GB2150713A

GB2150713A - Temperature regulator

Info

Publication number: GB2150713A
Application number: GB08332326A
Authority: GB
Inventors: Leonid Alexandrovich Griffen; Vladimir Filimonovich Ogolenko; Viktor Stepanovich Vititin; Viktor Semenovich Belyankin; Pavel Andreevich Stepashko; Valentin Nikiforovic Nikiforov
Original assignee: KI Z ELEKTROBYTPRIBOR; NII PERERABOTKE ISKUSSTVENNYKH
Current assignee: KI Z ELEKTROBYTPRIBOR; NII PERERABOTKE ISKUSSTVENNYKH
Priority date: 1983-12-03
Filing date: 1983-12-03
Publication date: 1985-07-03
Also published as: GB8332326D0; GB2150713B

Abstract

A temperature regulator comprises a temperature-sensitive bridge whose one branch is formed by the heating element (1). An input diagonal of the bridge is connected to a power source, while an output diagonal is connected to a controlled rectifier (5). The heating element (1) is connected to the power source via the controlled rectifier (5). A bridge branch (3) which is situated opposite to the branch formed by the heating element (1) is shunted by a positive feedback device (6) whose input is electrically connected to the output diagonal of the temperature- sensitive bridge. <IMAGE>

Description

SPECIFICATION Temperature Regulator This invention relates to electrical devices for regulating temperature and, in particular, to thermoregulators.

The present invention is suitable for use in various household heating appliances where a specific temperature is to be maintained.

It is an object of this invention to provide a more accurate thermoregulator.

The present invention provides a thermoregulator comprising a temperature-sensitive bridge whose one branch is formed by a heating element and whose input diagaonal is connected to a power source, and a controlled rectifier having the input thereof connected to an output bridge diagonal and thus being the element through which the heating element is connected to the power source, and a positive feedback device connected across that branch of the temperature sensitive bridge, which is opposite to the branch formed by the heating element, the input of the positive feedback device being electrically connected to the output diagonal of the temperature-sensitive bridge.

It is advisable that the branch of the temperature-sensitive bridge, which is opposite to the branch formed by the heating element should comprise two parts, while the positive feedback device should comprise a resistor inserted into the output diagonal of the bridge, a reverse-conducting transistor whose base-emitter junction is connected to the resistor, and a forward-conducting transistor whose base is connected to the collector of the reverse-conducting transistor, the baseemitter junction thereof is connected via a bias resistor to one part of the branch of the temperature-sensitive bridge, which is opposite to the branch formed by the heating element, and the collector-emitter junction thereof is connected to the other part of said branch .

The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, wherein: Figure 1 shows a functional block diagram of a thermoregulator, according to the invention; Figure 2 shows a schematic circuit diagram of a thermo-regulator used, for example, in an electric heater, according to the invention.

A temperature-sensitive bridge of a thermoregulator comprises a heating element 1 (Fig.

1) forming one of the branches and three other branches 2,3 and 4 composed of resistors. The heating element 1 is connected to a power source via a thyristor 5 whose input is coupled with an output diagonal of the bridge. The branch 3 of the temperaturesensitive bridge, which is opposite to the branch formed by the heating element 1, is bypassed by a positive feedback device 6 whose input is connected to the output bridge diagonal.

In a concrete embodiment of a thermoregulator suitable for use in an electric heater the branch 3 (Fig. 2) of the temperature-sensitive bridge comprises two parts. The first part comprises resistors 7 and 8 while the second part has a resistor 9, all connected in series.

An input of the thyristor 5 is connected to the output diagonal of the temperature-sensitive bridge via a resistor 10 coupled to the baseemitter junction of a reverse-conducting transistor 11. The collector of the transistor 11 is connected to the base of a forward-conducting transistor 1 2. The base-emitter junction of the transistor 1 2 is connected via a bias resistor 1 3 to that part of the branch 3 which inciudes the resistor 9, while the emitter-collector junction thereof is connected to the other part of the same branch 3 including the resistors 7 and 8. The temperature-sensitive bridge having a stabilizer diode 14 inserted parallel to the input diagonal thereof takes its power via a capacitor 1 5. The circuit also has two protective diodes 16 and 17.

The thermoreguiator operates as follows.

The temperature-sensitive bridge having a parallel-connected stabilizer diode 1 4 (Fig. 2) and together with the capacitor 1 5 is in fact a voltage divider. Consequently, a limited pulsating or ripple voltage is applied to the input diagonal of the temperature-sensitive bridge, said voltage being shifted in relation to the supply voltage to an angle close to 90 electrical degrees. The bridge can be balanced at a specific temperature by means of the variable resistor 8. When the bridge is balanced, no current is available in the control circuit of the thyristor 5 and said thyristor 5 is inoperative.

A small measuring current passes through the heating element 1 and its temperature goes down. The resistance of the heating element 1 consequently diminishes and the temperaturesensitive bridge becomes unbalanced. The unbalance voltage is generated in the output diagonal of the bridge and produces current in the control circuit of the thyristor 5.The current passes through the resistor 10 which has the base-emitter junction of the transistor 11 connected parallel therewith and produces current in the collector circuit thereof to be then applied to the base of the transistor 11 and the resistor 1 3. When the voltage across the resistor 1 3 produced by said current becomes equal to the voltage across the resistor 9, the transistor 1 2 becomes conductive and shunting the resistors 7 and 8 of the branch 3 of the temperature-sensitive bridge. The bridge becomes still more unbalanced and the current in the control circuit of the thyristor 5 increases.The process builds up as an avalanche until the transistor 1 2 is fully opened and the temperature-sensitive bridge becomes so unbalanced that the current in the control circuit of the thyristor 5 is in excess of the actuating current of the thyristor 5. The thyris tor 5 becomes conductive passing working current through the heating element 1 to be heated to a specific temperature at which the balance of the temperature-sensitive bridge is restored.

During the next half-period of the supply voltage the thyristor 5 remains inoperative and the heating element 1 cools again. The process is then repeated.

The diodes 1 6 and 1 7 protect the measur ing circuit against full supply voltage which can be otherwise applied thereto when the thyristor 5 is cut in.

In this manner the temperature-sensitive bridge acquires a relay-like characteristic and the thyristor 5 functions accurately at the beginning of each half-period of the supply voltage irrespectively of its characteristics and possible variations of voltage. The result is that the circuit does not have to be adapted for each particular thyristor 5 in mass production, no radio interferences are generated when the heating element 1 is cut in, and the circuit operation becomes less dependent on the voltage fluctuations.

Claims

1. A temperature regulator comprising a temperature-sensitive bridge whose one branch is formed by a heating element and whose input diagonal is connected to a power source, a controlled rectifier having its input connected to the output diagonal of said bridge and thus being the element through which the heating element is connected to the power source, and a positive feedback device which shunts that branch of the temperaturesensitive bridge which is opposite to the branch formed by the heating element, the input of the positive feedback device being electrically connected with the output diagonal of the temperature-sensitive bridge.

2. A temperature regulator as claimed in Claim 1, in which the branch of the temperature-sensitive bridge situated opposite the branch formed by the heating element comprises two parts, while the positive feedback device comprises a resistor inserted into the output diagonal of the temperature-sensitive bridge, a reverse-conducting transistor coupled to said resistor by the base-emitter junction thereof, and a forward-conducting transistor whose base is connected to the collector of the reverse-conducting transistor, whose baseemitter junction is connected via a bias resistor to one part of the bridge branch which is opposite to the branch formed by the heating element, while the collector-emitter junction of the forward-conducting transistor is connected, respectively, to the other part of said branch.

3. A temperature regulator substantially as set forth in any one of the preceding Claims and as described herein above with reference to the accompanying drawings.