GB2442528A

GB2442528A - Controller for electrically heated garments

Info

Publication number: GB2442528A
Application number: GB0619546A
Authority: GB
Inventors: Paul Telco
Original assignee: SMARTHEAT Ltd
Current assignee: SMARTHEAT Ltd
Priority date: 2006-10-04
Filing date: 2006-10-04
Publication date: 2008-04-09
Also published as: GB0619546D0

Abstract

A time-division controller for an electrically heated garment powered by an associated portable battery pack is so arranged that if a suitable external supply is connected, the controller will use that supply instead for heating the garment and also for charging the battery pack. The controller charges the battery pack only during off periods of the garment heating cycle thus limiting the power required from the external power source. Internal circuits prevent prolonged heating at high power settings and prevent operation in the event of over-temperature in the garment or the battery pack.

Description

Controls for Electrically Heated Garments This invention relates to

control circuits for the thermal control and safety of electricafly heated garments, pads and blankets Electrically heated garments are widely used in outdoor situations in cold climates. Fishermen, hunters, motorcyclists and emergency personnel who are exposed to extreme cold are known to rely on such aids.

Furthermore heated garments may be used by personnel inside buildings when it may be impractical to provide heating for an entire building or space such as an aircraft hangar or cold store.

A further use is by the elderly or disabled whose enforced sedentary circumstances might require rather more external warmth than would be acceptable or economic for more active people around them Electrical heating of garments is typically achieved by means of a pattern of resistance wires within the garment through which an electric current is caused to flow giving rise to the required wattage of heat dissipation.

It is a usual requirement in such garments that they should be able to heat up quickly to a required comfort level. It will be obvious that a fast heat-up feature requires that more heat energy will need to be available than would be needed once the required comfort level has been reached and this creates the need to ensure that overheating of the garment and or wearer is avoided.

Such overheating can occur locally if the garment carrying the heating wires is folded over on itsetf so that two or more heating wires are placed in close proximity to each other causing the temperature at that point to rise above a safe level for the wearer or even causing combustion to occur (so-called hot-spots).

Another overheating situation can occur if the temperature inside the garment is allowed to rise above normal body temperature of 370 Centigrade for a prolonged period when heat-stroke can occur. Such risks are at their greatest when the wearer falls asleep having forgotten to turn the power level down to a safe continuous level When electrically heated garments are in use with re-chargeable power supplies such as lithium-ion battery packs, it is possible to over-discharge said packs causing irreversible damage to them.

tt is possible that the heated garment may periodically be connected to a power source such as a vehicle battery for the purpose of heating the garment as well as simultaneously re-charging a connected battery pack. In such cwcumstances an excessive demand can be imposed on the supply system.

The present invention is based on a realization that it is possible to provide a method of automatic control that will obviate such dangers.

According to the present invention there is provided an electronic control means co-operating with a garment heating means comprising a garment heattng circuit, a temperature sensing means and a hot-spot sensing means.

The electronic control means is able to regulate the power input to the heating circuit while at the same time monitoring the temperature of the garment heating wire.

In addition the electronic control means is able to measure the presence or absence of localized over-heating or hot-spots The electronic control means further has the ability to impose different operating time limits dependent on the power level in use.

When supplied from an ac power source or dc derived from an ac power source the electronic control means is arranged to switch power on or off at the zero-crossing point of the ac power source so as to minimize the production of radiated and conducted electrical interference.

The electronic control means incorporates one or more electronic circuits functioning as inhibit lines so designed that, on receipt of a signal from an externally connected equipment, they will cause the electronic control means to prevent power being switched to the garment heating circuit. Such an externally connected equipment might be a lithium-ion battery pack with a means of signalling a fault condition In another situation the electronic control means would issue an inhibit signal to an externally connected equipment such as a battery charger to prevent it from operating except during so-called idle cycles of the heating circuit An embodiment of this invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic of a garment heating control circuit; Figure 2 is a schematic illustration of the time division power control; Figure 3 is an illustration of the ripple dc waveform when the dc supply is obtained from an ac source and is under load, Figure 4 is a schematic of a composite heating cable construction; and Figure 5 is a flow chart of the program sequence used to manage the time limits and power levels.

Refernrig to figure 1, the circuit generally comprises a control unit 1, to whLCh is connected a resistive temperature sensing means 2, a resistive hot-spot sensing means 3, a four position power level selector switch 4 providing settings of 75%, 50% 25% and 0% power, a boost button 5, timing and power control software 6, a power input 7, an inhibit circuit 8, an output control FET 9, a garment heating circuit 10, a timing oscillator 11 an AC detector 12 and extemaly connected equipment 13 (not shown).

When the garment heater is operating, the power output control FET 9 will switch the power input 7 to the garment heating circuit 10 for one, two, three or four 2.5 second heating periods, timed off the timing oscillator 11, at the end of the four periods the control unit I will interrogate the resistive temperature sensing means 2 for 10 milliseconds and the resistive hot-spot sensing means 3 for a further 10 milliseconds If either resistance measurement exceeds its fixed pre-set value the control unit 1 will re-set the power control software 6 according to the flow chart of figure 5 and set the following 10 second duty percentage of the output control FET 9 to 0%.

If the resistive temperature sensing means 2 and the resistive hot-spot sensing means 3 are within their fixed pre-set limits then the control unit 1 will pass the prevailing duty percentage setting to the output control FET 9 which will conned the power input 7 to the garment heating circuit 10 for the appropriate number of heating periods. The control cycle then repeats.

Figure 2 illustrates how the four 2 5 second heating periods are timed off the built-in 100Hz timing oscillator 11.

Figure 3 illustrates the waveform of the ripple dc that is used by the ac detector circuit 12 to synchronize the (otherwise free-running) 100Hz oscillator 11 to ensure that switching of the output control FET 9 coincides with the zero-crossing of the supply mains when the power input 7 is derived from the ac mains The inhibit circuit 8 is connected to the control unit I and the FET output switch 9 and also to external equipment and operates to inhibit the FET output 9 if the connected equipment 13 indicates a fault Furthermore the inhibit circuit 8 will operate to inhibit the operation of externally connected equipment 13 if an inhibit request signal is issued by the control unit 1 as might be the case if all available power was required for the garment heater 10.

Figure 5 illustrates how the power control software 6 is used to cause the 100% power timing and the 75% power timing to operate in a consecutive manner. It can be seen from the flow chart that the 100% boost timing is triggered and or re-triggered by an interrupt generated by the boost button 5 and further that this timer is cancelled if the resistive temperature sensing means 2 or the resistive hot-spot sensing means 3 should exceed their pre-defined resistance limits.

Likewise if 75% power has been selected on the power level selector switch 4 then this power level will survive for 60 minutes or until cancelled if the resistive temperature sensing means 2 or the resistive hot-spot sensing means 3 should exceed their pre-defined resistance limits At such time as both the 100% and the 75% power times expire, the power levels will default to 50% or to 25% if 25% was the level selected on the 4-position power level selector switch 4.

Claims

Claims 1. A garment heating controller provided with an input for a

battery pack, an input for an external power supply and an output connection to an electrically heatable garment such that when connected to an external power supply the controller will use that power source for garment heating and also to charge the battery pack.
2. A controller according to claim 1 in which the controller regulates the power output to the garment by a time-division process.
3. A controller according to claims 1 and 2 in which the controller charges the battery pack during intervals when the garment is not being heated.
4. A controller according to claims 1 and 2 in which detection means is provided for garment over temperature.
5. A controller according to claims 1 and 2 in which detection means is provided for localized over temperature or hot spots'.
6. A controller according to claims 1 and 2 in which high output power settings are limited in duration after which they will be automatically re-set to a lower level.
7. A controller according to claims 1, 2, 5 and 6 in which high output power settings are cancelled or reduced if a garment over temperature is detected.
8. A controller according to claims 1, 2, 5 and 6 in which high output power settings are cancelled or reduced if a garment hot-spot is detected.
9. A controller according to claims 1, 2 and 3 in which battery charging is discontinued if a battery fault signal is detected.
10. A controller according to claims 1, 2 and 3 in which battery charging is discontinued if a battery hazard signal is detected.