JPS6346339A - Power source circuit of air conditioner - Google Patents

Abstract

PURPOSE:To improve reliability of the user on a power relay, a smoothing diode or the like by delaying the on-timing of a first power relay by a predetermined time which is longer than a time where a smoothing capacitor discharges and a DC voltage reaches a release voltage of a second release power relay. CONSTITUTION:A power relay consists of a first power relay 2 which stores the inputs of a room temperature thermistor 12 and a main operating switch 13 and ON-OFF controlled in accordance with the condition of these signals, and a second power relay 4 which detects an output DC voltage of a rectifier circuit consisting of a rectifier diode 7 and a smoothing capacitor 8 by a DC voltage detection circuit 9 and is ON-OFF controlled by a drive coil 5. When the smoothing capacitor 8 is under a discharging condition, a second power relay 4 is turned off, and assumed if the first power relay 2 is turned on, the smoothing capacitor 8 is slowly charged through a current limit resistor 6. When the charge is carried out sufficiently, the second power relay 4 is turned on and is shifted to a normal operation condition. By these procedures, the reliability on the power relay, the rectifier diode can be remarkably improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power supply circuit for an air conditioner, and particularly in an air conditioner that controls the rotational speed of a compressor using an inverter device, etc. The present invention relates to a power supply circuit for an air conditioner suitable for preventing electric current.

[Conventional technology]

In the power supply circuit of an air conditioner equipped with a conventional inverter device, in order to suppress the initial charging current to the smoothing capacitor, the power relay, which is activated depending on the magnitude of the rectified voltage, is generally operated by a current limiting resistor to limit the inrush current. There is. That is, when the smoothing capacitor is not sufficiently charged in its initial state, the power relay is turned off, and the current limiting resistor connected in parallel with the power relay limits the inrush current, and the smoothing capacitor is fully charged. When this occurs, the power relay is turned on and the terminals at both ends of the current limiting resistor are short-circuited, entering a steady state of operation. At the stage when the power relay is turned on, the smoothing capacitor is sufficiently charged, so that almost no charging current flows. A related example of this type of power supply circuit is disclosed in Japanese Utility Model Application No. 61-77684.

[Problem that the invention seeks to solve]

The above conventional technology does not take into account irregular usage conditions such as restarting the power immediately after it is turned off, and after the power is turned off,
The short time it takes for the smoothing capacitor to discharge and for the DC voltage to reach the power relay release voltage (e.g. within 10 seconds)
However, when the power is turned on again, the power relay remains on, causing a large inrush charge current to flow, potentially reducing the reliability of the power relay and rectifier diodes.

An object of the present invention is to provide a power supply circuit for an air conditioner that does not cause the above-mentioned disadvantages under all conditions including the irregular conditions described above.

[Means for solving problems]

The above purpose is to
7- Achieved by delaying the IJ relay on timing by a fixed amount of time longer than the time it takes for the smoothing capacitor to discharge and for the DC voltage to reach the release voltage of the second power relay. At this time, it goes without saying that the off timing of the first power relay is not delayed.

[Operation] That is, once the first power relay is turned off, it remains off for a certain period of time and does not accept even if an on signal is received within that period. Therefore, the smoothing capacitor continues to discharge and the DC voltage drops to a level that turns off the second power relay, so that the above-mentioned disadvantage does not occur.

The above-mentioned fixed time is measured from the time when the first power relay turns off, but when the power is cut off, time measurement is impossible, so the timing when the power is turned on again is detected by a reset signal, etc. This is used as the starting point for time measurement.

Thereby, even in the event of a momentary power outage, the first power relay is turned on after a sufficient time delay for discharging, so the above-mentioned problem can be solved.

Note that since the certain delay time is usually about 10 to 20 seconds, there is no practical problem even if the on-timing of the first power relay is delayed. It goes without saying that the delay time can be further shortened by providing a forced discharge circuit to the smoothing capacitor.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4V]. FIG. 1 shows the overall circuit configuration of an air conditioner according to the present invention. The power relay receives human power from the room temperature thermistor 12 and the main operation switch 13, and turns on and off by controlling the drive coil 3 to be energized by the output from the indoor control unit 14 that controls compressor operation according to the state of these signals. Controlled first power relay 2 and rectifier diode 7
A DC voltage detection circuit 9 detects the output DC voltage of a rectifier circuit consisting of a smoothing capacitor 8 and a DC voltage detection circuit 9, and two second power relays 4 are provided, which are controlled to be turned on and off by a drive filter 5 in accordance with the detected DC voltage. There is.

The former functions to control on/off of the electric power sent to the inverter section 10 and the compressor motor 11, and the latter functions, together with a current limiting resistor, to prevent rush current when the power is turned on.

That is, when the smoothing capacitor 8 is in a discharged state, the second power relay 4 is turned off, and the first power relay 2 is turned off.
Even if the smoothing capacitor is turned on, the smoothing capacitor is gradually charged via the current limiting resistor 6, and when the charging is sufficiently performed, the second power relay 4 is turned on and the normal operating state is entered. . Even if the second power relay 4 is omitted, it is possible to limit the inrush current, but if only the current limiting resistor is used, the current will be energized even during normal operation, resulting in large losses. Don't omit it.

Now, the timing of each operating voltage will be explained with reference to FIGS. 2 and 3. FIG. 2 shows a case where the power outlet is unplugged, the power outlet is turned on again, and the main operation switch is pressed to return to the operating state. This case also applies to cases such as momentary power outages. Period a is the previous operating state, and if the power supply is suppressed here, the first power relay 2 is turned off, and the voltage supply is no longer available (as a result, the DC voltage across the smoothing capacitor begins to decrease.The power supply voltage Even if the power supply voltage returns and the main operation switch is pressed, the first power relay 2 will not be turned on for a certain period of time f from the time when the power supply voltage is restored.The certain period of time f is larger than the discharging time. f) b Since this is set, once the first power relay 2 is turned off, the second power relay 4 is also operated to be turned off. Note that period C is the time from when the second power relay 4 is turned off until the first power relay 2 is turned on, and period d is the time from when the first power relay 2 is turned on to when the second power relay 2 is turned on. This is the time it takes for the power relay 4 to turn on, that is, the charging time for the smoothing capacitor 8.

FIG. 3 is a timing chart when the first power relay 2 is turned on and off by the room temperature thermistor signal. The operation is similar to that shown in FIG. 2, but in this case, the measurement of the fixed time f is started from the time when the first power relay 2 is turned off.

Unlike the case in FIG. 2, the power supply voltage supplied to the indoor control unit is not cut off, so measurement can be performed while the first power relay 2 is off. Regarding the effects,
All (same) as in the case of Fig. 2.

FIG. 4 takes the time when the first power relay 2 is turned off as a starting point and shows the inrush current peak value at a time thereafter. When the second power relay 4 is on, the charge gradually increases as the discharge progresses, but after the discharge progresses and the second power relay 4 turns off, the current limiting resistor 6 causes the charge to increase. The flow is low (can be suppressed).

In this embodiment, since the time until the second power relay 4 is released is about 12 seconds, the constant delay time is f;
The time was set to 5 seconds.

The part indicated by the broken line is actually prohibited, so the maximum peak current of 150 Hz immediately before the power relay is released (12 seconds later)
A did not flow, ensuring the reliability of the power relay and rectifier diode.

〔Effect of the invention〕

According to the present invention, without adding any new parts, the first power relay for controlling the power supply to the inverter is controlled to turn on and off by providing a certain re-on prohibition period after turning off. Coupled with the inrush current limiting circuit consisting of the power relay and current limiting resistor (2), the inrush charging current can be kept to a low level even under any usage conditions such as instantaneous power outages, thereby increasing the reliability of power relays, rectifier diodes, etc. In addition, since the inrush current of rectifier diodes and the like can be reduced, it is possible to downsize the rectifier diodes and the like to the capacity determined by the rated operating state, which has a significant effect on lowering costs.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit configuration diagram of an air conditioner according to the present invention;
The figure shows the operation time chart of each part when the power supply voltage is suppressed.
FIG. 3 is a time chart of the operation of each part based on the room temperature thermistor signal, and FIG. 4 is a relationship diagram between the re-on time after the first power relay is turned off and the inrush current peak value. 1... Commercial power supply, 2... First power relay, 3.
...ml power relay drive coil, 4...second power relay, 5...second power relay (7) drive 1
/J) Illu, 6... Current limiting resistor, 7... Rectifier diode, 8... Smoothing capacitor, 9... DC voltage detection circuit, 1°... Inverter section, 11... Compressor Motor, 12...Room temperature thermistor (room temperature detector), 13
...Main operation switch, 14...Indoor control section, 15.
...Outdoor control section. Agent Patent Attorney Katsutoshi Ogawa't, 1 time 2 mouths 12・Kan; Kan thermistor 13 Chief Saito 1) Entry ÷

Claims (1)

[Claims] 1. A first power relay that operates on and off depending on the presence or absence of a signal from a room temperature detector or a main operation switch, a rectifier circuit consisting of a rectifier element and a smoothing capacitor, and a rectifier circuit that operates according to the magnitude of the output voltage of the rectifier circuit. A second power relay that operates, a current limiter connected in parallel with the second power relay, and a certain delay time are provided for the signals of the room temperature detector or the main operation switch, and the first power A power supply circuit for an air conditioner characterized by operating a relay.