JPS60245494A - Power transistor protecting device of frequency control type air conditioner - Google Patents

Abstract

PURPOSE:To effectively protect a power transistor by detecting temperature of temperature detecting means provided on the transistor or a heat sink plate of the transistor. CONSTITUTION:A thermistor 1 detects the temperature (t) of a power transistor, and inputs it to a microcomputer 3 together with the set value T of a setter 5. An LSI3 has a comparator, a timer, a shifter and a variable frequency output circuit. The comparator compares the temperature detected value with the set value, the timer applies the comparison at the timing, and the output circuit stepwisely varies the operating frequency of a compressor 7. The shifter outputs an electric signal for sequentially shifting the operating frequency of the compressor 7 by the electric signal of the comparator.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a power transistor protection device for a frequency-controlled air conditioner whose operation control device is equipped with a microcomputer.

Conventional configuration and its problems Power transistors in frequency-controlled air conditioners generate a large amount of heat, and due to the need for temperature protection, they are installed on the power transistor itself or on a power transistor heat sink (hereinafter referred to as a heat sink). The temperature is controlled by a temperature relay, and when the temperature exceeds the set temperature, the temperature relay operates, and this electrical signal stops the compressor, and after the temperature of the power transistor or heat sink has decreased, the compressor starts operating again. ,
In a separate air conditioner where the indoor and outdoor units are separated and the outdoor unit is equipped with a power transistor, the temperature of the power transistor will increase when the outside temperature is high during cooling operation and the cooling capacity is most needed. This had the disadvantage that the air conditioner could not be cooled because the temperature relay would operate and the compressor would stop.

OBJECTS OF THE INVENTION The present invention aims to solve the above-mentioned conventional problems and achieve both serial operation under high load conditions and power transistor protection.

Structure of the Invention In order to achieve this object, the present invention, as shown in FIG. A comparison means compares the set temperature value with the timing given by the timing means, and a transition means sequentially shifts the operating frequency of the compressor based on an electric signal from the comparison means; It is composed of a storage means that stores a variable frequency output mode that controls the operating frequency in stages, and an output means that operates the compressor at a frequency specified by an electrical signal in the storage means, and in the case of high load conditions, etc. The frequency of the compressor is controlled according to the temperature of the power transistor.

This configuration makes it possible to simultaneously operate the air conditioner continuously and protect the power transistor even under high load conditions.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 4 of the accompanying drawings.

In FIG. 1, the control circuit includes a thermionic circuit 1 that detects the temperature t of the power transistor, a temperature detection device 2 that converts the detected temperature t into an electrical signal and outputs it, and a resistor device 5 that provides an electrical signal of the temperature set value T. , microcomputer (hereinafter referred to as
An oscillating device 6 that gives pulses of a constant frequency to the lower LSI 3, an electrical signal from the temperature detecting device 2, and a temperature setting value T.
A comparison circuit that compares and determines the electrical signals of frequency divider circuit) and
An LSI 3 that includes a transition circuit that outputs an electrical signal that sequentially shifts the operating frequency of the compressor 7 according to the electrical signal of the comparison circuit, and a power that drives the compressor 7 at a frequency specified by the electrical signal output from the LSI 3. The compressor 7 is equipped with an output device using a transistor 4, a power supply device 8 that supplies the operating voltage of the compressor 7 to the power transistor 4, and the compressor 7.

To explain the relationship between the block diagram shown in FIG. 2 and the control circuit diagram shown in FIG. 1, the thermistor 1 is used as a temperature detection means, the resistance device 5 is used as a temperature setting value, and the comparison circuit built in the LSI 3 The timer circuit, transition circuit, and variable frequency output circuit each include a comparison means, a timing means, a transition means,
It corresponds to a storage means, and the power transistor 4 corresponds to an output means.

Next, the operation of the control circuit having the above configuration will be explained with reference to FIGS. 3 and 4.

At the start of operation, L! The built-in timer circuit in 1liI3 is ○N
Then, the detected temperature t detected by the thermistor 1 installed near the power transistor 4 is compared with the set temperature T, and t
If ≦T, the program proceeds to operation I (operating the compressor 7 at a high frequency of 41), and the timer becomes n=n-1-1 and continues counting. When the heat load is large or the outdoor temperature rises, the temperature of the power transistor 4 increases, and when t≧T, the power transistor 4 operates at the operating If (operating the compressor 7 at a low frequency of 12), and the amount of heat generated by the power transistor 4 increases. is reduced to protect the power transistor 4.

The flow chart of FIG. 3 and the time chart of FIG. 4 show the flow of the above operations.

The time chart in Figure 5 shows two temperature settings (T
1≦T2), and when the detected temperature t exceeds T2, the operating frequency of the compressor is lowered by one step, and conversely, when the detected temperature t exceeds T2, the compressor operating frequency is lowered by one step.
This is an example in which the operating frequency is raised by one level when the temperature drops below T1, and consideration is given to achieving the maximum capacity of the air conditioner while controlling the temperature of the power transistor. Similar effects can be obtained even if the operating frequency of the compressor is changed in multiple stages using multiple temperature settings and time controls in this manner.

Effects of the Invention As is clear from the above embodiments, the power transistor protection FPMM of the frequency-controlled air conditioner according to the present invention has the following characteristics:
Under high load conditions, the temperature is detected by a temperature detection means installed on the power transistor or the heat sink of the power transistor, and the operating frequency of the compressor is controlled so that the temperature of the power transistor does not exceed a certain temperature. It has excellent effects such as enabling continuous operation of the inverter air conditioner and ensuring more reliable protection of the power transistor, which is the heart of the inverter air conditioner.

[Brief explanation of drawings]

FIG. 1 is an electronic circuit diagram of an operation control device equipped with a microcomputer according to the present invention, and FIG. 2 is a block diagram expressing a power transistor protection device using function realizing means.
3 and 4 are a flowchart and a time chart showing one embodiment of the power transsonuta protection control of the present invention, and FIG. 5 is a time chart of another embodiment of the present invention. 1-...Thermistor, 2...Temperature detection device, 3...
・Microcomputer, 4...Power transistor,
5. Resistance device, 6. Oscillator, 7. Compressor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure II

Claims (1)

[Claims] Compressors whose power supply is frequency controlled, indoor heat exchangers,
A refrigeration cycle is formed by connecting a pressure reducing device, an outdoor heat exchanger, etc. in a ring, and a temperature detection means detects the temperature of the power transistor or the power transistor heat sink, converts it into an electric signal, and outputs it, and at least one temperature setting. a comparison means for comparing a value with an electric signal and outputting a control signal; a timekeeping means for giving a timing for comparing the temperature set value and the detected temperature; and an electric signal from the comparison means to sequentially shift the operating frequency of the compressor. a storage means storing a variable frequency output mode for controlling the operating frequency of the compressor in stages according to the electric signal of the transition means; and a designated membrane device based on the electric signal of the storage means.