Electricity: battery or capacitor charging or discharging – Capacitor charging or discharging
Reexamination Certificate
2000-05-03
2002-04-02
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Capacitor charging or discharging
C363S027000, C323S222000
Reexamination Certificate
active
06366058
ABSTRACT:
TECHNICAL FIELD
The invention relates to the field of mains power supply units for supplying electronic assemblies, in particular the invention relates to a capacitor power supply unit comprising a charging capacitor for charging up a further capacitor (storage capacitor) for the purpose of operating an electric power consumer, a rectifier which is disposed between the charging capacitor and the storage capacitor, and a switching means which by applying circuit engineering technology is disposed between the charging capacitor and the storage capacitor and has a control input which has applied to it the outputs of a member which determines the point in time, at which switching is to occur, which member is influenced by a small reference voltage in comparison with the mains alternating voltage, for the purpose of determining the point in time for switching over the switching means from a switch position which charges the storage capacitor, to a switch position which interrupts the charging procedure, in dependence upon the voltage applied on the output side to the charging capacitor, and a charging state-determining member for the purpose of determining the charging state of the storage capacitor. The invention also relates to a method of operating a capacitor power supply unit.
BACKGROUND ART
Capacitor power supply units are widely used for the purpose of generating auxiliary voltage supplies which are not separated from the mains supply. These types of auxiliary voltages usually serve to supply electronic assemblies, for example, to supply the electronics used for controlling the rotational speed in boring machines. The principle of a capacitor power supply unit is based upon the cyclic recharging of the charging capacitor which is used as a charging pump for the storage capacitor and charges same during each mains supply cycle. A breakdown diode is used for the purpose of stabilizing this type of capacitor power supply unit. In the context of these statements, the term breakdown diode relates to all diodes which are reverse biassed and are also known as a Zener diode or avalanche diode.
By reason of their straightforward and cost-effective design, capacitor power supply units are widely used for small output powers with a virtually constant load. However, a problem arises in the use of this type of capacitor power supply unit, if the load is relatively large and is subjected to severe fluctuations in dependence upon the operating point. This change in load can lead to an extreme loading of the breakdown diode, which ultimately can cause the breakdown diode, the storage capacitor and thus the entire power supply unit to be destroyed. This effect is particularly damaging if this type of capacitor power supply unit is encapsulated, for example, in a housing, so that the heat produced in the breakdown diode cannot be dissipated or is only dissipated inadequately, so that the thermal loading can cause the breakdown diode to become unsoldered. The capacitor power supply unit is then no longer functional.
In order to lessen these disadvantages, capacitor power supply units have been developed, as described, for example, in DE 38 01 399 A1, wherein the switching procedure for switching over the switching means from a switch position which charges the storage capacitor, to a switch position which interrupts the charging procedure, is performed at a point in time, at which the switching means is supplied with only a small amount of current. As a consequence, no steep switching transients should be produced in the case of this switching procedure. This is achieved by virtue of the fact that the switching means has a control device connected upstream, which serves to move the switching means to its switch position which interrupts the charging procedure if the voltage applied on the output-side to the charging capacitor is small corresponding the cycle of the mains voltage. At such a point in time when switching occurs, the switching means is only supplied with a small amount of current. This capacitor power supply unit is then switched to the charging operation, if the output voltage of the storage capacitor is less than a predetermined desired value. This switching procedure is exclusively dependent* upon the charging state of the storage capacitor and can therefore be performed at any time with regard to the cycle of the mains voltage. Even if, in the most favourable case, the switch can only be subjected to low voltage at this point in time when switching occurs, the switching means is still supplied with a relatively high level of current, so that the occurrence of current peaks cannot be excluded.
When the electric power consumer is operated in a continuous manner, the required current is drawn off continuously from the storage capacitor. By virtue of the procedure of controlling the switching means, as described in this document, the switching means is continuously switched in a reciprocating manner between the two operating positions corresponding to the frequency of the mains supply cycle or the rectified voltage half-waves. The loss of power which occurs in particular when switching the switching means to the charging operation of the storage capacitor means that there is the risk that the electronic components can be heated up to the point of being destroyed.
SUMMARY OF THE INVENTION
On the basis of the discussed prior art, the object of the invention is therefore to provide a capacitor power supply unit which is also suitable for permanently operating the electric power consumer connected thereto.
Furthermore, the object of the invention is to provide a corresponding method of operating a capacitor power supply unit.
In accordance with the invention, the object relating to the device is achieved by virtue of the fact that the switching time-determining member and the charging state-determining member, when connected together by wires so as to represent a logical AND-function, influence the control input of the switching means, so that both switching procedures of the switching means—switching the capacitor power supply unit to the charging operation and switching same for the purpose of interrupting the charging operation—are performed at a point in time, at which the voltage applied on the output-side to the charging capacitor is less than or equal to the reference voltage.
In accordance with the invention, the object relating to the method is achieved by virtue of the fact that on the basis of a charging operation for charging a storage capacitor, the method of operating a capacitor power supply unit with a switching means comprises the steps of:
comparing the phase-sensitive voltage, which is applied on the output-side to a charging capacitor, to a reference voltage,
providing a control signal with a switching time-determining member for the purpose of controlling the switching means, if the applied voltage is less than or equal to the reference voltage,
determining the charging state of the storage capacitor by means of a charging state-determining member,
providing a control signal for the purpose of controlling the switching means, if the charging state of the storage capacitor is greater than a predetermined limit value, which steps relating to the charging state can be performed simultaneously with the steps relating to the switching time,
switching the switching means for the purpose of interrupting the charging procedure of the storage capacitor, if both the charging state of the storage capacitor exceeds a predetermined limit value and also if the voltage, which is applied on the output-side to the charging capacitor, is less than or equal to the reference voltage,
switching the switching means back to the charging operation, if both the charging state of the storage capacitor is less than or equal to a predetermined limit value and also if the voltage, which is applied on the output-side to the charging capacitor, is less than or equal to the reference voltage.
In the case of the capacitor power supply unit in accordance with the invention, the switching time-det
Leopold Kostal GmbH & Co. KG
Tibbits Pia
Wong Peter S.
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