JPH08214543A - DC / DC converter and control method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] A counter electromotive force compensating circuit is provided so as to eliminate the resonance point in the current control system, and the response of the current controller is greatly improved to obtain high-speed response and stability. [Configuration] Voltage controller 12 and current controller 1
4, the output voltage feedback V _d is added by the adder 19 to the output of the current controller 14 from the counter electromotive force compensating circuit 20, and the effect of V _d on the current control loop is A stable control system with no resonance point is offset by +/-. Further, when the load 8 is a light load and the current is intermittent, the second voltage is controlled so as to narrow down the conduction ratio α according to the current flowing through the smoothing reactor 6 (the output current of the rectifier 5) in order to control the output voltage V _d. By the controller 22, the gain of the counter electromotive force compensation circuit 20 is apparently G (S).
= 1 and the influence of the output voltage V _d is ignored, and a stable control system with no resonance point is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC / DC converter for converting direct current into direct current of different voltage and a control method thereof.

[0002]

2. Description of the Related Art FIG. 7 is a circuit diagram of a conventional DC / DC converter shown in, for example, a 1990 switching power supply system symposium (sponsored by the Japan Management Association) P7-1-3. In the figure, 1 is a DC power supply,
Reference numeral 2 is an input capacitor (capacitance value C ₁ ) connected in parallel with the DC power source 1, and 3 is an inverter for converting the DC voltage E of the DC power source 1 into a high frequency AC voltage V ₁ , which are bridge-connected U, X, It consists of four-phase arms of V and Y,
Each arm is composed of an insulated gate transistor (hereinafter referred to as an IGBT) as a switching element and a diode connected in antiparallel with the IGBT.

Reference numeral 4 denotes an insulation transformer to which the AC voltage V ₁ from the inverter 3 is applied to its primary winding, and reference numeral 5 converts the AC voltage V ₂ from the secondary winding of the insulation transformer 4 into a DC voltage V ₃ . Rectifier, bridge-connected diode D ₁ ~
It is composed of D ₄ . Reference numerals 6 and 7 denote a smoothing reactor (inductance value L) and a smoothing capacitor (capacitance value C ₂ ) respectively constituting a smoothing circuit, and 8 is a load R connected in parallel with the smoothing capacitor 7.

Reference numeral 9 is a current sensor for detecting a current flowing through the smoothing reactor 6 (or output current of the rectifier 5), 10 is an output voltage reference V _d ^* generator, 11 is a voltage of the smoothing capacitor 7, that is, output voltage V _d. Of the output voltage reference V _d ^* and a first subtractor 12 for amplifying the output signal from the subtractor 11, 13 is an output V _C of the voltage controller 12 and the current sensor 9 Second subtractor for calculating a deviation from the detected value of, a current controller for amplifying an output signal from the second subtractor 13, a triangular wave carrier signal generation circuit, and a current controller 1
4 and the output from the carrier signal generation circuit 15 are compared,
Comparator that outputs a level signal of "1" or "0", 1
Reference numeral 7 is a pulse distribution circuit for generating pulses of U, X, V, and Y phases from the output from the comparator 16, and reference numeral 18 is a gate amplifier circuit for amplifying the pulse output from the pulse distribution circuit 17.

Next, the operation will be described. The electric power of the DC power supply 1 is converted into a rectangular wave AC by the input capacitor 2 and the inverter 3, and is converted into a DC voltage containing ripples through the insulating transformer 4 and the rectifier 5. The generated ripple is smoothed by the smoothing reactor 6 and the smoothing capacitor 7, converted into direct current with less ripple, and supplied to the load 8. The output voltage V _d is the IG of the inverter 3.
Control is performed by changing the flow rate α of BT.

The method of controlling the flow rate will be described below. The difference between the output voltage reference V _d ^* and the fed back output voltage V _d is calculated by the subtracter 11 and further amplified by the voltage controller 12. If there is a deviation between the output voltage reference V _d ^* and the output voltage feedback V _d ,
The output I ^* of the voltage controller 12 is given to the current controller 14 in the next stage as a current command, and acts to control the output voltage V _d by increasing or decreasing the output current I ₀ .

Further, the current controller 14 uses the current command I
The deviation between ^* and the feedback current I from the current sensor 9 is amplified, the output V _I and the output CAR (carrier signal) of the carrier signal generation circuit 15 are compared by the comparator 16, and the pulse distribution circuit 17 compares each of the inverters. The alternating voltage V ₁ is generated by generating the phase pulse. This is DC /
It is shown in the waveform diagram of the control circuit of the DC converter. When the period during which the inverter 3 is outputting the voltage within one cycle T is T ₁ , the output voltage V _d is controlled by changing the conduction ratio α = T ₁ / T.

The output voltage control circuit has the voltage controller 12 and the current controller 14 as described above. When viewed as the entire voltage control loop, the smoothing reactor 6 (inductance value L) and the smoothing capacitor are provided on the output side. Assuming that the angular frequency composed of 7 (capacitance value C ₂ ) is ω _C , it has a resonance circuit having a sharp peak at ω _C = 1 / (LC ₂ ) ^1/2 , and the response speed of the voltage controller 12 can be increased. Therefore, the current controller 14 is provided to speed up the response characteristics.

FIG. 9 is a block diagram showing an open loop transfer function of a current control system including the current controller 14. Figure 9
(1 / SL) · (1 / (1 + SC ₂ R)) in the loop even in the current control system, as shown in S = jω = d / dt R ... Load transfer resistance quadratic transfer function Remains, and there is a resonance point, so that instability tends to occur when the response of the current controller 14 is increased.

[0010]

Since the circuit of the conventional DC / DC converter is configured as described above, since the resonance point exists in the control loop, it becomes unstable when the control response is speeded up. There was a problem.

The present invention has been made to solve the above problems, and an object of the present invention is to eliminate the resonance point in the control loop, speed up the control response, and eliminate the control instability.

[0012]

[Means for Solving the Problems]

(1) A DC / DC converter according to the present invention is composed of a main circuit and a control circuit, and the main circuit converts a DC voltage into an AC voltage by an inverter, converts the AC voltage into a DC by a rectifier, and a smoothing circuit Supply to the load via
The control circuit is a voltage controller that controls the output voltage according to the deviation between the output voltage reference and the output DC voltage, and a current controller that controls the current according to the deviation between the output of the voltage controller and the output current of the rectifier. In the DC / DC converter configured to perform the current control by the output of the current controller, the control circuit is provided with a counter electromotive force compensating circuit, and the counter electromotive force compensating circuit includes the output voltage reference and the output DC A second voltage controller that controls the output voltage according to the deviation from the voltage is provided, and the output of the current controller is corrected by the combined value of the output of the second voltage controller and the output DC voltage. The inverter is controlled by.

(2) Further, it is composed of a main circuit and a control circuit, and the main circuit converts a DC voltage into an AC voltage by an inverter, converts this AC voltage into a DC by a rectifier, and supplies it to a load through a smoothing circuit. In addition, the control circuit controls the output voltage according to the deviation between the output voltage reference and the output DC voltage, and controls the current according to the deviation between the output of the voltage controller and the output current of the rectifier. In a DC / DC converter having a current controller and performing current control with the output of this current controller,
An arithmetic means is provided in the control circuit, and the arithmetic means is an arithmetic means for deriving a conduction ratio of the inverter with respect to the load current based on the load current and the inverter input voltage, and the output of the current controller is corrected based on the arithmetic result. Then, the inverter is controlled by this corrected value.

(3) Further, a memory means is provided in place of the arithmetic means of the control circuit, and the memory means is a memory means for storing the current ratio of the inverter to the load current based on the load current and the inverter input voltage. The current ratio is extracted based on the load current and the inverter input voltage, and the output of the current controller is corrected by the extracted current ratio. (4) The calculation of a computation unit or a storage content of the storage means, α = ((2 · L · V d * · I0) / (E · (E-V d *) ·
T)) ^1/2 However, α: conduction ratio L: inductance of smoothing reactor V _d ^* : command value of output voltage I0: smoothing reactor current (output current of rectifier) E: DC input voltage T: switching cycle It is a thing.

(5) A DC / DC converter control method according to the present invention comprises a main circuit and a control circuit, wherein the main circuit converts a DC voltage into an AC voltage by an inverter, and the AC voltage is converted by a rectifier. The DC voltage is supplied to the load through the smoothing circuit, and the control circuit controls the output voltage according to the deviation between the output voltage reference and the output DC voltage. The output of this voltage controller and the output of the rectifier. A DC / DC converter that has a current controller that controls a current according to a deviation from the current and that is configured to perform the current control by the output of the current controller. The output of the current controller is corrected with this output to control the inverter, and the output voltage reference and output is output when the load current is intermittently output. The deviation between the DC voltage through the integral element is obtained by so as to control the inverter with the correction value obtained by correcting the output of the current controller at its output.

[0016]

[Action]

(1) In the DC / DC converter of the present invention, the second voltage controller of the back electromotive force compensating circuit sends out an output according to the deviation between the output voltage reference and the output DC voltage, and the second voltage controller The output of the current controller is corrected by the combined value of the output and the output DC voltage, and the inverter is controlled by this corrected value.

(2) Further, the calculating means derives the current-carrying ratio of the inverter with respect to the load current based on the load current and the inverter input voltage, corrects the output of the current controller based on the calculation result, and corrects the correction. The value controls the inverter.

(3) Further, a memory means is provided in place of the arithmetic means of the control circuit, and the memory means stores the current ratio of the inverter to the load current based on the load current and the input voltage of the inverter. The current ratio is extracted based on the inverter input voltage and the inverter input voltage, and the output of the current controller is corrected by the extracted current ratio. (4) The calculation of a computation unit or a storage content of the storage means, α = ((2 · L · V d * · I0) / (E · (E-V d *) ·
T)) ^1/2 However, α: conduction ratio L: inductance of smoothing reactor V _d ^* : command value of output voltage I0: smoothing reactor current (output current of rectifier) E: DC input voltage T: switching cycle .

(5) In the DC / DC converter control method of the present invention, when the load current is continuously output, the output of the current controller is corrected by the output according to the DC output voltage to control the inverter, and the load current intermittent output is provided. Occasionally, the deviation between the output voltage reference and the output DC voltage is passed through an integral element, and the output is used to control the inverter with a correction value obtained by correcting the output of the current controller.

[0020]

【Example】

Example 1. FIG. 1 shows a DC / DC according to a first embodiment of the present invention.
In the circuit diagram of the converter, the same or corresponding parts as those of the conventional one are designated by the same reference numerals, and the description thereof will be omitted. This counter electromotive force compensating circuit is different from the conventional one in that the counter electromotive force compensating circuit 20 is provided in order to eliminate the resonance point of the control loop.

The configuration of the counter electromotive force compensating circuit 20 includes a third subtracter 21 for calculating a deviation between the output voltage reference V _d ^* and the output voltage feedback V _d , and a peak charge for preventing a light load. It comprises a second voltage controller 22 and an adder 23 for adding the output of the second voltage controller 22 and the output voltage feedback V _d .

Next, the operation will be described. Although the overall operation is the same as the conventional one, the operation of the counter electromotive force compensating circuit 20 will be mainly described because of the difference in the control loop configuration described above. FIG. 2 shows a block diagram of the transfer function of the current control loop, which will be described in conjunction with FIG.

Compared with the conventional circuit, the characteristic is that the counter electromotive force compensating circuit 2 receives the output voltage feedback V _d as an input.
The output of 0 is added to the output of the current controller 14 by the adder 19. This is to eliminate the term R / (1 + SC ₂ R) representing the influence of the load 8 and the smoothing / smoothing capacitor 7 in the block diagram of FIG.

That is, in FIG. 2, the gain of the inverter unit is usually K = 1 when the current is continuous, but in this case, the counter electromotive force compensating circuit is selected so that G (S) = 1, and the current The adder 1 is previously added to the output of the controller 14.
By adding the output voltage feedback V _d in 9, the effect of V _d is canceled by +/− on the current control loop and disappears, so theoretically R / ((1+
SC ₂ R)) term is erased. As a result, the only term remaining on the current control loop is 1 / SL, and a stable control system with no resonance point can be obtained.

Further, the load 8 is very light and the current is below the intermittent limit I _{0TH. As} is well known, the smoothing capacitor 7 is peak-charged by the residual charge of the smoothing capacitor 7. In order to control V _d , it is necessary to narrow down the flow ratio α with a characteristic curve as shown in FIG. The curve in FIG. 3 shows that the current is intermittent (I ₀ <
The current ratio α of (I _0TH ) is represented by the equation (1) and plotted. α = ((2 · L · V d * · I0) / (E · (E-V d *) · T)) 1/2 ····· (1) where L is the smoothing reactor 6 inductance, V _d ^* is the command value of the output voltage, I ₀ is the smoothing reactor current, E is the input voltage, and T is the switching cycle. Therefore, when I ₀ ≈0 when there is no load, it is necessary to narrow down to α≈0. The second voltage controller 22 plays this role.
Is.

As the second voltage controller, the frequency response is sufficiently smaller than the resonance angular frequency ω _C = 1 / ((LC ₂ ) ^1/2 ) and the slow integration system K _V / S having a large DC gain is used.
A control system such as (K _V is a constant) is suitable. This second
The voltage controller 22 can reduce α under no load, and apparently the gain of the counter electromotive force compensation circuit can be set to G (S) = 1.

As described above, the second voltage controller 2
2 together, the current intermittent mode (I ₀ <
In the case of I _0TH ), the gain of the counter electromotive force compensating circuit 20 can be apparently set to G (S) = 1, and the influence of the output voltage V _d can be ignored. Further, since the counter electromotive force compensation circuit 20 eliminates the resonance point of the current control system, the response speed of the current controller 14 and the first voltage controller 12 can be increased.

Embodiment 2 FIG. Second Embodiment FIG. 4 is a circuit diagram of a DC / DC converter according to a second embodiment of the present invention. In this embodiment, a microcomputer is used as the counter electromotive force compensation circuit.

In the figure, 24 is a back electromotive force compensating circuit, and 2 is.
Reference numeral 5 is an A / D conversion device for converting an analog signal into a digital signal, 26 is a microcomputer, and 27 is a D / A conversion circuit for converting a digital signal into an analog signal.

In this embodiment, the output level of the counter electromotive force compensating circuit 24 when the load current is intermittent is the microcomputer 26.
Reads the current I ₀ flowing through the smoothing reactor 6 and the input voltage E by the A / D converter 25, calculates α according to the equation (1) of the first embodiment, and outputs it using the D / A converter 27.
In this embodiment, the control can be performed at a higher speed than that in the first embodiment by performing the calculation by the high speed microcomputer.

Example 3. FIG. 5 is a circuit diagram of a DC / DC converter according to a third embodiment of the present invention. In this embodiment, a read-only memory (hereinafter R
OM) is used.

In the figure, 28 is a back electromotive force compensation circuit, 2
Reference numeral 9 is an A / D conversion device for converting an analog signal into a digital signal, 30 is a ROM, and 31 is a D / A conversion circuit for converting a digital signal into an analog signal.

In this embodiment, the output level of the counter electromotive force compensating circuit 28 when the load current is interrupted is calculated from the current I ₀ flowing through the smoothing reactor 6 and the input voltage E in advance using the equation (1) in the first embodiment. The results you have set are stored in ROM3
0 is written in advance, the value of α corresponding to the values of I ₀ and E is read from the ROM 30, and is output through the D / A converter 31. In this embodiment, higher speed control can be performed than in the first embodiment, and the configuration can be simplified as compared with the second embodiment.

In this embodiment, the calculation result is stored in the ROM for use. However, in addition to the ROM, the calculation result is stored in a storage device such as an FD (floppy disk), HD (hard disk), magnetic tape or the like. RAM at startup
It may be read in and executed.

Example 4. In the above embodiment, the inverter 3
IGBT (insulated gate transistor) was used for the switching element of the
You may use T, a thyristor, etc.

Example 5. The counter electromotive force compensation circuit described in the above embodiment may be applied to the chopper type DC / DC converter shown in FIG. That is, as shown in FIG. 6, a switching element that performs a chopper operation as a converter is controlled by the control circuit of the present invention.

[0037]

As described above, according to the present invention, the counter electromotive force compensating circuit is provided so as to eliminate the resonance point in the current control system, so that the response of the control operation can be greatly improved. There is an effect that both fast response and stability can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a DC / DC converter according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a transfer function according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a conduction ratio when a current is interrupted according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram of a DC / DC converter according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a DC / DC converter according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram of a DC / DC converter according to a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram of a conventional DC / DC converter.

FIG. 8 is a waveform diagram of a conventional DC / DC converter circuit.

FIG. 9 is a block diagram showing an open loop transfer function of a current control system.

[Explanation of symbols]

1 DC power supply, 2 input capacitor C ₁ , 3 inverter, 4 insulating transformer, 5 rectifier, 6 smoothing reactor, 7 smoothing capacitor, 8 load R, 9 current sensor, 10 output voltage reference V _d ^* generator, 11 1st Subtractor, 12 First voltage controller, 13 Second subtractor, 14 Current controller, 15 Carrier signal generation circuit, 16 Comparator, 17 Pulse distribution circuit, 18 Gate amplifier circuit, 19 Adder, 20, 24, 28 Back electromotive force compensation circuit, 21 Third subtractor, 22 Second controller, 23 Adder, 25,29 A / D converter, 26 Microcomputer, 27,31 D / A
Conversion circuit, 30 ROM.

Claims (5)

[Claims] 1. A main circuit and a control circuit, wherein the main circuit converts a DC voltage into an AC voltage by an inverter,
This AC voltage is converted to DC by a rectifier and supplied to a load through a smoothing circuit, and the control circuit controls the output voltage according to the deviation between the output voltage reference and the output DC voltage. In a DC / DC converter having a current controller that controls a current according to a deviation between an output and an output current of the rectifier, and performing current control with the output of the current controller, a counter electromotive force is applied to the control circuit. A compensation circuit is provided, and this counter electromotive force compensation circuit has a second voltage controller that controls the output voltage according to the deviation between the output voltage reference and the output DC voltage. The output of the current controller is corrected with a combined value with the output DC voltage, and the inverter is controlled with this corrected value. / DC converter. 2. A main circuit and a control circuit, wherein the main circuit converts a DC voltage into an AC voltage by an inverter,
This AC voltage is converted to DC by a rectifier and supplied to a load through a smoothing circuit, and the control circuit controls the output voltage according to the deviation between the output voltage reference and the output DC voltage. In a DC / DC converter that has a current controller that controls a current according to the deviation between the output and the output current of the rectifier, and that controls the current with the output of this current controller, the control circuit is provided with an arithmetic means. The calculating means is a calculating means for deriving the current ratio of the inverter to the load current based on the load current and the inverter input voltage. The calculation result corrects the output of the current controller, and the corrected correction value is used to correct the inverter. A DC / DC converter characterized in that it is controlled. 3. The storage device according to claim 2, wherein storage means is provided in place of the calculation means of the control circuit, and the storage means stores a current ratio of the inverter to the load current based on the load current and the inverter input voltage. As a storage means, to extract the conduction ratio based on the load current and the inverter input voltage,
A DC / DC converter characterized in that the output of the current controller is corrected by the extracted conduction ratio. 4. The calculation content of the calculation means according to claim 2 or the storage content of the storage means according to claim 3 is α = ((2 · L · V _d ^* · I0) / (E · (E−V _d ^* )
T)) ^1/2 However, α: conduction ratio L: inductance of smoothing reactor V _d ^* : command value of output voltage I0: smoothing reactor current (output current of rectifier) E: DC input voltage T: switching cycle A DC / DC converter characterized in that 5. A main circuit and a control circuit, wherein the main circuit converts a DC voltage into an AC voltage with an inverter,
This AC voltage is converted to DC by a rectifier and supplied to a load through a smoothing circuit, and the control circuit controls the output voltage according to the deviation between the output voltage reference and the output DC voltage. A DC / DC converter that has a current controller that controls a current according to a deviation between an output and an output current of the rectifier, and that is configured to perform the current control by the output of the current controller. , The output of the current controller is corrected by the output according to the DC output voltage to control the inverter, and at the time of the intermittent output of the load current, the deviation between the output voltage reference and the output DC voltage is passed through an integrating element to output the difference. The DC / DC controller is characterized in that the inverter is controlled by a correction value obtained by correcting the output of the current controller. Method of controlling the converter.