Current-driven PWM controller having a power saving means
US6768657B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 19, 2003 |
| Grant date | Jul 27, 2004 |
| Priority date | — |
| Expiry date | Mar 19, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02M3/33507
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Incorporating the PWM function with the power saving means develops the PWM controller in which the switching frequency is decreased in response to the decrease of the load. Further, the current-driven design minimizes the circuitry and reduces the cost of the PWM controller. Since most of the control signals are operated in current mode, the die size of integrated circuit of the PWM controller is greatly reduced. An off-time modulator is provided for power saving in which the discharge current of the oscillator is modulated. Keeping the maximum on-time of the PWM signal as a constant and increasing the off-time of the PWM signal extends the switching period in light load conditions. The off-time modulation is the function of a feedback current, which is derived from the feedback loop. An array of current operation is designed to generate the feedback voltage for the PWM control and meanwhile produces a modulated discharge current for power saving. A minimum discharge current is limited to prevent the switching frequency from flowing into the audio-band. Moreover, the minimum discharge current is switched on/off in response to the state of the supply voltage in which the minimum di…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.