| 摘要 |
A controller providing protection function and frequency-reduction function for a power conversion application, including: a voltage sense pin; a current source; a switch having a first end coupled to the current source, a second end coupled to the voltage sense pin, and a control end coupled with a control signal; and a sampling unit having a first node coupled to the voltage sense pin, a second node for providing the control signal, a third node for receiving a PWM signal, a fourth node for providing a first sampled voltage for a protection function, and a fifth node for providing a second sampled voltage for a frequency-reduction function. |
| 主权项 |
1. A controller providing protection function and frequency-reduction function for a power conversion application, comprising:
a voltage sense pin; a current source; a switch having a first end coupled to said current source, a second end coupled to said voltage sense pin, and a control end coupled with a control signal; a sampling unit having a first node coupled to said voltage sense pin, a second node for providing said control signal, a third node for receiving a PWM signal, a fourth node for providing a first sampled voltage, and a fifth node for providing a second sampled voltage, wherein when said PWM signal is at a first level, said control signal will be inactive and said switch will be off, and said sampling unit will sample a voltage at said voltage sense pin to generate said first sampled voltage; when said PWM signal is at a second level, which is different from said first level, said control signal will be active to switch on said switch, and said sampling unit will sample a voltage at said voltage sense pin to generate said second sampled voltage; a comparator having a positive input end coupled with said first sampled voltage, a negative input end coupled with a reference voltage, and an output end for providing a protection signal; a threshold voltages generation unit having a sixth node for receiving said second sampled voltage, a seventh node for providing a first threshold voltage according to a first function of said second sampled voltage, an eighth node for providing a second threshold voltage according to a second function of said second sampled voltage, and a ninth node for providing a third threshold voltage according to a third function of said second sampled voltage, wherein said first threshold voltage is higher than said second threshold voltage and said second threshold voltage is higher than said third threshold voltage; and a PWM unit having a tenth node for receiving a feedback voltage from a load via a feedback circuit, and an eleventh node for providing said PWM signal of a switching frequency, wherein said PWM unit adjusts said switching frequency in response to said feedback voltage in a way that said switching frequency starts to decrease from a first frequency when said feedback voltage falls below said first threshold voltage, said switching frequency stops decreasing and then remains at a second frequency when said feedback voltage falls below said second threshold voltage, and said PWM signal enters a green mode when said feedback voltage falls below said third threshold voltage; and wherein said PWM unit will shut down said PWM signal when said protection signal is active. |
