JPS63209463A - Switching type shunt regulator - Google Patents

Abstract

PURPOSE:To prevent rising of a voltage by combining an AC power having an inductance component with a DC power obtained by rectifying said AC power and by providing an overvoltage limiting circuit on the output side of a filter. CONSTITUTION:A three-phase AC of power supply 10 is rectified by a rectifier 12 and a DC output thereof is applied to and switched by a power FET 20 of switching element. An output of said FET 20 is smoothed by a filter 22 and supplied from output terminals 24, 26 to a load. Also, an error amplifier 16 compares an output voltage with a reference voltage 18 and outputs a PWM signal by a PWM circuit 30 to control the FET 20. Further, an overvoltage limiting circuit 32 removes a transient output voltage spike. In this manner, a calorific value can be controlled to a low one because an ON-resistance of said FET 20 is small, though heat is mainly generated by electric current flowing when the FET 20 is in ON-state.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a regulator applied to a power supply having an inductance component such as a small generator used in an aircraft engine, etc. This makes it possible to reduce loss and downsize.

(Prior art) Conventionally, a dropper (continuous control) type shunt regulator as shown in Fig. 2 has been commonly used as a regulator for regulating the output voltage of a power source for a small Ti-powered aircraft used in an aircraft engine, etc. Ta. This is a device in which the output (here, three-phase AC) of a power source 10 such as a small generator is rectified by a rectifier 12, the DC output is applied to a control transistor 14, and the output is taken out from both ends of the transistor 14. It is. The error amplifier 16 compares this output voltage with a reference voltage 18, and controls the transistor 14 so that the output voltage becomes a predetermined value.
control. That is, when the output voltage is higher than the reference voltage 18, the current flowing through the transistors 1 to 14 is increased to lower the output voltage. Furthermore, when the output voltage is lower than the reference voltage 18, the current flowing through the transistor 14 is reduced to increase the output voltage. This makes the output voltage constant.

[Problem that the invention seeks to solve]

In the dropper type shunt regulator shown in Fig. 2, in order to obtain a constant voltage output, the output current is adjusted according to fluctuations in the output current so that the sum of the output current supplied to the load and the current flowing through the transistor 14 remains constant. The current flowing through transistor 14 is controlled. Therefore, when the output current becomes zero, the entire load current flows through the transistor 14, causing the transistor 14 to generate a lot of heat. Therefore, the transistor 14 becomes large in order to withstand this heat generation, and the heat dissipation mechanism becomes large in order to dissipate the heat to the outside. For example, in the case of a 280 W load power supply, it is necessary to design the regulator with the expectation that heat of 280 W or more will soon be generated in consideration of the fact that the load will be zero. For this reason, it was unsuitable for use on aircraft, etc., which requires the device to be smaller and lighter.

This invention solves the above-mentioned problems in the conventional technology by reducing the amount of heat generated within the regulator.
By downsizing switching elements and heat dissipation mechanisms,
The present invention provides a regulator that enables miniaturization of the entire device.

[Means for solving problems]

The first invention of this application includes a switching element connected to a power supply having an inductance, a filter that smoothes the output voltage of this switching element, and an output of this filter that is supplied to a load connected in parallel with the switching element. and a switching control circuit that detects the voltage fluctuation between the output rods and controls the switching of the lyr switching element by changing the on/off time ratio so that the voltage becomes a predetermined voltage. It is what it is.

A second invention of this application is the first invention further comprising an overvoltage limiting circuit provided on the output side of the filter to remove transient output voltage spikes of the filter output. be.

[For production]

According to the first invention, the power output is switched by the switching element, smoothed by the filter, and supplied to the load connected in parallel to the switching element.

Such a configuration constitutes a switching type shunt regulator that has not conventionally existed.

The reason why switching type shunt regulators did not exist in the past is that conventional switching regulators were designed for use with ordinary commercial power sources. In other words, since a normal commercial power supply has constant voltage characteristics, if the switching regulator is configured as a shipt type, when the switching element is turned on, the power supply will be short-circuited and a large current will flow through the switching element, causing the switching element to It will be destroyed.

However, power supplies for small generators used in aircraft engines, etc. have characteristics close to constant current due to the inductance of the coil, so even if the switching element is turned on and the power supply is short-circuited, there will be no large current flowing through the switching element. No current flows, and destruction of the switching element can be avoided. Based on this idea, the present invention has made it possible to form a shunt regulator into a switching type h1 by combining it with a power supply having an inductance.

If configured as a switching type, the on-resistance of the control element can be reduced, so the amount of heat generated by the switching element can be reduced, and the switching element and heat dissipation mechanism can be made smaller, making the entire device smaller. It can be made light in weight and suitable for being mounted on an aircraft.

Furthermore, the filter configuration can be simplified by using the inductance within the power supply.

According to the second aspect of the invention, by providing an overvoltage limiting circuit on the output side of the filter, the overvoltage that occurs transiently when a disconnected generator line is connected, when the power is turned on, when the load suddenly changes, or when the load is cut off. Output voltage spikes can be removed. Furthermore, it is possible to prevent a steady output voltage rise that occurs when the device becomes close to a no-load state, the switching interval of the switching element becomes narrow, and control becomes uncontrollable.

(Example〕 An embodiment of this invention is shown in FIG.

The power source 10 is composed of a small generator of up to about 500 VA. The output of this power supply (three-phase AC) is rectified by 12r
! The DC output is applied to the power FET 20, which is a switching element, and is switched. The output of the power FET 20 is smoothed by a filter 22 and guided between output terminals 24 and 26 as an output path to be supplied to a load.

The error amplifier 16 compares the output voltage with the reference voltage 18 and P
The WM circuit 30 outputs a PWM signal that changes the on/off time ratio based on the comparison result, and controls the switching of the power FET 20. In other words, the output voltage is the reference voltage 1
When the voltage is higher than 8, the on time is lengthened to lower the output voltage, and when the output voltage is lower than the reference voltage, the on time is shortened and the output voltage is increased. This makes the output voltage constant.

The diode 28 is for guiding the electrical energy accumulated in the inductor (the coil of the small generator that constitutes the power supply 10) to the output when the power FET 28 is turned off, and for guiding the electric energy stored in the inductor (the coil of the small generator that constitutes the power supply 10) to the output, and for guiding the power F from the output side when the power FET 20 is turned on.
This prevents current from flowing back into the ET20.

The overvoltage limiting circuit 32 removes transient output voltage spikes that occur when a disconnected generator line is connected, when the power is turned on, or when the load suddenly changes. Further, it is possible to prevent a steady output voltage upper limit that occurs when the state approaches a no-load state.

According to the switching type shunt regulator shown in FIG. 1, when the power FET 20 is turned off from the on state, the voltage generated by the energy stored across the coil of the small generator constituting the power supply 10 is outputted via the diode 28. supplied to the load. Also, at this time, filter 3
2 is charged.

When the power FET 20 is turned on from the off state, the power FET20
The voltage across the ET 20 becomes almost zero, and the voltage stored in the filter 22 is output. As a result, output terminal 2
A smoothed constant voltage is obtained between 4.26 and 4.26. Further, when the power FET 20 is turned on, the power supply 10 is short-circuited, but since the power supply 10 has an inductance and a characteristic close to a constant current characteristic, a large current does not flow through the power FET 20 and it is not destroyed. In the switching type shunt regulator shown in Figure 1, heat generation is mainly caused by the power FET.
It is generated by the current that flows when 20 is turned on. but,
Since the power FET 20 has a small on-resistance, the amount of heat generated can be kept low. For example, even if the on-resistance of the power FET 20 is 0.1Ω and the current flowing when the power FET 20 is on is 10A, the loss is 1 if other losses are ignored.
0W, and the loss can be much reduced compared to conventional dropper type shunt regulators.

Therefore, the power FET 20 generates less heat, and the power FET 20 and the heat dissipation mechanism can be downsized.

Furthermore, heat is generated when the power FET 20 is switched from on to off and from off to on, but by using a high-speed element as the power FET 20 and shortening the switching time, the heat generation can be further suppressed.

Furthermore, by increasing the oscillation frequency of the PWM circuit 30, the filter 22 can be made smaller.

Furthermore, by utilizing the inductance within the power supply 10, the coil within the filter 22 can be made unnecessary. PWM elements, switching elements, and filter elements with high-speed response are appearing year by year, and there is a possibility that devices can be further downsized in the future. Note that a specific example of the switching type shunt regulator (the part after the rectifier 12) of FIG. 1 is not shown in FIG. 3, in which a bipolar power transistor or the like may be used instead of the power FET as the switching element 20.

In FIG. 3, the DC output from rectifier 12 is input to input terminals 34,36. Two power FET2OA,
20B constitutes a switching element, which is turned on and off alternately. Although the filter 22 is normally composed of a C filter, it is composed only of a capacitor C by using the inductance of the coil in the power supply 10 as an inductance portion. The overvoltage limiting circuit 32 applies an output voltage to a Zener diode 40 via a resistor 38, and applies the voltage across the resistor 38 between the pace emitter of the transistor 42. Thereby, even if a transient spike voltage occurs when a disconnected line of the power source 10 is connected, when the power is turned on, when the load suddenly changes, or when the voltage is cut off, the transistor 42 is turned on and the voltage can be released.

The control circuit board 44 is a PWM IC (SG3525A) 4
6, which constitutes an error amplifier and a PWM circuit. Each terminal ■~@ of the control circuit board 44 is a terminal ■~@ of the upper circuit
are connected to each.

The PWM IC 46 inputs the regulator output from the substrate terminal 2 to the IC terminal Nl. A reference voltage is output from the IC terminal VREG and input to the IC terminal INV. Then, the detection voltage input to the IC'4 child Nr and the IC terminal I
The reference voltages input to NV are compared, and P is alternately output from IC terminals A and 8 at an on/off time ratio according to the comparison result.
Outputs the WM signal and connects the board terminal 0. ■Power FE through
The voltage is applied to T2OA and 20B, and switching is controlled alternately.

〔Effect of the invention〕

As explained above, according to the first invention, the shunt regulator can be configured as a switching type by combining the AC power supply having an inductance with the DC power Mm obtained by rectifying the AC power supply. This makes it possible to reduce the on-resistance of the control element, thereby reducing the amount of heat generated during switching. Therefore, the switching elements and the heat dissipation mechanism can be made smaller, and the equipment can be made smaller and lighter, making it suitable for use on aircraft. - Also, the filter configuration can be simplified by using the inductance within the power supply. Further, according to the second invention, since the overvoltage limiting circuit is provided on the output side of the filter,
It is possible to eliminate output voltage spikes that occur transiently when a disconnected generator line is connected, when the power is turned on, when the load suddenly changes, when the load is cut off, etc. Furthermore, it is possible to prevent a steady increase in output voltage that occurs when the state approaches a no-load state.

Note that the present invention can also be combined with a power source having an inductance other than a small generator.

[Brief explanation of the drawing]

FIG. 11 is a block diagram showing an example of the present invention, FIG. 2 is a block diagram showing a conventional dropper type shunt regulator, and FIG. 3 is a circuit diagram showing a specific example of the switching type shunt regulator shown in FIG. 1. 20. 20A, 20B... switching element (power FET), 22... filter, 32... overvoltage limiting circuit, 44... IC for PWM.

Claims (2)

[Claims] (1) A switching element connected to a DC power source obtained by rectifying an AC power source having an inductance, a filter that smoothes the output voltage of this switching element, and an output of this filter connected in parallel with the switching element. The device includes an output path for supplying to a load, and a switching control circuit that detects voltage fluctuations between the output paths and controls switching of the switching element by changing an on/off time ratio so that a predetermined voltage is achieved. A switching type shunt regulator. (2) A switching element connected to a DC power source obtained by rectifying an AC power source having an inductance, a filter that smoothes the output voltage of this switching element, and an output of this filter connected in parallel with the switching element. an output path for supplying to a load; a switching control circuit that detects voltage fluctuations between the output paths and controls switching of the switching element by changing an on/off time ratio so that a predetermined voltage is reached; A switching type shunt regulator comprising an overvoltage limiting circuit provided on the output side to remove transient output voltage spikes of the filter output.