Electricity: power supply or regulation systems – In shunt with source or load – Using a three or more terminal semiconductive device
Reexamination Certificate
2001-08-30
2002-11-19
Riley, Shawn (Department: 2838)
Electricity: power supply or regulation systems
In shunt with source or load
Using a three or more terminal semiconductive device
C323S287000
Reexamination Certificate
active
06483278
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method according to the preamble of the patent claim
1
and a power supply device for implementing said method according to the preamble of the patent claim
3
.
2. Description of the Related Art
A power supply device working according to this method is known from the U.S. Pat. No. 5,235,504. It comprises a large number of comparators, comparing, among other things, measuring values of the input current on the alternating current side of the power supply device with constant reference values and also comparing the output voltage of the rectifier with a constant reference value. Depending on the rectifier output voltage, the frequency of an oscillator is regulated, and in dependence of the output frequency of the oscillator and the output signals of the comparators, the switching frequency of the switch is regulated. The design of this power supply device is expensive.
From the European patent application 0 779 700 A2 a similar power supply device is known, which also has a large number of comparators, and in which the load current is measured and regulated in accordance with a predetermined, sine-like curve course. The activation of the switches happens in dependence of varying measuring magnitudes exceeding a limit value, including the load current. However, the switches are activated so that during the switching processes the current does not drop to zero. Through the inductor arranged on the direct current side, a relatively high average current flows, so that the inductor converts a relatively high power loss and has to be dimensioned accordingly large. Additionally, when switching on the switches (closing or putting into the conducting state, respectively), the diodes are conducting in the reverse direction for a short period due to the high average value of the current during the reverse recovery time of the diodes, which causes an even higher power loss. As the resulting, approximately needle-shaped current impulse flowing in the blocking direction has steep flanks, it additionally causes interfering signals in the radio frequency area.
An important objective of the known power supply devices described is a power factor correction with the purpose of obtaining a high efficiency. Thus, with the power supply device according to EP 0 779 700 A2, a relatively high power factor of 0.97 is obtained. It also conforms to the maximum limits of the harmonics and their amplitudes in the mains current prescribed in the international standard IEC 1000-3-2, 1995-03, however, a power supply device of this kind is expensive, and therefore is a cost-burden when used in devices, which are produced in series in large numbers, for example in speed regulated domestic compressors, even though they will do with only one inductor, in which the step-up converter and the step-down converter execute time sharing, as the regulation with only one inductor is too complicated, as opposed to mains devices, in which each converter has its own inductor.
SUMMARY OF THE INVENTION
The invention is based on the task of providing a method and a power supply device as mentioned in the introduction, whose implementation and the design, respectively, is more simple, though still meeting the standard 1000-3-2.
This solution is realised with only three comparators and without an oscillator for the regulation of the switching frequency of the switches. The limit values change in dependence of the output signal of the power supply device, for example, the speed of a motor functioning as the load, which speed is again a measure of the direct output voltage, whereas the switching times of the switches change in dependence of the load current, both the change of the limit values and that of the measured current signal causing a balancing of changes of the control parameter (D.C. voltage) by means of the control circuit of the controller.
The method can be realised in such a way that the first switch is on in the step-up conversion mode, and during this mode the second switch is turned off, when the rising measured current signal reaches the second limit value, and is turned on, when the decreasing measured current signal reaches the first limit value, and that in the step-down conversion mode the second switch is turned off, and during this mode the first switch is turned on, when the decreasing measured current signal reaches the first limit value and is turned off, when the rising measured current signal reaches the third limit value.
Preferably, it is ensured that the second and the third limit values are directly proportional to the output signal of the adder. This causes a quick balancing of regulation deviations or regulation differences, respectively.
The limit values can be picked up at a voltage divider, which is connected with the output of the adder via an amplifier. In a simple manner, the voltage divider causes the desired proportionality between the limit values and the output signal of the adder.
The switches can be immediately connected in series. This permits the use of an integrated circuit component, in which the switches are realised as semiconductor switches, and where separate cabling for the connection of an inductor arranged between the switches, as known per se, is avoided. In this connection, the integrated circuit component can be made in IGBT technique (IGBT=Insulated Gate Bipolar Transistor), and preferably also be designed as a traditional circuit component, which is used for the inverter of a motor controller operated by the D.C. voltage, that is, instead of discrete semi-conductor switches, traditional series-produced and accordingly non-expensive IGBTs can be used.
Due to the fact that the first limit value is close to zero, the load current drops in practically each switching period to zero or close to zero, so that during the switching periods the average direct current value is relatively low and correspondingly the inductor can be dimensioned smaller. At the same time, the peaks of the current in the blocking direction of the diodes, and thus the power loss of the inductor as well as the interfering signals in the radio frequency area are further reduced.
Preferably, it is further ensured that the control device comprises a switching frequency limiter, which delays the switching-on time of the switches, if a minimum time has not lapsed since the latest switching-on time, and hereby preventing dropping below a minimum switching period duration, or which advances the switching-on time of the switches, if a maximum time has lapsed since the latest switching-on time of the switches, hereby preventing an exceeding of a maximum switching period duration. In this way, the switching frequencies of the switches are limited upwards and downwards, and their switching period durations are limited downwards and upwards, respectively. Otherwise, a too high switching frequency would cause too high switching losses of the switches, as the switching losses are proportional to the switching frequency. On the other hand, a too low switching frequency, or a too long switching period duration, respectively, would cause a too high load on the inductor.
REFERENCES:
patent: 4943762 (1990-07-01), Campbell et al.
patent: 4947309 (1990-08-01), Jonsson
patent: 4964029 (1990-10-01), Severinsky et al.
patent: 5235504 (1993-08-01), Sood
patent: 36 08 082 (1987-09-01), None
patent: 0 779 700 (1997-06-01), None
Altera Law Group LLC
Danfoss Compressors GmbH
Riley Shawn
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