JPS60204223A - Power source circuit device - 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] [Technical Field of the Invention] The present invention relates to a power supply circuit device that rectifies and smoothes an AC power supply, and in particular to a power supply circuit device that prevents inrush current at the start of charging of a smoothing capacitor and supplies DC power to a load side. The present invention relates to a power supply circuit device that can detect voltage abnormalities.

[Prior art]

As a conventional power supply circuit device of this type for rectifying and smoothing an alternating current power source, one shown in FIG. 1, for example, is known. This uses an inverter to control the frequency.
The phase alternating current power is input to a rectifier circuit 3 via an electromagnetic switch 2, converted to direct current, smoothed by a smoothing capacitor 4, and supplied to a transistor module 5 which together with the rectifier circuit 3 constitutes an inverter. The transistor module 5 has multiple output frequencies controlled by a controller 6, and multiple loads 7 are operated by a predetermined frequency power source. Further, the electromagnetic switch 2 is controlled to open and close by the controller 6 when the load 7 is activated and stopped.

However, in the conventional power supply circuit device as described above,
When the electromagnetic switch 2 is turned on, the smoothing capacitor 4 starts charging, but a rush current may flow at the start of charging, and at this time there is a problem in that an overcurrent exceeding a permissible value flows. Further, even if the supply voltage decreases due to loss of capacity of the smoothing capacitor 4 or overload, there is no means to detect this, and there are also problems such as overcurrent flowing.

[Summary of the invention]

This invention was made by focusing on the above-mentioned conventional problems, and by connecting a resistor in parallel with the electromagnetic switch and providing a detection circuit to detect the smoothed DC voltage, the smoothing capacitor can be improved. It is an object of the present invention to provide a power supply circuit device that can prevent inrush current at the start of charging, detect a drop in voltage supplied to a load, and prevent overcurrent and the like.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Note that the same or equivalent parts as those in the conventional FIG. 1 will be described with the same reference numerals.

FIG. 2 is an electric circuit diagram showing a circuit configuration of a power supply circuit according to the present invention, and shows a case where the present invention is applied to an air conditioner that controls the frequency of a compressor motor using an inverter. In the figure, 1 is a power terminal board into which 3-phase AC power # (R, S, T) is input, 2 is an electromagnetic switch connected between the power terminal board 1 and the rectifier circuit 3, and 2 is an electromagnetic switch connected between the power terminal board 1 and the rectifier circuit 3. It is interposed between two phases, an R phase and an S phase, and the T phase is directly connected to the rectifier circuit 3. A smoothing capacitor smoothes the DC output from the 4-piece rectifier circuit 3, a transistor module 5 forms an inverter together with the rectifier circuit 3, and a microcomputer controls the input/output circuits necessary for the 6-piece air conditioner. The controller controls the output frequency of the transistor module 5 and operates the compressor motor 8 with a predetermined frequency power supply.
At the same time, a driving current is applied to the coil 2a of the electromagnetic switch 2 to control opening and closing of the electromagnetic switch 2. 9 is a step-down transformer that supplies power to the controller 6, a resistor connected in parallel with the 10-piece electromagnetic switch 2, and is provided in parallel with the R-phase contact. 11 is the DC voltage (bus voltage)
This is a detection circuit that detects, and is configured as follows.

That is, 12.13 is a resistor for dividing the bus voltage, 14 zener diodes, 15 photocouplers consisting of a photodiode and a phototransistor, 16 is a field effect transistor, 11 is an NPN) transistor, 18°1
9.20 is the resistance. Further, the transistor 17 is directly connected to the photocoupler 15 and the field effect transistor llt direct current power supply via the resistor 21, and the collector of the transistor 17 is connected to the controller 6.

In the power supply circuit device configured as described above, when three-phase AC power is applied to the power supply terminal board l, the step-down transformer 9
Power is supplied to the controller 6 via the controller 6, and operation control of the air conditioner is started. When the power is turned on, the electromagnetic switch 2 is OFF, so the single-phase power of the R phase and T phase is input to the rectifier circuit 8, but since the resistor 10 is connected to the R phase, the smoothing capacitor is connected to the rectifier circuit 8. 4 units are gradually charged. Then, when the bus voltage rises and exceeds a predetermined value, a current flows through the Zener diode 14, the photodiode of the photocoupler 15 emits light, and the field effect transistor 11t is turned ON. As a result, a pace current flows through the transistor 17, turning it on, and an rjL signal (low level signal) is input to the controller 6. That is, an L signal when the bus voltage is above a predetermined value and an H signal (high level signal) when the bus voltage is below a predetermined value are input to the controller 6, respectively.

When a fixed time signal is input from the controller 6rj and the detection circuit 11, the electromagnetic switch 2 is activated when the clamp bus voltage exceeds a predetermined value for a fixed time.

This is to prevent an inrush current at the start of charging the smoothing capacitor 4, and for a certain period of time after the power is turned on, the resistor 1
A single-phase power supply limited by 0 is input to the rectifier circuit 3, and the smoothing capacitor 4 is gradually charged. When the electromagnetic switch 2 is turned on, a three-phase AC power source is directly input to the rectifier circuit 3, and the compressor motor is driven by a power source of a predetermined frequency that is controlled by the eight controller 6. Also, when the bus voltage falls below a predetermined value while the electromagnetic switch 2 is operating, that is, when the H signal is input to the controller 6 from the detection circuit 11, the controller 6tj refreshes the electromagnetic switch 2. and stop operation of the air conditioner. Thereby, it is possible to prevent an overcurrent from flowing to the bus bar when the bus voltage decreases due to, for example, loss of capacity of the smoothing capacitor 4 or an overload condition of the compressor motor 8.

Next, the process of detecting the above-mentioned bus voltage and controlling the operation of the air conditioner will be described in detail based on the flowchart of FIG. In addition, there are 3 phases on the power terminal board 1! When the power is turned on, a power-on reset is applied and operation control is started, and the opening and closing of the two electromagnetic switches are controlled according to a control flowchart (not shown); however, when the power-on reset is applied, the two electromagnetic switches are turned off. Tonanashi, this electromagnetic switch 2 is ON.
When it is 1, and when OF'F', O is the flag P.
The base control signal is output to the transistor module 5 only when the flag PL is set to 1, and the 8 compressor motors are driven at a predetermined frequency.

First, in step 22, the controller 6Fi detection circuit 11
It is determined whether the bus voltage is below a predetermined value based on a signal from the bus line voltage, and if it is below the predetermined value, the process proceeds to step 23, and it is determined whether the flag FL is set to 1. If the flag PL is set above IK, the operation is stopped in the inspection mode in step 24, and if it is set to 0, the electromagnetic switch 2 is prohibited from being turned on in step 25.

In step 22, if the bus voltage exceeds the predetermined value, the process proceeds to step 26, where it is determined whether the flag PL is set to 1. If the flag PL is not set to 1, the flag FL is set to 1 in step 27, and a timer (not shown) provided in the controller 6 is set in step 28. Also, flag PL
If the timer is set to 1, the process proceeds to step 29, where it is determined whether or not the timer is counting up. If the timer is counting up, the electromagnetic switch 2 is turned off at step 30.
Allow N.

As mentioned above, when the power is turned on, the smoothing capacitor 4 is gradually charged through the resistor lO, and when the bus voltage exceeds a predetermined value for a certain period of time set by the timer, the electromagnetic switch 2 is allowed to turn on. By giving smoothing capacitor 4
This avoids a rush current at the start of charging, and prevents overcurrent from flowing through the contacts of the electromagnetic switch 2 and the diode stuff of the rectifier circuit 3. In addition, if the bus voltage decreases while the compressor is running, it enters inspection mode and stops all functions to prevent capacity loss of the smoothing capacitor 4 due to changes over time, insufficient supply voltage, and overcurrent due to compressor overload conditions. ing.

〔Effect of the invention〕

As explained above, according to the present invention, a resistor is connected in parallel with the electromagnetic switch, and a detection circuit for detecting the smoothed DC voltage is provided, and when the detected voltage value exceeds a predetermined value for a certain period of time, The electromagnetic switch is activated, and the electromagnetic switch is cut off when the detected voltage value falls below a predetermined value while the electromagnetic switch is operating, thereby avoiding inrush current when charging the smoothing capacitor starts. It can prevent overcurrent from flowing through the contacts and rectifier circuit of the electromagnetic switch, and can detect when the supply voltage to the load is insufficient, preventing overcurrent from flowing due to an overload condition. effective.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing a conventional power supply circuit device, FIG. 2 is an electric circuit diagram showing a power supply circuit device according to the present invention, and FIG.
The figure is a flowchart showing the process of detecting the bus voltage and controlling the operation. 1...3-phase AC power supply 2...Electromagnetic switch 3...Rectifier circuit 4...Smoothing Capacitor 5...Transistor module 6...
......Controller 7...Load 8...Compressor motor lO...Resistor 11...Detection circuit The same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Figure 7 Figure 2 0

Claims (1)

[Claims] In a power supply circuit device in which AC power is input to a rectifier circuit via an electromagnetic switch, and the rectified DC is smoothed by a capacitor and supplied to a load, a resistor is connected in parallel with the electromagnetic switch, and a smoothing A detection circuit is provided to detect the DC voltage, and when the detected voltage value exceeds a predetermined value for a certain period of time, the electromagnetic switch is operated, and while the electromagnetic switch is operating, the detected voltage value is the predetermined value. A power supply circuit device characterized by being provided with means for shutting off the electromagnetic switch when the following conditions occur.