JPH0759355A - AC-AC converter - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the power supply harmonics of AC-AC converter and increase the input power factor. A smoothing capacitor C2 for smoothing the pulsating DC output voltage of a diode bridge DB that rectifies the voltage of a commercial AC power supply AC is a harmonic choke TH connected to the diode bridge DB side and a smoothing capacitor C2 having a first capacitor in the charging direction. It is connected in a series circuit with one diode D1.
In addition, the resonance capacitor C is provided on both ends of the smoothing capacitor C2.
5, the resonance circuit of the resonance choke TO and the main transistor Q1 of the switching element are connected. Further, the contact point of the harmonic choke TH and the first diode D1 is connected to the collector of the main transistor Q1 via a series circuit of the second diode D2 having the anode connected to this contact side, the discharge lamp FL, and the ballast choke TB. is doing. Further, an auxiliary choke TA is connected between the contact point of the first diode D1 and the smoothing capacitor C2 and the contact point of the second diode D2 and the discharge lamp FL.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC-AC converter, which is applied to, for example, a discharge lamp lighting device.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram of a conventional AC-AC converter having an active smoothing filter AF. In FIG. 8, the active smoothing filter AF is connected to the output terminal of the diode bridge DB that rectifies the voltage of the commercial AC power supply AC, the inverter IV is connected to the output terminal of this active smoothing filter AF, and the output terminal of this inverter IV. A load LD is connected to.

The active smoothing filter AF is composed of a transistor Q2 which switches at high frequency, a drive control circuit BC of this transistor Q2, a harmonic choke TH, a first diode D1 and a smoothing capacitor C2. In FIG. 8, by the smoothing action of the active smoothing filter AF, the inverter IV
The smoothed DC voltage is supplied to.

FIG. 9 is a block diagram of another conventional AC-AC converter using a capacitor input type smoothing circuit. In FIG. 9, the smoothing capacitor C2 and the inverter IV are connected to the output terminal of the diode bridge DB that rectifies the voltage of the commercial AC power supply AC, and the load LD is connected to the output terminal of the inverter IV. In FIG. 9, the smoothing action of the capacitor C2 supplies the inverter IV with a substantially completely smoothed DC voltage.

[0005]

The conventional AC-AC converter of FIG. 8 as described above can make the input current waveform almost sinusoidal, and therefore has a high power factor and few power source harmonics. On the other hand, active smoothing filter AF
There is a problem that the circuit configuration of the transistor Q2 and the drive control circuit BC is complicated, expensive, and large in loss.

On the other hand, the conventional AC-AC converter shown in FIG. 9 has the features that the circuit configuration is simple, the cost is low, and the loss of the switching element of the inverter can be designed to be small. Since it has a pulse-like waveform that flows only in the vicinity, the power factor is low and there are many problems with power source harmonics.

The present invention has been made in order to solve such a problem, and it is a circuit system which does not use the above-mentioned active smoothing filter, and the power factor of the conventional example shown in FIG. An object of the present invention is to obtain an AC-AC converter having a combination of a small number of features and a feature that the circuit configuration of the conventional example of FIG.

[0008]

According to a first aspect of the present invention, an AC-AC converter has a first capacitor connected to an output terminal of a rectifying circuit for rectifying a commercial AC power supply voltage, and also an output terminal of the rectifying circuit. A smoothing capacitor for smoothing the output voltage of this rectifier circuit is connected in series with a harmonic choke connected to the rectifier circuit side and a smoothing capacitor and a first diode in the charging direction.
Connect the resonance circuit and the switch element that turns on and off at high frequency, and connect the harmonic choke and the contact point of the first diode,
The switching element is connected through a series circuit of a second diode and a load circuit whose anode is connected to this contact side, and a contact between the first diode and the smoothing capacitor and a contact between the second diode and the load circuit. An auxiliary choke is connected between them.

An AC-AC converter according to a second aspect of the invention has a third capacitor connected in parallel with the auxiliary choke of the first aspect of the invention.

In the AC-AC converter according to the third aspect of the invention, a sixth capacitor is additionally connected between the contact of the second diode and the load circuit and the negative terminal of the rectifier circuit in the first aspect of the invention. It is a thing.

An AC-AC converter according to a fourth aspect of the invention is one in which a third diode is connected in parallel with the sixth capacitor of the third aspect.

An AC-AC converter according to a fifth aspect of the present invention uses a series circuit of a discharge lamp and a ballast choke as a load circuit including the inductance element of the first, second, third or fourth aspect. is there.

[0013]

In the first, third and fourth inventions,
A high frequency current having a low frequency component approximately proportional to the sine wave voltage of the power source is supplied from the commercial AC power source to the load circuit via the second diode or the auxiliary choke.

In the second aspect of the invention, a high frequency current having a low frequency component substantially proportional to the sine wave voltage of the power source is supplied from the commercial AC power source to the load circuit via the second diode, the auxiliary choke or the third capacitor. It

In the fifth invention, the first or second
Alternatively, the third or fourth invention is effectively applied to the discharge lamp lighting circuit.

[0016]

EXAMPLES Examples will be described with reference to the drawings. First Embodiment FIG. 1 is a circuit diagram of an AC-AC converter according to a first embodiment of the present invention. The load is composed of a series circuit of a discharge lamp FL, a parallel circuit of a starting capacitor C4 connected to both ends of the discharge lamp FL, and a ballast choke TB that limits the lamp current of the discharge lamp FL.

In FIG. 1, a first capacitor C1 is connected to the output terminal of a diode bridge DB for rectifying the voltage of the commercial AC power supply AC, and a smoothing capacitor for smoothing the DC output voltage of the pulsating current of the diode bridge DB. C2 is connected to the harmonic choke TH connected to the diode bridge DB side and the smoothing capacitor C2 in the series circuit of the first diode D1 in the charging direction.

Further, a series circuit of a resonance capacitor C5, a resonance circuit composed of a parallel circuit of a resonance choke TO, and a main transistor Q1 of a switching element which is turned on / off at a high frequency is connected to both ends of the smoothing capacitor C2. There is. Further, the contact point of the harmonic choke TH and the first diode D1 is connected to the collector of the main transistor Q1 via a series circuit of the second diode D2 having the anode connected to this contact side, the discharge lamp FL, and the ballast choke TB. is doing. Further, an auxiliary choke TA is connected between the contact point of the first diode D1 and the smoothing capacitor C2 and the contact point of the second diode D2 and the discharge lamp FL.

Next, the circuit operation of FIG. 1 will be described. The main transistor Q1 turns on and off at a high frequency of several tens KHz,
The high frequency current loop in each case is shown below.

First, when the commercial AC power supply AC is turned on, a high frequency current flows in the following loop. When the main transistor Q1 is on, loop 1 (ballast choke TB
→ main transistor Q1 → diode bridge DB → commercial AC power supply AC → diode bridge DB → harmonic choke TH → second diode D2 → parallel circuit of discharge lamp FL and starting capacitor C4 → ballast choke TB).

Or loop 2 (ballast choke TB
→ main transistor Q1 → diode bridge DB → commercial AC power supply AC → diode bridge DB → harmonic choke TH → first diode D1 → auxiliary choke TA → parallel circuit of discharge lamp FL and starting capacitor C4 → ballast choke TB).

Loop 3 (ballast choke TB → main transistor Q1 → smoothing capacitor C1 → auxiliary choke TA
→ Parallel circuit of discharge lamp FL and starting capacitor C4 → ballast choke TB).

A high frequency current flows through the loop 4 (resonance choke TO → main transistor Q1 → smoothing capacitor C2 → resonance choke TO).

On the other hand, when the main transistor Q1 is off,
Loop 5 (ballast choke TB → resonance capacitor C5
→ smoothing capacitor C2 → diode bridge DB → commercial AC power supply AC → diode bridge DB → harmonic choke TH → second diode D2 → parallel circuit of discharge lamp FL and starting capacitor C4 → ballast choke TB).

Alternatively, loop 6 (ballast choke TB
→ Resonant capacitor C5 → Smoothing capacitor C2 → Diode bridge DB → Commercial AC power supply AC → Diode bridge DB → Harmonic choke TH → First diode D1 → Auxiliary choke TA → Parallel circuit of discharge lamp FL and starting capacitor C4 → Ballast choke TB ).

Loop 7 (ballast choke TB ← → resonance capacitor C5 ← → auxiliary capacitor TA ← → parallel circuit of discharge lamp FL and starting capacitor C4 ← → ballast choke TB).

A high frequency current flows through the loop 8 (resonance choke TO → resonance capacitor C5 → resonance choke TO).

First, when the commercial AC power supply AC is turned on, a high frequency current flows in the above loop (however, in the parallel circuit of the discharge lamp FL and the starting capacitor C4, the current flows only in the starting capacitor C4), and the ballast choke TB. A resonance voltage is generated in the starting capacitor C4 due to the series resonance of the starting capacitor C4, and the discharge lamp FL is lit by the resonance voltage. Even when the discharge lamp FL is lit, high-frequency current flows through the same loop as above,
In the parallel circuit of the discharge lamp FL and the starting capacitor C4, since the impedance of the discharge lamp FL is low, a high frequency current mainly flows in the discharge lamp FL.

FIG. 2 shows high-frequency current and voltage waveforms at various points when the discharge lamp FL in FIG. 1 is turned on. In the figure, (a), (b) and (c) are high frequencies in the peak voltage phase, the intermediate voltage phase and the zero voltage phase of the pulsating voltage waveform V _C1 of the first capacitor C1 connected to the output of the diode bridge DB, respectively. The waveform is shown.

In the figure, I _Q1 is the collector current waveform of the main transistor Q1, V _Q1 is the collector-emitter voltage waveform of the main transistor Q1, I _TH is the current waveform of the harmonic choke TH, and I _D1 is the first diode. Current waveform of D1, I _D2
The current waveform of the second diode D2, I _TA auxiliary choke current waveform, the I _TB shows the current waveform of the ballast choke TB.

From the above, a high frequency current proportional to the voltage value of the harmonic choke TH over the entire phase of the pulsating current voltage waveform V _C1 of the first capacitor C1 is generated in the loop 1 or 2 and the loop 5 or loop 6. Flow in, especially loop 1
It can be seen that, in the loop 5, the current is supplied from the commercial AC power source AC in one direction by the rectifying action of the second diode D2.

Then, the high frequency component is passed by the first capacitor C1, and the input current waveform I ₁ of the AC-AC converter of FIG. ₁ is a sine which is substantially proportional to the voltage waveform V ₁ of the commercial AC power supply AC as shown in FIG. It has a wavy waveform.

Second Embodiment FIG. 4 is a circuit diagram of an AC-AC converter according to a second embodiment of the present invention. In FIG. 4, the third capacitor is connected in parallel with the auxiliary choke TA in FIG.

The circuit operation of FIG. 4 is almost the same as that of FIG. 1 except that two current loops are added because the third capacitor C3 is added. That is, when the main transistor Q1 is on, the loop 9 (ballast choke T
B → main transistor Q1 → diode bridge DB → commercial AC power supply AC → diode bridge DB → harmonic choke TH → first diode D1 → third capacitor C3 →
When the parallel circuit of the discharge lamp FL and the starting capacitor C4 → ballast choke TB), while the main transistor Q1 is off, the loop 10 (ballast choke TB → resonance capacitor C5 → smoothing capacitor C2 → diode bridge DB → commercial AC power supply AC → The diode bridge DB → the harmonic choke TH → the first diode D1 → the third capacitor C3 → the parallel circuit of the discharge lamp FL and the starting capacitor C4 → the ballast choke TB).

FIG. 5 shows high-frequency current and voltage waveforms at various points when the discharge lamp FL in FIG. 1 is turned on. In the figure, (a), (b) and (c) are high frequencies in the peak voltage phase, the intermediate voltage phase and the zero voltage phase of the pulsating voltage waveform V _C1 of the first capacitor C1 connected to the output of the diode bridge DB, respectively. The waveform is shown.

In the figure, I _Q1 is the collector current waveform of the main transistor Q1, V _Q1 is the collector-emitter voltage waveform of the main transistor Q1, I _TH is the current waveform of the harmonic choke TH, and I _D1 is the first diode. Current waveform of D1, I _D2
Shows the current waveform of the second diode D2, I _TA shows the current waveform of the auxiliary choke, I _C3 shows the current waveform of the third capacitor I _TB shows the current waveform of the ballast choke TB.

From the above, a high frequency current proportional to the voltage value of the harmonic choke TH over the entire phase of the pulsating current voltage waveform V _C1 of the first capacitor C1 is generated in the loop 1, loop 2 or loop 9 and loop 5. Alternatively, it flows in the loop 6 or the loop 10, and particularly in the loop 1 and the loop 5, the commercial AC power source A is generated by the rectifying action of the second diode D2.
It can be seen from C that current is supplied in one direction of the discharge lamp FL.

Then, the high frequency component is passed by the first capacitor C1, and the input current waveform I ₁ of the AC-AC converter of FIG. 4 is a sine which is substantially proportional to the voltage waveform V ₁ of the commercial AC power supply AC as shown in FIG. It has a wavy waveform.

FIG. 6 shows an AC according to the third embodiment of the present invention.
FIG. 3 is a circuit diagram of an AC converter. In FIG. 6, the sixth capacitor is connected between the contact of the second diode and the load circuit and the negative terminal of the rectifier circuit in FIG.

The circuit operation of FIG. 6 is almost the same as that of FIG. 1, except that the high frequency current loop 10 when the main transistor Q1 is off does not pass through the smoothing capacitor C2 in FIG. Is different in that it goes through the smoothing capacitor C2.

FIG. 7 shows an AC according to the fourth embodiment of the present invention.
FIG. 3 is a circuit diagram of an AC converter. In FIG. 7, a third diode is connected in parallel with the sixth capacitor in FIG. 6 with the negative side of the rectifier circuit as the anode.

The circuit operation of FIG. 7 is almost the same as that of FIG. 6, but the potential of the second diode side of the sixth capacitor is kept positive with respect to the negative terminal of the rectifier circuit DB by the action of the third diode. Be done.

[0043]

As described above, according to the present invention, as compared with the conventional AC-AC converter using the active smoothing filter, the circuit configuration is very simple, the cost is low, and further, the capacitor input type smoothing is performed. It is possible to realize an AC-AC converter with low harmonics and high power factor in which the loss of switching elements is as small as that of a conventional AC-AC converter using a circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an AC-AC converter according to a first embodiment of the present invention.

FIG. 2 is a high-frequency waveform chart of each part for explaining the circuit operation of FIG.

FIG. 3 is an input waveform diagram for explaining the circuit operation of FIG.

FIG. 4 is a circuit diagram of an AC-AC converter according to a second embodiment of the present invention.

5 is a high-frequency waveform chart of each part for explaining the circuit operation of FIG.

FIG. 6 is a circuit diagram of an AC-AC converter according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram of an AC-AC converter according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram of a conventional AC-AC converter.

FIG. 9 is a block diagram of another conventional AC-AC converter.

[Explanation of symbols]

 AC Commercial AC power supply DB Diode bridge AF Active smoothing filter BC Drive control circuit IV Inverter LD Load circuit TH Harmonic choke TO Resonance choke TB Ballast choke TA Auxiliary choke Q1 Main transistor Q2 Transistor C1 First capacitor C2 Smoothing capacitor C3 Third capacitor C4 Starting capacitor C5 Resonant capacitor C6 Sixth capacitor D1 First diode D2 Second diode D3 Third diode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasunori Ieshiro 5-1-1 Ofuna, Kamakura-shi Mitsubishi Electric Lighting Co., Ltd. (72) Inventor Masaomi Asayama 5-1-1 Ofuna, Kamakura-shi Mitsubishi Electric Lighting Co., Ltd. In the company

Claims (5)

[Claims] 1. A first capacitor is connected to an output terminal of a rectifier circuit for rectifying a commercial AC power supply voltage, and a smoothing capacitor for smoothing an output voltage of the rectifier circuit is connected to an output terminal of the rectifier circuit. Connected in series with a harmonic choke connected to the smoothing capacitor and a first diode in the charging direction. An LC resonance circuit and a switching element that turns on and off at high frequency are connected to both ends of the smoothing capacitor. The contact between the harmonic choke and the first diode is connected to the switch element through the series circuit of the second diode having the anode connected to the contact side and the load circuit, and the contact between the first diode and the smoothing capacitor, An AC-AC converter characterized in that an auxiliary choke is connected between the second diode and the contact of the load circuit. 2. The AC-A according to claim 1, further comprising a third capacitor connected in parallel with the auxiliary choke.
C converter. 3. The AC-AC converter according to claim 1, wherein a sixth capacitor is connected between the contact of the second diode and the load circuit and the negative terminal of the rectifier circuit. 4. The AC-AC converter according to claim 3, wherein a third diode is connected in parallel with the sixth capacitor with the negative side of the rectifying circuit as an anode. 5. The load circuit includes a discharge lamp connected to the second diode side, and a parallel circuit of a starting capacitor connected to both ends of the discharge lamp.
5. The AC-A according to claim 1, 2 or 3 or 4, which is constituted by a series circuit with a ballast choke connected to the switch element side.
C converter.