JPH10174438A - Power supply unit for ac input - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for providing the tertiary coil winding of a power conversion transformer and a resistor for suppressing a rush current by controlling the conduction resistance of a resistance control circuit according to the output of a charge/discharge circuit. SOLUTION: When a power supply switch SW1 is thrown SW1 is thrown, a current is supplied to a second rectifying circuit 5, a voltage applied to an internal capacitor gradually increases, and the voltage is applied to a resistance control circuit 6 as a limited voltage. Since a small voltage applied initially, the conduction resistance of the resistance control circuit 6 is extremely large, and a rush current is suppressed due to the large resistance of the resistance control circuit 6, thus suppressing a current IP that flows through the resistance control circuit 6. Also, since a current-suppressing resistor and the tertiary coil winding of a power conversion transformer are not required, a device can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC-DC converter type AC input power supply device which uses an AC input and controls the conduction time of a switching element to stabilize a DC output voltage. The present invention relates to an AC input power supply device that suppresses inrush current (rush current) flowing when the power supply is turned on.

[0002]

2. Description of the Related Art AC-D for stabilizing a DC output voltage by inputting an alternating current and controlling a conduction time of a switching element.
An AC input power supply device of the C converter type generally has a circuit for suppressing an excessive rush current (rush current) flowing when a power switch is turned on. The reason is that firstly, the input power equipment can be made smaller, and secondly, a small rectifier diode can be used.

FIG. 6 is a diagram showing a configuration example of a conventional circuit of an AC input power supply device. In the figure, reference numeral 1 denotes an AC power source for generating an AC voltage, D ₁ to D ₄ are rectifying diodes, 3
Is a bridge rectifier circuit composed of these diodes, which inputs an AC voltage and converts it into a DC voltage. SW ₁ is a power supply switch to turn on / off the AC power supply.

[0004] CR ₁ is connected thyristors in series with the bridge rectifier circuit 3, R ₁ is a resistor connected in parallel with the thyristor CR _1. The output of the bridge rectifier circuit 3 is connected via the parallel circuit of the thyristor CR ₁ and resistor R ₁ to the power conversion transformer T ₁ of the primary winding N1.

[0005] High-frequency transformer T₁Has a first winding N1 and
A second winding N2 and a third winding N3 are provided. Volume 1
The wire N1 and the third winding N3 are connected in series,
The other end of the winding N3 is a rectifying diode D₇Contact the anode
Has been continued. R_FourIs the diode D₇Connected in series with
Resistance, C_ThreeIs a smoothing capacitor connected to the other end of the resistor R4
It is. Capacitor C_ThreeThe voltage charged to the
Lister CR₁Connected to the gate. Thyristor C
R₁And resistance R₁And a power conversion transformer T ₁No.
3 windings N3, diode D₇, Resistance R_FourAnd capacitor C
_ThreeThese constitute an inrush current suppression circuit.

C ₁ is a smoothing capacitor for smoothing the output of the bridge rectifier circuit 3 and is connected between one end of the thyristor CR ₁ and a common line. As the capacitor C _1, typically electrolytic capacitor having a large capacity is used. T
R ₁ is a field effect transistor (F) serving as a switching element connected in series to the first winding of the power conversion transformer T ₁ .
ET).

On the secondary side of the power conversion transformer T ₁ ,
D _5, D ₆ is a rectifying diode which converts the high frequency voltage generated in the secondary side (second winding N2 side) into a DC voltage. L
₁ reactor, C ₂ for smoothing is connected to the cathode side of the rectifier diode is a smoothing capacitor connected between the other end of the reactor L ₁ and the common line.

[0008] R_TwoAnd R_ThreeIs a voltage dividing resistor connected in series,
R₀Is a load resistance. 2 is a voltage dividing resistor R_TwoAnd R_ThreeConnection
Input the divided voltage extracted from the point as the control voltage,
Switching transistor TR₁Control the conduction time of
And the power conversion transformer T₁Output voltage on the secondary side of
This is a switching control circuit that makes The switch
The ringing control circuit 2 is electrically insulated between the input side and the output side.
Then, the power conversion transformer T ₁The primary and secondary sides of the
Power supply device can be realized. Configuration like this
The operation of the circuit thus described is as follows.

FIG. 7 is a diagram showing operation waveforms of various parts of the conventional circuit. (A) the input waveform e _i of the AC power supply 1, (b)
The on / off state of the power switch SW1, shows (c) is a voltage V _c1 of the smoothing capacitor C _1, (d) is an input current I _p flowing through the rectifier circuit 3, respectively.

[0010] Now, when turning on the power switch SW _1, the output of the bridge rectifier circuit 3 is a DC pulsating as indicated by the broken line in (a). This pulsating is smoothed by the smoothing capacitor C _1, a waveform as shown in (c). Now, if the resistance R ₁ is considered the state that is not connected. At the time of power switch SW ₁ was charged, the charge in the smoothing capacitor C ₁ is not stored, the capacitor voltage V _c1 is zero. Therefore, the voltage rectified by the bridge rectifier circuit 3 is all the way takes the capacitor C _1, a large inrush current (rush current) flows.

However, since the resistor R ₁ is actually connected, the inrush current that flows is V / R _{1 if the} output of the bridge rectifier circuit is V and R ₁ is used as the value of the resistor R ₁ as it is. Will be suppressed. At this point, the capacitor C ₃ thyristor CR ₁ since the voltage does not occur is off. As a result, those I _p1 (input current from the AC power source 1 side) power switch SW _1-on inrush current was suppressed as shown in (d) of FIG.

[0012] During this time the voltage is generated in the third winding N3 of the power conversion transformer T _1, after being rectified by the diode D _7, enters constituted charging circuit a resistor R ₄ and the capacitor C _3. In the charging circuit, gradually increases the voltage across capacitor C _3, reaches a certain predetermined value, the thyristor CR ₁ is rapidly turned on. After that, thyristor C
R ₁ is regularly on unless the power switch is off SW _1. In the on state, since the resistance value is as small as about several Omega, a parallel circuit of a thyristor CR ₁ and the resistance R ₁ can be regarded as being short-circuited.

[0013] In this way, after suppressing the inrush current, it is charged charges the smoothing capacitor C _1, the voltage gradually rises, the switching control circuit 2 controls the switching transistor TR _1, DC-DC converter Operation. At this time, the AC voltage generated on the secondary side of the power conversion transformer T ₁ is rectified by the full-wave rectifier circuit,
A flat DC voltage by the smoothing action of reactor L ₁ and the smoothing capacitor C _2. A direct current is supplied to the load R ₀ .

The secondary side DC voltage value is determined by the resistance R_TwoAnd R_Threeby
Monitored by the voltage dividing circuit and given to the switching control circuit 2.
Can be The switching control circuit 2 outputs the output voltage value
Is compared with the reference value, and the output voltage becomes constant.
Switching transistor TR ₁Control the conduction time of
(PWM operation).

[0015]

In the above-described conventional power supply device, a thyristor is used to suppress inrush current.
Power switch-on (SW ₁ on) but suppresses the overcurrent flowing at, in order to operate this thyristor,
Third winding N3 was required power conversion transformer T _1.
In addition, the smoothing capacitor C _{1 is} initially set when the power switch is turned on.
It requires resistance R ₁ for suppressing the rush current which charges, the large current to flow, high power resistance was required for this resistor R _1. This was a factor that hindered miniaturization.

[0016] Without this resistor R _1, the power switch S
Be charged to W _1, since the thyristor CR ₁ is in the OFF state, does not flow the charging current to the smoothing capacitor C _1, it can not operate while this is a power supply.

The third winding N of the power conversion transformer T ₁
Without 3, even if the power switch SW ₁ is turned on, it is impossible to turn on the thyristor, a smoothing capacitor C ₁
The charging current does not flow through the power supply, and the power supply cannot operate as it is.

The present invention has been made in view of such a problem, and does not require the provision of a third winding of a power conversion transformer or a resistor for suppressing an inrush current, and is a compact AC input power supply device. It is intended to provide.

[0019]

[Means for Solving the Problems]

(1) FIG. 1 is a principle circuit diagram of the present invention. 6 are denoted by the same reference numerals. In the figure, 1 is an AC power supply, SW ₁ is a power on / off switch, and 3 is a first rectifier circuit that receives and rectifies an AC voltage from the AC power supply. As the first rectifier circuit 3, for example, a bridge rectifier circuit using four rectifier diodes as shown in FIG. 6 is used.

4 is a second rectifier which also receives an AC input and rectifies it.
Rectifier circuit. As the second rectifier circuit, a half-wave rectifier circuit as shown in FIG. 2 is used. Reference numeral 5 denotes a charge / discharge circuit that receives an output of the second rectifier circuit 4 and charges and discharges an internal capacitor. 6 are connected in series to the primary side of the power conversion transformer T _2, it receives the output of this charge-discharge circuit 5 as a control signal, a resistance control circuit that conduction resistance value is changed by the control signal. T ₂ are the power conversion transformer consisting of primary and secondary windings, the third winding does not have. The resistance value control circuit 6 includes a power conversion transformer T ₂
Are connected in series to the primary side.

C ₁ is a smoothing capacitor for smoothing the output of the first rectifier circuit 3, and SW ₂ is a switching element for turning on / off the DC voltage stored in the smoothing capacitor C ₁ via a power conversion transformer T _2. is there. 7 is a third rectifier circuit for rectifying the secondary output of the power conversion transformer T _2.
C ₂ is a smoothing capacitor for smoothing the output of the third rectifier circuit 7. DC output is taken out from both ends of the capacitor C _2. A switching control circuit ₂ detects the output voltage, compares the output voltage with a predetermined reference value, and controls the conduction time of the switching element SW2 so that the output voltage becomes a predetermined value.

According to the configuration of the present invention, the power switch S
The W ₁ when turned on, the current from the second rectifier circuit 4 to charge and discharge circuit 5 is supplied, gradually increasing the voltage applied to the internal capacitors, the control voltage the voltage across the internal capacitor to the resistance value control circuit 6 Since a small voltage is initially applied, the conduction resistance of the resistance value control circuit 6 is extremely large, and the inrush current is suppressed due to the high resistance of the resistance value control circuit 6. As a result, the current _Ip flowing through the resistance value control circuit 6 is suppressed. Further, according to the configuration of the present invention, since the third winding of a conventional current suppressing resistor R ₁ and the power conversion transformer T ₂ becomes unnecessary, thereby downsizing the apparatus.

(2) In this case, the resistance value control circuit 6 is characterized by using a field effect transistor whose resistance between the drain and the source changes according to the voltage applied to the gate.

According to the configuration of the present invention, the resistance value control circuit 6 can be changed in accordance with the control voltage by using a field effect transistor (FET) as the resistance value control circuit 6, so that the resistance value control circuit 6 has a very simple configuration. Can be realized.

(3) As the rectifier circuit 4, a half-wave rectifier circuit using one diode or a full-wave rectifier circuit using two diodes is used. According to the configuration of the present invention, a circuit for supplying a current to the charge / discharge circuit 5 can be realized with a simple configuration.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a circuit diagram showing a first embodiment of the present invention. 1 and 6 are denoted by the same reference numerals. D ₁₀ is a diode which constitutes the second rectifier circuit. The cathode of the diode D ₁₀ of resistor R ₅ is connected, the other end of the resistor R ₅ is connected to the gate G of the field effect transistor TR _2.
Transistor TR ₂ is connected in series to the primary side of the power conversion transformer T _2.

[0027] C ₄ is capacitor connected between the other end and the common line of the resistor R _5, R ₆ are resistors connected in parallel with the capacitor C _4, D ₇ is the voltage clamp is also connected in parallel with capacitor C ₄ Zener diode for These resistors R ₅ and R ₆ , capacitor C ₄ , zener diode D ₇
These constitute the charge / discharge circuit 5 of FIG.

The drain D and the source S of the transistor TR ₂ are connected in series to the primary side of the power conversion transformer T ₂ ,
The transistor TR ₂ constitutes a resistance control circuit 6 which conduction resistance between the drain D and the source S by a control voltage applied to the gate is changed (see FIG. 1). The output voltage of the charging and discharging circuit is applied between the gate G and the source S of the transistor TR _2, and controls the conduction resistance between the drain D and the source S of the transistor TR _2. Other configurations, that there is no third winding to the power converter transformer T _2, is the same as FIG. 6, except that there is no ignition circuit of thyristor CR ₁ and the current suppression resistors R ₁ and thyristor CR _1. The operation of the circuit thus configured will be described as follows.

FIG. 3 shows operation waveforms of various parts of the circuit of the present invention.
FIG. (A) is an AC input voltage waveform, and (b) is an
Source switch SW₁(C) is a smooth condenser
Sensor C₁Voltage applied to_c1And (d) shows the transistor T
R_TwoGate-source voltage V _GSAnd (e) the resistance value system
Use (for suppressing inrush current) field effect transistor TR_Twoof
The resistance between the drain D and the source S is shown in FIG.
Input current I_pAre respectively shown.

[0030] The (1) When the power switch SW ₁ is turned when the power switch SW ₁ shown in FIG. 3 (b) is turned on, (positive part of the sine wave voltage) half-wave of the AC input voltage e _i rectified by rectifier diode D _10, charges the capacitor C ₄ of the charging and discharging circuit through the resistor R _5. The voltage across the capacitor C ₄ is gradually increased. Voltage applied to the gate G of the transistor TR _2, since initially is 0, the conductive resistance between the drain D and the source S (e)
As shown in FIG. Thus, the input current I _p flowing through the smoothing capacitor C ₁ is suppressed to a small value, the inrush current is suppressed. _{Ip1 in} FIG. 3 (f) indicates the suppressed inrush current value. It can be seen that a current suppression effect similar to that of the conventional device shown in FIG.

Capacitor C_FourThe voltage applied to
As it rises as shown in (d), Transis
TA TR_TwoThe resistance between the drain D and the source S is the same as (e).
As shown, it gradually decreased from the initial value of several MΩ to several mΩ.
Go on. And the capacitor C _FourVoltage applied to
When the value exceeds the value, the Zener diode D₇Is the value
The transistor TR_Twoof
Conduction resistance between drain D and source S is a constant value of several mΩ
Becomes

On the other hand, the smoothing capacitor C ₁ is charged with electric charge from the bridge rectifier circuit 3 as shown in FIG. 3C, and when the voltage V _c1 applied to the smoothing capacitor C ₁ reaches a predetermined value, switching control is performed. The circuit 2 starts a switching operation. I _p figure is the current flowing at this time in the field-effect transistor TR _2. The high-frequency AC transmitted to the secondary side via the power conversion transformer T ₂ is rectified by a rectifier circuit including diodes D ₅ and D ₆ , and the reactor L ₁
And a DC voltage of a flat characteristic is smoothed by the smoothing capacitor C _2. This DC voltage becomes the output of the power supply,
The load current is supplied to the load _R0 .

On the other hand, the output voltage is detected by a voltage dividing circuit composed of resistors R ₂ and R _3, and applied to the switching control circuit 2. The switching control circuit 2
Compares this output voltage with a predetermined reference voltage,
So that the output voltage becomes a predetermined value, it performs the PWM control for controlling the conduction time of the switching transistor TR _1.
Here, when the input and output of the switching control circuit 2 are electrically insulated, this power supply becomes a power supply in which the primary side and the secondary side of the power conversion transformer are completely insulated.

[0034] In this case, with the operation of the field effect transistor TR ₂ which functions as a resistance control circuit will be described in detail. Figure 4 is a diagram showing an operating characteristic example of the transistor TR _2. (A) the voltage between the gate and the source of the TR ₂ V
_GS , (b) is the resistance (conduction resistance) R _DS between the drain and source of TR ₂ , and (c) is the input current I _p (in the figure, _ID is the current flowing between the drain and source of the transistor) Are shown).

When the power switch SW ₁ is turned on, the voltage of the charge / discharge circuit 5 (the voltage V _GS applied between the gate and the source of the transistor TR ₂ ) gradually increases as shown in FIG. Go. While the gate-source voltage V _GS is equal to or lower than the predetermined value, the resistance R _DS between the drain and the source of the transistor TR ₂ is several MΩ as shown in FIG. Accordingly, the inrush current flowing when the power switch SW ₁ was charged in the amplitude of the AC input e _i, the drain of the transistor TR ₂ - represented as e _i / R _DS between the source resistance as R _DS, suppressing the rush current Can be. I _ps of (c) an input current at this time, its value is, for example, about 0.1 mA.

Here, when the gate-source voltage V _GS reaches a predetermined value, the drain-source resistance R _DS rapidly decreases as shown in (b) and drops to about several mΩ. As a result, the current I _D flowing through the transistor TR ₂ has one peak as shown in (c). _Assuming that this peak value is I _p1 , I _p1 is represented by the following equation.

I_p1= (E_i-V_c1) / R_DS Where e_iIs the amplitude of the AC input voltage, V_ciIs a smooth conde
Sensor C₁, R _DSIs the transistor TR_TwoDre
This is the resistance between the input D and the source S. Current peak at this time
The value of the value is, for example, about 10A.

[0038] (2) When the power switch SW ₁ cross when the power switch SW ₁ to the cross-sectional, the voltage applied to the gate G of the inrush current suppression transistor TR ₂ is reduced rapidly. Charged in the capacitor C ₄ (charged) once was charge is to be consumed by the resistor R ₆ which are connected in parallel thereto. As a result, the transistor TR ₂ is suddenly turned off.

Here, if the discharge resistor R ₆ is not provided, the charge charged in the capacitor C ₄ remains without being discharged, and when the power switch SW ₁ is turned on next time, there is a conduction resistance of the transistor TR _2. As a result, an excessive rush current may flow. Therefore, in order to discharge the electric charge charged in the capacitor C _4, are provided resistors R _6, and allowed to constitute a discharge circuit.

At the same time, the voltage across the smoothing capacitor C ₁ also decreases, the device stops operating and the output voltage goes to zero. Thus, according to this embodiment, by controlling the gate voltage applied to gate G of the field effect transistor TR ₂ which operates as a resistance control circuit in the charge-discharge circuit that occur when the power switch SW ₁ is turned on Inrush current can be greatly reduced. Further, according to this embodiment, since the third winding and the current suppressing resistor of the power conversion transformer as in the conventional device as the inrush current suppressing circuit are not required, the device can be downsized.

Further, according to this embodiment, by using a field effect transistor in which the resistance between the drain and the source changes according to the voltage applied to the gate as the resistance value control circuit 6, the resistance value control circuit can be made extremely simple. It can be realized with a configuration.

Further, according to this embodiment, a current supply circuit having a simple configuration can be realized by using a single diode as a rectifier circuit for supplying a charge / discharge circuit.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention. The same components as those in FIG. 2 are denoted by the same reference numerals. Embodiment Example differs from FIG. 2 is that the second rectifier circuit 4 is in the full-wave rectifier circuit by the diode D ₁₀ and a diode D _11. The anode of the diode D _11, the other end of the power supply 1 is connected. Other configurations are exactly the same as those in FIG. The operation of the circuit thus configured will be described as follows.

[0044] When the power switch SW ₁ is turned on, a full-wave rectifier circuit by the diode D ₁₀ and a diode D ₁₁ is full-wave rectification of the input AC voltage e _i. The current from the full-wave rectifying circuit 4 to the charging and discharging circuit is supplied, the charging voltage of the capacitor C ₄ (V _GS), as indicated by the broken line in FIG. 3 (d), higher than the case of the half-wave rectifier circuit The voltage waveform of By using a full-wave rectifier circuit, the capacitor C ₄
Can be reduced. Other operations and effects are exactly the same as those of the embodiment shown in FIG.

In the above-described embodiment, a field effect transistor (FET) is used as the resistance value control circuit 6.
The present invention is not limited to this, and any circuit may be used as long as the circuit has a configuration in which the conduction resistance value is changed by receiving a control voltage. Further, although a field effect transistor is used as a switching element of the DC-DC converter section, the present invention is not limited to this, and other switching elements, for example, a bipolar transistor or the like can be used.

[0046]

As described above in detail, according to the present invention, (1) an AC-DC converter system in which an alternating current is input and a conduction time of a switching element is controlled to stabilize a direct current output voltage. In a power supply device, a resistance control circuit connected in series to a primary side of a power conversion transformer and having a resistance value changed by a control voltage, a rectifier circuit for inputting and rectifying an AC voltage, and receiving an output of the rectifier circuit By providing a charge and discharge circuit, and controlling the conduction resistance of the resistance value control circuit with the output of the charge and discharge circuit, there is no need to provide a third winding of the power conversion transformer or a resistor for suppressing inrush current, In addition, a small AC input power supply device can be provided.

(2) In this case, by using a field effect transistor in which the resistance between the drain and the source changes according to the voltage applied to the gate as the resistance value control circuit, the conduction resistance can be changed by the control voltage. By using a field effect transistor (FET) as the possible resistance value control circuit 6, the resistance value control circuit 6 can be realized with an extremely simple configuration.

(3) Further, by using a half-wave rectifier circuit using one diode or a full-wave rectifier circuit using two diodes as the rectifier circuit, a circuit for supplying a current to the charge / discharge circuit is provided. It can be realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a principle circuit diagram of the present invention.

FIG. 2 is a circuit diagram showing a first embodiment of the present invention.

FIG. 3 is a diagram showing an example of an operation waveform of each part of the circuit of the present invention.

FIG. 4 is a diagram showing an example of an operation characteristic of TR2.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional circuit.

FIG. 7 is a diagram illustrating an example of an operation waveform of each unit of the conventional circuit.

[Explanation of symbols]

Reference Signs List 1 AC power supply 2 Switching control circuit 3 First rectifier circuit 4 Second rectifier circuit 5 Charge / discharge circuit 6 Resistance value control circuit 7 Third rectifier circuit C ₁ Smoothing capacitor C ₂ Smoothing capacitor T ₂ Power conversion transformer SW ₁ Power supply Switch SW ₂ switching element

Claims (3)

[Claims] An AC-D for stabilizing a DC output voltage by inputting an AC and controlling a conduction time of a switching element.
In a C converter type power supply device, a resistance control circuit connected in series to a primary side of a power conversion transformer and having a resistance value changed by a control voltage, a rectifier circuit for inputting and rectifying an AC voltage, and the rectifier circuit And a charge / discharge circuit for receiving the output of the AC input power supply, wherein the output of the charge / discharge circuit controls the conduction resistance of the resistance value control circuit. 2. The transistor according to claim 1, wherein the resistance control circuit uses a field-effect transistor in which a resistance between a drain and a source changes according to a voltage applied to a gate.
An AC input power supply as described. 3. The AC input power supply device according to claim 1, wherein a half-wave rectifier circuit using one diode or a full-wave rectifier circuit using two diodes is used as the rectifier circuit.