LinkSwitch-4 is a family of CV/CC primary-side regulated (PSR) switcher ICs that use an adaptive base and emitter switched drive scheme for bipolar junction transistor switches (BJTs) that substantially improves power conversion efficiency and eliminates reliability concerns due to secondary breakdown. The devices target chargers and adapters required to meet stringent new efficiency rules from the US Department of Energy (DoE) and European Code of Conduct (CoC), both of which are scheduled to come into force in January 2016. The new DoE rules, known as DoE-6, require efficiency compliance measurements to be taken at the end of the charger USB cable; LinkSwitch-4 exceeds the requirements while using a low-complexity Schottky diode secondary, even for high-current 1.5A and 2A smartphone chargers.
The ICs incorporate a multimode PWM/PFM controller with a quasi-resonant switching strategy to maximise the efficiency, meet less-than-30 mW no-load limits and at the same time maintain fast transient response. An operating frequency of up to 65 kHz enables transformer size to be minimised, and the minimum peak current is fixed to improve transient load response. Devices compensate for a number of factors including: transformer inductance tolerances; input line voltage variations; cable voltage drop; and external component temperature variations. Accurate IC parameter tolerances are maintained using proprietary trimming technology.
Power Integrations adds, “The LinkSwitch-4 controller’s adaptive base and emitter switched drive scheme boosts switching performance and delivers higher efficiency than is possible using existing BJT or MOSFET switchers. The technique also eliminates secondary breakdown associated with BJTs and reduces sensitivity to variation in current gain, allowing use of very low cost BJTs. The adaptive base-emitter switched drive technology not only provides design and manufacturing flexibility in the choice of BJT transistors by dynamically optimising BJT switching characteristics but also dramatically improves the reliability of BJTs based solutions.”
LinkSwitch-4 ICs are available in SOT-23-6 and SO-8 packages, priced at $0.16 to $0.25 (10,000).
Power Integrations; http://ac-dc.power.com/products/linkswitch-family/linkswitch-4