JPH0970182A - Power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power unit which can suppress the rise of the output voltage of a smoothing circuit when the load is light and, at the same time, can improve input distortion. SOLUTION: A power unit is constituted of a full-wave rectifier DB1, a high-frequency reverse-current suppressing circuit Do, a smoothing circuit H which obtains a DC power output by smoothing AC power supply Vs, an inverter circuit INVo which converts the DC power output of the circuit H into high-frequency AC power and supplies the AC power to a discharge lamp La, and a high-frequency feedback section FB which is composed of an impedance element Zo, feeds back part of the AC power, and alternately repeats a state where the section FB suck an electric current from the AC power supply Vs and another state where the section FB discharges the smoothing circuit H in accordance with the polarity of the fed back high-frequency AC power. When the load is light, the power unit adjusts the quantity of the electric current flowing to the impedance element Zo by intermittently oscillating the inverter circuit INVo so as to suppress the value of the both-terminal voltage Vdc of the circuit H within a specific range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply.

[0002]

2. Description of the Related Art As a conventional example of the present invention, there is one disclosed in Japanese Patent Application No. 6-190816 filed by the present applicant.
The circuit diagram is shown in FIG.

This circuit is connected in series between a full-wave rectifier DB1 for full-wave rectifying the AC power supply Vs and an output terminal of the full-wave rectifier DB1 via a diode D3, and a switching element Q1 for alternately turning on and off. , Q2 and switching elements Q1, Q2 are connected in parallel at both ends of a series circuit, and the smoothing capacitance element C1 is charged when the switching element Q2 is turned on.
2, a step-down chopper circuit composed of diodes D4, D5 and an inductance element L3, and a switching element Q
An inverter element Y including a capacitance element C5 connected in parallel at both ends of a series circuit of Q1 and Q2, an inductance element L1, capacitance elements C3, C10 connected in parallel at both ends of a switching element Q2, and a discharge lamp La.
And the positive output terminal of full-wave rectifier DB1 and diode D5
And a capacitance element C4 connected to the connection point of the inductance element L3 and a capacitance element C4.
The series connection of the capacitance element C6 and the switching element SW2 connected in parallel at both ends of the control unit CN and the control unit CN for controlling the switching element SW2 allows the discharge lamp La to have a light load such as when the filament is preheated. , The voltage V across the smoothing capacitance element C1
It is possible to suppress the abnormal rise of c1 and improve the input distortion.

An inverter circuit INV is constituted by the switching elements Q1, Q2 and the inverter element Y, and by alternately turning on / off the switching elements Q1, Q2, the voltage Vc1 across the smoothing capacitance element C1 is changed to the inductance element L1, the capacitance element C3. , C
10 resonant system converts into AC high frequency voltage and discharge lamp La
To supply. The capacitance element C10 is connected in parallel between the non-power supply side terminals of the discharge lamp La. The capacitance element C4 and the capacitance element C6 form an impedance element Z, and the high frequency feedback section FB is formed via the impedance element Z.

In the steady state, the switching element SW2 is turned off, and a part of the high frequency voltage output from the step-down chopper circuit is fed back via the capacitance element C4.
The input current Iin flows from the AC power supply Vs according to the polarity of the voltage across the capacitance element C4, and thus the input distortion is improved.

When the load is light, the control unit CN turns on the switching element SW2 to control the impedance value of the impedance element Z, thereby controlling the feedback voltage from the step-down chopper circuit, and smoothing capacitance element C1. The abnormal increase of the voltage Vc1 between both ends is suppressed and the input distortion is improved in substantially the same manner as in the steady state.

By providing a filter circuit in this circuit, the input current Iin has a substantially sinusoidal waveform with less harmonic components.

[0008]

However, in the above-mentioned conventional example, in order to control the feedback voltage from the step-down chopper circuit,
The first problem arises in that the switching element SW2, the control unit CN, the impedance element, or the like are required, which leads to an increase in the size of the device.

Further, the following second problem also occurs. Since the impedance element Z exists even if the switching element SW2 is controlled, the switching elements Q1 and Q2
The voltage Vc1 across the smoothing capacitance element C1 rises, though slightly, by turning on and off. This becomes more remarkable when the impedance element Z is configured to include an inductance element, for example. That is, the energy accumulated in the inductance element gradually moves to the smoothing capacitance element C1 by a so-called chopper operation, which causes the voltage Vc1 across the smoothing capacitance element C1 to rise.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a light load.
An object of the present invention is to provide a power supply device capable of suppressing boosting of the output voltage of the smoothing circuit and improving input distortion.

[0011]

In order to solve the above problems, according to the invention of claim 1, a full-wave rectifier for full-wave rectifying an AC power supply and a backflow of high frequency to the AC power supply side are blocked. A high-frequency backflow suppressing unit, a smoothing circuit for smoothing an AC power source to obtain a DC power output via a full-wave rectifier and a high-frequency backflow suppressing unit, and a DC power output of a smoothing circuit having at least two switching elements and an oscillating circuit. Inverter circuit that converts the high frequency power into alternating current high frequency power and supplies it to the load, and part of the high frequency power output from the inverter circuit is fed back between the full wave rectifier and the high frequency backflow suppressing unit, and A high-frequency feedback unit that alternately repeats a state of drawing a current from an AC power supply and a state of charging a smoothing circuit via a full-wave rectifier and a high-frequency backflow suppressing unit, and two switches. At a power supply device and a control unit for controlling the switching element, when the load is a light load, 2
It is characterized in that a pause period is provided in which two switching elements are stopped for a certain period.

According to the second aspect of the invention, the control section includes:
When the load becomes light, the two switching elements are controlled so as to reduce the feedback of the high frequency power by the high frequency feedback section.

According to the third aspect of the present invention, the control section includes:
When the load becomes light, the two switching elements are stopped for a certain period so as to reduce the feedback of the high frequency power by the high frequency feedback section.

According to a fourth aspect of the invention, the control section comprises:
When the load becomes light, the two switching elements are stopped in the vicinity of the peaks of the AC power supply for a certain period so that the feedback of the high frequency power by the high frequency feedback unit is reduced.

According to a fifth aspect of the invention, the control section comprises:
It is characterized in that the two switching elements are controlled so that the output voltage of the smoothing circuit is detected and the change of the output voltage of the smoothing circuit is controlled within a certain range.

According to a sixth aspect of the invention, the control section comprises:
The present invention is characterized in that two switching elements are controlled so that the load state is detected and the change of the output voltage of the smoothing circuit is controlled within a certain range.

According to the seventh aspect of the invention, the control section comprises:
It is characterized in that the two switching elements are controlled so as to detect the AC power supply voltage and control the change of the output voltage of the smoothing circuit within a certain range.

According to the invention described in claim 8, the high-frequency feedback section is configured to include an impedance element inserted in a feedback path of the high-frequency power.

According to a ninth aspect of the invention, the impedance element includes at least a capacitance element.

According to the tenth aspect of the invention, the impedance element is also used as the vibration circuit.

According to the eleventh aspect of the present invention, the load is a discharge lamp.

[0022]

[Embodiment]

(Embodiment 1) FIG. 1 shows a block diagram of a first embodiment according to the present invention.

This configuration has a full-wave rectifier DB1 for full-wave rectifying the AC power supply Vs, a diode Do which is a high-frequency backflow suppressing unit for blocking a high-frequency backflow to the AC power supply Vs side, and a DC output of the full-wave rectifier DB1. A smoothing circuit H connected between terminals through a diode Do and smoothing an AC power supply Vs to obtain a DC power output; and at least a switching element Qo1, Qo2, a vibration circuit, a switching element Qo1,
An inverter circuit INVo, which is composed of an anti-parallel diode of Qo2, is connected to both ends of the smoothing circuit H, and converts the DC power output of the smoothing circuit H into AC high-frequency power and supplies it to the discharge lamp La, which is a load, and an impedance element Zo. And a part of the high frequency power output from the inverter circuit INVo is fed back to the full wave rectifier DB1 and the diode Do, and a current is absorbed from the AC power source Vs according to the polarity of the high frequency power to be fed back and a full wave rectifier. A high frequency feedback section FB which alternately repeats a state of charging the smoothing circuit H via DB1 and a diode Do, and an inverter circuit I
The discharge lamp La is connected to the output end of NVo.

In the block diagram shown in FIG. 1, the control unit 1 is used for the entire cycle of the AC power source Vs as shown in FIG.
By alternately repeating switching on and off of the switching elements Qo1 and Qo2 by 0, the alternating-current power supply Vs → full-wave rectifier DB1 → impedance element Zo → part of the oscillating circuit → at least one of the switching elements Qo1 and Qo2 → full-wave rectifier DB1. → A current flows in the path of the AC power supply Vs, and this current causes the smoothing circuit H as shown in FIG. 2 (c).
The voltage Vdc at both ends of the voltage rises. This is particularly noticeable when the load is light. 2A shows the output voltage V1 of the full-wave rectifier DB1, FIG. 2B shows the drive signal VGS of the switching element Qo1 or the switching element Qo2, and FIG.
(C) shows the voltage Vdc across the smoothing circuit H.

Therefore, in the present embodiment, it is assumed that the input power and the load power are substantially equal even when the load is light.
As shown in FIG. 3C, in order to suppress the value of the voltage Vdc across the smoothing circuit H within a predetermined range, as shown in FIG. 3B, a pause period in which the switching elements Qo1 and Qo2 are paused for a time t1 is set. Provided. That is, the switching element Qo for the time t2 near the valley of the output voltage V1 of the full-wave rectifier DB1.
The switching operation of 1 and Qo2 (hereinafter referred to as intermittent oscillation) is performed to adjust the amount of current flowing through the impedance element Zo.

At time t1, the switching element Qo
Since impedance 1 and Qo2 are off, impedance element Z
The current flowing through o is cut off, and the power supply to the discharge lamp La is also cut off. Therefore, the means shown in the present embodiment is particularly effective when the discharge lamp La is in a spot state, for example, when the filament is preheated.

By operating in this way, the output voltage of the smoothing circuit does not rise above the peak value of the AC power supply Vs when the load is light.

(Second Embodiment) FIG. 4 shows a circuit diagram of a second embodiment according to the present invention.

This circuit is the same as the circuit shown in FIG.
s and the full-wave rectifier DB1 between the inductance element LF,
Filter circuit F composed of capacitance element CF
1 is inserted, and the switching element Q is connected in parallel to the output terminal of the full-wave rectifier DB1 via the diode Do.
o1 and Qo2 connected in series and the switching element Qo1,
Diodes D11 and D connected in antiparallel to each of Qo2
An inverter circuit INVo is composed of 12 and a series connection including an inverter element Y and a capacitance element C13 connected between the cathode terminal of the diode Do and the connection points of the switching elements Qo1 and Qo2.
The other configurations that are the same as those of the circuit shown in FIG.

The impedance element Z is composed of an inductance element L11 and a capacitance element C11 connected in series, and the smoothing circuit H is composed of diodes D14 to D1.
6, consisting of capacitance elements C14 and C15
It is composed of a partial smoothing circuit and a capacitance element C16 connected to both ends thereof. The inverter element Y has a secondary winding n2 and a primary winding n1 connected to a diode Do.
The transformer T1 connected between the cathode terminal and the capacitance element C13 and the inductance element L12, the capacitance element C12, and the discharge lamp La connected in series at both ends of the secondary winding n2 of the transformer T1. Further, the control unit 10 that detects the output voltage Vdc of the smoothing circuit H, that is, the voltage across the capacitance element C6 and drives the switching elements Qo1 and Qo2 is provided.
The control unit 10 alternately turns on and off the switching elements Qo1 and Qo2. The capacitance element C16
Has a smaller capacitance than the capacitance elements C14 and C15.

In the steady state in which the discharge lamp La is stably lit, this circuit performs the inverter operation and the input distortion improvement by uniformly switching the switching elements Qo1 and Qo2.

First, the operation of the inverter in the steady state will be described. Switching element Qo1 off, Qo2
By turning on, the capacitance element C16 → the primary winding n1 of the transformer T1 → the capacitance element C13 →
The current I1 flows in the direction of the arrow shown in FIG. 4 along the path from the switching element Qo2 to the capacitance element C16. Then, by turning off the switching elements Qo1 and Qo2, the current I1 flows in the direction of the arrow shown in FIG. 4 along the path of the primary winding n1 of the transformer T1 → capacitance element C13 → diode D11 → primary winding n1 of the transformer T1. Flows. By turning on the switching element Qo1 and turning off Qo2, the capacitance element C13 → 1 of the transformer T1
A current I1 flows in a direction opposite to the direction of the arrow shown in FIG. 4 along the path of the next winding n1 → the switching element Qo1 → the capacitance element C13. After that, the switching element Qo
1 and Qo2 are turned off, so that the primary winding n1 of the transformer T1 → capacitance element C16 → diode D1
A current I1 flows in the direction opposite to the direction of the arrow shown in FIG. 4 in the path of 2 → capacitance element C13 → the primary winding n1 of the transformer T1. A secondary voltage is generated in the secondary winding n2 of the transformer T1 by the current I1 thus flowing, and the resonance system (= oscillation circuit) including the secondary winding n2 of the transformer T1, the inductance element L12, and the capacitance element C12.
AC high-frequency voltage is supplied to the discharge lamp La via. Since the capacitance element C16 is connected in parallel to the 1/2 partial smoothing circuit, the capacitance element C16 is actually
Power is supplied from at least one of 14 to C16 to the inverter circuit INVo, and the current I1 flows. Since the capacitance element C16 has a smaller capacity than the capacitance elements C14 and C15, the capacitance element C16 will be mainly described here.

Next, the operation of improving the input distortion in the steady state will be described. By turning the switching element Qo1 off and the switching element Qo2 on, the AC power supply Vs
→ Filter circuit F1 → Full wave rectifier DB1 → Inductance element L11 → Capacitance element C11 → Capacitance element C13 → Switching element Qo2 → Full wave rectifier DB1 → Filter circuit F1 → AC power supply Vs in the direction of the arrow shown in FIG. The current I2 flows. After that, by switching off the switching elements Qo1 and Qo2, the AC power supply Vs → the filter circuit F1 → the full-wave rectifier DB1 → the inductance element L11 → the capacitance element C11 →
Capacitance element C13 → diode D11 → capacitance element C16 → full-wave rectifier DB1 → filter circuit F1 → AC power supply Vs, and current I2 flows in the direction of the arrow shown in FIG. By turning on the switching element Qo1 and turning off the switching element Qo2, the capacitance element C1
A current I2 flows in the route of 1 → inductance element L11 → diode Do → switching element Qo1 → capacitance element C13 → capacitance element C11, which is opposite to the direction of the arrow shown in FIG. Thereafter, by turning off the switching elements Qo1 and Qo2, the capacitance element C11 → the inductance element L11 → the diode D
In the path of o → capacitance element C16 → diode D12 → capacitance element C13 → capacitance element C11, the current I2 flows in the direction opposite to the direction of the arrow shown in FIG. 4 and the capacitance element C16 is charged.

That is, a part of the high frequency power output from the inverter circuit INVo is fed back between the full-wave rectifier DB1 and the diode Do, and a current is absorbed from the AC power supply Vs according to the polarity of the high frequency power to be fed back. Smoothing circuit H via full-wave rectifier DB1 and diode Do
Alternating with the state of charging the AC power source Vs
The input current Iin can be made to continue to flow in substantially the entire area of, and the input distortion is improved.

In the light load state, the operation is as follows. As shown in FIG. 2B, the control unit 10 uniformly repeats the alternating on and off of the switching elements Qo1 and Qo2, whereby the AC power supply Vs → the filter circuit F1 → the full-wave rectifier DB1 → the inductance element L11 → the capacitance element. C11 → capacitance element C13 → diode D
11 → Capacitance element C16 → Full wave rectifier DB1 →
A current I2 flows through the path from the filter circuit F1 to the AC power supply Vs, and the voltage Vc16 across the capacitance element C16 starts rising due to this current I2. Capacitance element C
When the voltage Vc16 across 16 exceeds a certain value, the control unit 1
0 detects this, and as shown in FIG. 3B, intermittently oscillates the switching elements Q11 and Q12 to reduce the current I2 and suppresses the rise of the voltage Vc16 across the capacitance element C16. By this operation, the capacitance element C1
The voltage Vc16 across the capacitor 6 decreases, but when the voltage Vc16 across the capacitance element C16 becomes equal to or lower than a certain value, the control unit 10 detects it and the control unit 10 switches as shown in FIG. 2B. Elements Qo1 and Qo2
By alternately repeating ON and OFF, the voltage Vc16 across the capacitance element C16 starts to rise again.

By repeating the above operation, even if the discharge lamp La is momentarily attached or detached, the change in the voltage Vc16 across the capacitance element C16, that is, the change in the output voltage Vdc of the smoothing circuit H is kept within a certain range. Adjustments can be made within the time, and it is possible to quickly shift to the lighting state. Also,
For example, even when a light load state such as filament preheating occurs, the voltage Vc16 across the capacitance element C16 can be adjusted within a certain range.

(Third Embodiment) FIG. 5 shows a circuit diagram of a third embodiment according to the present invention.

The difference from the second embodiment shown in FIG. 4 is that the control section 10 does not detect the output voltage Vdc of the smoothing circuit H, but instead uses a transformer D1 via a diode D17.
The secondary winding n3 is configured to detect the secondary voltage, and the same configurations as those of the second embodiment are denoted by the same reference numerals and the description thereof will be omitted.

As described above, by detecting the load state directly from the transformer T1, it is possible to detect an abnormal state such as an emilys of the discharge lamp La. In this case, a rapid intermittent oscillation occurs. Can be migrated.

(Embodiment 4) FIG. 6 shows a circuit diagram of a fourth embodiment according to the present invention.

The difference from the second embodiment shown in FIG. 4 is that the control unit 10 is configured to detect the AC power supply Vs instead of detecting the output voltage Vdc of the smoothing circuit H. The same components as those of the second embodiment are denoted by the same reference numerals and the description thereof will be omitted.

In this embodiment, when the AC power supply Vs exceeds a certain value at a light load, the switching element Qo1,
The oscillation of Qo2 is stopped, and when the AC power supply Vs falls below a certain value, intermittent oscillation is performed so that the oscillations of the switching elements Qo1 and Qo2 are restarted, and the rise of the output voltage Vdc of the smoothing circuit H is suppressed.

In this embodiment, the output voltage Vdc of the smoothing circuit H as shown in the second and third embodiments is used.
Also, since there is no configuration for detecting the state of the load, it is particularly effective when it is known beforehand that the load is light, for example, at the time of starting and preheating the discharge lamp La.

[0044]

It is an object of the present invention to provide a power supply device capable of suppressing the boosting of the output voltage of the smoothing circuit and improving the input distortion in the case of a light load.

According to the inventions of claims 1 to 4 and claims 8 to 10, in the case of a light load,
A power supply device that can suppress boosting of the output voltage of the smoothing circuit and can improve input distortion can be provided.

According to the fifth aspect of the present invention, for example, even when the discharge lamp is momentarily attached and detached, the change in the output voltage of the smoothing circuit can be adjusted within a certain range, and in the case of a light load. It is possible to provide a power supply device that can suppress boosting of the output voltage of the smoothing circuit and can improve input distortion.

According to the sixth aspect of the present invention, it is possible to detect an abnormal state such as an emily of a discharge lamp and quickly shift to intermittent oscillation, and in the case of a light load,
A power supply device capable of suppressing boosting of the output voltage of the smoothing circuit and improving input distortion can be provided.

According to the seventh aspect of the invention, when it is known that the load is light in advance, for example, when the discharge lamp is preheated, it is possible to suppress the boosting of the output voltage of the smoothing circuit and improve the input distortion. It is possible to provide a possible power supply device.

According to the eleventh aspect of the present invention, the discharge lamp can be stably lit, the boosting of the output voltage of the smoothing circuit can be suppressed in the case of a light load, and the input distortion can be improved. A power supply device can be provided.

[Brief description of drawings]

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

FIG. 2 shows an operation waveform diagram in a steady state according to the above embodiment.

FIG. 3 shows an operation waveform diagram in a light load state according to the above embodiment.

FIG. 4 is a circuit diagram showing a second embodiment according to the present invention.

FIG. 5 is a circuit diagram showing a third embodiment according to the present invention.

FIG. 6 is a circuit diagram showing a fourth embodiment according to the present invention.

FIG. 7 is a circuit diagram showing a conventional example according to the present invention.

[Explanation of symbols]

 C Capacitance element DB Full wave rectifier Do High frequency backflow suppression section FB High frequency feedback section H Smoothing circuit INV Inverter circuit Vs AC power supply La Discharge lamp Q Switching element SW Switching element Zo Impedance element

Claims (11)

[Claims] A full-wave rectifier for full-wave rectifying an AC power supply;
At least two high-frequency backflow suppressing units that prevent high-frequency backflow to the AC power supply side; a smoothing circuit that smoothes the AC power supply to obtain a DC power output via the full-wave rectifier and the high-frequency backflow suppressing unit; An inverter circuit that has a switching element and an oscillating circuit, converts the DC power output of the smoothing circuit into AC high-frequency power and supplies it to a load, and a part of the high-frequency power output from the inverter circuit to the full-wave rectifier and A state of feeding back current between the high-frequency backflow suppressing units, a state of absorbing a current from the AC power supply according to the polarity of the high-frequency backflow to be fed back, and a state of charging the smoothing circuit via the full-wave rectifier and the high-frequency backflow suppressing unit. In a power supply device including a high-frequency feedback section that alternately repeats and a control section that controls the two switching elements, the load is light. A power supply device is provided with a rest period for stopping the two switching elements for a certain period when a load is applied. 2. The control unit controls the two switching elements so as to reduce the feedback of high frequency power by the high frequency feedback unit when the load becomes light. The power supply device according to item 1. 3. The control unit stops the two switching elements for a certain period of time so as to reduce the feedback of the high frequency power by the high frequency feedback unit when the load becomes a light load. Claim 1 or Claim 2
The power supply device according to. 4. The control unit controls the two switching elements so as to reduce feedback of high frequency power by the high frequency feedback unit when the load becomes light, for a certain period of time in the vicinity of the peak of the AC power supply. The power supply device according to claim 1, wherein the power supply device is stopped. 5. The control unit detects the output voltage of the smoothing circuit and controls the two switching elements so as to control the change of the output voltage of the smoothing circuit within a certain range. Claims 1 to 4 characterized in that
The power supply device according to any one of the above. 6. The control unit detects the state of the load and controls the two switching elements so as to control the change of the output voltage of the smoothing circuit within a certain range. The power supply device according to any one of claims 1 to 4, which is characterized. 7. The control unit controls the two switching elements so as to detect the AC power supply voltage and control a change in an output voltage of the smoothing circuit within a certain range. The power supply device according to any one of claims 1 to 4, which is characterized. 8. The power supply device according to claim 1, wherein the high-frequency feedback unit includes an impedance element inserted in a feedback path of high-frequency power. . 9. The power supply device according to claim 8, wherein the impedance element includes at least a capacitance element. 10. The power supply device according to claim 8, wherein the impedance element is also used as the vibration circuit. 11. The power supply device according to claim 1, wherein the load is a discharge lamp.