(2) Temperature regulating electric blanket. This kind of electric blanket overcomes the disadvantage that ordinary electric blanket cannot adjust the temperature, and a temperature regulating device is added to the circuit. According to the different temperature regulating principles, the temperature regulating electric blanket can be divided into the following categories:
① A temperature regulating electric blanket that changes the resistance of electric heating elements. This electric blanket adopts two groups of electric heating wires with the same length and wire diameter, which are sewn on the flexible fabric in a parallel and alternating manner. The connection mode of the two groups of electric heating wires is changed by the change-over switch, that is, the impedance of the circuit is changed, so as to achieve the purpose of temperature regulation. This electric blanket is generally equipped with four gears: high temperature, medium temperature, low temperature and neutral. The power ratio of the first three gears is 4:2:1. When using, the high temperature gear can be used to preheat and heat up. When sleeping, the change-over switch can be placed in the medium temperature gear or low temperature gear according to the different temperature requirements of individuals. In this way, the appropriate temperature can be obtained and electricity can be saved. However, when this electric blanket is used in the middle temperature range, the heating is not uniform enough, and the temperature of different parts is also different.
② Diode half wave rectification temperature regulating electric blanket. On the basis of ordinary electric blanket, a rectifier diode is connected in series in the circuit. It uses the half wave rectification characteristic of diode to reduce the power and achieve the purpose of temperature regulation. The power ratio of high temperature gear and low temperature gear is 2:1, which can be selected as required.
This electric blanket has simple manufacturing process and uniform heating. It is one of the most widely produced and used in China. Its disadvantage is that it interferes with AM radio to some extent.
(3) Capacitive temperature regulating electric blanket. A capacitor is connected in series in the control circuit of an ordinary electric blanket. The temperature is adjusted by adjusting the capacitance, changing the circuit capacitance reactance, and then changing the circuit power consumption. When the electric blanket works, it will not interfere with the radio, but it is large in size, high in cost and poor in safety.
(4) Transformer voltage regulating electric blanket. It is used to reduce 220V voltage to safe voltage of 36V or below through transformer. The secondary of the transformer has multiple taps. The working voltage (12V, 16V, 20V, 24V, etc.) is obtained on different taps to supply the electric blanket. The purpose of temperature regulation is achieved by using the different working voltages. The electric blanket is safe because the working voltage is within the safe voltage range. However, due to the addition of transformers, the cost of products has been increased, and the weight and power consumption have also been increased.