Stabilized laptop power supply. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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The proposed stabilized power supply is designed to power laptops and charge their lithium-ion batteries, as well as lead-acid batteries of uninterruptible power supplies. The device provides for switching the output voltage depending on the type and nominal voltage of the battery.
Charging a deeply discharged laptop battery is not always possible due to the operation of the protection built into the battery. Disassembly of some of these battery packs showed that all the elements are in good order, the microcircuit that performs the protection function is not damaged.
In such cases, it is possible to pre-charge the battery by directly connecting the charger to the batteries in the appropriate polarity, bypassing the protection unit.
A similar situation happened to me with a faulty laptop, the battery of which was completely discharged in a year. After repairing the laptop, it was proposed to buy a new battery pack to replace the failed one, since the standard laptop charger (AD 82000, 19 V, 1,58 A) "refused to charge the battery."
There was an idea to develop a homemade device for charging the battery. Such a device was assembled, and after its use, the battery began to charge normally.
The charger contains a stabilized power supply with output voltage and current protection in accordance with the nameplate data of the laptop battery.
Today, the industry produces a wide range of microcircuit voltage stabilizers, both adjustable and fixed, with very high parameters. However, for most of them, the maximum load current does not exceed 1,5 A. Therefore, it was decided to make a laptop power supply based on a voltage stabilizer microcircuit with a power regulating transistor.
Main Specifications
- Rated mains voltage, V.......220
- Power consumption, no more than, W ....... 60
- Output voltage, V.....12/19
- Maximum load current, A.....2
- Output closing current, A ....... 0,5
The laptop power supply circuit is shown in fig. 1. It contains a transformer T1 with switching elements SA1 and protection FU1, RK1. From the secondary winding of the transformer, an alternating voltage of 24 V is supplied to the diode bridge VD1, from which, after rectification and smoothing of the ripples by the capacitor C1, it is supplied to the stabilizer DA1 and the regulating transistor VT1. Capacitor C2 eliminates high-frequency interference from the mains into the load.
Rice. 1. Diagram of a laptop power supply
Since there are no devices with an output voltage of 403 V in the KMP19 series of microcircuits, a microcircuit for a nominal voltage of 12 V is used, and a voltage boost is organized by connecting a VD2 zener diode with a stabilization voltage of 6,8 V to the output circuit 6 of the microcircuit. The current of the zener diode sets the resistor R4. Switch SA2 switches the output voltage from 12 V when the switch contacts are closed to 19 V when they are open. Within a small range, the output voltage of the power supply can be adjusted by resistor R1.
All elements of the device, with the exception of switches, a transformer and protection elements, are mounted on a board made of fiberglass laminated on one side. Its drawing is shown in Fig. 2.
Rice. 2. Drawing board elements
All elements of the device, with the exception of switches, a transformer and protection elements, are mounted on a board made of fiberglass laminated on one side. Its drawing is shown in Fig. 2.
The device uses fixed resistors S2-29, MLT-0,25, variable - SP-3-23. Oxide capacitors - imported, C2 - ceramic K10-17.
The KMP403EN4A microcircuit is interchangeable with a similar one from the K403 series, in any version it is installed on a heat sink with dimensions of 55x30 mm. The KT829A transistor can be replaced by any of the KT8108 series or imported C3461, it is also placed on a heat sink with dimensions of 100x30 mm.
We will replace the GBU706 diode bridge with a bridge RBV606, GBU606, KBL406, 1KBR210 or another, designed for a forward current of more than 2 A and a reverse voltage of at least 100 V.
In the author's version, the transformer XL15-P-EC is used in the power supply. It can be replaced by TN-46, four secondary windings of 6,3 V each for a current of 2,38 A, which are connected in series, or by transformers of the TPP, TS series, the secondary windings of which have a voltage of 24 V at a load current of 2 A.
To check, a load is connected to the output of the power supply, for example, an incandescent lamp for a voltage of 24 V with a power of 50 W, and an output voltage of 1 V is set with resistor R19. When charging batteries, this resistor sets the charging current. For control, a 5 A ammeter is included in the positive circuit.
Authors: A. Vanteev, V. Konovalov
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The US banking system plans to replace obsolete and technically vulnerable magnetic stripe plastic credit cards, which are now used by residents of the country for cashless payments, with a new type of card. According to the Wall Street Journal, this modernization will be carried out everywhere in October 2015.
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