FIELD

The disclosure relates to a composite circuit protection device, and more particularly to a composite circuit protection device having a voltage-dependent resistor sandwiched between two positive temperature coefficient (PTC) components.

BACKGROUND

U.S. Pat. No. 8,508,328 B1 discloses an insertable polymer positive temperature coefficient (PPTC) over-current protection device that includes first and second electrodes30, a solder material, conductive lead pins50,60bonded to the first and second electrodes30, respectively, and a PTC polymer matrix20laminated between the first and second electrodes30(seeFIG. 1). The PTC polymer matrix20is formed with a hole40that has an effective volume to accommodate thermal expansion of the PTC polymer matrix20at increased temperature.

Electrical properties (e.g., operating current and high-voltage surge endurability) are important factors which affect the occurrence of power surge in the PPTC over-current protection device. For example, an increase in the thickness or the area of the PTC polymer matrix20allows the operating current of the PPTC over-current protection device to be increased, which might result in the PPTC over-current protection device becoming more vulnerable to power surge. On the other hand, a decrease in the thickness or the area of the PTC polymer matrix20allows the high-voltage endurability of the PPTC over-current protection device to be increased, which does not necessarily makes the PPTC over-current protection device less vulnerable to power surge.

Although a voltage-dependent resistor (VDR)could be combined with the PPTC over-current protection device to impart over-current and over-voltage protection to the resultant composite circuit protection device, the (VDR) might only withstand power surge for a short time period (such as 0.001 seconds). That is, if a time period of the power surge exceeds a cut-off time period, the (VDR) might be burned out or damaged due to over-current and over-voltage, causing permanent loss of function of the composite circuit protection device.

SUMMARY

Therefore, an object of the disclosure is to provide a composite circuit protection device that can alleviate at least one of the drawbacks of the prior art.

According to the disclosure, a composite circuit protection device includes a first positive temperature coefficient (PTC) component, a second PTC component, a voltage-dependent resistor, a first conductive lead, a second conductive lead, and a third conductive lead.

The first PTC component includes a first PTC layer having two opposite surfaces, and first and second electrode layers respectively disposed on the two opposite surfaces of the first PTC layer.

The second PTC component includes a second PTC layer having two opposite surfaces, and third and fourth electrode layers respectively disposed on the two opposite surfaces of the second PTC layer.

The voltage-dependent resistor is connected to the second electrode layer of the first PTC component and the third electrode layer of the second PTC component.

The first conductive lead is bonded to the first electrode layer of the first PTC component. The second conductive lead is bonded to the voltage-dependent resistor. The third conductive lead is bonded to the fourth electrode layer of the second PTC component.

