This paper mainly introduces the 75 W scheme of ONSEMI’s DC-DC Step-Down Controller Based on ncl35076 continuous conduction mode (CCM) and the 100 W and 240 w schemes based on ncl30076 quasi resonant (QR) step-down controller. The typical applications of the two schemes are led lighting system and analog / PWM dimmable LED driver. The analog dimming range is wide, from 1% to 100%.

Ansenmey’s proprietary LED current calculation technology and zero input voltage offset of internal detection and feedback amplifier can accurately stabilize the current within the whole analog dimming range. The current stabilization accuracy is ± 2% at full load and ± 20% at 1% load. Excellent dimming characteristics can be adjusted in CCM (ncl35076) or QR (ncl30076) and discontinuous conduction mode (DCM) according to load conditions Switching between, so as to ensure low LED current ripple to provide higher energy efficiency, such as working in CCM (ncl35076) or QR (ncl30076) under heavy load and DCM under light load. Standby power consumption is low in standby mode. PWM dimming is also provided to maintain constant LED color temperature. Ncl3x076 soft start function realizes steady-state start without overshoot. VDD overvoltage protection (OVP) and led short circuit protection (SLP) , overcurrent protection, thermal shutdown protection (TSD) and other protection features ensure high system reliability. Among them, ncl35076 CCM 75 W scheme has the advantage of small shape. While ncl30076 QR 100 W scheme has high energy efficiency under high voltage input.

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Figure 1: typical application circuit diagram of ncl35076 CCM 75 W scheme

The ncl30076 QR 240 w scheme shown in Figure 2 adopts ansenmey’s ncl2801cda PFC driver, ncl30076 step-down driver, ncp10671 switch driver and a dimming signal controller. Ncl2801cda is a current mode CRM boost PFC controller that uses ansenmey’s total harmonic distortion (THD) enhancement technology to provide best in class thd performance over a wider operating range. Valley count frequency reversal (vcff) method optimizes energy efficiency and standby power consumption. Ncp10671 integrates fixed frequency current mode controller and 700 V MOSFET, with high integration, including soft start, frequency jitter, short-circuit protection, jump cycle, slope compensation and dynamic self power supply (excluding auxiliary winding). During nominal load operation, ncp10671 switches at one of the available frequencies (60 or 100 kHz). When the output power demand decreases, the IC will automatically enter the skip cycle mode to reduce the standby power consumption. The protection function includes a timer for detecting overload or short circuit events and overvoltage protection with automatic recovery function. Ncp10671 has optimized standby performance, connects auxiliary windings or supplies power to IC from output, stops DSS operation, and helps reduce input power consumption under high voltage to less than 15 MW.

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Figure 2: typical application block diagram of ncl2801 + ncl30076 QR 240 w scheme

Accurate current stabilization and wide analog dimming

In addition, the test conditions and results of current stabilizing accuracy and simulated dimming range of ncl35076 CCM 75 W evaluation board and ncl30076 QR 100 W evaluation board are as follows:

Ncl35076 CCM 75 W evaluation board:

Vout (50 / 30 / 10 V), inductance value is typical value ± 20%, temperature (- 10 / 25 / 90 º C), 27 dimming curves are tested, the current stabilizing accuracy is ± 1.5% at full load and ± 10% at 1% load, and the simulated dimming range is 1%.

Ncl30076 QR 100 W evaluation board:

Vout (300 / 200 / 100 V), inductance value is typical value ± 15%, temperature (- 10 / 25 / 90 º C), 27 dimming curves are tested, the current stabilizing accuracy is ± 2% at full load and ± 14% at 1% load, and the simulated dimming range is 1%.

Energy efficiency test

The test conditions and energy efficiency curve of the evaluation board are as follows. The energy efficiency of ncl35076 CCM 75 W evaluation board at 10 V, 30 V and 50 V can be as high as 92%, 96% and more than 98%, and the energy efficiency of ncl30076 QR 100 W evaluation board at 100 V, 200 V and 300 V can be more than 96%, 97% and nearly 98% respectively.

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Figure 3: energy efficiency test curve of evaluation board

Thermal performance test

We tested the input voltage Vin 60 V, Vout 50 V, IOUT 1.5 A, ncl35076 CCM 75 W. the evaluation board has good thermal performance when it works for 30 minutes. The input voltage Vin 400 V, Vout 300 V, IOUT 0333 a, ncl30076 QR 100 W evaluation board also shows good thermal performance when working for 30 minutes.

summary

Ansenmey’s dimmable LED lighting step-down scheme based on ncl35076 or ncl30076 has the advantages of high energy efficiency, high precision and high reliability. The analog dimming range is as low as 1%. The proprietary LED current calculation technology and the zero input voltage offset of the internal detection and feedback amplifier make the current stabilization accuracy of ± 2% at full load and 1% at load ± 20%, PWM dimming is also provided to maintain constant LED color temperature. Rich protection features ensure high system reliability. High energy-efficient and intelligent LED lighting is an integral part of ansenmey’s intelligent power supply, which will help to achieve sustainable development.

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