CN108306258A - A kind of excess temperature detection circuit and thermal-shutdown circuit for heater - Google Patents
A kind of excess temperature detection circuit and thermal-shutdown circuit for heater Download PDFInfo
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- CN108306258A CN108306258A CN201810298704.XA CN201810298704A CN108306258A CN 108306258 A CN108306258 A CN 108306258A CN 201810298704 A CN201810298704 A CN 201810298704A CN 108306258 A CN108306258 A CN 108306258A
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
- H02H5/04—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature
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- Control Of Resistance Heating (AREA)
- Control Of Temperature (AREA)
Abstract
This application involves a kind of excess temperature detection circuits and thermal-shutdown circuit for heater.The advantageous effect of the application is excess temperature detection circuit as described herein and thermal-shutdown circuit without using temperature sensor, only just can determine whether that heater whether there is excess temperature situation by detecting the difference in voltage of supply voltage and heater both ends.In addition, in the case where only needing to increase external circuit and protection switch, the overheat protector for heater can be achieved with.Single failure defencive function is not lost while this can substantially reduce heater volume yet.A kind of novel thinking is provided in terms of heater is miniaturized, there is very high practical value and economic value.
Description
Technical field
This application involves electrical engineering technical fields, it particularly relates to a kind of excess temperature detection circuit for heater
And thermal-shutdown circuit.
Background technology
Heter temperature control is widely adopted in industry-by-industry.But the safety issue of heater is also closed
Note.
According to traditional safety requirement, it is uncontrolled shall not temperature to occur for heater under any device single failure
Rise phenomena such as even on fire always.
Traditional solution mainly seals in temperature switch in heating installation power supply circuit, for detecting heater temperature
Degree disconnects heating installation power supply after heter temperature reaches a certain limit value.Temperature switch is there are two types of form, and one is from extensive
Replica, a kind of is non-self- recoverage type.No matter which kind of mode to have many drawbacks using, as Thermal protection point is opened depending on temperature
Self character is closed, outside cannot adjust again；The meeting of self- recoverage type causes heater work near overheat protector zero point
Make, still deviate normal higher section work, can still bring hidden danger for a long time, or propose to the electronic equipment heatproof of surrounding
Requirements at the higher level；Non- self- recoverage type voluntarily fuses once protection, and repair must just replace protection device, temperature switch stock size
It is all bigger, it is difficult application in some microheaters, and temperature switch ordinary disbursements are more expensive, to heater cost control
It is unfavorable.
Also be exactly conventional method it is temperature dependent sensor to temperature control, temperature sensor, which must increase, to be heated
On device, heater volume and heater circuit cost are further increased.
For this purpose, electric for the detection of heater excess temperature there is an urgent need in the art to develop a kind of one kind without using temperature sensor
Road and thermal-shutdown circuit.
Invention content
The application's is designed to provide a kind of excess temperature detection circuit for heater without using temperature sensor, from
And solve it is above-mentioned in the prior art the technical issues of.Specifically, the circuit of the application is compared by increasing a voltage detecting
Circuit judges whether heater the case where excess temperature occurs.Heater is usually the heater of positive temperature coefficient, i.e., with temperature liter
Height, resistance increase.The excess temperature detection circuit of the application is powered heater by constant-current circuit, is then compared by voltage
Supply voltage is compared by device with the difference in voltage at heater both ends with the temperature protection of setting point voltage, if supply voltage
It is less than temperature protection point voltage with the difference in voltage at heater both ends, then showing heater, there are excess temperature situations.
The purpose of the application, which also resides in, provides a kind of overheat protector for heater using above-mentioned excess temperature detection circuit
Circuit.
To achieve the goals above, the application provides following technical proposals.
In the first aspect, the application provides a kind of thermal-shutdown circuit for heater, described for heater
Thermal-shutdown circuit includes heater, the constant-current circuit to heating installation power supply, voltage comparator, protection switchs and first resistor,
The voltage comparator includes "+" end input terminal, "-" end input terminal and output end, described when excess temperature situation occurs in heater
The output end of voltage comparator exports excess temperature signal；
The wherein described protection switch and heater series connection；
The wherein described first resistor is configured in parallel with the heater；
The "+" end input terminal of the wherein described voltage comparator be used to input supply voltage and heater both ends voltage it
Difference, and the "-" end input terminal of voltage comparator is for input temp protection point voltage；And
The output end of the voltage comparator is electrically connected with protection switch, and is configured in the voltage comparator
When output end exports excess temperature signal, the protection switch is disconnected.
In a kind of embodiment of first aspect, the heater is the heater of positive temperature coefficient.
In the another embodiment of first aspect, the protection switch is cmos device and/or solid-state relay.
In the another embodiment of first aspect, the protection switch is cmos device, the grid of the cmos device
The output end of pole and the voltage comparator is electrically connected, and the thermal-shutdown circuit for heater further includes the second electricity
Resistance, which is electrically connected with the grid of the cmos device and the output end electricity of the other end and the voltage comparator
Connection.
In the another embodiment of first aspect, the thermal-shutdown circuit for heater further includes digital mould
Quasi- converter, external temperature control circuit and micro-control unit；
The wherein described digital analog converter is for output temperature protection point voltage；
The wherein described micro-control unit is configured to receive the excess temperature signal of the voltage comparator output end and provide external
Temperature controls input signal；And
The wherein described external temperature control circuit is configured to reset and protection switch.
In the another embodiment of first aspect, the thermal-shutdown circuit for heater further includes digital mould
Quasi- converter, external switching on/off circuit and control logic circuit；
The wherein described digital analog converter is for output temperature protection point voltage；
For providing fixed pulse width input signal, the fixed pulse width input signal is used for the wherein described external switching on/off circuit
Control the break-make of constant-current circuit；
The wherein described control logic circuit includes concatenated CMOS and gate device and at least one Schmidt's NOT gate device,
One end of at least one Schmidt's NOT gate device is electrically connected with the output end of the voltage comparator, and the other end with it is described
CMOS is electrically connected with the input terminal of gate device；And
The wherein described fixed pulse width input signal is electrically connected with the CMOS with the input terminal of gate device, and the CMOS with
The output end of gate device is electrically connected with the constant-current circuit.
In the another embodiment of first aspect, when there is excess temperature situation in heater, the voltage comparator
Output end exports the low level as excess temperature signal, and the protection switch disconnects.
In the another embodiment of first aspect, when there is excess temperature situation in heater, the voltage comparator
Output end exports the low level as excess temperature signal, and the protection switch disconnects, and the micro-control unit receives excess temperature signal
Afterwards, the protection switch is made to re-close by the external temperature control circuit.
In the another embodiment of first aspect, when there is excess temperature situation in heater, the voltage comparator
Output end exports the low level as excess temperature signal, and the protection switch disconnects, and the external temperature control circuit is detecting heating
When the temperature of device is reduced to acceptable maximum temperature or less, the protection switch is made to re-close.
In the another embodiment of first aspect, when there is excess temperature situation in heater, the voltage comparator
Output end exports the low level as excess temperature signal, and the protection switch disconnects, and what external switching on/off circuit provided fixes next time
Pulsewidth input signal makes constant-current circuit be electrically connected again, so that protection switch is closed again, and be again started up heater.
In second aspect, the application provides a kind of excess temperature detection circuit for heater, the excess temperature detection circuit
Constant-current circuit and voltage comparator including heater, to heating installation power supply, the voltage comparator include "+" end input terminal,
"-" end input terminal and output end,
The "+" end input terminal of the wherein described voltage comparator be used to input supply voltage and heater both ends voltage it
Difference, and the "-" end input terminal of voltage comparator is for input temp protection point voltage.
In a kind of embodiment of second aspect, when there is excess temperature situation in heater, the voltage comparator output
End output low level.
Compared with prior art, the advantageous effect of the application is excess temperature detection circuit as described herein and overheat protector electricity
Road only just can determine whether that heater is without using temperature sensor by detecting the difference in voltage of supply voltage and heater both ends
No there are excess temperature situations, and in the case where only needing to increase external circuit and protection switch, can be achieved with self- recoverage type or non-
The overheat protector for heater of self- recoverage type, this does not also lose single failure while can substantially reducing heater volume
Defencive function.A kind of novel thinking is provided in terms of heater is miniaturized, there is very high practical value and economic value.
Description of the drawings
Fig. 1 schematically shows the constant-current circuit of one embodiment according to the application.
Fig. 2 schematically shows the excess temperature detection circuit according to one embodiment of the application.
Fig. 3 schematically shows the thermal-shutdown circuit of one embodiment according to the application.
Fig. 4 schematically shows the schematic diagram of the non-self- recoverage type thermal-shutdown circuit of one embodiment according to the application.
Fig. 5 schematically shows the non-self- recoverage type thermal-shutdown circuit of another embodiment according to the application.
Fig. 6 schematically shows the schematic diagram of the temperature control circuit of one embodiment according to the application.
Fig. 7 schematically shows the temperature control circuit of another specific embodiment according to the application.
Specific implementation mode
Below in conjunction with attached drawing and embodiments herein, carries out clear to the technical solution of the application and completely retouch
It states.
Term defines
As used herein, term " temperature protection point voltage " is referred in the feelings heated to heater using constant-current circuit
Under condition, the difference in voltage of supply voltage and heater both ends when heater is under acceptable maximum temperature.Temperature protection
Point voltage can be more than zero and less than the supply voltage of constant-current circuit.
As used herein, term " excess temperature signal " refers to when excess temperature situation occurs in heater, the output of voltage comparator
The exported signal in end.Under normal conditions, excess temperature signal refers to the low level of the output end output of voltage comparator.
In the first aspect, the application provides a kind of thermal-shutdown circuit for heater, described for heater
Thermal-shutdown circuit includes heater, the constant-current circuit to heating installation power supply, voltage comparator, protection switchs and first resistor,
The voltage comparator includes "+" end input terminal, "-" end input terminal and output end, described when excess temperature situation occurs in heater
The output end of voltage comparator exports excess temperature signal；
The wherein described protection switch and heater series connection；
The wherein described first resistor is configured in parallel with the heater；
The "+" end input terminal of the wherein described voltage comparator be used to input supply voltage and heater both ends voltage it
Difference, and the "-" end input terminal of voltage comparator is for input temp protection point voltage；And
The output end of the voltage comparator is electrically connected with protection switch, and is configured in the voltage comparator
When output end exports excess temperature signal, the protection switch is disconnected.
In the another embodiment of first aspect, the thermal-shutdown circuit for heater further includes digital mould
Quasi- converter, external temperature control circuit and micro-control unit；
The wherein described digital analog converter is for output temperature protection point voltage；
The wherein described micro-control unit is configured to receive the excess temperature signal of the voltage comparator output end；And
The wherein described external temperature control circuit is configured to reset and protection switch.
In the another embodiment of first aspect, the thermal-shutdown circuit for heater further includes digital mould
Quasi- converter, external switching on/off circuit and control logic circuit；
The wherein described digital analog converter is for output temperature protection point voltage；
For providing fixed pulse width input signal, the fixed pulse width input signal is used for the wherein described external switching on/off circuit
Control the break-make of constant-current circuit；
The wherein described control logic circuit includes concatenated CMOS and gate device and at least one Schmidt's NOT gate device,
One end of at least one Schmidt's NOT gate device is electrically connected with the output end of the voltage comparator, and the other end with it is described
CMOS is electrically connected with the input terminal of gate device；And
The wherein described fixed pulse width input signal is electrically connected with the CMOS with the input terminal of gate device, and the CMOS with
The output end of gate device is electrically connected with the constant-current circuit.
In second aspect, the application provides a kind of excess temperature detection circuit for heater, the excess temperature detection circuit
Constant-current circuit and voltage comparator including heater, to heating installation power supply, the voltage comparator include "+" end input terminal,
"-" end input terminal and output end,
The "+" end input terminal of the wherein described voltage comparator be used to input supply voltage and heater both ends voltage it
Difference, and the "-" end input terminal of voltage comparator is for input temp protection point voltage.
In a specific embodiment, the application provides a kind of heater thermal-shutdown circuit, and feature includes：
Temperature sensor or temperature switch need not be increased；
Adapt to the heater with positive warm resistance coefficient；
Using current constant mode to heating installation power supply, while the constant-current source can be controlled by external signal and be switched；
The voltage for the voltage detecting point brought by heater resistance variation by a voltage detecting comparison circuit detection becomes
Change, and the excess temperature voltage output by setting controls signal and switched to protection；
Protection switch disconnects heater current and realizes overheat protector；
The circuit once detects excess temperature, removes non-reset, otherwise can disconnect heater power source always, will not break-make repeatedly,
Cause practical of temperature protection the problem of excess temperature boundary lifts repeatedly；
The circuit can realize that online protection resets, i.e., in the case where not doing any power operation, believed by external reset
Number resetting protection circuit, heater can be worked normally；
This protects circuit not change external control circuit, does not influence the original external temperature closed control circuit of temperature control system
With control mode method or program, it is only necessary to do improvement to heating installation power supply circuit and can be realized；
In a specific embodiment, heater should be with temperature rise, and the heater that internal resistance rises is namely
The heater of positive temperature coefficient.For heater material characteristic, heater should all be positive temperature coefficient.Because in atomic scale
On with temperature rise, the electronics for participating in hot disordered motion is more and more, voltage control under, present a direction movement electricity
Son is fewer and fewer, and actual effect is exactly that electric current reduces, i.e., resistance increases.So actually this patent should be adapted to all add
Hot device.
In a specific embodiment, constant-current circuit can carry out start-up and shut-down control by external control signal, open
Current constant control when dynamic, when stopping, constant-current circuit does not export.Make that external control circuit is supplied to carry out temperature in this way
Spend the mode of closed-loop control.
In a specific embodiment, continuous current should be less than the minimum current of heater operation interval, i.e. heater
In normal work, electric current should be the constant not change with heater resistance variation under energized state；
In a specific embodiment, excess temperature voltage can be reset, or even pass through controller and digital-to-analogue converting means
It sets and is reset online, to achieve the purpose that the different protection temperature of setting.
In a specific embodiment, it after thermal-shutdown circuit as described herein enters guard mode, is re-closing off and opens
Stop signal, then open again, can be switched with reset and protection.In this embodiment, the reset need not change any original
There is software and hardware, it is only necessary to increase protection circuit and protection switchs.
In a specific embodiment, by being improved to the excess temperature detection circuit described in first aspect, it can be achieved that
A kind of non-temperature-control circuit of the self- recoverage type without temperature sensor, which is characterized in that
There is no temperature sensor；
It disconnecting, can't restore automatically after temperature rise to some set point, external circuit can detect the off-state, and
Judge whether to need to continue for control temperature；
It is online by external digital-to-analog circuit by temperature protection point voltage in the voltage detecting comparison circuit described in first aspect
The arbitrary temp control of circuit may be implemented in setting；
In a specific embodiment, by being improved to the excess temperature detection circuit described in first aspect, it can be achieved that
A kind of temperature-control circuit of the self- recoverage type without temperature sensor, which is characterized in that
Increase logic judgment in the control leading portion of constant-current circuit, increases a fixed pulse width input signal, and voltage is allowed to examine
It surveys the excess temperature signal exported in comparison circuit and participates in control；
When excess temperature signal arrives, in any state, constant-current circuit can all be stopped external start stop signal, next
Secondary pulse width signal reset circuit, heater can be again started up again, and enabled protection becomes in this way again immediately after excess temperature
The pulsewidth of the change pulse-width controlled of phase reaches temperature controlled purpose.
Thermal-shutdown circuit as described herein is powered firstly the need of a controlled constant-current circuit.This circuit needs simultaneously
It is controlled, it can be opened and closed by outside.With reference to figure 1, Fig. 1 schematically shows the perseverance of one embodiment according to the application
Current circuit.As shown, electric current, which is opened and closed controllable function, to be realized by Q2.When control input is high level, the electricity of Q1
Pressure is U1 output voltages, and the output of U1 is the current controling signal of Q1.The function of constant current is realized by R1, Q1, U1, V1
's.R1 is current sampling resistor, V1 voltages in order to control.When output current is smaller, the "-" terminal voltage of U1 is less than V1, U1 amplifiers
Output voltage increases, when electric current becomes larger, U1-terminal voltage becomes larger, slowly reach the state equal with V1, the output of U1 is slowly
Become smaller, until entering a stable state.R2 is isolation resistance, to realize that the grid voltage of Q1 can be dragged down by Q2.
The constant-current circuit has following feature：1) controlled end of the circuit can input pwm control signal, need not more change to
What original control circuit and software program.2) V1 can be changed to be exported by DAC, and electric current output is adjustable.
For ease of control, which should design in power supply negative terminal, that is, the ground terminal usually said.In another situation
Under, when needing to reduce publicly impedance, the constant-current source designed in anode is could be used that in the method that this patent is announced, it is only necessary to control
Logic processed slightly makes an amendment and increases a control terminal boostrap circuit.
There is no stringent limitations to heater by the application, it is only necessary to be positive warm resistance coefficient.The electricity that this patent is announced
Road can realize that no temperature sensor or temperature switch can be achieved with the principle of temperature protection, that is, realize to heater itself
Resistance value monitored on-line, when resistance value be more than certain value when, the heating installation power supply is switched off, to reach the mesh of protection
's.
Next, by the excess temperature detection circuit being discussed in detail with reference to figure 2 according to the application for heater and crossing temperature detector
Survey method.Fig. 2 schematically shows the excess temperature detection circuit according to one embodiment of the application.As shown in Fig. 2, the excess temperature detects
Circuit includes heater, the constant-current circuit for heating installation power supply and voltage comparator U2.The "+" end of U2 is for inputting power supply electricity
The difference in voltage Vp of pressure and heater both ends, "-" end is for input temp protection point voltage V2.
It can judge whether heater excess temperature situation occurs by detecting the voltage V0 of voltage comparator output end.Below will
Transient analysis is carried out to the circuit.When heater just starts, resistance is smaller, so the voltage at heater both ends is smaller, in turn
So that supply voltage and the difference Vp of heater both end voltage are more than temperature protection point voltage V2, the output end of voltage comparator U2 is defeated
Go out high level, is i.e. is high level at V0.As heter temperature increases, Vp is gradually reduced, and until being less than V2, voltage compares at this time
The output end of device U2 exports low level, i.e. is low level at V0.Therefore, the electricity of the output end of detection voltage comparator U2 can be passed through
V0 is pressed to judge that heater whether there is excess temperature situation, without temperature in use sensor.
Below with reference to Fig. 3 to Fig. 7 detailed descriptions according to the thermal-shutdown circuit and use for heater of the application
In the excess temperature protection method of heater.
Fig. 3 schematically shows the thermal-shutdown circuit of one embodiment according to the application.As shown in figure 3, Q3 is protection
Switch, protection switch can use other devices such as solid-state relay, the replacements such as contact relay.U2 is voltage comparator, U2
Voltage monitoring circuit is formed with V2.
There are one stable states for thermal-shutdown circuit shown in Fig. 3, and can this is the key that the circuit reset.It below will be to the electricity
Road carries out transient analysis.In the case where constant-current circuit is closed, if Q3 is opened, Q3 and heater can be such that Vp is directly equal to
Supply voltage (high level).If Q3 is closed, voltage can be directly pulled upward to supply voltage by R4.As long as that is, permanent
Current circuit is closed, and no matter Q3 is turned on and off, and Vp is equal to supply voltage.Because detection comparison voltage V2 is typically larger than 0 and small
In supply voltage, so U2 comparators export high level.Constant-current circuit conducting in a flash, due to the presence of parasitic capacitance,
The grid voltage of Q3 has delay, and the grid of Q3 is high level to source electrode, which can control Q3 to keep it turned on.
Since Q3 is opened, Q3 itself internal resistances are negligible or can be converted into fixed resistance, under constant current state, Vp only and
Heater resistance is related.When heater is not when temperature is high, heater resistance is smaller, and heater both ends resistance is not high, Vp
The small voltage at heater both ends is subtracted for power source supplying voltage.As heter temperature rises, heater resistance rises, heater
Both end voltage increases, and Vp is smaller and smaller.When heater resistance is more than certain value, Vp can be less than V2, and U2 outputs are immediately turned into low electricity
It is flat.In this case, Q3 ends, and since constant-current circuit itself is also in open state, after Q3 cut-offs, Vp declines rapidly, U2
Output remain unchanged.At this point, circuit enters stable state, heater power source is cut off, to reach the purpose of protection heater.
As described above, regardless of whether Q3 opens, as long as constant-current circuit is closed, then it is then turned on, Q3 must be in open
Open state.It is primary by being then turned on after constant-current circuit is closed, so that it may to realize the reset of protection switch.After reset, if
Heter temperature starts to work normally less than protection temperature, heater.If heter temperature is higher than protection temperature, circuit is again
Guard mode is quickly entered, in the power supply for not resetting the disconnected heater of previous vertical cut.
V2 in the circuit can do calibration according to actual conditions and adjust, such as can be made by way of electric resistance partial pressure
With slide rheostat, the protection temperature of heater is strictly limited in some temperature spot.
If V2 is exported using digital analog converter (DAC), the logic Modification of cooperation micro-control unit (MCU) can
As a kind of temperature controlled means, and the participation of temperature sensor is not needed.Referring specifically to Fig. 4 and Fig. 5, Fig. 4 is schematically shown
Show the schematic diagram of the non-self- recoverage type thermal-shutdown circuit of one embodiment according to the application.In schematic diagram shown in Fig. 4,
The similar but more external temperature control circuit of the protection circuit of the principle of overheat protector as shown in figure 3.The outside temperature control circuit can be to perseverance
Current circuit inputs pulsewidth fixed modulation formula (PWM) signal, to control the break-make of constant-current circuit.In a kind of specific implementation mode
In, external temperature control circuit can detect the temperature of heater by temperature sensor, be reduced in the temperature of heater acceptable
Temperature range within when, be again started up heater.
Fig. 5 schematically shows the non-self- recoverage type thermal-shutdown circuit of another embodiment according to the application.In Fig. 5 institutes
In the circuit shown, control temperature is output to U2 by DAC, and when temperature is excessively high, voltage comparator U2 exports excess temperature output signal
After recognizing the signal to MCU, MCU, by control signal reset circuit, heater continues to heat again.When heater goes out
When existing excess temperature situation, voltage comparator U2 continues to output excess temperature signal, and MCU resets control again.Since change in resistance signal comes
From in the exothermic material of heater itself, temperature time delay is very low, thus the temperature-controllable performance ratio it is common heater it is good,
The temperature-controlled precision that PID control can also reach certain is not needed.
If being exported to the excess temperature of the thermal-shutdown circuit described in Fig. 3 and control signal carrying out logic change, MCU ginsengs
It can also be omitted with temperature controlled processes, it is only necessary to which DAC is exported and switching signal.Referring specifically to Fig. 6 and Fig. 7, wherein Fig. 6
Schematically show the schematic diagram of the temperature control circuit of another specific embodiment according to the application.Circuit theory described in Fig. 6
In figure, control logic circuit is increased in constant-current circuit leading portion so that the excess temperature signal of voltage detecting comparison circuit with it is outer
The control signal of portion's switching on/off circuit simultaneously participates in the break-make of control constant-current circuit.
Fig. 7 schematically shows the temperature control circuit of another specific embodiment according to the application.With it is shown in fig. 5 non-from extensive
Replica thermal-shutdown circuit is compared, and temperature control circuit shown in fig. 7 exports the voltage comparator in voltage detecting comparison circuit
End excess temperature output negate after and switch the input phase and.When switch input is closed, circuit is in reset state.Work as switch
After opening, after the temperature rise to certain temperature of heater, U2 outputs low level passes through CMOS and gate device after U3A is negated
U4 and switch the input phase with control constant-current circuit is closed, and reset switch.In a specific embodiment, U3 is
CD40106.In a specific embodiment, U4 74HC08.After switch normal work, heater continues to heat.Such as temperature
It is more than protection temperature again, U2 exports excess temperature signal immediately again, and closes constant-current circuit and reset.So reach temperature in temperature control point
The effect to float up and down.U3 herein is temperature in a period of time after triggering in order to prevent using the purpose of schmidt trigger NOT gate
The time of decline is inadequate, and continues to be heated, and temperature is caused to continue to rise, can not be constant.If the triggered time is inadequate, Ke Yiduo
Add and seal in several Schmidt triggers, and optionally can increase resistance capacitance in these schmidt triggers to reduce signal intensity
Speed to prevent temperature fall time inadequate.
Fig. 5 and circuit shown in Fig. 7 all do not need temperature sensor and participate in temperature control, do not need temperature switch ginseng more
With do not lose single failure defencive function while can greatly reducing heater volume yet.In terms of heater is miniaturized
A kind of novel thinking is provided, there is very high practical value and economic value.
The above-mentioned description to embodiment is that this Shen can be understood and applied for the ease of those skilled in the art
Please.Person skilled in the art obviously easily can make various modifications to these embodiments, and described herein
General Principle is applied in other embodiments without paying performing creative labour.Therefore, the application is not limited to implementation here
Example, those skilled in the art make according to herein disclosed content in the case where not departing from the application scope and spirit
It improves and changes within all scope of the present application.
Claims (12)
1. a kind of thermal-shutdown circuit for heater, the thermal-shutdown circuit for heater include heater, to
The constant-current circuit of heating installation power supply, voltage comparator, protection switchs and first resistor, the voltage comparator include that "+" end is defeated
Enter end, "-" end input terminal and output end, when excess temperature situation occurs in heater, the output end of the voltage comparator exported
Warm signal；
The wherein described protection switch and heater series connection；
The wherein described first resistor is configured in parallel with the heater；
The "+" end input terminal of the wherein described voltage comparator is used to input the difference in voltage of supply voltage and heater both ends, and
The "-" end input terminal of voltage comparator is for input temp protection point voltage；And
The output end of the voltage comparator is electrically connected with protection switch, and is configured to the output in the voltage comparator
When the output excess temperature signal of end, the protection switch is disconnected.
2. being used for the thermal-shutdown circuit of heater as described in claim 1, which is characterized in that the heater is that positive temperature is
Several heaters.
3. being used for the thermal-shutdown circuit of heater as described in claim 1, which is characterized in that the protection switch is CMOS
Device and/or solid-state relay.
4. being used for the thermal-shutdown circuit of heater as claimed in claim 3, which is characterized in that the protection switch is CMOS
The output end of device, the grid of the cmos device and the voltage comparator is electrically connected, and the excess temperature for heater
Protect circuit further include second resistance, the second resistance one end be electrically connected with the grid of the cmos device and the other end with it is described
The output end of voltage comparator is electrically connected.
5. being used for the thermal-shutdown circuit of heater as described in claim 1, which is characterized in that the mistake for heater
Temperature protection circuit further includes digital analog converter, external temperature control circuit and micro-control unit；
The wherein described digital analog converter is for output temperature protection point voltage；
The wherein described micro-control unit is configured to receive the excess temperature signal of the voltage comparator output end and provides external temperature
Control input signal；And the wherein described external temperature control circuit is configured to reset and protection switch.
6. being used for the thermal-shutdown circuit of heater as described in claim 1, which is characterized in that the mistake for heater
Temperature protection circuit further includes digital analog converter, external switching on/off circuit and control logic circuit；
The wherein described digital analog converter is for output temperature protection point voltage；
The wherein described external switching on/off circuit is for providing fixed pulse width input signal, and the fixed pulse width input signal is for controlling
The break-make of constant-current circuit；
The wherein described control logic circuit includes concatenated CMOS and gate device and at least one Schmidt's NOT gate device, described
One end of at least one Schmidt's NOT gate device is electrically connected with the output end of the voltage comparator, and the other end and the CMOS
It is electrically connected with the input terminal of gate device；And
The wherein described fixed pulse width input signal is electrically connected with the CMOS with the input terminal of gate device, and the CMOS and door device
The output end of part is electrically connected with the constant-current circuit.
7. being used for the thermal-shutdown circuit of heater as described in claim 1, which is characterized in that when tender feeling occurred in heater
When condition, the output end of the voltage comparator exports the low level as excess temperature signal, and the protection switch disconnects.
8. being used for the thermal-shutdown circuit of heater as claimed in claim 5, which is characterized in that when tender feeling occurred in heater
When condition, the output end of the voltage comparator exports the low level as excess temperature signal, and the protection switch disconnects, the micro-control
After unit processed receives excess temperature signal, the protection switch is set to re-close by the external temperature control circuit.
9. being used for the thermal-shutdown circuit of heater as claimed in claim 5, which is characterized in that when tender feeling occurred in heater
When condition, the output end of the voltage comparator exports the low level as excess temperature signal, and the protection switch disconnects, the outside
Temperature control circuit makes the protection switch close again when the temperature for detecting heater is reduced to acceptable maximum temperature or less
It closes.
10. being used for the thermal-shutdown circuit of heater as claimed in claim 5, which is characterized in that when excess temperature occurs in heater
When situation, the output end of the voltage comparator exports the low level as excess temperature signal, and the protection switch disconnects, and outside is opened
The input signal of fixed pulse width next time that power failure road provides makes constant-current circuit be electrically connected again, and protection switch is made to be closed again, and
It is again started up heater.
11. a kind of excess temperature detection circuit for heater, the excess temperature detection circuit includes heater, to heating installation power supply
Constant-current circuit and voltage comparator, the voltage comparator include "+" end input terminal, "-" end input terminal and output end,
The "+" end input terminal of the wherein described voltage comparator is used to input the difference in voltage of supply voltage and heater both ends, and
The "-" end input terminal of voltage comparator is for input temp protection point voltage.
12. it is used for the excess temperature detection circuit of heater as claimed in claim 11, it is described when excess temperature situation occurs in heater
Voltage comparator output end exports low level.
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| CN201810298704.XA CN108306258B (en) | 2018-04-04 | 2018-04-04 | Over-temperature detection circuit and over-temperature protection circuit for heater |
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| CN201810298704.XA CN108306258B (en) | 2018-04-04 | 2018-04-04 | Over-temperature detection circuit and over-temperature protection circuit for heater |
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