JPH033463B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a power control circuit for a switch type power amplifier in which the voltage applied to a switch or the current waveform flowing through the switch becomes an arc of resonance. [Technical background of the invention and its problems] Conventional switch type power amplifiers directly switch the input power supply voltage as seen in the chopper type.
There are two types of circuits: those that change the width of the switch to change the amount of power sent to the load, and those that do not directly switch the input power supply voltage by adding an external circuit as seen in class D power amplifiers. is made to form a resonant arc, and the amount of power to the load is changed using another converter on the input side. In the former chopper type switch loss, the transition loss of the switch increases as the switch frequency increases, and its limit is determined by the switch speed of the switch element. On the other hand, regarding the switch loss of the latter class D power amplifier, even if the switch frequency increases, the transition loss of the switch does not increase much, allowing highly efficient switching. On the other hand, since the resonance conditions are determined by the external circuit, the switch width,
Even if the switch cycle is changed, the power to the load does not change smoothly. Therefore, in order to adjust the power to the load of a switch circuit such as this class D power amplifier, it is necessary to install another variable voltage device before and after the switch circuit. [Object of the Invention] This invention was made in view of the above points, and is a switch-type power amplifier that utilizes a resonant waveform. The purpose is to provide a control circuit. [Summary of the Invention] The present invention provides a switch type power amplifier circuit in which a load circuit is connected to a voltage resonant single-ended switch circuit via a series resonant circuit, and a switch that directly closes the series resonant circuit without going through the load circuit. By providing this between the input terminals of the load circuit, it is possible to smoothly control the power to the load circuit while maintaining voltage resonance. [Examples of the Invention] The present invention will be described in detail below with reference to Examples.
FIG. 1 is a circuit diagram showing an embodiment of the present invention. 1 is an input DC power supply, and a switch element 3 such as a transistor or thyristor (including GTO) is connected to both ends of the input DC power supply via a current smoothing chain 2.
Connect. A damper diode 5 and a resonance capacitor 5 are connected in parallel to this switch element 3.
Further, a switch 8 is connected to this switch element 3 via a power transfer capacitor 6 and an inductance 7. A load circuit 9 is connected in parallel to this switch 8. This load circuit includes cases in which it simply includes only a resistor, and cases in which it includes a voltage smoothing capacitor, load resistance, etc. via a bridge rectifier. Here, some assumptions will be made to explain the operation of FIG. It is assumed that the switch element 3 opens and closes with a constant pulse width and period, and the circuit shown in FIG. 1 has reached a steady state. In other words, a constant current is applied to the chain 2.
It is assumed that Iin flows, the terminal voltage of the resonant capacitor 6 at the start of the cycle is a certain constant value _Vc1 , and furthermore, a certain constant value Io of current flows in the power transmission inductance 7. switch element 3,
8 and diode 5 are each ideal switches, and the conduction resistance is zero ohm when conductive, and infinite when disconnected. First, the operation of the present invention will be explained from the period when the switch element 3 is in the "conducting" state with the simple switch element 8 in an open state without a collar. In FIG. 1, the load circuit 9 is specifically represented by a resistor 11.
When the switch element 3 is "conductive", the equivalent circuit becomes as shown in FIG. And literature no.
Sokal“clossE−Arka cloth of High−
Efficiency Twad Sigle−Euded Switching
Power Awplifier”IEEE Vol SC−10No.3
According to June 1975, the value R of the load resistance 11 is determined in advance by the operating frequency of the switch and the inductance 7.
Using the value L, select approximately 2π·L/R _L > 6 (1). Current flows into the chain 2 from the power source 1 to replenish magnetic energy. On the other hand, in a closed circuit including the load 11 as a part, the magnetic energy stored in the inductance 7 is discharged by flowing in the direction shown in the figure as a current Lout. Meanwhile, Lout is the load R _L
While consuming energy, energy is stored in the capacitor 6 in the form of voltage. This state continues until half of the operating cycle. That is, after half of the operating cycle has elapsed, the switch element 3 is forcibly turned off. At that time, the power supply 1 and the switch coil 2 become a current source that supplies a constant current Lout, and the capacitor 4 connected to both ends of the switch element 3 appears, so the equivalent circuit during the "off" period of the switch element 3 is shown in Figure 3. become that way. The capacitor 4 receives an inflow from a current source 12 and an inflow of energy stored in the resonant circuit 10 . Since the capacitors 4 and 6, the coil 7, and the load 11 form a resonant circuit, the terminal voltage of the capacitor 4 rises in a sinusoidal arc, drops again, and eventually reaches zero, becoming even more negative potential. . At that time, a diode 5 is connected across the capacitor 4.
is in the direction shown in FIG. 1, the equivalent circuit returns to FIG. 2 again. That is, the terminal voltage of the capacitor 4 is maintained at zero until the end of the operating cycle.
Thereafter, when the next cycle begins, current begins to flow with the terminal voltage of the switch element 3 being zero, so that the switch loss when the switch element 3 is turned on is theoretically eliminated. The above operation waveforms are summarized as shown in FIG. In other words, Fig. 4a shows the distribution of "conduction" and "disconnection" of the switch element 3, b shows the current waveform of the switch element 3, c shows the terminal voltage waveform of the switch element 3, and d flows to the load R _L. The current waveforms are shown respectively. However, the direction of the solid line of the load current Lout in FIG. 3 corresponds to the negative part of d in FIG. 4. Here, even if the load R _L changes, if it is within the range that satisfies equation (1), the waveforms of each part in Figure 4 will not change significantly, but the load R _L will become lighter and go out of the range of equation (1). When the load current Lout attenuates rapidly as shown by the dotted line in Fig. 4d, and the switch element 3 becomes disconnected, there is little energy stored in the resonant circuit 10 , so the voltage across the capacitor 4 increases as shown in Fig. 4. As shown by the dotted line c, the potential does not become zero even after one cycle ends. In other words, when the next cycle starts with the voltage Vres remaining in the capacitor 4, the electrical energy of 1/2 CV ² res is transferred to the switch element 3.
It flows in an instant. This results in a large spike-like current as shown by the dotted line in FIG. 4b. As a result, the switch element 3 increases its allowable current value and is destroyed. Furthermore, if destruction does not occur, the loss in the switch element increases significantly. From the above facts, in order to change the load to a lighter direction, the energy needed to make the terminal voltage Vc of the capacitor 4 zero is required to reduce the load to the resonant circuit 1 during the "conduction" period of the switch element.
This means that it must be stored at 0. In other words, the terminal voltage is applied to the resonant circuit 10 .
The limit to which the load R _L can be lightened is that the energy that can reduce Vc to zero is stored. The variable range of the load is narrow, about 1/5 times the rated load R _L , and the waveforms at various parts become as shown by the dotted lines in Figure 4. The cause of this narrowing of the variable range of the load is that sufficient energy is not stored in the resonant circuit 10 to reduce the terminal voltage of the capacitor 4 to zero, or that sufficient energy is not stored in the resonant circuit 10 to reduce the terminal voltage Vc to zero. Load despite stored energy
Resonant circuit 1 due to large energy consumption in R _L
There are two cases where the stored energy of 0 is not transmitted to the capacitor 4. This latter state can be relieved according to the present invention. i.e. load R _L
If a switch is provided at both ends of , the negative current Lout is closed at an appropriate time Ta, and the energy of the resonant circuit 10 is transmitted directly to the capacitor 4 without passing through the load R _L , the terminal voltage Vc becomes zero. The ON-OFF chart of switch 8 is once in Ton and once in Ton in one period T, as shown in Figure 5e.
Close each once between ~T. switch 8
In Fig. 4, the period Ta when Ton is open is indicated by the dotted line, and the period Ta is closed is (Ton-Ta)
is the solid line part in Figure 4, so those switches 8
When rewritten according to the ON-OFF chart, the waveforms of each part become as shown in Figures b to d. That is, the waveform flowing through the switch element 3 is shown in figure b, the waveform applied to the switch element 3 is shown in figure c, and the waveform of the current flowing in the resonant circuit 10 is shown in figure d. After Ta has elapsed, the switch 8 is switched and a large resonant current of the resonant circuit 10 flows into the capacitor 4, so the amplitude of the terminal voltage Vc oscillates greatly as shown in Figure 5b and becomes zero at the end of one cycle. Become. The period during which switch 8 is closed (Ton-Ta),
(T-Ta), since no power is transmitted to the load 11, the average power of the load 11 decreases. Furthermore, by changing the width of Ta, the average power consumed by the load 11 can be changed arbitrarily. The switch 8 can be easily realized by connecting thyristors in antiparallel as shown in FIG. 6, or by directly switching a transistor or a magnetic amplifier according to the switch chart shown in FIG. 5e. [Effects of the Invention] As is clear from the above explanation, even though the main switch 3 operates with low switch loss, the power consumption of the load 11 can be reduced by changing the conduction timing of the auxiliary switch 8. Can be changed smoothly. Furthermore, even if the contents of the load circuit 9 shown in FIG. 7 are used, the basic operation will not be impaired. Furthermore, the terminal voltage of the load resistor 11 does not become zero even when the auxiliary switch 8 is closed.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIGS. 2 and 3 are equivalent circuit diagrams for explaining the operation, and FIGS. 4 and 5 are operational waveform diagrams.
FIG. 6 is a diagram showing a method of configuring the switch, and FIG. 7 is a diagram showing an example of a load circuit. DESCRIPTION OF SYMBOLS 1... Power supply, 2... Chain yoke, 3, 8... Switch element, 4, 6, 13,... Capacitor, 7... Inductance, 9... Load circuit, 10 ... Resonant circuit, 11...
Load resistance, 12... Current source, 14... Bridge diode.

Claims (1)

[Claims] 1. A switch element that opens and closes under certain conditions is connected to a DC power supply via a chain yoke, a capacitor and a damper diode are connected in parallel to this switch element, and a coil is connected to this switch element via another capacitor. 1. A power control circuit characterized in that a load circuit is connected through the circuit, and another switch element is connected in parallel to the load circuit. 2. A patent claim characterized in that the switch element connected in parallel to the load circuit operates at least once when the switch element connected via the chain yoke opens and closes once when it is "conducted" and once when it is "disconnected". The power control circuit according to scope 1.