JP2518042B2 - Semiconductor element temperature detection circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a circuit for detecting a junction temperature of a semiconductor switch element that constitutes a power conversion device.

[Conventional technology]

FIG. 4 is a general main circuit connection diagram of an inverter configured by combining semiconductor elements.

In FIG. 4, a gate turn-off thyristor (hereinafter abbreviated as GTO thyristor) 4 as a semiconductor element and a freewheeling diode 5 connected in antiparallel are shown in FIG.
Inverter 3
Is formed. It is well known that the DC power from the DC power supply 2 is converted into AC power by sequentially turning on / off the four GTO thyristors 4 in response to a command from a control device (not shown), and power can be supplied to the load 6. is there.

The GTO thyristor 4 used here is a self-extinguishing type semiconductor device that is capable of conducting and interrupting the main current by gate control. To obtain the characteristics specified in the rating, the specified junction temperature range is used. Must be used within. Further, the GTO thyristor 4, like other semiconductor elements, causes a loss due to the flow of a current, and also causes a large loss at a transient time of ignition and extinguishing although it is a short time.
Therefore, in order to keep the temperature rise due to these generated losses within the range of the above-mentioned determined junction temperature, some cooling device is required.

FIG. 5 is a block diagram showing a cooling system of a known GTO thyristor.

In FIG. 5, a flat structure which is frequently used for a large capacity semiconductor device is shown as an example. That is, the anode side cooling body 7 is directly connected to the anode electrode A of the GTO thyristor 4, and the cathode side cooling body 8 is directly connected to the cathode electrode K. By blowing cooling air in the arrow direction,
The loss generated in the GTO thyristor 4 is dissipated to the surrounding atmosphere via the cooling bodies 7 and 8. In addition,
Reference numeral 9 is a temperature detector such as a thermostat.

By the way, in the case of a device in which the power of the load 6 is constant or the operation method is predetermined in the inverter 3 as shown in FIG. 4, the maximum generated loss of this GTO thyristor 4 is at the time of designing the device. Since it is known in advance, the cooling system may be designed so that the temperature rise of the GTO thyristor 4 due to the loss is within the allowable value.

However, in a device in which an arbitrary load is connected and the operating method changes significantly depending on the load, the current flowing through the GTO thyristor 4 changes significantly, and in this case, the maximum expected loss can be expected. However, if the cooling system is designed so as to be able to deal with a large loss that rarely comes, the cost will increase and it will be an uneconomical device.

Therefore, in such a case, design a cooling system corresponding to the load that is normally used, and detect an abnormal temperature rise in the GTO thyristor 4 during abnormal conditions such as excessive load or erroneous operation. It is more economical to stop the device by using

FIG. 6 is a view showing a joint surface between the cathode electrode and the cathode side cooling body of the GTO thyristor in the configuration diagram shown in FIG.

As shown in FIG. 6, in the cathode side cooling body 8,
A thermostat 9 is attached together with the GTO thyristor 4 to monitor the case temperature of the GTO thyristor 4. That is, when the GTO thyristor 4 becomes overloaded for some reason and the junction temperature of the GTO thyristor 4 rises to a value that cannot withstand normal operation, the case temperature also rises accordingly. An abnormal temperature rise is detected and an alarm is issued, or the operation of the device is stopped.

[Problems to be Solved by the Invention]

However, the above-mentioned conventional temperature detection method has some drawbacks as described above. That is, the first problem is that when the cooling bodies 7 and 8 as shown in FIG. 5 are used, the thermostat 9 has a place to be attached only to the fin portions of the cooling bodies 7 and 8, and the GTO thyristor 4 has Since the distance from the case becomes long and the temperature of the GTO thyristor 4 cannot be monitored accurately, reliable protection was difficult. Second
The problem is that when a large pulsed load is applied for a time shorter than the thermal time constant of the cooling bodies 7 and 8 of the GTO thyristor 4,
Since there is a time lag between the actual junction temperature of the GTO thyristor 4 and the temperature at the thermostat 9 mounting position shown in FIG. 5, accurate temperature monitoring cannot be performed, and therefore reliable protection is required. It was difficult to do.

Due to the above two problems, the GTO thyristor 4 cannot be effectively used up to its temperature limit,
As a result, the size of the device becomes large and the cost becomes high.

Therefore, an object of the present invention is to reliably protect the semiconductor element by accurately and quickly detecting the junction temperature of the semiconductor element attached with a cooling body that dissipates the generated loss.

[Means for solving the problem]

In order to achieve the above object, the temperature detection circuit of the present invention is a device including a semiconductor element that performs power conversion and a cooling body that dissipates the loss generated in the semiconductor element. Turn-on loss calculation means for calculating the turn-on loss of the semiconductor element by inputting the loss characteristic, the current flowing through the semiconductor element, and the anode-cathode voltage, and the loss characteristic and the flowing current and A turn-off loss calculating means for calculating the turn-off loss of the semiconductor element by inputting the voltage between the anode and the cathode, and the above-mentioned loss characteristic and the flowing current are input to calculate the steady-state loss of the semiconductor element. Steady loss calculation means, addition means for adding the turn-on loss, turn-off loss, and steady-state loss, and the addition calculation result Shall and a junction temperature calculating means for calculating a junction temperature of the semiconductor element.

[Action]

According to the present invention, the instantaneous value of the junction temperature of the semiconductor element is calculated from the loss characteristics of the semiconductor element and the characteristics of the cooling system which are obtained in advance, and the actual values of the current flowing through the semiconductor element and the voltage between the anode and the cathode. By performing the calculation, the accurate junction temperature can be quickly grasped in both the steady state and the transient state, so that reliable protection is performed.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention.

The GTO thyristor 4 as a semiconductor element forming the inverter 3 shown in FIG. 4 converts electric power by an on / off operation. At this time, the GTO thyristor 4 loses power in an off state. Is divided into a turn-on loss that occurs when shifting from the ON state to the ON state, a steady loss that occurs during steady operation in the ON state, and a turn-off loss that occurs when shifting from the ON state to the OFF state.

In FIG. 1, reference numeral 11 denotes a turn-on loss calculation circuit that calculates a loss when the GTO thyristor 4 is turned on. Based on the characteristic data of the GTO thyristor 4 given in advance, the anode current I _A and the anode
The relationship between the turn-on loss and the voltage V _AK between the cathodes is stored, and the anode current I _A of this GTO thyristor 4 is stored.
It also has a function to output turn-on loss corresponding to the anode-cathode voltage V _AK .

Reference numeral 12 denotes a turn-off loss calculation circuit that calculates a loss at the time of turn-off of the GTO thyristor 4, and based on the characteristic data of the GTO thyristor 4 given in advance, the anode current I _A and the anode-cathode voltage V _AK flowing through the characteristic data.
Remember the relationship of turn-off loss to
The GTO thyristor 4 has a function of outputting turn-off loss corresponding to the anode current I _A and the anode-cathode voltage V _AK .

Reference numeral 13 is a steady loss calculation circuit for calculating the loss of the GTO thyristor 4 in a steady state. Based on the specific data of the GTO thyristor 4 given in advance, the anode current flowing through this
Remember the relationship of steady loss to I _A ,
It has a function of outputting a steady loss corresponding to the anode current I _A of the thyristor 4.

Reference numeral 14 denotes an adder, which adds the losses calculated by the turn-on loss calculation circuit 11, the turn-off loss calculation circuit 12, and the steady-state loss calculation circuit 13 to each other.
The total loss that occurs when the GTO thyristor 4 turns on and off is calculated.

Reference numeral 15 is a junction temperature calculation circuit for calculating the junction temperature of the GTO thyristor 4 from the generated loss of the GTO thyristor 4 calculated by the adder 14, which has a time constant equal to the thermal time constant of the cooling system. It is composed of a second-delay filter, the output of which corresponds to the junction temperature of the GTO thyristor 4.

Reference numeral 16 is a comparator for detecting that the junction temperature of the GTO thyristor 4 obtained as the output of the junction temperature calculation circuit 15 has reached the maximum operable value.
This is the maximum operable value of the junction temperature of the GTO thyristor 4 preset in the comparator 16 and the actual value of the junction temperature of the GTO thyristor 4 obtained as the output of the junction temperature calculation circuit 15. In comparison, when the actual temperature value exceeds the above-mentioned set value, the output logic signal is inverted. Therefore, if the GTO thyristor 4 becomes overloaded and the logic output of the comparator 16 is inverted, the protection circuit (not shown) immediately stops the operation of the device and may damage it due to overload. Is being prevented.

Figure 2 shows the anode current I flowing through the GTO thyristor.
FIG. 7 is a diagram showing _A and an anode-cathode voltage V _AK .

FIG. 3 is a waveform diagram showing the timing at which the GTO thyristor causes a loss, and FIG. 3 (a) is the anode current I _A of the GTO thyristor and the anode-cathode voltage V _AK.
Fig. 3 (b) shows the changes over time in the loss generated in the GTO thyristor.

In FIG. 3, T ₁ is the time when the GTO thyristor 4 in the off state starts to turn on, T ₂ is the time when the turn on is completed, T ₃ is the time when the GTO thyristor 4 in the on state starts to turn off, and T ₄ is At the end of turn-off.
Therefore, the period during which T ₁ to T ₂ causes turn-on loss,
The period from T ₂ to T ₃ is the steady loss, and from T ₃
Until T ₄ is a period for generating the turn-off loss.

〔The invention's effect〕

According to the present invention, the loss that occurs when the semiconductor element is turned on, the loss that occurs when the semiconductor element turns off, and the loss that occurs during steady operation are the flow rates of the characteristic data unique to the semiconductor element. Since the circuit is configured so that it can be calculated separately from the anode current value and the anode-cathode voltage value, and the instantaneous value of the junction temperature of the semiconductor element can be calculated from the sum of these losses,
When detecting the junction temperature from the time when the loss occurs, the time delay of the detection, which was present in the conventional method, is eliminated. Therefore, the temperature can be accurately detected immediately even for a pulsed load for a period shorter than the thermal time constant of the cooling body, so that the rating of the semiconductor element is cut down and used, or a large cooling body is used. It is possible to eliminate the waste of waste and reduce the size of the device.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
The figure shows the anode current I _A flowing through the GTO thyristor and the anode-cathode voltage V _AK . Figure 3 is the waveform diagram showing the timing at which the GTO thyristor generates loss. A general main circuit connection diagram of an inverter formed by combining elements, FIG. 5 is a configuration diagram showing a cooling system of a known GTO thyristor, and FIG. 6 is a cathode electrode of the GTO thyristor in the configuration diagram shown in FIG. It is a figure showing the joint surface of the cathode side cooling body. 2 ... DC power supply, 3 ... Inverter, 4 ... GTO thyristor as semiconductor element, 5 ... Reflux diode, 6 ...
… Load, 7 …… Anode side cooling body, 8 …… Cathode side cooling body, 9 …… Thermostat, 11 …… Turn-on loss calculation circuit, 12 …… Turn-off loss calculation circuit, 13 …… Steady loss calculation circuit, 14… … Adder, 15 …… Junction temperature calculation circuit, 16 …… Comparator.

Claims (2)

(57) [Claims] 1. A device comprising a semiconductor element that performs power conversion and a cooling body that dissipates the loss generated in the semiconductor element, and a loss characteristic of the semiconductor element and a current flowing through the semiconductor element. , And an anode-cathode voltage are input to calculate a turn-on loss of the semiconductor element, and the loss characteristics, the conduction current, and the anode-cathode voltage are input, and Turn-off loss calculation means for calculating the turn-off loss of the semiconductor element, steady-state calculation means for calculating the steady-state loss of the semiconductor element by inputting the above-mentioned loss characteristics and flowing current, and these turn-on loss and turn-off loss Loss, and addition means for adding the loss at steady state, and a junction temperature for calculating the junction temperature of the semiconductor element from the addition operation result. Temperature detection circuit of the semiconductor element characterized in that it comprises a calculating means. 2. The temperature detecting circuit according to claim 1, wherein the junction temperature calculating means is a first-order lag filter having a time constant equal to a thermal time constant between the semiconductor element and its cooling body. A temperature detecting circuit for a semiconductor device, which is characterized in that it is configured.