JPH10127046A - Control circuit for step-up converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the excellent rectification by securing the formation of the sine wave of a power supply current without the excessive increase of the output voltage of a step-up converter. SOLUTION: The output of a rectifier circuit is made to form the multiple pulses at step-up choppers (L1 , Q1 and D1 ) and conducted and smoothed with a capacitor C1 . Thus, the formation of the sine wave of the power supply current is secured, and the rectification can be performed. The ON/OFF control of the switching element Q1 is performed at an exclusive IC 41. At this point, a corrected detection voltage Vo*, which is obtained by adding the detected input voltage Vs to the output voltage Vo, is inputted into the exclusive IC 41. Therefore, when the input voltage is small, the output voltage Vo can be made small, and the excessive voltage increase can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for a step-up converter, and more particularly to a control circuit for a power supply current, while ensuring a sinusoidal power supply current.
It is devised so that rectification can be performed without excessively increasing the output voltage, and is suitable for use in an AC / DC conversion circuit (rectifier circuit, converter circuit) of a general-purpose inverter, and the like.

[0002]

2. Description of the Related Art A general-purpose inverter device mainly includes a converter (rectifier circuit), an inverter, and a control circuit. Not limited to the rectifier circuit built in such a general-purpose inverter device, generally, a rectifier circuit 01 of a capacitor input type as shown in FIG. 2 is frequently used as the rectifier circuit.

[0003] The capacitor input type rectifier circuit 01 is
As shown in FIG. 2, the diode bridge rectifier circuit 02
And a rush current prevention circuit 03 and a capacitor 04, which rectify the AC received from the AC power supply (commercial power supply) 05 and output DC. This capacitor input type rectifier circuit 01 has a simple circuit configuration and is inexpensive.
In addition, there is an advantage that control is not required.

However, when the capacitor input type rectifier circuit 01 is used, the current of the AC power supply 05, that is, the input current (current on the rectifier AC side) input from the AC power supply 05 to the rectifier circuit 02 is not a sine wave but a large harmonic. It becomes a current containing components. Harmonic components included in the current on the rectifier AC side increase heat loss or cause a resonance phenomenon with respect to other loads or electric devices connected to the AC power supply 05, and sometimes these devices cause a resonance phenomenon. Adverse effects such as damage (heating, burning). Such harmonic interference has recently become a major problem.

As shown in FIG. 3, the inrush current prevention circuit 03 includes an electromagnetic contactor (or a power relay or the like) MC and a resistor R. This inrush current prevention circuit 03
When the power is turned on, the contact MC-1 of the electromagnetic contactor MC is turned on.
Is OFF (open state), and the charging current to the capacitor 04 flows through the resistor R, so that the inrush current is limited by the resistor R. When the charging of the capacitor 04 is completed, a voltage is applied to the exciting coil MC-2 of the electromagnetic contactor MC to turn on (short-circuit) the contact MC-1. During normal operation, the contact MC-1 is kept in the ON state, so that the current flows through the electromagnetic contactor MC, does not flow to the resistor R, and no loss occurs in the resistor R.

In order to suppress the above-mentioned harmonic current, various circuit systems have been proposed in which the AC current (current on the rectifier AC side) of the AC power supply 05 is converted into a sine wave. As one of the basic methods, there is a step-up type single-phase converter rectifier circuit (step-up single-phase converter) 10 as shown in FIG.

The boost type single-phase converter 10 is composed of a main circuit 20 which operates on the principle of a boost type chopper to flow a current by making it into a multi-pulse like a PWM inverter, and a control circuit 30 for performing switching control. .

[0008] The main circuit 20 includes a diode bridge rectifier circuit 21 includes a reactor L _1, the switching element Q ₁ which is configured by IGBT (insulated gate bipolar transistor), a diode D _1, the capacitor C for smoothing
₁ and resistors R ₁ , R ₂ and R ₃ .

[0009] Among these, the reactor L ₁ and the switching element Q _1, a diode D _1, the step-up chopper is configured. Therefore, the switching element Q ₁ is turned on by the control of the control circuit 30 (details of the control method will be described later).
When you have N (conducting state), the electromagnetic energy is stored in the reactor L _1.

[0010] When the switching element Q ₁ is becomes OFF (cut-off state), the polarity counter electromotive force is generated in the reactor L ₁ is inverted, the energy of the reactor L ₁ is released. That is, the switching element Q ₁ is in the period to OFF, subjected to any voltage out of the voltage and reactor L ₁ of the rectifier circuit 21, a voltage is output through the diode D _1.
Moreover, the switching frequency of the switching elements Q ₁ and 10 kHz, by passing a current in the multi-pulsed in accordance with the input voltage, the current of the rectifier circuit AC side than is sinusoidal. The voltage output from the diode D ₁ is smoothed by the capacitor C ₁ and becomes a DC output voltage Vo.

The control circuit 30 includes a voltage error amplifier A ₁ ,
A multiplier 31, a current error amplifier A _2, the comparator C
P and an oscillator 32 and the like.

Voltage error amplifier A₁Is the output voltage (DC)
V₀Is the resistance R_2,R_ThreeThe detection output voltage divided by
Flow) V₀'And the reference voltage (DC) V_refIs entered, and both
Voltage V ₀', V_refError voltage (DC) V_eTo
Output. The multiplier 31 is rectified by the rectifier circuit 21 and
Detection indicating the value of the input voltage that has a rectified waveform (pulsating flow)
Input voltage V_sAnd the error voltage (DC) V_eIs entered,
Both voltages V_s, V_eAnd the reference current I_refOutput
You. This reference current I_refIs the detected input voltage V_sof
The waveform (pulse flow) corresponds to the waveform (rectified waveform)
You.

The current error amplifier A ₂ detects a value of a current flowing through the main circuit 20 (a current corresponding to an output current of the boost type single-phase converter) by using a resistor R _1.
d and the reference current I _ref are input, and the two currents I _d,, I
_An error current _Ie that is a difference from _ref is output. Oscillator 32
Outputs a sawtooth oscillating current I _h.

The PWM comparator CP outputs the error current I _e
And compared with the oscillating current I _h, when the I _e> I _h and ON the switching element Q _1. At this time, energy is stored in the reactor L _1. When I _e <I _h , the switching element Q ₁ is turned off.
F. At this time, the energy stored in the reactor L ₁ is released.

[0015] Since the frequency of the oscillating current I _h is 10kHz and fast, ON · OFF of the switching element Q ₁ is also carried out at high speed. For this reason, the detection current I _d is
when it becomes larger than _ref, the switching element Q ₁ is becomes large fraction of time the ON in per unit of time, energy is stored in the reactor L _1, approaches the reference current I _ref detected current I _d is reduced. Further, when the detected current I _d becomes smaller than the reference current I _ref, the switching element Q ₁ is becomes large fraction of time becomes OFF in per unit time, is the energy from the reactor L ₁ release, the detection current I _d increases And the reference current I _ref
Approach.

By performing the above control, the detected current
I_dIs the reference input voltage V _dFlows following
(See FIG. 5). Therefore, the power supply current is
It can be transformed.

[0017]

When the circuit configuration as shown in FIG. 4 is realized, as apparent from the comparison with the circuit of FIG.
Electronic components such as operational amplifiers, comparators, and transmitters are required. Therefore, an increase in the number of parts, an increase in cost, and the like become problems.

Further, the principle of operation in the circuit of FIG. 4, the output voltage V _o is higher than the power supply voltage input. Therefore, the output voltage V _o must be controlled to be higher than the maximum value of the power supply voltage fluctuations. In other words, even if the input voltage is actually low, the output voltage is controlled to be higher than necessary. In such a state, the DC voltage (output voltage V
_o )), the stress applied to the main circuit components (converter, smoothing capacitor, inverter) increases, which is not preferable in terms of reliability and life.

An object of the present invention is to provide a boost converter control circuit which has a small number of components and does not require an output voltage to be higher than necessary with respect to an input voltage.

[0020]

According to the present invention, there is provided a rectifying circuit comprising a rectifier circuit, a reactor, a switching element, and a diode.
A control circuit for controlling ON / OFF of the switching element of a boost converter including a boost chopper for boosting a voltage input from the rectifier circuit by an F operation and a capacitor for smoothing an output from the boost chopper. A voltage-dividing resistor for detecting an input voltage input to the boost chopper from the rectifier circuit to obtain a detected input voltage; and an output voltage detecting means for detecting an output voltage output from the capacitor to obtain a detected output voltage Output voltage correcting means for correcting the value of the detected output voltage according to the value of the detected input voltage to obtain a corrected detected output voltage; a detected current having a value corresponding to the output current of the boost converter; When the voltage and the correction detection output voltage are input, the switching element is turned on so that the waveform of the detection current follows the waveform of the detection input voltage. Characterized by being constituted by a dedicated IC for the OFF control.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a main circuit and a control circuit of a boost type single-phase converter according to an embodiment of the present invention. Note that parts performing the same functions as those of the related art are denoted by the same reference numerals, and redundant description will be omitted.

A main circuit 20 of the boost type single-phase converter;
The configuration itself of the AC power supply 05 is the same as the conventional one shown in FIG. In the present embodiment, the control circuit 40 is devised.

The control circuit 40 includes a dedicated IC 41, an output voltage detecting means 42, an output voltage correcting means 43, a voltage dividing resistor r ₁ ,
r ₂ .

The dedicated IC 41 includes an error amplifier for voltage control, an oscillator and a comparator for PWM control, and the like.
In addition to having a control function having the same contents as the control circuit 30 described above, a protection circuit for overvoltage, overcurrent, and the like is built in. Such a dedicated IC 41 is already commercially available at a relatively low cost, and is mainly used for small-capacity applications.

This dedicated IC 41 has a detection input voltage V _s
, The detection current _Id, and the correction detection output voltage V ₀ ^* . The correction detection output voltage V ₀ ^* will be described later. The dedicated IC 41 performs the same control operation as the control circuit 30 of FIG. That is, the dedicated IC obtains a reference current by multiplying the error value between the corrected detection output voltage V ₀ ^* and the built-in reference voltage by the detection input voltage V _s , and calculates the difference between the reference current and the detection current I _d. Find a certain error current. Moreover, the error current and the oscillation current by comparison PWM comparator to ON · OFF control of the switching element Q _1.

The major feature of this embodiment lies in the output voltage detecting means 42 and the output voltage correcting means 43. These configurations and operations will be described below.

The output voltage detecting means 42 is constituted by a fixed resistor r ₃ and the movable resistor r _4, and outputs a corresponding output voltage V ₀ (divided by) the detected output voltage V ₀ '. Instead of moving resistor r _4, it may be used electron trimmer (Digital control potentiometer). In this way, by digitally controlling the tap position of the electronic trimmer according to the detection input voltage Vs, the resistance value (r ₄ ) can be changed to correct the value of the detection output voltage V ₀ ′.

The output voltage correction means 43 detects the detected output voltage V
A value of ₀ ', then corrected according to the value of the detected input voltage V _s,
The correction detection output voltage V ₀ ^* is output. So, for example,
The detection output voltage V ₀ ′ is multiplied by a variable to obtain a corrected detection output voltage V ₀ ^* , and the value of the variable is made to be proportional to the value of the detection input voltage V _s . Therefore, correction detection output voltage V ₀ ^* becomes small when detecting the input voltage V _s is small, the correction detection output voltage V ₀ ^* becomes large when the detection input voltage V _s is greater.

As described above, in the present embodiment, the information on the current output voltage V ₀ (detected output voltage V ₀ ′) obtained by the output voltage detecting means 42 is added to the information on the current input voltage (detected input voltage V _s). ) Is added to obtain the corrected detected output voltage V ₀ ^* . As a result, an output voltage V ₀ corresponding to the input voltage can be obtained, and voltage stress on the main circuit element can be reduced.

That is, in the case of the boost converter, the design of the output voltage V ₀ is set to a high value so that the operation does not become unstable even at the maximum value of the power supply voltage fluctuation.
Therefore, as in the prior art (FIG. 4), when the detected output voltage V ₀ ′ is a constant value due to the resistance voltage division, even when the power supply voltage (input voltage) is low, a high value set based on the maximum value of the power supply voltage fluctuation is used. , The output voltage V ₀ is controlled. However, in the present embodiment, when the input voltage is small, the correction detection output voltage V
_{It is possible} to lower ₀ ^* and, consequently, reduce the value of the output voltage V ₀ .

[0031]

According to the present invention, a commercially available dedicated IC having a built-in control function and protection function is used for a control circuit of a boost converter circuit used for a general-purpose inverter or the like, so that a relatively inexpensive and highly reliable circuit is provided. Power supply high frequency suppression measures can be implemented.

By providing the output voltage correcting means in the preceding stage of the dedicated IC, it is not necessary to unnecessarily increase the output voltage with respect to the input voltage, thereby reducing the voltage stress on the main circuit components, extending the life, and increasing the reliability. Sex can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a capacitor input type rectifier circuit.

FIG. 3 is a circuit diagram showing an inrush current prevention circuit.

FIG. 4 is a circuit diagram showing a conventional boost type single-phase converter.

FIG. 5 is a waveform diagram schematically showing a relationship between a detection input voltage and a detection current.

[Explanation of symbols]

REFERENCE SIGNS LIST 01 Capacitor input type rectifier circuit 02 Diode bridge rectifier circuit 03 Inrush current prevention circuit 04 Capacitor 05 AC power supply 10 Boost single-phase converter 20 Main circuit 21 Diode bridge rectifier circuit 30 Control circuit 31 Multiplier 32 Oscillator 40 Control circuit 41 Dedicated IC 42 output voltage detection means 43 output voltage correcting unit r _1, r ₂ partial pressure resistors A ₁ voltage error amplifier A ₂ current error amplifier CP PWM comparator L ₁ reactor Q ₁ switching element D ₁ diode C ₁ capacitor R _1, R _2, R ₃ resistor V ₀ output voltage V ₀ 'detection output voltage V ₀ ^* correction detection output voltage V _ref reference voltage V _s detection input voltage V _e error voltage I _d detection current I _ref reference current I _e error current I _h oscillation current

Claims (1)

[Claims] 1. A rectifier circuit comprising a reactor, a switching element, and a diode.
A control circuit for controlling ON / OFF of the switching element of a boost converter including a boost chopper for boosting a voltage input from the rectifier circuit by an FF operation and a capacitor for smoothing an output from the boost chopper. A voltage dividing resistor for detecting an input voltage input from the rectifier circuit to the boost chopper to obtain a detected input voltage; and an output voltage detecting means for detecting an output voltage output from the capacitor to obtain a detected output voltage. Output voltage correction means for correcting the value of the detected output voltage according to the value of the detected input voltage to obtain a corrected detected output voltage; a detection current having a value corresponding to the output current of the boost converter; Voltage, the correction detection output voltage is input, the switching element so that the waveform of the detection current follows the waveform of the detection input voltage A step-up converter control circuit comprising a dedicated IC for ON / OFF control.