JPS6323740B2 - - Google Patents

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention provides an alternative method for connecting an AC load and a DC load to which power is supplied from a common power supply path to an AC power source or a DC load connected to the power supply path. The present invention relates to a switching circuit that selectively switches depending on the power source.

(Prior Art) For example, a lighting device may be configured so that the lighting of a discharge lamp can be arbitrarily switched between lighting using a conventional ballast and lighting using an inverter. In this case, an AC power source is connected to the ballast, which is an AC load, and a DC power source is connected to the inverter, which is a DC load, but since both loads are not energized at the same time, the power supply path is common. The load side is configured to be switched depending on the AC power supply or DC power supply connected to this power supply path.

Conventionally, as this type of switching circuit, for example, the first
The configuration shown in FIG. 2 and FIG. 2 is adopted. Both of these are configured to selectively supply power corresponding to an AC load 14 or a DC load 15 through a common power supply line 13 that can be selectively connected to both a DC power supply 11 and an AC power supply 12. The electromagnetic relay 16 for switching is provided in a circuit so that it is excited only by AC power. The a contact 16a is interposed between the power supply path 13 and the AC load 14, and the b contact 16b is interposed between the power supply path 13 and the DC load 15.

With this configuration, when the AC power source 12 is connected to the power line 13, the electromagnetic relay 16 is excited, closes the a contact 16a and opens the b contact 16b, so only the AC load 14 is connected to the power line 13. , are energized by the corresponding AC power supply 12. On the other hand, when the DC power supply 11 is connected to the power supply path 13, the electromagnetic relay 16 is demagnetized, so the a contact 16
A is open, and b contact 16b is closed. Therefore, only the DC load 15 is connected to the power supply path 13 and is energized by the corresponding DC power supply 11 .

(Problems to be Solved by the Invention) However, in the conventional configuration described above, switching on the load side is performed by opening and closing the A contact 16a and the B contact 16b, so the travel time of the contacts must be taken into consideration. First, a certain amount of time is required for switching. Therefore, if the power supply side is changed from the AC power supply 12 to the DC power supply 11 at a timing earlier than this certain time, for example,
If the switch is switched to , the DC power will flow into the AC load 14 . Furthermore, since the contacts of electromagnetic relays generally have a short opening distance, the DC current continues to flow while drawing an arc even after the opening operation, causing the problem that it cannot be interrupted. As a result, electromagnetic relay burnout and AC load 14
Problems such as burnout have occurred.

The present invention was developed in view of the above problems, and has a circuit design that makes the switching section contactless, speeds up the switching operation, sufficiently follows the fast switching speed, and ensures reliable insulation between the DC side and the AC side. It is an object of the present invention to provide a switching circuit that facilitates the switching and further simplifies the circuit configuration.

[Structure of the invention]

(Means for Solving the Problems) The switching circuit of the present invention includes a power supply path to which an AC power source and a DC power source are selectively connected, an AC load connected to this power path via a thyristor, and a power supply path to which an AC power source and a DC power source are selectively connected. A DC load connected via a semiconductor switching element, a light receiving element provided in the conduction control section of the semiconductor switching element and turning off the semiconductor switching element only when receiving light, and a zero voltage point of the AC power source. a pulse generation circuit that generates a pulse voltage every half cycle to provide a gate signal to the thyristor; a capacitor that is charged by the pulse voltage of the pulse generation circuit; and the AC power source connected to the power supply path. and a light emitting element that controls the light receiving element by continuously emitting light based on the charged charge of the capacitor when the light receiving element is in use.

(Function) When an AC power supply is selectively connected to the power supply path, the pulse generation circuit generates a pulse voltage every half cycle in response to the zero voltage point of the AC power supply, and provides a gate signal to the thyristor. Supply AC power to an AC load. Also, at this time, a capacitor is charged with the pulse voltage of the pulse generation circuit, and the charge in the capacitor causes the light emitting element to emit light continuously and controls the light receiving element, and by turning off the semiconductor switching element, power is supplied to the DC load. Not supplied.

When a DC power source is selectively connected to the power supply path, DC power is supplied to the DC load. Further, since the pulse generating circuit does not generate a pulse voltage, no pulse voltage is generated, and the thyristor is not conductive, so no power is supplied to the AC load.

(Example) The present invention will be described below with reference to an example shown in FIG. Note that parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

The embodiment shown in FIG. 3 also has a common power supply path 13 to which the DC power supply 11 and the AC power supply 12 are selectively connected. The AC load 14 is connected via a bidirectional thyristor (hereinafter referred to as a triax) 20, and the DC load 15 is connected via a semiconductor switching element such as a transistor 21. A control circuit 25 is connected to the power supply path 13 to control the conduction of the triac 20 and the transistor 21 in accordance with the power applied to the power supply path 13.

The control circuit 25 has a full-wave rectifier 28 connected to the power supply path 13 via voltage dividing resistors 26 and 27. Output side electric circuits P and N of this full-wave rectifier 28
Resistors 30 and 31 are connected in series between them, and
The intermediate connection point is connected to the base of a transistor 34 via a resistor 32. Further, a diode 36 is inserted in the forward direction in the electric path P, and the cathode of this diode 36 and the transistor 34 are connected to each other.
A primary winding 37a of a pulse transformer 37 is connected between the collector of the pulse transformer 37 and the collector of the pulse transformer 37. In addition, pulse transformer 3
The secondary winding 37b of 7 is connected to the gate of the triac 20. These components constitute a pulse generating circuit 38 that generates a pulse voltage every half cycle corresponding to the zero voltage point of the AC power source 12. The transistor 34 has its emitter connected to the electric path N, and its collector connected to a resistor 39 and a capacitor 40.
It is also connected to a smoothing circuit consisting of, and communicates with the electric path N via this smoothing circuit. 42 and 43 are voltage dividing resistors,
It is connected between the cathode of the diode 36 and the electric path N. Further, a photodiode 45a as a light emitting element of a photocoupler is connected in the forward direction from the upper end of the capacitor 40 as shown in the figure to the intermediate connection point between the voltage dividing resistors 42 and 43. Here, the voltage dividing value of the voltage dividing resistor 43 is set lower than the voltage across the capacitor 40, and the photodiode 45a is configured to continuously emit light based on the collector potential of the transistor 34. Note that both 47 and 48 are capacitors, which are connected as shown.

Furthermore, the conduction control unit 50 of the transistor 21 interposed between the DC load 15 and the DC load 15 is configured as follows. That is, one end of a resistor 51 is connected to the collector of the transistor 21, and the other end is connected to the base of the transistor 21 through a diode 52 in the forward direction. The anode of the diode 52 is connected to the collector of a phototransistor 45b serving as a light receiving section of the photocoupler. Further, the emitter of this phototransistor 45b is connected to the emitter of the transistor 21.

In the above configuration, the AC power supply 12 is connected to the power supply path 13.
is connected, the transistor 34 is turned off near the zero cross of the AC power, and turned on at other times. Therefore, this transistor 34
The pulse transformer 37 constituting the pulse generating circuit 38 connected to the collector of the pulse transformer 37 applies a pulse generated by turning off the transistor 34 at each zero cross to the gate of the triac 20, thereby turning the triac 20 into a conductive state and generating an alternating current. AC power is supplied to the load 14.
On the other hand, the collector potential of the transistor 34, that is, the pulse output, is applied to the resistor 39 and the capacitor 40.
smoothed by Then, the phototransistor 45b is energized by the potential difference between the potential across the capacitor 40 and the voltage divided by the voltage dividing resistor 43, causing it to emit light continuously. Therefore, the phototransistor 45b is energized, short-circuiting the conduction control section 50 of the transistor 21, and maintaining its off state. Therefore, AC power is not supplied to the DC load 15.

On the other hand, when the DC power supply 11 is connected to the power supply path 13, the transistor 3 provided in the control circuit 25
4 is continuously in the on state, no pulse is supplied to the gate of the triac 20, and the triac 20 becomes non-conductive. Furthermore, since the collector potential of the transistor 34 is continuously close to the ground potential, the photodiode 45a becomes reverse biased and the phototransistor 45b is deenergized. Therefore, the transistor 21 becomes forward biased and conducts, supplying DC power to the DC load 15.

〔Effect of the invention〕

According to the present invention, since the electrical circuit switching from the common power supply circuit to the load is made contactless using a semiconductor element,
There is no need to worry about contact travel time or arcing, it can fully follow the switching speed of the power source, and the use of a light emitting element and light receiving element ensures electrical insulation, ensuring insulation between the DC and AC sides. I can,
Circuit design becomes easier. Furthermore, since switching of the thyristor for the AC load and switching of the semiconductor switching element for the DC load can be performed by one pulse generating circuit, the circuit configuration can be simplified. In addition, the use of semiconductors has many effects, such as improved environmental resistance such as mechanical wear and contact oxidation compared to when contacts are used.

[Brief explanation of the drawing]

Figures 1 and 2 are circuit diagrams showing the conventional configuration, and Figure 3 is a circuit diagram showing the conventional configuration.
The figure is a circuit diagram showing an embodiment of the switching circuit according to the present invention. 1...DC power supply, 12...AC power supply, 13...
Power supply path, 14... AC load, 15... DC load,
20...Thyristor, 21...Semiconductor switching element, 38...Pulse generation circuit, 40...Capacitor, 45a...Photodiode as a light emitting element, 45b...Phototransistor as a light receiving section, 50...Continuity control section .

Claims (1)

[Claims] 1. A power supply path to which an AC power supply and a DC power supply are selectively connected; An AC load connected to this power supply route via a thyristor; A DC load connected to the power supply route via a semiconductor switching element. a load; a light-receiving element that is provided in the conduction control section of the semiconductor switching element and turns off the semiconductor switching element only when receiving light; and a light-receiving element that generates a pulse voltage every half cycle in response to the zero voltage point of the AC power supply; a pulse generating circuit that applies a gate signal to the thyristor; a capacitor that is charged by the pulse voltage of the pulse generating circuit; and a capacitor that is charged by the pulse voltage of the pulse generating circuit; A switching circuit comprising: a light-emitting element that emits light to control the light-receiving element;