Why Overvoltage Protection Innovation is Needed

Exposure to lightning and switching transients, weak regulations for line voltage in remote or developing areas and grid inconsistencies around the globe make circuit protection a necessity for any device connected to AC/DC power lines. Designers know that selecting the right overvoltage protection is no easy task. First, no single solution fits every application or will satisfy UL 1449 certification. Plus, increasing application density and complexity make it more difficult to address all circuit protection concerns.

One popular solution used for many years in countless devices is the MOV. Even with its high current handling, high current absorption, and fast reaction time, MOVs have a well-known flaw. MOVs degrade and can fail from long-term overvoltage exposure. Degradation to the zinc oxide structure of the MOV causes its varistor voltage to decrease resulting in higher levels of leakage and watt-loss heating. Ultimately, the decreased varistor voltage, increased leakage and a compromised ability to dissipate heat triggers the MOV to enter a thermal runaway condition that ends its operational life.  These threats have led UL to require extensive testing to guard against possible harmful failure modes. Applications subjected to voltage transients need more protection than a MOV alone can provide – it was time to innovate.

Bourns has engineered an enhanced overvoltage protection solution. Our new hybrid GMOV™ device is the first single component to combine the technology of an MOV and a GDT based on Bourns® space-saving FLAT® technology. This breakthrough solution meets higher density design size restrictions and is also a drop-in replacement for 14 mm and 20 mm MOVs. It also delivers the increased reliability needed in clamping voltage transients with the added advantages of low leakage, energy savings and low capacitance to help extend an application’s lifespan.


The GMOV™ works by keeping the MOV isolated from the line, basically “on-call, but not on-duty”. The GDT shields the MOV from transients and temporary overvoltage spikes that typically damage the MOV over time. Leakage of the device is eliminated by the series GDT and mitigates damage of the MOV due to watt loss heating.

The reduced leakage current with a GMOV component makes it particularly appealing for ENERGY STAR® applications, especially in the presence of voltage stress. Reduced leakage current and constant capacitance of the GDT make it optimal for power line communications. And, the capacitance level advantages achieved with the GMOV™ device allow power line communications to attain acceptably high data rates.

gmov_logo_animation07_longGMOV™ overvoltage hybrid components are recognized to UL 1449, Issue 4, type 5, which takes the guesswork out of pairing discrete MOVs and GDTs as many surge strips and SPDs use both devices. Plus, the GDT function in the GMOV™ component allows for better performance on lost neutral testing, and greatly simplifies UL listing of end products.

Because overvoltage protection for reliability and safety remains a constant requirement, what could be easier than specifying a GMOV™ component as a direct MOV replacement that reduces both concerns.

ENERGY STAR® is a registered U.S. trademark.


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