| 摘要 |
A circuit and method for regulating the battery charge current with improved loop stability is achieved. Key element of this invention is a digital low pass filter within the feedback loop of the regulator, which is built by an up/down counter, a digital-to-analog-converter and a variable frequency oscillator. The disclosed invention employs a digital low pass filter arrangement. It achieves stability by being able to choose the low pass filter time constant longer than the supply-voltage-pulse-width with reduced circuit complexity and less electronic circuit resources. Futhermore, the timing characteristics can be varied during normal operation by modifying the oscillator frequency and by presetting the up/down counter to defined values. The circuit is capable of regulating a charge current from a pulsed power supply, such as a rectified sine wave power supply without capacitor and can provide a pulse-width-modulated charge current. The circuit makes sure that the maximum peak current of the battery is not exceeded by sampling only when there is sufficient supply voltage. <IMAGE> |
