Power Control Circuit Limits On Time To Prevent MOSFET Burnout

Feb. 12, 2009
Design Idea for a simple gated-osciallator circuit to limit MOSFET on-time using an An R-C time to limit On-time pulse period length and generates its own maximum permitted On/Off duty cycle.

A power control device that protects against MOSFET burnout was designed using a well-known gated-oscillator circuit. The circuit prevents excessive On time for the MOSFETs beyond a permitted limit. The R1-C1 time constant forms a timing circuit that limits the On-time pulse period and automatically generates its own maximum permitted On/Off duty cycle (Fig. 1). Without this timing circuit, if the input remained high for any reason it would then generate a continuous On condition for the powerdriver MOSFETs.

R1 is a variable resistor that sets the desired oscillator frequency by keeping the input always On or in one state. Once the limit frequency or On/Off period is set, the circuit is ready for operation with any input signal. A longer zero level (or Off) at the input keeps the zero level intact at the output. However, a longer one level (or On) is prevented automatically (Fig. 2). C1 can be from 100 pF to 10 F, and R1 can vary from 1 k to 1 M.

Sponsored Recommendations

Highly Integrated 20A Digital Power Module for High Current Applications

March 20, 2024
Renesas latest power module delivers the highest efficiency (up to 94% peak) and fast time-to-market solution in an extremely small footprint. The RRM12120 is ideal for space...

Empowering Innovation: Your Power Partner for Tomorrow's Challenges

March 20, 2024
Discover how innovation, quality, and reliability are embedded into every aspect of Renesas' power products.

Article: Meeting the challenges of power conversion in e-bikes

March 18, 2024
Managing electrical noise in a compact and lightweight vehicle is a perpetual obstacle

Power modules provide high-efficiency conversion between 400V and 800V systems for electric vehicles

March 18, 2024
Porsche, Hyundai and GMC all are converting 400 – 800V today in very different ways. Learn more about how power modules stack up to these discrete designs.

Comments

To join the conversation, and become an exclusive member of Electronic Design, create an account today!