Hong Kong Applied Science and Technology Research Institute Company, Limited

High Tech Technology Limited

Chik Wai (David) Ng

Wai Kit (Victor) So

Kwok Kuen (David) Kwong

Hing Kit Kwan

Po Wah (Patrick) Chang

Tin Ho (Andy) Wu

Po Wah Chang

Ka Lok (Roy) Ng

Ki Hin (Gary) Choi

Yuanzhe Xu

Kwun Yuan (Godwin) Ho

Sheung Wai (Orange) Fung

Yuanzhe (Kevin) Xu

Wai Kei Or

Chi Chiu Tsang

Shaobin Wu

Kit Wing (Simon) Lee

Chi Tak (Gerry) Leung

Wing Cheong Mak

An Integrated Circuit (IC) package has a ferrite-dielectric shield between a planar inductor coil and a semiconductor chip. The shield blocks Electro-Magnetic Interference (EMI) generated by currents in the inductor coil from reaching the semiconductor chip. The shield has a ferrite layer surrounded by upper and lower dielectric laminate layers to prevent electrical shorts. The center end of the inductor coil connects to the semiconductor chip through a center post that fits through an opening in the shield that is over the air core center of the inductor coil. The center post can connect to a die attach pad that the semiconductor chip is mounted to. Bonding wires connect pads on the semiconductor chip to lead-frame pads on lead-frame risers that end at external package connectors. The outer end of the inductor coil connects to lead-frame outer risers also having external package connectors such as pins or bonding balls.

Ferrite electro-magnetic interference (EMI) shield between an integrated-circuit (IC) chip and an air-core inductor all inside a hybrid lead-frame package

A re-configurable bank of DC-DC converters has many channels, each with a DC-DC converter and a controller that senses the channel's output voltage and current to adjust a duty cycle of switch signals to the DC-DC converter. A serial bus connects to all controllers and writes digital voltage and current control targets into each controller. The controller has Digital-to-Analog Converters (DACs) that convert the targets to analog voltages that are compared to sensed output voltage and current. The comparison results are compared to a sawtooth wave to generate pulses of the switch signals that have a duty cycle adjusted for the target comparisons. In combined mode, a primary channel's controller generates switch signals for secondary channels having outputs shorted to the primary channel. Secondary channels have a mux to select switch signals from the primary controller during combined mode, and from the secondary controller during separated mode.

Flexible array of DC-DC converters reconfigurable using a shared serial bus

A modulator spreads the spectrum of a generated clock to reduce Electro-Magnetic Interference (EMI). A capacitor is charged by a variable current to generate a ramp voltage that is compared to a reference to end a clock cycle and discharge the capacitor. An up-down counter drives a Digital-to-Analog Converter (DAC) that controls the variable charging current to provide triangle modulation. A smaller offset current is added or subtracted for cubic modulation when the up-down counter reaches its minimum count. A frequency divider that clocks the up-down counter also clocks a Linear-Feedback Shift-Register (LFSR) to that controls pseudo-random current sources that further modulate variable current and frequency. The LFSR is clocked with the up-down counter to modulate each frequency step, or only at the minimum count to randomly modulate at the minimum frequency. Binary-weighted bits from the up-down counter to the DAC are swapped to modulate the frequency step size.

Digital frequency dithering for switched-mode power supplies (SMPS) using triangular, asymmetric cubic, or random cubic spread spectrum oscillators

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. Larger battery matrixes have row and column lines that are connected by connecting switches.

Serial multi-battery charger with independent simultaneous charge and discharge

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.

LED driver with small output ripple without requiring a high-voltage primary-side electrolytic capacitor

A fly-back power converter has a current-estimating control loop that senses the primary output current in a transformer to control the secondary output. A primary-side control circuit switches primary current through the transformer on and off. A discharge time when a secondary current through an auxiliary winding of the transformer is flowing is generated by sampling a voltage divider on an auxiliary loop for a knee-point. A normalized duty cycle is calculated by multiplying the discharge time by a current that is proportional to the switching frequency and comparing to a sawtooth signal having the switching frequency. The peak of a primary-side voltage is sensed from the primary current loop and converted to a current and multiplied by the normalized duty cycle to generate an estimated current. An error amp compares the estimated current to a reference to adjust the oscillator frequency and peak current to control primary switching.

Output current estimation for an isolated flyback converter with variable switching frequency control and duty cycle adjustment for both PWM and PFM modes

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.

Constant-current control module using inverter filter multiplier for off-line current-mode primary-side sense isolated flyback converter

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.

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Hong Kong, China

Chik Wai (David) Ng