GB2500053A

GB2500053A - DC voltage converter with current sensor and voltage booster

Info

Publication number: GB2500053A
Application number: GB1204145.5A
Authority: GB
Inventors: Charles Wesley Sterling
Original assignee: STERLING POWER PRODUCTS
Current assignee: STERLING POWER PRODUCTS
Priority date: 2012-03-09
Filing date: 2012-03-09
Publication date: 2013-09-11
Also published as: GB201204145D0

Abstract

A DC-DC converter allows an input voltage (particularly from a battery charger) to be boosted to a higher voltage, particularly to allow batteries under charge to absorb more current. The converter provides a regulated DC voltage at specific preset charging profiles depending on the type of battery. The voltage converter comprises three main sections, a current sensing section, a voltage boosting section and a micro processing section. The current sensing section comprises a shunt and a voltage amplifier. The voltage booster is a switch-mode boost converter comprising coils, capacitors, diodes, field-effect transistors (FETs) and a boost current sensor. The microprocessor is a chip with software installed. It stores information of battery charging profiles and the FET switching to produce the desired output voltage. The converter may be arranged within a self contained box or integrated as part of a battery charger.

Description

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A DC voltage converter with current sensor and voltage booster

Description

Field of Invention

The present invention allows you to convert an input voltage (direct current DC) into a higher output voltage (direct current DC).

Background to Invention

The invention allows users to retro fit this product to a lead acid/lithium style battery charger. The device fits onto the output terminal(s) of the battery charger and provides an increased voltage at the batteries(y). As a basic schematic:

Battery charger(xV) - (xV)voltage converter(>xV) - (>xV)battery

The benefits of increasing voltage are to increase levels of current that can be absorbed by the battery - the faster it can absorb current the faster the battery is recharged. So, why don't battery chargers just charge at a higher voltage? All battery chemistries can only handle so high a voltage; to the extent, whereby, each battery chemistry is attributed a particular charging pattern, known as a charging profile. For instance, a 12V GEL lead acid battery, where the electrolyte (the solution the redox reaction occurs in) is jellified, cannot handle a higher voltage than 14.1V. If this voltage is exceeded the gel starts to form more and more pockets of air around the plates the more they become over charged - this is a process called 'gassing'. Gassing occurs when the high charge rate (energy) splits up the water in the electrolyte and turns it into hydrogen gas and oxygen gas, this gas disappears through valves in the side of the battery. The more air that forms around the plates the fewer electrolytes there is exposed to the plate - resulting in reducing performance. In contrast a 12V OPEN lead acid battery will handle a voltage of 14.8V. Here, the electrolyte is a solution, not a gel, no pockets of air form - gassing events will occur, but, because they are open, they can be topped up with more distilled water, open lead acid batteries can therefore be charged faster and can be maintained (by adding water), unlike that of gel. Due to these charging sensitivities and the myriad of battery chemistries on the market each of these battery chemistries requires its own unique charging profile for the most effective charge. Most charging voltages lie somewhere between 14.1V and 14.8V (ex. Calcium - 15.1V).

This issue only arises within the industry when people have different battery chemistry types on board their boat/vehicle. This is a very common issue and is occurring more and more. People, as an example, will use a GEL lead acid battery to start their engine (starter battery), as they are particularly good at performing this function and they shall use an OPEN lead acid for their domestic battery bank (to run on board appliances). The vast majority of battery chargers on the market (99.9%) will only be able to provide 1 charging profile at any one time. For instance, you have a two output battery charger, one of the outputs goes to the GEL starter and the second output goes to the OPEN domestic bank. If you set the battery charger to the OPEN profile you will gas the GEL and prematurely destroy it. If you set the

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charger to GEL you will not charge the OPEN lead acid domestics at a fast enough rate, the OPEN batteries will be vastly under charged and they tend to be part of a larger bank (to supply the domestic appliance) and require large amounts of current, which is not happening at 14.1V. Therefore, the ability to charge the GEL battery at 14.1V and to boost the voltage on the second output (OPEN) to 14.8V is in increasing demand within the industry.

Brief Description of Invention

Refer to drawings

The design behind this voltage booster comprises of three main sections: a current sensing section, a voltage boosting section (both shown on the fig 1) and a micro processing section (software) which controls the hardware. The electronics can be fit into a standalone / retro fit style box or it can be fit into a battery charger itself.

Please refer to: Figure 1 - wiring schematic (detailed)

Figure 2 - demonstrates a schematic (basic)

The current sensing section is comprised of a shunt and a voltage amplifier. The voltage amplifier amplifies the voltage across the shunt (known resistance) so you can measure the current more effectively. The data is processed by the micro processing section. Monitoring current is essential for safety reasons / errors messages and it also provides information for displaying information on remote controls or product mounted panels - if required.

The voltage booster is a switch mode boost converter. It is comprised of coils, capacitors, diodes, field-effect transistors (FETs) and a boost current sensor. The coil acts like a 'spring board' bringing the input voltage right the way down to zero, the back electro motive force (EMF) allows it to spring back up to a higher voltage (the coil propagates this boost). The coil is controlled by a switching system comprised of FETs + a driver. The FETs switch to enable the 'spring board' effect on the coil. The driver is required to clean up this switching process. The result from the spring board at the coil, as stated, is at higher voltage, this is captured by a series of diodes, which are a one way valve (semi conductor), they essentially capture this boosted voltage and deliver it to the output stud (the battery you wish to charge). Capacitors are used on the output connectors to smooth the output current, unregulated, there would be spikes on the output.

The microprocessor is a chip with software installed. It stores the information of the charging profiles (for different battery chemistries). The software controls the FETs so they switch to create the desired output voltage via the 'spring back' effect. The microprocessor is attached to the connectors such as the: CL_1_SENSOR, BOOST_FET, i_FBACK, DRV_FET_GND_0VS, INDJOUT, LK3 (refer to fig 1).

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Claims

1. A system that will take DC voltage from an input and convert to a higher DC voltage on the output.

2. A system that will take DC voltage from the input and provide a higher regulated DC voltage output at specific preset charging profiles stored on a microprocessor.

3. A system, that uses a system described in claim 2, using a coil to 'spring board' the voltage from an input voltage, down to zero voltage, then back to a higher voltage.

4. A system, that uses a system described in claim 3, with a series of diodes to capture the increased voltage produced by the coil.

5. A system, that uses a method described in claim 4, with capacitors on the output connectors to smooth and reduce spikes when charging.

6. A system, as specifically described in claim 5, with a FET + driver switching system, which provides the clean switching mechanism for the 'spring boarding' effect of the coils.

7. A system, described in claim 6, whereby the FET driven switching system is controlled by a boost current sensor which monitors current going to ground (OV).

8. A system, described in claim 7, which uses a current sensor on the input (comprised of a shunt and a voltage amplifier), this allows the monitoring of current, desirable for external monitoring (via remote control) and to display warning/safety features.

9. A system, described in claims 1-8, which is controlled by a central micro processing unit which monitors and integrates the various regions of the circuit board.

10. A system, which can take some or all of the above claims, and to arrange it within a self contained box or integrated as part of a battery charger.