect is relatively poor. The digital control is not influenced by the drift of device parameters; the digital processing chip is expensive, and especially the digital processing chip with high operation and storage requirements is very expensive compared with an analog device, so that the cost of digital control is high.
Disclosure of Invention
In view of the above defects or improvement needs in the prior art, the present invention provides a PID control circuit of a DC-DC switching power supply, which aims to reduce the influence of device parameter drift on the control circuit, so as to improve the control effect and reduce the control cost.
To achieve the above object, the present invention provides a PID control circuit of a DC-DC switching power supply, comprising: a delay link, an error pulse generation link, an integral differential pulse generation link, a phase-shifting carrier generation link and a proportional integral differential pulse combination link;
output voltage U of power circuitoOutputting the output voltage U of the previous switching period through the time delay linkodWith the output voltage U of the first two switching cyclesodd；
The output voltage U of the power circuitoOutput voltage U of the previous switching cycleodOutput voltage U of the first two switching cyclesoddReference voltage UrefAnd a preset carrier c1The output of the error pulse generating link comprises an error pulse signal P1 at the current moment, an error pulse signal P2 in the previous period, an error pulse signal P3 in the previous two periods and a reference pulse vref；
Said reference pulse vrefThrough the phase-shift carrier generation link, a reference carrier c is generated2；
Error pulse signal P1 at present time, previous timeError pulse signal P2 of one period, error pulse signal P3 of the first two periods and reference carrier c2The integral differential pulse generation unit and the integral differential pulse generation unit are used as the input of the integral differential pulse generation unit together, and the output of the integral differential pulse generation unit is an integral differential pulse vID；
Said integral differential pulse vIDThe error pulse signal P1 at the current moment is used as the input of the PID combination link, and the output of the PID combination link is the PID regulation pulse signal v for controlling the on-off of the DC-DC converter switch tubePIDTo regulate the output voltage of the DC-DC converter.
Further, the error pulse generating unit comprises a plurality of error pulse subunits; the error pulse subunits respectively generate an error pulse signal P1 at the current moment, an error pulse signal P2 in the previous period and an error pulse signal P3 in the previous two periods; each error pulse signal comprising a positive error pulse verr+And negative error pulse verr-；
The logic expression of the error pulse subunit generating the error pulse signal P1 at the current time is:
Figure BDA0002225337080000041
wherein v isrefIs a reference voltage UrefAnd a preset carrier c1Comparing to obtain a square wave signal; v. ofoIs the output voltage U of the power circuitoAnd a preset carrier c1Comparing to obtain a square wave signal;
the logic expression of the error pulse subunit generating the error pulse signal P2 of the previous cycle is:
Figure BDA0002225337080000042
wherein v isodFor the output voltage U of the preceding switching cycleodAnd a preset carrier c1Square waves are obtained after comparison;
the logic expression of the error pulse subunit generating the error pulse signal P3 of the first two cycles is:
Figure BDA0002225337080000043
wherein v isoddFor the output voltage U of the first two switching cyclesoddAnd a preset carrier c1And (5) comparing the obtained square waves.
Further, the pulse width of the error pulse signal P1 at the current time is equal to the reference voltage UrefAnd the output voltage U of the power circuitoProportional to the difference of (a); the pulse width of the error pulse signal P2 in the previous period and the reference voltage UrefAnd the output voltage U of the previous switching cycleodProportional to the difference of (a); the pulse width of the error pulse signal P3 of the first two periods and the reference voltage UrefAnd the output voltage U of the first two switching cyclesoddIs proportional to the difference in (c).
Further, the reference carrier c2And a preset carrier c1Are all equal to the switching period, and the reference carrier c2Is advanced by the predetermined carrier c1Leading phase with said reference pulse vrefProportional to the pulse width of; the preset carrier c1Is a sawtooth wave.
Furthermore, the phase-shift carrier generation link comprises a triode common collector circuit module, a high-pass filtering module, a constant current source module and a capacitor discharging module.
Furthermore, the integral differential pulse generation link comprises a constant current charging and discharging circuit with a plurality of capacitors.
Further, the logic expression of the pid pulse combination element is as follows:
Figure BDA0002225337080000051
further, the delay link is an LRC delay circuit.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
(1) the invention generates pulse width signals after comparing the output voltage of the power circuit with the carrier, and realizes the control strategy by a logic operation method, so that the signals in the control circuit are basically transmitted in a pulse mode, compared with analog control, the circuit of the invention is not easily influenced by the drift of device parameters, and the control effect is similar to digital control; meanwhile, the logic operation of the pulse width in the circuit is simple, can be directly realized through a logic gate, does not need to adopt a digital processor, is compared with digital control, and has low cost.
(2) The control circuit of the invention is composed of a triode, a comparator and a logic gate, and can be simply integrated on a circuit chip under the existing process level, therefore, the control circuit of the invention has the advantage of convenient integration.
Drawings
FIG. 1 is a block diagram of a control circuit of a DC-DC switching power supply;
FIG. 2 is an overall architecture diagram of an example of an application of a control circuit of a DC-DC switching power supply;
FIG. 3 is a circuit diagram of a delay link;
FIGS. 4(a) -4 (b) are waveform diagrams of positive and negative error pulses generated in the error pulse generation link;
FIG. 5 is a circuit diagram of an error pulse subunit for generating an error pulse signal P1 at the current time;
FIG. 6 is a circuit diagram of an integral differential pulse generation element;
FIG. 7 is a circuit diagram of a phase-shifted sawtooth wave generation link;
FIG. 8 is a waveform diagram of the operation of the phase-shifted sawtooth wave generating circuit;
fig. 9 is a circuit diagram of a pid pulse combination unit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a control circuit of a DC-DC converter based on a PID control mode, which is mainly used for controlling the DC-DC converter in the conventional application occasions by fusing PID control and pulse width modulation together through circuit design and adopting a logic method for control. Compared with the traditional pure analog PID control and digital PID control, the method provided by the invention is less influenced by the drift of device parameters, the control effect is similar to that of digital control, and the circuit cost is low.
Referring to fig. 1, the present invention provides a PID control circuit of a DC-DC switching power supply, including: a time delay link, an error pulse generation link, an integral differential pulse generation link, a phase shift carrier generation link and a proportional integral differential pulse combination link;
output voltage U of power circuitoOutputting the output voltage U of the previous switching period through the time delay linkodWith the output voltage U of the first two switching cyclesodd(ii) a Output voltage U of power circuitoOutput voltage U of the previous switching cycleodOutput voltage U of the first two switching cyclesoddReference voltage UrefAnd a preset carrier c1The output of the error pulse generation link comprises an error pulse signal P1 at the current moment, an error pulse signal P2 in the previous period, an error pulse signal P3 in the previous two periods and a reference pulse vref(ii) a Reference pulse vrefThrough the phase-shift carrier generation link, a reference carrier c is generated2(ii) a An error pulse signal P1 at the current moment, an error pulse signal P2 in the previous period, an error pulse signal P3 in the previous two periods and a reference carrier c2The integral differential pulse is used as the input of the integral differential pulse generating link, and the output of the integral differential pulse generating link is the integral differential pulse vID(ii) a Integral differential pulse vIDError pulse of current timeThe impulse signal P1 is used as the input of the PID combination link, the output of the PID combination link is the PID regulation impulse signal v for controlling the on-off of the DC-DC converter switch tubePIDTo regulate the output voltage of the DC-DC converter.
The application of the method of the invention will be described in connection with a Buck circuit based DC-DC converter as shown in fig. 2. As in U of FIG. 2iIs the input voltage of Buck circuit, UoThe Buck circuit is composed of a switch tube S, a diode D, an inductor L and a capacitor C, and a resistor R is used for outputting voltage of the power circuitLThe switch tube S is connected with a diode D and an inductor L as a load, the other end of the diode D is grounded, and the other end of the inductor L is connected with a capacitor C and a load resistor RLCapacitor C and load resistor RLAnd the other end of the same is grounded. The control circuit samples the output of the power circuit through the resistance voltage-dividing network, one end of the resistance voltage-dividing network is connected with the output end of the power circuit, the other end of the resistance voltage-dividing network is grounded, and the resistance value of the resistance voltage-dividing network is far greater than that of the load resistor, so that the influence of the resistance voltage-dividing network on the load of the power circuit can be ignored. It should be noted that the output voltage U of the power circuit in the present inventionoThe total output voltage of the DC-DC converter power circuit is divided by a large resistor and then is transmitted to the voltage of the input end of the whole control circuit. Input of control system divides UoIn addition, an artificially set reference voltage U is also requiredrefAnd a preset carrier c1As input, a reference voltage UrefIs generally set to UoPresetting carrier c1Set as a sawtooth wave.
The construction process of each link in the control circuit is as follows:
(1) a time delay link; since a differential link is used in the subsequent PID adjustment, the output voltage U of the power circuit needs to be adjustedoThe delayed signal is used as the input of a control system, and the embodiment of the invention realizes the U pair through an LRC delay circuitoOne switching cycle and two switching cycles are delayed, respectively. The circuit of the delay link is shown in fig. 3, and comprises an inductor L, a capacitor C and a resistor R; an end of the inductor L is connected with an input signal UoThe other end is connected with a capacitor C andand resistance R. The transfer function of the circuit is:
Figure BDA0002225337080000071
delaying a signal in the time domain by t according to the Laplace transform0Equivalent to multiplication by e ^ (-st) in the frequency domain0) And (5) linking. The sum of the transfer functions e ^ (-st)0) The second-order approximate forms of Taylor expansion in the link are consistent, and the function of delaying one switching period and two switching periods of an output signal can be realized by reasonably designing the RLC parameters of the circuit.
(2) An error pulse generation step; taking the example of generating the error pulse signal P1 at the current time as an example, the control logic is:
for positive error pulses verr+The waveform diagram of the output is shown in fig. 4 (a): when reference pulse vrefIs high level and outputs a voltage pulse voAlso high, positive error pulse verr+Is low level; when reference voltage pulse vrefIs at a low level and outputs a voltage pulse voAlso low, positive error pulse verr+Is low level; when reference voltage pulse vrefIs at a low level and outputs a voltage pulse voAt a high level, positive error pulses verr+Is at a high level; when reference voltage pulse vrefIs at a low level and outputs a voltage pulse voAt a high level, positive error pulses verr+Is at a high level; and a reference voltage pulse vrefIs high level and outputs a voltage pulse voThe low level is not possible;
for negative error pulses verr-The waveform diagram of the output is shown in fig. 4 (b): when reference pulse vrefIs high level and outputs a voltage pulse voAlso high, negative error pulses verr-Is low level; when reference voltage pulse vrefIs at a low level and outputs a voltage pulse voAlso low level, negative error pulse verr-Is also low; when reference voltage pulse vrefIs high level and outputs a voltage pulse voAt the low level of the voltage, the voltage is low,negative error pulse verr-Is at a high level; because of the generation of negative error pulses verr-Provided that U isrefLess than UoReference voltage pulse vrefIs low level and outputs a voltage pulse voThe case of high level also does not exist, and the negative error pulse is unknown. Thus, the logical expression is:
Figure BDA0002225337080000081
wherein v isrefIs a reference voltage UrefAnd a preset carrier c1Comparing to obtain a square wave signal; v. ofoIs the output voltage U of the power circuitoAnd a preset carrier c1Comparing to obtain a square wave signal; since the error signal is divided into a positive error signal and a negative error signal, P1, P2, and P3 actually include two signals, respectively, and the positive error pulse is v in the case of P1 as an exampleerr+Negative error pulse is verr-；
Similarly, the logic expression of the error pulse subunit generating the error pulse signal P2 of the previous period is:
Figure BDA0002225337080000091
wherein v isodFor the output voltage U of the preceding switching cycleodAnd a preset carrier c1Square waves are obtained after comparison;
the logic expression of the error pulse subunit generating the error pulse signal P3 of the first two cycles is:
Figure BDA0002225337080000092
wherein v isoddFor the output voltage U of the first two switching cyclesoddAnd a preset carrier c1And (5) comparing the obtained square waves.
In summary, the pulse width of the error pulse signal P1 at the current time is equal to the reference voltage UrefAnd the output voltage U of the power circuitoProportional to the difference of (a); the pulse width of the error pulse signal P2 in the previous period and the reference voltage UrefAnd the output voltage U of the previous switching cycleodProportional to the difference of (a); the pulse width of the error pulse signal P3 of the first two periods and the reference voltage UrefAnd the output voltage U of the first two switching cyclesoddIs proportional to the difference in (c).
The error pulse generating link comprises a plurality of error pulse subunits, and each error pulse subunit respectively generates an error pulse signal P1 at the current moment, an error pulse signal P2 in the previous period and an error pulse signal P3 in the previous two periods; taking the error pulse subunit generating the error pulse signal P1 at the current time as an example, the circuit shown in fig. 5 includes two comparators, two not gates, and two and gates. In practical application, the circuit structure is not limited, and the logic relationship is satisfied.
(3) An integral differential pulse generation link; a PID control also requires the presence of integrating and differentiating elements, i.e. integrating and differentiating the error signal, in order to obtain integral and differential regulation of the PID regulation. The input positive and negative error pulses are subjected to integration of the error pulses by a constant current source to a capacitor charge-discharge circuit, the capacitor is charged with constant current when the positive error pulses are at a high level, and the capacitor is discharged with constant current when the negative error pulses are at a high level, so that the integration of the errors is realized. Defining the error of the kth switching period as e [ k ], then the error of the previous switching period is e [ k-1], the error of the previous two switching periods is e [ k-2], realizing secondary differentiation by constructing e [ k ] -2e [ k-1] + e [ k-2], realizing integration once by constant current charging and discharging of a capacitor, finally realizing differentiation, and sharing an integration capacitor and an integration link used by the differentiation link, so that the integration link and the differentiation link are naturally combined together, and a circuit is not required to be combined subsequently.
The core circuit for constructing the above functions is a constant current charging and discharging circuit of a capacitor, the circuit of the constant current charging and discharging circuit is shown in fig. 6, Q2 is an NPN triode, and when v is greater than v, the constant current charging and discharging circuit is a capacitor, and the NPN triode is a capacitor, so that the capacitance of the constanterr+At high, the emitter junction is forward biased, the collector junction is reverse biased, and Q2 is turned on, so that Q1 also satisfies that the emitter junction is positiveThe conduction condition of biased, collector junction reverse biased, Q1 conducting, current through diode D1 charges capacitor C1, uCThe voltage rises linearly. When v iserr+When the voltage is low, the base and emitter potentials of the Q2 are both the reference ground potential, the Q2 is turned off, the emitter and base potentials of the Q1 are equal, and both the emitter and base potentials are the power supply voltage, so that the Q1 is also turned off, no current flows through the Q1 due to the unidirectional conduction property of the diode, and if the Q3 is also turned off at the moment, u is also turned offCThe potential remains unchanged, and if Q3 is turned on, uCThe potential decreases linearly. In the same way, when verr-When the voltage is high, Q5 is conducted, Q4 is conducted, Q3 also meets the conducting condition, Q3 is conducted, C1 discharges through a diode D2, the voltage linearly decreases, when verr-is low, Q5 is turned off, the base and emitter potentials of Q4 are equal, Q4 is turned off, Q3 is also turned off, Q3 has no current flowing, if Q1 is conducted, C1 charges through a diode D1, the voltage on the C1 linearly increases, if Q1 is turned off, the voltage across C1 is kept unchanged, the amplification factor of a triode Q1 is defined as β, and the current amplification characteristic of the triode per se has the characteristic that the voltage is unchanged
Figure BDA0002225337080000101
When disturbance exists outside, the current of the branch of the diode D1 is increased, the voltage drop of the resistor R1 is increased, and the voltage change amount △ v of the resistor R1R1As a positive, the current change △ i flowing between the two stages ec of the transistor Q1 can be obtained according to the equation (1)ecNegative, therefore, the current in the branch of the diode D1 decreases, and conversely, when disturbance exists outside, the current in the branch of the diode D1 decreases, △ vR1Being negative, △ i can be obtained according to equation (1)ecPositive, the diode D1 branch current increases. Therefore, the currents of the branches D1 and D2 are constant when corresponding signals are provided, and the current steady-state values are as follows:
Figure BDA0002225337080000111
the whole working process of the whole circuit module is as follows: when v iserr+Is at a high level, and whenverr-When the voltage is low level, the power supply charges the capacitor C1, and the voltage at the two ends of the C1 rises; on the contrary, when v iserr+Is low, and when v iserr-At high, the capacitor discharges and the voltage across C1 drops. When v iserr+And verr-When the voltage across the capacitor is high, the voltage across the capacitor rises and falls, and the current magnitude relation of Q1 and Q3 is related, and when the current flowing through Q1 is large, the capacitor is charged, and the voltage across the capacitor rises; when the current flowing through Q3 is large, the capacitor discharges and the voltage across the capacitor decreases. E [ k ] is realized by three same capacitor constant-current charging and discharging circuit modules]-2e[k-1]+e[k-2]The function of the capacitor is that the voltage of the capacitor is the result of the combined action of integral and differential regulation through the integral action of the capacitor. And comparing the capacitor voltage with the phase-shifted sawtooth wave carrier to obtain integral differential pulse.
(4) A phase-shift carrier generation step; the circuit of the circuit is shown in fig. 7 and comprises a triode common collector circuit module, a high-pass filtering module, a constant current source module and a capacitor discharging module. The triode common collector circuit consists of R3, R4, R5 and a triode Q2; the high-pass filtering module consists of a filtering capacitor C1 and a resistor R6; the constant current source module consists of a voltage regulator tube ZD1, resistors R1, R2 and a triode Q1; the capacitor discharge module consists of resistors R7 and R8 and a triode Q3; the input signal of the circuit is square wave pulse obtained by comparing reference voltage and sawtooth wave carrier, and the output signal is phase-shifted sawtooth wave. The main process of generating the sawtooth wave is as follows: the capacitor is charged with constant current, the voltage of the capacitor rises in a slope from zero, a discharge loop is connected at a certain moment, the resistance value of the discharge loop is very small, the discharge time of the capacitor is extremely short, and the voltage of the capacitor is rapidly reduced to zero. The charging process and the discharging process of the capacitor are continuously alternated, and the voltage of the capacitor presents sawtooth waves. As long as the discharging time of the capacitor is shorter than the access time of the discharging loop, the voltage of the capacitor can be ensured to be reduced to zero. As long as the connection duration of the discharge loop is short enough to be much shorter than the switching period, the falling time of the sawtooth wave can be considered to be approximately zero. The time when the discharging loop is connected into the capacitor is controlled, so that the frequency and the phase of the generated triangular wave can be controlled.
The working process of the phase-shifting sawtooth wave generating circuit is as follows: v of inputrefAfter the pulse passes through the voltage follower, the input pulse is changed into v in figure 8 through high-pass filteringRCShown waveform when v isRCGreater than vtriWhen the trigger Q3 is turned on, the capacitor C2 discharges through R8 and Q3, as long as R8 is small enough, the charge of the capacitor C2 can be quickly discharged, the voltage of the capacitor is reduced to zero, the waveform of C2 has a falling edge, and the falling time is far shorter than the switching period. When v isRCLess than vtriWhen the voltage rises linearly, the Q3 is turned off, and the capacitor C2 is charged with constant current at the moment. The Q3 is continuously alternated in the long-time turn-off and instantaneous turn-on states, the charge and discharge processes of the capacitor C2 are continuously alternated, and the voltage waveform of the capacitor shows the C in the graph 82The sawtooth wave shown. Reference carrier c in the present invention2And a preset carrier c1Are all equal to the switching period, and the reference carrier c2Is advanced by the predetermined carrier c1Leading phase and reference pulse vrefIs proportional to the pulse width of (c).
(5) A proportional-integral-differential pulse combination link; after the proportional pulse and the integral differential pulse are generated, the proportional pulse and the integral differential pulse are synthesized through a certain logic relation to obtain the PID pulse, because the circuit has two carriers c1And c2The pulse generator is used for generating a proportional pulse and an integral differential pulse respectively, so that the proportional pulse and the integral differential pulse have a certain time sequence relation, and the duty ratio can be directly superposed through a logic gate. According to the time sequence relation, the positive error pulse falling edge and the integral differential pulse rising edge of the proportional error pulse are at the same time, and the negative error pulse rising edge and the integral differential error rising edge of the proportional error pulse are at the same time.
Because the positive error pulse and the negative error pulse can not be generated at the same time, when the positive error pulse is at a high level, the negative error pulse is at a low level, and no matter the integral differential pulse is at the high level or the low level, the PID pulse outputs the high level; when the positive error pulse is at a low level and the negative error pulse is at a high level, the PID pulse outputs a low level no matter the integral differential pulse is at the high level or the low level; when the positive error pulse and the negative error pulse are both at low level, the PID pulse is in the same state as the integral differential pulse, and the logic expression is:
Figure BDA0002225337080000121
wherein the integral differential pulse vIDThe pulse width of (c) satisfies:
Figure BDA0002225337080000122
in the formula, wID(k) For integrating the differential pulse vIDPulse width of kth switching period, K1Is the integral coefficient, K2Is a differential coefficient, wp1(k) For the pulse width, w, corresponding to the k-th switching period P1p2(k) The pulse width corresponding to the k-th switching period P2.
The pid pulse superimposing circuit is shown in fig. 9, and the circuit is composed of a not gate, an and gate and an or gate. The proportional pulse and integral differential pulse superposition module circuit is provided with three input signals which are respectively a positive proportional pulse, a negative proportional pulse and an integral differential pulse, the output quantity is a PID pulse, after the negative proportional pulse is inverted, the negative proportional pulse is subjected to phase comparison with the integral differential pulse, and the obtained signal and the positive proportional pulse are subjected to OR operation to obtain an output PID pulse. In practical Buck circuit application, because the ground potential of a switch is different from the ground potential of a control board, the output of a control circuit can drive a switch tube to work only through an isolation link, and under the condition that some switch tubes have higher driving requirements, a driving module circuit is also needed, and the driving circuit generally has an existing circuit module which can be directly used, which is not described in the invention.
It should be noted that this application scenario is only an application result under one parameter, and similar results can be obtained by changing the carrier frequency, i.e. changing the switching frequency, or changing the input/output power of the power circuit within a certain range.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A PID control circuit for a DC-DC switching power supply, comprising: a time delay link, an error pulse generation link, an integral differential pulse generation link, a phase shift carrier generation link and a proportional integral differential pulse combination link;
output voltage U of internal power circuit of DC-DC converteroOutputting the output voltage U of the previous switching period through the time delay linkodWith the output voltage U of the first two switching cyclesodd；
The output voltage U of the power circuitoOutput voltage U of the previous switching cycleodOutput voltage U of the first two switching cyclesoddReference voltage UrefAnd a preset carrier c1The output of the error pulse generating link comprises an error pulse signal P1 at the current moment, an error pulse signal P2 in the previous switching period, an error pulse signal P3 in the previous two switching periods and a reference pulse vref；
Said reference pulse vrefThrough the phase-shift carrier generation link, a reference carrier c is generated2；
An error pulse signal P1 at the current moment, an error pulse signal P2 in the previous switching period, an error pulse signal P3 in the previous two switching periods and a reference carrier c2The integral differential pulse generation unit and the integral differential pulse generation unit are used as the input of the integral differential pulse generation unit together, and the output of the integral differential pulse generation unit is an integral differential pulse vID；
Said integral differential pulse vIDThe error pulse signal P1 at the current moment is used as the input of the PID combination link, and the output of the PID combination link is the PID regulation pulse signal v for controlling the on-off of the DC-DC converter switch tubePIDTo regulate the output voltage of the DC-DC converter.
2. The PID control circuit of claim 1, wherein the error pulse generating element comprises a plurality of error pulse sub-units; each error pulse subunit respectively generates an error pulse signal P1 at the current moment, an error pulse signal P2 in the previous switching period and an error pulse signal P3 in the previous two switching periods; each error pulse signal includes a positive error pulse and a negative error pulse;
the logic expression of the error pulse subunit generating the error pulse signal P1 at the current time is:
Figure FDA0002541733460000021
wherein v iserr+A positive error pulse of the error pulse signal P1 at the current time; v. oferr-Negative error pulse of the error pulse signal P1 at the current time; reference pulse vrefIs a reference voltage UrefAnd a preset carrier c1Comparing to obtain a square wave signal; v. ofoIs the output voltage U of the power circuitoAnd a preset carrier c1Comparing to obtain a square wave signal;
the logic expression of the error pulse subunit generating the error pulse signal P2 of the previous switching period is:
Figure FDA0002541733460000022
wherein, v'err+A positive error pulse of the error pulse signal P2 for the previous switching cycle; v'err-Negative error pulse of the error pulse signal P2 for the previous switching cycle; v. ofodFor the output voltage U of the preceding switching cycleodAnd a preset carrier c1Comparing to obtain a square wave signal;
the logic expression of the error pulse subunit generating the error pulse signal P3 of the first two switching cycles is:
Figure FDA0002541733460000023
wherein, v ″)err+A positive error pulse of the error pulse signal P3 for the first two switching cycles; v ″)err-Negative error pulses of the error pulse signal P3 for the first two switching cycles; v. ofoddFor the output voltage U of the first two switching cyclesoddAnd a preset carrier c1And comparing the obtained square wave signals.
3. The PID control circuit of claim 2, wherein the pulse width of the error pulse signal P1 at the current time is equal to the reference voltage UrefAnd the output voltage U of the power circuitoProportional to the difference of (a); the pulse width of the error pulse signal P2 of the previous switching period and the reference voltage UrefAnd the output voltage U of the previous switching cycleodProportional to the difference of (a); the pulse width of the error pulse signal P3 of the first two switching periods and the reference voltage UrefAnd the output voltage U of the first two switching cyclesoddIs proportional to the difference in (c).
4. A PID control circuit for a DC-DC switching power supply according to any of claims 1-3, characterized in that the reference carrier c2And a preset carrier c1Are all equal to the switching period, and the reference carrier c2Is advanced by the predetermined carrier c1Leading phase with said reference pulse vrefProportional to the pulse width of; the preset carrier c1Is a sawtooth wave.
5. The PID control circuit of claim 4, wherein the phase-shifted carrier generation unit comprises a triode common collector circuit module, a high-pass filter module, a constant current source module and a capacitor discharge module.
6. The PID control circuit of claim 1, wherein the PID generation element comprises a constant current charging and discharging circuit with multiple capacitors.
7. The PID control circuit of the DC-DC switching power supply according to claim 2, wherein the logic expression of the PID combining element is:
Figure FDA0002541733460000031
8. the PID control circuit of claim 1, wherein the delay element is an LRC delay circuit.
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