Charge pump circuit with feedback control

• US 5,717,581 A
• Filed: 10/15/1996
• Issued: 02/10/1998
• Est. Priority Date: 06/30/1994
• Status: Expired due to Term

• Current Assignee: SGS-Thomson Microelectronics (STMicroelectronics NV)
• Original Assignee: SGS-Thomson Microelectronics (STMicroelectronics NV)
• Inventors: Canclini, Athos
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Riley, Shawn
• Application Number:
  US08/729,315
• Time in Patent Office: 483 Days
• Field of Search: 307/110, 363/61, 363/62, 363/60, 327/536
• US Class Current: 363/60
• CPC Class Codes: H02M 3/073 Charge pumps of the Schenkel-type

Abstract

A charge pump circuit with negative current feed back is disclosed. The charge pump circuit consists of charge pump stages, switch circuits in between the stages, and a feedback loop to control the conductivity of the switch circuit. The conductivity of the switch circuits is controlled by modulating the bias current of the switch circuit which modulates its conductivity. By using the feedback loop to control the conductivity, the output voltage of the charge pump circuit can be regulated.

Claims

1. A method of regulating the output voltage in a charge pump circuit comprising the steps of:

charging a first capacitor to a voltage;

periodically pumping said first capacitor to a higher voltage;

periodically conducting current through a first switch circuit from said first capacitor to a second capacitor which is operatively connected, through zero or more additional pumping stages which each comprise an additional switching circuit and an additional capacitor, to provide a pumped output voltage; and

modulating the on-state conductivity of said switch circuit responsive to said pumped output voltage.

2. The method of claim 1 wherein the step of modulating the conductivity further comprises the steps of feeding back the output voltage to a current bias circuit and modulating a bias voltage so that the on-state conductivity of said switch circuit is modulated responsive to the output voltage.

3. The method of claim 2 wherein the step of feeding back comprises negative feedback.

4. The method of claim 1 wherein the step of modulating the current further comprises the steps of:

sensing the output voltage of the charge pump circuit;

reducing the conductivity of the switch circuit as the output voltage rises above a desired voltage; and

increasing the conductivity of the switch circuit as the output voltage falls below a desired voltage.

5. The method of claim 3 wherein the step of reducing the conductivity of a switch circuit comprises reducing a bias current to the switch circuit.

6. A bias current circuit for modulating the conductivity of a switch circuit in a charge pump comprising:

an amplifier having an input for receiving a output voltage, and having an output;

a constant current source having an output connected to a switch circuit for providing a bias current to said switch circuit; and

a current source having a control element connected to the output of said amplifier and having a current draining element connected to the output of said constant current source for modulating the bias current of said switch circuit responsive to the output voltage;

wherein the amplifier comprises;

a zener diode having a cathode for receiving an output voltage and having an anode;

a npn bipolar transistor having a base connected to the anode of said zener diode, having a collector and an emitter;

a current source having a drain connected to the emitter of said npn bipolar transistor and having a source connected to a reference voltage; and

a first current mirror having a current path connected between the output voltage and the collector of said npn bipolar transistor and having an output so that the output current is proportional to the output voltage.

7. The circuit of claim 6 wherein the first current mirror further comprises:

a first pnp bipolar transistor having an emitter connected to the output voltage and having a gate and collector connected to said npn bipolar transistor; and

a second pnp bipolar transistor having an emitter connected to the output voltage, having a base connected to the base of said first pnp bipolar transistor and having a collector for outputting the current of the amplifier.

8. The circuit of claim 6 wherein said current source further comprises:

a n-channel transistor having a drain connected to the source of said constant current source, having a source connected to a voltage reference, and having a gate connected to the source of said constant current source; and

a second current mirror having a first current path connected between the output of said amplifier and a voltage reference, and having mirrored current path connected between the source of said constant current source and a reference voltage, for decreasing the bias current to the switching circuit responsive to the output of said amplifier.

9. The circuit of claim 8 wherein the second current mirror comprises:

a first npn bipolar transistor having a collector and a gate connected to the output of said amplifier and having an emitter connected to ground; and

a second npn bipolar transistor having an emitter connected to ground, having a gate connected to the gate of said first npn-bipolar transistor, and having a collector connected to the source constant current source.

10. A circuit for rectifying current in a charge pump comprising:

a switch circuit having a current path between a first charge pump stage and a second charge pump stage and having a current bias element for receiving a bias current; and

a bias circuit connected to the current bias element of said switch circuit for modulating the conductivity of said switch circuit, responsive to an output to said charge pump;

wherein the amplifier comprises;

a zener diode having a cathode for receiving a pumped voltage and having an anode;

a npn bipolar transistor having a base connected to the anode of said zener diode, having a collector and an emitter;

a current source having a drain connected to the emitter of said npn bipolar transistor and having a source connected to a reference voltage; and

a first current mirror having a current path connected between the output voltage and the collector of said npn bipolar transistor and having an output so that the current output is proportional to the output voltage;

wherein the first current mirror further comprises;

a first pnp bipolar transistor having an emitter connected to the output voltage and having a gate and collector connected to said npn bipolar transistor; and

a second pnp bipolar transistor having an emitter connected to the output voltage, having a base connected to the base of said first pnp bipolar transistor and having a collector for outputing the current of the amplifier.

11. A circuit for rectifying current in a charge pump comprising:

a switch circuit having a current path between a first charge pump stage and a second charge pump stage and having a current bias element for receiving a bias current; and

a bias circuit connected to the current bias element of said switch circuit for modulating the conductivity of said switch circuit, responsive to an output to said charge pump;

an amplifier having an input connected to the output voltage, and having an output;

a constant current source having an output connected to the current bias element of said switch circuit for providing a bias current to said switch circuit; and

a current source having a control element connected to the output of said amplifier and having a current draining element connected to the output of said constant current source for modulating the bias current of said switch circuit responsive to the output voltage;

wherein said current source further comprises;

a n-channel transistor having a drain connected to the source of said constant current source, having a source connected to a voltage reference, and having a gate connected to the source of said current source, and

a second current mirror having a first current path connected between the output of said amplifier and a voltage reference, and having mirrored current path connected between the source of said constant current source and a reference voltage, for decreasing the bias current to the switching circuit responsive to the output of said amplifier.

12. A charge pump circuit comprising:

a plurality of charge pump stages;

a plurality of switch circuits, each connected to provide a respective current path, between two of said charge pump stages, whose magnitude is determined by a bias current received at a bias current terminal; and

a plurality of bias circuits connected to the current bias elements of said switch circuit for modulating the on-state conductivity of said switch circuits, responsive to an output of said charge pump circuit, said bias circuits each comprising;

an amplifier having an input connected to the output voltage, and having an output;

a constant current source having an output connected to the current bias element of said switch circuit for providing a bias current to said switch circuit; and

a current source having a control element connected to the output of said amplifier and having a current draining element connected to the output of said constant current source for modulating the bias current of said switch circuit responsive to the output voltage.

13. A charge pump circuit comprising:

a plurality of charge pump stages;

a plurality of switch circuits having a current path between charge pump stages and having current bias elements for receiving a bias current; and

a plurality of bias circuits connected to the current bias elements of said switch circuit for modulating the conductivity of said switch circuits, responsive to an output of said charge pump circuit;

wherein the amplifier comprises;

a zener diode having a cathode for receiving a pumped voltage and having an anode;

a npn bipolar transistor having a base connected to the anode of said zener diode, having a collector and an emitter;

a current source having a drain connected to the emitter of said npn bipolar transistor and having a source connected to a reference voltage; and

a first current mirror having a current path connected between the output voltage and the collector of said npn bipolar transistor and having an output so that the current output is proportional to the output voltage.

14. The circuit of claim 13 wherein the first current mirror further comprises:

a first pnp bipolar transistor having an emitter connected to the output voltage and having a gate and collector connected to said npn bipolar transistor; and

a second pnp bipolar transistor having an emitter connected to the output voltage, having a base connected to the base of said first pnp bipolar transistor and having a collector for outputing the current of the amplifier.

15. A charge pump circuit comprising:

a plurality of charge pump stages;

a plurality of switch circuits having a current path between charge pump stages and having current bias elements for receiving a bias current; and

a plurality of bias circuits connected to the current bias elements of said switch circuit for modulating the conductivity of said switch circuits, responsive to an output of said charge pump circuit;

an amplifier having an input connected to the output voltage, and having an output;

a constant current source having an output connected to the current bias element of said switch circuit for providing a bias current to said switch circuit; and

a current source having a control element connected to the output of said amplifier and having a current draining element connected to the output of said constant current source for modulating the bias current of said switch circuit responsive to the output voltage;

wherein said current source further comprises;

a n-channel transistor having a drain connected to the source of said constant current source, having a source connected to a voltage reference, and having a gate connected to the source of said constant current source; and

a second current mirror having a first current path connected between the output of said amplifier and a voltage reference, and having mirrored current path connected between the source of said constant current source and a reference voltage, for decreasing the bias current to the switching circuit responsive to the output of said amplifier.

16. An integrated charge pump circuit, comprising:

a plurality of charge-pumping stages, each comprising an intermediate node, a clocked switching element connected to said intermediate node, a capacitor having a first terminal connected to said intermediate node and a second terminal connected to be driven by a respective clocked drive element; and

a bias circuit connected to monitor the voltage of an output connection, and to provide a corresponding bias signal to ones of said switching elements;

said ones of said switching elements modulating their on-state conductivity in dependence on said bias signal;

wherein said switching elements are connected in a series chain from an input connection to said output connection.

17. An integrated charge pump circuit, comprising:

a plurality of charge-pumping stages, each comprising an intermediate node, a clocked switching element connected to said intermediate node, a capacitor having a first terminal connected to said intermediate node and a second terminal connected to be driven by a respective clocked drive element; and

a bias circuit connected to monitor the voltage of an output connection, and to provide a corresponding bias signal to ones of said switching elements;

wherein said switching elements comprise a series transistor connected between two of said intermediate nodes, and also comprise a current mirror stage which modulates the current passed by said series transistor in the on-state, in dependence on said bias signal.