OnSemi’s NCP4354A is a secondary-side switching power supply controller designed to achieve extremely low power loss applications at no load. The controller has no-load detection capability and makes the controller enter a shutdown mode with low power loss. During the shutdown mode, the primary side controller is turned off, and the output is provided by the output capacitor to maintain a regulated output, thereby eliminating power consumption. During the shutdown period, the output voltage is in a released state, and the output voltage is allowed to decrease within an adjustable range. Once more energy is required, the NCP4354A primary side control will automatically start to provide the required power. This article first introduces the introduction, basic features, internal block diagram and application areas of NCP4354A, and gives the design schematic diagram, component list and PCB component layout diagram of the corresponding design scheme.
The NCP4353/4 is a secondary side SMPS controller designed for use in applications which require extremely low no load power consumption. The device is capable of detecting “no load” conditions and entering the power supply into a low consumption OFF mode. During OFF mode , the primary side controller is turned off and energy is provided by the output capacitors thus eliminating the power consumption required to maintain regulation. During OFF mode, the output voltage relaxes and is allowed to decrease to an adjustable level. Once more energy is required, the NCP4353/4 automatically restarts the primary side controller.The NCP4353/4 controls the primary side controller with an “Active OFF” signal, meaning that it drives optocoupler current during OFF mode to pull−down the FB pin of the primary controller.
During normal power supply operation, the NCP4353/4 provides integrated voltage feedback regulation, replacing the need for a shunt regulator. The A versions include a current regulation loop in addition to voltage regulation. Feedback control as well as ON/OFF signal can be provided with only one optocoupler. The NCP4354 includes a LED driver pin implemented with an open drain MOSFET driven by a 1 kHz square wave with a 12.5% duty cycle when primary side is in regulation for indication purpose.
The NCP4353 is available in TSOP−6 package while the NCP4354 is available in SOIC−8 package.
Main features of NCP4354A:
• Operating Input Voltage Range: 2.5 V to 36.0 V
• Supply Current <100 _a
• ±0.5% Reference Voltage Accuracy (TJ = 25°C)
• Constant Voltage and Constant Current (A versions) Control Loop
• Indication LED PWM Modulated Driver (NCP4354x)
• Designed for use with NCP1246 Fixed Frequency PWM Controller
• This is a Pb−Free and Halide−Free Device
• Offline Adapters for Notebooks, Game Stations and Printers
• High Power AC−DC Converters for TVs, Set−Top Boxes, Monitors, etc.·POS System
Figure 1. Internal block diagram of NCP4354A
NCP4354A program introduction:
When designing an offline Ac-Dc power adapter, one key consideration is the power consumption in standby mode. Standby power consumption, also sometimes referred to as vampire power or phantom load, is the power consumed by Electronic devices when they are switched off, but still plugged into the wall. It is estimated that standby power accounts for nearly 10% of the energy usage in the average American home. One common contributor to vampire power in the home is notebook adapters. These adapters spend a lot of time left underneath desks with the notebook computer disconnected or powered off. The following design note features the latest techniques for minimizing the standby power consumption of a 65 W notebook adapter.
NCP4354A program main parameter table
Schematic diagram of NCP4354A scheme:
Figure 2. Schematic diagram of NCP4354A solution
NCP4354A program material list:
PCB component layout diagram: