Electrical transmission or interconnection systems – Plural load circuit systems – Control of current or power
Patent
1997-04-25
1998-10-13
Gaffin, Jeffrey A.
Electrical transmission or interconnection systems
Plural load circuit systems
Control of current or power
327175, 327451, 318809, G05F 100
Patent
active
058216359
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a method for controlling the power supplied by an electrical circuit, in particular, a sinusoidal source of the generic type which generates a controllable output power from a DC voltage supply, with the current flowing essentially sinusoidally.
It is generally known to operate a high-frequency-operated sine power converter, in particular, in the form of a sinusoidal source, according to so-called phase-angle control, which power converter supplies a controllable power from a DC voltage supply. Disadvantageous in this control are the associated switch-off losses because, during switch-off in the reduced power mode, switching does not take place in the current zero and because this switch-off process takes place within each half period.
Furthermore, it is known to implement a power control according to the so-called pulse package control or burst control. This implies that a package switched through at a specific switching frequency respectively comprises several sinusoidal pulses of a higher frequency. Since the current is only switched off when the current goes through zero to avoid switch-off losses, the disadvantage of this control is that a precise power control cannot be accomplished with this method because, after all, the output power is only possible in jumps of one pulse each time, i. e., the power can only be quantized in rough steps. This applies at least in those instances where the burst repetition frequency must not be allowed to become too low.
SUMMARY AND ADVANTAGES OF THE INVENTION
In contrast, the method according to the invention for controlling the power supplied by an electrical circuit, in particular, a sinusoidal source, having the characteristics according to the present invention offers the advantage of a finely quantizable power control in the entire adjustment range with a minimum switch-off power loss since it occurs only once within the burst repetition frequency.
In principle, this is accomplished according to the invention in that the supplied power is determined, on the one hand, by the integer number of the sinusoidal pulses comprised in a burst which is fully switched through to the output of the circuit and, on the other hand, by the length of the last phase angle-controlled pulse within each burst which is switched through to the output of the circuit, with the frequency of the pulse sequence within the bursts being selected to be constant and considerably higher than the burst repetition frequency. In other words, a burst is first fully switched through in the invention for a period of time and then the last half period or complete period of a pulse within the burst with phase angle-controlled and switched through phase is controlled.
Advantageous modifications and improvements of the method according to the invention discussed above are possible by way of the measures disclosed and discussed an advantageous circuit arrangement for gaining the actuation signal according to the invention is likewise disclosed.
According to a particularly advantageous feature of the invention, the bursts are switched through in such a manner that the switching elements switching the current are switched in the zero passage of the sinusoidal pulses to avoid switch-off losses, with the exception of the period portion that is phase angle-controlled.
An advantageous embodiment of the invention provides that the actuation signals for the switching elements switching the current are produced in a similar manner as in the phase-angle control, with a pulse width gain being carried out by comparator comparison of the regulated quantity with a sawtooth voltage and a sawtooth generator being operated with an n-fold lower frequency than the frequency of the sinusoidal pulses in the bursts. In an advisable modification of the invention, the n-fold lower frequency of the sawtooth generator corresponds to the pulse frequency divided by 8 up to 256.
In a further configuration of the invention, the present method according to the invention can be used in a particula
REFERENCES:
patent: 3633094 (1972-01-01), Clements
patent: 3927349 (1975-12-01), Suhren et al.
patent: 4010412 (1977-03-01), Forman
patent: 4358716 (1982-11-01), Cordes et al.
patent: 4358730 (1982-11-01), Beifus
Gaffin Jeffrey A.
Paladini Albert W.
Robert & Bosch GmbH
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