Automatic voltage limiting circuit capable of sensing temperature

Abstract

The utility model discloses an automatic voltage limiting circuit capable of sensing temperature, and relates to the technical field of power amplification, in particular to the automatic voltage limiting circuit capable of sensing temperature, which comprises a comparison control module, a switch control module and a power limiting module, the comparison control module comprises a thermistor and a first operational amplifier unit; the thermistor is arranged on the transformer; two input ends of the first operational amplifier unit are respectively connected with a positive reference voltage and a thermistor; the switch control module comprises a first switch unit, the first switch unit comprises a first triode, the base electrode of the first triode is connected with the output end of the first operational amplifier unit, and the collector electrode is connected with positive reference voltage; the power limiting module comprises a transconductance operational amplifier chip, and the current bias input end of the transconductance operational amplifier chip is connected with the output end of the switch control module; the inverted input end and the non-buffering output end of the transconductance operational amplifier chip are connected with the AND output module, and the output power can be dynamically adjusted to enable the temperature of the amplifier transformer to be recovered to a safe working range.

Description

Technical Field

[0001] The utility model relates to the technical field of power amplification, in particular to an induction temperature automatic voltage limiting circuit. Background Art

[0002] In view of the different environments and places during the use of current audio broadcast power amplifiers, some power amplifiers are used in very harsh environments and have very high requirements for power amplifiers. Among them, the power amplifier fails due to continuously high temperature. In the existing protection circuits, the traditional method of the power amplifier power limiting circuit is to perform power limiting processing on the peak power, and does not perform real-time detection on the temperature rise of the transformer. After the power amplifier output is overloaded or the transformer works for a long time, the temperature is very high, which is a great potential danger invisibly (the transformer is burned due to too high temperature rise); moreover, when the temperature is detected to be too high, the power supply will be directly switched, which is not flexible enough in adjustment and will seriously affect the user experience. Summary of the Utility Model

[0003] The purpose of the utility model is to avoid the deficiencies in the prior art and provide a technology that can adjust the temperature of the transformer to work within a safe range and reduce the operation failure rate.

[0004] The purpose of the utility model is achieved by the following technical solutions:

[0005] An induction temperature automatic voltage limiting circuit includes: a comparison control module, a switch control module, and a power limiting module; the switch control module is separately connected to the comparison control module and the power limiting module; the comparison control module includes a thermistor and a first operational amplifier unit; the thermistor is arranged on the transformer; two input ends of the first operational amplifier unit are respectively connected to a positive reference voltage and the thermistor; the switch control module includes a first switch unit, the first switch unit includes a first triode, the base of the first triode is connected to the output end of the first operational amplifier unit, and the collector is connected with a positive reference voltage; the power limiting module includes a transconductance operational amplifier chip, and the current bias input end of the transconductance operational amplifier chip is connected to the output end of the switch control module; the inverting input end and the bufferless output end of the transconductance operational amplifier chip are connected to the output module.

[0006] Specifically, the first switch unit further includes a first diode, a first resistor, and a second resistor; one end of the first diode is connected to the output end of the first operational amplifier unit, and the other end is connected to the base of the first triode through the first resistor; the collector of the first triode is connected to the second resistor, and the emitter is grounded.

[0007] Specifically, the switch control module further includes a second switch unit; the second switch unit includes a second triode, a second diode, and a third resistor; the base of the second triode is grounded, the collector is connected to one end of the second diode, and the emitter is connected to the emitter of the first triode through the third resistor; the other end of the second diode is connected to the current bias input terminal of the transconductance operational amplifier chip.

[0008] Specifically, the comparison control module further includes a first voltage dividing resistor, a second voltage dividing resistor, and a third voltage dividing resistor; one end of the first voltage dividing resistor is grounded, and the other end is connected to one end of the third voltage dividing resistor; one end of the second voltage dividing resistor is connected to a positive reference voltage, and the other end is connected to one end of the third voltage dividing resistor; the other end of the third voltage dividing resistor is connected to the negative phase input terminal of the first operational amplifier unit.

[0009] Furthermore, the power limit module further includes a fourth voltage dividing resistor and a fifth voltage dividing resistor; one end of the fourth voltage dividing resistor is connected to a negative reference voltage, and the other end is connected to one end of the fifth voltage dividing resistor; the other end of the fifth voltage dividing resistor is connected to the current bias input terminal of the transconductance operational amplifier chip.

[0010] Furthermore, the output module includes a second operational amplifier unit; the positive phase input terminal of the second operational amplifier unit is connected to the input module; the inverting input terminal and the bufferless output terminal of the transconductance operational amplifier chip are respectively connected to the negative phase input terminal and the positive phase input terminal of the second operational amplifier unit.

[0011] Furthermore, the power limit module further includes a sixth voltage dividing resistor and a seventh voltage dividing resistor; the inverting input terminal of the transconductance operational amplifier chip is connected to the negative phase input terminal of the second operational amplifier unit through the sixth voltage dividing resistor, and at the same time, the inverting input terminal of the transconductance operational amplifier chip is grounded through the seventh voltage dividing resistor.

[0012] Specifically, the input module includes a third operational amplifier unit, the negative phase input terminal and the positive phase input terminal of the third operational amplifier unit are used to access a balanced signal, and the output terminal is connected to the positive phase input terminal of the second operational amplifier unit.

[0013] Specifically, the transconductance operational amplifier chip uses an operational amplifier chip with the model LM13700M.

[0014] Specifically, the thermistor is arranged on the secondary winding coil of the transformer.

[0015] Beneficial effects achieved by the present utility model: An induction temperature automatic voltage limiting circuit, comprising: a comparison control module, a switch control module, and a power limiting module; the switch control module is separately connected to the comparison control module and the power limiting module; the comparison control module includes a thermistor and a first operational amplifier unit; the thermistor is disposed on the transformer; two input ends of the first operational amplifier unit are respectively connected to a positive reference voltage and the thermistor; the switch control module includes a first switch unit, the first switch unit includes a first triode, a base of the first triode is connected to an output end of the first operational amplifier unit, and a collector is connected to a positive reference voltage; the power limiting module includes a transconductance operational amplifier chip, a current bias input end of the transconductance operational amplifier chip is connected to an output end of the switch control module; an inverting input end and a bufferless output end of the transconductance operational amplifier chip are connected to an output module, and the output power can be dynamically adjusted to restore the temperature of the transformer to a safe operating range. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following will briefly introduce the drawings required for description in the embodiments. Obviously, the drawings in the following description are some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic block diagram of the principle of an induction temperature automatic voltage limiting circuit according to an embodiment of the present utility model;

[0018] Figure 2 It is a schematic circuit diagram of an induction temperature automatic voltage limiting circuit according to an embodiment of the present utility model;

[0019] Figure 3 It is a schematic diagram of the internal circuit principle of a transconductance operational amplifier chip of an induction temperature automatic voltage limiting circuit according to an embodiment of the present utility model. Detailed Embodiments

[0020] To make the objectives, technical solutions, and advantages of the present utility model clearer, the following will, with reference to the drawings in the embodiments of the present utility model, clearly and completely describe the technical solutions of the present utility model through implementation manners. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present utility model.

[0021] Embodiment 1

[0022] An induction temperature automatic voltage limiting circuit of the present utility model, as Figures 1 to 3As shown in the figure, it includes: a comparison control module, a switch control module, and a power limit module; among them, the switch control module is separately linked to the comparison control module and the power limit module; the power limit module is connected to the output module, and the output module is also connected to the input module.

[0023] In this embodiment, the output module includes the second operational amplifier unit U1 B. The input module includes the third operational amplifier unit U1A. The negative input terminal and the positive input terminal of the third operational amplifier unit U1A are used to access the balanced signals CHA+ and CHA-, and convert the balanced signals CHA+ and CHA- into single-sided signals. The output terminal of the third operational amplifier unit U1A is connected to the positive input terminal of the second operational amplifier unit U1 B, and is used to transmit the converted single-sided signal to the second operational amplifier unit U1 B, which is amplified by the second operational amplifier unit U1 B and then power output (CHA OUTPUT).

[0024] The comparison control module includes a thermistor RT2 and the first operational amplifier unit U9B; the thermistor RT2 is arranged on the transformer T1; the negative input terminal and the positive input terminal of the first operational amplifier unit U9B are respectively connected to the positive reference voltage +12V and the thermistor RT2.

[0025] Specifically, the thermistor RT2 is arranged on the secondary winding coil of the transformer T1. In this embodiment, when the transformer is produced, the thermistor RT2 is deeply buried and closely attached to the winding coil of the transformer T1, and is connected to two adjacent pins of the transformer T1 skeleton. According to the characteristics of the thermistor RT2, when the temperature of the transformer T1 is sensed to rise, the resistance value of the thermistor RT2 becomes smaller, and the resistance value of the thermistor RT2 changes with the temperature of the transformer T1.

[0026] More specifically, the comparison control module further includes a first voltage dividing resistor R44, a second voltage dividing resistor R34, and a third voltage dividing resistor R48. One end of the first voltage dividing resistor R44 is grounded, and the other end is connected to one end of the third voltage dividing resistor R48; one end of the second voltage dividing resistor R34 is connected to the positive reference voltage +12V, and the other end is connected to one end of the third voltage dividing resistor R48; the other end of the third voltage dividing resistor R48 is connected to the negative input terminal of the first operational amplifier unit U9B; the thermistor RT2 on the transformer T1 is connected to the positive input terminal of the first operational amplifier unit U9B through a resistor R50, forming a complete comparator circuit controlled by temperature. The positive reference voltage +12V is connected in series in the circuit composed of the thermistor RT2, and a value whose voltage magnitude changes with the temperature of the transformer is obtained after passing through the voltage dividing resistors (the first voltage dividing resistor R44, the second voltage dividing resistor R34, and the third voltage dividing resistor R48).

[0027] The switch control module includes a first switch unit and a second switch unit. The first switch unit includes a first triode Q5, a first diode D10, a first resistor R35, and a second resistor R58. The base of the first triode Q5 is connected to the output terminal of the first operational amplifier unit, and the collector is connected to the positive reference voltage +12V; one end of the first diode D10 is connected to the output terminal of the first operational amplifier U9B, and the other end is connected to the base of the first triode Q5 through the first resistor R35; the collector of the first triode Q5 is connected to the second resistor R58, and the emitter is grounded.

[0028] The second switch unit includes a second triode Q5, a second diode D6, and a third resistor R10; the base of the second triode Q5 is grounded, the collector is connected to one end of the second diode D6, and the emitter is connected to the emitter of the first triode Q5 through the third resistor R10; the other end of the second diode Q5 is connected to the current bias input terminal of the transconductance operational amplifier chip U3.

[0029] The power limit module includes a transconductance operational amplifier chip U3, and the transconductance operational amplifier chip U3 uses an operational amplifier chip with the model LM13700M. The specific chip pins are as follows:

[0030] Inverting input terminal: powered by the negative terminal of the chip power supply;

[0031] Pin 11: powered by the positive terminal of the chip power supply;

[0032] Pin 15: linear diode bias input terminal;

[0033] Pin 16; current bias input terminal;

[0034] Pin 14: non-inverting input terminal;

[0035] Pin 13: inverting input terminal;

[0036] Pin 12: unbuffered output terminal.

[0037] Among them, the current bias input terminal is connected to the output terminal of the switch control module; the inverting input terminal and the unbuffered output terminal are connected to the output module; the inverting input terminal and the unbuffered output terminal are respectively connected to the inverting input terminal and the non-inverting input terminal of the second operational amplifier unit U1B.

[0038] Specifically, the power limit module further includes a fourth voltage-dividing resistor R1 and a fifth voltage-dividing resistor R63; one end of the fourth voltage-dividing resistor R1 is connected to the negative reference voltage -12V, and the other end is connected to one end of the fifth voltage-dividing resistor R63; the other end of the fifth voltage-dividing resistor R63 is connected to the current bias input terminal.

[0039] More specifically, the power limit module further includes a sixth voltage-dividing resistor R67 and a seventh voltage-dividing resistor R54; the inverting input terminal is connected to the negative input terminal of the second operational amplifier unit U1 B through the sixth voltage-dividing resistor R67, and at the same time, the inverting input terminal is grounded through the seventh voltage-dividing resistor R54.

[0040] The specific working principle is as follows:

[0041] When the transformer T1 overheats due to an overloaded load and then reaches the set temperature, the thermistor RT2 senses the rising temperature of the transformer T1, and the resistance value of the thermistor RT2 gradually decreases, outputting a gradually increasing voltage value at the output terminal. Then, this level value is input to the positive input terminal and the negative input terminal of the first operational amplifier unit U9B through the resistor R50 for comparison. When the voltage at the positive input terminal is higher than the voltage at the negative input terminal, the output of pin 1 of the first operational amplifier unit U9B is also a high level, which is coupled and output to the first triode Q5 through the first diode D10 and the resistor R36; when the input of pin 1 of the first triode Q5 is a high level, the first triode Q5 and the second triode Q3 are simultaneously turned on. At this time, the final high level reaches pin 16 of the transconductance operational amplifier chip U3 through the input fifth voltage-dividing resistor R63. When the high level input to pin 16 of the transconductance operational amplifier chip U3 exceeds the set power limit starting value, the signal input by the operational amplifier will be power-limited and then an inverted signal will be output at pin 12 of the transconductance operational amplifier chip U3 to cancel the input signal; in this way, the input signal at the positive input terminal of the second operational amplifier unit U1 B decreases, and then the signal output at CHA OUTPUT decreases, and the power output of the amplifier becomes smaller, and the temperature of the transformer T1 in the amplifier works within a safe range.

[0042] Among them, the balanced signal is input at both ends of CHA+ and CHA- respectively, and is converted into a single-sided signal after passing through the third operational amplifier unit U1A. Then it is transmitted to the non-inverting input terminal of the second operational amplifier unit U1B through the resistor R6 and the resistor R69. Since the circuit of the second operational amplifier unit U1B is a voltage follower, all the output voltage is fed back to the inverting input terminal for negative-phase input. The current bias input terminal of the normal transconductance operational amplifier chip U3 is a negative terminal control signal. When it receives the signal from pin 3 of Q3, it immediately reverses to a positive signal and is input to the current bias input terminal of the chip. Through the operation, the output signal of U1B is fed back to the inverting input terminal, the non-inverting input terminal, and the reference value set at pin 15 for operation and quantization. Finally, the non-buffered output terminal of the transconductance operational amplifier chip U3 outputs an anti-phase signal opposite to the signal of R69 to cancel the signal. The higher the temperature rise of the transformer, the higher the high-level signal fed back to the current bias input terminal of the chip, and the more anti-phase cancellation signals are output from the non-buffered output terminal of the chip. In this way, the input signal at the non-inverting input terminal of the second operational amplifier unit U1B is greatly reduced, and the output signal of the second operational amplifier unit U1B is reduced. The CHA OUTPUT signal output through the resistor R65 is reduced to the power amplifier terminal, thus realizing the function that the higher the temperature of the transformer T1, the lower the output power of the power amplifier.

[0043] To sum up, the utility model has the following beneficial effects: the circuit is simple, debugging-free, the circuit design is safer, it can detect the temperature rise of the transformer automatically and scientifically in real time, and perform power limitation. It can adjust the temperature rise of the transformer more scientifically, so that the transformer can work within a safe temperature range for a long time, effectively reducing the failure rate.

[0044] Note that the above is only the preferred embodiment of the utility model and the applied technical principle. Those skilled in the art will understand that the utility model is not limited to the specific embodiments described here. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the utility model. Therefore, although the utility model has been described in detail through the above embodiments, the utility model is not limited to the above embodiments. Without departing from the concept of the utility model, it can also include more other equivalent embodiments, and the scope of the utility model is determined by the scope of the appended claims.

Claims

1. A temperature sensing automatic voltage limiting circuit, characterized in that: include: a comparison control module, a switch control module and a power limiting module; The switch control module is separately linked to the comparison control module and the power limiting module; The comparison control module includes a thermistor and a first operational amplifier unit; the thermistor is arranged on a transformer; two input terminals of the first operational amplifier unit are respectively connected to a positive reference voltage and the thermistor; The switch control module comprises a first switch unit, the first switch unit comprises a first transistor, the base of the first transistor is connected to the output end of the first operational amplifier unit, and the collector is connected to the positive reference voltage; The power limiting module includes a transconductance amplifier chip, and a current bias input terminal of the transconductance amplifier chip is connected to an output terminal of the switch control module; The inverting input terminal and the unbuffered output terminal of the transconductance amplifier chip are connected to the output module.

2. The temperature-sensing automatic voltage-limiting circuit according to claim 1, characterized in that: The first switch unit further includes a first diode, a first resistor and a second resistor; One end of the first diode is connected to the output end of the first operational amplifier unit, and the other end is connected to the base of the first transistor via a first resistor; The collector of the first transistor is connected to the second resistor, and the emitter is grounded.

3. The temperature-sensing automatic voltage-limiting circuit according to claim 1, characterized in that: The switch control module further includes a second switch unit; The second switch unit includes a second triode, a second diode and a third resistor; The base of the second transistor is grounded, the collector is connected to one end of the second diode, and the emitter is connected to the emitter of the first transistor via the third resistor; The other end of the second diode is connected to the current bias input end of the transconductance amplifier chip.

4. The temperature sensing automatic voltage limiting circuit according to any one of claims 1 to 3, characterized in that: The comparison control module also includes a first voltage-dividing resistor, a second voltage-dividing resistor and a third voltage-dividing resistor; One end of the first voltage-dividing resistor is grounded, and the other end is connected to one end of the third voltage-dividing resistor; One end of the second voltage-dividing resistor is connected to a positive reference voltage, and the other end is connected to one end of the third voltage-dividing resistor; The other end of the third voltage-dividing resistor is connected to the negative phase input end of the first operational amplifier unit.

5. The temperature-sensing automatic voltage-limiting circuit according to claim 4, characterized in that: The power limiting module further includes a fourth voltage-dividing resistor and a fifth voltage-dividing resistor; One end of the fourth voltage-dividing resistor is connected to a negative reference voltage, and the other end is connected to one end of the fifth voltage-dividing resistor; The other end of the fifth voltage-dividing resistor is connected to the current bias input end of the transconductance amplifier chip.

6. The temperature-sensing automatic voltage-limiting circuit according to claim 5, characterized in that: The output module includes a second operational amplifier unit; The non-inverting input terminal of the second operational amplifier unit is used to connect to the input module; The inverting input terminal and the unbuffered output terminal of the transconductance operational amplifier chip are respectively connected to the negative phase input terminal and the positive phase input terminal of the second operational amplifier unit.

7. The temperature-sensing automatic voltage-limiting circuit according to claim 6, characterized in that: The power limiting module further includes a sixth voltage-dividing resistor and a seventh voltage-dividing resistor; The inverting input terminal of the transconductance amplifier chip is connected to the negative input terminal of the second amplifier unit through the sixth voltage-dividing resistor, and at the same time, the inverting input terminal of the transconductance amplifier chip is grounded through the seventh voltage-dividing resistor.

8. The temperature-sensing automatic voltage-limiting circuit according to claim 6, characterized in that: The input module comprises a third operational amplifier unit, a negative phase input terminal and a positive phase input terminal of the third operational amplifier unit are used to receive a balanced signal, and an output terminal is connected to the positive phase input terminal of the second operational amplifier unit.

9. The temperature-sensing automatic voltage-limiting circuit according to claim 4, characterized in that: The transconductance operational amplifier chip adopts an operational amplifier chip of model LM13700M.

10. The temperature-sensing automatic voltage-limiting circuit according to claim 4, characterized in that: The thermistor is arranged on the secondary winding coil of the transformer.

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