GB2068607A - Voltage regulator circuit - Google Patents
Voltage regulator circuit Download PDFInfo
- Publication number
- GB2068607A GB2068607A GB8036210A GB8036210A GB2068607A GB 2068607 A GB2068607 A GB 2068607A GB 8036210 A GB8036210 A GB 8036210A GB 8036210 A GB8036210 A GB 8036210A GB 2068607 A GB2068607 A GB 2068607A
- Authority
- GB
- United Kingdom
- Prior art keywords
- voltage
- pass device
- circuit
- voltage regulator
- output
- 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.)
- Withdrawn
Links
- 238000012544 monitoring process Methods 0.000 claims abstract description 6
- 230000003287 optical effect Effects 0.000 claims abstract description 4
- 230000001939 inductive effect Effects 0.000 claims description 2
- 238000012806 monitoring device Methods 0.000 abstract 1
- 239000003990 capacitor Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/563—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices including two stages of regulation at least one of which is output level responsive, e.g. coarse and fine regulation
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Automation & Control Theory (AREA)
- Dc-Dc Converters (AREA)
Abstract
A voltage regulator for a power supply circuit has a pass device e.g. transistor 7 in series with the circuit output, means 12,13 for monitoring the output voltage of the circuit, and a linear regulator 14 for controlling the pass device 7 to maintain the monitored output voltage within predetermined limits. Means, eg. Schmitt trigger 16, are provided for monitoring the condition of the pass device 7 and for controlling the power supplied to it to maintain the voltage across the pass device within predetermined limits. The monitoring device 16 may be connected through an optical link 18 to a drive circuit 17 for a switching transistor 10. A current limiting arrangement 21,22 operates to inhibit transistor 10 if a short circuit occurs. <IMAGE>
Description
SPECIFICATION
Voltage regulator
The present invention relates to a voltage regulator which is particularly adapted for use in battery chargers and other D.C. power supply circuits.
It is of particular importance to maintain the output voltage of a battery charger within upper and lower voltage limits to ensure that effective charging is achieved. Conventionally the stability of a battery charger output is maintained by the use of a linear regulator controlling a pass device in series with the charger output The linear regulator monitors the charger output and controls the pass device to maintain that output within the desired limits. This system works satisfactorily but a substantial amount of power is dissipated in the pass device. This power dissipation is of particular significance in the case of for example chargers incorporated in fire alarm systems to maintain the charge of reserve power supply batteries as the chargers in such systems operate continuously.
It is an object of the present invention to provide a voltage regulator in which the above-described power dissipation is reduced.
According to the present invention, there is provided a voltage regulator for a power supply circuit comprising a pass device in series with the circuit output, means for monitoring the output voltage of the circuit, and means for controlling the pass device to maintain the monitored output voltage within predetermined limits, characterised by means for monitoring the condition of the pass device and means for controlling the power supplied to the pass device to maintain the voltage across the pass device within predetermined limits.
Preferably the condition of the pass device is monitored by a voltage sensor connected across the pass device and the power supplied to the pass device is controlled by a low frequency switch connected between the voltage regulator and its source of power. The switch may comprise a transistor responsive to a drive circuit controlled by the output of the voltage sensor. The voltage sensor and drive circuit are preferably connected by an optical feedback link.
The current through the switch may be sensed and the circuit disabled if the sensed current exceeds a predetermined threshold. The circuit may be disabled by latching the switch in its non-conductive condition.
An inductive/capacitive circuit is preferably provided to minimise ripple in the regulator output due to the action of the switch.
The invention also provides a power supply circuit incorporating a voltage regulator as characterised above.
An example of the present invention will now be described with reference to the accompanying drawing which is a circuit diagram of a battery charger including a voltage regulator according to the present invention.
The circuit shown in the drawing is intended to supply an output voltage at terminals 1 and 2 of 25V.
The circuit is driven from an A.C. supply via a transformer 3 and a full wave rectifier 4.
The output of the rectifier 4 is connected to terminal 1 via a supply line 5, an inductor 6, a pass device in the form of a transistor 7, and a diode 8, and to terminal 2 via a supply line 9 and a switch in the form of a transistor 10. A capacitor 11 is connected between the supply lines 5 and 9 to smooth the output of the rectifier 4.
A potential divider formed by resistors 12, 13 provides a signal proportional to the output voltage between terminals 1 and 2 to a linear regulator 14.
The linear regulator 14 is of conventional type and controls the transistor 7 to maintain the voltage between terminals 1 and 2 within predetermined limits. An auxiliary voltage detector 15 provides a fault indication if these predetermined limits are exceeded.
A voltage sensor in the form of a Schmitt trigger 16 is connected across the transistor 7. The sensor drives an LED (not shown) which controls a drive circuit 17 via an optical feedback link 18 providing voltage isolation. The drive circuit 17 in turn controls transistor 10. If the voltage across the transistor 7 is above the threshold of the Schmitt trigger, the drive circuit 17 turns transistor 10 off. If the voltage across the transistor 7 is below the threshold, the drive circuit 17 turns transistor 10 on. The power supplied to the pass device 7 is thus controlled to maintain the voltage across the pass device substantially constant, the voltage across a capacitor 19 rising when transistor 10 is on and falling when transistor 10 is off. A flyback diode 20 enables inductor 6 to release energy into capacitor 19 when the transistor 10 is off.
As the voltage across transistor 7 is limited by the action of the transistor 10, so too is the power dissipated in transistor 7. The transistor 10 is a switching device and therefore dissipates little power. It has been found that the described circuit substantially reduces the power dissipation in the pass device, for example from 200 watts to 25 watts for circuits of similar power power ratings.
The pulses of current through the transistor 10 are monitored by a winding 21 connected to a sensor 22.
If the monitored current exceeds a predetermined threshold, the sensor 22 applies an output on line 23 to the voltage sensor 16 which in turn inhibits transistor 10 via drive circuit 17. Thus the circuit is protected from damage due to for example short circuiting of terminals 1, 2. If the terminals 1, 2 were temporarily short circuited, when the short circuit was removed the capacitor 19 would charge up rapidly and unacceptably high currents would flow in the inductor 6 and hence through transistor 10.
The sensor 22 prevents this happening. The sensor 22 incorporates a delay device which maintains transistor 10 in its non-conductive state for a predetermined period. The conduction of transistor loins inhibited for this predetermined period to ensure that the current through inductor 6 falls significantly before transistor 10 can be turned on again.
A wide variety of voltage and power output requirements can be met using a number of circuits as described connected in parallel and/or series.
Claims (10)
1. A voltage regulator for a pbwer supply circuit comprising a pass device in series with the circuit output, means for monitoring the output voltage of the circuit, and means for controlling the pass device to maintain the monitored output voltage within predetermined limits, characterised by means for monitoring the condition of the pass device and means for controlling the power supplied to the pass device to maintain the voltage across the pass device within predetermined limits.
2. A voltage regulator according to claim 1, comprising a voltage sensor connected across the pass device to monitor the condition of the pass device and a low frequency switch connected between the voltage regulator and its source of power to control the supply of power to the pass device.
3. Avoltage regulator according to claim 2, wherein the switch comprises a transistor responsive to a drive circuit controlled by the output ofthe voltage sensor.
4. A voltage regulator according to claim 2 or 3, wherein the voltage sensor and drive circuit are connected by an optical feed back link.
5. A voltage regulator according to any one of claims 2 to 4, comprising means for sensing current through the switch and means for disabling the circuit of the sensed current exceeds a predetermined threshold.
6. A voltage regulator according to claim 5, wherein the disabling means comprises means for latching the switch in its non-conductive condition.
7. A voltage regulator according to any one of claims 2 to 6, comprising an inductive/capacitive circuit to minimise ripple in the regulator output due to the action of the switch.
8. A power supply circuit incorporating a voltage regulator according to any preceding claim.
9. A voltage regulator substantially as hereinbefore described with reference to the accompanying drawings.
10. A power supply substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8036210A GB2068607A (en) | 1980-01-19 | 1980-11-11 | Voltage regulator circuit |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8001870 | 1980-01-19 | ||
| GB8036210A GB2068607A (en) | 1980-01-19 | 1980-11-11 | Voltage regulator circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2068607A true GB2068607A (en) | 1981-08-12 |
Family
ID=26274217
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8036210A Withdrawn GB2068607A (en) | 1980-01-19 | 1980-11-11 | Voltage regulator circuit |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2068607A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0456990A2 (en) * | 1990-05-12 | 1991-11-21 | Daimler-Benz Aktiengesellschaft | Device to supply power to a computer system in a motor vehicle |
| EP0625814A1 (en) * | 1993-05-21 | 1994-11-23 | Schneider Electric Sa | Electronic trip device comprising a power supply control |
-
1980
- 1980-11-11 GB GB8036210A patent/GB2068607A/en not_active Withdrawn
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0456990A2 (en) * | 1990-05-12 | 1991-11-21 | Daimler-Benz Aktiengesellschaft | Device to supply power to a computer system in a motor vehicle |
| EP0456990A3 (en) * | 1990-05-12 | 1992-04-08 | Daimler-Benz Aktiengesellschaft | Device to supply power to a computer system in a motor vehicle |
| EP0625814A1 (en) * | 1993-05-21 | 1994-11-23 | Schneider Electric Sa | Electronic trip device comprising a power supply control |
| FR2705506A1 (en) * | 1993-05-21 | 1994-11-25 | Merlin Gerin | Electronic trip device comprising a power control device. |
| US5541499A (en) * | 1993-05-21 | 1996-07-30 | Merlin Gerin | Electronic trip device comprising a power supply control device |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |