Power Management

Flyback Controller – Getting started

A flyback controller is a dedicated IC that’s designed to regulate a flyback converter. Click the different boxes in the diagram below to read more about each feature.

feedback-configuration-circuit

Feedback Configuration

Secondary Side Regulation (SSR)

  • Output is regulated directly from the output. An optocopuler is recommended to maintain isolation.

Primary Side Regulation (PSR)

  • Output is regulated from the auxiliary winding. This simplifies the design by eliminating the optocopuler based feedback network.
operating-mode

Operating Mode

Discontinuous Conduction Mode (DCM)

  • Typical for lower power levels, current fully discharges from transformer every switching cycle.

Quasi-Resonant/Transition Mode(QR/TM)

  • Typical for higher power levels, special DCM case where switch turns on at first valley to reduce switching losses.

Continuous Conduction Mode (CCM)

  • Typical for some operating points in higher power levels, current always conducts through the transformer.

Active Clamp Flyback (ACF)

  • Dissipative clamp replaced with lossless active clamp, which is used to achieve zero voltage switching and drastically improve efficiency
switch

Switch

Metal Oxide Semiconductor Field Effect Transistor (MOSFET )

  • Electrical switch that’s turned on and off by an external voltage.

Bipolar Junction Transistor (BJT)

  • Electrical switch that is turned on and off by an injected current.
integrated

Integrated High Voltage (HV) Startup

Yes

  • Integrated high voltage startup switch reduces standby power consumption.

No

  • External resistors required for startup.

External

  • Optional interface to easily implement a low standby power depletion mode FET startup circuit.
cable-compensation

Cable Compensation (CBC)

Fixed

  • Output voltage increases at predetermined amounts as output current increases to compensate for resistive losses on long cables, enabling tight regulation at true output at end of cable.

User Adjustable

  • Output voltage increases at user programmable amounts as output current increases to compensate for resistive losses on long cables, enabling tight regulation at true output at end of cable.

No

  • Output voltage fixed, regardless of output current magnitude.
constant-voltage-control

Constant Voltage (CV)/Constant Current (CC) Control

Yes

  • When output reaches max current the output turns into a constant current source, preventing current from exceeding max current threshold.

No

  • When output reaches max current the output turns into a constant power source, with the output voltage decreasing with increasing output current.
ntc-interface

Negative Temperature Coefficient (NTC) Resistor Interface

Yes

  • Direct connection with a negative temperature coefficient interface resistor, enabling external over temperature shutdown protection in addition to internal protection limit.

No

  • No direct connection with a negative temperature coefficient. Over temperature protection is dependent on internal limit of device.