JPS58119017A - Switching voltage regulator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to switching voltage regulators, ie direct current regulators whose output voltage is determined by the switching ratio of series-connected switches. Many types of regulators of this type are known and usually use semiconductor switching elements. The circuit can be more or less complex depending on the equipment used to control the switching elements to maintain the output voltage at the required value as the current supplied to the load changes. Switching voltage regulators require some form of smoothing to reduce ripple to an acceptable level, and one commonly used configuration uses a series-connected inductance coil between the switch side of the inductance coil and ground. A diode is connected to the inductance coil, and a capacitor is connected between the load side of the inductance coil and ground.

In operation, this device allows energy to be stored in the inductance coil while the series switch is closed, during which time the diode is non-conducting. When the switch opens, the load current is maintained through the conducting diode, allowing the energy stored in the inductance coil to pass to the load.

In order to reduce switching losses, the switch must operate quickly. but.

It has often been found that when the switch is closed, the diode is still conducting due to hole storage effects in the diode. For this purpose, short-duration, high-amplitude current pulses flow through the diode until the diode ceases to be conductive. Such current pulses are wasteful and can also cause significant radio frequency disturbances.

It is an object of the present invention to provide a switching voltage regulator with series connected switches which eliminates the above-mentioned problems.

According to the present invention, there is provided a switching voltage regulator comprising a series connected switch and an output voltage smoothing circuit connected between the series switch and a pair of output terminals, the smoothing circuit being connected between the switch and the output terminal. first and second inductance coils connected in series between one of the terminals, and a first diode connected between the junction of the two inductance coils and the other of the output terminals; , a capacitor connected between the pair of output terminals, and a second diode that consumes all the energy stored in the inductance coil closest to the switch when the switch opens.

The invention will now be described with reference to the accompanying drawings.

In all drawings, control circuits for switching elements have been omitted for clarity. A number of control devices are known for use with series connected switches in voltage regulators of this type.

Referring now to FIG. 1, one well-known type of switching voltage regulator is shown in which an input DC voltage is applied to a pair of input terminals 10. The ground side of the input is.

It is connected to one of the pair of output terminals 11. The other input terminal is connected to the collector of the switching transistor TR, and the emitter of the transistor TR is connected to the other output terminal via an inductance coil L1. A diode D1 is connected between the junction of the inductance coil L1 and the transistor TR and the ground line, and a capacitor C is connected between the ground line and the a-side (7) end of the inductance coil. A load is shown connected to the output terminals.

In operation, transistor TR opens and closes at a rate determined by the control circuit. When the transistor turns on, current flows to the load, charging the capacitor and at the same time storing energy in the inductance coil L1. Diode D1 is reverse biased and therefore non-conducting. When the transistor turns off, the inductance coil L1 dissipates energy through the diode to the load,
Maintain load current. Ideally, when the transistor becomes conductive again, diode D1 should immediately become non-conductive to avoid the short duration, high amplitude current pulses that would cause the previously mentioned problems. The diode must also carry the full load current when the transistor burns out.

Due to hole storage effects, it is the combination of high current capacity and high switching speed that is difficult to achieve, especially at load current values on the order of 5 amps or higher.

To achieve high switching speed at small currents.

It is also easy to achieve high current capacity at low switching speeds.

Figure 2 shows one way in which that problem can be overcome. The illustrated circuit has all the features of FIG. 1, but with a second inductance coil L2 connected in series with the first inductance coil and between it and transistor TR. .

A diode D2 is connected across the inductance coil L2 in such a way that when the transistor TR is turned off, the energy stored in the inductance coil can be dissipated. The inductance of inductance coil L2 is usually smaller than the inductance of Ll.

When transistor TR conducts, current flows through inductance coil L2 and increases to the required load value, while
Diode D1, which was previously conducting, recovers and stops conducting. Next, 5 currents are applied to the inductance coil as before.
Flows all the way through to the load. When the transistor is turned off, the load current flowing through the inductance 2 before is
It can be attenuated through diode D2 in a controlled manner. At the same time, diode D1 begins to conduct as described above to maintain the load current.

Diode D1 does not need to switch between its conducting and non-conducting states particularly rapidly, but it does need to withstand the load current. Diode Sum2, on the other hand, must change state quickly but conducts a relatively small current. Diode D2 is what is referred to as a "fast" diode in the manufacturer's literature. This generally means that one state (
That means that only 10% of the time spent in conduction or non-conduction is spent changing from one state to another. Ideally, that time should be 2-3%
It should be. The two types of diodes defined above are readily available.

FIG. 5 shows an alternative embodiment, showing a diode D2 connected between the switch end of the inductance coil L2 and the ground wire. The effect of this connection is similar to that already described. Other arrangements of diode D2 are also possible.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a well-known switching voltage regulator, FIG. 2 is a circuit diagram of a first embodiment of the present invention, and FIG. 3 is a circuit diagram of another embodiment of the present invention. TR--Switching transistor, Ll, L2--
Inductance coil, Dl, D2-1 diode,
C--conde/su.

Claims (1)

[Claims] L series connection switch and the series connection switch and 1
an output voltage smoothing circuit connected between the pair of output terminals, the smoothing circuit comprising first and second inductance coils connected in series between the switch and one of the output terminals; , a first diode connected between the junction of the two inductance coils and the other of the output terminals, dissipating all the energy stored in the inductance coil closest to the switch when the switch opens. and a second diode connected in such a manner that the switching voltage regulator comprises a second diode. 2. The voltage regulator according to claim 1, wherein the second diode is connected in parallel to the second inductance coil. 5. The second diode is connected to the switch and the second diode.
2. The voltage regulator according to claim 1, wherein the voltage regulator is connected between the junction point with the inductance coil and the other output terminal. 3. The voltage regulator according to claim 1, 2 or 5, wherein the second diode is a high speed diode.