JPH0260459A - Method of controlling dc/dc converter - Google Patents

Abstract

PURPOSE:To reduce the variation of an output voltage by adding a feedforward voltage control system composed of a divider for dividing the set voltage of said output voltage by the input supply voltage of a converter to a feedback voltage control system. CONSTITUTION:The voltage controlling circuit of a DC/DC converter is composed of a voltage setter 1, a soft start circuit 2, an oscillator 3, a voltage regulator(AVR) 4, a phase shifter 5, a pulse distributor 6, etc. In this case, a divider 7 using the input voltage Vc of the DC/DC converter and the set voltage Vs of the output voltage V0 of said converter as input to operate Vs/Vc is provided, and the output of said divider is added to the output of said AVR 4. Thus, feedforward voltage control system by said divider 7 is added to a feedback voltage control system using the AVR as a main element so that the variation of said output voltage V0 for the rapid variation of said input voltage Vc is suppressed suitably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a start-up special voltage control of a DC/DC converter output voltage and a constant voltage control method after the end of start-up.

[Conventional technology]

The conventional method for controlling the output voltage of this type of converter is as follows:
It is known that the main circuit shown in FIG. 2 is controlled by a voltage control circuit shown in FIG. 3.

Figure 2 is an example of the main circuit of a half-bridge inverter type DC/DC converter, where L is the input smoothing handle, 02 is the input smoothing capacitor, GTO, and GTO.
2 is gate turn-off thyristor, T is transformer, D
l and D2 are diodes, L2 is an output smoothing reactor,
c3 is an output smoothing capacitor. Also ■. and V. are the input and output voltages of the converter, respectively.

The GTO and GTO2 mentioned above are the input voltage ■. Using the terminal voltages of capacitors C and C2 that divide the voltage as the power source, conduction and cutoff are repeated alternately, and each time a current in the opposite direction is passed through the primary winding of the transformer T, and the two sets of current The voltage induced on the secondary side of the transformer T is rectified by diodes D and D2, then combined, and smoothed by reactor L2 and capacitor C3 to form a voltage V. is output.

The output voltage V. The magnitude of is controlled by a conductivity instruction signal applied to the gates of GTO and G T Oz from the voltage control circuit shown in FIG.

In FIG. 3, 1 is a voltage setting device, and the output voltage ■
. The steady value V of the set value Vs of . 2 is a soft start circuit which outputs the set value V which changes at a constant time constant with its steady value as VSO, and 3 is an oscillator which performs switching operation between GTO and GTO□. 4 outputs a reference pulse that defines the period, and 4 is the pressure V of both types.
, and■. This is a voltage regulator (AVR) that calculates the deviation Vs - ■o between the two and outputs a control signal that makes the deviation zero. Further, 5 is a phase shifter, 6 is a pulse distributor, and the G T
A required control pulse signal is output to each of the gates 1 to 1 of O+ and GTO2.

FIG. 4 shows the set voltage (3) and its steady-state value (2) in the soft start circuit 2. FIG. 3 is an operation waveform diagram showing a time variation pattern of , and shows the time point at which the activation command is applied as the time origin.

[Problem to be solved by the invention]

In the feed-hack control of the DC/DC converter output voltage by the conventional method as described above, the output voltage of the converter is controlled to be constant regardless of fluctuations in the input voltage.

However, in the above-mentioned feed hack control, in order to obtain accuracy and stability of output voltage control, the voltage regulator (AVR) has proportional-integral (PI) characteristics, and the feedback system for the output voltage is included. The entire closed-circuit voltage control system must be a control system with a time delay, and therefore, transient fluctuations in the output voltage in response to sudden changes in the input voltage are unavoidable.

In view of the above, it is an object of the present invention to provide an output voltage control method in output pressure control of a DC/DC converter, which reduces transient fluctuations in the output voltage when the input voltage of the converter suddenly changes. .

[Means to solve the problem]

In order to achieve the above object, in the method for controlling a DC/IIC converter of the present invention, the conductivity of the main circuit switching element is controlled to perform constant voltage control.
In the voltage control system of the C/DC converter, the switching element is calculated by dividing the output voltage setting value of the converter, which reaches a steady value with a certain time constant by a start signal, by the detected value of the input DC voltage of the converter. a divider having a gain that outputs a conductivity signal for the converter and sets the signal to a value required to make the output voltage equal to the specified voltage in the steady state of the voltage setting value at the rated value of the input DC voltage of the converter. , the switching element is determined by the sum of the output of the voltage regulator and the output of the divider, which calculates the deviation between the set value and the detected value of the converter output voltage and performs control to make the deviation zero. This is a comprehensive conduction heavy signal.

[Effect]

Output voltage of DC/DC converter■. If the input voltage of the converter is α, the conductivity of the VC1 main circuit switching element is α, and the transformer turns ratio is 1, then in a load state where the output smoothing reactor has a continuous current, Equation (1) is obtained.
It becomes as shown in.

V, -αv o---------------
---------- (1) Therefore, the predetermined output voltage V.

On the other hand, the required conductivity α at input voltage VC is uniquely determined as shown in equation (2).

α −■. /vc −'−−−−−−・−−1−−−
〜---・−(2) Also, the output voltage V in the converter.

Since the predetermined value of is specified by its setting value ■, the formula (2
) becomes as shown in equation (3).

α −v s / v c −−−−−−−−−−
-----------(a) In equation (3), the input voltage V
, changes by ΔV from its steady value, the output voltage ■.

The required correction value Δα of the conductivity α required to maintain the set value V, is as follows, assuming that there is no change in the set value V,
Assuming Zunawara △■s-0, the equation (4) is obtained.

Δα−−α・ΔV C/ VC”−”' (4) In the present invention, a divider is provided that performs the operation shown in equation (3), and the output of the divider is set as a feed hack voltage with respect to the output voltage Vo. By adding it to the output of the voltage regulator (AVR) of the control system, a conduction rate designation signal including the conductivity correction value of formula (4) according to formula (3) is directly given to the main circuit switching element, and The above output voltage can be adjusted immediately without being affected by the time delay in feed hack system control
. The voltage regulator (A
For feedback control by VR), the input voltage ■
. This forms an output-type suppression<Mu system that also uses feedforward control to follow the fluctuations in .

Therefore, the input voltage ■. The correction control of the output voltage ■o due to the fluctuation of is preceded by the feedforward control system using the divider, and the voltage regulator (A
The correction signal from VR) is always approximately zero.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a voltage control circuit showing an embodiment of the present invention.

In addition, the main circuit to be controlled and the set voltage of the circuit shown in Figure 1 ■3
The operating waveform diagrams are as shown in FIG. 2 and FIG. 4, respectively, as in the case of the prior art embodiment.

Furthermore, in FIG. 1, the same reference numerals are given to components having the same functions as in the prior art embodiment shown in FIG. 3.

In the circuit diagram shown in Fig. 3, Fig. 1 shows the D shown in Fig. 2.
Input voltage of C/DC converter■. and the output voltage of the converter■. Input the set voltage V, and V3/■o
, and the output of the divider 7 is added to the output of the voltage regulator (AVR) 4. With the above circuit configuration, a feedforward voltage control system using the divider 7 is added to the feedback voltage control system whose main element is the voltage regulator (AVR) 4, so that the input voltage (2) is increased. The output voltage V for rapid fluctuations in . fluctuations will be suppressed immediately.

〔Effect of the invention〕

According to the present invention, a feedforward voltage comprising a divider that divides the set voltage of the output voltage by the input power supply voltage of the converter is provided for a feedback voltage control system that performs constant voltage control of the output voltage of the DC/DC converter. By adding a control system, fluctuations in the output voltage due to sudden changes in the input power supply voltage can be reduced, and furthermore, by controlling the conductivity of the main circuit switching element in response to an increase in the set voltage, the output voltage can be increased. Soft start is possible.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a voltage control circuit showing an embodiment of the present invention, FIG. 3 is a circuit diagram of a voltage control circuit showing an embodiment of the prior art, and FIG. 2 is the circuit shown in FIG. 1 or 3. FIG. 4 is an operating waveform diagram of the output voltage setting value of the converter in FIG. 1 or 3. 1... Voltage setting device, 2... Soft start circuit, 3
...Oscillator, 4...AVR (voltage regulator), 5...
・Phase shifter, 6... Pulse distributor, 7... Divider, C
,-C. ...Smoothing capacitor, D+, Dz...diode,
GTO, GTO2...Gate turn-off thyristor, L+, Lz...Smoothing reactor.

Claims (1)

[Claims] 1) In the voltage control system of a DC/DC converter that performs constant voltage control by controlling the conductivity of the main circuit switching element, the output voltage setting value of the converter that reaches a steady value with a certain time constant by a start signal is set. A conductivity signal for the switching element is output by dividing by the detected value of the input DC voltage of the converter, and the output voltage is set to the steady state of the voltage setting value at the rated value of the input DC voltage of the converter. A voltage regulator is provided with a divider having a gain required to make the specified voltage equal to the specified voltage, calculates the deviation between the set value of the converter output voltage and the detected value, and performs control such that the deviation becomes zero. A method for controlling a DC/DC converter, characterized in that the sum of the output and the output of the divider is used as a total conductivity signal for the switching element.