What was the revenue growth rate of the appliance market for POWI in 2021
 the strong fourth quarter of 2020. Gross margins approached the high end of our model, and our non-GAAP EPS grew 38% from a year ago.
For the full year, non-GAAP EPS grew 92% on revenue growth of 44%. That's well above the revenue growth rate of analog semiconductor industry, which was on track to grow about 30%. Over the past three years, we have averaged 19% top-line growth, almost three times the rate of the analog sector. The revenue growth in 2021 was broad-based and diversified with all four revenue categories growing at least 35%.
We gained share across a broad range of end markets, including appliances, smartphone chargers, notebooks, and a range of verticals in the industrial category. We have strong momentum coming out of 2021, and we could not be more excited about the opportunities ahead of us in 2022 and beyond. The secular trends underpinning our growth last year remained in full effect, including energy efficiency, electrification, smart homes and appliances, and advanced chargers for mobile devices. GaN was a significant contributor to our growth in 2021, with revenues tripling from the prior year, and we expect strong growth again in 2022.
GaN-based InnoSwitch products and complementary products like MinE-CAP are driving a revolution in chargers, and we have a wide range of impressive smartphone and notebook designs coming to market in the months ahead. We also have new revenue streams coming online this year from motor drives as our BridgeSwitch products begin ramping at appliance customers and from automotive with multiple EV design wins going into production later in the year. Our unique foundry model and timely investments in capacity, which enabled us to win market share in 2021, will help us again in 2022 as lead times remain stretched across the industry. Our team executed beautifully last year under challenging conditions, assessing genuine customer needs, building the right mix of parts, and keeping customer lines running while guarding against inventory builds and excess ordering.
Our inventories are nearly back to our target level, and we are in a great position to support strong demand in 2022. We will also introduce new products this year that will extend our lead over the competition while expanding our addressable market. We have a pipeline of products incorporating industry-leading technologies, such as our proprietary GaN switches, FluxLink isolation technology, the BridgeSwitch architecture for motor drive, and our SCALE gate driver technology for high power. In all, we expect to double our addressable market to more than $8 billion over the next five years with the expansion primarily coming from the appliance, industrial, and automotive markets.
We announced one such product earlier this week, a new member of our InnoSwitch three family of ICs, qualified for automotive use. Our InnoSwitch products are rapidly gaining acceptance in EV power supplies, thanks to their efficiency and their high level of integration, which saves precious board space while enhancing reliability. This latest InnoSwitch device designed for next-generation 800-volt EV platforms incorporates a 1,700-volt silicon carbide MOSFET. The challenges of high voltage are new to the automotive market and customers are eager to tap our expertise.
As noted earlier, we have multiple automotive design wins going into production later this year, including an emergency power supply for a Tier 1 automotive supplier. We have additional designs scheduled for production in 2023 and 2024, and a strong pipeline of design activity involving seven of the world's top 11 automakers. While revenues will ramp gradually given the length of automotive design cycles, we are excited about our progress, and we are investing in products, people, and facilities to make automotive a significant part of our business in the coming years. Another new revenue stream for 2022 is motor drives.
Our BridgeSwitch products drive brushless DC motors, which are being adopted by appliance makers to keep pace with the efficiency requirements such as China's n
 the strong fourth quarter of 2020. Gross margins approached the high end of our model, and our non-GAAP EPS grew 38% from a year ago.
For the full year, non-GAAP EPS grew 92% on revenue growth of 44%. That's well above the revenue growth rate of analog semiconductor industry, which was on track to grow about 30%. Over the past three years, we have averaged 19% top-line growth, almost three times the rate of the analog sector. The revenue growth in 2021 was broad-based and diversified with all four revenue categories growing at least 35%.
We gained share across a broad range of end markets, including appliances, smartphone chargers, notebooks, and a range of verticals in the industrial category. We have strong momentum coming out of 2021, and we could not be more excited about the opportunities ahead of us in 2022 and beyond. The secular trends underpinning our growth last year remained in full effect, including energy efficiency, electrification, smart homes and appliances, and advanced chargers for mobile devices. GaN was a significant contributor to our growth in 2021, with revenues tripling from the prior year, and we expect strong growth again in 2022.
GaN-based InnoSwitch products and complementary products like MinE-CAP are driving a revolution in chargers, and we have a wide range of impressive smartphone and notebook designs coming to market in the months ahead. We also have new revenue streams coming online this year from motor drives as our BridgeSwitch products begin ramping at appliance customers and from automotive with multiple EV design wins going into production later in the year. Our unique foundry model and timely investments in capacity, which enabled us to win market share in 2021, will help us again in 2022 as lead times remain stretched across the industry. Our team executed beautifully last year under challenging conditions, assessing genuine customer needs, building the right mix of parts, and keeping customer lines running while guarding against inventory builds and excess ordering.
 Our inventories are nearly back to our target level, and we are in a great position to support strong demand in 2022. We will also introduce new products this year that will extend our lead over the competition while expanding our addressable market. We have a pipeline of products incorporating industry-leading technologies, such as our proprietary GaN switches, FluxLink isolation technology, the BridgeSwitch architecture for motor drive, and our SCALE gate driver technology for high power. In all, we expect to double our addressable market to more than $8 billion over the next five years with the expansion primarily coming from the appliance, industrial, and automotive markets.
We announced one such product earlier this week, a new member of our InnoSwitch three family of ICs, qualified for automotive use. Our InnoSwitch products are rapidly gaining acceptance in EV power supplies, thanks to their efficiency and their high level of integration, which saves precious board space while enhancing reliability. This latest InnoSwitch device designed for next-generation 800-volt EV platforms incorporates a 1,700-volt silicon carbide MOSFET. The challenges of high voltage are new to the automotive market and customers are eager to tap our expertise.
As noted earlier, we have multiple automotive design wins going into production later this year, including an emergency power supply for a Tier 1 automotive supplier. We have additional designs scheduled for production in 2023 and 2024, and a strong pipeline of design activity involving seven of the world's top 11 automakers. While revenues will ramp gradually given the length of automotive design cycles, we are excited about our progress, and we are investing in products, people, and facilities to make automotive a significant part of our business in the coming years. Another new revenue stream for 2022 is motor drives.
Our BridgeSwitch products drive brushless DC motors, which are being adopted by appliance makers to keep pace with the efficiency requirements such as China's n