Abstract: A serial battery charger has a battery matrix with switches that are configured by a microcontroller that reads voltages between batteries to determine if each battery is fully-charged, charging, or absent. A switch configuration allows charging and discharging currents to flow simultaneously, and allows discharging current but blocks charging current from fully-charged batteries to prevent over-charging. The charging current flows through all charging batteries in series while the discharging current flows from all fully-charged and charging batteries in series. Blocking and bypass switches route the charging current to all charging batteries in series, but bypass all fully-charged and absent batteries. The blocking and bypass switches route the discharging current serially through all fully-charged and charging batteries in the battery matrix while avoiding absent batteries. The switches are controlled by the switch configuration from the microcontroller.

Abstract: A power converter reduces output ripple without using an electrolytic primary-side capacitor that can reduce product lifetime. Primary-Side Regulation (PSR) using an auxiliary winding provides a regulated secondary voltage with some low-frequency ripple on a secondary winding of a transformer. A smaller secondary capacitor that is not an electrolytic capacitor filters the output of the secondary side. A bang-bang controller controls the secondary side current to reduce current ripple despite voltage ripple. The bang-bang controller has a series resistor and inductor in series with a load such as an LED. A voltage drop across the series resistor increases when a switch turns on. This increasing voltage drop toggles the switch off once an upper limit voltage is reached. The voltage drop then decreases as inductor current is shunted by a diode, until the voltage drop reaches a lower limit voltage and the switch toggles on again.

Abstract: A power converter reduces output ripple without using an electrolytic primary-side capacitor that can reduce product lifetime. Primary-Side Regulation (PSR) using an auxiliary winding provides a regulated secondary voltage with some low-frequency ripple on a secondary winding of a transformer. A smaller secondary capacitor that is not an electrolytic capacitor filters the output of the secondary side. A bang-bang controller controls the secondary side current to reduce current ripple despite voltage ripple. The bang-bang controller has a series resistor and inductor in series with a load such as an LED. A voltage drop across the series resistor increases when a switch turns on. This increasing voltage drop toggles the switch off once an upper limit voltage is reached. The voltage drop then decreases as inductor current is shunted by a diode, until the voltage drop reaches a lower limit voltage and the switch toggles on again.

Abstract: A serial battery charger has a battery matrix with switches that are configured by a microcontroller that reads voltages between batteries to determine if each battery is fully-charged, charging, or absent. A switch configuration allows charging and discharging currents to flow simultaneously, and allows discharging current but blocks charging current from fully-charged batteries to prevent over-charging. The charging current flows through all charging batteries in series while the discharging current flows from all fully-charged and charging batteries in series. Blocking and bypass switches route the charging current to all charging batteries in series, but bypass all fully-charged and absent batteries. The blocking and bypass switches route the discharging current serially through all fully-charged and charging batteries in the battery matrix while avoiding absent batteries. The switches are controlled by the switch configuration from the microcontroller.

Abstract: A frequency dithering circuit reduces emissions that cause Electro-Magnetic Interference (EMI) by spreading the spectrum of a clock. The clock sequences a counter that drives a digital count value to a digital-to-analog converter (DAC). The DAC outputs a sawtooth wave with a wide voltage swing. A subtractor scales down the voltage swing to produce a reduced-swing sawtooth wave which is used as an upper limit voltage. Comparators trigger a set-reset latch to toggle the clock when current pumps charge and discharge a capacitor beyond voltage limits. Since the upper limit voltage is the reduced sawtooth wave from the subtractor, the amount of time to charge the capacitor varies, dithering the period of the clock. The degree of dithering can be adjusted by programming the feedback resistance in the subtractor. The subtractor reduces the sensitivity of dithering to errors in the DAC, allowing for an inexpensive, less precise DAC.

Abstract: A fly-back AC-DC power converter has a constant-current control loop that senses the primary output current in a transformer to control the secondary output without an expensive opto-isolator. A primary-side control circuit can use either a Quasi-Resonant (QR) or a Pulse-Width-Modulation (PWM) control loop to switch primary current through the transformer on and off. A feedback voltage is compared to a primary-side voltage sensed from the primary current loop to turn the switch on and off. A multiplier loop generates the feedback voltage using a multiplier. A level-shift inverter and a low-pass filter act as the multiplier by multiplying an off duty cycle of the switch by the feedback voltage to generate a filtered voltage. A high-gain error amp compares the filtered voltage to a reference voltage to generate the feedback voltage. The multiplier produces a simple relationship between the secondary current and the reference voltage, yielding simplified current control.