CA1164941A - Active power supply ripple filter - Google Patents
Active power supply ripple filterInfo
- Publication number
- CA1164941A CA1164941A CA000380912A CA380912A CA1164941A CA 1164941 A CA1164941 A CA 1164941A CA 000380912 A CA000380912 A CA 000380912A CA 380912 A CA380912 A CA 380912A CA 1164941 A CA1164941 A CA 1164941A
- Authority
- CA
- Canada
- Prior art keywords
- power supply
- coupled
- voltage
- input
- terminal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/468—Regulating voltage or current wherein the variable actually regulated by the final control device is dc characterised by reference voltage circuitry, e.g. soft start, remote shutdown
Abstract
Abstract of the Disclosure An active power supply ripple filter with low noise and low power dissipation characteristics, which tracks the voltage of the power source with low voltage drop and high current capability. The circuit consists of a con-trol transistor connected between one terminal of a power source and one terminal of a load, a reference circuit which tracks the supply voltage, a low pass filter which filters the reference voltage and an amplifier for driv-ing the control transistor in response to the filtered reference voltage and a feedback voltage from the load.
The circuit minimizes the voltage drop across the control transistor as well as minimizing the capacitance values required for the filter capacitors.
The circuit minimizes the voltage drop across the control transistor as well as minimizing the capacitance values required for the filter capacitors.
Description
ACTIV~ POWER SUPPLY RIPPLE FILTER
Background of the Invention _ _ _ _ _ A. Field of the Invention The present invention relates to power supply circuitry and, in particular, to a low noise, low voltage drop, active power supply filter suitable for monolithic fabrication.
B. Description of the Prior Art In conventional communication circuitry it is often desirable to employ a power supply ripple filter which ~ will provide a well filtered, low noise supply voltaye ; capable of high output current and which drops as small a voltage as possible across the filter. Ripple filters I0 known in the prior art do not maintain a minimum voltage drop nor minimal noise leveLs. Further, prior art circuits require relatively large capacitance values to achieve a desired cut-off frequency and are not highly sultable for monolithic integration.
Accordingly, it is an object of the invention to provlde a low noise active power supply ripple filter capable of hiyh output currents while maintaining low voltage drop across the filter.
It is another object of the invention to provide a 20~ low~noise active power supply ripple fil~er which mini-mizes the capacitance values re~uired to achieve desired frequency rejecti~on characteristics.
It is yet another objec~t~of the invention to provide a low noise active power supply ripple filter which is ~ 25 particularly suitable Eor monolithic integration.
,~
: ' ' ' ' ' ' . ` . , , ~: , " , , , ` : " , : ~ : '' 1 ~ B ~
Briefly, in accordance with the invention a low noise active power supply filter capable of high output current is provided for elir~linating alternating current components from a direct current voltage, with a minimal input-output voltage drop. A control device such as a bipolar transistor is utilized with an input terminal coupled to the power supply and an output te~inal coupled to a load. rrhe control device controls and therefore to the power supply the current from the input terminal to the output terminal via a signal coupled to a control terrninal. A reference circuit coupled to the input terminal of -the control device provides a reference voltage which approximately tracks the power supply input voltage. An amplifier having its output coupled to the control terminal of the control device amplifies a signal applied across first and second input terminals. A fil-ter is coupled to the reference means to low pass filter the reference voltage and then couple the filtered refer-ence voltage to the first input of the amplifier means.
A feedback loop couples the control rneans output terminal to the second input of the amplifier means-The invention herein disclosed provides a low noiseactive power supply ripple filter capable of high output current which tracks the direct current supply voltage thereby maintaining a minimum voltage drop across the filter and low power dissipation. The filter also pro-vides some temperature compensation, permits the use of small vaIue filter capacitors and is particularly suit-able for monolitllic fabrication.
Brief ~escriptlon_of_the Drawings The features of the present invention which are believed to be novel are set forth wi-th particularity in the appended claims. The invention itself, together with -- ~ --. :
~ ~' ' . ' ' ' \
further objects, features and advantages thereof, may best be understood by reference to the following descrip-tion when taken in conjunction with the accompanying drawings.
FIG. 1 is a simplified schematic diagram of the novel power supply ripple filter circuit accordiny to the invention.
FIG. 2 i5 a detailed schematic diagram of the pre-ferred embodiment of the novel power supply ripple filter circuit according to the invention.
Detailed Description of the Preferred Embodiment Referring to FIG. 1, there is shown a simplified schematic diagram of an active power supply ripple filter 10 constructed in accordance with the present invention (and shown with a positive supply of voltayes). The output of a DC power supply (not shown) is applied to the active filter input terminal 12. The anode of a diode 14 is coupled to the input terminal 12, as shown, and the `~ cathode of the diode 14 is coupled to a node 16. AlSo coupled to the node 16 is a current source 17 which is coupled Erom the node 16 to ground, as shown, to provide a current throuyh the diode 14 when a DC voltaye is applied to the input terminal 12. This results in a voltage at the node 16 which is one diode drop (approxi-mately .7 volt~ below the applied ~C voltage. Thus, a refer~ence voltage tracking one diode drop below the input DC voltage is generated at node 16.
:
~; The reference node 16 is coupled to the input of a low pass ~ilter 18, which filters the DC reference volt-age. A simple RC filter can be used to provide a high degree of filtering, howevert~multiple pole networks can also be used to provi~e additional filteriny. The output ,"
:
.:~
:: ~
~ :
~ 9 ~
of the low pass filter 18 is coupled, as shown, to the inverting input 24 of a gain stage 22~ The output 28 of the gain stage 22 is coupled to the control terminal 32 (iOe., the base) of a control transistor 30. The emitter 31 of the control transistor 30 is coupled, as shown, to the input terminal 12, while the collector 33 of the transistor 30 is coupled to an output terminal 36. Also coupled to the output terminal 36 is the non-inverting input 26 of the gain stage 22, thereby providing negative feedback.
In operation, the circuit of FIG. 1 functions as described below. The output of a DC power sup~ly (not shown), having a small ripple component, is applied to the input terminal 12. This voltage, together with the current source 17, forward biases the diode 14 resultiny in a DC reference voltage with ripple at the node 16 which tracks one diode drop below the input DC voltage.
This reference voltage is filtered by the low pass filter 18 providing a filtered ~C reference to the inverting input 24 of the gain stage 22. The output voltage at the collector 33 of the control transistor 30 is fed back to the non-inverting input 26 of the gain stage 22. Thus, the gain stage 22 acts as a comparator with its output - coupled to the base 32 of the control transistor 30, thereby controlling the current through the control tran-sistor 30. If the output voltage at the output terminal 36 drops, the voltage on the noninverting input 26 of the gain stage 22 will drop, causing the difference between the reference voltage at the inverting input 24 and the non-inverting input 26 to increase~ This will result in .
a decrease in the output voltage of the gain stage 22 applied to the base 32 of the control transistor 30, and will drive the control transistor harder~ pulling up the output voltaye of the output terminal 36.
~`t ::: :
' ' :: ~
Since the reference voltaye at the inverting input 24 of the gain sta~e 22 tracks one diode drop below the input voltac~e, the voltage across the transistor 30 is maintained at approximately one diode clrop, independent 5 of the input voltage. This provides the advantaye of maintaining a low input-output voltaye drop for the circuit, as well as minimizing the power dissipation of the control transistor 30. In addition, the control transistor 30 is kept out of saturation over a wide 10 temperature range. Finally, since the gain stage 22 can have a very low input bias current and good noise charac-teristics, great flexibility is possible in the choice of ` the values of resistance and capacitance for the low pass filter 18, while still providiny a high degree of supply 15 filtering.
Referring now to FIG. 2, there is shown a detailed schematic diagram of the preferred ernbodiment of the novel power supply filter according to the invention. An input terminal 112 is coupled to a reference node 117 via 20 a series string of diodes 113, 114, 115, as shown. The reference node 117 is coupled to ground via a current source resistor 116 me reference node 117 is also coupled to a resistor 119, which is connected to the base 123 of a transistor 122, and to one electrode of a filter 25 capacitor 121. The second electrode of the capaci~or 121 -~ is coupled -to ground. rrhe emitter 126 oE the transistor 122 is coupled to ground via a resistor 154 and t~e collector 125 is coupled to the input terminal 112 via a resistor 128, as shown Also coupled to the collector 30 125 of the transistor 122 is the base 129 of a transistor ~ 134. The collector 137 of the transistor 134 is coupled ; ~ directly to ground, whiIe the emitter 138 is connected to the base 141 of a transistor 140. The collector 143 of the transistor 140 is connected to the base 132 of a 35 control transistor 130. It can be seen that this .:
: `
' :~ :
' ~
arrangement of the transistors 134 and 140 forms a Darlington pair configuration. The emitter 131 of the control transistor 130 is connected to the input terminal 112, and the collector 133 is connected to an output terminal 136, as shown. A series string of three diodes, 150, 151 and 152, are coupled from the output terminal 136 to the resistor 154, as shown, thereby providing a negative feedback connection to the emitter 126Of the transistor 122.
In operation, a DC power supply voltage having a small ~C ripple component is applied to the input terminal 112. This DC voltage applied across the series combination composed of the diodes 113~ 114, 115 and the resistor 116, will forward bias the diodes 113, 114, 115.
This will result in a reference voltage VR generated at the reference node 117, which tracks three diode drops below the input ~C voltage at the input terminal 112.
This reference voltage VR is filtered by the low pass filter formed by the resistor 119 and the capacitor 121.
;20 'rhe filtered reference voltage is applied to the base of the transistor 123. The voltage generated at the col lector 125 is coupled to the base 132 of the control transistor 130 via the Darlington pair composed of the ;transistors 134 and 1400 The Darlinyton pair provides a high degree of current gain. Thus, the transistors 122, 134 and 140 form a high gain staye with a high output current capability and an added two diode voltage drop.
The reference voltage at the base 123 of the transistor 122 is approximately three diode drops below the input DC
voltageq In addition, the feedback through the three diodes 150, 151, 152 will cause the voltage at the emitter 126 of the transistor 122 to be three diode drops below the voltage at the output terminal 136. Therefore, the voltage across the control transistor 130 will be maintained at approximately one diode drop. An :
. ~ . . .
: ~' . ' ., ' ' : ' .
additional consequence of the feedback loop is that an output voltage drop will cause the voltage at the emitter 126 to drop, causing the transistor 122 to turn on more.
This will drive the transistor 130 harder, pulling up the output voltage at the output terminal 136.
Since this novel active power supply ripple filter tracks the input voltage by maintaining approximately one diode drop across the control transistor 130, it there-fore has the dual advantage of low input-output voltage differential and low power dissipation. Also, since the voltage across the reference and feedback diode strings change with temperature in the same manner, the circuit provides the advantage of compensating for temperature changes within the circuit. In addition, since only the base current of the transistor 122 goes through the filter resistor 119, a pinch resistor can be used for the resistor llg and an NPN transistor can be used for the transistor 122 when the circuit is integrated. A pinch resistor is an integrated circuit resistor with high value of resistance that tracks the NPN beta of the cir-cuit transistors. Thus r a constant voltage drop across the high value resistor can be obtained. This permits the use of a larger value of resistance than could other-wise be utilized, allowing smaller values of capacitance to achieve a desired filter cut-off frequency. Also of importance when integrating this circuit is the fact that no lateral PNP transistor would be required in the signal path since the PNP control transistor 130 is required to be external to the integrated circuit when using standard ~;~ 30 processiny technology due to the high current require-~ ment. In integrated circuits this reduces frequency -~ compensation problerns and provides improved noise charac~
teristics over a circuit requiring a lateral PNP in the ':
signal path. Thus, this novel circuit is highly suitable for monolithic integration.
: ~, :' .
,~; ;
~ ~ , - . , ~
~ ~ :
It can be seen from the above description that an active power supply ripple filter has been provided which maintains minirnum voltage drop across it and minimum power dissipation in the control device. In addition, the invention provides temperature compensated operation, permits the use of smaller capacitances and is particu-larly suitable for monolithic fabrication.
While a preferred embodiment of the invention has been described and shown, it should be understood that other variations and rnodifications may be implemented.
It is therefore contemplated to cover by the present application any and all modifications and variations that fall wi~hin the true spirit and scope of the basic under-lying principles disclosed and claimed herein.
.
:
'~ :
~' ;~
. ~
.
Background of the Invention _ _ _ _ _ A. Field of the Invention The present invention relates to power supply circuitry and, in particular, to a low noise, low voltage drop, active power supply filter suitable for monolithic fabrication.
B. Description of the Prior Art In conventional communication circuitry it is often desirable to employ a power supply ripple filter which ~ will provide a well filtered, low noise supply voltaye ; capable of high output current and which drops as small a voltage as possible across the filter. Ripple filters I0 known in the prior art do not maintain a minimum voltage drop nor minimal noise leveLs. Further, prior art circuits require relatively large capacitance values to achieve a desired cut-off frequency and are not highly sultable for monolithic integration.
Accordingly, it is an object of the invention to provlde a low noise active power supply ripple filter capable of hiyh output currents while maintaining low voltage drop across the filter.
It is another object of the invention to provide a 20~ low~noise active power supply ripple fil~er which mini-mizes the capacitance values re~uired to achieve desired frequency rejecti~on characteristics.
It is yet another objec~t~of the invention to provide a low noise active power supply ripple filter which is ~ 25 particularly suitable Eor monolithic integration.
,~
: ' ' ' ' ' ' . ` . , , ~: , " , , , ` : " , : ~ : '' 1 ~ B ~
Briefly, in accordance with the invention a low noise active power supply filter capable of high output current is provided for elir~linating alternating current components from a direct current voltage, with a minimal input-output voltage drop. A control device such as a bipolar transistor is utilized with an input terminal coupled to the power supply and an output te~inal coupled to a load. rrhe control device controls and therefore to the power supply the current from the input terminal to the output terminal via a signal coupled to a control terrninal. A reference circuit coupled to the input terminal of -the control device provides a reference voltage which approximately tracks the power supply input voltage. An amplifier having its output coupled to the control terminal of the control device amplifies a signal applied across first and second input terminals. A fil-ter is coupled to the reference means to low pass filter the reference voltage and then couple the filtered refer-ence voltage to the first input of the amplifier means.
A feedback loop couples the control rneans output terminal to the second input of the amplifier means-The invention herein disclosed provides a low noiseactive power supply ripple filter capable of high output current which tracks the direct current supply voltage thereby maintaining a minimum voltage drop across the filter and low power dissipation. The filter also pro-vides some temperature compensation, permits the use of small vaIue filter capacitors and is particularly suit-able for monolitllic fabrication.
Brief ~escriptlon_of_the Drawings The features of the present invention which are believed to be novel are set forth wi-th particularity in the appended claims. The invention itself, together with -- ~ --. :
~ ~' ' . ' ' ' \
further objects, features and advantages thereof, may best be understood by reference to the following descrip-tion when taken in conjunction with the accompanying drawings.
FIG. 1 is a simplified schematic diagram of the novel power supply ripple filter circuit accordiny to the invention.
FIG. 2 i5 a detailed schematic diagram of the pre-ferred embodiment of the novel power supply ripple filter circuit according to the invention.
Detailed Description of the Preferred Embodiment Referring to FIG. 1, there is shown a simplified schematic diagram of an active power supply ripple filter 10 constructed in accordance with the present invention (and shown with a positive supply of voltayes). The output of a DC power supply (not shown) is applied to the active filter input terminal 12. The anode of a diode 14 is coupled to the input terminal 12, as shown, and the `~ cathode of the diode 14 is coupled to a node 16. AlSo coupled to the node 16 is a current source 17 which is coupled Erom the node 16 to ground, as shown, to provide a current throuyh the diode 14 when a DC voltaye is applied to the input terminal 12. This results in a voltage at the node 16 which is one diode drop (approxi-mately .7 volt~ below the applied ~C voltage. Thus, a refer~ence voltage tracking one diode drop below the input DC voltage is generated at node 16.
:
~; The reference node 16 is coupled to the input of a low pass ~ilter 18, which filters the DC reference volt-age. A simple RC filter can be used to provide a high degree of filtering, howevert~multiple pole networks can also be used to provi~e additional filteriny. The output ,"
:
.:~
:: ~
~ :
~ 9 ~
of the low pass filter 18 is coupled, as shown, to the inverting input 24 of a gain stage 22~ The output 28 of the gain stage 22 is coupled to the control terminal 32 (iOe., the base) of a control transistor 30. The emitter 31 of the control transistor 30 is coupled, as shown, to the input terminal 12, while the collector 33 of the transistor 30 is coupled to an output terminal 36. Also coupled to the output terminal 36 is the non-inverting input 26 of the gain stage 22, thereby providing negative feedback.
In operation, the circuit of FIG. 1 functions as described below. The output of a DC power sup~ly (not shown), having a small ripple component, is applied to the input terminal 12. This voltage, together with the current source 17, forward biases the diode 14 resultiny in a DC reference voltage with ripple at the node 16 which tracks one diode drop below the input DC voltage.
This reference voltage is filtered by the low pass filter 18 providing a filtered ~C reference to the inverting input 24 of the gain stage 22. The output voltage at the collector 33 of the control transistor 30 is fed back to the non-inverting input 26 of the gain stage 22. Thus, the gain stage 22 acts as a comparator with its output - coupled to the base 32 of the control transistor 30, thereby controlling the current through the control tran-sistor 30. If the output voltage at the output terminal 36 drops, the voltage on the noninverting input 26 of the gain stage 22 will drop, causing the difference between the reference voltage at the inverting input 24 and the non-inverting input 26 to increase~ This will result in .
a decrease in the output voltage of the gain stage 22 applied to the base 32 of the control transistor 30, and will drive the control transistor harder~ pulling up the output voltaye of the output terminal 36.
~`t ::: :
' ' :: ~
Since the reference voltaye at the inverting input 24 of the gain sta~e 22 tracks one diode drop below the input voltac~e, the voltage across the transistor 30 is maintained at approximately one diode clrop, independent 5 of the input voltage. This provides the advantaye of maintaining a low input-output voltaye drop for the circuit, as well as minimizing the power dissipation of the control transistor 30. In addition, the control transistor 30 is kept out of saturation over a wide 10 temperature range. Finally, since the gain stage 22 can have a very low input bias current and good noise charac-teristics, great flexibility is possible in the choice of ` the values of resistance and capacitance for the low pass filter 18, while still providiny a high degree of supply 15 filtering.
Referring now to FIG. 2, there is shown a detailed schematic diagram of the preferred ernbodiment of the novel power supply filter according to the invention. An input terminal 112 is coupled to a reference node 117 via 20 a series string of diodes 113, 114, 115, as shown. The reference node 117 is coupled to ground via a current source resistor 116 me reference node 117 is also coupled to a resistor 119, which is connected to the base 123 of a transistor 122, and to one electrode of a filter 25 capacitor 121. The second electrode of the capaci~or 121 -~ is coupled -to ground. rrhe emitter 126 oE the transistor 122 is coupled to ground via a resistor 154 and t~e collector 125 is coupled to the input terminal 112 via a resistor 128, as shown Also coupled to the collector 30 125 of the transistor 122 is the base 129 of a transistor ~ 134. The collector 137 of the transistor 134 is coupled ; ~ directly to ground, whiIe the emitter 138 is connected to the base 141 of a transistor 140. The collector 143 of the transistor 140 is connected to the base 132 of a 35 control transistor 130. It can be seen that this .:
: `
' :~ :
' ~
arrangement of the transistors 134 and 140 forms a Darlington pair configuration. The emitter 131 of the control transistor 130 is connected to the input terminal 112, and the collector 133 is connected to an output terminal 136, as shown. A series string of three diodes, 150, 151 and 152, are coupled from the output terminal 136 to the resistor 154, as shown, thereby providing a negative feedback connection to the emitter 126Of the transistor 122.
In operation, a DC power supply voltage having a small ~C ripple component is applied to the input terminal 112. This DC voltage applied across the series combination composed of the diodes 113~ 114, 115 and the resistor 116, will forward bias the diodes 113, 114, 115.
This will result in a reference voltage VR generated at the reference node 117, which tracks three diode drops below the input ~C voltage at the input terminal 112.
This reference voltage VR is filtered by the low pass filter formed by the resistor 119 and the capacitor 121.
;20 'rhe filtered reference voltage is applied to the base of the transistor 123. The voltage generated at the col lector 125 is coupled to the base 132 of the control transistor 130 via the Darlington pair composed of the ;transistors 134 and 1400 The Darlinyton pair provides a high degree of current gain. Thus, the transistors 122, 134 and 140 form a high gain staye with a high output current capability and an added two diode voltage drop.
The reference voltage at the base 123 of the transistor 122 is approximately three diode drops below the input DC
voltageq In addition, the feedback through the three diodes 150, 151, 152 will cause the voltage at the emitter 126 of the transistor 122 to be three diode drops below the voltage at the output terminal 136. Therefore, the voltage across the control transistor 130 will be maintained at approximately one diode drop. An :
. ~ . . .
: ~' . ' ., ' ' : ' .
additional consequence of the feedback loop is that an output voltage drop will cause the voltage at the emitter 126 to drop, causing the transistor 122 to turn on more.
This will drive the transistor 130 harder, pulling up the output voltage at the output terminal 136.
Since this novel active power supply ripple filter tracks the input voltage by maintaining approximately one diode drop across the control transistor 130, it there-fore has the dual advantage of low input-output voltage differential and low power dissipation. Also, since the voltage across the reference and feedback diode strings change with temperature in the same manner, the circuit provides the advantage of compensating for temperature changes within the circuit. In addition, since only the base current of the transistor 122 goes through the filter resistor 119, a pinch resistor can be used for the resistor llg and an NPN transistor can be used for the transistor 122 when the circuit is integrated. A pinch resistor is an integrated circuit resistor with high value of resistance that tracks the NPN beta of the cir-cuit transistors. Thus r a constant voltage drop across the high value resistor can be obtained. This permits the use of a larger value of resistance than could other-wise be utilized, allowing smaller values of capacitance to achieve a desired filter cut-off frequency. Also of importance when integrating this circuit is the fact that no lateral PNP transistor would be required in the signal path since the PNP control transistor 130 is required to be external to the integrated circuit when using standard ~;~ 30 processiny technology due to the high current require-~ ment. In integrated circuits this reduces frequency -~ compensation problerns and provides improved noise charac~
teristics over a circuit requiring a lateral PNP in the ':
signal path. Thus, this novel circuit is highly suitable for monolithic integration.
: ~, :' .
,~; ;
~ ~ , - . , ~
~ ~ :
It can be seen from the above description that an active power supply ripple filter has been provided which maintains minirnum voltage drop across it and minimum power dissipation in the control device. In addition, the invention provides temperature compensated operation, permits the use of smaller capacitances and is particu-larly suitable for monolithic fabrication.
While a preferred embodiment of the invention has been described and shown, it should be understood that other variations and rnodifications may be implemented.
It is therefore contemplated to cover by the present application any and all modifications and variations that fall wi~hin the true spirit and scope of the basic under-lying principles disclosed and claimed herein.
.
:
'~ :
~' ;~
. ~
.
Claims (5)
1. A low noise electronic power supply filter circuit capable of high output currents for eliminating alternating current components from a direct current power supply and for tracking the direct current voltage of said power supply, comprising:
a) control means having a control terminal, an input terminal and an output terminal, said input termi-nal coupled to the power supply and said output terminals adapted to be coupled to a load, said control means controlling current from the input terminal to the output terminal;
b) reference means,coupled to the control means input terminal for generating a reference voltage which approximately tracks the power supply voltage;
c) amplifier means having an output coupled to the control terminal and having first and second input terminals, for amplifying a signal applied across the input terminals;
d) filter means, having an input coupled to the reference means for low pass filtering the reference voltage, and having an output coupled to the first input of the amplifier means thereby coupling the filtered reference voltage to said amplifier means; and e) feedback means coupled from the control means output terminal to the second input of the ampli-fier means.
a) control means having a control terminal, an input terminal and an output terminal, said input termi-nal coupled to the power supply and said output terminals adapted to be coupled to a load, said control means controlling current from the input terminal to the output terminal;
b) reference means,coupled to the control means input terminal for generating a reference voltage which approximately tracks the power supply voltage;
c) amplifier means having an output coupled to the control terminal and having first and second input terminals, for amplifying a signal applied across the input terminals;
d) filter means, having an input coupled to the reference means for low pass filtering the reference voltage, and having an output coupled to the first input of the amplifier means thereby coupling the filtered reference voltage to said amplifier means; and e) feedback means coupled from the control means output terminal to the second input of the ampli-fier means.
2. The low noise electronic power supply filter circuit of claim 1, wherein the reference means maintains the reference voltage approximately one diode drop below the power supply voltage.
3. The low noise power supply filter circuit of claim 1 wherein the reference means comprises at least one diode in series with a resistor, coupled to the power supply.
4. The low noise power supply filter circuit of claim 1, wherein the feedback loop comprises at least one diode having an anode coupled to the control means output terminal and a cathode coupled to the second input of the amplifier means such that approximately one diode drop is maintained across the control means.
5. The low noise electronic power supply filter circuit of claim 4, wherein the control means is a bipolar transistor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/178,490 | 1980-08-15 | ||
| US06/178,490 US4327319A (en) | 1980-08-15 | 1980-08-15 | Active power supply ripple filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1164941A true CA1164941A (en) | 1984-04-03 |
Family
ID=22652740
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000380912A Expired CA1164941A (en) | 1980-08-15 | 1981-06-30 | Active power supply ripple filter |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4327319A (en) |
| CA (1) | CA1164941A (en) |
Families Citing this family (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4587476A (en) * | 1983-09-29 | 1986-05-06 | The Boeing Company | High voltage temperature compensated foldback circuit |
| IT1203335B (en) * | 1987-02-23 | 1989-02-15 | Sgs Microelettronica Spa | MINIMUM VOLTAGE DROP VOLTAGE REGULATOR, SUITABLE TO SUPPORT HIGH VOLTAGE TRANSITORS |
| DE58902165D1 (en) * | 1988-01-18 | 1992-10-08 | Siemens Ag | CIRCUIT ARRANGEMENT FOR A VOLTAGE CONTROLLED CONSTANT VOLTAGE SOURCE WITH INPUT R-C-LINK. |
| CA1306006C (en) * | 1988-07-05 | 1992-08-04 | Yoshiaki Sano | Constant voltage source circuit |
| DE3834880A1 (en) * | 1988-10-13 | 1990-04-19 | Ant Nachrichtentech | METHOD FOR SUPPRESSING NOISE SIGNALS IN A CONSUMER SUPPLIED WITH DC VOLTAGE BY AN ACTUATOR, AND ARRANGEMENT AND APPLICATION |
| US5043686A (en) * | 1989-03-14 | 1991-08-27 | Harman International Industries, Inc. | Adaptive power line noise filter and switch for audio reproduction equipment |
| US5485077A (en) * | 1993-08-09 | 1996-01-16 | Aphex Systems, Ltd. | Concentric servo voltage regulator utilizing an inner servo loop and an outer servo loop |
| US5548165A (en) * | 1994-07-18 | 1996-08-20 | Regents Of The University Of Minnesota | Hybrid filter for reducing distortion in a power system |
| IL112928A0 (en) * | 1995-03-07 | 1995-06-29 | Neerman Haim | Electronic filter |
| US5736843A (en) * | 1995-04-27 | 1998-04-07 | Silicon Graphics, Inc. | Efficient ultra low drop out power regulator |
| US5612612A (en) * | 1995-12-21 | 1997-03-18 | Aphex Systems, Ltd. | Functional control block for voltage regulator with dual servo loops |
| FR2787648B1 (en) * | 1998-12-17 | 2001-06-15 | St Microelectronics Sa | CONVERTER FROM A HIGH ALTERNATE VOLTAGE TO A CONTINUOUS LOW VOLTAGE |
| US6489755B1 (en) | 2000-09-18 | 2002-12-03 | Adtran, Inc. | Active ripple and noise filter for telecommunication equipment powering |
| US6404174B1 (en) | 2000-10-27 | 2002-06-11 | Adtran, Inc. | Circuit for in-system programming of memory device |
| ATE497201T1 (en) | 2002-04-23 | 2011-02-15 | Nanopower Solutions Inc | NOISE FILTER CIRCUIT |
| US7030595B2 (en) * | 2004-08-04 | 2006-04-18 | Nanopower Solutions Co., Ltd. | Voltage regulator having an inverse adaptive controller |
| US7825822B2 (en) * | 2005-04-01 | 2010-11-02 | Cepia, Llc | System and method for extracting and conveying modulated AC signal information |
| JP4745023B2 (en) * | 2005-11-07 | 2011-08-10 | フリースケール セミコンダクター インコーポレイテッド | Ripple filter circuit |
| US20100066326A1 (en) * | 2008-09-16 | 2010-03-18 | Huang Hao-Chen | Power regulator |
| US8564256B2 (en) * | 2009-11-18 | 2013-10-22 | Silicon Laboratories, Inc. | Circuit devices and methods of providing a regulated power supply |
| US8901905B2 (en) | 2011-02-18 | 2014-12-02 | Iowa State University Research Foundation, Inc. | System and method for providing power via a spurious-noise-free switching device |
| CN105553244B (en) * | 2015-12-22 | 2018-05-29 | 矽力杰半导体技术(杭州)有限公司 | Electromagnetic interface filter and apply its Switching Power Supply |
| KR102517759B1 (en) * | 2016-08-31 | 2023-04-03 | 엘지디스플레이 주식회사 | Power supply unit and display device including the same |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2995697A (en) * | 1957-02-18 | 1961-08-08 | Bell Telephone Labor Inc | Transistor filter |
| US3215928A (en) * | 1960-12-15 | 1965-11-02 | Aiken William Ross | Volume changer employing a magnetic responsive resistor and providing a direct or inverse relation of output to input |
| NL7212971A (en) * | 1972-09-26 | 1974-03-28 | ||
| JPS5244420B2 (en) * | 1973-06-11 | 1977-11-08 | ||
| US3868562A (en) * | 1973-08-02 | 1975-02-25 | Us Scientific Instruments | Energy storage method and apparatus |
| JPS51122745A (en) * | 1975-04-21 | 1976-10-27 | Toshiba Corp | Dc constant-voltage power source circuit |
| GB1549064A (en) * | 1975-10-27 | 1979-08-01 | Outokumpu Oy | Method of the temperature stability of a regulated voltage source and a stabilized voltage source for carrying out the method |
| US4017779A (en) * | 1976-03-22 | 1977-04-12 | Motorola, Inc. | Battery isolator |
| US4048523A (en) * | 1976-10-01 | 1977-09-13 | Paoli High Fidelity Consultants Inc. | Electronic filter with active elements |
| US4099155A (en) * | 1976-11-10 | 1978-07-04 | Rte Corporation | Gas actuated high voltage bushing |
| US4064448A (en) * | 1976-11-22 | 1977-12-20 | Fairchild Camera And Instrument Corporation | Band gap voltage regulator circuit including a merged reference voltage source and error amplifier |
| US4103220A (en) * | 1977-04-04 | 1978-07-25 | Gte Lenkurt Electric (Canada) Ltd. | Low dissipation voltage regulator |
-
1980
- 1980-08-15 US US06/178,490 patent/US4327319A/en not_active Expired - Lifetime
-
1981
- 1981-06-30 CA CA000380912A patent/CA1164941A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4327319A (en) | 1982-04-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1164941A (en) | Active power supply ripple filter | |
| US3939399A (en) | Power circuit with shunt transistor | |
| US4629973A (en) | Current stabilizing circuit operable at low power supply voltages | |
| US4122403A (en) | Temperature stabilized common emitter amplifier | |
| US4415868A (en) | One and one half pole audio power amplifier frequency compensation | |
| US4728902A (en) | Stabilized cascode amplifier | |
| US4460876A (en) | Low consumption, wide-band linear amplifier operating in sliding class A | |
| US4593252A (en) | Enhanced transconductance amplifier | |
| CA1194151A (en) | Circuit arrangement comprising a differential amplifier | |
| US5760651A (en) | Inductorless voltage biasing circuit for and Ac-coupled amplifier | |
| JPH04369907A (en) | High frequency amplifier circuit | |
| EP0093140B1 (en) | Amplifier suitable for low supply voltage operation | |
| US5541550A (en) | Electronic load resistor circuit | |
| GB2079078A (en) | Gain controlled tv if amplifier | |
| JP2765257B2 (en) | Amplifier circuit | |
| JPS6127211Y2 (en) | ||
| US4513251A (en) | Miller compensation for an operational amplifier | |
| US4132963A (en) | Gain controlled signal amplifier | |
| US4139825A (en) | Audio frequency amplifier | |
| JPS646583Y2 (en) | ||
| JPS63184408A (en) | Transistor bias circuit | |
| JPH021949Y2 (en) | ||
| JPS6310926A (en) | Optical reception circuit | |
| JPS6214725Y2 (en) | ||
| JPS6336745Y2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |