JPH0523349B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention effectively suppresses surge voltage suppressing circuits for on-vehicle refrigerators, especially surge voltages induced in transformers by switching elements that operate alternately. The present invention relates to a surge voltage suppression circuit for an on-vehicle refrigerator in which a surge voltage suppression element is connected to a position where the switching element is prevented from being destroyed.

[Conventional technology]

There is a refrigerator that compresses and liquefies a gaseous refrigerant using a vibrating compressor, and performs cooling etc. using the heat of vaporization when the liquefied refrigerant is vaporized. Conventionally,
As an example of a vibrating compressor drive control system used in the refrigerator, there is a system as shown in FIG. In FIG. 4, the vibrating compressor 5 connects the DC power source V to the primary windings of the transformer 4 with different polarities by alternately switching the switching transistors TR ₁ and TR ₂ into conductive states. Apply voltage alternately to the line to create a resonant state,
That is, the drive is controlled so as to obtain maximum efficiency.
At this time, the switching transistor TR ₁ ,
TR ₂ is alternately switched between a conductive state and a non-conductive state in a manner such as the current waveform shown in FIG. 5, and the switching frequency is controlled to match the resonant frequency of the vibrating compressor 5. To be more specific, base current "I _B " is alternately supplied from the drive circuit 1-3 to the bases of switching transistors TR ₁ and TR ₂ so that the collector current "I _C " in FIG. 5 is switched. Ru. That is, by supplying a so _- called trapezoidal waveform as _shown in the figures as a current waveform obtained by multiplying the base current "I _B " by the current amplification factor "h _FE ", The switching transistors TR ₁ and TR ₂ are alternately switched into a conductive state and a non-conductive state by providing the following conditions: I _C ≧ h _FE × I _B , respectively, to obtain a driving power source with a desired frequency. There is. Conventionally, as explained above, the vibrating compressor 5 has been driven using a drive power source that matches the resonant frequency of the compressor 5.

As described above, the on-vehicle refrigerator drives the compressor 5 using a drive power source that matches the resonant frequency of the vibrating compressor 5, and the switching transistors TR ₁ and TR ₂ in the on-vehicle refrigerator are operated alternately. In other words, the switching transistors TR ₁ and TR ₂ were protected against surge voltage caused by electromagnetic induction of the transformer during on/off switching using the circuit configuration shown in FIG. That _is , in FIG. 6, a surge _voltage absorbing element, e.g. Bidirectional varistors 91 and 92 were provided in parallel, and furthermore, bidirectional varistors 27 were provided at both ends of the DC input power source. For example, the surge voltage that appears across the DC input power supply is absorbed by the varistor 27, and the voltage surge generated by the operation of the switching transistors TR ₁ and TR ₂ is applied to the transformer 4.
A surge voltage due to electromagnetic induction, that is, a surge voltage induced in the winding 4-1 of the transformer ₄ caused by turning on and off the transistor TR1, is connected in parallel between the emitter and collector of the transistor _TR1 . It is absorbed by the varistor 91, and the transistor
The surge voltage induced in the winding 4-2 of the transformer 4 caused by turning TR ₂ on and off is absorbed by the varistor 92 connected in parallel between the emitter and collector of the transistor TR ₂ , and Transistors TR ₁ and TR ₂ were previously protected. When an overcurrent flows through the transistors TR ₁ and TR ₂ , the overcurrent detection circuit 14 detects the overcurrent and stops the output Q from the drive circuit 1-3. In addition, in the same figure, 5 is a compressor, 28, 29
is a diode, but since it has no direct relation to the present invention, its explanation will be omitted. Further, the windings 4-1 and 4-2 of the transformer 4 are wound around the same iron core.

(Problems to be Solved by the Invention) In the conventional surge voltage suppression circuit for a vehicle refrigerator shown in FIG. 6, a varistor as a surge voltage absorbing element is provided corresponding to each transistor that performs switching. , 2 with 1 barista
It is desirable to protect the individual switching transistors and reduce the number of components.

The present invention has been made in view of the above points, and
The switching transistor is turned on or off by pulse 1 output from the drive circuit.
By focusing on the fact that when one transistor turns off during a cycle, the other transistor turns on, and by connecting a varistor in a position where both transistors are protected, we have developed an on-vehicle refrigerator that uses fewer parts. The purpose is to provide a surge voltage suppression circuit.

(Means for Solving the Problems) Therefore, the surge voltage suppression circuit for an on-vehicle refrigerator of the present invention is provided in a compressor drive control device that controls the drive of a vibrating compressor using a predetermined frequency corresponding to the load. , a suction refrigerant temperature detector that detects a temperature corresponding to the saturated vapor pressure of the refrigerant sucked by the compressor; and a suction refrigerant temperature detector that detects a temperature corresponding to the saturated vapor pressure of the refrigerant compressed and discharged by the compressor. A discharge refrigerant temperature detector for detecting the temperature, and a drive power generation section for generating a drive power of a predetermined frequency based on temperature signals respectively detected by the suction refrigerant temperature detector and the discharge refrigerant temperature detector. ,
The drive power generation section includes a switching element that operates alternately, a drive circuit that operates the switching element and a predetermined frequency, and a transformer that generates an alternating current voltage by the alternate operation of the switching element. A compressor drive control device for driving and controlling the compressor using the drive power generated by the drive power generation section, wherein the switching element and each winding of the transformer are operated alternately. A surge voltage suppressing element is provided between each connection point with the switching element to suppress the surge voltage generated by electromagnetic induction of the transformer due to the operation of the switching element.

This will be explained below with reference to the drawings.

(Example) Fig. 1 shows the configuration of an embodiment of the surge voltage suppression circuit for an on-vehicle refrigerator according to the present invention, Fig. 2 is a schematic configuration diagram of an on-vehicle refrigerator in which the present invention is used, and Fig. 3 shows the configuration of an on-vehicle refrigerator in which the present invention is applied. 1 shows a circuit configuration of an example of a vehicle-mounted refrigerator in use.

Before explaining the surge voltage suppression circuit for a vehicle-mounted refrigerator according to the present invention, the outline of the vehicle-mounted refrigerator to which the present invention is applied and the circuit configuration in which the present invention is used will be described.

In FIG. 2, 1 is a control circuit, 1-1 is a temperature detection section, 1-2 is a calculation section, 1-3 is a drive circuit, 2 and 3 are temperature detectors, 4 is a transformer, 5 is a compressor, 6 is a condenser, 7 is a pressure reducer, 8 is a refrigerator, 8-
1 represents an evaporator.

In the figure, the control circuit 1 includes a temperature detection section 1-1, a calculation section 1-2, and a drive circuit 1-3, and controls the temperature corresponding to the saturated vapor pressure of the refrigerant sucked by the compressor 5. Temperature detector to detect (T _s )
The compressor 5 is driven in a resonant state based on the respective signals from the temperature detector (T _d ) 3 that detects the temperature corresponding to the saturated vapor pressure of the refrigerant compressed and discharged by the compressor 5. This is to supply a drive signal with a frequency such that Note that the temperature detected by the temperature detection unit 1-1 can be considered to be a temperature that substantially corresponds to the pressure of the refrigerant on the suction side and the pressure of the refrigerant on the discharge side.

The vibrating compressor 5, supplied with drive power generated by the drive signal supplied from the control circuit 1, compresses the refrigerant and supplies a mixture of gas and liquid to the condenser 6. It releases heat and liquefies it. Then, the liquefied refrigerant passes through the pressure reducer 7 and is vaporized in the evaporator 8-1 provided in the refrigerator 8, and removes the heat of vaporization.
It is for cooling. The refrigerant that has absorbed the heat of vaporization is compressed again by the compressor 5. By repeating the above closed cycle, the heat removed from the evaporator 8-1 is released from the condenser 6 in the form of heat. The operation of the control circuit 1 will be described in detail below.

In the figure, a temperature detection section 1-1 is for converting signals detected by temperature detectors (eg, thermistors) 2 and 3 into predetermined electrical signals.

In the figure, the calculation section 1-2 causes the compressor 5 to resonate based on the "temperature corresponding to the suction pressure" and "temperature corresponding to the discharge pressure" converted in the form of electrical signals by the temperature detection section 1-1. The purpose is to generate a voltage corresponding to the frequency of driving in the state. and,
The drive circuit 1-3 supplies a drive signal with a frequency corresponding to the voltage supplied from the arithmetic unit 1-2 to the transistors TR ₁ and TR ₂ in the figure, and supplies the DC power supply Vcc to the primary of the transformer 4. This is for supplying current to the side windings in the form of a so-called rectangular wave in which the polarity is alternately switched to the windings having different polarities. The AC voltage obtained from the secondary winding of the transformer 4 is supplied to the compressor 5, and the compressor 5 is always driven in a resonant state, that is, driven at maximum efficiency.

In the circuit configuration of an embodiment of an on-vehicle refrigerator in which the present invention is used, shown in FIG.
2, 1-3, 2 to 5, TR ₁ and TR ₂ are the same as those shown in FIG. 2, so their explanations will be omitted.

9 is a thermo device, 10 is an evaporator temperature comparator, 11 is a transformer, 12 is an AC detector, 1
3 is a surge absorption circuit, 14 is an overcurrent detection circuit, 1
5 and 16 are relays, 17 and 18 are AND circuits, 1
9, 20 are OR circuits, 21 is an inverter, 22,
23 represents a diode, 24 represents a volume, and 25 represents a shunt.

The thermo device 9 is for setting the indoor temperature of the refrigerator, and the indoor temperature of the refrigerator changes depending on the setting of the volume 24 provided in the thermo device 9.

The evaporator temperature comparator 10 electrically compares the indoor temperature signal of the refrigerator set by the volume 24 with the signal from the temperature detector 2 which detects the temperature of the evaporator 8-1, and When the set temperature on the evaporator 8-1 side becomes higher than the temperature on the evaporator 8-1 side, a logic "L" is output. The output of the logic "L" is an OR circuit 2 with a negative input terminal.
0 to the drive circuit 1-3, and turns off the contact of the relay 16 via the AND circuit _{17 .}
Cut off the DC power supply to the

The transformer 11 is for detecting when the in-vehicle refrigerator is connected to a commercial power source, and drops the voltage of the commercial power source. Supply voltage.

The AC detector 12 detects whether or not commercial power is input, and outputs a logic "H" when the commercial power is input. The logic "H" serves as a stop signal to the drive circuit 1-3 via the OR circuit 20, and also turns off the contact of the relay 16 via the AND circuit 17.
through transformer 4, i.e. transistor
Cut off the DC power supply to TR ₁ and TR ₂ . Further, the contact of the relay 15 is turned on via the AND circuit 18, and AC power is supplied to the transformer 4 via the relay 15.

The surge absorption circuit 13 absorbs the surge voltage of the input DC power supply and supplies the DC power to the drive circuit 1-3, and also outputs a logic "H" when the voltage of the input DC power supply is higher than a predetermined voltage. " is output. The logic "H" is applied to the drive circuits 1-3 via the OR circuit 19 to the transistors TR ₁ ,
The output of TR ₂ is controlled, and the stroke of the compressor 5 is controlled.

The overcurrent detection circuit 14 detects an overcurrent flowing through the transistors TR ₁ and TR ₂ together with the shunt 25. When the overcurrent detection circuit 14 detects an overcurrent, the overcurrent is transmitted to the drive circuit 1-3.
It outputs an output off latch signal that stops the operation of TR ₁ and TR ₂ to prevent damage to transistors TR ₁ and TR ₂ , etc.

Next, the present invention will be further explained using FIG.

In FIG. 1, symbols 1-3, 4, 5, TR ₁ ,
TR ₂ corresponds to that in FIG. 2, 14 corresponds to that in FIG. 3, and 4-1, 4-2, 27 to 29 correspond to that in FIG. 6, which has already been explained. Reference numeral 26 denotes a varistor _, which is an element that absorbs _surge voltage. It is connected between each connection point X and Y.

Now, for example, the switching transistor TR ₁
turns off, winding 4-1 of transformer 4
Due to electromagnetic induction, a surge voltage 2E twice the applied DC input voltage E is generated. On the other hand, when the switching transistor TR ₁ turns off, the switching transistor TR ₁ turns off.
Since the transistor TR2 is turned off, the transistor _TR2 is turned on at the same time as the surge voltage 2E is generated, and the voltage between the node Y and the cathode becomes the saturation voltage _VCE2 of the transistor _TR2 . Therefore, the surge voltage caused by turning off transistor TR ₁ is transferred to varistor 26 and transistor TR ₂ .
A current flows through the varistor 26, and if the voltage of the varistor 26 at this time is V ₀ , the voltage between the connection point X and the cathode is V ₀
+V _CE2 , and the voltage V ₀ +V _CE2 is applied between the emitter and collector of the turned-off transistor _TR1 . That is, V ₀ , V _CE2
Since the value of is small and E>V ₀ +V _CE2 , the surge voltage applied to the turned-off transistor TR ₁ is suppressed.

Conversely, exactly the same thing occurs when transistor TR ₂ is turned off. Also transistor
When TR ₁ and TR ₂ are turned on, E + V ₀ +
In some cases, _a voltage of V _CE is applied, but as explained above, since V ₀ +V _CE is a small value, each transistor TR ₁ and TR _{2 is} protected from destruction.

Note that it is considered that the varistor 26 is omitted and only the varistor 27 is provided, and the on-voltage of the varistor 27 is set low to protect the transistors TR ₁ and TR ₂ . However, in this case, the current flowing through the varistor 27 becomes extremely large, which is not practical. By providing the varistor 26 as described above, the on-voltage of the varistor 27 can be set high. The protection against surge voltages described above is also effective against surges from an AC power source during AC drive.

〔Effect of the invention〕

As described above, according to the present invention, the number of varistors used to protect switching transistors can be reduced, and the transistors can be sufficiently protected.

[Brief explanation of the drawing]

FIG. 1 shows the configuration of an embodiment of a surge voltage suppression circuit for an on-vehicle refrigerator according to the present invention, FIG. 2 is a schematic configuration diagram of an on-vehicle refrigerator in which the present invention is used, and FIG. 3 shows an example in which the present invention is used. 4 is an explanatory diagram illustrating a conventional compressor drive control system; FIG. 5 is an operation explanatory diagram illustrating the operation of the compressor drive control system shown in FIG. 4; FIG. 6 shows a conventional surge voltage suppression circuit for an on-vehicle refrigerator. In the figure, 1 is a control circuit, 1-1 is a temperature detection section, 1
-2 is the calculation unit, 1-3 is the drive circuit, 2 and 3 are the temperature detectors, 4 is the transformer, 4-1 and 4-2 are the windings, 5 is the compressor, 6 is the condenser, and 7 is the pressure reduction 8 represents a refrigerator, 8-1 represents an evaporator, and 26 and 27 represent a varistor.

Claims (1)

[Claims] 1. In a compressor drive control device that drives and controls a vibrating compressor using a predetermined frequency corresponding to the load, a suction refrigerant that detects a temperature corresponding to the saturated vapor pressure of the refrigerant sucked by the compressor. a temperature detector; a discharge refrigerant temperature detector that detects a temperature corresponding to the saturated vapor pressure of the refrigerant compressed and discharged by the compressor; and the suction refrigerant temperature detector and the discharge refrigerant temperature detector. and a drive power generation section that generates a drive power source of a predetermined frequency based on the temperature signal detected respectively, and the drive power generation section includes a switching element that operates alternately, and a switching element that operates the switching element at a predetermined frequency. and a transformer that generates an alternating current voltage by alternately operating the switching elements, and drives the compressor using the drive power generated by the drive power generation section. A compressor drive control device for controlling a compressor, wherein a surge voltage suppressing element is provided between each connection point between the switching element that operates alternately and each winding of the transformer, A surge voltage suppression circuit for an on-vehicle refrigerator, characterized in that it suppresses surge voltage caused by electromagnetic induction.