For multi-output power supplies, an active shunt regulator and pre-load circuit may be used to prevent rising output voltages under unbalanced loading conditions.
Circuit Designs present tips and tricks for solving problems of interest to power supply designers. Here is where PI Applications Engineers turn their training and experience into practical circuit designs that can be employed to quickly and straightforwardly address problems of the sort that working designers often encounter.
Note: These ideas are presented for informational purposes only and Power Integrations makes no warranty herein expressed or implied.
A scaling buffer circuit for sensing a high DC input voltage is shown. The circuit can be used with a power converter controller.
Reduction of common-mode current in the input lines may be achieved by attaching copper foil between the core of the transformer and the switching node of a power switch. Further reduction can also be achieved by connecting a capacitor between an input-referenced bias winding and a copper foil attached to the core of the transformer.
A sensing circuit enables design of a forward converter using TOPSwitch-GX by ensuring that the transformer resets each cycle.
For a dual output flyback power supply, a ferrite magamp is used to regulate within tolerances levels when one output goes to no-load.
Externally fed current into the BYPASS (BP) pin from a floating constant current source enables start-up of the controller for a wide range of input voltages.
An alternative power factor correction (PFC) control technique is introduced to design high-bandwidth PFC controller for the off-line single-stage power converters. It may be used in commercial or consumer products including LED driver and appliances.
An improved feedback loop process is introduced for power factor correction (PFC) controllers in single-stage AC-DC power converters. It reduces external component count and simplifies end-user tuning for the external components of error compensation.
This circuit simplifies and reduces the cost of the electromagnetic interference (EMI) filter circuitry for AC-DC converters by using fast recovery diodes in the input bridge rectifier.
An efficient simple circuit with low component count may be added to the feedback circuitry of a high-side switching buck converter to dramatically improve the input line regulation.
The circuit provides overpower protection (OPP) or overcurrent protection (OCP) by using an active pre-load circuit to trigger an existing crowbar circuit used for overvoltage protection (OVP).
LED driver with a controlled active filter which is activated by a secondary-side phase detection circuit to enable the controlled active filter during low conduction angles of a dimmer circuit, such as a TRIAC dimmer. The controlled active filter can reduce shimmer and flicker of an LED load due to the asymmetry of TRIAC dimmers.
The controlled active filter can be used with single-staged LED drivers with power factor correction (PFC).
A power supply output disable circuit includes a series pass switch with additional capacitance to reduce turn-on current spikes of the series pass switch.
A primary-side controller for an isolated flyback power supply operating in continuous conduction mode (CCM) may use a primary-side winding to sense and to regulate the output voltage.
A primary-side controller for an isolated flyback power supply operating in discontinuous conduction mode (DCM) may use a primary-side winding to sense and to regulate the output voltage.
A controller may use an internal clamp circuit that conducts current from the V pin to prevent damage to the internal ESD (electrostatic discharge) protection structure.