Power Integrations, Inc.

A power converter controller with commands based on pulse pattern recognition is described. In one embodiment, a control system for a power converter includes a first switching circuit having a first controller, and a second switching circuit having a second controller. The second controller is configured to generate a pattern of pulses in a transmitted signal U TX . The pattern of pulses in the transmitted signal U TX corresponds to a predetermined command. The first controller is configured to receive a pattern of pulses in a received signal U RX . The first controller includes a pattern filter configured for: comparing the pattern of pulses in the received signal U RX with an expected pattern, and, when the pattern of pulses in the received signal U RX corresponds to the expected pattern, asserting the predetermined command.

The circuits and methods of the present disclosure control the active off-time (high side switch on-time) to ensure the magnetization energy release and resonant capacitor energy release in an asymmetrical half-bridge (AHB) converter finish at the same time and all the stored energy is delivered to the output in each switching cycle. Multiple, parallel, techniques to control the high side switch on-time are illustrated. One is to track the volt-seconds applied during the storage cycle and allow the active release off-time to be limited to the same volt-seconds. A second option is to provide a high side switch on-time that is proportional to the on-time of the low side switch in that switching cycle. A third option is to provide a maximum high side switch on-time that can be programmed to ensure the high side on-time is equal to or smaller than half of the resonant period.

A power converter having an integrated input bias self-supply function has an input switch, a controller, an output switch, and an output filter having an inductor. The controller includes control circuitry, a bias drive circuit, and a bias supply circuit. The bias supply circuit includes a bias transistor and a bias diode. The control circuitry and the bias drive circuit produce a bias drive signal indicative of the conductive states of the input and output switches. When the bias drive signal is asserted, the bias transistor is configured to be on and the bias diode is configured to be reverse biased and not conduct any forward current. When the bias drive signal is deasserted, the bias transistor is configured to be off.

A control system for a power converter having an energy transfer element, a power switch, and a synchronous rectifier (SR). The control system includes an SR control circuit and a cross conduction detector circuit. The detector circuit receives an SR signal indicating whether the synchronous rectifier has been turned on using a drive signal output by the SR control circuit. Based on the SR signal, the detector circuit determines whether the synchronous rectifier is conducting. The detector circuit also compares a voltage at a forward node of the energy transfer element to a threshold voltage to determine whether the power switch is conducting. The detection circuit disables the synchronous rectifier in response to detecting a cross conduction event, based on a determination that the synchronous rectifier and the power switch are both conducting during a time interval in which the synchronous rectifier is turned on.

A half-bridge circuit of a power converter includes a high-side device and a low-side device coupled together at a half-bridge node, which is in turn coupled to a network including an inductor and/or a capacitor. In some examples, the network is a resonant network. The half-bridge circuit further includes a first switch and a second switch. The first switch is coupled between the half-bridge node and a ground reference, in parallel with the low-side device. The second switch is coupled between an input node of the power converter and the half-bridge node, in series with a high-side capacitor that powers a driver of the high-side device. During power-up, the second switch turns on to provide a charging current to the high-side capacitor, while the first switch turns on to augment the charging current by pulling down a voltage at the half-bridge node, thereby diverting a shunt current away from the network.

A bridgeless power factor correction (PFC) circuit for reducing electromagnetic interference (EMI) is disclosed herein. A current source is placed in parallel with a switch of a low frequency leg. The current source may be turned on during zero crossings of the AC input voltage to limit current and reduce the rate of change in voltage. In turn, EMI may be advantageously reduced without the need for large passive filters or complicated circuitry.

Control of a resonant power converter using switch paths during power-up is described herein. During power-up, a first switch path sinks current away from a resonant capacitor while a second switch path sources current to a high-side capacitor. In this way the high-side capacitor may predictably charge to sufficient bootstrap voltage for steady state operation. Additionally, a third switch path may control current to a low-side capacitor.

A controller for a power converter includes a primary controller and a secondary controller. The primary controller is coupled to a primary winding of the energy transfer element and a primary switch of the power converter. The secondary controller is coupled to a secondary winding of the energy transfer element and a secondary switch, e.g., a synchronous rectifier, of the power converter. The secondary controller has a synchronous rectifier control/drive circuit, a control logic circuit, and a cross conduction detector circuit. Cross conduction is when the primary switch turns on when the secondary switch is active. The cross-conduction detector circuit produces a Disable SR signal when cross conduction event detected. The cross-conduction detector circuit detects zero voltage switching cross conduction event and a minimum conduction period cross conduction event. The SR drive circuit disables the synchronous rectifier in response to receiving the Disable SR signal.

A controller for a power converter comprising a drive circuit and an adaptive current limit generator. The drive circuit is coupled to receive a request signal representative of a power demand of an output of the power converter. The drive circuit is configured to generate a drive signal to control switching of a power switch in response to the request signal. The adaptive current limit generator configured to generate a current limit signal and the drive circuit is configured to turn off the power switch when a current sense signal reaches the current limit signal. The adaptive current limit generator is configured to vary an upper threshold of the current limit signal to a first value when a switching frequency is less than a frequency threshold and vary the upper threshold to a second value when the switching frequency is greater than the frequency threshold.

A method to charge a capacitance to provide operating power for a controller of a power converter. The method comprising controlling the turn ON and turn OFF of a power switch, wherein the power switch includes a first switch and a second switch, sensing a voltage across the capacitance, determining if the voltage falls below a reference, turning ON a branch switch in response to the voltage falling below the reference, wherein turning ON the branch switch redirects at least a portion of a drain current conducted by the first switch to the capacitance, sensing a branch current conducted by the branch switch, and regulating the branch current to not exceed a threshold by controlling a second switch current conducted by the second switch.