Overheat protection circuit

DC switching power supply in the high integration of switching regulators and lightweight small volume, so that the power density within the unit volume greatly increased, so if the internal components of the power supply unit to its operating environment temperature requirements do not improve, will inevitably make the circuit performance deterioration, premature failure of components. Therefore, in high-power DC switching power supply should be set over the thermal protection circuit. In this paper, the temperature relay is used to detect the internal temperature of the power supply device, when the power supply device internal overheating, temperature relay on the action, so that the alarm circuit in the alarm state, to achieve the power supply overheating protection. As shown in Figure 5 (a) Type control Gate Gejin Gate is placed near the power switch transistor, according to the characteristics of the TT102 (by the RR value to determine the device's conduction temperature, the larger the RR, the lower the conduction temperature), when the power tube shell temperature or the temperature inside the device exceeds the allowable value, the Gejin thyristor on the conduction, so that the light emitting diode lights alarm. If cooperate with the photoelectric coupler, can make the whole machine alarm circuit action, protect the switching power supply. The circuit can also be designed as shown in Figure 5 (b), as a power transistor overheating protection, the base current of the crystal Switch tube is the N-type control gate Gejin Gate TT201 Bypass, switch tube cutoff, cut off the collector current, prevent overheating.