Abstract: Improving start-up time of a light emitting diode (led) driver at lower input voltage is accomplished with a quick start circuit comprising a constant current source that replaces the traditional trickle charge start-up path for charging of a Vcc capacitor supplying operating voltage to an SMPS controller. Also the constant current source will only be operational during SMPS start-up, then will turn off after the SMPS is capable of producing its own regulated power supply to the Vcc terminal of the SMPS controller, thereby minimizing E2/R power losses in the SMPS.

Abstract: Total harmonic distortion (THD) at the AC line input of a power factor corrected (PFC) flyback switch mode power supply (SMPS) is reduced by adding additional current injection to the current programming signal of a PFC controller during the period of the line cycle where the AC input current wave shape is most flattened, i.e., around the peak portion of the AC line voltage. The input current drawn by the PFC flyback SMPS will then more closely resemble a desired sinusoidal waveform. A voltage dependent non-linear resistance is coupled in parallel with the normal current injection resistor that supplies current to the PFC flyback controller multiplier input to inject appropriate values of additional current into the PFC flyback controller based upon the AC input voltage value(s) so as to better shape the AC input current to the desired sinusoidal waveform.

Abstract: A circuit for dimming a lamp is provided. The circuit includes a triac dimmer that adjusts the voltage level of an input AC waveform based on the setting of a dimmer switch. The output of the dimmer is provided to a power supply circuit that drives the lamp based on the voltage level at the dimmer output. The power supply circuit includes a compensation circuit that compensates for loss of dimmer output signal caused by the triac when the dimmer switch is adjusted for full output. The compensation circuit is configured to engage at dimmer output voltage levels between full power supply voltage and a voltage threshold. The voltage threshold may be based on the dimmer output voltage level when the dimmer switch is set for full output. The compensation circuit essentially disengages to allow the lamp to dim when the dimmer output voltage level falls below the threshold.

Abstract: A battery charger for a lead acid battery having a power supply with an input connected to an AC signal and an output connected to the battery. The power supply provides a charge current to the battery. A clock connected to the AC signal provides clock pulses having transitions synchronized with zero crossings of the AC signal. A voltage monitor connected to the battery detects a battery voltage substantially simultaneously with a zero value of the charge current. A charge mode control is connected to the clock and the voltage monitor for commanding different battery charge currents. The voltage monitor includes a temperature compensation circuit. The battery charger includes a display module that can be placed at a location remote from the battery charger and convenient to the user.

Abstract: A power supply circuit detects ground fault paths, and miswiring of the load, using a test mode in which electrical power is applied to only one power output terminal of the power supply relative to the ground terminal, while substantially no electrical power is applied to the second power output terminal relative to the ground terminal. If application of power during the test mode causes substantial current flow through ground, then there is a ground fault path, or an incorrect connection between the midpoint of the load and ground. The power supply further includes unique features for signaling the presence and kind of fault it has detected; the power supply is capable of distinguishing between ground faults in at least two different locations, and when a fault is detected, the power supply signals the presence of the fault and its location, e.g., by timed blinking of the connected discharge light. These features are enhanced by a diagnostic analyzer for connection to the power supply.

Abstract: A power supply circuit detects ground fault paths, and miswiring of the load, using a test mode in which electrical power is applied to only one power output terminal of the power supply relative to the ground terminal, while substantially no electrical power is applied to the second power output terminal relative to the ground terminal. If application of power during the test mode causes substantial current flow through ground, then there is a ground fault path, or an incorrect connection between the midpoint of the load and ground. The power supply further includes unique features for signaling the presence and kind of fault it has detected; the power supply is capable of distinguishing between ground faults in at least two different locations, and when a fault is detected, the power supply signals the presence of the fault and its location, e.g., by timed blinking of the connected discharge light. These features are enhanced by a diagnostic analyzer for connection to the power supply.

Abstract: A power supply power supply circuit of the kind which includes a transformer having primary and secondary windings and an oscillator for driving the primary winding in a bi-directional fashion, suitable for driving gas discharge lighting such as neon signs, which prevents dangerous overvoltage output conditions and detects relatively low level ground fault currents. The transformer includes a clamp winding which is in proximity to and capacitively coupled to the secondary winding. The terminals of the clamp winding are connected to a current imbalance detection circuit for detecting imbalance between the current flowing into one clamp winding terminal and the current out of the other clamp winding terminal. In a ground fault condition, ground fault current flows in an unbalanced fashion into the clamp winding terminal(s), and through the capacitive coupling to the secondary winding.

Abstract: A transformer control circuit which includes a ground fault detection circuit that detects ground fault currents in the transformer secondary and delivers a ground fault detection signal to the primary circuit. This circuit derives power from the secondary winding and transmits the ground fault detection signal through an optical isolation barrier, thus avoiding the use of an auxiliary transformer. The ground fault detection circuit further includes safety features for detecting whether AC power is being supplied without earth ground being connected, and/or whether there is an undesired electrical connection between a transformer output connection and earth ground, which would defeat the ground fault detection circuit.