Switching controller having frequency hopping for power supplies and method therefor
View Patent ↗A switching controller having frequency hopping is used for reducing the EMI of a power supply. A pattern generator generates a digital pattern code in response to a clock signal. An oscillator generates an oscillation signal for determining a switching frequency of a switching signal. A programmable capacitor coupled to the oscillator modulates the switching frequency in response to the variation of the digital pattern code. An attenuator connected to a voltage feedback loop attenuates a feedback signal. The feedback signal controls the pulse width of the switching signal. A programmable resistor coupled to the attenuator determines an attenuation rate of the attenuator in response to the digital pattern code. The attenuation rate is increased as the switching frequency increases. The pulse width of the switching signal is thus reduced, which compensates the decrease of the switching period and keeps the output power and the output voltage constant.
1. A switching controller having frequency hopping, comprising:
a pattern generator, receiving a clock signal and generating a digital pattern code in response to said clock signal;
an oscillator, for determining a switching frequency of a switching signal, wherein said switching signal is utilized to regulate an output of a power supply, and wherein said switching signal is synchronized with said clock signal; and
a programmable capacitor, coupled to said oscillator for modulating said switching frequency in response to said digital pattern code.
2. The switching controller having frequency hopping of claim 1 , wherein said programmable capacitor comprises:
switching-capacitor sets, connected to each other in parallel, wherein said switching-capacitor sets are formed by couples of switches and capacitors connected in series respectively, wherein said switches are turned on/off by said digital pattern code.
3. The switching controller having frequency hopping of claim 1 , wherein said oscillator comprises:
a charge-current source, for producing a charge current;
a discharge-current source, for producing a discharge current;
an osc capacitor, connected in parallel with said programmable capacitor;
an osc-charge switch, connected between said charge-current source and said osc capacitor;
an osc-discharge switch, connected between said discharge-current source and said osc capacitor;
a first comparator, wherein a positive input of said first comparator is supplied with an first osc-threshold voltage, a negative input of said first comparator is connected to said osc capacitor;
a second comparator, wherein a negative input of said second comparator is supplied with a second osc-threshold voltage, a positive input of said second comparator is connected to said osc capacitor, and wherein said first osc-threshold voltage is higher than said second osc-threshold voltage;
a first NAND gate, for producing an oscillation signal for determining said switching frequency, wherein a first input of said first NAND gate is driven by an output of said first comparator, and wherein an output of said first NAND gate turns on/off said osc-discharge switch; and
a second NAND gate, wherein two inputs of said second NAND gate are respectively connected to said output of said first NAND gate and an output of said second comparator, wherein an output of said second NAND gate is connected to a second input of said first NAND gate, and wherein said output of said second NAND gate turns on/off said osc-charge switch.
4. The switching controller having frequency hopping of claim 1 , further comprising:
an attenuator, coupled to a voltage feedback loop for attenuating a feedback signal, wherein said feedback signal is utilized to control the pulse width of said switching signal.
5. The switching controller having frequency hopping of claim 4 , wherein the switching controller further comprises:
a programmable resistor, connected to said attenuator for programming an attenuation rate of said attenuator in response to said digital pattern code.
6. A method for generating a hopping frequency through a switching controller, comprising:
generating a clock signal;
generating a digital pattern code in response to said clock signal through a pattern generator;
determining a switching frequency of a switching signal through an oscillator, wherein said switching signal is utilized to regulate an output of a power supply, and wherein said switching signal is synchronized with said clock signal; and
modulating said switching frequency in response to said digital pattern code through a programmable capacitor coupled to said oscillator.
7. The method of claim 6 , wherein said programmable capacitor comprises:
switching-capacitor sets, connected to each other in parallel, wherein said switching-capacitor sets are formed by couples of switches and capacitors connected in series respectively, wherein said switches are turned on/off by said digital pattern code.
8. The method of claim 6 , wherein said oscillator comprises:
a charge-current source, for producing a charge current;
a discharge-current source, for producing a discharge current;
an osc capacitor, connected in parallel with said programmable capacitor;
an osc-charge switch, connected between said charge-current source and said osc capacitor;
an osc-discharge switch, connected between said discharge-current source and said osc capacitor;
a first comparator, wherein a positive input of said first comparator is supplied with an first osc-threshold voltage, a negative input of said first comparator is connected to said osc capacitor;
a second comparator, wherein a negative input of said second comparator is supplied with a second osc-threshold voltage, a positive input of said second comparator is connected to said osc capacitor, and wherein said first osc-threshold voltage is higher than said second osc-threshold voltage;
a first NAND gate, for producing an oscillation signal for determining said switching frequency, wherein a first input of said first NAND gate is driven by an output of said first comparator, and wherein an output of said first NAND gate turns on/off said osc-discharge switch; and
a second NAND gate, wherein two inputs of said second NAND gate are respectively connected to said output of said first NAND gate and an output of said second comparator, wherein an output of said second NAND gate is connected to a second input of said first NAND gate, and wherein said output of said second NAND gate turns on/off said osc-charge switch.
9. A switching controller having frequency hopping, comprising:
a pattern generator, receiving a clock signal and generating a digital pattern code in response to said clock signal;
an oscillator, for determining a switching frequency of a switching signal, wherein said switching signal is utilized to regulate an output of a power supply; and
a frequency modulating circuit, coupled to said oscillator for modulating said switching frequency in response to said digital pattern code.
10. The switching controller having frequency hopping of claim 9 , wherein said switching signal is substantially synchronized with said clock signal.
11. The switching controller having frequency hopping of claim 9 , wherein the frequency modulating circuit is a programmable capacitor.
12. The switching controller having frequency hopping of claim 11 , wherein said programmable capacitor comprises:
switching-capacitor sets, connected to each other in parallel, wherein said switching-capacitor sets are formed by couples of switches and capacitors connected in series respectively, wherein said switches are turned on/off by said digital pattern code.
13. The switching controller having frequency hopping of claim 9 , further comprising:
an attenuator, coupled to a voltage feedback loop for attenuating a feedback signal, wherein said feedback signal is utilized to control the pulse width of said switching signal.
14. The switching controller having frequency hopping of claim 13 , wherein the switching controller further comprises:
a programmable resistor, connected to said attenuator for programming an attenuation rate of said attenuator in response to said digital pattern code.