Low power charge pump regulating circuit

Details Low power charge pump regulating circuit Low power charge pump regulating circuit

2002-07-29

2003-05-20

Berhane, Adolf Daneke (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

C363S059000

Reexamination Certificate

active

06566847

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) FIELD OF THE INVENTION
This invention relates to a circuit for regulating the output voltage of a charge pump circuit and more particularly to using current feedback to provide analog control of the frequency of clock signals driving the charge pump circuit.
(2) Description of the Prior Art
Charge pump circuits are frequently used in EEPROM, Electronically Erasable and Programmable Read Only Memory, Circuits. These circuits supply the high voltages needed for erasing and reprogramming the Read Only Memories. These high voltages must be regulated in order to provide the proper voltages for the required application.
Many of the regulating methods used require a voltage reference and a voltage comparator which have the undesirable attribute of consuming extra power.
U.S. Pat. No. 5,553,030 to Tedrow et al. describes a charge pump circuit using comparator circuit comprising a differential amplifier circuit.
U.S. Pat. No. 5,812,017 to Golla et al. describes a charge pump voltage multiplier circuit using a voltage comparator.
U.S. Pat. No. 5,483,486 to Javanifard et al. describes a charge pump circuit using a voltage reference, a divider circuit, and a voltage controlled oscillator in regulating the output voltage.
U.S. Pat. No. 5,394,365 to Tsukikawa, U.S. Pat. No. 5,671,179 to Javanifard, and U.S. Pat. No. 5,781,473 to Javanifard et al. describe charge pump circuits.
U.S. Pat. No. 5,726,944 to Pelley et al. describe a charge pump circuit using a voltage regulation circuit comprising a band-gap voltage source.
U.S. Pat. No. 6,177,828 to Kang et al. describes a charge pump circuit wherein the voltage regulation is achieved by halting and restarting the charge pumping operation.
SUMMARY OF THE INVENTION
Charge pump circuits are frequently used to supply the higher voltages required for electronically erasing and writing EEPROM, Electronically Erasable Programmable Read Only Memory, circuits. The output voltage of the charge pump circuit must be regulated to maintain the proper voltage over the required range of operating load conditions. It is important to keep the power consumed by these voltage regulating circuits as low as possible.
FIG. 1
shows an example of a conventional means for providing voltage regulation for a charge pump circuit.
FIG. 1
shows a block diagram of a conventional voltage regulated charge pump circuit showing a current controlled oscillator
10
driven by a constant current generator
28
. The constant current generator
28
is connected to a primary voltage supply, V
DD
, and supplies a current to the input
26
of the current controlled oscillator
10
. The current controlled oscillator
10
produces clock signals, CK
IN
, at clock outputs
23
which are fed to the clock inputs
24
of the charge pump circuit
12
.
FIG. 1
shows two clock outputs and two clock inputs for two clock signals however the actual number of clock outputs, clock inputs, and clock signals may be more than two or less than two. The clock frequency of the clock signals CK
IN
determine the output voltage, V
HV
, appearing at the output
16
of the charge pump circuit
12
.
The output
16
of the charge pump circuit
12
is fed to the input
20
of a detecting circuit
14
which serves as a voltage divider producing a voltage proportional to voltage at the output
16
of the charge pump circuit
12
at the output
22
of the detecting circuit
14
. The output
22
of the detector circuit
14
is connected to the gate of an NMOS transistor
18
connected between the output
16
of the charge pump circuit
12
and ground potential. When the voltage at the output
16
of the charge pump circuit
12
becomes too high the voltage at the output
22
of the detecting circuit
14
turn on the NMOS transistor
18
and the current through the NMOS transistor
18
decreases the voltage at the output
16
of the charge pump circuit
12
until the voltage at the output
22
of the detecting circuit
14
drops and the current in the NMOS transistor
18
is reduced or turned off. This varying current in the NMOS transistor
18
provides voltage regulation for the charge pump circuit
12
but has the disadvantage of the power consumed by the NMOS transistor
18
.
FIG. 2
shows another example of a conventional means for providing voltage regulation for a charge pump circuit
12
.
FIG. 2
shows a block diagram of a conventional voltage regulated charge pump circuit showing an oscillator
11
controlled by a differential amplifier
34
. The oscillator
11
produces clock signals, CK
IN
, at the clock outputs
23
of the oscillator
11
which are fed to the clock inputs
24
of the charge pump circuit
12
.
FIG. 2
shows two clock outputs and two clock inputs for two clock signals, however the actual number of clock outputs, clock inputs, and clock signals may be more than two or less than two. The clock frequency of the clock signals CK
IN
determine the output voltage, V
HV
, appearing at the output
16
of the charge pump circuit
12
.
The output
16
of the charge pump circuit
12
is fed to the input
20
of a detecting circuit
14
which serves as a voltage divider producing a voltage proportional to voltage at the output
16
of the charge pump circuit
12
at the output
22
of the detecting circuit
14
. The output
21
of the detector circuit
14
is connected to a first input
22
of the differential amplifier
34
. The output
31
of a reference voltage source
30
is connected to a second input
32
of the differential amplifier
34
. The output
35
of the differential amplifier
34
is connected to the control input
36
of the oscillator
11
. When the voltage at the output
21
of the detecting circuit
14
, supplied to the first input
22
of the differential amplifier
34
, is less than the voltage supplied by the reference voltage source
30
to the second input
32
of the differential amplifier
34
, the signal at the output
35
of the differential amplifier
34
, fed to the control input
36
of the oscillator, turns the oscillator
11
on. When the oscillator
11
is on, the oscillator
11
supplies clock signals, CK
IN
, to the input
24
of the charge pump circuit
12
, and the voltage at the output
16
of the charge pump circuit
12
increases. When voltage at the output
21
of the detecting circuit
14
, supplied to the first input
22
of the differential amplifier
34
, is greater than the voltage supplied by the reference voltage source
30
to the second input
32
of the differential amplifier
34
, the signal at the output
35
of the differential amplifier
34
, fed to the control input
36
of the oscillator
11
, turns the oscillator
11
off. When the oscillator
11
is turned off clock signals, CK
IN
, are no longer supplied to the inputs
24
of the charge pump circuit
12
, and the voltage at the output
16
of the charge pump circuit
12
decreases. This turning the oscillator on and off provides voltage regulation for the charge pump circuit
12
but has the disadvantages of the need to supply a reference voltage source, the need for a differential amplifier, and of the fluctuation of the voltage at the output
16
of the charge pump circuit
12
caused by turning the oscillator on and off.
It is a primary objective of this invention to provide voltage regulation for a charge pump circuit using analog control of a current controlled oscillator without the need for a reference voltage supply.
It is another primary objective of this invention to provide voltage regulation for a charge pump circuit using analog control of a current controlled oscillator without the need for a reference voltage supply over the full range of the output voltage of the charge pump circuit.
It is another primary objective of this invention to provide voltage regulation for a charge pump circuit using analog control of a current controlled oscillator without the need for a reference voltage supply when the output voltage of the charge pump circuit exceeds a critical output voltage.
These objectives are achieved using a constant current generator a

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