JP3223293B2 - DC / DC converter - Google Patents

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 a direct current into a direct current having a different voltage.
You.

[0002]

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

[0003] 4 insulating transformer AC voltage V ₁ of the inverter 3 is applied to the primary winding, 5 converts the alternating voltage V ₂ from the secondary winding of the isolation transformer 4 to a DC voltage V ₃ Rectifier, bridge-connected diodes D ₁ to
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, which constitute the smoothing circuit. Reference numeral 8 denotes a load R connected in parallel with the smoothing capacitor 7.

Reference numeral 9 denotes a current sensor for detecting a current flowing through the smoothing reactor 6 (or the output current of the rectifier 5), reference numeral 10 denotes an output voltage reference V _d ^* generator, and reference numeral 11 denotes a voltage of the smoothing capacitor 7, that is, an output voltage V _d. first subtractor, a first voltage controller 12 for amplifying the output signal from the subtractor 11, 13 output V _C and the current sensor 9 of the voltage controller 12 for calculating a deviation between the output voltage reference V _d ^* Is a second subtractor for calculating a deviation from the detected value of the second subtractor 1.
A current controller for amplifying the output signal from 3; 15 a triangular wave carrier signal generating circuit; 16 a current controller 14 for comparing the output from the carrier signal generating circuit 15 to output a "1" or "0" level signal A comparator 17 generates a pulse of each phase of U, X, V, and Y from an output from the comparator 16, and a gate amplifier circuit 18 amplifies the pulse output from the pulse distribution circuit 17.

Next, the operation will be described. The 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 including a ripple 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 a DC with little ripple, and supplied to the load 8. The output voltage _Vd is equal to the IG of the inverter 3.
It is controlled by changing the BT flow rate α.

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

The current controller 14 outputs a current command I
^* And amplifies the deviation between the feedback current I from the current sensor 9, compares the output V _I and the output CAR of the carrier signal generating circuit 15 (carrier signal) by the comparator 16, the inverter by the pulse distributing circuit 17 It generates an AC voltages V ₁ by generating phase pulses. This is referred to as 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 put out a voltage of one cycle T and T _1, the output voltage V _d is controlled by changing the flowing ratio alpha = T ₁ / T.

The output voltage control circuit includes the voltage controller 12 and the current controller 14 as described above. When viewed as a whole voltage control loop, the output voltage control circuit includes a smoothing reactor 6 (inductance value L) and a smoothing capacitor on the output side. Assuming that an 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 can increase the response speed of the voltage controller 12. Therefore, the current controller 14 is provided for speeding 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. FIG.
(1 / SL) · (1 / (1 + SC ₂ R)) where S = jω = d / dt R... A secondary transfer function of load resistance Remain, and since there is a resonance point, the response of the current controller 14 tends to be unstable when the response is made high-speed.

[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.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to eliminate a resonance point in a control loop, speed up control response, and eliminate control instability.

[0012]

(1) D according to the present invention
The C / DC converter includes a main circuit and a control circuit. The main circuit converts a DC voltage into an AC voltage using an inverter, converts the AC voltage into a DC voltage using a rectifier, and generates an output DC voltage via a smoothing circuit. And supply it to the load,
The control circuit includes a voltage controller that outputs an output current reference according to a deviation between the output voltage reference and the output DC voltage.
And the deviation between the output current reference and the output current of the rectifier
Is the positive side deviation, the control output corresponding to the deviation
And a current controller for generating the current.
Controlling the output of the inverter to increase
In the DC / DC converter, the back electromotive force compensation is added to the control circuit.
Compensation circuit and correction means, and the back electromotive force compensation circuit
According to the deviation between the output voltage reference and the output DC voltage
A second voltage controller that outputs a first correction value;
1 which is a feedback of the correction value of 1 and the output DC voltage.
Combining means for outputting a combined value with the correction value of 2 as a correction value
A back electromotive force compensating circuit having
Add the above correction value to the control output of the current controller and
A correction means for correcting the control output is provided.
Control to increase the output of the inverter according to the power.
And the occurrence of resonance is suppressed by the first correction value.
The second correction value makes the smoothing capacitor lighter or lighter.
The peak charge at the time of loading is suppressed .

(2) It is composed of a main circuit and a control circuit. The main circuit converts a DC voltage into an AC voltage with an inverter, converts the AC voltage into a DC voltage with a rectifier, and outputs an output DC voltage through a smoothing circuit. And supplies the load current to a load, and the control circuit outputs a voltage controller that outputs an output current reference according to a deviation between the output voltage reference and the output DC voltage; and a voltage controller that outputs the output current reference and the output current of the rectifier. as the deviation is a positive deviation, and a current controller for generating a control output corresponding to the deviation, in the DC / DC converter to control so as to increase the output of the inverter in response to the control output, the Operator in control circuit
Steps and correction means are provided.
Read the input DC voltage and the output current of the rectifier.
When the output current of the rectifier becomes equal to or less than a predetermined current value, the conduction ratio (α) of the inverter is calculated by the following equation.
The calculation result is calculated as a correction value, and α = ((2 · L · Vd ^* · I0) / (E · (E−Vd
^* ). T)) ^1/2, where α: conduction ratio L: inductance of smoothing reactor Vd ^* : command value of output voltage I0: smoothing reactor current (output current of rectifier) E: DC input voltage T: switching cycle The correction means outputs the control output of the current controller to the
A correction means for correcting the control output by adding the calculated correction value.
And the inverter according to the corrected control output.
The output is controlled so as to increase.

(3) Further, it is composed of a main circuit and a control circuit.
The main circuit converts DC voltage to AC
The AC voltage is converted to DC by a rectifier,
Output DC voltage via the
The control circuit includes an output voltage reference and the output DC voltage.
Voltage control that outputs the output current reference according to the deviation from
Between the output current reference and the output current of the rectifier.
The more positive the deviation is, the more the control output according to the deviation
A current controller for generating a force;
Control to increase the output of the inverter according to
In a DC / DC converter, a memory device is stored in the control circuit.
A step and a correction means, and the storage means is provided with the rectifier in advance.
When the output current of the rectifier is equal to or less than a predetermined current value,
Current ratio corresponding to output current and inverter input voltage
(Α) is calculated by the following equation and stored, and α = ((2 · L · Vd ^* · I0) / (E · (E−Vd)
^* ). T)) ^1/2, where α: conduction ratio L: inductance of smoothing reactor Vd ^* : command value of output voltage I0: smoothing reactor current (output current of rectifier) E: DC input voltage T: switching cycle The actual output current of the rectifier is less than the specified current value
The actual output power of the rectifier
Current and the inverter input voltage that is actually applied.
A storage means for extracting a flow ratio and setting it as a correction value;
Is the control output of the current controller
Correction means for correcting the control output by adding a value,
Increase the output of the inverter according to the corrected control output
This is so controlled as to be performed.

[0015]

[Action] (1) DC / DC converter of the present invention, reverse
The second voltage controller of the electromotive force compensating circuit has an output voltage
Outputs the first correction value according to the deviation between the reference and the output DC voltage.
The combining means calculates the first correction value and the output DC voltage.
The composite value of the fed back second correction value and the correction value
The correction means outputs the control output of the current controller.
The control output is corrected by adding the correction value to the force, and the correction
Control to increase the output of the inverter according to the control output
And the occurrence of resonance is suppressed by the first correction value.
And the second correction value makes the smoothing capacitor lighter.
Suppresses peak charging under load.

(2) Further , the calculating means inputs the input to the inverter.
Read the input DC voltage and the output current of the rectifier,
When the output current of the rectifier falls below a predetermined current value,
The flow ratio (α) of the inverter is calculated by the following formula, and the calculation result is obtained.
補正 = ((2 · L · Vd ^* · I0) / (E · (E−Vd ^*)
) · T)) ^1/2 where α: conduction ratio L: inductance of smoothing reactor Vd ^* : command value of output voltage I0: smoothing reactor current (output current of rectifier) E: DC input voltage T: switching cycle correction Means calculated above to the control output of the current controller
The control output is corrected by adding a correction value, and the corrected control
Control to increase the output of the inverter according to the output
I will.

(3) Further , the storage means is provided in advance of the rectifier.
If the output current is less than the specified current value,
The current ratio (α) corresponding to the current and the input voltage of the inverter is
Is calculated by the following equation and stored. Α = ((2 · L · Vd ^* · I0) / (E · (E−Vd
^* ) · T)) ^1/2 where α: conduction ratio L: inductance of smoothing reactor Vd ^* : command value of output voltage I0: smoothing reactor current (output current of rectifier) E: DC input voltage T: switching cycle The actual output current of the rectifier is less than the specified current value
The actual output power of the rectifier
Current and the inverter input voltage that is actually applied.
The flow ratio is extracted and used as a correction value.
The above correction value is added to the control output of the
The output is corrected, and the input is adjusted according to the corrected control output.
Control to increase the output of the barter.

[0018]

[Embodiment 1] FIG. 1 is a circuit diagram of a DC / DC converter according to a first embodiment of the present invention. The same or corresponding parts as those in the related art are denoted by the same reference numerals and description thereof is omitted. The difference from the prior art is that a back electromotive force compensating circuit 20 is provided in order to eliminate the resonance point of the control loop.

The configuration of the back electromotive force compensating circuit 20 includes a third subtractor 21 for calculating a deviation between the output voltage reference V _d ^* and the output voltage feedback V _d , and a circuit for preventing peak charging at light load. A second voltage controller 22;
It is constructed output of the voltage controller 22 and the output voltage feedback V _d from the adder 23 for adding.

Next, the operation will be described. The overall operation is the same as that of the conventional one, but the operation of the back electromotive force compensating circuit 20 will be mainly described from the difference in the control loop configuration described above. FIG. 2 shows a block diagram of a transfer function of the current control loop, which will be described together with FIG.

Compared with the conventional circuit, the back electromotive force compensating circuit 2 having the output voltage feedback _Vd as an input
The point that 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 section is normally K = 1 when the current is continuous. In this case, the back electromotive force compensating circuit is selected so that G (S) = 1, Adder 1 is added to the output of controller 14 in advance.
By previously adding the output voltage feedback V _d at 9, the current control loop, the effect of V _d is offset by +/- theoretically by disappears, R / ((1+
SC ₂ R)) is deleted. As a result, the only term remaining on the current control loop is 1 / SL, and a stable control system having no resonance point can be provided.

Further, when the load 8 is a very light load, the current becomes less than the intermittent limit I _0TH , and as is well known, the residual charge of the smoothing capacitor 7 causes the smoothing capacitor 7 to be peak-charged. in order to control the V _d should refine the characteristic curve shown in FIG 3 the Tsuryuhi alpha. The curve of FIG. 3 is obtained when the current is interrupted (I ₀ <I
_0TH ) is expressed and plotted by equation (1). α = ((2 · L · V _d ^* · I 0) / (E · (E−V _d ^* ) · T)) ^1/2 (1) where L is the inductance of the smoothing reactor 6, V _d ^*
Is a command value of an output voltage, I ₀ is a smoothing reactor current, E is an input voltage, and T is a switching cycle. Therefore, when I ₀ ≒ 0 at no load, it is necessary to narrow down to α ≒ 0. The second voltage controller 2 performs this function.
2.

In the second voltage controller, the frequency response has a resonance angular frequency ω _C = 1 / ((LC ₂ ) ^1/2 )
Slower integral system K _V /
A control system such as S (K _V is a constant) is appropriate. The α at the time of no load is reduced by the second voltage controller 22,
G (S) = 1 can be apparently set as the gain of the back electromotive force compensation circuit.

As described above, the second voltage controller 2
2 together, the current intermittent mode (I ₀ <I
For _0th), be a on G (S) = 1 apparent gain of the counter electromotive force compensation circuit 20, it is possible to ignore the influence of the output voltage V _d. Further, since the back 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. FIG. 4 is a circuit diagram of a DC / DC converter according to Embodiment 2 of the present invention. In this embodiment, a microcomputer is used as a back electromotive force compensation circuit.

In the figure, reference numeral 24 denotes a back electromotive force compensating circuit;
Reference numeral 5 denotes an A / D converter for converting an analog signal to a digital signal, reference numeral 26 denotes a microcomputer, and reference numeral 27 denotes a D / A conversion circuit for converting a digital signal to an analog signal.

In this embodiment, the output level of the back electromotive force compensating circuit 24 when the load current is interrupted is
Reads the current I ₀ flowing through the smoothing reactor 6 and the input voltage E by the A / D converter 25, calculates α by the equation (1) of the first embodiment, and outputs it by using the D / A converter 27.
In this embodiment, higher-speed control can be performed by using a high-speed microcomputer to perform calculations.

Embodiment 3 FIG. FIG. 5 is a circuit diagram of a DC / DC converter according to Embodiment 3 of the present invention. In this embodiment, a read-only memory (hereinafter referred to as a ROM) is used as a back electromotive force compensation circuit.

In the figure, 28 is a back electromotive force compensating circuit, 2
Reference numeral 9 denotes an A / D converter for converting an analog signal to a digital signal, reference numeral 30 denotes a ROM, and reference numeral 31 denotes a D / A conversion circuit for converting a digital signal to an analog signal.

In this embodiment, the output level of the back 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 saved result is stored in ROM3
The value of α corresponding to the values of I ₀ and E is read from the ROM 30 and output through the D / A converter 31. In the present embodiment, the control can be performed at a higher speed than in the first embodiment, and the configuration can be simplified as compared with the second embodiment.

In this embodiment, the calculation results are stored and used in the ROM. However, the calculation results are stored in a storage device such as an FD (floppy disk), HD (hard disk), or magnetic tape in addition to the ROM. RAM at startup
May be read and executed.

Embodiment 4 FIG. In the above embodiment, the switching element of the inverter 3 has I
Although a GBT (insulated gate transistor) is used, a bipolar transistor, a MOSFET, a thyristor, or the like may be used.

Embodiment 5 FIG. The back 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.

[0035]

As described above, according to the present invention, since the resonance point in the current control system is eliminated by providing the back electromotive force compensating circuit, it is possible to greatly increase the response of the control operation. There is an effect that both high-speed response and stability can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a DC / DC converter according to Embodiment 1 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 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 Embodiment 2 of the present invention.

FIG. 5 is a circuit diagram of a DC / DC converter according to Embodiment 3 of the present invention.

FIG. 6 is a circuit diagram of a DC / DC converter according to Embodiment 5 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]

Reference Signs List 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 first Subtracter, 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 (3)

(57) [Claims] 1. A main circuit and a control circuit, wherein the main circuit converts a DC voltage into an AC voltage by an inverter,
The AC voltage into DC by the rectifier, exits via the smoothing circuit
A voltage controller that generates a DC voltage and supplies the DC voltage to a load, and the control circuit outputs an output current reference according to a deviation between the output voltage reference and the output DC voltage.
And the deviation between the output current reference and the output current of the rectifier is positive.
The more the deviation is on the side, the more control output is generated according to the deviation
And a current controller that performs the control according to the control output.
DC / D for controlling to increase the output of the inverter
In C converter, it provided a counter electromotive force compensation circuit and the correction means to the control circuit, the counter electromotive force compensation circuit, the output voltage reference and the output
A second output of a first correction value according to a deviation from a DC voltage
Voltage controller, the first correction value and the output DC voltage.
Corrects the composite value with the second correction value that feedbacks the pressure
Back electromotive force compensating circuit having combination means for outputting as a value
And then, the above-mentioned correction means above the control output of the current controller
Correction means for correcting the control output by adding a correction value, and outputting the output of the inverter according to the corrected control output;
Control to increase, and by the first correction value,
The occurrence of resonance is suppressed, and the smoothing is performed by the second correction value.
Suppress the peak charge of the capacitor at light load.
A DC / DC converter characterized in that: 2. A main circuit and a control circuit, wherein the main circuit converts a DC voltage into an AC voltage by an inverter,
The AC voltage is converted to DC by a rectifier, an output DC voltage is generated via a smoothing circuit and supplied to a load, and the control circuit outputs an output current reference in accordance with a deviation between the output voltage reference and the output DC voltage. And a current controller that generates a control output corresponding to the deviation as the deviation between the output current reference and the output current of the rectifier is a deviation on the positive side, according to the control output. DC / D for controlling to increase the output of the inverter
In the C converter, the control circuit is provided with a calculating means and a correcting means, and the calculating means is configured to control the DC voltage input to the inverter.
And reading the output current of the rectifier, the output current of the rectifier is below the predetermined current value, calculated flows ratio inverters (alpha) by the following equation, a correction value of the operation result
And calculation means for, α = ((2 · L · Vd * · I0) / (E · (E-Vd
^* ). T)) ^1/2, where α: conduction ratio L: inductance of smoothing reactor Vd ^* : command value of output voltage I0: smoothing reactor current (output current of rectifier) E: DC input voltage T: switching cycle The correction means outputs the control output of the current controller to the
A correction means for correcting the control output by adding the calculated correction value.
And the output of the inverter according to the corrected control output.
DC / DC converter characterized by controlling to increase
Barta. And a main circuit and a control circuit.
The main circuit converts DC voltage to AC voltage with an inverter,
This AC voltage is converted to DC by a rectifier and output through a smoothing circuit.
The control circuit generates an output DC voltage and supplies the load to the load .
Voltage controller that outputs the output current reference according to the deviation
And the deviation between the output current reference and the output current of the rectifier is positive.
The more the deviation is on the side, the more control output is generated according to the deviation
And a current controller that performs the control according to the control output.
DC / D for controlling to increase the output of the inverter
In the C converter, the control circuit is provided with a storage means and a correction means, and the storage means stores a predetermined output current of the rectifier in advance.
Value, the output current of the rectifier and the inverter
Calculate and write the conduction ratio (α) corresponding to the input voltage using the following formula.
Remember, α = ((2 · L · Vd ^* · I0) / (E · (E−Vd
^* ). T)) ^1/2, where α: conduction ratio L: inductance of smoothing reactor Vd ^* : command value of output voltage I0: smoothing reactor current (output current of rectifier) E: DC input voltage T: switching cycle The actual output current of the rectifier is less than the specified current value
The actual output power of the rectifier
Current and the inverter input voltage that is actually applied.
Storage means for extracting the flow ratio and setting it as a correction value, wherein the correction means stores the control output of the current controller
A correction means for correcting the control output by adding the extracted correction value.
And the output of the inverter according to the corrected control output.
DC / DC converter characterized by controlling to increase
Barta.