JPS5840202B2 - switching regulator - Google Patents

Description

[Detailed description of the invention] The present invention relates to switching regulators.

Generally, a switching regulator has a protection function against overcurrent output and overvoltage output, and protects a load connected to the power supply device and the power supply device itself.

An example of such a switching regulator is the first
As shown in the figure, the DC voltage obtained by converting the AC input voltage through a rectifying and smoothing circuit is converted back to AC voltage by the variable output inverter, and this inverter output is boosted (or stepped down) by an isolation transformer, then rectified and It is converted into a DC output voltage through a wave circuit.

The variable inverter repeats ON and OFF operations according to the pulse voltage supplied from the pulse width conversion circuit through the drive circuit.

The pulse width conversion circuit controls the pulse width of the pulse supplied from the pulse generator in response to the overcurrent signal voltage supplied from the overcurrent detection amplifier and the error voltage supplied from the error voltage amplifier, and converts the overcurrent signal voltage to the overcurrent signal voltage supplied from the overcurrent detection amplifier. Turn on the variable output inverter so that it is below the reference voltage, and so that the error between the DC output voltage and base pressure is always zero.

Change the OFF operation time ratio.

The error voltage amplifier uses the DC output voltage of the switching regulator as input, and the overcurrent detection amplifier uses the voltage difference between the resistors connected to the O volt line of the rectifier and filter circuit as input.

As described above, the output of the switching regulator is stabilized and protected from overcurrent and overvoltage.

Conventionally, when the rectifier and filter circuit RF is configured as shown in FIG. 2, when the load LD is short-circuited, the smoothing capacitor C8 is removed from the circuit.

That is, the charging/discharging current of the choke coil L increases, and the current L discharged through the overcurrent detection resistor R and the flywheel diode D becomes a large sawtooth wave including ripple voltage.

Therefore, the overcurrent detection amplifier supplies a pulsating voltage including a ripple waveform to the pulse width conversion circuit.

- A large sawtooth current containing ripple voltage flows from the choke coil L to the short-circuited load, and the error voltage supplied from the error voltage amplifier to the pulse width conversion circuit has a ripple waveform. Become.

Furthermore, if an integrating circuit is inserted into the error voltage amplifier in order to eliminate such pulsating voltage, the output thereof will have a phase lag.

Overcurrent signal voltage and error voltage LJ as described above.

It can cause instability in the operation of the pulse width conversion circuit, causing oscillation and intermittent operation, causing abnormal noises from the power supply, and even causing abnormal phenomena such as excessive current flowing through the load. .

In addition, if the ripple in the output current is large and the capacitor is short-circuited (J switching noise absorption is low, S
This has the disadvantage that it causes deterioration of N, adds noise to the output voltage, and makes it difficult to construct a stable power supply.

The present invention (j has been made to eliminate the above drawbacks,
The present invention provides a switching regulator that stably performs pulse width conversion by removing pulsating components and ripple components of the outputs of an overcurrent detection amplifier and an error voltage amplifier using an integrating circuit.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Incidentally, in order to simplify the explanation, the explanation of the parts similar to those of the conventional switch regulator will be omitted.

In FIG. 3, reference numeral 10 denotes an error voltage amplifier. This amplifier 10 receives the DC output voltage of the switching regulator at terminal A, and transfers this voltage to the reference voltage (in the illustrated example, the Zener voltage) in the differential amplifier OA1. ), and the output voltage, which changes on the order of 2 from +15V to -15V according to the difference voltage, is sent to the next stage pulse width conversion circuit 11.

In the pulse width conversion circuit 11, the output voltage from the error voltage amplifier 10 is connected to a resistor R1, a resistor R2, and a capacitor C.
The comparator CO
It is given to the single force input of M.

Reference numeral 12 indicates an overcurrent detection amplifier, which receives at terminal B a detection voltage associated with an overcurrent from rectification and F-wave heating.

This detection voltage is converted into a voltage of, for example, 0 to -50 mV, and then supplied to the single input of the differential amplifier OA2.
compared to a reference voltage.

These differential amplifiers generate an output voltage that varies from, for example, +15V to 0V in accordance with the difference in input voltage, and is supplied between the capacitor C and the resistor R2 of the pulse width conversion circuit 11.

A clock signal is supplied to the terminal P of the pulse width conversion circuit 11, which controls the conduction of the transistor Tr1 and also controls the conduction of the transistor Tr1.
Control AND gate NA.

The comparator COM compares the triangular wave voltage from the integrating circuit with a reference voltage to generate an output, which is input to the NAND gate NA via an inverter.

Since the present invention is configured as described above, the pulse width conversion circuit 1
The voltage applied to the integrating circuit 1 is the voltage applied to the overcurrent detection amplifier 1.
2 and/or the magnitude of the output voltage of the error voltage amplifier 10.

Therefore, the voltage level of the triangular wave voltage supplied to the comparator COM changes in proportion to the output voltage of the amplifier 10.12, thereby changing the pulse width from the pulse width conversion circuit 11 and changing the output of the variable output inverter. Vary the pulse width.

The above operation will be explained using waveform diagrams.

As shown in FIG. 4, A is the clock signal input to the P terminal, and B is the input voltage (triangular wave voltage) of the comparator COM. For example, when the output voltage of the output inverter becomes large, the output of the error voltage amplifier 10 becomes low. Since the charging current to the capacitor C flows to the amplifier 10 side, the waveform becomes small as shown in waveform a.

- When the power, for example, the overvoltage applied to the overcurrent detection amplifier 12 becomes smaller, the output of the amplifier 12 becomes larger and becomes a large triangular wave as shown in the waveform.

That is, the amplifiers 10 and 12 change the waveform from a triangular wave to a waveform depending on the content of the input voltage.

C1 is NAN when the input terminal of comparator COM has waveform a.
The input signal of the D gate NA is shown, and C2 shows the input signal of the NAND gate NA when the waveform is 1.

These input signals together with clock A are connected to NAND gate N
When inputted to A, its output becomes the output of Dl when the waveform is a, and becomes the output of D2 when the waveform is a, and is supplied to the drive circuit.

That is, when the DC output voltage to the error voltage amplifier 10 increases, or when the detection voltage to the overcurrent detection amplifier 12 and therefore the load current of the switching regulator increases,
The triangular wave voltage from the integrator circuit becomes smaller and the comparator COM
The pulse width of the output will be reduced.

Therefore, in any case of overcurrent or overvoltage to the load of the switching regulator, the peak value of the triangular wave voltage from the integrating circuit in the pulse width conversion circuit 11 is exchanged, thereby changing the pulse width of the pulse output supplied to the drive circuit. It's up to you to decide.

Even if the outputs of the error voltage amplifier 10 and the overcurrent detection amplifier 12 contain ripple components and ripple components, they are smoothed and reduced by selecting the resistors R1 and R2 of the integrating circuit and the capacitor C.

Furthermore, even if the triangular wave voltage from the integrating circuit contains fluctuations due to pulsation and ripple components, as is clear from FIG. 4, the output signal pulse of the NAND gate NA is equal to the input signal from the comparator COM It is 1/2 of the pulse,
The amount of change is equivalent to being reduced by 1/2.

As described above, the switching regulator of the present invention operates to reduce the variation when the DC output voltage fluctuates, in other words, it can perform constant voltage control. For example, the pulse width of the output of the pulse width conversion circuit is changed in accordance with the overcurrent, and the circuit operates so as to reduce fluctuations in the load current. In other words, constant current control can be performed.

Furthermore, even if the outputs of the error voltage amplifier and overcurrent detection amplifier contain pulsating components and ripple components, the pulse width conversion circuit does not operate unstablely, so abnormal noises may not be generated from the switching regulator as in the conventional case. Stable operation is achieved without excessive current flowing or excessive voltage occurring.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a general switching regulator, FIG. 2 is a circuit configuration diagram showing a part of FIG. 1, FIG. 3 is a wiring diagram showing an example of a switching regulator according to the present invention, and FIG. The figure is a waveform diagram showing the operation of FIG. 3. 10...Error voltage amplifier, 11...Pulse width conversion circuit, 12...Overcurrent detection amplifier,
OAl, OA2...Differential amplifier, COM...
...Comparator.

Claims (1)

[Claims] 1. A means for converting DC voltage into AC voltage controlled by pulses, a circuit for converting the AC voltage produced by the means into DC voltage, and generating an error voltage by comparing the output voltage of the circuit with a reference voltage. an error voltage amplifier, an overcurrent detection amplifier that detects an overcurrent flowing through the circuit and generates an overcurrent signal voltage, and a pulse width conversion circuit that generates a pulse according to the error voltage and the overcurrent signal voltage; In the switching regulator, the switching regulator includes a drive circuit that operates the conversion means by inputting a pulse, and the pulse width conversion circuit is provided with an integral circuit, and the error voltage and the overcurrent signal voltage are supplied to the integration circuit. A switching regulator, characterized in that the switching regulator is configured to control the pulse width of the pulse generated from the pulse conversion circuit according to the peak value of the output voltage from the integration circuit.