GB2316819A - Over temperature protection for a power amplifier - Google Patents

Over temperature protection for a power amplifier Download PDF

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Publication number
GB2316819A
GB2316819A GB9618141A GB9618141A GB2316819A GB 2316819 A GB2316819 A GB 2316819A GB 9618141 A GB9618141 A GB 9618141A GB 9618141 A GB9618141 A GB 9618141A GB 2316819 A GB2316819 A GB 2316819A
Authority
GB
United Kingdom
Prior art keywords
temperature
power amplifier
sensing
radio frequency
frequency power
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9618141A
Other versions
GB9618141D0 (en
Inventor
Christopher Warren Wright
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Motorola Solutions UK Ltd
Original Assignee
Motorola Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Motorola Ltd filed Critical Motorola Ltd
Priority to GB9618141A priority Critical patent/GB2316819A/en
Publication of GB9618141D0 publication Critical patent/GB9618141D0/en
Publication of GB2316819A publication Critical patent/GB2316819A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/52—Circuit arrangements for protecting such amplifiers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)

Abstract

A radio frequency power amplifier is provided with at least one device 21, 23, 29 for sensing the temperature of at least one predetermined area 20, 22, 28 of the power amplifier and comparing 30 the sensed temperature with a reference 32. Detection of an over temperature may cause the disconnection of the power supply to the amplifier and may be implemented by using a crowbar effect 34. It may be made necessary to remove the power supply to the amplifier and replace it in order to reset the protection device.

Description

POWER AMPLIFIER AND METHOD THEREFOR Field of the Invention This invention relates to a radio frequency power amplifier and a method therefor. Specifically, this invention relates to a power amplifier having a temperature sensing device and a method for sensing a temperature of a power amplifier.
Background of the Invention Intrinsically safe (IS) equipment is classified in different temperature groups. Such temperature groups are defined by the maximum temperature attained in the event of a fault and dissipation of maximum power. High power modules such as Radio Frequency (RF) power amplifiers usually are capable of dissipating too much power to allow a reasonable temperature classification without special measures.
FIG. 1 shows a block diagram of a typical radio frequency power amplifier. Such a typical power amplifier module includes a driver circuit 10, followed by an RF output transistor 12. The RF output 14 is connected to an antenna. The module derives its power from a power supply 16, such as a 7v/lA source. Should the output device, Qx, fail in a low resistance state, the module will dissipate around 7W which will result in a large rise in temperature. The situation will be similar in the event of the failure of the driver 10 but the situation may be compounded by the regulating transistors of a control circuit 18. Thus, in case of a fault the module will most certainly exceed the permitted temperatures and will not be intrinsically safe.
Historically, the problem usually has been solved by encapsulation of a power amplifier module with a special compound to exclude the potentially explosive gas from contact with very hot components and to spread heat more evenly so that exposed surfaces of the module remain below a specified threshold. Such encapsulation is difficult, messy and expensive. Furthermore, the encapsulation process is difficult to control and is not appreciated by manufacturing. Thus, there is a need to make power amplifiers intrinsically safe without encapsulation.
Summarv of the Invention According to the present invention, a radio frequency power amplifier is provided comprising a temperature sensing device for sensing the temperature in predetermined areas in the power amplifier; and a comparator for comparing the temperature with a reference.
An alternative body of the present invention includes a method of sensing the temperature of a radio frequency power amplifier including the steps of sensing a temperature at a least one predetermined area of the power amplifier; and comparing the sensed temperature of the at least one predetermined area with a referenced temperature.
A preferred embodiment of the invention is now described, by way of example only, with reference to the drawings.
Brief Description of Drawings FIG. 1 is a block diagram of a radio frequency power amplifier according to the prior art.
FIG. 2 is a block diagram of a radio frequency power amplifier according to an embodiment of the invention.
FIG. 3 is a flowchart according to a further embodiment of the present invention.
Detailed Description of the Drawings FIG. 2 shows a radio frequency power amplifier having at least one temperature sensing device 21, 23, 29 for sensing the temperature in predetermined areas 20, 22, 28 in the power amplifier and a comparator 30 for comparing the temperature with a reference 32. The radio frequency power amplifier of FIG. 2 further includes a tripping device 34 that shuts down the power amplifier if the temperature is greater than the reference.
The tripping device (or crowbar) 34 may be a transistor.
The radio frequency power amplifier of FIG. 2 operates having a control circuit 28, a driver circuit 20, and an output circuit 22.
Furthermore, the power amplifier includes a first temperature sensing device 29 for sensing a first temperature in the control circuit 28, a second temperature sensing device 21 for sensing a second temperature in the driver circuit 20, a third temperature sensing device 23 for sensing a third temperature in the output circuit 22. In fact, any variation of number of temperature sensing devices may be used to measure predetermined areas of the circuit as needed.
The power amplifier of the present invention further includes a comparator 30 for comparing a reference temperature 32 with the first, second and third temperatures. The reference temperature 32 may be chosen as the maximum temperature that is acceptable to operate under in order to be intrinsically safe.
The tripping device (or crowbar) 32 operates to shuts down the power amplifier if the first, second or third temperature is greater than the reference temperature. The comparator 30 trips the crowbar 32 which shorts the battery supply 26. The battery may be a 7v supply. A regulator circuit in the battery senses the over current and shuts down. The battery supply cannot be reset unless the battery is removed from the radio.
The temperature sensors must be fault tolerant. Film-type thermistors may be used, and may be such that only a single sensor is needed per circuit. The sensors may be leaded devices glued to the tops of the transistors or IC package, or depending on the package style, could be incorporated in the multilayer pcb below the power device.
Semiconducting sensors, diodes, for example, could be redundant, requiring a pair of devices per circuit but such could be integrated into a power device package. The crowbar may or may not be redundant since it is normally off. It must, however, withstand the current transient but, because of transient operation, physically could be quite small.
FIG. 3 shows a method of operating a power amplifier according to an embodiment of the present invention. Such a method could be used to sense the temperature of a radio frequency power amplifier and determine if it is operating at an intrinsically safe temperature.
Referring to FIG. 3, when the power amplifier is operating, temperature sensors are used to sense a temperature at least one predetermined area of the power amplifier, step 40. The sensed temperature is then compared, in step 42, with a referenced temperature.
If the sensed temperature is less than the reference temperature, as determined in step 42, then the sensor continues to monitor the temperature returning back to step 40.
If the sensed temperature is greater than the reference temperature, as determined in step 42, the power amplifier may be shut down, step 44.
The power amplifier circuit may be restarted by removing and replacing a power source to the power amplifier as in step 46.
The present invention may include a number of temperature sensors strategically placed in a number of areas of the power amplifier circuit in order to monitor the temperature of particular predetermined areas. The reference temperature may be easily changed as needed and with only a small effect on the power amplifier circuit itself. Thus, the present invention may permit higher temperature classification for certain power amplifiers.
The present invention eliminates the need for encapsulating the power amplifier module, thus makes available space above the device typically used up by encapsulation. Most importantly, the present invention avoids potentially explosive situations by shutting down the device when the temperature gets too high in particular areas. Thus, the present invention provides an intrinsically safe radio frequency power amplifier

Claims (8)

  1. Claims 1. A radio frequency power amplifier comprising: a temperature sensing device for sensing the temperature in predetermined areas in the power amplifier; and a comparator for comparing the temperature with a reference.
  2. 2. The radio frequency power amplifier of claim 1 further comprising a tripping device that shuts down the power amplifier if the temperature is greater than the reference.
  3. 3. A radio frequency power amplifier having a control circuit, a driver circuit, and an output circuit, the power amplifier comprising: a first temperature sensing device for sensing a first temperature in the control circuit; a second temperature sensing device for sensing a second temperature in the driver circuit; a third temperature sensing device for sensing a third temperature in the output circuit; and a comparator for comparing a reference temperature with the first, second and third temperatures.
  4. 4. The radio frequency power amplifier of claim 2 further comprising a tripping device that shuts down the power amplifier if the first, second or third temperature is greater than the reference temperature.
  5. 5. A method of sensing the temperature of a radio frequency power amplifier comprising the steps of: sensing a temperature at a least one predetermined area of the power amplifier; and comparing the sensed temperature of the at least one predetermined area with a referenced temperature.
  6. 6. The method of claim 5 further comprising the step of: shutting down the power amplifier circuit if the sensed temperature of the at least one predetermined area is greater than the reference temperature.
  7. 7. The method of claim 6 further comprising the step of: restarting the power amplifier by removing and replacing a power source to the power amplifier.
  8. 8. A radio frequency power amplifier substantially as described herein with reference to FIG. 2 of the drawings.
GB9618141A 1996-08-30 1996-08-30 Over temperature protection for a power amplifier Withdrawn GB2316819A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9618141A GB2316819A (en) 1996-08-30 1996-08-30 Over temperature protection for a power amplifier

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9618141A GB2316819A (en) 1996-08-30 1996-08-30 Over temperature protection for a power amplifier

Publications (2)

Publication Number Publication Date
GB9618141D0 GB9618141D0 (en) 1996-10-09
GB2316819A true GB2316819A (en) 1998-03-04

Family

ID=10799183

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9618141A Withdrawn GB2316819A (en) 1996-08-30 1996-08-30 Over temperature protection for a power amplifier

Country Status (1)

Country Link
GB (1) GB2316819A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2336509A (en) * 1998-04-06 1999-10-20 Nec Corp Preventing overheating of portable telephone by calculating temperature expected after transmission
WO2006079941A1 (en) * 2005-01-25 2006-08-03 Nxp B.V. Synchronized temperature protection for class-ab amplifiers

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1602364A (en) * 1977-03-02 1981-11-11 Bosch Gmbh Robert Apparatus for the protection of an electrical installation
GB2157104A (en) * 1982-11-09 1985-10-16 Ericsson Telefon Ab L M Monitoring device for drive amplifiers
US5159520A (en) * 1990-08-03 1992-10-27 Sharp Kabushiki Kaisha Semiconductor integrated circuit having function of preventing rise of surface temperature
US5198956A (en) * 1992-06-19 1993-03-30 Square D Company Overtemperature sensing and signaling circuit
US5291387A (en) * 1991-03-13 1994-03-01 Nec Corporation Switching voltage regulator with protective device against thermal breakdown

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1602364A (en) * 1977-03-02 1981-11-11 Bosch Gmbh Robert Apparatus for the protection of an electrical installation
GB2157104A (en) * 1982-11-09 1985-10-16 Ericsson Telefon Ab L M Monitoring device for drive amplifiers
US5159520A (en) * 1990-08-03 1992-10-27 Sharp Kabushiki Kaisha Semiconductor integrated circuit having function of preventing rise of surface temperature
US5291387A (en) * 1991-03-13 1994-03-01 Nec Corporation Switching voltage regulator with protective device against thermal breakdown
US5198956A (en) * 1992-06-19 1993-03-30 Square D Company Overtemperature sensing and signaling circuit

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2336509A (en) * 1998-04-06 1999-10-20 Nec Corp Preventing overheating of portable telephone by calculating temperature expected after transmission
GB2336509B (en) * 1998-04-06 2003-01-15 Nec Corp Method and apparatus for preventing overheating of a portable telephone
WO2006079941A1 (en) * 2005-01-25 2006-08-03 Nxp B.V. Synchronized temperature protection for class-ab amplifiers
US7948320B2 (en) 2005-01-25 2011-05-24 Nxp B.V. Synchronized temperature protection for class-AB amplifiers

Also Published As

Publication number Publication date
GB9618141D0 (en) 1996-10-09

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)