Varistors: Essential Protection for Electronic Circuits
Varistors are critical components in modern electronics, safeguarding circuits from voltage spikes and surges. Whether you're an engineer, buyer, or hobbyist, understanding these devices can help you make informed decisions for your projects.
How to Find Reliable Varistors from China in 2025
China remains a leading manufacturer of varistors, offering competitive pricing and quality. To ensure reliability:
- Verify supplier certifications (ISO, RoHS)
- Request sample testing reports
- Check customer reviews on platforms like Alibaba
- Confirm MOQ and lead times
Top Chinese manufacturers have invested in automated production lines, improving consistency in 2024-2025.
What Buyers Should Know Before Buying Varistors from China
Key considerations include:
- Clamping voltage specifications
- Response time (nanoseconds matter)
- Operating temperature range
- Packaging standards for shipping
Always request datasheets in English and confirm warranty terms. Payment terms (30% deposit) are common for first-time buyers.
Types of Varistors
Main varistor types include:
- MOV (Metal Oxide Varistors) - Most common for AC circuits
- Silicon Carbide - Older technology, still used in high-energy applications
- Polymer-based - Flexible circuits and wearable electronics
- MLV (Multilayer Varistors) - For low-voltage DC circuits
Functions and features of Varistors
Varistors function as voltage-dependent resistors with these key features:
- Non-linear resistance characteristics
- Fast response to voltage spikes (under 25ns)
- Energy absorption up to several hundred joules
- Self-resetting after transient events
They're often called "voltage clamping" devices for their ability to limit voltage to safe levels.
Scenarios of Varistors
Common applications include:
- Power supply input protection
- Telecommunications equipment
- Industrial motor controls
- Consumer electronics (TVs, appliances)
- Automotive electronics
A 2024 study showed 78% of power supply failures could be prevented with proper varistor protection.
How to Choose Varistors
Selection criteria:
- Determine maximum continuous operating voltage
- Calculate expected surge current
- Consider energy absorption requirements
- Evaluate physical size constraints
- Check agency approvals (UL, CE)
For LED drivers, a 20mm disk varistor with 275V rating is typical.
Varistors Q & A
Q: How long do varistors typically last?
A: Properly rated varistors can last 5-10 years, but should be replaced after absorbing major surges.
Q: Can varistors prevent all electrical damage?
A: No, they protect against voltage spikes but not sustained overvoltage conditions.
Q: What's the difference between SMD and through-hole varistors?
A: SMD versions are for automated assembly while through-hole offers easier manual replacement.
Q: How do I test a varistor?
A: Use a multimeter to check resistance (should be very high at normal voltages).
Q: Why do some varistors fail short circuit?
A: This is a design feature - failing short helps blow fuses and disconnect power during extreme events.
