JP3412354B2 - Power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[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.
By connecting in series with a capacitance element C6 and a switching element SW2 connected in parallel to both ends of the discharge lamp La and a control unit CN for controlling the switching element SW2, a light load such as filament preheating of the discharge lamp La can be achieved. , 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
Supply to. 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, the above-mentioned conventional example has the following problems.

In the above-mentioned conventional example, since the impedance element Z exists even if the switching element SW2 is controlled, the voltage Vc1 across the smoothing capacitance element C1 rises, albeit little by little, by turning on / off the switching elements Q1 and Q2. This is for example the impedance element Z
Becomes more prominent by including an inductance element. That is, the energy accumulated in the inductance element gradually moves to the capacitance element C1 due to the 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 including a capacitance element and a diode for smoothing an AC power source to obtain a DC power output via the full-wave rectifier and the high-frequency backflow suppressing unit, and at least one switching element and an oscillating circuit. An inverter circuit which has a DC power output of the smoothing circuit and supplies it to a load by converting it to AC high frequency power, and a 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. At the same time, a state in which a current is drawn from the AC power supply according to the polarity of the high frequency power to be returned and a state in which the smoothing circuit is charged via the full wave rectifier and the high frequency backflow suppression unit The at the power supply and a high frequency feedback section are alternately repeated, when the load is a light load, characterized in that a feedback stop for stopping the feedback of the high-frequency power by the high frequency feedback section.

According to the second aspect of the present invention, the feedback stop unit stops the feedback of the high frequency power when the output voltage of the smoothing circuit exceeds a specified value.

According to the third aspect of the present invention, the feedback stop section includes a switching element inserted in the feedback path of the high frequency power in the high frequency feedback section, and the high frequency is controlled by controlling the switching element. It is characterized by stopping the return of electric power.

According to the fourth aspect of the present invention, the feedback stop section is configured to include a series circuit of the impedance element and the switching element inserted in the feedback path of the high frequency power in the high frequency feedback section, and the switching is performed. It is characterized in that the feedback of high frequency power is stopped by controlling the element.

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

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

According to the invention described in claim 7, the load is a discharge lamp.

[0018]

[Embodiment]

(Embodiment 1) FIG. 1 shows a block diagram of the 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 as a high-frequency backflow suppressing unit for blocking reverse flow of high frequency to the AC power supply Vs side, and a DC output of the full-wave rectifier DB1. A smoothing circuit including a smoothing circuit H connected between terminals through a diode Do and smoothing the AC power supply Vs to obtain a DC power output, and at least one switching element Qo1, an oscillating circuit, and an antiparallel diode of the switching element Qo1. An inverter circuit INVo that is connected to both ends of H and that converts the DC power output of the smoothing circuit H into AC high frequency power and supplies it to the discharge lamp La that is a load, an impedance element Zo, and a switching element SWo that is a feedback stop unit. And a part of the high frequency power output from the inverter circuit INVo is connected to the full wave rectifier DB1. A high-frequency feedback in which a state in which a current is absorbed from the AC power supply Vs and a state in which the smoothing circuit H is charged via the full-wave rectifier DB1 and the diode Do is alternately repeated while being fed back between the diodes Do according to the polarity of the fed-back high-frequency power. The part FB and the discharge lamp La connected to the output end of the inverter circuit INVo.

In this embodiment, the switching element SWo is turned off when the load is light, and the AC power source Vs → full-wave rectifier DB1 → impedance element Zo → switching element S.
Wo → part of the vibration circuit → switching element Qo → full-wave rectifier DB1 → interrupts the current flowing through the path of the AC power supply Vs. By operating in this way, when the load is light,
Since a current flows into the smoothing circuit H only from the AC power supply Vs via the diode Do, the output voltage of the smoothing circuit H does not rise above the peak value of the AC power supply Vs.

(Second Embodiment) FIG. 2 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 components that are the same as those in the circuit shown in FIG.

Next, a more specific circuit of the circuit diagram shown in FIG. 2 is shown in FIG. In this circuit, in the circuit of FIG. 2, the impedance element Zo is composed of an inductance element L11 and a capacitance element C11 connected in series, and the switching element SWo is a full-wave circuit having an input terminal connected between the capacitance element C11 and the capacitance element C13. Rectifier DB2
And a switching element Qo3 connected to the output terminal of the full-wave rectifier DB2, and the smoothing circuit H includes a diode D
It is composed of a 1/2 partial smoothing circuit composed of 14 to D16 and capacitance elements C14 and C15, and a capacitance element C16 connected to both ends thereof. The inverter element Y has a secondary winding n2, and the primary winding n1 is connected to the cathode terminal of the diode Do and the capacitance element C1.
Transformer T1 connected between the three and the inductance element L1 connected to both ends of the secondary winding n2 of the transformer T1.
2, a capacitance element C12, and a series-parallel connection of the discharge lamp La. The capacitance element C16 has a smaller capacity 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 turning on the switching element Qo3.

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. 3 along the path from the switching element Qo2 to the capacitance element C16. Thereafter, by turning off the switching elements Qo1 and Qo2, the current I1 flows in the direction of the arrow shown in FIG. 3 in 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 the direction opposite to the direction of the arrow shown in FIG. 3 through the path of the next winding n1 → the switching element Qo1 → the capacitance element C13. After that, the switching element Qo
By turning off the 1, Qo2, 1 winding n1 → the capacitance elements of the transformer T1 C16 → diode D 1
2 → Capacitance element C13 → Current I1 flows through the path of the primary winding n1 of the transformer T1 in the direction opposite to the direction of the arrow shown in FIG. 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. Switching element Qo1 off, Qo
2 By turning on, AC power supply Vs → filter circuit F
1 → Full wave rectifier DB1 → Inductance element L11 → Capacitance element C11 → Full wave rectifier DB2 → Switching element Qo3 → Full wave rectifier DB2 → Capacitance element C13 → Switching element Qo2 → Full wave rectifier DB1
→ The filter circuit F1 → The current I2 flows in the direction of the arrow shown in FIG. 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 → the full wave rectifier DB2 → the switching element Qo3 → the full wave rectifier DB.
2 → capacitance element C13 → diode D11 → capacitance element C16 → full-wave rectifier DB1 → filter circuit F1 → AC power supply Vs, and a current I2 flows in the direction of the arrow shown in FIG.
To charge. By switching the switching element Qo1 on and Qo2 off, the capacitance element C11 → inductance element L11 → diode Do → switching element Qo1 → capacitance element C13 → full-wave rectifier DB2.
→ Switching element Qo3 → Full-wave rectifier DB2 → Capacitance element C11, the current I2 flows in the opposite direction of the arrow shown in FIG. After that, switching element Q
By turning off o1 and Qo2, capacitance element C11 → inductance element L11 → diode Do
→ Capacitance element C16 → Diode D12 → Capacitance element C13 → Full wave rectifier DB2 → Switching element Qo3 → Full wave rectifier DB2 → Capacitance element C11 The current I2 flows in the direction opposite to the direction of the arrow shown in FIG. 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 source 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. In the input distortion improving operation described above, the switching element Qo
Since the charging loop of the smoothing circuit H exists when 1 and Qo2 are off, the charging loop of the smoothing circuit H is cut off by turning off the switching element Qo3 in this case. Then, the inverter circuit IN is added to the output power of the full-wave rectifier DB1.
Since the high frequency power fed back from Vo is not superimposed, the voltage Vc1 across the capacitance element C16
6 never becomes higher than the peak value of the output voltage VDB1 of the full-wave rectifier DB1, and the capacitance element C1
It is possible to suppress the step-up of the voltage Vc16 between both ends of 6, that is, the step-up of the output voltage of the smoothing circuit H.

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

The difference from the second embodiment shown in FIG. 2 is that the anode terminal of the diode Do is connected to the inverter element Y.
Is connected to one end of the diode Do, the cathode terminal of the diode Do is connected to the collector terminal of the switching element Qo1, and the capacitance element C17 is connected in parallel with the diode Do. Description is omitted by attaching the same reference numerals.

FIG. 5 shows a more specific circuit of the circuit diagram shown in FIG. The difference between this circuit and the circuit diagram of the second embodiment shown in FIG. 3 is that the anode terminal of the diode Do is connected to one end of the inverter element Y and the cathode terminal of the diode Do is connected to the switching element Qo1 as described above. This is because the capacitance element C17 is connected in parallel to the diode Do and the diode Do, and the same configurations as those of the other second embodiment are denoted by the same reference numerals and the description thereof will be omitted.

With this configuration, even if the switching element Qo3 is turned off under a light load, the AC power supply V
s → filter circuit F1 → full-wave rectifier DB1 → transformer T
1 primary winding n1 → capacitance element C13 → switching element Qo2 → full wave rectifier DB1 → filter circuit F
Since the input current Iin can flow in the path of 1 → AC power supply Vs, the input distortion can be further improved.

[0033]

According to the inventions of claims 1 to 6, in the case of a light load, the boosting of the output voltage of the smoothing circuit can be suppressed and the input distortion can be improved. Can be provided.

According to the invention described in claim 7, 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. The 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 is a circuit diagram showing a second embodiment according to the present invention.

FIG. 3 shows a specific circuit diagram in the above embodiment.

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

FIG. 5 shows a specific circuit diagram in the above embodiment.

FIG. 6 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 unit 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 (7)

(57) [Claims] 1. A full-wave rectifier for full-wave rectifying an AC power supply,
A high-frequency backflow suppressing unit that blocks a high-frequency backflow to the AC power supply side, and a capacitance element and a diode that smooth the AC power supply to obtain a DC power output via the full-wave rectifier and the high-frequency suppressing unit. An inverter circuit that has a smoothing circuit, at least one switching element and an oscillating circuit, and converts the DC power output of the smoothing circuit into AC high-frequency power and supplies it to a load; and a high-frequency power output from the inverter circuit. The part is fed back between the full-wave rectifier and the high-frequency backflow suppressing part,
A power supply including a high-frequency feedback unit that alternately repeats a state of drawing a current from the AC power supply according to the polarity of the high-frequency power 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 the apparatus, the the load is a light load, the power supply apparatus characterized in that a feedback stop for stopping the feedback of the high-frequency power by the high frequency feedback section. 2. The power supply device according to claim 1, wherein the feedback stop unit stops the feedback of the high frequency power when the output voltage of the smoothing circuit exceeds a specified value. 3. The feedback stop unit includes a switching element inserted in a high-frequency power feedback path of the high-frequency feedback unit, and stops the high-frequency power feedback by controlling the switching element. serial mounting of the power device to claim 1 or claim 2, characterized in that the. 4. The feedback stop unit is configured to include a series circuit of a switching element and a switching element inserted in a feedback path of the high frequency power in the high frequency feedback section, and controls the switching element. serial mounting of the power device to claim 1 or claim 2, characterized in that to stop the return of the high-frequency power through. 5. The power supply device according to claim 4, wherein the impedance element is configured to include at least a capacitance element. 6. The power supply device according to claim 4, wherein the impedance element is also used as the vibration circuit. 7. The power supply device according to claim 1, wherein the load is a discharge lamp.