Charge pump with reduced noise
A charge pump generates gate control voltage in a DC/DC converter. The input voltage to the charge pump may vary. To reduce noise at higher input voltages, a variable resistance is included in the charge pump and that resistance is controlled to vary with the input voltage.
1 . A charge pump circuit comprising:
charge pumping capacitance;
switches that vary voltage across the pumping capacitance to provide a pumped output voltage from an input voltage;
variable resistance; and
control that varies the variable resistance with varied operating point.
2 . A charge pump as claimed in claim 1 wherein the variable resistance is coupled in series with the pumping capacitance and input voltage.
3 . A charge pump as claimed in claim 1 wherein the variable resistance comprises a switch coupled in parallel with a resistor.
4 . A charge pump as claimed in claim 3 wherein the switch is a field effect transistor.
5 . A charge pump as claimed in claim 3 wherein the control comprises a comparator.
6 . A charge pump as claimed in claim 3 wherein the control comprises an amplifier.
7 . A charge pump as claimed in claim 3 wherein the control comprises a shunt reference device.
8 . A charge pump as claimed in claim 1 wherein the variable resistance comprises a field effect transistor.
9 . A charge pump as claimed in claim 1 wherein the control comprises a comparator.
10 . A charge pump as claimed in claim 1 wherein the control comprises an amplifier.
11 . A charge pump as claimed in claim 1 wherein the control comprises a shunt reference device.
12 . A controller comprising:
charge pumping capacitance;
switches that vary voltage across the pumping capacitance to provide a pumped output voltage from an input voltage;
variable resistance; and
control that varies the variable resistance with varied operating point.
13 . A controller as claimed in claim 12 comprising both a charge pump internal to a controller integrated circuit and an external charge pump.
14 . A controller as claimed in claim 12 wherein the variable resistance is coupled in series with the pumping capacitance and input voltage.
15 . A controller as claimed in claim 12 wherein the variable resistance comprises a switch coupled in parallel with a resistor.
16 . A controller as claimed in claim 15 wherein the switch is a field effect transistor.
17 . A controller as claimed in claim 15 wherein the control comprises a comparator.
18 . A controller as claimed in claim 15 wherein the control comprises an amplifier.
19 . A controller as claimed in claim 15 wherein the control comprises a shunt reference device.
20 . A controller as claimed in claim 12 wherein the variable resistance comprises a field effect transistor.
21 . A controller as claimed in claim 12 wherein the control comprises a comparator.
22 . A controller as claimed in claim 12 wherein the control comprises an amplifier.
23 . A controller as claimed in claim 12 wherein the control comprises a shunt reference device.
24 . A DC/DC converter comprising:
controlled switches; and
a controller that controls the controlled switches, the controller comprising:
charge pumping capacitance;
switches that vary voltage across the pumping capacitance to provide a pumped output voltage to the controller from an input voltage;
variable resistance; and
control that varies the variable resistance with varied operating point.
25 . A DC/DC converter as claimed in claim 24 comprising both a charge pump internal to a controller integrated circuit and an external charge pump.
26 . A DC/DC converter as claimed in claim 24 wherein the variable resistance is coupled in series with the pumping capacitance and input voltage.
27 . A DC/DC converter as claimed in claim 24 wherein the variable resistance comprises a switch coupled in parallel with a resistor.
28 . A DC/DC converter as claimed in claim 27 wherein the switch is a field effect transistor.
29 . A DC/DC converter as claimed in claim 27 wherein the control comprises a comparator.
30 . A DC/DC converter as claimed in claim 27 wherein the control comprises an amplifier.
31 . A DC/DC converter as claimed in claim 27 wherein the control comprises a shunt reference device.
32 . A DC/DC converter as claimed in claim 24 wherein the variable resistance comprises a field effect transistor.
33 . A DC/DC converter as claimed in claim 24 wherein the control comprises a comparator.
34 . A DC/DC converter as claimed in claim 24 wherein the control comprises an amplifier.
35 . A DC/DC converter as claimed in claim 24 wherein the control comprises an shunt reference device.
36 . A method of charge pumping comprising:
varying voltage across a pumping capacitor to provide a pumped output voltage from an input voltage; and
varying variable resistance in circuit with the pumping capacitance with varied operating point.
37 . A method as claimed in 36 wherein the variable resistance is coupled in series with the pumping capacitance and input voltage.
38 . A method as claimed in 36 wherein the variable resistance comprises a field effect transistor.
39 . A method as claimed in 36 wherein the variable resistance is varied in response to a comparator.
40 . A method as claimed in 36 wherein the variable resistance is varied in response to an amplifier.
41 . A method as claimed in 36 wherein the variable resistance is varied in response to a shunt reference device.
42 . A method of converting DC voltage to DC voltage comprising:
varying voltage across a pumping capacitor to provide a pumped output voltage from an input voltage;
varying variable resistance in circuit with the pumping capacitance with varied operating point;
applying the output voltage to a controller; and
controlling converter switches from the controller.
43 . A method as claimed in 42 wherein the variable resistance is coupled in series with the pumping capacitance and input voltage.
44 . A method as claimed in 42 wherein the variable resistance comprises a field effect transistor.
45 . A method as claimed in 42 wherein the variable resistance is varied in response to a comparator.
46 . A method as claimed in 42 wherein the variable resistance is varied in response to an amplifier.
47 . A method as claimed in 42 wherein the variable resistance is varied in response to a shunt reference device.
48 . A charge pump comprising:
means for varying voltage across a pumping capacitor to provide a pumped output voltage from an input voltage; and
means for varying variable resistance in circuit with the pumping capacitance with varied operating point.
49 . A controller comprising:
means for varying voltage across a pumping capacitor to provide a pumped output voltage from an input voltage; and
means for varying variable resistance in circuit with the pumping capacitance with varied operating point.
50 . A DC/DC converter comprising:
means for varying voltage across a pumping capacitor to provide a pumped output voltage from an input voltage;
means for varying variable resistance in circuit with the pumping capacitance with varied input voltage;
means for applying the output voltage to a controller; and
means for controlling converter switches from the control.