3 An Led Lamp States That It Is 120v 6w 100ma The Led Lamp Circuit Is Shown In Figure 2 A The Smoothing Capacitor Is 1 (57.86 KiB) Viewed 62 times
3 An Led Lamp States That It Is 120v 6w 100ma The Led Lamp Circuit Is Shown In Figure 2 A The Smoothing Capacitor Is 2 (32.3 KiB) Viewed 62 times
3 An LED lamp states that it is 120V, 6W 100mA. The LED Lamp circuit is shown in Figure 2(a). The smoothing capacitor is 10 uF. (a) Give 2 reasons why this is a good circuit for such an application. (b) Discuss briefly why a simple calculation of input power does not give 6W. (c) Estimate the capacitor ripple voltage. (d) Find the estimated diode conduction angle and carefully sketch the AC line current. (e) The proposed design of the LED lamp circuit uses an ideal constant current source in series with the LEDs, Fig. 2(b), and the smoothing capacitor is removed. Sketch the AC line current and write down its Fourier series. (f) The practical circuit design is shown in Fig. 2(c), where the capacitors act in series when charging and in parallel when discharging, thereby allowing the 'current source' to work. By assuming the voltage on each capacitor remains at one half of the peak AC supply voltage, with only a small ripple, show that the third harmonic in the AC supply current is effectively removed. V1 60Hz, 120V D1 D4 D3 D2 Fig. 2 (a) C1 Т₁0μ R1 2.2K D5 Out of 4 22 4 4
60Hz, 120V 60Hz, 120V V1 D1 D4 D1 D4 Z A 5 D3 D2 * Fig. 2 (b) D3 D2 D7 Fig. 2 (c) C1 |10μ D8 D6 # * 40mA D5 $22 C2 10μ 40mA D5
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