JP2000270556A - Power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power unit which can start the supply of high-frequency power to load immediately after power, even through it is equipped with a partial smoothing circuit. SOLUTION: A current flowing to the primary winding of the drive transformer CT1 for driving transformers Q1 and Q2 is inverted by the resonance action of a resonance circuit including an inductor L1 and a capacitor C2, and both transistors Q1 and Q2 are turned on and off alternately by self-excited oscillation. The transistor Q2 constitutes a boosting chopper circuit together with a smoothing capacitor C1, an inductor L2, and a diode D3. The primary winding of the driving transformer CT is inserted into a course, which lets a charge current flow into the smoothing capacitor C1 when transistor Q2 is turned on. When the power is made, the transistor Q2 is turned on, and at this time the charge current of the smoothing capacitor C1 flows into the primary winding of the driving transformer CT, so that turning on and off of the transistors Q1 and Q2 are started without waiting for the voltage rise of the smoothing capacitor C1.

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 for converting a low-frequency AC power supply such as a commercial power supply into a DC power, converting the power into a high-frequency power by an inverter, and supplying the converted power to a load.

[0002]

2. Description of the Related Art A circuit shown in FIG. 6 has been proposed as this type of power supply device. The illustrated example is a circuit in which an AC power supply such as a commercial power supply is used as a power supply and a discharge lamp such as a fluorescent lamp is turned on at a high frequency.

That is, in the circuit shown in FIG. 6, a smoothing capacitor C1 is connected between the output terminals of a rectifier DB for full-wave rectifying an AC power supply Vac, and two transistors Q1 and Q2 are connected between both ends of the smoothing capacitor C1. A series circuit of a collector and an emitter and a series circuit of two capacitors C3 and C4 are connected respectively. Each transistor Q1, Q
Diodes D1 and D2 are connected in anti-parallel between the collector and the emitter of No. 2, respectively. Here, the anti-parallel means that the diode D has a polarity between the collector and the emitter of each of the transistors Q1 and Q2 in which the current flows in a direction opposite to the direction in which the current flows when the transistors Q1 and Q2 are turned on.
1 and D2. Each transistor Q
1 and Q2 function as switching elements together with the diodes D1 and D2, respectively. Both transistors Q1, Q
2 is connected between the connection point of the capacitors C3 and C4, a series circuit of the primary winding of the drive transformer CT, the inductor L1, and the capacitor C2 is connected.
Is connected between both ends of the load Z.

The driving transformer CT has two secondary windings, one of which is connected between the base and the emitter of the transistor Q1 via a base current adjusting resistor R1. The secondary winding is connected between the base and the emitter of the transistor Q2 via a resistor R2 for adjusting a base current. The secondary winding connected to the transistor Q1 applies an on-direction bias to the transistor Q1 when the leftward current in FIG. 6 passes through the primary winding, and the secondary winding connected to the transistor Q2. 6 applies an on-direction bias to the transistor Q2 when the rightward current in FIG. 6 passes through the primary winding.

In the above configuration, when the power is turned on, the smoothing capacitor C1 and the capacitors C3 and C4 are charged,
When the transistor Q2 starts conducting, the capacitor C4-
Parallel circuit of load Z and capacitor C2-inductor L1
A current flows through the path of the primary winding of the driving transformer CT, the transistor Q2, and the capacitor C4. At this time, the driving transformer CT applies an on-direction bias to the transistor Q2 and keeps the transistor Q1 off, so that the transistor Q2 is completely turned on. Thereafter, the direction of the current flowing through the primary winding of the drive transformer CT is inverted by the resonance action of the resonance circuit including the inductor L1 and the capacitor C2, so that the transistor Q2 is turned off, and the transistor Q1 is biased in the on direction. Can be When the transistor Q1 starts to conduct, a capacitor C3-transistor Q1-primary winding of the driving transformer CT-inductor L1-
Parallel circuit of load Z and capacitor C2-capacitor C3
A current flows through the path, and the transistor Q1 is completely turned on. Thereafter, the direction of the current flowing through the primary winding of the drive transformer CT is again inverted by the resonance action of the resonance circuit, the transistor Q1 is turned off, and the conduction of the transistor Q2 is started.

By repeating the above operation, a high-frequency alternating current according to the resonance frequency of the resonance circuit flows through the load Z. That is, the above-described circuit configuration forms an inverter circuit that generates high-frequency power by self-excited oscillation. This inverter circuit has a resonance circuit (including an inductor L1, a capacitor C2, and the like as constituent elements).
And a series circuit of a primary winding of a driving transformer CT and a transistor Q2, is driven in a self-excited manner by using an output of a secondary winding of the driving transformer CT, and supplies high frequency power to a load Z. . In this configuration, the capacitors C3 and C3
C4 functions as a coupling capacitor to remove a DC component.

In the circuit configuration shown in FIG. 6, since the smoothing capacitor C1 is connected between the output terminals of the rectifier DB, a current flows through the rectifier DB only near the peak of the voltage of the AC power supply Vac. It is known that the input current from the AC power supply Vac has many idle periods and the input current distortion increases. Therefore, as shown in FIG. 7, by adopting a configuration in which the voltage between both ends of the smoothing capacitor C1 is reduced, it is considered to reduce the idle period of the input current from the AC power supply Vac and suppress the input current distortion. . Further, in this configuration, the voltage applied to the circuit components such as the transistors Q1 and Q2 is also lower than that of the circuit configuration shown in FIG. 6, so that the breakdown voltage of the circuit components may be lower than that of the circuit configuration shown in FIG. And cost can be reduced accordingly.

In the circuit shown in FIG. 7, instead of the smoothing capacitor C1 in the circuit configuration of FIG. 6, an inductor L2 as an inductance element and a discharging diode (hereinafter abbreviated as a diode) D4 are provided on the negative electrode side of the smoothing capacitor C1.
Is provided, and a connection point between the inductor L2 and the diode D4 is connected to a charging diode (hereinafter, referred to as a charging diode).
Both transistors Q are connected via D3.
1 and Q2. The diode D3 has a polarity that allows a charging current to flow through the capacitor C1 (that is, the anode is connected to the connection point between the inductor L2 and the diode D4).
The polarity is such that a discharge current of 1 flows (that is, the cathode is connected to the connection point between the inductor L2 and the anode of the diode D3). Further, in the circuit shown in FIG. 7, the capacitor C4 in the circuit configuration of FIG. 6 is omitted, and the capacitor Cf is connected in parallel to a series circuit of the smoothing capacitor C1, the inductor L2, and the diode D4. This type of circuit is called a partial smoothing circuit.

That is, when the transistor Q2 is turned on, the rectifier DB-smoothing capacitor C1-inductor L2
When a current flows through the path of the diode D3-transistor Q2-rectifier DB and the transistor Q2 is turned off, the energy stored in the inductor L2 is reduced by the diode D3-
The light is emitted through a path from the diode D1 to the smoothing capacitor C1. In this configuration, the charging current for charging the smoothing capacitor C1 from the rectifier DB is the inductor L2
And the transistor Q2, the smoothing capacitor C
The voltage across the terminal 1 is reduced according to the ratio between the ON period and the OFF period of the transistor Q2. That is, the diode D
1, D3, inductor L2, transistor Q2 and smoothing capacitor C1 constitute a step-down chopper circuit.

In the circuit shown in FIG. 7, when the transistor Q1 is turned on, the capacitor C3, the transistor Q1, the primary winding of the driving transformer CT, the inductor L1, the parallel circuit of the load Z and the capacitor C2, and the current flowing through the path of the capacitor C3. The operation at this time is the same as the circuit configuration shown in FIG. On the other hand, when the transistor Q2 is conducting, if the output voltage of the rectifier DB is higher than the voltage across the smoothing capacitor C1, the rectifier DB-the capacitor C3-the parallel circuit of the load Z and the capacitor C2-the inductor L1-
A current flows through a path between the primary winding of the driving transformer CT, the transistor Q2, and the rectifier DB. At this time, at the same time, current also flows through the path of the rectifier DB-smoothing capacitor C1-inductor L2-diode D3-transistor Q2-rectifier DB. That is, the input current flows from the AC power supply Vac to the rectifier DB during this period. If the transistor Q2 is conducting and the output voltage of the rectifier DB is lower than the voltage across the smoothing capacitor C1, the smoothing capacitor C1-the capacitor C3-the load Z and the capacitor C
A current flows through a path of a parallel circuit with the inductor 2, the inductor L1, the primary winding of the driving transformer CT, the transistor Q2, the diode D4, the inductor L2, and the smoothing capacitor C1, and energy is supplied to the load Z by discharging the smoothing capacitor C1. You.

The capacitor Cf is charged immediately after the power is turned on until the voltage between both ends reaches the peak value of the output voltage of the rectifier DB. Thereafter, when the transistor Q2 is turned on, the capacitor Cf-smoothing capacitor C1-inductor L2-diode D3 Charging the smoothing capacitor C1 via the path of the transistor Q2 to the capacitor Cf; The capacitor C
f also has a function of forming a path for releasing the energy stored in the inductor L1 and the like when the transistor Q1 is turned off from on. That is, the transistor Q
When 1 is turned off from on, a current path of inductor L1-parallel circuit of load Z and capacitor C2-capacitor C3-capacitor Cf-diode D2-primary winding of drive transformer CT-inductor L1 is formed.

[0012]

By the way, in the circuit configuration shown in FIG. 7, immediately after the power is turned on, the capacitor Cf is charged until the voltage between both ends reaches the peak value of the output voltage of the rectifier DB. When conducting, the smoothing capacitor C1 is charged through the path of the capacitor Cf-smoothing capacitor C1-inductor L2-diode D3-transistor Q2-capacitor Cf. Immediately after the power is turned on, the voltage across the smoothing capacitor C1 is lower than the output voltage of the rectifier DB for most of the period of one cycle of the voltage waveform of the AC power supply Vac.
2 conducts, and the voltage across the capacitor Cf becomes lower than the output voltage of the rectifier DB, a current flows from the rectifier DB to two paths, a path passing through the primary winding of the drive transformer CT and a path passing through the smoothing capacitor C1. Become like However, immediately after the power is turned on, since the smoothing capacitor C1 is not charged, a current mainly flows through the path passing through the smoothing capacitor C1 among the two paths, and almost no current flows through the primary winding of the drive transformer CT. Not flowing. That is, the transistors Q1 and Q2 cannot be turned on / off until the voltage across the capacitor C1 sufficiently rises, and self-excited oscillation cannot be started. In other words, there is a problem that the operation of the load Z cannot be started immediately even when the power is turned on.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power supply device which has a partial smoothing circuit and can start supplying high-frequency power to a load immediately after power-on. Is to do.

[0014]

According to a first aspect of the present invention, there is provided a rectifier for rectifying an AC power supply, a series circuit of a smoothing capacitor, an inductance element, a charging diode, and a switching element, and a series circuit of the smoothing capacitor and the discharging diode. A step-down chopper circuit including a series circuit and inserted between the output terminals of the rectifier; a series circuit including a resonance circuit having a resonance frequency higher than a frequency of an AC power supply, the switching element, and a primary winding of a drive transformer. A self-excited inverter circuit that supplies high frequency power to a load circuit by turning on and off the switching element using an output of a secondary winding of a drive transformer using the rectifier or the smoothing capacitor as a power supply, and turning on the switching element by turning on the power. And a starting circuit for turning on the switching element. In which the drive transformer primary winding is inserted in the path for flowing the DENDEN flow. According to this configuration, when the switching element is turned on by the starting circuit immediately after the power is turned on, the charging current flows through the uncharged smoothing capacitor, and this charging current passes through the primary winding of the driving transformer. A relatively large current can flow through the transformer, and the switching element can be turned on / off without waiting for the voltage of the smoothing capacitor to rise.

According to a second aspect of the present invention, in the first aspect of the present invention, an impedance element to which a high-frequency voltage generated in the inverter circuit is applied is provided in a charging path of the smoothing capacitor, and a voltage across the impedance element is reduced by the rectifier. And applied to the smoothing capacitor. According to this configuration, the charging current flows through the smoothing capacitor by adding the high-frequency voltage generated by the inverter circuit to the output voltage of the rectifier even during the period when the output voltage of the rectifier is lower than the voltage across the smoothing capacitor. Therefore, the input current from the AC power supply to the rectifier has almost no pause, thereby suppressing input current distortion and obtaining a high input power factor.

According to a third aspect of the present invention, in the first or second aspect of the present invention, a primary winding of the drive transformer is provided between the switching element and a series circuit of the smoothing capacitor and the charging diode. It is what is inserted.
With such a connection relationship, the positional relationship between the switching element and the smoothing capacitor, which are also used as the step-down chopper circuit and the inverter circuit, is symmetrical with respect to the drive transformer, so that the circuit design is facilitated.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the load circuit has an output transformer comprising a leakage transformer, and a leakage inductance of the output transformer is used as a component of the resonance circuit. It is. According to this configuration, since the output transformer is used as a component of the resonance circuit, if the configuration uses the output transformer, it is not necessary to separately provide a resonance inductor, and the number of components can be reduced. is there.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, a smoothing capacitor is connected between one end of the charging diode and a rectifier, and between the other end of the charging diode and the switching element. A series circuit of a primary winding of the output transformer and a primary winding of the drive transformer is inserted, and a leakage inductance of the output transformer is used as the inductance element. According to this configuration, since the output transformer is used as an inductance element in the step-down chopper circuit, if the output transformer is used, there is no need to separately provide an inductance element for the step-down chopper, and a resonance inductor is also provided. Since there is no need, the number of parts is reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) As shown in FIG. 1, this embodiment has a circuit configuration basically similar to the conventional configuration shown in FIG. The cathode of the diode D3 used for the partial smoothing circuit is not directly connected to the collector of the transistor Q2, but is connected between the primary winding of the driving transformer CT and the inductor L1.

This will be described more specifically. In the circuit shown in FIG. 1, a capacitor Cf is connected between the output terminals of a rectifier DB composed of a diode bridge for full-wave rectification of an AC power supply Vac, and the collectors of two transistors Q1 and Q2 are connected between both ends of the capacitor Cf.・ A series circuit of emitters is connected. Further, a series circuit in which the cathode of the diode D4 is connected to the negative electrode of the smoothing capacitor C1 via the inductor L2 is also connected between both ends of the capacitor Cf. Diodes D1 and D2 are connected in anti-parallel between collectors and emitters of the transistors Q1 and Q2, respectively. A series circuit of a primary winding of the driving transformer CT, an inductor L1, a capacitor C2, and a capacitor C3 is connected between a connection point of the two transistors Q1 and Q2 and a positive electrode of the rectifier DB. That is, both transistors Q1, Q2
Is connected to one end of the primary winding of the drive transformer CT, and the positive terminal of the rectifier DB is connected to one end of the capacitor C3, which is connected to the other end of the primary winding of the drive transformer CT. The inductor L1 and the capacitor C2 connected to the other end of the capacitor C3 are connected in series. A load Z is connected in parallel to the capacitor C2. The capacitor C2 constitutes a resonance circuit together with the inductor L1 and the like, and the capacitor C3 is a coupling capacitor for removing a DC component to the load Z.
It has a sufficiently large capacity. Further, the above-mentioned capacitor Cf is provided for passing an AC component.

The drive transformer CT has two secondary windings, one of which is connected between the base and the emitter of the transistor Q1 via a base current adjusting resistor R1. The secondary winding is connected between the base and the emitter of the transistor Q2 via a resistor R2 for adjusting a base current. The secondary winding connected to the transistor Q1 applies an on-direction bias to the transistor Q1 when the leftward current of FIG. 1 passes through the primary winding, and the transistor Q2
Is applied to the transistor Q2 in an on-direction when the rightward current of FIG. 1 passes through the primary winding.

An anode of a diode D3 is connected to a connection point between the inductor L2 and the diode D4 which constitute a partial smoothing circuit. The present embodiment is characterized in that the connection position of the cathode of the diode D3 is a connection point between the primary winding of the drive transformer CT and the inductor L1. The operation by adopting this configuration will be described later.

Further, a series circuit of the resistor R3 and the capacitor C5 is connected to the capacitor Cf such that one end of the resistor R3 is connected to the positive electrode of the rectifier DB. The resistance R
A trigger element Q3 such as a diac is inserted between the connection point of the capacitor 3 and the capacitor C5 and the base of the transistor Q2. Resistor R3, capacitor C5 and trigger element Q3
Constitutes a start-up circuit. When the capacitor C5 is charged via the resistor R3 and the terminal voltage of the capacitor C5 reaches the breakover voltage of the trigger element Q3, the trigger element Q3 turns on and the transistor Q2 turns on. It is configured to be. After the transistor Q2 is turned on, a diode D5 is connected between the connection point between the resistor R3 and the capacitor C5 and the connection point between the two transistors Q1 and Q2 in order to discharge the capacitor C5 and turn off the trigger element Q3. Is inserted. That is, as described later, in the steady state, the transistors Q1 and Q2 are alternately turned on and off at a high frequency. When the transistor Q2 is turned on, the charge of the capacitor C5 is released through the diode D5, and the terminal voltage of the capacitor C5 is changed to the break of the trigger element Q3. Keep it below the overvoltage. To enable this operation, the terminal voltage of the capacitor C5 must be
The time to reach the breakover voltage of 3 is set to be longer than the ON / OFF cycle of the transistors Q1 and Q2.

When the power is turned on, the voltage across the capacitor Cf is charged up to the peak value of the output voltage of the rectifier DB, and at the same time, the capacitor C5 is charged via the resistor R3, whereby the transistor is turned on as described above. Q2
Turns on. When the transistor Q2 is turned on, first, the capacitor Cf-the smoothing capacitor C1-the inductor L2
A current flows through the path of the diode D3, the primary winding of the driving transformer CT, the transistor Q2, and the capacitor Cf.
When the capacitor Cf discharges and the voltage across the capacitor Cf becomes lower than the output voltage of the rectifier DB, the rectifier DB-
Smoothing capacitor C1-Inductor L2-Diode D3
-The primary winding of the driving transformer CT-the path of the transistor Q2-the rectifier DB and the rectifier DB-the capacitor C3-a parallel circuit of the load Z and the capacitor C2-the inductor L1-the path of the driving transformer CT-the transistor Q2-the rectifier DB. Current flows through the two paths.

As described above, in the configuration of the present embodiment, since the primary winding of the drive transformer CT is inserted in the charging path of the smoothing capacitor C1, the smoothing capacitor C1 is inserted.
Thus, a sufficient current can flow through the primary winding of the drive transformer CT even immediately after the power is turned on, and the transistor Q2 can be given a bias in the ON direction with a sufficient magnitude.

After that, when the direction of the current flowing through the primary winding of the drive coil CT is reversed by the resonance action of the resonance circuit including the capacitor C2 and the inductor L1, the transistor is similar to the conventional configuration shown in FIG. Q2 is turned off, and the energy stored in the inductor L2 is transferred to the diode D3-the primary winding of the driving transformer CT-the diode D2.
1- Discharged on the path of the smoothing capacitor C1. here,
Since the charging current for charging the smoothing capacitor C1 from the rectifier DB passes through the inductor L2 and the transistor Q2, the voltage across the smoothing capacitor C1 is
Is lower than the output voltage of the rectifier DB in accordance with the ratio between the ON period and the OFF period of the rectifier DB. That is, the diodes D1 and D3, the inductor L2, the transistor Q2, and the smoothing capacitor C1 constitute a step-down chopper circuit.

When the transistor Q1 is turned on when the transistor Q2 is turned off, the capacitor C3-transistor Q1-primary winding of the driving transformer CT-inductor L1-
Parallel circuit of load Z and capacitor C2-capacitor C3
The current flows through the path. Thereafter, the direction of the current flowing through the primary winding of the drive coil CT is reversed by the resonance action of the resonance circuit including the capacitor C2 and the inductor L1,
When the transistor Q1 is turned off, the stored energy of the inductor L1 and the like is stored in a parallel circuit of the inductor L1−the load Z and the capacitor C2−the capacitor C3−the capacitor Cf.
-Diode D2-Drive transformer CT-Inductor L1
It is released by the route. Further, the transistor Q2 is turned on again with the turning off of the transistor Q1, and the above operation is repeated.

During the period when the output voltage of the rectifier DB is lower than the voltage across the smoothing capacitor C1, when the transistor Q2 is turned on, the smoothing capacitor C1-capacitor C3-parallel circuit of the load Z and the capacitor C2.
A current flows through the path of the inductor L1-the primary winding of the driving transformer CT-the transistor Q2-the diode D4-the inductor L2-the smoothing capacitor C1.
, Energy is supplied to the load Z. When the voltage across the smoothing capacitor C1 increases, the charging current of the smoothing capacitor C1 decreases, so that the current flowing through the inductor L2 and the diode D3 to the primary winding of the drive transformer CT decreases, and the rectifier DB-capacitor C3
-Parallel circuit of load Z and capacitor C2-Inductor L
1-drive transformer CT-transistor Q2-rectifier DB
The current flowing through the drive transformer CT increases along the path.

Thereafter, the same operation as in the conventional configuration shown in FIG. 7 is performed, self-excited oscillation is stably performed so that both transistors Q1 and Q2 are alternately turned on and off, and high frequency power is supplied to load Z. .

As described above, the charging current of the smoothing capacitor C1 immediately after the power is turned on is caused to flow through the primary winding of the driving transformer CT.
1, a sufficient bias can be applied to Q2, and self-sustained pulsation can be stably performed immediately after the power is turned on, so that high-frequency power can be supplied to the load Z.

(Second Embodiment) This embodiment is different from FIG.
As shown in FIG. 7, the partial smoothing circuit is configured to charge the smoothing capacitor C1 when the transistor Q1 is turned on, and the transistor Q1 is turned on immediately after the power is turned on.

That is, in the partial smoothing circuit of the present embodiment, the smoothing capacitor C1 is connected to the negative electrode of the rectifier DB via the inductor L2, the cathode of the diode D4 is connected to the positive electrode of the rectifier DB, and the anode of the diode D4 is connected to the anode. A diode D3 is connected to the connection point with the smoothing capacitor C1.
Are connected. The anode of diode D3 is connected to the connection point between inductor L1 and the primary winding of drive transformer CT.

In this embodiment, the transistor Q2
A resistor R4 is connected between the emitter and the collector of the transistor Q1, and a series circuit of a resistor R3 and a capacitor C5 is connected between the emitter and the collector of the transistor Q1. One end of the trigger element Q3 and the anode of the diode D3 are connected to a connection point between the resistor R3 and the capacitor C5, and the other end of the trigger element 3 is connected to the base of the transistor Q1,
The cathode of diode D3 is connected to the collector of transistor Q1.

When the power is turned on, the voltage across the capacitor Cf is charged to the peak value of the output voltage of the rectifier DB, and at the same time, the capacitor Cf is passed through the resistors R3 and R4.
5 is charged, when the voltage across the capacitor C5 reaches the breakover voltage of the trigger element Q3, the trigger element Q3 conducts and the transistor Q1 turns on. When the transistor Q1 is turned on, first, a current flows through a path of the capacitor Cf, the transistor Q1, the primary winding of the driving transformer CT, the diode D3, the smoothing capacitor C1, the inductor L2, and the capacitor Cf. Thereafter, as in the first embodiment, both transistors Q
1, Q2 are turned on and off alternately.

When the transistor Q1 is on, the rectifier D
B-transistor Q1-primary winding of drive transformer CT-
Diode D3-Smoothing capacitor C1-Inductor L2
-The path of the rectifier DB and the capacitor C3-the transistor Q1-the primary winding of the driving transformer CT-the inductor L1-
Parallel circuit of load Z and capacitor C2-capacitor C3
Current flows through this path, charging the smoothing capacitor C1 and supplying high-frequency power to the load Z. When the smoothing capacitor C1 is charged in this manner, the charging current flowing through the smoothing capacitor C1 in a path passing through the diode D3 and the inductor L2 decreases with an increase in the voltage between both ends of the smoothing capacitor C1. The current flowing through the next winding is a current mainly due to the resonance action of the resonance circuit including the capacitor C2 and the inductor L1. Thus, both transistors Q1 and Q2 can be stably turned on and off.

The capacitor C3, a parallel circuit of the capacitor C2 and the load Z, the inductor L1, the drive transformer C
Although the series circuit composed of the primary winding of T is connected in parallel to the transistor Q1 in the above-described embodiment, it can be connected in parallel to the transistor Q2, and can be connected in parallel to the transistor Q1. Operate.

(Third Embodiment) This embodiment is similar to FIG.
As shown in FIG. 1, in the first embodiment, a discharge lamp La such as a fluorescent lamp is used
3 has one end connected to the negative electrode instead of the positive electrode of the rectifier DB. Further, a MOSFET is used instead of using the transistors Q1 and Q2 in which the diodes D1 and D2 are connected in anti-parallel. In the following, a MOSFET replaced with a parallel circuit of transistors Q1, Q2 and diodes D1, D2 is referred to as a switching element Q
1 and Q2. Here, since the MOSFET has a parasitic diode, the diodes D1 and D2 are unnecessary. Furthermore, in the present embodiment, the discharge lamp La is connected to the secondary side of the output transformer T1 in which the primary winding is connected between the inductor L1 and the capacitor C3, and the non-power supply end of the filament in the discharge lamp La. The capacitor C2 is connected therebetween. In addition to these configurations, in the present embodiment, the source of the switching element Q2 and the rectifier DB
A capacitor Cin is connected between the capacitor Cin and the negative electrode, and a diode D6 is connected in parallel to the capacitor Cin. The cathode of the diode D6 is connected to the negative electrode of the rectifier DB.

The present embodiment operates in substantially the same manner as the first embodiment during the period when the output voltage of the rectifier DB is higher than the voltage across the smoothing capacitor C1. When the power is turned on, the switching element Q2 is turned on as in the other embodiments described above. When the switching element Q2 is turned on, first, the capacitor Cf-the smoothing capacitor C1-
A current flows through a path of the inductor L2, the diode D3, the primary winding of the driving transformer CT, the switching element Q2, and the capacitor Cf. When the capacitor Cf discharges and the voltage across the capacitor Cf becomes lower than the output voltage of the rectifier DB, the rectifier DB-the smoothing capacitor C1-the inductor L
2-Diode D3-Primary winding of drive transformer CT-Switching element Q2-Diode D6-Rectifier DB path and rectifier DB-Smoothing capacitor C1-Inductor L
2-diode D3-inductor L1-output transformer T
A current flows through the primary winding of No. 1 and the path of the capacitor C3 and the rectifier DB. As described above, by supplying the charging current of the smoothing capacitor C1 to the primary winding of the driving transformer CT, it is possible to apply a sufficient ON-direction bias to the switching element Q2. After that, the inductor L
Self-excited oscillation is performed so that the direction of the current flowing through the primary winding of the drive coil CT is alternately reversed by the resonance action of the resonance circuit including the capacitor 1 and the capacitor C2, and the switching elements Q1 and Q2 are alternately turned on and off.

By the way, the output voltage of the rectifier DB is equal to the smoothing capacitor Cin and the diode D6.
1 even during a period lower than the voltage across the AC power supply Vac.
To allow a current to flow through the rectifier DB. That is, if the capacitor Cin and the diode D6 are not provided, the rectifier D
During the period in which the output voltage b is lower, the input current from the AC power supply Vac to the rectifier DB stops, and the envelope of the input current waveform does not become sinusoidal, so that the input current distortion increases and the power factor increases. Will decrease. On the other hand, when the capacitor Cin is provided, this capacitor Ci
By utilizing the charge and discharge of n, it is possible to flow a current from the AC power supply Vac to the rectifier DB even during a period in which the output voltage of the rectifier DB is lower than the voltage across the smoothing capacitor C1. This operation will be briefly described.

During the period when the output voltage of the rectifier DB is lower than the voltage across the smoothing capacitor C1, when the switching element Q1 is turned on, the smoothing capacitor C1-the switching element Q1-the primary winding of the driving transformer CT-the inductor L1- Primary winding of output transformer T1-capacitor C
3-capacitor Cin-diode D4-inductor L
2. A current flows through the path of the smoothing capacitor C1. That is, the capacitor Cin is charged. When the voltage across the capacitor Cin reaches the voltage difference between the voltage and the output voltage of the rectifier DB at both ends of the smoothing capacitor C1, a current flows from the AC power supply Vac to the rectifier DB, and the rectifier DB-switching element Q1-drives A current flows through the path of the primary winding of the transformer CT, the inductor L1, the primary winding of the output transformer T1, the capacitor C3, and the rectifier DB. That is, compared with the case where the capacitor C6 is not provided, the period in which the current flows from the AC power supply Vac to the rectifier DB can be increased, and as a result, the input current distortion can be reduced and the input power factor can be increased. become.

In other words, since the high frequency voltage generated in the inverter circuit is applied to both ends of the capacitor Cin as an impedance element, the output voltage of the rectifier DB is smoothed by superimposing the high frequency voltage on the output voltage of the rectifier DB. The smoothing capacitor C1 can be charged even during a period lower than the voltage across the capacitor C1. Other configurations and operations are the same as those of the first embodiment.

(Fourth Embodiment) This embodiment is different from FIG.
As shown in FIG. 5, the inductor L1 is omitted from the third embodiment shown in FIG. 3, and a leakage transformer is used as the drive transformer T1. In this configuration, the leakage inductance of the drive transformer T1 is
Since it functions as 1, it operates in the same manner as the configuration of the third embodiment. Other configurations and operations are the same as those of the third embodiment.

(Fifth Embodiment) This embodiment is different from FIG.
As shown in the figure, the inductor L2 is omitted from the fourth embodiment, and the cathode of the diode D3 is connected to the connection point between the capacitor C3 and the primary winding of the drive transformer T. In short, not only the resonance inductor L1 but also the inductor L2 for realizing the operation as the step-down chopper circuit is replaced by the leakage inductor of the output transformer T. In short, when switching element Q2 is on, rectifier DB-smoothing capacitor C1-diode D3-primary winding of output transformer T-primary winding of driving transformer cT-switching element Q2-diode D
6-charging the smoothing capacitor C1 in the path of the rectifier DB
At this time, the energy stored in the leakage inductance of the output transformer T is converted into the output transformer T-the primary winding of the drive transformer CT-the parasitic diode of the switching element Q1-the smoothing capacitor C1-the diode D3- when the switching element Q2 is turned off. It is released by the trans-T route.

In this embodiment, when the switching element Q2 is turned on immediately after the power is turned on, the rectifier DB
-Smoothing capacitor C1-Diode D3-Primary winding of output transformer T-Primary winding of drive transformer CT-Switching element Q2-Diode D6-Current flows through the path of rectifier DB. In addition, the charging current of the smoothing capacitor C1 is supplied to the primary winding of the driving transformer CT to surely turn on the switching element Q2, and self-excited oscillation can be stably performed immediately after the power is turned on. Other configurations and operations are the same as those of the fourth embodiment.

The start-up circuit is not limited to the above-described configuration, but may be any other configuration as long as the transistor Q2 (or the switching element Q2) inserted in the charging path of the smoothing capacitor C1 is turned on immediately after the power is turned on. Alternatively, any configuration of the starting circuit may be used.

[0046]

According to the first aspect of the present invention, a rectifier includes a rectifier for rectifying an AC power supply, a series circuit of a smoothing capacitor, an inductance element, a charging diode, and a switching element, and a series circuit of a smoothing capacitor and a discharging diode. A step-down chopper circuit inserted between the output terminals of the power supply, a series circuit of a resonance circuit having a resonance frequency higher than the frequency of the AC power supply, a switching element, and a primary winding of a drive transformer, and a rectifier or a smoothing capacitor as a power supply. A switching element comprising: a self-excited inverter circuit that supplies high-frequency power to a load circuit by turning on and off a switching element using an output of a secondary winding of a driving transformer; and a starting circuit that turns on the switching element when power is turned on. The primary winding of the drive transformer is in the path where the charging current flows to the smoothing capacitor when the When the switching element is turned on by the starting circuit immediately after the power is turned on, the charging current flows through the uncharged smoothing capacitor, and this charging current passes through the primary winding of the drive transformer. This has the advantage that a relatively large current can be passed through the drive transformer, and the switching element can be turned on / off without waiting for the voltage of the smoothing capacitor to rise.

According to a second aspect of the present invention, in the first aspect of the present invention, an impedance element to which a high-frequency voltage generated in the inverter circuit is applied is provided in a charging path of the smoothing capacitor, and a voltage across the impedance element is output from the rectifier. The high-frequency voltage generated by the inverter circuit is added to the output voltage of the rectifier and smoothed even during the period when the output voltage of the rectifier is lower than the voltage across the smoothing capacitor. Since the charging current can flow through the capacitor, there is almost no pause in the input current from the AC power supply to the rectifier, so that there is an advantage that input current distortion can be suppressed and a high input power factor can be obtained.

According to a third aspect of the present invention, in the first or second aspect, a primary winding of a driving transformer is inserted between a switching element and a series circuit of a smoothing capacitor and a charging diode. With such a connection relationship, the positional relationship between the switching element and the smoothing capacitor, which are also used as the step-down chopper circuit and the inverter circuit, has symmetry with respect to the drive transformer.
There is an advantage that circuit design becomes easy.

According to a fourth aspect of the present invention, in the first to third aspects, the load circuit has an output transformer comprising a leakage transformer, and the leakage inductance of the output transformer is used as a component of the resonance circuit. Since the output transformer is used as a component of the resonance circuit, if the output transformer is used, it is not necessary to separately provide a resonance inductor, and the number of components may be reduced.

According to a fifth aspect of the present invention, in the fourth aspect, a smoothing capacitor is connected between one end of the charging diode and the rectifier, and the output transformer is connected between the other end of the charging diode and the switching element. Since a series circuit of the primary winding and the primary winding of the drive transformer is inserted, the leakage inductance of the output transformer is used as an inductance element, and the output transformer is used as an inductance element in a step-down chopper circuit.
With the configuration using the output transformer, there is no need to separately provide an inductance element for the step-down chopper, and there is no need to provide an inductor for resonance, so that there is an advantage that the number of components is reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

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

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention.

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

FIG. 6 is a circuit diagram showing a conventional example.

FIG. 7 is a circuit diagram showing another conventional example.

[Explanation of symbols]

 C1 smoothing capacitor C2 capacitor C5 capacitor Cin capacitor CT drive transformer D1, D2 diode D3 (for charging) diode D4 (for discharging) diode D5 diode D6 diode DB rectifier L1 inductor L2 inductor Q1, Q2 switching element Q3 trigger element R3 resistance T output Transformer Vac AC power supply

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H05B 41/24 H05B 41/24 L 41/282 41/29 C F-term (Reference) 3K072 AA02 BA03 BA05 BB03 BC01 BC03 CA11 CA16 CB02 DB03 DD04 GA01 GA03 GB12 GC02 HA05 HA10 5H006 AA02 BB00 CA01 CA02 CA07 CB01 DC02 GA01 5H007 AA02 BB03 CA01 CA02 CB03 CB12 CB22 CB25 CC32 DC02 GA01

Claims (5)

[Claims] 1. A rectifier for rectifying an AC power supply, a series circuit of a smoothing capacitor, an inductance element, a charging diode and a switching element, and a series circuit of the smoothing capacitor and a discharging diode, between output terminals of the rectifier. A drive transformer including a series circuit of an inserted step-down chopper circuit, a resonance circuit having a resonance frequency higher than the frequency of an AC power supply, the switching element, and a primary winding of a drive transformer, using the rectifier or the smoothing capacitor as a power supply. A self-excited inverter circuit that turns on and off the switching element using the output of the secondary winding to supply high-frequency power to a load circuit; and a starting circuit that turns on the switching element when power is turned on. When the element is turned on, the driving transistor is placed in a path for supplying a charging current to the smoothing capacitor. A power supply device, wherein a primary winding of an impedance is inserted. 2. An impedance element to which a high frequency voltage generated in the inverter circuit is applied is provided in a charging path of the smoothing capacitor, and a voltage across the impedance element is superimposed on an output voltage of the rectifier and applied to the smoothing capacitor. The power supply device according to claim 1, wherein 3. A primary winding of the driving transformer is inserted between the switching element and a series circuit of the smoothing capacitor and the charging diode. Power supply. 4. The power supply device according to claim 1, wherein the load circuit has an output transformer including a leakage transformer, and a leakage inductance of the output transformer is used as a component of the resonance circuit. 5. A smoothing capacitor is connected between one end of the charging diode and a rectifier, and a primary winding of the output transformer and a driving transformer between the other end of the charging diode and the switching element. The power supply device according to claim 4, wherein a series circuit with a primary winding is inserted, and a leakage inductance of the output transformer is used as the inductance element.