JP3232995B2 - Switching control method of stabilized power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilizing power supply, such as a switching system or a chopper system, which receives a rectified voltage of an AC power supply voltage as a DC input voltage. It relates to a method for controlling.

[0002]

2. Description of the Related Art A stabilized power supply widely used in various applications is essentially a DC / DC converter. Therefore, when a power supply is a commercial AC power supply, an AC voltage is rectified as an input voltage. Need to receive DC voltage. To rectify the AC power supply voltage to a DC voltage, the AC voltage Va is generally full-wave rectified by a rectifier 11 of a rectifier circuit 10 as shown in FIG. 2 (a), and the pulsating rectified voltage is converted to a reactor 12 and a capacitor.
13, and smoothed and stabilized to obtain a DC input voltage Vi of the stabilized power supply. In order to extract this input voltage Vi in a stabilized waveform without pulsation, it is customary to use a capacitor 13 having a sufficiently large capacitance, usually 100 to 1000 μF.

However, the pulsating rectified voltage generated by the rectifier circuit 11 includes many harmonic components, and the reactance of the capacitor 13 decreases as the frequency increases. Has a sharp peak that is significantly different from the sine waveform of the AC voltage Va, and becomes a deformed waveform containing a large amount of harmonics, especially odd-order harmonics.This tendency becomes more pronounced as the capacitance of the capacitor 13 increases. .

When the current Ia from the AC power supply has a deformed waveform, the power factor of the power from the power supply decreases, adversely affecting the power supply circuit due to harmonics, and increasing the heat generated by the harmonics in the capacitor 13. And the like. Reactor
If a large inductance is used for 12, this problem is slightly alleviated, but it is not only expensive but also the conversion efficiency of AC voltage Va to DC input voltage Vi tends to be reduced.
Therefore, by incorporating a type of converter as shown in FIG.
A conventional technique for making Ia a substantially sinusoidal waveform is known.

The converter 70 shown in FIG. 3 is of a so-called step-up type, which receives a rectified voltage from the rectifier 11 into a reactor 71 and interrupts a current flowing therethrough by a transistor 72 while taking out the voltage on the output side through a diode 73. The voltage is smoothed by a capacitor 13 and then supplied to a stabilized power supply (not shown) as an input voltage Vi. The intermittent period of the current is specified by the period of the harmonic pulse from the oscillator 75 applied to the flip-flop 74 that controls the gate of the transistor 72. A difference amplifier to keep the value of the input voltage Vi constant
A rectifier having substantially the same sine waveform as the AC voltage Va is supplied to the multiplication circuit 77 by a difference signal which is a difference between the reference voltage e and the reference signal e.
The product of each instantaneous value of the full-wave rectified voltage by 11 and this error signal value is calculated and given to the comparator 78 as a control signal,
This control signal value is supplied to the transistor 72 by the current detection resistor 79.
Is compared with the waveform of the detected reference signal.

The flip-flop 74 is set when a pulse is received from the oscillator 75, and the transistor 72 is output by the Q output.
Turn on. Thereafter, the flip-flop 74 is reset by the output of the comparator 78 each time the control signal value of the multiplying circuit 77 cuts off the waveform of the reference signal detected by the current detection resistor 79, and the transistor 72 is turned off. The control signal value by the multiplier 77 is the full-wave rectified waveform by the rectifier 11 and the reference value e of the input voltage Vi.
Therefore, the current flowing through the transistor 72 follows the sine waveform of the full-wave rectified waveform at a very short cycle specified by the oscillation frequency of the oscillator 75, and the input voltage
It is finely controlled so that Vi is always kept at a constant value. In this manner, the input voltage applied to the stabilized power supply while controlling the waveform of the current Ia taken from the AC power supply by the conventional circuit of FIG. 3 to have the same phase as the AC voltage Va and a sine waveform similar to the waveform.
Vi can be kept constant.

[0007]

According to the above-mentioned prior art, the current taken from the AC power supply is accurately controlled to have a sinusoidal waveform similar to the AC voltage, and the power factor of the power taken from the AC power supply is kept almost exactly at 1. Although the harmonic component of the current can be reduced to almost zero, the total cost of the stabilized power supply is considerably high because the converter and the multiplier circuit shown in FIG. 3 are incorporated on the input side, and the input side circuit consumes power. Therefore, there is a problem that the conversion efficiency is reduced accordingly. A particular problem in terms of cost is the multiplication circuit. If the operation accuracy is sufficiently increased, the cost will be extremely high. In addition, if the required accuracy is to be maintained even when the AC voltage varies over a wide range, the operation requires a wide dynamic range. Therefore, a dedicated chip is required to provide a stable power supply, and it cannot be incorporated into the main body of the stabilized power supply or the integrated circuit device for the input-side converter, which further increases the cost.

An object of the present invention is to solve such a problem and improve the power factor by improving the waveform of the current taken from the AC power supply without particularly incorporating a converter or the like at the input side of the stabilized power supply, thereby improving the harmonic component of the current. Is to reduce.

[0009]

SUMMARY OF THE INVENTION According to the present invention, an object of the present invention is to provide an error signal representing a difference between an actual value of an output voltage of a stabilized power supply and a target value, having a substantially sinusoidal waveform in phase with the voltage of an AC power supply. Creates a control signal with a correction signal superimposed, compares the control signal with a reference signal having a pulsating waveform synchronized with the switching cycle of the stabilized power supply, and opens and closes the switching transistor when the control signal value cuts off the reference signal waveform The problem is solved by controlling the state to correct the waveform of the current taken from the AC power supply into a sinusoidal waveform having the same phase as the AC voltage.

According to the present invention having the above-described structure, the waveform of a current taken from an AC power supply without using a converter or a multiplication circuit on the input side is substantially sinusoidal while utilizing a control system for maintaining the output voltage of the stabilized power supply constant. Instead of an error signal that represents the difference between the output voltage and the target value, which is usually used for constant control of the output voltage, a waveform that is substantially the same as the AC voltage obtained from the pulsating rectified voltage is used. A control signal that changes over time according to the AC voltage waveform is created by superimposing the signal, and the instantaneous value opens and closes the switching transistor at the timing when the reference signal of the pulsating waveform synchronized with the switching cycle is opened and closed. Is corrected to a sine wave.

The method of the present invention is particularly suitable when the stabilized power supply is a switching power supply of a current mode operation type.
In this case, it is preferable to use a detection signal of a pulsating current flowing through the switching transistor as the reference signal in the above configuration. The opening / closing control for the switching transistor at the timing when the instantaneous value of the control signal cuts off the waveform of the reference signal may be usually an off operation control.

When implementing the method of the present invention, it is easiest to produce the above-mentioned correction signal in the form of voltage division by a resistive voltage dividing circuit which receives a pulsating voltage obtained by rectifying an AC voltage. In order to generate a control signal by superimposing the correction signal on the error signal, it is preferable to couple the error signal to the correction signal, which is a resistor voltage division, via a resistor. A control gain for constant control of the output voltage can be set.

When the method of the present invention is applied to an application in which the voltage of the AC power supply or the load of the stabilized power supply fluctuates over a wide range, for example, about ± 20% or more, the current waveform tends to deviate from a sine wave. On the other hand, it is desirable to perform waveform shaping so as to dull the waveform near the maximum value or the peak value. For this purpose, it is preferable to connect a waveform shaping circuit in which a zener diode and a resistor are connected in series to the dividing point of the voltage dividing resistor on the power receiving side in parallel with the resistor voltage dividing circuit. It is preferable to connect a plurality of waveform shaping circuits each having a different breakdown voltage in parallel, or to divide the voltage dividing resistor finely and connect the waveform shaping circuits at each division point.

Further, it is desirable to superimpose a negative bias value on the control signal in order to make the current waveform closer to a sine wave as accurately as possible. This negative bias can be created by rectifying the induced voltage of an auxiliary coil provided in a transformer or the like to a polarity opposite to that of the auxiliary power supply voltage in order to create an auxiliary power supply voltage for power supply to the control system of the stabilized power supply. It is convenient to superimpose this on the control signal by combining a negative bias with the correction signal via a resistor and setting the degree to which the bias is effective by the resistance value of the combined resistor.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 2A is a circuit diagram showing a configuration example of a stabilized power supply to which the control method of the present invention is applied, and FIGS. 2B and 2C are circuit diagrams showing a modified example of the waveform shaping circuit. FIG. 3D is a waveform diagram showing an example of the waveform of the control signal, and portions corresponding to those in FIGS. 2 and 3 are denoted by the same reference numerals.

The rectifier circuit 10 at the upper left of FIG.
And a reactor 12 and a capacitor 13.The AC voltage Va of the commercial frequency of the AC power supply is rectified and converted into a DC input voltage Vi applied to a stabilized power supply on the right side thereof. However, even if it is omitted as appropriate, no major trouble occurs, and it is preferable to use a capacitor 13 having a much smaller capacitance than the conventional one, for example, about 1 μF.

The stabilized power supply shown is a switching power supply. As is customary, the transformer 1 receives an input voltage Vi at a primary coil 1a, and a current flowing through the primary coil 1a is interrupted by a switching transistor 2, and In the illustrated embodiment, the current waveform is detected by the current detection resistor 2a and used as a pulsating reference signal Sr. In the example of FIG voltage induced in the secondary coil 1 b of the transformer 1 of the flyback it is rectified by the diode 3, and is taken out as an output voltage Vo of the stabilized power supply on stabilized by the capacitor 4. The transformer 1 includes an auxiliary coil 1c. The induced voltage of the transformer 1 is rectified by the diode 5 and stabilized by the capacitor 6, and then supplied to the control system of the stabilized power supply as the auxiliary power supply voltage Vd. At the time of startup, the auxiliary power supply voltage Vd rises by charging the capacitor 6 via the startup resistor 7 with the input voltage Vi.

A control circuit shown by a dashed line on the left side of the figure.
Reference numeral 20 denotes an opening / closing control of the switching transistor 2, and includes an oscillator 21, a comparator 22, and a flip-flop 23 which operate upon receiving the above-mentioned auxiliary power supply voltage Vd. Oscillator 21 is flip-flop driven by the oscillation pulse.
23, the transistor 2 is turned on by the open / close command Ss which is the Q output, and the comparator 22 resets the flip-flop 23 with the high output to
Off. The switching frequency of the transistor 2 specified by the oscillation frequency of the oscillator 21 is set to several tens to several hundreds kHz, which is about three to four digits higher than the frequency of several tens Hz of the commercial AC voltage Va.

Since the stabilized power supply shown in FIG. 1A is a switching power supply of a current mode operation type, a reference signal having a pulsating waveform to be compared with a control signal Sc described later by the comparator 22 is used.
The detection signal of the current flowing through the transistor 2 by the current detection resistor 2a is used as Sr, and the waveform of the reference signal Sr is changed to the control signal Sc.
The output of the comparator 22 is set high every time the signal value of the signal is cut off, and the transistor 2 is turned off.

In the present invention, the control signal Sc to be supplied to the comparator 22 is converted into an error signal Se representing the difference between the actual value of the output voltage Vo of the stabilized power supply and the target value by using a substantially sinusoidal waveform in phase with the AC power supply voltage Va. It is made by superimposing the correction signal Sa which has. FIG.
In the embodiment of (a), for example, a shunt regulator is provided as a part of the error signal circuit 30 on the secondary side of the transformer 1 as a voltage detector 31 in order to generate the error signal Se, and the target of the actual value of the output voltage Vo is set. Photocoupler 32 with a current proportional to the difference
Of the photodiode 32 shown in the lower left part of FIG. 1A by driving the light emitting portion 32a of FIG.
b. A constant current is supplied from the current source 33 in the control circuit 20 to the light receiving section 32b, and a voltage drop caused by the current is used as an error signal Se. In the illustrated example, a small-capacity capacitor 34 is connected in parallel to the light receiving section 32b in order to remove a pulsating component in the error signal Se. Since the voltage drop of the light receiving section 32b is lower as the light L is stronger, the signal value of the error signal Se is lower as the output voltage Vo is higher in this embodiment.

In order to give the correction signal Sa, which is another component of the control signal Sc, a sinusoidal waveform similar to the AC voltage Va, in this embodiment, a pulsating rectified voltage obtained by rectifying the AC voltage Va. The full-wave rectified voltage is applied to a voltage dividing circuit 40 composed of resistors 41 to 43, and the voltage divided by the resistors 41, 42 and 43 is used as a correction signal Sa. While the above-mentioned error signal Se is a so-called DC component representing the control error of the output voltage Vo in the control signal Sc, the correction signal Sa is an AC component representing the waveform of the AC voltage Va, and therefore its signal value Changes with time according to the instantaneous value of the AC voltage Va. In order to superimpose the two signals Se and Sa, the error signal circuit 30 is connected to a resistor voltage dividing circuit 40 via a resistor 35 in the illustrated example. The content of the error signal Se of the control signal Sc is set by the resistance value of the coupling resistor 35, and accordingly, the control gain for keeping the output voltage Vo of the stabilized power supply constant is set.

In the present invention, the correction signal Sa generated from the waveform of the AC voltage Va is superimposed on the error signal Se relating to the actual value of the output voltage Vo as a control signal Sc.
22 to be compared with the waveform of the pulsating reference signal Sr. Accordingly, the timing of the OFF operation of the switching transistor 2 is adjusted so as to eliminate an error relating to the output voltage Vo, and to adjust the value of the current Ia taken from the AC power supply to the instantaneous value of the sine waveform AC voltage Va at that time. According to the method of the present invention, the current Ia from the AC power supply can be controlled to have a substantially sinusoidal waveform while the output voltage Vo is kept constant.

As a result of implementing the method of the present invention,
If the voltage value of Va is constant within the range of ± 20%, the operation of controlling the current Ia from the AC power supply into a sinusoidal waveform as described above functions without any problem, and the power factor of the power from the AC power supply is substantially reduced. It can be increased to 1 and the harmonic component of the current Ia can be reduced to almost 0. For example, when the AC voltage Va is high and the load on the stabilized power supply is light, the AC voltage
There is a tendency for the waveform to be slightly sharp near the peak value of Va. The waveform shaping circuit 50 is for accurately controlling the current Ia to have a sine waveform even in such a case.

The waveform shaping circuit 50 shown in FIG. 1A is composed of a resistor 51 and a Zener diode 52 connected in series.
40 is connected to receive the potential of the interconnection point between the voltage dividing resistors 41 and 42 on the power receiving side. Thereby, the correction signal Sa
However, the waveform of the control signal Sc is shaped so that the waveform near its maximum value becomes dull. In order to perform this waveform shaping more precisely, as shown in FIG. 1B, a plurality of series circuits of a resistor 51 and a Zener diode 52 having different breakdown voltages are connected in parallel, and in the example of FIG. As shown in FIG. 1 (c), it is preferable to divide the voltage dividing resistor 42 into partial resistors 42a and connect them at each connection point. FIG. 1 (d) shows the waveform of the control signal Sc shaped in this manner. For comparison, the sine waveform of the AC voltage Va is shown by a thin line superimposed on the waveform, and from the figure, the waveform of the control signal Sc is shown. It has been found that the value of has become dull near the peak value of the AC voltage Va.

Although the waveform I can control the current Ia to have a sine waveform even if the AC voltage Va varies over a wide range, the bias circuit 60 shown in FIG. 1 (a) superimposes a negative bias on the control signal Sc. This is to further expand the controllable range of the waveform of the current Ia with respect to the change in the AC voltage Va. As the bias voltage source, it is preferable to use the induced voltage of the auxiliary coil 1c of the transformer 1 for generating the auxiliary power supply voltage Vd for supplying power to the control circuit 20 and the like as shown in FIG. The auxiliary power supply voltage Vd may be rectified to the opposite polarity, and may be smoothed by the capacitor 62 to be a negative bias. This negative bias is superimposed or added to the control signal Sc via the resistor 63 in the illustrated example. Under the same load condition of the stabilized power supply, the bias circuit 60 stabilizes the signal value level of the control signal Sc so that the signal value level does not fluctuate much even if the AC voltage Va changes over a wider range. A stable control action can be performed so as to keep the waveform.

When the above-described waveform shaping circuit 50 and bias circuit 60 are provided, the stabilizing power supply can be shared for the AC voltage Va of 100 V and 200 V, for example. According to the result of applying the method of the present invention to such a stabilized power supply, the AC voltage Va
The current Ia can be controlled to have a substantially sinusoidal waveform even when it changes over a wide range of 60 to 240 V, and the power factor of the power taken from the AC power supply can be guaranteed to be about 97%.

Finally, the reason why the present invention does not need to use the multiplication circuit 77 as in the conventional example of FIG. In the case of the conventional example, as described above, a difference signal representing the difference between the input voltage Vi to be applied to the stabilized power supply and the predetermined reference value e is created by the difference amplifier 76, and the signal value and the waveform of the AC voltage Va are represented. The multiplication circuit 77 calculates the product of the rectified voltage of the rectifier 11 and the instantaneous value, and supplies the result to the comparator 78 as a control signal. Here, the difference signal value to be multiplied needs to include a certain component in addition to the error of the current value of the input voltage Vi. That is, if there is no fixed component, when the error is 0, the multiplication result is also 0, and the control signal does not reflect the waveform of the AC voltage Va.

On the other hand, in the present invention, the control signal Sc is formed by superimposing the correction signal Sa reflecting the waveform of the AC voltage Va on the error signal Se. When this is compared with the conventional example, the error signal Se corresponds to the error component of the difference signal value before multiplication, and the correction signal Sa corresponds to the constant component of the difference signal value. That is, in the method of the present invention, the correction signal Sa plays the same role as the constant component of the difference signal value after the conventional multiplication, and the error signal Se plays the same role as the error component of the difference signal value after the conventional multiplication. The difference is that the waveform of the voltage Va is not reflected. From a control point of view, it is not necessary to reflect the waveform of the AC voltage Va in any of its components like the difference signal value after multiplication. It is desirable that the signal be composed of a component and a waveform reflection component.

However, the conventional example of FIG. 3 is a converter on the input side of a stabilized power supply, so that it is sufficient to output an input voltage Vi proportional to the AC voltage Va. In the present invention, however, the output voltage Vo of the stabilized power supply is required. Current Ia taken from the AC power supply to the voltage control system
Is built in, the current waveform control function is easily affected by adverse effects when the voltage value of the AC voltage Va and the load of the stabilized power supply vary over a wide range. To solve this problem, the aforementioned waveform shaping circuit 50 and bias circuit 60
It is very effective to appropriately adopt the above as needed or as needed.

[0030]

As described above, in the switching control method according to the present invention, the error representing the difference between the actual value of the output voltage of the stabilized power supply receiving the rectified voltage of the AC power supply voltage as the DC input voltage and the target value. A reference signal having a pulsating waveform synchronized with the switching cycle of the stabilized power supply by superimposing a correction signal having a sine waveform in phase with the AC voltage of the power supply on the signal as a control signal for the switching operation of the stabilized power supply. By controlling the opening / closing operation of the switching transistor at the timing when the instantaneous value of the control signal cuts the pulsating waveform of the reference signal, the following effects can be obtained.

(A) Utilizing a voltage control function provided in the stabilized power supply to keep its output voltage at a constant value, the current waveform obtained from the AC power supply without using a converter on the input side as in the related art is converted to an alternating current. By controlling the voltage in the form of a sine wave having the same phase as the voltage, the power factor of the power taken from the power supply can be increased to near 1, and the harmonic component of the current can be reduced to almost 0, thereby eliminating the possibility of adversely affecting the power supply circuit.

(B) A control signal for switching operation of the stabilized power supply is formed by superimposing a correction signal representing an AC voltage waveform of the power supply on an error signal relating to the output voltage, thereby using a multiplication circuit as in the prior art. This eliminates the necessity, makes it possible to control the current drawn from the AC power supply in a sinusoidal manner with a simpler circuit configuration and much lower cost than before, and to integrate the entire control system of the stabilized power supply into an integrated circuit device having a small chip size.

(C) Conventionally, an error component relating to the output voltage of a stabilized power supply is multiplied by a signal value representing an AC voltage waveform, and then used for voltage control. In the present invention, a multiplication circuit is not used. Therefore, since the error signal constituting the control signal is not interfered by the correction signal representing the waveform of the AC voltage, the gain of the voltage control system of the stabilized power supply is not affected by the instantaneous value of the waveform of the AC voltage. It is possible to accurately and stabilize the operation of the output voltage control system of the stabilized power supply while keeping it constant.

(D) When controlling the waveform of the current taken from the AC power supply according to the method of the present invention, the large-capacity capacitor conventionally used for stabilizing the input voltage applied to the stabilized power supply becomes rather an obstacle. It is sufficient to incorporate a capacitor into the rectifier circuit that can absorb the pulsation of the rectified voltage, and it is possible to reduce the cost by reducing the capacitor by two to three orders of magnitude compared to the conventional capacitor.

The method of the present invention having the above-mentioned features is particularly suitable when the stabilized power supply is a switching power supply that operates in a current mode type. In this case, a pulsating current flowing through the switching transistor as a reference signal is detected by current detection. Using a signal detected by a resistor and turning off the switching transistor at the timing when the value of the control signal cuts off the waveform of the reference signal is advantageous in simplifying the circuit configuration.

In the embodiment of the present invention, the embodiment using the voltage division by the resistance voltage dividing circuit which receives the pulsating voltage obtained by rectifying the AC voltage as the correction signal has an advantage that an accurate correction signal can be generated by a very simple circuit. In the embodiment in which the correction signal and the error signal are combined via a resistor in order to superimpose the correction signal on the error signal, the control gain of the voltage control system of the stabilized power supply that keeps the output voltage constant according to the error signal is adjusted by the resistance of the coupling resistor. This has the effect that the value can be easily and accurately set by the value.

In the embodiment of the present invention in which the waveform of the correction signal is shaped so as to dull the correction signal by the waveform shaping circuit, the load of the AC power supply voltage or the stabilized power supply varies over a wide range. In this case, it has the effect that the waveform of the current taken from the AC power supply can be accurately controlled in a sine wave shape, and for this waveform shaping, a series circuit of a Zener diode and a resistor is divided at the dividing point of the voltage dividing resistor on the power receiving side of the resistor voltage dividing circuit. The embodiment in which a plurality of waveform shaping circuits each having a different Zener breakdown voltage are used has an advantage that the waveform shaping circuit can be easily configured. This has the effect that a more accurate sinusoidal waveform can be controlled.

Further, the embodiment of the present invention in which a negative bias value is superimposed on the control signal has an effect of expanding a change range of a load of an AC power supply voltage or a stabilized power supply capable of controlling a current waveform in a sine wave shape, For this purpose, the pulsating voltage for producing the auxiliary power supply voltage for supplying the negative bias voltage to the control system of the stabilized power supply is rectified to the polarity opposite to that of the auxiliary power supply voltage. There is an advantage that the value can be set accurately with respect to the auxiliary power supply voltage, and the embodiment in which this negative bias is combined with the control signal via a resistor and superimposed on the control signal is used to make the negative bias effective by the resistance value of the coupling resistor. There is an effect that can be set easily and accurately. With a stabilized power supply using a waveform shaping circuit and a bias circuit, even if the AC power supply voltage varies over a wide range of 60 to 240 V, the power factor of the power taken from the power supply is increased to about 97%, and the harmonic component of the current is reduced to several percent or less. Can be reduced.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a switching control method for a stabilized power supply according to the present invention. FIG. 1 (a) is a circuit diagram illustrating a stabilized power supply to which the present invention is applied, and FIG. 1 (b) is a waveform shaping circuit. FIG. 4C is a circuit diagram showing still another configuration example of the waveform shaping circuit, and FIG. 4D is a waveform diagram showing a waveform example of a control signal.

FIG. 2 (a) is a circuit diagram of a rectifier circuit, and FIG.
FIG. 3 is a waveform diagram showing a waveform of an AC voltage received by a rectifier circuit and a waveform of a current taken from an AC power supply.

FIG. 3 is a circuit diagram showing a conventional converter used on the input side of a stabilized power supply for converting a current taken from an AC power supply into a sinusoidal waveform.

[Explanation of symbols]

2 Switching transistor 10 Rectifier circuit for generating input voltage of stabilized power supply 11 Capacitor for smoothing rectified voltage 20 Control circuit 30 Error signal circuit 31 Voltage detection circuit for generating error signal 32 Photocoupler for transmitting error signal 35 Correction of error signal Coupling resistance superimposed on signal 40 Resistance voltage divider circuit for correction signal 50 Waveform shaping circuit for correction signal 51 Series resistance of zener diode for waveform shaping 52 Zener diode for waveform shaping 60 Bias circuit for control signal 61 Make negative bias Rectifier diode 63 Coupling resistance that superimposes negative bias on control signal Ia Current taken from AC power supply Sa Correction signal Sc Control signal Se Error signal Sr Reference signal Ss Switching command for switching transistor Va AC voltage of AC power supply Vd Control system of stabilized power supply Auxiliary power supply voltage Vi Input voltage of stabilized power supply Vo Source output voltage

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H02M 7/06 H02M 7/06 A (56) References JP-A-4-109866 (JP, A) JP-A-3-7066 ( JP, A) JP-A-3-277172 (JP, A) JP-A-6-54536 (JP, A) JP-A-7-274574 (JP, A) International publication 95/34939 (WO, A1) (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/217 H02J 3/18 H02M 1/12 H02M 3/28 H02M 3/335 H02M 7/06

Claims (11)

(57) [Claims] A rectified voltage of an AC power supply is connected to a primary winding of a transformer.
Open and close the switching transistor via the transformer
A method for controlling the switching operation of the stabilized power supply shall be the rectifying output voltage the voltage induced in the secondary side, front
Serial creating a control signal by superimposing the correction signal with the actual substantially sinusoidal waveform to the error signal voltage and phase of the AC power source representing the difference between the target value of the output voltage, the synchronization control signals to the switching period of the stabilized power supply At the timing when the control signal value cuts off the waveform of the reference signal compared with the reference signal having the pulsating waveform
Wherein by controlling the opening and closing states of the switching transistors, almost stabilized power supply switching control method being characterized in that so as to correct the sinusoidal waveform of the AC voltage in phase with the current to take from the AC power source. 2. A rectified voltage of an AC power supply as a DC input voltage.
To control the switching operation of the regulated power supply
The difference between the actual value of the output voltage and the target value is
And has an almost sinusoidal waveform in phase with the AC power supply voltage.
Waveform correction to dull the waveform near the maximum value
A signal is superimposed on the error signal to form a control signal, and the control signal is
Pulsation synchronized with the switching cycle of the power supply
The control signal value is compared with the reference signal having a waveform.
The switching transistor opens at the timing when the waveform is cut.
By controlling the closed state, the current
So that the waveform is corrected to be almost sinusoidal in phase with the AC voltage
Switching control method for stabilized power supply
formula. 3. A method according to claim 1 or 2,
A switching control method for a stabilized power supply, wherein a voltage divided by a resistance voltage dividing circuit that receives a pulsating voltage obtained by rectifying an AC voltage is used as a correction signal. 4. A switching control method for a stabilized power supply according to claim 3 , wherein an error signal and a correction signal as a resistance voltage division are superposed by coupling via a resistor. 5. The switching control method for a stabilized power supply according to claim 1, wherein the correction signal is subjected to waveform shaping so as to dull a waveform near its maximum value. 6. The method of claim 2 or 5,
A waveform shaping circuit comprising a zener diode and a resistor connected in series for shaping the waveform of the correction signal is connected to a dividing point of a voltage dividing resistor on a power receiving side in parallel with a resistor voltage dividing circuit. Switching control method for stabilized power supply. 7. A switching control method for a stabilized power supply according to claim 6 , wherein a plurality of waveform shaping circuits having different Zener breakdown voltages are connected in parallel. 8. The method according to claim 1 or 2,
A switching control method for a stabilized power supply, wherein a negative bias value is superimposed on a control signal. 9. A method according to claim 8 , wherein a pulsating voltage for producing an auxiliary power supply voltage for supplying power to a control system of the stabilized power supply as a negative bias value is rectified to a polarity opposite to that of the auxiliary power supply voltage. A switching control method of a stabilized power supply characterized by being made. 10. A method according to claim 1 or 2, stabilized power supply switching control method, wherein the stabilizing power supply is a switching power supply for the operation of the current-mode type. 11. A switching control method for a stabilized power supply according to claim 10 , wherein a detection signal of a pulsating current flowing through the switching transistor is used as a reference signal.