JPH0219703B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a switching regulator used for controlling the speed of a DC motor, for example.

[Technical background of the invention and its problems] Generally, when controlling the speed of a DC motor,
A switching regulator is used.

This switching regulator is equipped with a resonant circuit consisting of a coil and a capacitor, and a switching semiconductor for exciting this resonant circuit, and by driving the switching semiconductor on and off and setting its on and off duty, It can output variable level voltage. For example, there is the one shown in Japanese Patent Application Laid-Open No. 56-150968 or the one shown in FIG.

In FIG. 1, Ein is a DC power supply, and the voltage of the DC power supply Ein is applied to a resonant circuit consisting of a coil Lp and a capacitor C. A switching semiconductor such as an NPN transistor _Q1 between the collector and emitter and a damper diode _D1 are connected in parallel to the capacitor C. Furthermore, a rectifier circuit consisting of a diode _D2 and a smoothing capacitor Cs is connected to the coil Lp via an inductance Ll, and a load R is connected to the output end of the rectifier circuit.

Note that Lp and Ll equivalently represent a transformer consisting of a primary coil and a secondary coil, where Lp is the primary inductance and Ll is the leakage inductance. Moreover, the load R is a dummy load of the DC motor.

That is, when the transistor _Q1 is turned on, the collector current ic of the transistor _Q1 gradually increases as shown in Figure 2a, and the inductance also increases.
The inductor current il flowing through Ll also gradually increases as shown in FIG. 2b. And transistor Q ₁
When turned off, its collector current il becomes zero (strictly speaking, there is a time delay before it becomes zero). At this time, the inductor current il tries to flow as it is, and eventually attenuates to zero. On the other hand, capacitor C
As shown in FIG. 2c, the terminal voltage Vc of the transistor _Q1 rises rapidly at the same time as the transistor Q1 is turned off, and then gradually decreases after reaching the saturation point. In this case, the coil Lp
The current ip flowing through the capacitor C once flows in the same direction as the collector current ic, but when the terminal voltage Vc of the capacitor C becomes saturated, it starts discharging in the opposite direction. When the terminal voltage Vc of the capacitor C becomes near zero due to this discharge, the coil current ip reaches its maximum value, as shown in FIG. 2d, and begins to flow in the original direction. Terminal voltage Vc
When becomes zero, the inductor current il gradually begins to flow again as shown in FIG. 2b.

In this way, by turning on and off the transistor _Q1 , a resonant circuit consisting of the coil Lp and the capacitor C is excited, and a voltage at a predetermined level corresponding to the inductor current il is rectified and smoothed and supplied to the load R.

In this switching regulator, in order to change the level of the output voltage (voltage supplied to the load R), a triangular wave voltage as shown in Fig. 3c is generated, and the triangular wave voltage and the reference voltage H are connected by a comparator. A voltage pulse as shown in FIG. 3b is obtained by comparing the two voltages, and the voltage pulse is applied as a switching signal to the transistor _Q1 . and,
It is sufficient to adjust the level of the reference voltage H and change the on/off duty (ratio of high level period to zero level period) of the voltage pulse.

That is, if the level of the reference voltage H is lowered, the off-period _W2 of the voltage pulse becomes longer, and the voltage of the resonant circuit (the terminal voltage Vc of the capacitor C,
The waveform width W ₁ of the collector-emitter voltage of transistor Q ₁ becomes longer, and the level of the output voltage increases. Conversely, if the level of the reference voltage H is increased, the off-period _W2 of the voltage pulse will be shortened, and the voltage of the resonant circuit (hereinafter referred to as the resonant voltage) will decrease accordingly.
The waveform width _W1 becomes shorter, and the output voltage level decreases.

By the way, in this switching regulator, transistor _Q1 turns on
From the standpoint of protecting _Q1 , improving efficiency and reducing noise, it is best to perform this when the resonant voltage is at zero level.

However, if the magnitude of the load R changes,
As the inductor current il changes, the waveform width of the resonant voltage
W ₁ changes.

For example, when the load R increases, the inductor current il increases, and the waveform width of the resonant voltage increases accordingly.
W ₁ becomes longer. The waveform of the resonant voltage in this case is shown in FIG.

In this way, when the waveform width W ₁ of the resonant voltage becomes longer,
A situation occurs in which transistor _Q1 turns on before the resonant voltage drops to zero level, leading to a decrease in efficiency and an increase in noise, and in the worst case, the transistor Q1 turns on.
Causes destruction of Q ₁ .

Also, as the load R increases, the inductor current
il decreases, and the waveform of the resonant voltage becomes a defective waveform, as shown in FIG. 5, which temporarily drops to near the zero level and then rises again.

In this case, when the resonant voltage rises again, a situation occurs in which the transistor Q ₁ is turned on, resulting in a decrease in efficiency and an increase in noise as described above, and in the worst case, destruction of the transistor Q ₁ .

[Purpose of the Invention] This invention was made in view of the above circumstances, and its purpose is to ensure optimal on-timing of a switching semiconductor regardless of load fluctuations; An object of the present invention is to provide a switching regulator which prevents destruction of a switching semiconductor and always enables voltage output with high efficiency and low noise.

[Summary of the Invention] The present invention provides a switching leg that includes a resonant circuit consisting of a coil and a capacitor, a switching semiconductor for exciting the resonant circuit, and outputs a predetermined voltage by turning on and off the switching semiconductor. In the generator, waveform detection means detects whether the voltage waveform of the resonant circuit is rising or falling when the switching semiconductor changes from off to on, and temperature detection means detects a rise in temperature of the switching semiconductor. and,
When the outputs of the temperature detection means and the waveform detection means are input and the temperature detection means detects a temperature rise of the switching semiconductor, when the waveform detection means detects that the voltage waveform of the resonant circuit is rising,
The on/off frequency of the switching semiconductor is controlled to be small, and when the waveform detection means detects a fall of the voltage waveform of the resonant circuit, the on/off frequency of the switching semiconductor is controlled to be large. , and off control means.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In Fig. 6, 1 is an AC power supply, and the power supply 1
Connect the main circuit 10 to. This main circuit 10 converts the AC voltage of the power supply 1 into DC, converts the DC voltage into AC of a predetermined frequency and voltage by switching, rectifies it, and supplies it to the DC motor 2 as driving power. It is.

Further, 90 is a microcomputer which is a main control unit, and this microcomputer 90
A drive control section 30, a rotation speed setting section 100, a temperature detection circuit 110, and a waveform detection circuit 120 are connected to.

The drive control unit 30 is a microcomputer 90
The main circuit 10 is switched and driven in response to commands from the main circuit 10.

The rotation speed setting section 100 is for setting the rotation speed of the motor 2, and setting data is supplied to the microcomputer 90.

The temperature detection circuit 110 detects the temperature of the switching semiconductor in the main circuit 10, and the detected data is supplied to the microcomputer 90.

The waveform detection circuit 120 detects whether the voltage waveform of the resonant circuit in the main circuit 10 is rising or falling, and the detected data is supplied to the microcomputer 90.

A detailed circuit of this switching regulator is shown in FIG.

The main circuit 10 takes in the power supply voltage of the AC power supply 1 to the diode bridge 12 via the filter 11 for suppressing surge input.
The rectified output of 2 is supplied to a smoothing capacitor 14 via a resistor 13. Furthermore, smoothing capacitor 1
4, a series resonant circuit consisting of a primary coil 15a of a transformer 15 and a capacitor 16 is connected to the capacitor 16, and a switching semiconductor such as an NPN transistor 17 between the collector and emitter and a damper diode 18 are connected in parallel to the capacitor 16. ing. The secondary coil 15b of the transformer 15 has a diode 19, a coil 20,
A rectifier circuit consisting of a smoothing capacitor 21 and a smoothing capacitor 21 is connected, and the output voltage of the rectifier circuit is supplied to the DC motor (load) 2. In addition, a voltage pulse supplied from a drive circuit 60, which will be described later, is connected to a resistor 2.
The voltage generated in the resistor 23 is applied between the base and emitter of the transistor 17.

That is, when the transistor 17 is turned on and off, a resonant circuit of the primary coil 15a and the capacitor 16 is excited, and a high frequency current flows through the primary coil 15a. Then, an alternating current of a predetermined frequency and voltage is generated in the secondary coil 15b based on the high frequency current,
The AC voltage is rectified by a diode 19, a coil 20, and a smoothing capacitor 21, and becomes an output voltage.

The drive control section 30 includes an integration circuit 40, a signal processing circuit 50, a drive circuit 60, a signal transmission circuit 70, and a reference voltage generation circuit 80.

Here, the integrating circuit 40 takes in the DC voltage Vdd into a capacitor 41, and applies the voltage of this capacitor 41 to a series circuit of resistors 42a, 42b, 42c, 42d and a capacitor 43. and,
A series circuit between the emitter and collector of the PNP transistor 44a and the resistor 45a is connected to the resistor 42a.
PNP type transistor 4
A series circuit between the emitter and collector of the PNP transistor 44c and the resistor 45b is connected in parallel to the resistors 42a and 42b, and a series circuit between the emitter and collector of the PNP transistor 44c and the resistor 45c is connected in parallel with the resistors 42a, 42b, and the resistor 45b. Connect in parallel to 42c. Further, transistors 44a, 44b, 4
Output signals A, B, and C from the signal transfer circuit 70 are applied to the base of the signal transfer circuit 4c, respectively. Then, the voltage of the capacitor 43 is supplied to the signal processing circuit 50 as an output.

That is, by selectively turning on the transistors 44a, 44b, and 44c according to the signals A, B, and C, the time constant of the output voltage changes.

The signal processing circuit 50 constitutes an oscillation circuit together with the integrating circuit 40, and takes in the output voltage of the integrating circuit 40 to generate a triangular wave voltage of a predetermined frequency. Further, the signal processing circuit 50 constitutes a pulse voltage generation circuit together with the drive circuit 60, and compares the generated triangular wave voltage with the reference voltage H from the reference voltage generation circuit 80, and drives the signal by the comparison output. The circuit 60 is controlled and the drive circuit 60 generates a voltage pulse with a predetermined pulse width.

The drive circuit 60 connects the DC voltage Vdd to the capacitor 6.
1 and the voltage of the capacitor 61 as NPN
The voltage of the capacitor 61 is applied to the primary coil of the pulse transformer 63 through the collector and emitter of the type transistor 62, and the voltage of the capacitor 61 is applied to the
5,66 series circuits. Furthermore, resistance 6
4 and 65 are connected to the output terminal of the signal processing circuit 50, and the voltage generated across the resistor 66 is applied between the base and emitter of the transistor 62. Then, the voltage generated in the secondary coil of the pulse transformer 63 is supplied to the main circuit 10 as a switching drive signal. Note that 67 is a stabilizing capacitor.

That is, the drive circuit 60 is the signal processing circuit 50
When the output terminal of the signal processing circuit 50 is at a high level, the transistor 62 is turned on and current flows through the primary coil of the pulse transformer 63. When the output terminal of the signal processing circuit 50 is at a low level, the transistor 62 is turned off and current flows through the primary coil of the pulse transformer 63. The current to the coil is cut off, and voltage pulses are generated in the secondary coil of the pulse transformer 63 by turning on and off the current.

The signal transmission circuit 70 is connected to the microcomputer 9
The input terminals of inverter circuits 71a, 71b, 71c are connected to the output ports O ₀ , O ₁ , O ₂ of 0, respectively, and the inverter circuits 71a, 71b, 71c
The outputs are taken out via resistors 72a, 72b, and 72c, respectively, and supplied to the integrating circuit 40 as signals A, B, and C.

The reference voltage generation circuit 80 applies a DC voltage Vdd to a series circuit of resistors 81, 82, 83, 84, and 85, and applies the voltage obtained at the interconnection point of the resistors 81 and 82 to the signal processing circuit 50 as a reference voltage H. supply Furthermore, a series circuit between the resistor 86a and the collector-emitter of the NPN transistor 87a is connected in parallel to the resistors 83, 84, and 85, and the resistor 8
6b and the collector of NPN type transistor 87b.
A series circuit between the emitters is connected in parallel to the resistors 84 and 85, and a series circuit between the resistor 86c and the collector and emitter of the NPN transistor 87c is connected in parallel to the resistor 85. The bases of transistors 87a, 87b, and 87c are connected to output ports _O3 , _O4 , and _O5 of microcomputer 90, respectively.

That is, the level of the reference voltage H changes by selectively turning on the transistors 87a, 87b, and 87c in accordance with the output signals of the output ports _O3 , _O4 , and _O5 of the microcomputer 90.

The temperature detection circuit 110 has a thermistor 110a as a temperature detector, and the thermistor 1
10a is provided near the transistor 17 in the main circuit 10.

The waveform detection circuit 120 detects the resonance voltage (terminal voltage of the capacitor 16 or collector-emitter voltage of the transistor 17) in the main circuit 10 by capturing the voltage generated in the secondary coil 15b of the transformer 15 in the main circuit 10. Detect whether the waveform is rising or falling.

The microcomputer 100 outputs a 3-bit signal from output ports O ₃ , O ₄ , O ₅ according to the rotation speed set by the rotation speed setting section 100 , and also outputs a 3-bit signal corresponding to the rotation speed set by the rotation speed setting section 100 . A 3-bit signal corresponding to the temperature and the detection result of the waveform detection circuit 120 is output from output ports O ₀ , O ₁ , and O ₂ .

Next, the operation in the above configuration will be explained.

When the power is turned on, the microcomputer 90 outputs a 3-bit signal from the output ports O ₀ , O ₁ , and O ₂ in order to generate a triangular wave voltage of a predetermined frequency that is predetermined in consideration of the rotation constant of the main circuit 10. do.
This output signal is sent to the signal transmission circuit 70 as signals A, B,
C and is supplied to the integrating circuit 40. The integrating circuit 40 selects a time constant according to the signals A, B, and C, and supplies a voltage that changes with the selected time constant to the signal processing circuit 50. The signal processing circuit 50 uses the output voltage of the integrating circuit 40 to generate a triangular wave voltage [waveform a in FIG. 8c] of a predetermined frequency.

In this case, if the output signals of the output ports O ₀ , O ₁ , and O ₂ are all logic "0", the signals A, B, and C of the signal transmission circuit 70 are transferred to the inverter circuit 71.
A, 71b, 71c are inverted and all logic “1”
becomes. Then, in the integrating circuit 40, the transistors 44a, 44b, and 44c are all turned off, and a time constant is selected according to the combined resistance value of the resistors 42a, 42b, 42c, and 42d and the capacitance of the capacitor 43. This time constant is the largest.

Furthermore, if the output signals of the output ports O ₀ and O ₁ are logic "0" and the output signal of the output port O ₂ is logic "1", the signals A and B of the signal transfer circuit 70 are logic "1". , signal C becomes logic "0". At this time, in the integrating circuit 40, the transistor 44
a, 44b are turned off, the transistor 44c is turned on, and the resistance value of the resistor 42d and the capacitor 43 are approximately equal.
A time constant is selected according to the capacity of This time constant is the smallest.

The triangular wave voltage generated in the signal processing circuit 50 is compared with the reference voltage H from the reference voltage generation circuit 80, and a voltage pulse [the solid line waveform in FIG. 8b] with a pulse width corresponding to the comparison result is applied to the drive circuit. Occurs at 60.

The voltage pulse generated by the drive circuit 60 is supplied to the transistor 17 of the main circuit 10, and turns the transistor 17 on and off.

When the transistor 17 is turned on and off, a resonant circuit consisting of the primary coil 15a and the capacitor 16 is excited, and a high frequency current flows through the primary coil 15a. As a result, an alternating current of a predetermined frequency and voltage is generated in the secondary coil 15b, and the alternating current voltage is rectified and supplied to the direct current motor (load) 2. In this case, the resonant voltage generated between the collector and emitter of the capacitor 16 or transistor 17 has a waveform d in FIG. 8a.

In order to change the voltage supplied to the DC motor (load) 2, the set rotation speed of the rotation speed setting section 100 may be changed.

When the set rotation speed is changed, the microcomputer 90 changes the states of the output signals at the output ports O ₃ , O ₄ , and O ₅ .

In this case, if the output signals of the output ports O ₃ , O ₄ , O ₅ are all logic "0", then the transistors 87a, 87b, 87c of the reference voltage generation circuit 80
are all turned off, and the voltage generated in the series circuit of resistors 82, 83, 84, and 85 becomes reference voltage H.

Further, if the output signals of the output ports O ₃ and O ₄ are logic "0" and the output signal of the output port O ₅ is logic "1", the transistors 87a and 87b of the reference voltage generation circuit 80 are turned off, and the transistor 87c
is turned on, and the voltage generated in the series circuit of resistors 82, 83, and 84 becomes the reference voltage H.

By changing the reference voltage H in this way, the on/off duty of the voltage pulse generated in the drive circuit 60 changes, and the off period
The longer W ₂ is, that is, the longer the off-period of transistor 17 is, the higher the output voltage of main circuit 10 is.

By the way, when the DC motor 2 with a large load is connected, the waveform width _W1 of the resonant voltage becomes longer, and there is a situation where the voltage pulse rises and the transistor 17 is turned on before the resonant voltage drops to the zero level. arise.

At this time, the transistor 17 is turned on with a voltage applied between its collector and emitter, so heat is generated and the temperature rises. This temperature rise is detected by the temperature detection circuit 110 as a change in the resistance value of the thermistor 110a.
The detected temperature is supplied to the microcomputer 90.

Further, the waveform detection circuit 120 constantly detects whether the waveform of the resonance voltage is rising or falling, and the detection result is supplied to the microcomputer 90.

The microcomputer 90 has a temperature detection circuit 1
When the detected temperature 10 reaches a predetermined value or higher, the microcomputer 90 determines whether the voltage waveform of the resonant circuit is "rising" or "falling" when the switching semiconductor in the main circuit 10 changes from off to on. Read from the output of the waveform detection circuit 120. If the detection result of the waveform detection circuit 120 at that time is "falling", it is determined that the transistor 17 is turned on before the resonance voltage reaches the zero level due to the large load R, and the output port O ₀ ,
A command is given to the signal transmission circuit 70 by the output signals of O ₁ and O ₂ to increase the time constant of the integration circuit 40 .
In this case, the higher the temperature detected by the temperature detection circuit 110, the larger the time constant.

As the time constant of the integrating circuit 40 becomes larger, the frequency of the triangular wave voltage generated in the signal processing circuit 50 becomes lower, and accordingly, the period _T1 of the voltage pulse generated in the drive circuit 60 becomes longer.

In this way, if the period T ₁ of the voltage pulse becomes longer,
The off-period _W2 of the voltage pulse also becomes longer, and the rising timing of the voltage pulse, that is, the on-timing of the transistor 17, comes to correspond to the point in time when the resonant voltage drops to the zero level.

Therefore, even if the DC motor 2 with a large load is connected, the optimal on-timing of the transistor 17 can be ensured regardless of the connection, thereby preventing destruction of the transistor 17, and always maintaining high efficiency and high efficiency. Low noise voltage output is possible.

Also, contrary to the above, the DC motor 2 with a small load
When connected, the resonant voltage becomes a bad waveform, as shown by the waveform c in Figure 8a and the change in the broken line from the middle of the waveform, which drops to near the zero level and then rises again, and the resonant voltage becomes +EV. When this happens, a voltage pulse rises and transistor 17 turns on.

At this time, the transistor 17 is turned on with a voltage applied between its collector and emitter, so heat is generated and the temperature rises. This temperature rise is detected by the temperature detection circuit 110 as a change in the resistance value of the thermistor 110a.
The detected temperature is supplied to the microcomputer 90.

The microcomputer 90 has a temperature detection circuit 1
When the detected temperature 10 reaches a predetermined value or higher, the microcomputer 90 determines whether the voltage waveform of the resonant circuit is "rising" or "falling" when the switching semiconductor in the main circuit 10 changes from off to on. Read from the output of the waveform detection circuit 120. If the detection result of the waveform detection circuit 120 at that time is "rising", it is determined that the transistor 17 is turned on when the load R is small and the resonance voltage is not at zero level, and the output ports O ₀ , O ₁ ,
A command is given to the signal transmission circuit 70 by the output signal of O ₂ to reduce the time constant of the integration circuit 40. In this case, the higher the temperature detected by the temperature detection circuit 110, the smaller the time constant.

As the time constant of the integrating circuit 40 becomes smaller, the frequency of the triangular wave voltage generated in the signal processing circuit 50 increases [changes from waveform a to waveform b in FIG. The period of the pulse changes from T ₁ as shown in Figure 8b.
Shortens to T ₂ .

In this way, if the period of the voltage pulse becomes shorter, the OFF period of the voltage pulse also becomes W ₂ as shown in FIG. 8b.
to W ₂ ', and the rising timing of the voltage pulse, that is, the timing at which the transistor 17 turns on, corresponds to the time when the resonant voltage drops to near the zero level (before rising again as shown by the broken line).

Therefore, it is possible to ensure the optimal on-timing of the transistor 17 regardless of the decrease in the load 2, thereby preventing the transistor 17 from being destroyed, and also making it possible to always output voltage with high efficiency and low noise. It is.

In the above embodiment, the application to speed control of a DC motor has been described, but the invention can also be applied to other devices as long as they require variable voltage.

In addition, in this example, the reason why the temperature rise of the switching semiconductor is used as a condition for changing the on/off frequency of the switching semiconductor is that it is easy to detect whether the voltage waveform of the resonant circuit is "rising" or "falling", and the switching This takes into consideration the stability of the semiconductor's on and off frequencies.

In other words, if there is a slight deviation between the on/off state of the switching semiconductor and the voltage waveform of the resonant circuit, the voltage waveform of the resonant circuit will "rise" or "fall".
Furthermore, if the on/off frequency of the switching semiconductor is precisely matched to the voltage waveform of the resonant circuit, the on/off frequency of the switching semiconductor will constantly change due to load fluctuations, which may affect stability. There is a problem with missing parts.

On the other hand, in a state that causes the temperature of the switching semiconductor to rise, the deviation between the OFF/ON state of the switching semiconductor and the voltage waveform of the resonant circuit becomes large to some extent, so the "rising" and "falling" of the voltage waveform of the resonant circuit increases. can be detected extremely easily and accurately.

In addition, switching semiconductors are destroyed by temperature rises, and by correcting the "shift" between the switching semiconductor's on/off state and the resonant frequency of the resonant circuit when the temperature rises, switching semiconductors can protect and improve efficiency. It is quite possible to achieve low noise.

[Effects of the Invention] As described above, according to the present invention, in a switching regulator that outputs a predetermined voltage by turning on and off a switching semiconductor for exciting a resonant circuit consisting of a coil and a capacitor, , when the temperature rise of the switching semiconductor is detected, if the voltage waveform of the resonant circuit when the switching semiconductor changes from off to on is rising, the on/off frequency of the switching semiconductor is controlled to be small. If the voltage waveform of the resonant circuit is falling, the on/off frequency of the switching semiconductor is controlled to be small, so the on/off timing of the switching semiconductor is adjusted to the resonant voltage of the resonant circuit regardless of load fluctuations. It is possible to provide a switching regulator that can be matched, thereby preventing destruction of the switching semiconductor, and also capable of outputting a voltage with high efficiency and low noise.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an example of a conventional switching regulator, and Fig. 2 a, b, c, and d are diagrams showing the configuration of an example of a conventional switching regulator.
Figures 3a, b, and c are signal waveform diagrams for explaining the operation of the switching regulator shown in Figure 1. 4 and 5 are diagrams showing examples of resonant voltage waveforms of the switching regulator shown in FIG. 1, respectively, FIG. 6 is a diagram showing the overall configuration of an embodiment of the present invention, and FIG. FIGS. 8a, 8b, and 8c are diagrams showing the detailed configuration of the embodiment, and are signal waveform diagrams for explaining the operation of the embodiment. 2...Load (DC motor), 10...Main circuit,
30... Drive control section, 40... Integrating circuit, 50...
...Signal processing circuit, 60...Drive circuit, 70...Signal transmission circuit, 80...Reference voltage generation circuit, 90...
... Microcomputer, 110 ... Temperature detection circuit, 120 ... Waveform detection circuit.

Claims (1)

[Claims] 1. A switching regulator that includes a resonant circuit consisting of a coil and a capacitor, and a switching semiconductor for exciting this resonant circuit, and outputs a predetermined voltage by driving the switching semiconductor on and off. a waveform detection means for detecting whether a voltage waveform of the resonant circuit is rising or falling when the switching semiconductor changes from off to on; and a temperature detecting means for detecting a rise in temperature of the switching semiconductor. a detection means; an output of the temperature detection means and an output of the waveform detection means are input; and when the temperature detection means detects that the temperature of the switching semiconductor has increased, the waveform detection means detects a rise in the temperature of the resonant circuit; When detecting that the voltage waveform is rising, the on/off frequency of the switching semiconductor is controlled to be small; and when the waveform detecting means detects that the voltage waveform of the resonant circuit is falling; . A switching regulator comprising: on/off control means for controlling the on/off frequency of the switching semiconductor to be increased.