Electrical transmission or interconnection systems – Switching systems – Condition responsive
Reexamination Certificate
2002-01-02
2004-03-23
Toatley, Jr., Gregory J. (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
Condition responsive
C307S131000, C315S2090SC, C363S132000
Reexamination Certificate
active
06710474
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a circuit arrangement for switching on a partial circuit arrangement, the circuit arrangement having a first switching element with a control electrode and a reference electrode, the reference electrode being connected to a reference potential. It further comprises a partial circuit arrangement, the first switching element having to be activated when the circuit arrangement is being switched on, and at least one second switching element, which is required for the operation of the circuit arrangement after the partial circuit arrangement has been switched on but which is not assigned any activity when the partial circuit arrangement is being switched on, the at least one second switching element having a control electrode and a reference electrode, which is connected to the reference potential. It further comprises an activation circuit for the first switching element, the activation circuit comprising a storage capacitor which, to activate the first switching element, is connected via a DIAC to the control electrode of the first switching element, and a first diode which is arranged between the reference potential and the storage capacitor in such a way that it is made possible for a current to flow to activate the first switching element.
PRIOR ART
In order to clarify the problem on which the invention is based, such a circuit arrangement, disclosed by the prior art, is illustrated in FIG.
1
. It is used by the applicant of the present invention as a starting circuit for lamp operating devices which have a half-bridge arrangement. In particular as a starting circuit for a freely oscillating converter, one of the two half-bridge transistors initially has to be switched on. In the case of a freely oscillating converter, which is to be assumed here by way of example in order to illustrate the invention, the two half-bridge transistors are driven via their control electrode, in actual operation, only after a separate starting operation. In
FIG. 1
, the transistor T
1
represents one of the two half-bridge transistors. The transistor T
2
is a second switching element, which is required for the operation of the circuit arrangement after it has been switched on, but which is assigned no activity while the partial circuit arrangement is being switched on, here the lower half of the freely oscillating converter for operating the lamp. The bases of the transistors T
1
and T
2
are connected to each other via a resistor R
1
. In order to switch on the transistor T
1
, that is to say to start an oscillation, a pulse-like switching-on signal is necessary. In the present case, this is achieved by a capacitor C
1
, which on one side is connected via at least one resistor R to the positive signal +(NGR) from a mains rectifier and on the other side is connected via a resistor R
2
to ground, being charged up. This capacitor voltage is present on one side of a DIAC, whose other terminal is connected to the control electrode of transistor T
1
. Then, as soon as the voltage on that terminal of the DIAC which is connected to the capacitor C
1
exceeds a certain limiting value, said DIAC breaks down and permits a sudden current surge to the control electrode of the transistor T
1
. By this means, the transistor T
1
is switched on, and therefore the freely oscillating converter is started. The firing current for starting the freely oscillating converter initially flows in the circuit comprising DIAC, transistor T
1
, reference potential, resistor R
2
and capacitor C
1
. However, as the firing current grows, the voltage drop across the resistor R
2
at some time becomes so high that the firing current experiences a lower resistance if it flows via the diode D
1
. The current flow then changes from the resistor R
2
to the diode D
1
.
The task of the transistor T
2
begins after the firing of the transistor T
1
. In the present example, it consists in blocking the DIAC during normal operation, since repeated firing of the DIAC would disrupt the continuous operation of the freely oscillating converter. The latter functions in such a way that the base signal of transistor T
1
is also applied via R
1
to the base terminal of the transistor T
2
. The collector of transistor T
2
is connected to the potential between storage capacitor C
1
and DIAC. During normal operation, the transistor T
1
is driven via the line BT
1
. This signal is also applied to the base of the transistor T
2
via R
1
.
The storage capacitor C
1
is therefore discharged regularly via T
2
, and no disruption to the operation of transistor T
1
occurs.
The disadvantage of this known circuit arrangement is that precisely at the time at which the full energy stored in the storage capacitor C
1
leads to the breakdown of the DIAC, some of the energy is led past the envisaged location—namely the control electrode of the transistor T
1
—via R
1
to the base of transistor T
2
. This leads to the transistor T
2
turning on and, via its operating electrode, dissipating some of the energy stored in the storage capacitor C
1
to the reference potential. As a consequence, it can be established that not all of the energy stored in C
1
is available for firing the transistor T
1
, but is dissipated via a switching element which is not assigned any activity during the actual firing operation. As explained above, the purpose of transistor T
2
is based on normal operation, that is to say after the firing of transistor T
1
.
The negative result of this is that the storage capacitor C
1
has to be dimensioned to be considerably larger, which in turn results in the entire circuit arrangement being slowed down.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to develop a generic circuit arrangement in such a way that the disadvantages of the prior art are overcome, in particular the provision of a faster circuit arrangement is made possible.
According to the invention, this object is achieved in that, in series with the first diode, on the side of the first diode facing away from the reference potential, a second diode is arranged in the same orientation as the first diode, the junction between the first and the second diode being connected to the control electrode of the at least one second switching element and, in series in a connection between the control electrode of the second switching element and the reference potential, in addition to the second diode, at least one third diode is connected in the same orientation as the second diode.
The invention is based on the fundamental idea of switching off at least one second switching element actively via the DIAC at the same time as the first switching element is initially switched on, the switching-off action also being effected by the DIAC. In particular, in order to switch off the at least one second switching element, use is made of the current which flows through the storage capacitor C
1
belonging to the DIAC when the latter is fired. Therefore, the at least one second switching element is switched off by exactly the same current by which the first switching element T
1
is switched on. This implementation is optimal with regard to the cost question, since no further controllers, timing elements etc. are needed. It is in particular independent of component parameters and can therefore preferably also be used in mass production. Moreover, it is naturally real-time capable. With minimum expenditure, the invention provides an extremely robust and exactly functioning solution.
A preferred embodiment of the invention is distinguished by the fact that the side of the series circuit comprising the second and third diode and facing away from the control electrode of the second switching element-is connected firstly to the storage capacitor and secondly via a resistor to the reference potential. This measure means that the firing operation is boosted since, when the voltage drop across the resistor becomes greater than the sum of the diode forward voltages, the diodes take over the firing current.
A further preferre
Patent-Treuhand-Gesellschaft fur elektrische Gluhlampen mbH
Rios Roberto J.
Toatley , Jr. Gregory J.
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