JPS5925576A - Switching regulator - Google Patents

Abstract

PURPOSE:To contrive to enhance efficiency and to reduce noise of switching by a method wherein the period of switching is variably controlled to attain matching with width of the resonance waveform of a switching electric power source, and a switching semiconductor is made to ON always with timing when the terminal voltage of the semiconductor is zero. CONSTITUTION:The temperature of the switching semiconductor in a switching electric power source 4 is detected by a temperature detecting circuit 7, moreover the resonance waveform in the switching electric power source 4 is detected by a waveform detecting circuit 8, and outputs thereof are inputted to a microcomputer 2. The microcomputer 2 makes the period of oscillation of oscillating output of an oscillator 3 and the duty ratio of ON, OFF to variably corresponding to the number of rotation set by a number of rotation setting circuit 1, and controls variably the switching period of the switching semiconductor to attain matching with width of the oscillation waveform of the switching electric power source 4, and the switching semiconductor is made to ON always with timing when the semiconductor terminal voltage is zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a switching regulator that supplies a variable applied voltage applied to, for example, speed control of a DC motor.

[Technical background of the invention and its problems]

FIG. 1 shows a conventional example of a switching regulator for a DC motor that performs speed control by varying the voltage applied to the DC motor. This switching regulator is a switching power supply circuit using a quasi-E class power supply circuit.

Here, a quasi-E class switching power supply circuit is one in which a diode is inserted into the LC resonant closed circuit that constitutes the power supply circuit when a switching semiconductor (for example, a switching transistor) is turned off, and transient oscillations that occur when the switching transistor is turned on and off are eliminated. A circuit that converts the phenomenon into a resonant waveform using the resonant capacitance and the reactance of the switching transformer, and turns on the switching semiconductor at the moment when the resonant waveform is attenuated and the emitter-collector voltage of the switching semiconductor becomes zero. That's true. That is, in Figure 1 (2), Qs is a switching transistor, RL is a dummy load of the motor, Ll! is a circuit inducting transistor Q, and a drive signal is input to the base of the transistor Q.
1 turns on, the collector current 1c increases (2 gradually (2) and similarly (-inductance Ll) as shown in Figure 2 (al).
As shown in Fig. 2 (h), the current IJ flowing in
-Increase.

Here, when the transistor Q1 is turned off, its collector current 1C becomes zero (2 (exactly): becomes 0 (until it becomes 2 (there is a two-hour delay). At this time, the current flows through the inductor, il tries to flow as it is, and eventually Attenuates to zero. The terminal voltage vc of the capacitor C rises sharply when the transistor Q1 is turned off, as shown in FIG. 2(C), and gradually decreases after reaching the saturation point. In this case, the coil current ip once flows in the same direction as the collector current 1c, but when the terminal voltage VC of the capacitor 0 is saturated, the coil current ip flows in the opposite direction (-
Start discharging. When this discharge (=Therefore, the terminal voltage VC of capacitor 0 approaches zero, the coil current ip reaches its maximum value and returns to its original direction (
Current begins to flow. When the terminal voltage vc becomes zero (=, the inductor current i/ begins to flow again gradually (-) as shown in Figure 2 (bl).Then, these coil current 1p, inductor current il!, and switching transistor Q1 are If the switching transistor Q1 is turned on when the values of 'F1m, i p and i lO become the same as each other, the operating waveforms (switching can be performed without reversing the two).

Here, in order to vary the voltage (2), a triangular wave as shown in Figure 2 (g) (=) is generated, and a comparator is used to generate a triangular wave as shown in Figure 2 (f).
) (= Construct a circuit that generates an output voltage pulse as shown in FIG. On the other hand, the resonance period of the power supply section is set to be constant due to the circuit constant. Therefore, with such a period T (=, the time from OFF to ON of the voltage pulse Width W! Width W1 is approximately equal to W, medium W, and the switching transistor Q1 has a capacitor terminal voltage vc.
When is approximately zero (can be adjusted), it is also possible to change the reference level (to vary the output voltage (-
It has become.

By the way, the resonant waveform width of a quasi-E class power supply circuit varies depending on the size of the load.As the load increases, the inductor current flowing through the power supply circuit (ff1lI!) increases, and The waveform width of voltage vc increases.On the other hand, since the switching pulse period is the same, the time width W from OFF to ON of the voltage pulse and the width W1 of the resonance waveform
Figure 2 (h) As shown in , the switching waveform becomes a bad waveform, and in the worst case it will be destroyed as above.Therefore, we adopted a method of changing the switching cycle according to the load. This was insufficient as a method to protect the switching semiconductor.In other words, an attempt was made to control the switching period of the switching semiconductor in two to three stages by reading the signal output from the microcomputer for iR) response width control that determines the motor applied voltage. [Objective of the Invention] This invention was made in view of the above circumstances, and its purpose is to provide high-efficiency, low-noise switching. An object of the present invention is to provide a switching regulator that can be used under conditions with large load fluctuations and has a wide guaranteed voltage range.

[Summary of the invention]

This invention detects the temperature of the switching semiconductor and the state of the resonant waveform when the switching semiconductor is on, and variably controls the switching period of the variable output voltage according to these detection results to adjust the resonant waveform width of the switching power supply. This switching semiconductor is configured to be matched and turned on at a timing when the semiconductor terminal voltage is always zero.

[Embodiments of the invention]

An embodiment of the invention will be described below with reference to the drawings. FIG. 3 shows a speed control device for a DC motor using the switching regulator of the invention. That is, l is a rotation speed setting circuit that sets the rotation speed of the motor, 2 is a microcomputer (hereinafter simply referred to as microcomputer), 3 is an oscillator, 4 is a switching power supply that obtains a DC output, 5 is an AC power supply, and 6 is a motor. , 7 is a temperature detection circuit for detecting the temperature of a switching semiconductor (not shown) in the switching power supply 4 and inputting it to the microcomputer 2. Reference numeral 8 denotes a waveform detection circuit which detects whether the resonant waveform is falling or rising when the switching semiconductor is turned on and inputs it to the microcomputer 2. According to this speed control device,
The temperature detection circuit 7 detects the temperature of the switching semiconductor and detects it by the microcomputer 2. (Secondly, the switching power supply 4 changes the switching time to variably control the voltage applied to the motor 6, thereby executing speed control in which the speed of the motor 6 is set to the set rotation speed.

゛The detailed circuit of the switching regulator is shown in FIG. This is a quasi-E class power supply circuit that obtains the corresponding direct output voltage from the output of the rectifier circuit 12 by varying the switching timing in accordance with the oscillation frequency variable voltage voltage. , 1.! Solution capacitor C8, capacitor f Ot s diode D,.

The output voltage of this power supply circuit 13 is supplied to the motor, which is the load RL. 3-bit output signal 00 to 0 according to the heat generation temperature and the detection waveform of the resonance waveform.
．． In addition, only the reference rotation speed of the setting circuit 1 (=3-pit output signals 03 to 0. is output accordingly).

In addition, 14 is an output signal from the microcomputer 2 to a frequency variable section, which will be described later, from 0° to O! This signal transmission unit 1
4 has an inverter I, to 11 and resistors R4 to R8. Furthermore, 15 has transistors Q2 to Q4%, resistors R1 to R13, and capacitors C, C4, and switches the OR time constant according to the output signals A to 0 from the signal transmission section 14 to change the period of the triangular wave. The variable oscillation frequency section 16 includes transistors Q!~QTl and resistors RI4~1'Ltt connected to the output terminal of the microcomputer 2,
A comparison reference voltage circuit 17 obtains a reference voltage for comparison, and a reference voltage circuit 17 performs predetermined signal processing using the time constant switched by the oscillation frequency variable section 15 and the comparison reference voltage from the circuit 16 to generate a voltage pulse having a predetermined period. 18 is a transformer T7 connected to the power supply circuit 13, a transistor Q8s, a capacitor O1l, 0
0, resistance R□~几, 4, and in response to the voltage pulse from the signal processing circuit 17, the switching transistor Q,
This is a drive circuit that drives the.

In such a configuration, the output signal 08-O of the microcomputer 2
7 are all at the N″0” level, the signal transmission circuit 14
outputs signals A, B, and O of the inverted °'1'' level from the inverter ■1 to I, i2.The transistors Q and Q4 of the variable section 5 that receive these signals remain off, Therefore, variable part 15 (two OR time constant 04 (R, +R
, ten liters.

10R+o) is selected.

Next, assuming that only the output signal O1 is at the l'' level,
The signal transmission circuit 14 outputs a signal with only the signal person at the 0'' level.Receiving this signal A, the variable section 15 turns on the transistor Q and sets a predetermined OR time constant 04 (几,
+R, +R1°).

Similarly, output signals O8-0. The OR time constant is changed depending on the level of . Then, the output signal Oo~0. are all tl
When the signal is at O'' level, the OR time constant is the largest, and conversely, when all the signals are at If1'' level, the OR time constant is the smallest.

Hiko, for example, a thermistor (temperature detector) 19 is provided near the switching transistor Q1, and the resistance value changes according to the heat generated by the switching transistor Q. The detection result of this thermistor 19 is sent to the temperature detection circuit 7.
(Two are supplied.

Next (Second), the operation in such a configuration will be explained.For example, in a switching regulator to which a motor with a predetermined load is connected, the microcomputer 2 outputs output signals O8 to O0 in response to the setting signal C2 from the rotation speed setting circuit 1. . is output. From this (2), a predetermined reference voltage is supplied to the signal processing circuit 17. At this time, the microcomputer output signal d.-b.

A triangular waveform a (shown in FIG. 5C) of the OR time constant selected by the variable section 15 is output from C2. As a result, the signal processing circuit 17 outputs a voltage pulse shown by the east line in FIG. 5(h) based on the OR time constant and the comparison reference voltage from the circuit 16. When the drive circuit 18 drives the switching transistor Q1 with this voltage pulse, the resonance waveform of the switching power supply becomes a waveform d shown in FIG. 5(a) (2).

Then, the motor 6 is controlled by this output voltage (second).

By the way, suppose that a motor with a load smaller than the predetermined load mentioned above is connected. Then, the resonant waveform becomes the fifth
As shown by the broken line C in Figure (a), the resonant voltage once becomes near zero, and then rises again. From this C2, when the resonant voltage is +EY, the switching transistor Ql is turned on,
This transistor Q! temperature increases. The temperature of the heat generated (as the resistance value of the thermistor 19 changes) is detected by the temperature detection circuit 7. At this time, the waveform detection circuit 8 detects that the resonant waveform is in the rising state. , this detection result is supplied to the microcomputer 2 (2).Thereby, the microcomputer 2 is supplied from the waveform detection circuit 8 that the waveform is a rising waveform (2).
It is determined that L has become small, and the OR time constant is switched in accordance with the detected temperature from the temperature detection circuit 7 to output output signals O8 to O1 that change the period of the triangular wave.

By using this output signal, the OR time constant of the first variable section 15 is shortened, and the period of the triangular wave generated in the first S processing circuit 17 is changed to the fifth
As shown in Figure (cJ) (2 waveform a to waveform b (2) By changing and shortening, as shown in Figure 5 (h) (2 period T1 to period T, (2 moved voltage pulse, that is, the frequency is higher) The resulting switching pulse is obtained by the signal processing circuit 17.

As a result, the switching transistor Q is on-off controlled by a voltage pulse in which the resonant waveform (=WS) of the power supply circuit 13 and the time width W of the voltage pulse are equal.

Therefore, the waveform of the switching transistor Q+ is shown by the broken line in FIG.
A normal sine waveform such as waveform 0 shown by the east line +8+ in the figure is obtained, and the switching transistor Q1 does not generate heat and is prevented from being destroyed.

Also, assume that a load larger than a predetermined load is connected. Then, the resonant voltage drops to zero (+='F before becoming 2). Due to this, the temperature of the switching transistor Q1 rises, and as the resistance value of the thermistor 19 changes from that temperature (2), the temperature is detected by the temperature detection circuit 7.

Further, at this time, the waveform detection circuit 8 detects that the resonance waveform is in a falling state, and this detection result is supplied to the microcomputer 2C. From this (2), the microcomputer 2 determines that the waveform detection circuit 8 is supplied with a falling waveform from the circuit 8 (2), and determines that the load ratio has become larger, and accordingly detects the temperature detected from the temperature detection circuit 7. An output signal is output that changes the period of the triangular wave by switching the OR time constant.

This output signal lengthens the OR time constant of the variable part 15 (secondarily, the voltage pulse with a longer cycle of the triangular wave generated in the signal processing circuit 17, that is, the switching pulse with a lower frequency) is applied to the signal processing circuit 17. As a result, the switching transistor Q1 is controlled on-off by a voltage pulse (2) in which the resonant waveform width W1 of the power supply circuit 13 and the time width W of the voltage pulse are equal.

Therefore, the waveform of the switching transistor Q1 does not become a defective waveform, but becomes a normal sine waveform, and the switching transistor Q+ does not generate heat and is prevented from being destroyed.

As mentioned above, if a high-efficiency, low-noise switching power supply can be used under conditions with large load fluctuations (2), the guaranteed voltage range will also be from ``100+JCP10'' to RL.
oo"'"Lived a wide life. Further, the variable rotation speed ratio of the DC motor can be brought closer to ioo% from 50% in the conventional case.

It should be noted that in addition to the motor speed control of the embodiment described above, other devices (2) can also be applied.

〔Effect of the invention〕

As described in detail above, according to this invention C2, it is possible to provide a switching regulator that can be used for high efficiency, low noise switching bm under conditions of large load fluctuations, and has a wide guaranteed voltage range.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a switching regulator applied to a conventional motor speed control device, and Fig. 2 (a) to (￥
1 is a waveform diagram for explaining the circuit operation of the switching regulator shown in FIG. 1, FIGS. 3 to 5 show an embodiment of the present invention, and FIG. 3 is a motor speed control device according to the present invention. FIG. 4 is a diagram showing the overall circuit configuration, and FIGS. 5(3) to 5(c) are waveform diagrams for explaining the operation. 2...Microcomputer, 4...Switching power supply, 5...
- AC @ power supply, 7... temperature detection circuit, 8... waveform detection circuit, 13... power supply circuit, 14... signal transmission section, 1
5... Oscillation frequency variable section, 16... Reference voltage circuit,
17... Signal processing circuit, 18... Drive circuit, 19.
...Thermistor (temperature detector), Q,...Switching transistor (switching semiconductor), RL...Load (motor). Figure 1 Figure 2 Figure 2 (h) (i)

Claims (1)

[Claims] A switching regulator comprising a quasi-E class switching power supply circuit that has a switching semiconductor that is controlled on-off by a switching pulse and obtains a predetermined output control voltage applied to a load according to a duty ratio of the switching pulse, wherein the switching semiconductor waveform detection means for detecting whether the resonant waveform is rising or falling when turned on; temperature detection means for detecting the temperature of the switching semiconductor; a detection result of this detection means; and a detection result of the waveform detection means. control means for variably controlling the frequency of the switching pulse of the variable output control voltage according to the output control voltage; A switching regulator characterized in that the switching semiconductor is configured to turn on at zero timing.