JPS6138492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for electric heating appliances such as electric blankets and electric floor heaters.
The object of the present invention is to provide an electronic control device in which noise generation is suppressed by performing visual zero-cross triggering of a power control element.

Taking a conventional electric blanket temperature control device as an example, it will be explained with reference to FIGS. 1 to 3.

FIG. 1 shows an example of a conventional circuit diagram of a temperature control device.
V _AC is an alternating voltage. 2 is a temperature-sensitive heater in which the heater and sensor are integrated; 3 is the heater; 4 is the temperature-sensitive heater;
is a sensor such as a plastic thermistor, 5
is the temperature sensing electrode wire. The heater 3 is powered during the positive half cycle of the alternating current voltage V _AC by the conduction of the power control element 6 . Further, the resistance value of the sensor 4 changes depending on the temperature of the heater 3, and during the negative half cycle period of _{the AC} voltage VAC, the sensor 4 flows from the temperature detection electrode wire 5 toward the heater 3. The current is detected by a signal detection circuit 8 made up of a transistor 7 and taken out as a collector current _I.sub.C. Therefore, the collector current I _C has a half wave waveform, and as the heater temperature increases, the resistance value of the sensor 4 decreases, so the value of the collector current I _C increases. Furthermore, since the sensor 4 exhibits capacitive impedance, the collector current I _C has a waveform that is advanced by 90 degrees from the negative half cycle of the AC voltage V _AC . 9 is a protection diode for the transistor 7. diode 1
0, a resistor 11, and a capacitor 12, a low voltage DC voltage V _CC for the control circuit is obtained from the AC voltage V _AC . The collector current I _C is the capacitor 13
and is integrated by an integrating circuit 15 consisting of a resistor 14,
It is input to the comparator circuit 16 as a DC temperature signal voltage V _T . Reference numeral 17 denotes a zero-cross pulse generation circuit that generates a zero-cross pulse V _Z in synchronization with the AC voltage V _AC . Reference numeral 18 denotes a temperature setting circuit, which is composed of a resistor 19 and a temperature setting volume 19', and obtains a temperature setting voltage V _S . 20 is resistance,
Reference numeral 21 denotes a transistor, and when the zero-crossing pulse generation circuit 17 is not generating the zero-crossing pulse V _Z , the transistor 21 is turned on, and the output V _O of the comparing circuit 16 is kept low. When the zero cross pulse V _Z is generated, the transistor 21 is turned off, and during that period, the comparison circuit 16 compares the temperature setting potential V _S and the temperature signal voltage V _T . Therefore, when the temperature of the heater 3 has not reached the set temperature, V _T >V _S and a pulse V _O of the same type as the zero cross pulse is output from the comparison circuit 16, triggering the power control element 6 at the zero cross. Electric power is supplied to the heater 3 to raise the temperature to a set temperature. 22 is a limiting resistor, and 23 is a gate resistor.

FIG. 2 shows an operational waveform diagram of each part in the above configuration. The period from time t ₁ to time _{t 5} is a period in which the heater temperature does not reach the set temperature, and the power control element is triggered to supply power to the heater during the half cycle period in which the AC voltage V _AC is positive. During the period starting from time t ₆ , the heater temperature has reached the set temperature and the power control element is not triggered.

In the above conventional configuration, the temperature signal voltage V _T and the temperature set voltage V _S are directly compared in the comparator circuit 16 during the zero-crossing period, so there is a drawback that phase control is required when the heater temperature is near the set temperature. Ta.

FIG. 3 shows an enlarged view of the waveform of section A at time _t4 in FIG. 2, and the above-mentioned drawbacks will be explained. Temperature setting voltage V
As shown in the figure, _S has a rectangular waveform that falls during the zero-cross pulse period, but at that time, the temperature signal voltage V _T is held while gradually discharging the charge accumulated in the capacitor 13 of the integrating circuit 15 through the resistor 14. Because of this, it draws a slight upward curve to the right. Therefore, when V _S and V _T are close to each other, a period where V _T >V _S always occurs on the right side as shown in period B, so the output pulse V _O of the comparator circuit 16 rises on the positive side of the AC voltage V _AC . It generates a thin rising pulse and performs phase control.

With electric blankets like the one shown in this application example, you often listen to FM broadcasts while sleeping, so
The generation of noise, even if it is minute, is a serious drawback.

The present invention solves the above-mentioned drawbacks by stopping the discharging of the integrating circuit during the zero-crossing pulse generation period. An embodiment of the present invention will be described below with reference to FIGS. 4 to 7.

FIG. 4 shows an embodiment of the temperature control device according to the present invention. The difference from FIG. 1 is that a discharge stop circuit 25 consisting of a transistor 24 is provided. The transistor 24 is turned on via the resistor 26 when the zero cross pulse V _Z is not generated.
The operation is the same as that shown in FIG. 1, but the transistor 24 is turned off during the period when the zero cross pulse V _Z occurs and the temperature setting voltage V _S and the temperature signal voltage V _T are compared in the comparator circuit 16. , capacitor 13
stop discharging. Therefore, as shown in Figure 5,
During the period, the temperature signal voltage V _T does not change;
Therefore, even if V _S and V _T are close to each other, a period of V _T >V _S will not occur on the right side, and phase control will not occur.

FIG. 6 shows another embodiment of the temperature control device according to the present invention, which is further improved. The difference from Figure 4 is that
The point is that an integral energizing circuit 28 consisting of a resistor 27 is provided. When the zero-cross pulse V _Z is not generated, the transistor 24 is turned on and the charge in the capacitor 13 is gradually discharged through the resistor 14 as in FIG. 4, but when the zero-cross pulse V _Z is generated, the transistor 24 is turned on. OFF, so even if collector current I _C is not flowing, resistor 14 and resistor 27
Since integration is performed on the capacitor 13 via the voltage V T , the temperature signal voltage V _T during the period draws a downward-sloping curve as shown in FIG. Therefore, when V _S and V _T are close to each other, V _T >V _S from the left side will always hold, so it is possible to perform a reliable zero cross trigger that is not affected by even a small amount of noise. Furthermore, since the operating time of the integral energizing circuit is extremely short, there is no fear that the temperature signal voltage V _T will be significantly shifted due to some integration during that time.

As described above, the present invention has a configuration in which the discharge stop circuit stops the discharge of the integrating circuit that obtains the temperature signal voltage during the zero-cross pulse generation period in which the temperature signal voltage and the temperature setting voltage are compared. The temperature signal voltage and the temperature setting voltage can be accurately compared, and therefore a stable zero cross trigger pulse can be obtained as a comparison output.
Furthermore, during the operation period of the discharge stop circuit, the integral energizing circuit causes the integrating circuit to perform integration, so that the comparative output can be reliably generated from before the zero cross point, so that it is not affected by even slight noise. This allows reliable zero cross triggering.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional temperature control device, Fig. 2 is an operation waveform diagram of each part in Fig. 1, Fig. 3 is an enlarged waveform diagram of section A in Fig. 2, and Fig. 4 is a temperature control device according to the present invention. A circuit diagram of one embodiment of the control device, FIG. 5 is an enlarged waveform diagram corresponding to part A of FIG. 3 in the configuration of FIG. 4, and FIG. 6 is a circuit diagram of another embodiment of the temperature control device of the present invention. 7 are enlarged waveform diagrams corresponding to section A of FIG. 3 in the configuration of FIG. 6. 2...Temperature sensitive heater, 3...Heater, 4...Sensor, 5...Temperature detection electrode wire, 6...Power control element, 8...Signal detection circuit, 15...Integrator circuit, 1
6... Comparison circuit, 17... Zero cross pulse generation circuit, 18... Temperature setting circuit, 21... Transistor, 25... Discharge stop circuit, 28... Integral activation circuit, V _AC ... AC voltage, V _CC ...DC voltage for control circuit, I _C ...Collector current, V _H ...Anode voltage of power control element 6, V _T ...Temperature signal voltage,
V _Z ...Zero cross pulse, V _S ...Temperature setting voltage, V _O ...Zero cross trigger pulse.

Claims (1)

[Claims] 1. A load such as a heater, and a power control element that controls power supply to the load in a half cycle of alternating current;
a sensor that detects the load temperature; a signal detection circuit that detects a signal of the sensor in the other half cycle of the half cycle in which power is supplied to the load;
an integrating circuit that integrates and holds the output of the signal detection circuit; a temperature setting circuit that sets the operating temperature of the load; a zero-crossing pulse generation circuit that generates a pulse at a zero-crossing point of the AC voltage; and the integrating circuit and the temperature. a comparison circuit that compares the output of a setting circuit and energizes or deenergizes the power control element in synchronization with the zero-cross pulse; and a discharge stop circuit that stops discharging the integrating circuit in synchronization with the zero-cross pulse. A temperature control device characterized by comprising: 2. The temperature control device according to claim 1, further comprising an integration energizing circuit that causes the integration circuit to perform integration during the operation period of the discharge stop circuit.