JP2000003220A - Temperature control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature control circuit for lengthening the life of a member whose temperature is to be controlled. SOLUTION: This temperature control circuit is constituted of a CPU 1 for outputting a temperature control signal as a PWM(pulse width modulation) signal, a comparator for comparing this PWM signal with an output signal from a temperature sensor, and a driver for driving a temperature control element based on the output of this comparator. This temperature control circuit is also provided with a temporary temperature setting means for applying a temporary control signal in the neighborhood of a set temperature or in a non-destructive range to a temperature control element until a normal temperature control signal is outputted from the CPU 1 when any normal temperature control signal is not outputted from the CPU 1 due to a reset state or abnormality or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control circuit for controlling the temperature of a temperature controlled member based on a setting signal from a CPU, and more particularly to a temperature controlled circuit when a normal signal is not output from the CPU. The present invention relates to a temperature control circuit for extending the life of a temperature control circuit.

[0002]

2. Description of the Related Art As a temperature control circuit of a spectrum monitor, for example, there is one having a configuration shown in FIG. In FIG.
A signal corresponding to the set temperature from the CPU 1 (PWM: pulse width modulation, PPM: pulse position
Modulation, FM ... frequency modulation, etc., and this output is a low-pass filter (hereinafter, referred to as
The signal is converted to an analog signal via an LPF 2 and input to one input terminal of a comparator 3 provided at a subsequent stage.

A temperature controlled member (photodiode array, hereinafter simply referred to as PDA) 4 constituting a spectrum monitor is heated or cooled by a temperature control element (for example, Peltier element) 5 and its temperature is detected by a temperature sensor 6. You. The output of the temperature sensor 6 is input to the other end of the comparator 3 and is compared with the output from the LPF 2 to calculate the difference. Then, the comparator 3 outputs a signal corresponding to the difference to the driver 7, and the driver 7 heats or cools the Peltier element 5. In this way, the temperature of the PDA is maintained at a predetermined temperature.

[0004]

By the way, in the temperature control circuit having the above-mentioned conventional configuration, there is no problem when the CPU is operating normally. However, the CPU is reset or abnormal, and a normal PWM signal is output. Otherwise, an abnormal value may be set as the temperature set value. As a result, the temperature of the Peltier element cannot be controlled, and in the worst case PD
There is a problem that A becomes abnormal temperature and is broken or deteriorated.

Further, even if the temperature is once controlled to an abnormal setting even if it does not lead to destruction, even if the CPU returns to a normal state and a normal PWM signal is output, it takes a long time to control, and the driver needs to be controlled. There is a problem that a load is applied and power is wasted. The present invention has been made in order to solve such a problem, and provides a temperature control circuit for extending the life of a temperature-controlled member (PDA in this embodiment) even when a normal signal is not output from a CPU. Is to do.

[0006]

According to the present invention, a CPU for outputting a temperature control signal as a PWM (Pulse Width Modulation) signal and a PWM signal and an output signal from a temperature sensor are provided. In a temperature control circuit including a comparator to be compared and a driver for driving a temperature control element based on the output of the comparator, when a normal temperature control signal such as a reset state or an abnormal state is not output from the CPU, a normal temperature is output. Until a control signal is output, provisional temperature setting means for providing a provisional control signal to the temperature control element in the vicinity of a set temperature or in a range not to be destroyed is provided.

[0007]

The temporary temperature setting means outputs a normal temporary control signal in place of the CPU and controls the temperature of the PDA until a normal PWM signal is output from the CPU.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of an embodiment of the present invention. In this example, a frequency divider 10 is used as temporary temperature setting means. As shown in FIG. 1, a clock supplied to the CPU is used for the frequency divider 10, and the frequency is divided to
The PWM is the same as the normal PWM signal of the PU. When the PWM setting signal is, for example, 1 kHz and the duty is 3
When the frequency is 0% to 70% and the center is 50%, division is performed by a frequency divider in accordance with the signal. For example, when the clock is 1 MHz, the frequency divider is 1/1000, and 1 kHz is 50%.

FIG. 2 shows the output of the CPU 1 and the two outputs from, for example, the temporary temperature setting means 10 shown in FIG. 1 having different resistances (in the embodiment, 100Ω on the output side of the CPU and the temporary temperature setting means 10).
Are output to the digital IC 11 via 10 kΩ), and the output of the digital IC is input to the LPF.

Such a configuration utilizes the fact that the CPU generally has a high impedance in an abnormal state and a low impedance in a normal state. When the CPU is in an abnormal state, the signal from the provisional temperature setting means 10 has priority, and Then C
The signal from PU1 has priority, and the switching is performed automatically.

FIG. 3 shows an example in which the output of the CPU 1 and, for example, both outputs from the provisional temperature setting means 10 shown in FIG. In this case, the switch 13 is switched according to the output level of the CPU. That is, when the CPU is operating, it is set to the high level and connected to the CPU side.
When the PU is not operating, there is no signal output, so that it is switched to the temporary PWM side as a low level.

FIG. 4 shows signal determining means 14 for determining whether or not a signal from the CPU is normal.
The switch 13 is switched on the basis of the output of. In the signal determination, for example, it is determined whether or not the signal has a certain period. Here, an example of the determination means is shown in FIG.
(A) and (b) are conceivable. In FIG. 1A, 14a and 14a 'are monostable multivibrators, 14b is a flip-flop, 14c is an inverting inverter, and 14d is an AND element.

Table multivibrators 14a, 14
a 'outputs a signal of a determined pulse width by detecting the rise of the input (PWM) signal, and the inverting inverter 14c inputs the inverted signal to the flip-flop. In this case, the monostable multivibrators 14a and 14a '
(B), the output of the inverting inverter 14c is as shown in (b) of FIG. B (in FIG. (B), the PWM signal width changes).

With such a configuration, when the PWM duty changes, the D input level at the time of the rising of the flip-flop clock (inverted output of PWM) is checked in a short check. Normally, a low level (A
If the PWM signal becomes abnormally short, a high level is detected in the A 'section and an error is determined (using the flip-flop inverted output Q).

Similarly, in the long check, normally, a high level (part B) as shown in FIG. 2D is detected (the flip-flop output is high). However, if the PWM signal becomes abnormally long, the B 'part becomes abnormal. Detects a low level and determines an error (using the Q output of the flip-flop).

FIG. 6 shows a configuration in which a window comparator 15 for judging the output of the LPF 2 is provided. The analog output of the LPF 2 is output to one input terminal of the window comparator 15, and the LPF 1 as a comparison signal is output to the other input terminal. A signal from the analog signal generating means 16 for generating a normal analog signal to be input is input and the two signals are compared.

When there is no difference between the two signals, the switch 13 selects the signal from the LPF 2, and when there is a difference, the switch 13 selects the signal from the analog signal generating means 16. That is, when the normal value of the output voltage of the low-pass filter is 1 to 4 V, it is determined whether the output voltage is 1 V or more.
It is sufficient if there is a window comparator that determines whether the voltage is equal to or less than V.

According to the configurations shown in FIGS. 1 to 6, backup can be performed when the CPU is in a reset state or the CPU is abnormal and a normal PWM signal is not output. As a result, it is possible to realize a temperature control circuit with a long life of the photodiode. It should be noted that the foregoing description of the invention merely illustrates certain preferred embodiments for purposes of explanation and illustration. Thus, it will be apparent to one skilled in the art that the present invention may be modified or modified in many ways without departing from its essentials. The scope of the present invention defined by the description in the claims section is intended to cover alterations and modifications within the scope.

[0019]

As described above, according to the present invention, a CPU that outputs a temperature control signal as a PWM (pulse width modulation) signal, a comparator that compares the PWM signal with an output signal from a temperature sensor, In a temperature control circuit including a driver for driving a temperature control element based on the output of the comparator, a normal temperature control signal is output when a normal temperature control signal is not output from the CPU due to a reset state or an abnormality. In the meantime, the provisional temperature setting means for providing the temperature control element with a provisional temperature control signal in the vicinity of the set temperature or in a range where the temperature is not destroyed is provided, so that the CPU is reset or abnormal, and the normal PWM signal is not output. In this case, a backup can be performed, and a temperature control circuit with a longer life of the PDA can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a provisional temperature setting unit according to the present invention.

FIG. 2 is a diagram showing a configuration example of a switching unit for switching an output of a CPU and an output of a provisional temperature setting unit.

FIG. 3 is a diagram illustrating a configuration example of a switching unit for switching an output of a CPU and an output of a provisional temperature setting unit;

FIG. 4 is a diagram illustrating an example of switching between an output of a CPU and an output of a provisional temperature setting unit using a determination unit.

FIG. 5 is a diagram illustrating an example of a determination unit in FIG. 4;

FIG. 6 is a diagram showing another example of switching between the output of the CPU using the determination means and the output of the provisional temperature setting means.

FIG. 7 is a diagram showing a conventional example of a temperature control circuit of a spectrum monitor.

[Description of Signs] 1 CPU 2 Low-pass filter (LPF) 3 Comparator 4 Photodiode array (PDA) 5 Temperature control element 6 Temperature sensor 7 Driver 11 Divider 12 Digital IC 13 Switch 14 Signal judgment means 15 Window comparator 16 Analog Signal generation means

Claims (7)

[Claims] 1. A CPU for outputting a temperature control signal as a PWM (pulse width modulation) signal, a comparator for comparing the PWM signal with an output signal from a temperature sensor, and a temperature control element based on an output of the comparator. When a normal temperature control signal is not output from the CPU due to a reset state or an abnormal condition, the temperature control circuit including a driver for driving the temperature control element sets the temperature to the temperature control element until a normal temperature control signal is output. And a provisional temperature setting means for providing a provisional temperature control signal in the vicinity of or within a range not destroyed. 2. The temperature control circuit according to claim 1, wherein said PWM signal is inputted to analog signal conversion means, converted into an analog signal and then inputted to said comparator. 3. The temporary temperature setting means is provided outside the CPU and externally supplies a PWM signal to the temperature control element in the vicinity of a set temperature or in a range where the temperature is not destroyed. Temperature control circuit as described. 4. The system according to claim 1, wherein switching between the setting PWM signal from the CPU and the PWM signal from the provisional temperature setting means is performed from the CPU after the CPU operates normally. Temperature control circuit. 5. The temperature control circuit according to claim 1, wherein switching between a setting PWM signal from said CPU and a PWM signal from said provisional temperature setting means is performed externally. 6. A signal judging means for judging whether or not the signal of the CPU is in a normal range, and based on an output signal from the signal judging means, a PWM signal from the temporary temperature setting means is converted to a PWM signal of the CPU. 2. The temperature control circuit according to claim 1, wherein the temperature control circuit is configured to switch to the temperature control circuit. 7. A signal judging means for judging whether or not a signal of said analog signal converting means is within a normal range, wherein said analog signal converting means has a normal visual signal based on an output signal from said signal judging means. 2. The temperature control circuit according to claim 1, wherein a signal from an analog signal generating means for outputting a signal similar to that in a state is switched.