GB2303229A

GB2303229A - Constant power output circuit for an electric fence

Info

Publication number: GB2303229A
Application number: GB9506569A
Authority: GB
Inventors: Carlton Dudley Manning
Original assignee: EDDIE PALIN DISTRIBUTION LIMIT
Current assignee: EDDIE PALIN DISTRIBUTION LIMIT
Priority date: 1995-03-30
Filing date: 1995-03-30
Publication date: 1997-02-12
Anticipated expiration: 2015-03-30
Also published as: GB9506569D0; GB2303229B

Abstract

A battery-powered circuit for charging a capacitor 4 intended to deliver high-voltage pulses to a load, and in particular to an electric fence, is able to deliver its intended output with the battery voltage lying in the range of 3 - 15 V. Positioned between the terminals across which the battery is to be connected and the energy-storage capacitor, is a voltage-sensitive device 3 and at least one timer circuit 12 by which energy from the battery 2 is intended to be supplied to the capacitor 4 in pulses of battery current initiated at timed intervals. The duration of each battery pulse is dependent on the instantaneous voltage of the battery, and the voltage-sensitive circuit controls the length of the period over which the pulses supply energy to the capacitor, so that the period is a function of the instantaneous voltage of the capacitor. This extends the effective life of batteries used to charge electric fences, and enables farmers and other users to use partially-discharged batteries to keep the fence effective against straying cattle.

Description

Constant Power Output Circuit.

According to the present invention there is provided a circuit which is self sensing of voltage input and which will provide a constant power output irrespective of voltage input between 15 and 3 volts DC.

This circuit has been incorporated into an electric fence controller. Although incorporated into an electric fence controller there will be other applications where a constant power output, irrespective of voltage input is required.

A constant power circuit is provided for the use with an electric fence controller, which overcomes the problems of electric fence controllers known therefore whereby the stored energy level falls as battery input voltage decreases.

The pulse rate will also remain constant irrespective of the voltage input between 15 and 3 volts DC.

Electric fence controllers currently available suffer from a reduction in stored energy as input voltage falls. Stored energy capacitors are periodically discharged through the primary winding of an output pulse transformer. This is controlled by a timing circuit and the opening and closing of a power semicondutor switch, for example a thyristor or I.G.B.T. As battery voltage decreases a reduced level of power is stored in the storage capacitors resulting in a lower potential.

Referring to fig. 1, there is illustrated a circuit diagram of a high voltage pulse generator according to the invention for use with an electric fence. The generator is powered by a battery 2. The circuit comprises of a transformer 5 having a secondary coil 7 and a primary coil 6. The secondary coil is connected to a capacitive high tension neon pulse indication circuit 8 and to an electric fence contact 9 and to an earth contact 10. The high voltage pulses are delivered onto contacts 9 and 10 An energy storage capacitor 4 is connected across the primary coil 6 of the transformer 5 and the capacitor 4 is fed through a voltage converter 3 from the battery 2. A switch means provided by a current bidirectional switch 11 is connected between the primary capacitor 4 and the primary coil 6 to close the circuit formed by the capacitor 4 and the primary coil 6.The bidirectional switch 11 is closed at intervals of approximately one second by timing means 12, and opens naturally when the current through it tries to reverse at the end of one complete cycle of resonant frequency oscillation or is forced open by the timing means 12 after a predetermined period from the instance of closure.

The voltage converter 3 is self sensing of input voltage and energy storage capacitor voltage and operates efficiently to provide a constant level of energy storage in the capacitor 4 irrespective of the level of the input voltage, and to avoid unnecessary current consumption from the battery.

As input voltage decreases current consumption will automatically increase thus maintaining output power at a constant level.

The circuit (Fig2) is designed to provide a constant level of output irrespective of voltage input. It is self regulating as battery voltage drops current will increase. Should battery voltage increase current will decrease.

It is designed to operate as follows. IC1 (ICM7556) is set to operate between 15 - 3 volts DC. One half of the IC1 is used as part of a timing circuit which opens thyristor TH1 via a signal from Q1. The stored energy in capacitors C9 and C10 are discharged through the primary coil P1. The other half of the IC is used in the inverter/rectifier synchronous clock system. This has been designed to be self sensing and self regulating irrespective of input voltage between 15 - 3 volts DC.

Q4 will open and close at a frequency governed by IC1 via Pin 9. Current will be drawn through primary winding of T1 and C9/C10 will be charged via D12. A feed back circuit senses the voltage level of C9 and C10 and is designed to stop the inverter once the voltage in C9 and C10 reach the pre-determind level.

Claims

Claims

A A battery-powered circuit for charging a capacitor intended to deliver pulses of electrical energy to a load, in which circuit, positioned between the terminals across which the battery is to be connected and an energy-storage capacitor, is a voltagesensitive device including at least one timer circuit by which energy from the battery is intended to be supplied to the capacitor in pulses of battery current initiated at timed intervals, in which circuit the duration of each battery pulse is dependent on the instantaneous voltage of the battery, and in which the voltage-sensitive circuit controls the length of the period over which the pulses supply energy to the capacitor so that the period is a function of the instantaneous voltage of the capacitor.
2 A circuit as claimed in claim 1, in which there is a current limiter in the supply line from the battery terminals, the limiter being adapted to terminate each battery current supply pulse should the current in the pulse reach a chosen maximum value.
3 A circuit as claimed in claim 1 or 2, in which the capacitor is adapted to supply its energy to a load through an output pulse transformer.
4 A circuit as claimed in any preceding claim, in which the battery supplies energy to the storage capacitor through a flyback pulse transformer.
5 A circuit as claimed in claim 3 or 4, in which the primary winding of the flyback pulse transformer and/or of the output pulse transformer has a switch in series with it, and in which the or each switch is controlled by a timer.
6 A circuit as claimed in any preceding claim, in which the said device includes an integrated circuit chip, and in which the chip has two timer circuits on it.