LinkSwitch-4 uses technology acquired with PI’s purchase of Cambridge Semiconductor early in 2015. It now has a reference design for an energy meter PSU that boosts efficiency, and eliminates opto-couplers. The reference design (DER-479) demonstrates an industrial power supply using the LinkSwitch-4 family of CV/CC primary-side regulated (PSR) switcher ICs with a 1200V bipolar junction transistor (BJT). The design supports 440 VAC line inputs and features three outputs which combine to provide up to 11W of highly accurate constant-voltage DC power.
PI comments that Cambridge Semiconductor had developed expertise in driving bipolar junction transistors (BJTs) to maintain them in safe-operating-area conditions, and that experince is embodied in the reference design.
LinkSwitch-4 controllers feature an adaptive base and emitter switched drive scheme to boost switching performance and increase efficiency. The advanced switching technique is beneficial in high-voltage applications as it reduces slow turn-off switching losses and eliminates BJT failures due to secondary breakdown, improving the reverse-bias safe operating area (RBSOA) and system reliability. The LinkSwitch-4 controller’s primary-side regulated sensing methodology eliminates optocouplers, replacing them in the feedback loop with a simple transformer winding. The design uses just 50 mW under no-load conditions while maintaining a fast transient response. The 65 kHz operating frequency minimises transformer size, reducing system cost and PCB footprint.
LinkSwitch-4 devices also compensate for a number of factors including: transformer inductance tolerances; input line voltage variations; cable voltage drop; and external component temperature variations.
Power Integrations adds, “Power supplies for high-voltage systems such as three-phase meters and motor drives can be challenging to develop – efficiency, reliability and component count often suffer in such designs. By pairing the LinkSwitch-4 controller with a 1200 V BJT, the designs become very straightforward and extremely reliable.”
DER-479 is downloadable at www.power.com/der-479
Power Integrations; www.power.com