JPH0360863A - Temperature control circuit for soldering iron - Google Patents

Abstract

PURPOSE:To convert a secondary voltage by the mere regulation of the capacity of a capacitor and to prevent overheating by connecting the capacitor in parallel after half-wave rectification of a primary voltage by a diode, then, regulating the output voltage of the secondary voltage. CONSTITUTION:The capacitor 3 is connected in parallel after the half-wave rectification of the primary voltage 1 by the diode 2. A switch 4 is so formed as to be automatically changed over to a low-pressure side when an iron is placed at the time of the pause of a soldering operation. Since the capacity of the capacitor 3 is large, an electrolytic capacitor is used. While the conversion of the secondary voltage is heretofore not possible except when a transformer is used, the free conversion of the primary 100V to secondary 50V to 110V is possible by the mere regulation of the capacitor in this way. The conduction of the soldering operation is possible without overheating even if the iron is rested for 2 hours with secondary output 80V.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overheating prevention circuit for an electric soldering iron.There have been various applications for preventing overheating of soldering irons, but many of them have complex structures and have not been put to practical use. Further, although the half-wave rectification method using diodes has a simple circuit, the secondary output voltage is as low as 40-odd volts, and the soldering iron tip temperature rises slowly during soldering work due to insufficient heating, making it impractical.

This invention solves the problem of voltage adjustment after half-wave rectification using diodes in a simple manner.

To explain with a diagram, in Figure 1, the primary voltage (1) is half-wave rectified by a diode (2), and then a capacitor (3) is connected in parallel. The switch (4) is designed to automatically switch to the low pressure side when the soldering iron is put down when the soldering work is stopped. An electrolytic capacitor is used because the capacitor (3) has a large capacity. The soldering iron tip capacity often used for general electronic circuit wiring is of the 20W type. Taking a load of 20W as an example, the capacitance of the electrolytic capacitor (3) is 10μF and the DC output is approximately 60V1.
An output voltage of 70V at 3μF and around 80V at 15μF can be obtained. The practical voltage for preventing overheating of the iron tip is 60V to 80V. Below 60V, there will be insufficient heating, and above 80V, there will be overheating. If you want to increase the high voltage during soldering work to 100V or more, install a diode (6) as shown in Figure 2 and increase the capacitance of the electrolytic capacitor (7) to 50μF or more.
V~110V is obtained. Normally, 100V AC is directly connected.

When the load changes to more than or less than 20W, the output voltage also changes, and at 40W, 80V drops to 60V. To accommodate this, the capacitor capacity can be adjusted. As shown in Figure 3, several capacitors (3) are connected in parallel and adjusted as desired using a selector switch (8).

As described above, the temperature control circuit of the present invention converts the primary voltage to 100 V by simply adjusting the capacitance of the capacitor, whereas conventionally the secondary voltage could only be converted by using a transformer.
The secondary voltage can be freely converted from 50V to 110V.

Even if you leave it for 2 hours with a secondary output of 80V, you can solder in the best conditions without heating up.

[Brief explanation of drawings]

1...Primary voltage 2...Diode 3...Capacitor 4...High/low selector switch 5...Secondary voltage 6.
...Diode 7...Capacitor 8...Capacitor selection switch

Claims (1)

[Claims] After half-wave rectification of the primary voltage (1) using a diode (2), a capacitor (3) is connected in parallel to create the secondary voltage (5).
A temperature control circuit for soldering irons that adjusts the output voltage of the soldering iron.