In this circuit, driver transistor Q2's PWM duty cycle varies from 100% at actuation to a power saving 50% sustain. It can accommodate load currents up to half an amp. R5 protects current limiter Q3's base-emitter junction from destruction by over-current
| Authors | Stephen Woodward |
| Main Document | Article «8 to 48 volt PWM relay/solenoid driver finds fault, pinches power» |
| Description | Figure 1 |
| File Format / Size | PDF / 15 Kb |
| Document Language | English |
Other Materials from the Main Document
- Article «8 to 48 volt PWM relay/solenoid driver finds fault, pinches power»
- Figure 1. In this circuit, driver transistor Q2's PWM duty cycle varies from 100% at actuation to a power saving 50% sustain. It can accommodate load currents up to half an amp. R5 protects current limiter Q3's base-emitter junction from destruction by over-current
- Figure 2. In this timing diagram, T1 = timeout to first fault check = L1/R timeconstant = ~500 µs. T2 = ~100% PWM duty cycle to power initial actuation = ~10 ms. T3 = ~50% sustain duty cycle for as long as application requires. And T4 = PWM sustain cycle = ~1