JPS61263099A - Ac-dc conversion circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial field of application Pilotage BA is an AC power source that passes DC current from an AC power source to a load.
The present invention relates to a DC conversion circuit, and particularly to a discharge lamp lighting circuit that lights a discharge lamp as a load.

Conventional technology The lighting circuit for lighting a discharge lamp with an AC power supply is as follows:
Lighting circuits using magnetic circuit components such as choke coils and leakage transformers are most commonly used. However, these are heavy and large, and have not been considered suitable for ceiling mounting. Furthermore, lighting circuits based mainly on magnetic circuit components generate large amounts of heat and power loss, and are considered undesirable from the standpoint of efficiency.

Another type of lighting circuit has been known that mainly uses electronic circuits to flow direct current from an alternating current power source to a discharge lamp. This type of lighting circuit is known, for example, from Japanese Unexamined Patent Publication No. 65-2
As shown in Publication No. 6980, the configuration was as shown in Figure 3. In Figure 3, 1 is an AC power supply, 2 is
is a rectifier circuit, and 3 is a capacitor for smoothing the rectified pulsating voltage. This capacitor 3 and rectifier 2 constitute a power supply smoothing circuit. At the output end of the power supply smoothing circuit, a transistor 4 and a choke are connected. A discharge lamp 6 is connected to the coil 5 via the coil 5. 7 is a control circuit for controlling on/off of the transistor 4; Further, 8 is a diode for allowing the electromagnetic energy of the choke coil 5' to flow through the discharge lamp 6 while the transistor 4 is off, and 9 is a capacitor for smoothing the voltage across the discharge lamp e. This lighting circuit is called a step-down chopper circuit.

The operation of the conventional example shown in FIG. 3 will be described below.The output of the commercial AC power supply 1 is rectified by a rectifier circuit 2, and further smoothed by a capacitor 3 to obtain a relatively flat DC output.

From the output of the power supply smoothing circuit composed of the rectifier circuit 2 and the capacitor 3, current flows to the discharge lamp 6 via the choke coil 5 when the transistor 4 is turned on. Furthermore, the electromagnetic energy stored in the choke coil 6 at this time is transferred to the diode 8 when the transistor 4 is turned off.
It flows to the discharge lamp 6 via. Further, the on/off control of the transistor 4 is controlled by a control circuit 7 so that the discharge lamp 6 is lit under predetermined electrical conditions. This on/off control performs switching at a high frequency in order to make the lighting circuit lightweight and compact, thereby making it possible to use a choke coil with a small inductance as the choke coil 5.

Problems to be Solved by the Invention In such a conventional discharge lamp lighting device, a capacitor is directly connected to the output terminal of the rectifier circuit 2 to smooth out the ripple voltage.
, the diode 8, the control circuit 7, and the capacitor 9 allow the current to continue flowing through the discharge lamp 6 without interruption.
It is possible to prevent the arc from extinguishing or turning off. On the other hand, since a phase-advanced current flows from the AC power supply 1 to the capacitor 3 via the rectifier circuit 2, ■the input power rate is low;■the AC current 1
There were problems such as a large inrush current flowing when the power was turned on, which could damage the power switch or rectifier circuit.

The present invention has been made in view of the above points, and has a simple configuration that allows current to flow seamlessly through the load, while providing a high power factor and a low inrush current when AC power is turned on. The purpose is to provide a switching circuit.

Means for Solving the Problems In order to solve the above problems, the present invention provides an AC power supply, a rectifier circuit for rectifying the AC voltage of the AC power supply to output a pulsating voltage, and an output terminal of the rectification circuit. a series circuit of a connected load, a choke coil, and a controlled semiconductor switch; and a series circuit of the choke coil and the load connected in parallel to the series circuit of the series circuit and connected in the opposite direction to the controlled semiconductor switch. a diode, a capacitor connected in parallel to the series circuit portion of the choke coil and the controlled semiconductor switch in the series circuit, and connected to be charged from the rectifier circuit through the load; A control circuit that controls the controlled semiconductor switch so that current flows under the electrical conditions of A current is caused to flow from the capacitor to the choke coil via the switch, and when the controlled semiconductor switch is turned off, electromagnetic energy from the choke coil is caused to flow to the load via the diode.

Operation According to the present invention, with the above-described configuration, the current that flows into the capacitor when the AC power is turned on does not flow directly from the rectifier circuit, but through the load. Therefore, the in-rush current is limited by the impedance of the load, and excessive in-rush current can be prevented. In addition, the capacitor accumulates a voltage charge equal to the voltage drop due to the load from the instantaneous value of the power supply voltage, and this charge is discharged to the load by turning on and off the controlled semiconductor switch. Since current flows from the AC power source over a voltage phase range, a high input power factor can be obtained.

Embodiment FIG. 1 is a diagram showing the configuration of a discharge lamp lighting circuit which is an AC-DC conversion circuit in an embodiment of the present invention. In FIG. 1, 1 is an AC power supply, 2 is a rectifier circuit, 4 is a transistor which is a controlled semiconductor switch, 5 is a choke coil,
6 is a discharge lamp which is a load, 7 is a control circuit, 8 is a diode, and 9 is a capacitor.The above configuration is the same as the conventional example shown in FIG. 3, and the same numbers are given. A capacitor 10 is connected in parallel to the series circuit of the choke coil 6 and the controlled semiconductor switch 4, and is connected to be charged from the rectifier circuit 2 via the discharge lamp 6.

The operation of the embodiment shown in FIG. 1 will be explained below.

The output of the AC power supply 1 is rectified by a rectifier circuit 2 and becomes a pulsating voltage. The capacitor 1o is charged via the discharge lamp 6 by the output of the rectifier circuit which becomes a pulsating voltage. At this time, the maximum charging voltage of the capacitor 1o is approximately the maximum value of the pulsating current voltage, that is, the value obtained by subtracting the voltage of the discharge lamp 6 from the maximum value of the instantaneous voltage of the AC power supply. Furthermore, since the capacitor 1o is connected in parallel with the series circuit of the choke coil 5 and the transistor 4, when the controlled semiconductor switch 4 is turned on, current flows through the choke coil 6 through the transistor 4. When the choke coil 6
The electromagnetic energy stored in the discharge lamp 6 flows through the diode 8 to the discharge lamp 6. Since current is caused to flow through the discharge lamp 6 using the charge accumulated in the capacitor 10 in this manner, current can continue to flow through the discharge lamp 6 even if the instantaneous value of the AC voltage decreases. Therefore, it can be stably lit without turning off. Furthermore, in a phase where the instantaneous value of the AC voltage is relatively high, when the transistor 4 is turned on, current flows from the AC power supply 1 via the rectifier circuit 2, the choke coil 6, and the discharge lamp 6, and the AC current flows over a wide AC voltage phase range. Current flows from the power supply.

Therefore, a high input power factor can be obtained. Further, the on/off control of the transistor 4 is controlled by a control circuit 7 so that the discharge lamp 6 is turned on under a predetermined drowsiness condition.

Next, FIG. 2 is a diagram showing a discharge lamp lighting circuit according to another embodiment of the present invention. In FIG. 2, a series circuit of a transistor 4, a choke coil 6, and a discharge lamp 6 is connected to a rectifier circuit 2 in the reverse order from that of the embodiment of FIG. 1, but the circuit operation is similar to that of the embodiment of FIG. It is similar to

In the embodiment, the load was a discharge lamp, but other loads such as a resistor or a light bulb may be used. Further, although the controlled semiconductor switch is a transistor, it goes without saying that other controlled semiconductor switches such as a thyristor or a bidirectional thyristor may be used. In addition, in the embodiment, a separately excited type circuit is used in which the transistor is driven and controlled by an independent control circuit, but a self-excited type circuit in which voltage and current are obtained from a part of the conversion circuit to drive and control the transistor may be used. Needless to say.

It goes without saying that a capacitor that does not increase the inrush current to an excessive value or significantly reduce the input power factor may be connected in parallel to the output end of the rectifier circuit.

Effects of the Invention As described above, according to the present invention, it is possible to supply power to the load without interruption with an extremely simple configuration, while also achieving a small inrush current and a high power factor when AC power is turned on. An AC-DC switching circuit is obtained, which is extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a discharge lamp lighting circuit which is an AC-DC conversion circuit in one embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a discharge lamp lighting circuit in another embodiment, and FIG. 1 is a diagram showing the configuration of a conventional discharge lamp lighting circuit. 1... AC power supply, 2... Rectifier circuit, 3
... Capacitor, 4 ... Transistor, 5
...Choke coil, 6...Discharge lamp, 7.
...Control circuit, 8...Diode, 9,10
・・・・・・Capacitor.

Claims (1)

[Claims] an AC power source, a rectifier circuit that rectifies the AC voltage of the AC power source and outputs a pulsating voltage, a series circuit including a load connected to an output end of the rectifier circuit, a choke coil, and a controlled semiconductor switch; A diode connected in parallel to the series circuit section of the choke coil and the load in the series circuit and connected in the opposite direction to the controlled semiconductor switch; a capacitor connected in parallel to the series circuit section so as to be charged from the rectifier circuit through the load; and a control circuit that controls the controlled semiconductor switch to cause current to flow through the load under predetermined electrical conditions. When the controlled semiconductor switch is turned on, current flows from the capacitor to the choke coil through the controlled semiconductor switch, and when the controlled semiconductor switch is turned off, the electromagnetic energy of the choke coil flows through the diode to the load. An AC-DC conversion circuit characterized in that: