Power converter controller IC having input voltage pin with multiple functions
View Patent ↗A controller integrated circuit (IC) for controlling a power converter uses its input voltage pin with a plurality of functions, including receiving an input voltage to the power converter, charging an external startup capacitor through charging circuitry coupled internally to the input voltage pin, and also receiving a test signal for programming a programmable resistance in an input voltage scale down circuitry coupled to the input voltage pin. Use of the input voltage pin with a plurality of functions reduces the number of pins required in the controller IC, thereby reducing the cost of manufacturing the controller IC.
1. A controller integrated circuit (IC) for controlling a power converter, the controller IC comprising:
an input voltage pin for receiving an input voltage to the power converter;
charging circuitry internal to the controller IC for charging a capacitor coupled externally to a supply voltage pin of the controller IC; and
scale down circuitry for scaling down the input voltage received at the input voltage pin, the scale down circuitry comprising a first transistor coupled to receive the input voltage, a second transistor connected in series to the first transistor, and a programmable resistor connected in series to the second transistor, the input voltage scaled down by the programmable resistor when both the first and second transistors are turned on.
2. The controller IC of claim 1 , wherein the charging circuitry comprises a switch that is turned on and off in response to a power-on-reset (POR) signal, the POR signal being in a first state to turn on the switch when the input voltage to the power converter is below a first threshold voltage and in a second state to turn off the switch when the input voltage to the power converter rises above the first threshold voltage but does not fall below a second threshold voltage.
3. The controller IC of claim 2 , wherein the capacitor is charged while the switch is turned on.
4. The controller IC of claim 1 , wherein the capacitor provides supply voltage to the controller IC during a startup mode of the power converter.
5. The controller IC of claim 1 , wherein the second transistor is on, and the first transistor is turned on and off in response to a power-on-reset (POR) signal, the POR signal being in a first state to turn off the first transistor when the input voltage to the power converter is below a first threshold voltage and in a second state to turn on the first transistor when the input voltage to the power converter rises above the first threshold voltage but does not fall below a second threshold voltage.
6. The controller IC of claim 1 , wherein a voltage at a node between the second transistor and the programmable resistor is clamped to a predetermined voltage when the input voltage causes the second transistor to operate in saturation.
7. The controller IC of claim 1 , wherein the programmable resistor comprises a plurality of resistors connected in series and a plurality of switches each coupled to one of the resistors, said each of the switches configured to short said one of the resistors to which said each of the switches is coupled, when said each of the switches is closed.
8. The controller IC of claim 7 , wherein the programmable resistor is programmed by a count signal determining how many of the switches are closed and how many of the resistors of the programmable switches are shorted by said closed switches.
9. The controller IC of claim 1 , wherein a test signal is input to the input voltage pin, the test signal including a first pulse with a first polarity indicating a start of a test mode, a plurality of pulses with a second polarity following the first pulse with the first polarity, and a second pulse with the first polarity indicating an end of the test mode, and wherein a count of the number of the pulses with the second polarity is used to set the programmable resistor.
10. The controller IC of claim 9 , wherein the count of the number of the pulses with the second polarity in the test signal is inversely proportional to the set resistance of the programmable resistor.
11. The controller IC of claim 9 , further comprising a counter for counting the number of the pulses with the second polarity in the test signal.
12. The controller IC of claim 9 , further comprising a fuse for storing the count of the number of the pulse with the second polarity.
13. A controller integrated circuit (IC) for controlling a power converter, the controller IC comprising:
an input voltage pin for receiving an input voltage to the power converter; and
scale down circuitry for scaling down the input voltage received at the input voltage pin, the scale down circuitry including a first transistor coupled to receive the input voltage, a second transistor connected in series to the first transistor, and a programmable resistor connected in series to the second transistor, the input voltage scaled down by the programmable resistor when both the first and second transistors are turned on; and
wherein the second transistor is on, and the first transistor is turned on and off in response to a power-on-reset (POR) signal, the POR signal being in a first state to turn off the first transistor when the input voltage to the power converter is below a first threshold voltage and in a second state to turn on the first transistor when the input voltage to the power converter rises above the first threshold voltage but does not fall below a second threshold voltage.
14. The controller IC of claim 13 , wherein a voltage at a node between the second transistor and the programmable resistor is clamped to a predetermined voltage when the input voltage causes the second transistor to operate in saturation.
15. The controller IC of claim 13 , wherein the programmable resistor comprises a plurality of resistors connected in series and a plurality of switches each coupled to one of the resistors, said each of the switches configured to short said one of the resistors to which said each of the switches is coupled, when said each of the switches is closed.
16. The controller IC of claim 15 , wherein the programmable resistor is programmed by a count signal determining how many of the switches are closed and how many of the resistors of the programmable switches are shorted by said closed switches.
17. The controller IC of claim 13 , wherein a test signal is input to the input voltage pin, the test signal including a first pulse with a first polarity indicating a start of a test mode, a plurality of pulses with a second polarity following the first pulse with the first polarity, and a second pulse with the first polarity indicating an end of the test mode, and wherein a count of the number of the pulses with the second polarity is used to set the programmable resistor.
18. The controller IC of claim 17 , wherein the count of the number of the pulses with the second polarity in the test signal is inversely proportional to the set resistance of the programmable resistor.
19. The controller IC of claim 17 , further comprising a counter for counting the number of the pulses with the second polarity in the test signal.
20. The controller IC of claim 17 , further comprising a fuse for storing the count of the number of the pulses with the second polarity.
21. The controller IC of claim 13 , further comprising charging circuitry internal to the controller IC for charging a capacitor coupled externally to a supply voltage pin of the controller IC, the charging circuitry including a switch that is turned on and off in response to a power-on-reset (POR) signal, the POR signal being in a first state to turn on the switch when the input voltage to the power converter is below a first threshold voltage and in a second state to turn off the switch when the input voltage to the power converter rises above the first threshold voltage but does not fall below a second threshold voltage.
22. The controller IC of claim 21 , wherein the capacitor is charged while the switch is turned on.
23. The controller IC of claim 21 , wherein the capacitor provides supply voltage to the controller IC during a startup mode of the power converter.
24. In a controller integrated circuit (IC) for controlling a power converter, the controller IC comprising an input voltage pin for receiving an input voltage to the power converter, and scale down circuitry including a programmable resistor for scaling down the input voltage received at the input voltage pin, a method of setting a resistance of the programmable resistor, the method comprising:
providing a test signal to the input voltage pin, the test signal including a first pulse with a first polarity indicating a start of a test mode, a plurality of pulses with a second polarity following the first pulse with the first polarity, and a second pulse with the first polarity following the pulses with the second polarity and indicating an end of the test mode; and
setting the resistance of the programmable resistor based on a count of the number of pulses with the second polarity in the test signal.
25. The method of claim 24 , wherein the pulses with the second polarity are continued in the test signal until a desired output voltage level is achieved in the power converter in responsive to an input voltage level, the resistance of the programmable resistor being set based on the count of the pulses with the second polarity in the test signal when the desired output voltage level is achieved.
26. The method of claim 25 , wherein the count of the number of pulses with the second polarity in the test signal is inversely proportional to the set resistance of the programmable resistor.