US 4,906,820 AGranted

Temperature control method and circuit for controlling the temperature in a heatable compartment of an appliance

AssigneeMemmert GmbH & Co. KG

InventorsPeter Haarmann, Heinz Kusebauch

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Abstract

The invention relates to a temperature control method and to a temperature control circuit. In a measured value detecting member (2) a measuring voltage (U.sub.TH) is generated which is representative of the actual temperature. In an adjustment member (1), a desired voltage (U.sub.S) is generated which is representative of the desired temperature. A difference former (inverse adder 5) determines from the measuring voltage (U.sub.TH) and the desired voltage (U.sub.S) a deviation voltage (U.sub.D) which corresponds to the deviation between the desired temperature and the actual temperature. The heating power of the heating element (14) of the temperature control circuit is regulated proportionately in dependence on the deviation voltage (U.sub.D) by shifting the phase angle (.phi.). During each line half-wave (27), the deviation voltage (U.sub.D) is compared in a comparator (comparator 11) with the descending edge voltage of a line-synchronous delta voltage (U.sub.DS). Beginning with the point in time at which these two voltages (U.sub.D and U.sub.DS) are identical, the comparator (comparator 11) generates an output signal which controls the position of the phase angle (.phi.).

Claims7

Dependent claims

In a method for controlling temperature in a compartment of an appliance, the compartment being heated by a heating element supplied with heating power by line voltage regulated by a controllable switch which can be turned on at a controllable phase angle of the line voltage, comprising:

generating a measuring voltage representing an actual temperature in the compartment;
generating a desired voltage representing a desired temperature in the compartment;
forming a difference between the desired voltage and the actual voltage to obtain a deviation voltage representing a deviation between the desired temperature and the actual temperature;
shifting the phase angle of the controllable switch in proportion to the deviation voltage;
generating from the line voltage a line-synchronous delta voltage having a waveform presenting descending edge region;
comparing the deviation voltage with the descending edge region of the line-synchronous delta voltage during each half wave of the line voltage;
and
generating an output signal which controls the position of the phase angle for turning on the controllable switch from the time when the amplitudes of the desired voltage and the actual voltage have the same amplitude, the improvement wherein:
said step of generating a line-synchronous delta voltage includes generating a line-synchronous delta voltage having a waveform presenting:
(1) a first descending edge region which has a relatively large voltage drop per unit of time down to a limit voltage when the deviation voltage is below a settable voltage threshold;
and (2) a second descending edge region following in time the first descending edge region which has a relatively small voltage drop per unit of time.

8 more elements

In a temperature control circuit for controlling temperature in a compartment of an appliance, comprising:

a temperature-to-voltage converter means for generating a measuring voltage representing an actual temperature in the compartment;
an adjustable voltage source for generating a desired voltage representing a desired temperature in the compartment;
a difference former means connected to said temperature-to-voltage converter means and said voltage source for forming a difference between the desired voltage and the actual voltage to obtain a deviation voltage representing a deviation between the desired temperature and the actual temperature;
heating element means for heating the compartment;
controllable switch means connected to said heating element means and like voltage for proportionally regulating power to said heating element means by switching on the line voltage at a controlled phase angle of the line voltage;
delta voltage means for generating from line voltage a line-synchronous delta voltage having a waveform presenting a descending edge region;
comparator means connected to said difference former means and said delta voltage means for comparing the deviation voltage with the descending edge region of the line-synchronous delta voltage during each half wave of the line voltage and generating an output signal which controls the position of the phase angle for turning on the controllable switch from the time when the amplitudes of the desired voltage and the actual voltage have the same amplitude;
the improvement wherein:
said delta voltage means comprises means for generating a line-synchronous delta voltage having a waveform presenting:
(1) a first descending edge region which has a relatively large voltage drop per unit of time down to a limit voltage when the deviation voltage is below a settable voltage threshold;
and (2) a second descending edge region following in time the first descending edge region which has a relatively small voltage drop per unit of time.

8 more elements

Dependencies are inferred from the claim text.