Thermal measuring and testing – Temperature measurement – Combined with diverse art device
Reexamination Certificate
1999-09-17
2001-09-11
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
Combined with diverse art device
C374S178000, C327S512000
Reexamination Certificate
active
06286996
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a method and to an arrangement for measuring temperature in a semiconductor component.
BACKGROUND OF THE INVENTION
The radio transmitter is an important part of, for example mobile telephony systems. A transmitter in radio communications equipment will comprise, among other things, a power amplifier in which transistors are included. A transistor will generate heat at high powers. Typical problems that may occur are overheating and parameter changes. Overheating can damage the transistor and render it totally unserviceable. A change in temperature can change the parameters of the transistor and result in interferences. To prevent overheating, and therewith transistor damage, or parameter changes and therewith interferences, it is important that the transistor junction temperature can be measured correctly. When the temperature of a transistor is known, damage can be prevented or compensation made for any parameter changes that may occur. This is important and often essential in systems in which high performance is required. Mobile telephone systems are examples of such systems.
One typical method of measuring the temperature of a power transistor is to place a temperature sensor in the proximity of the heat-conducting outer casing of the transistor, for instance on a cooling fin. This method is unsatisfactory in many cases, since it is then the temperature of the outer casing that is measured rather than the junction temperature of the transistor. The measured values are therewith thermally delayed as a result of the physical distance between the active transistor parts and the temperature sensor. The temperature measurement is also misleading, since the temperature value decreases with the distance between the transistor and the temperature sensor. There is a danger that a sudden increase in temperature will not be measured until it is too late, in other words until the transistor has already been damaged. To prevent this, it is necessary to introduce large safety margins, which, in turn, increases costs. Other methods of measuring the temperature of a transistor are known to the art. U.S. Pat. No. 5,383,083 describes how the temperature of a transistor is measured by connecting a measuring circuit to the transistor base and registering the voltage across the base-emitter of the transistor, and converting the measurement to a temperature value. One drawback with this technique is that normal transistor operation will disturb the temperature measuring process, or vice versa that the measuring process will disturb the normal operation of the transistor.
SUMMARY OF THE INVENTION
The present invention addresses the problem of enabling the junction temperature of an intermittently operating semiconductor component, for instance a transistor, to be measured correctly without interference between the measuring process and transistor operation.
This problem is solved in accordance with the invention, by waiting for a pause in the actual work carried out by the semiconductor component. The temperature is then measured when the component is in its inactive state.
More specifically, when the semiconductor component is a bipolar transistor the problem is solved by forming the temperature sensor from a part of the transistor and by supplying the transistor base with a known current that is kept constant during the temperature measuring process. An inactive period is detected, i.e. a pause in normal transistor operation, for instance a pause between transmissions in a radio transmitter. According to the invention, a measuring circuit is connected to the semiconductor component, for example to the base of the transistor, during this pause in transmission. The measuring circuit measures the base-emitter voltage and the voltage is then converted to a temperature value that corresponds to the transistor temperature when correctly calibrated.
Another problem addressed by the invention is one of measuring the temperature of a semiconductor component without needing to pay attention to thermal delay.
This problem is solved in accordance with the invention by forming the temperature sensor from a part of the semiconductor component.
One object of the present invention is to prevent the normal operation of a semiconductor component from being disturbed by the temperature measuring process.
Another object of the invention is to prevent the signals obtained with the temperature measuring process from being drowned in the signalling occurring in a normally operating semiconductor component.
Still another object of the invention is to prevent a thermal delay in the temperature measuring process from resulting in an erroneous measurement, therewith requiring margins to be employed by expensive over-dimensioning in respect of cooling the semiconductor component, its power durability or temperature durability.
Another object of the invention is to enable the effects of the temperature change to be corrected in good time before the fault occurs. This correction may, for instance, comprise increased cooling of the semiconductor component.
Yet another object of the invention is to compensate for variations in the modus operandi caused by temperature change. Compensation may, for instance, consist of changing the operating or working point of the semiconductor component to the value that existed prior to the change in temperature. Thus, one advantage afforded by the invention is that the temperature measuring process and operation of the semiconductor component will not interfere with one another.
Another advantage is that the measurement result will be correct, which results in low costs.
The invention will now be described in more detail with reference to exemplifying embodiments thereof and also with reference to the accompanying drawings.
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Burns Doane Swecker & Mathis L.L.P.
Gutierrez Diego
Pruchnic Jr. Stanley J.
Telefonaktiebolaget LM Ericsson (publ)
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