JPH10215582A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply in which harmonic components are reduced, even for the low input voltage part. SOLUTION: In the low-voltage section of a full-wave rectifier circuit 1, voltage of a second capacitor C2 drops as the voltage of a first capacitor C1 drops, with respect to the filing voltage of a charging capacitor C3. Consequently, the amplitude is increased by an inductance L2, and the second capacitor C2 and the input decreases but flows continuously. When the voltage of a capacitor C8 drops and a Zener diode ZD1 is turned off, for example, and a transistor Q5 is turned on to connect a capacitor C14 in parallel with a capacitor C7, a combined capacitance is increased and the base amount of a transistor Q1 is increased, thus increasing the output from an inverter circuit 3. Since the voltage of the second capacitor C2 approaches 0V at the time of zero-cross, an input current is supplied from an AC commercial power supply e) side and the second capacitor C2 resonates, even at a low input voltage part. Consequently, a substantially sinusoidal continuos input current having no pause is provided, and harmonic components are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device in which harmonics of an input current are reduced.

[0002]

2. Description of the Related Art Conventionally, as a power supply device of this type, for example, a configuration described in Japanese Patent Application Laid-Open No. 5-212774 is known. In the discharge lamp lighting device described in Japanese Patent Application Laid-Open No. 5-217774, a full-wave rectifier circuit is connected to a commercial AC power supply, and a first capacitor and a second capacitor are connected to output terminals of the full-wave rectifier circuit. ing. Further, a partial smoothing circuit having a charging capacitor and an inductor is connected to the second capacitor, and a parallel resonance circuit and a transistor of the capacitor and the inductor are connected in series to the partial smoothing circuit. Is connected to a fluorescent lamp.

[0003] By the high-frequency switching operation of the transistor, resonance occurs in the parallel resonance circuit, a resonance voltage is generated, and the fluorescent lamp is lit at high frequency.

[0004]

However, in the discharge lamp lighting device described in Japanese Patent Application Laid-Open No. Hei 5-221774, the voltage of the second capacitor C2 is low in a portion where the input voltage is low due to variations in parts and the like. 0V, the voltage of the second capacitor becomes higher than the input voltage,
There is a problem that the input current is not supplied to the load, and the harmonic components included in the input current cannot be sufficiently removed.

The present invention has been made in view of the above problems, and has as its object to provide a power supply device that reduces harmonic components even in a portion where the input voltage is low.

[0006]

According to a first aspect of the present invention, there is provided a power supply device comprising: a rectifier for rectifying an AC from an AC power supply; a first capacitor connected in parallel to an output terminal of the rectifier; And a diode connected in series with one polarity to one end of the first capacitor, and the first
A second capacitor connected in parallel with the capacitor of
A partial smoothing circuit having an inductor and a charging capacitor, connected in parallel to the second capacitor for charging the charging capacitor with a voltage lower than the maximum instantaneous voltage value of the output of the rectifier; And a parallel resonance circuit having a resonance inductor, an inverter having a switching element connected in series to the parallel resonance circuit, connected in parallel to the partial smoothing circuit, and generating a high-frequency voltage by a switching operation of the switching element A circuit, input voltage detection means for detecting an input voltage input to the first capacitor, and control means for increasing the output of the inverter circuit when the input voltage detected by the input voltage detection means is low. It is provided. The inverter circuit supplies the input current from the first capacitor and the second capacitor when the output level of the rectifier is equal to or higher than the charge level of the charging capacitor, and the output level of the rectifier is lower than the charge level of the charging capacitor. Sometimes, the input current is supplied from the partial smoothing circuit, and the switching operation of the switching element causes the parallel resonance circuit to resonate to reduce harmonics.
When the input voltage detected by the input voltage detection means is low, the output of the inverter circuit is increased by the control means, the potential of the second capacitor is made lower than the input voltage, and the input current is caused to flow to the load, so that the input voltage is reduced. Lowers the harmonics contained in the input current even when is low.

According to a second aspect of the present invention, a first capacitor connected to an AC power supply, a rectifier connected to the first capacitor, and a second capacitor connected to the rectifier.
A smoothing circuit connected in parallel to the second capacitor that charges the charging capacitor with a voltage lower than the maximum instantaneous voltage value of the output of the rectifier. And a parallel resonance circuit having a resonance capacitor and a resonance inductor,
An inverter circuit that has a switching element connected in series to the parallel resonance circuit, is connected in parallel to the partial smoothing circuit, and generates a high-frequency voltage by a switching operation of the switching element; Input voltage detection means for detecting an input voltage to be input,
Control means for increasing the output of the inverter circuit when the input voltage detected by the input voltage detection means is low. The inverter circuit supplies the input current from the first capacitor and the second capacitor when the output level of the rectifier is equal to or higher than the charge level of the charging capacitor, and the output level of the rectifier is lower than the charge level of the charging capacitor. Sometimes, the input current is supplied from the partial smoothing circuit, the parallel resonance circuit is resonated by the switching operation of the switching element to reduce harmonics, and the inverter is controlled by the control means when the input voltage detected by the input voltage detection means is low. By increasing the output of the circuit and lowering the potential of the second capacitor below the input voltage,
By flowing the input current to the load, harmonics included in the input current are reduced even when the input voltage is low.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the power supply device of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, an input terminal of a full-wave rectifier circuit 1 as a rectifier of a diode bridge is connected to a commercial AC power supply e via an inductor L1, and a capacitance is connected to an output terminal of the full-wave rectifier circuit 1. Is connected to the first capacitor C1, which has a diode D1,
And a second capacitor C1 having a smaller capacity than the first capacitor C1.
The series circuit of the capacitor C2 is connected.

A partial smoothing circuit 2 is connected to the second capacitor C2. The partial smoothing circuit 2 is connected to a series circuit of a charging capacitor C3, an inductor L2 and a diode D2, and an inductor L1 and a diode D2. In the meantime,
Diode D3 is connected.

Further, an inverter circuit 3 is connected to the partial smoothing circuit 2. The inverter circuit 3 includes a leakage flux type inverter transformer as a resonance inductor.
The primary winding Tr1a of Tr1, the parallel resonance circuit 4 of the resonance capacitor C4, and the collector and the emitter of the transistor Q1 serving as a switching element are connected.

The secondary winding of the inverter transformer Tr1
The filaments FL1 and FL2 of the fluorescent lamp FL as a discharge lamp are connected to Tr1b via a DC cut capacitor C5 and a primary winding CT1a of a current transformer CT1 for current feedback. These filaments FL1 and FL2 are The starting capacitor C6 is connected. Note that a resistor R1 is connected in parallel with the series circuit of the capacitor C5 and the primary winding CT1a of the current transformer CT1.

The load circuit 5 is composed of a fluorescent lamp FL or the like.

Further, a parallel circuit of a secondary winding CT1b of the current transformer CT1 and a diode D4 and a capacitor C7 are connected in series between the base and the emitter of the transistor Q1, and a series circuit of a diode D5 and a resistor R2. Is connected.

On the other hand, an input voltage detection circuit 6 as input voltage detection means is connected in parallel with the first capacitor C1. In the input voltage detection circuit 6, a series circuit of a resistor R3 and a capacitor C8 is connected in parallel with the first capacitor C1, and a connection point of the resistor R3 and the capacitor C8 is connected to a transistor Q2 via a zener diode ZD1.
The base is connected.

Similarly, a series circuit of a resistor R4 and a capacitor C11 is connected in parallel to the first capacitor C1, and a series circuit of a zener diode ZD2 and a capacitor C8 is connected in parallel to the capacitor C11. ing.

Further, a series circuit of a resistor R6 and a resistor R7 is connected in parallel with the second capacitor C2, and the collector and the emitter of the transistor Q2 are connected to both ends of the resistor R7.

A series circuit of a diode D6 and a capacitor C12 is connected between the collector and the emitter of the transistor Q1, and a connection point of the diode D6 and the capacitor C12 is connected via a resistor R8, a resistor R9, a variable resistor R10 and a resistor R11. Connected to the negative electrode of the full-wave rectifier circuit 1. Also,
The drain and source of the field effect transistor Q3 are connected between both ends of the resistor R11.
Is connected to a connection point of the resistors R6 and R7. Further, the connection point of the resistor R8 and the resistor R9 is connected to the base of the transistor Q4, and the emitter of the transistor Q4 is connected via the resistor R12 to the resistor R4 and the capacitor C1.
1 and the collector is connected to resistor R13 and resistor
It is connected to the negative electrode of the full-wave rectifier circuit 1 via R14.
A capacitor C13 is connected in parallel with the resistor R14.The capacitor C13 is connected to the gate of the field effect transistor Q5 via the resistor R15.The drain and source of the field transistor Q5 are connected to the capacitor C7 via the capacitor C14. And a control circuit 7 as a control means.

Next, the operation of the above embodiment will be described.

First, the transistor Q1 of the inverter circuit 3
When a switching operation is performed and a oscillating operation is performed, a high-frequency voltage is generated by a resonance action of the inverter transformer Tr1 and the charging capacitor C3, and a high-frequency voltage is also induced in the secondary winding Tr1b. Then, based on the voltage induced in the secondary winding Tr1b, power is supplied to the fluorescent lamp FL, and the fluorescent lamp FL is started and lit by resonance of the inverter transformer Tr1 and the capacitor C6. Then the current transformer CT
A base current is supplied to the base of the transistor Q1 by the secondary winding CT1b, and the transistor Q1 is oscillated.

When the transistor Q1 is turned on, a current flows through the primary winding Tr1a of the inverter transformer Tr1 and a current flows through the charging capacitor C3, the inductor L2, and the diode D3, thereby charging the charging capacitor C3. Then, a DC voltage lower than the peak value of the pulsating voltage from the full-wave rectifier circuit 1 can be stored in the charging capacitor C3.

Here, a description will be given of a section in which the pulsating voltage of the full-wave rectifier circuit 1 is higher than the charging voltage of the charging capacitor C3 and a section in which the pulsating voltage is lower than the charging voltage.

First, when the transistor Q1 of the inverter circuit 3 is turned on at an arbitrary time in a section where the pulsating voltage of the full-wave rectifier circuit 1 is higher than the charging voltage of the charging capacitor C3, the primary winding Tr1a of the inverter transformer Tr1 is turned on. Most of the current is supplied from the first capacitor C1, and part of the current is supplied from the second capacitor C2. The combined capacity of the first capacitor C1 and the second capacitor C2 is a capacity sufficient to provide the energy required by the inverter circuit 3. These first capacitor C1 and second capacitor C2
In accordance with the current supply from the above, energy becomes an input current and flows in from the commercial AC power supply e side. Then, an operation is performed so as to accompany the switching operation of the transistor Q1 in response to the change of the pulsating voltage, and the small and equal amplitude of the high frequency of the inverter operation of the inverter circuit 3 along the sine wave value of the AC voltage becomes full-wave. The voltage value of the rectifier circuit 1 is superimposed on all high sections.

That is, in the section where the voltage value of the full-wave rectifier circuit 1 is high, the first capacitor C1 and the second capacitor C2
Is a value obtained by satisfying the energy given by the supplied pulsating voltage with respect to the energy required by the inverter circuit 3.

For this reason, both the first capacitor C1 and the second capacitor C2 have a small ripple component, a small amount of heat, and can improve the operation reliability.

Then, in a section where the voltage value of the full-wave rectifier circuit 1 is high, the charging capacitor C3 is charged when the transistor Q1 is turned on. Note that, in a section where the voltage value of the full-wave rectifier circuit 1 is high, the discharge is not performed from the charging capacitor C3 to the inverter circuit 3 side.

When the instantaneous voltage of the commercial AC power supply e is high and the input voltage from the first capacitor C1 is high, the voltage of the capacitor C8 is high.
ZD1 turns on and transistor Q2 turns on. As a result, no gate voltage is applied to the gate of the field effect transistor Q3, and current flows through the resistor R11, so that the voltage dividing ratio is reduced, the base amount of the transistor Q4 is not increased, and the capacitor C13 is not charged. Since no gate voltage is applied to Q5, the field effect transistor Q5
Is turned off. Therefore, the capacitor C14 is not connected to the capacitor C7, and the capacitance remains small, so that the base frequency of the transistor Q1 remains unchanged and the oscillation frequency remains high, so that the output of the inverter circuit 3 remains unchanged.

Next, in a section where the voltage value of the full-wave rectifier circuit 1 is low, when the pulsating sine wave voltage of the full-wave rectifier circuit 1 starts to decrease with respect to the charging voltage of the charging capacitor C3, the transistor Q1 is turned on. When turned on, the current to the primary winding Tr1a of the inverter transformer Tr1 is first supplied from the second capacitor C2. Since the capacity of the second capacitor C2 is not enough to provide the energy required by the inverter circuit 3, the current flowing through the primary winding Tr1a after the transistor Q1 is turned on increases as the current of the second capacitor C2 increases. The voltage drops. Then, from the time when the voltage of the second capacitor C2 decreases to the voltage of the first capacitor C1, the first capacitor C1 supplies energy to the inverter circuit 3 that is insufficient in the second capacitor C2.

Then, the voltage is supplied until the transistor Q1 is turned off. However, the decrease in the voltage of the second capacitor C2 after the start of the energy supply from the first capacitor C1 is reduced. In addition, the energy supply from the first capacitor C1 to the inverter circuit 3 causes a corresponding amount of energy to flow as an input current from the commercial AC power supply e side.

On the other hand, the release of energy of the charging voltage of the charging capacitor C3 is delayed due to the transient impedance of the inductor L1, and the energy is released immediately before the transistor Q1 is turned off. And transistor Q1
Is turned off, the charging voltage of the charging capacitor C3 becomes a voltage supply source to the series circuit of the inductor L2, the diode D2, and the second capacitor C2. Here, since the inductor L2 and the second capacitor C2 are set so as to obtain an oscillating resonance, the charging of the second capacitor C2 is performed in a sine wave shape. This charging is increased in the inverter circuit 3 to a voltage at which the energy supply does not become insufficient when the transistor Q1 is turned on next time. Also,
When the transistor Q1 is turned off, resonance occurs between the resonance capacitor C4 and the inverter transformer Tr1.

Then, as the voltage of the first capacitor C1 decreases with respect to the charging voltage of the charging capacitor C3, the voltage of the second capacitor C2 decreases.
Of the capacitor C2 increases. Further, although the input current decreases, the current flows continuously.

As described above, the continuous flow of the input current from the commercial AC power supply e prevents a harmonic component from intervening in the input current.

When the instantaneous voltage of the commercial AC power supply e is low and the input voltage from the first capacitor C1 is low, the voltage of the capacitor C8 is low.
ZD1 is in the reverse blocking state, and transistor Q2 maintains the off state. For this reason, a gate voltage is applied to the gate of the field effect transistor Q3, bypassing the resistor R11, increasing the base amount of the transistor Q4 and increasing the capacity of the capacitor.
By charging C13 and applying a gate voltage to the field effect transistor Q5, the apparent resistance between the source and the drain of the field effect transistor Q5 is reduced. Therefore, the capacitor C14 is connected in parallel to the capacitor C7, the combined capacitance increases, the base amount of the transistor Q1 increases, and the oscillation frequency decreases, so that the output of the inverter circuit 3 increases.

As described above, by increasing the output of the inverter circuit 3, the voltage of the second capacitor C2 approaches 0 V at the time of zero crossing of the commercial AC power supply e.
As shown in FIG. 2A, an input current is supplied from the commercial AC power supply e side, and the second capacitor C2 also resonates as shown in FIG. As shown, since the input current continues in a substantially sinusoidal manner, there is no pause section and harmonics can be reduced.

When the power is turned on, the emitter and collector currents of the transistor Q4 do not flow because the capacitor C11 is not charged, so that the field effect transistor Q5 is kept off and the output of the inverter circuit 3 increases. No, it can be soft-started.

When the voltage of the capacitor C12 increases due to a surge or the like, the potential of the base of the transistor Q4 is increased, the base current of the transistor Q4 is stopped, and the field effect transistor Q5 is turned off without charging the capacitor C13. To prevent the output of the inverter circuit 3 from increasing.

Next, another embodiment will be described with reference to FIG.

The embodiment shown in FIG. 3 is different from the embodiment shown in FIG. 1 in that the second capacitor C2 is replaced by a diode.
It is connected in parallel to D1.

In such a configuration, the basic operation is as shown in FIG.
Operates similarly to the embodiment shown in FIG.

[0040]

According to the power supply device of the first aspect, the inverter circuit supplies the input current from the first capacitor and the second capacitor when the output level of the rectifier is equal to or higher than the charging level of the charging capacitor. When the output level of the rectifier is lower than the charge level of the charging capacitor, an input current is supplied from the partial smoothing circuit, and the parallel resonance circuit is resonated by the switching operation of the switching element to reduce harmonics. When the input voltage detected in the step is low, the output of the inverter circuit is increased by the control means, the potential of the second capacitor is made lower than the input voltage, and the input current flows to the load.
Even when the input voltage is low, harmonics included in the input current can be reduced.

According to the power supply device of the second aspect, the inverter circuit includes the first capacitor and the second capacitor when the output level of the rectifier is equal to or higher than the charging level of the charging capacitor.
When the output level of the rectifier is lower than the charge level of the charging capacitor, the input current is supplied from the partial smoothing circuit, and the switching operation of the switching element causes the parallel resonance circuit to resonate to perform a harmonic operation. And when the input voltage detected by the input voltage detection means is low, the output of the inverter circuit is increased by the control means, the potential of the second capacitor is made lower than the input voltage, and the input current flows to the load. Thus, even when the input voltage is low, harmonics included in the input current can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a power supply device of the present invention.

FIG. 2 is a waveform chart showing the same operation.

FIG. 3 is a circuit diagram showing an operation of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Full-wave rectification circuit as rectification means 2 Partial smoothing circuit 3 Inverter circuit 4 Parallel resonance circuit 6 Input voltage detection circuit as input voltage detection means 7 Control circuit as control means C1 First capacitor C2 Second capacitor C3 Charging Capacitor C4 Resonant capacitor D1 Diode e Commercial AC power supply L1 Inductor L2 Inductor Q1 Transistor Tr1 as switching element Inverter transformer as resonant inductor

Claims (2)

[Claims] 1. A rectifier for rectifying an alternating current from an AC power supply, a first capacitor connected in parallel to an output terminal of the rectifier, and one end of the first capacitor connected in series with a forward polarity. A second capacitor connected in parallel to the first capacitor via the diode, an inductor and a charging capacitor, wherein the charging capacitor has a maximum instantaneous voltage value of the output of the rectifier means. A partial smoothing circuit connected in parallel to the second capacitor charged at a lower voltage, a parallel resonance circuit having a resonance capacitor and a resonance inductor, and a switching element connected in series to the parallel resonance circuit. An inverter connected in parallel to the partial smoothing circuit and generating a high-frequency voltage by the switching operation of the switching element A circuit; input voltage detection means for detecting an input voltage input to the first capacitor; and control means for increasing the output of the inverter circuit when the input voltage detected by the input voltage detection means is low. A power supply device comprising: A first capacitor connected to the AC power supply; a rectifier connected to the first capacitor; a second capacitor connected to the rectifier; an inductor and a charging capacitor; A partial smoothing circuit connected in parallel to the second capacitor for charging the charging capacitor with a voltage lower than the maximum instantaneous voltage value of the output of the rectifier, and a parallel resonance circuit having a resonance capacitor and a resonance inductor. A circuit, an inverter circuit having a switching element connected in series to the parallel resonance circuit, connected in parallel to the partial smoothing circuit, and generating a high-frequency voltage by a switching operation of the switching element; Input voltage detecting means for detecting an input voltage input to the capacitor; and an input voltage detected by the input voltage detecting means. Control means for increasing the output of the inverter circuit when the pressure is low.