JPH0248897Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a switching regulator mounted on a portable device that has a pulse width modulator that lowers the lower limit of battery voltage at which regulation cannot be achieved and increases battery utilization efficiency.

Conventionally, there is a switching regulator mounted on a portable device that is constructed as shown in FIG.

In FIG. 1, 1 is a battery, 2 is a switching AC converter, 3 is an output filter, 4 is an output terminal,
5 is a pulse generator composed of an astable multivibrator, 6 is a pulse width modulator composed of a monostable multivibrator, and 7 is an error amplifier.

The operation will be explained with reference to FIGS. 1 and 3. battery 1
The voltage is supplied to the switching transistor of the switching AC converter 2, and a control pulse is supplied from the pulse width modulator 6 to the switching transistor to turn it on and off. An AC output is taken out by turning on and off the switching transistor, this is rectified by an output filter 3, and a DC output is taken out to a terminal 4. At this time, the voltage at the terminal 4 is detected by the error amplifier 7, this detected voltage is compared with the reference voltage, and the difference voltage is supplied to the pulse width modulator 6 as a modulation input, and from the pulse generator 5 as shown in FIG. A pulse indicated by A is supplied to the pulse width modulator 6 as a trigger. The pulse width modulator 6 generates a pulse based on the rising edge of this input pulse. In the pulse width modulator 6, when the differential voltage is zero, the "H" level period of the pulse shown in FIG. 3B is set to be slightly narrower than the pulse period of the pulse generator 5 shown in FIG. 3A. , the pulse width is varied by changing the "H" level period of the pulse shown in FIG.・The output voltage is kept constant by controlling the off time and repeating high-speed rises and low-falls. For example, as the input battery voltage decreases, the waveform of the output pulse from the pulse width modulator 6 changes from C to D to E to F as shown in FIG. As the voltage increases, at the limit point of the battery voltage where regulation is no longer possible, the waveform of the output pulse of the pulse width modulator 6 becomes the waveform shown in FIG. 3G. However, at the limit point of the battery voltage where regulation is no longer possible, if the pulse width of the pulse width modulator 6 exceeds the period of the pulse of the pulse generator 5 shown in FIG. Since it is at the "L" level for one period as shown by H, the "L" level period of the pulse of the pulse width modulator 6 cannot be extremely shortened, and the limit is as shown in FIG. 3F. In such a switching regulator, pulses from the pulse width modulator 6 are not forcibly output during the "L" level period shown by H in FIG. 3, so even though voltage can be supplied from the battery, However, there is a drawback that regulation cannot be maintained.

The present invention aims to eliminate the above-mentioned drawbacks, obtain stable output until the battery voltage approaches the output voltage, and improve the effectiveness of battery utilization.

Embodiments of the present invention will be described below with reference to FIGS. 2 and 4. Components that are the same as those in FIG. 1 are given the same reference numerals, and their description will be omitted.

In FIG. 2, the voltage at terminal 4 is applied to error amplifier 7.
The voltage is compared with the reference voltage, and the difference voltage is detected by the monostable multivibrator 6.
At the same time, the pulse shown in FIG. 4I is inverted by the inverter 8 from the astable multivibrator 5, and the pulse shown in FIG. 4J is supplied.
This pulse causes a monostable multivibrator 6
, and set a pulse waveform that generates a pulse according to the rising edge of the input pulse, as shown in FIG. This pulse waveform is set so that when the differential voltage is zero, the "H" level becomes the "L" level during the "H" level period of the pulse of the astable multivibrator 5. The above error amplifier 7
The monostable multivibrator 6 outputs a pulse whose waveform changes according to the voltage difference between
The output is supplied to the OR circuit 9, is ORed with the pulse from the astable multivibrator 5, and the output is supplied to the switching transistor, which controls the on/off time and repeatedly repeats excessively high and excessively low pulses for output. Keeps the voltage constant.

For example, as the input battery voltage decreases, the output pulse of the monostable multivibrator 6 changes to L as shown in FIG.
→N→P, this output pulse is ORed with the output pulse of the astable multivibrator 5, and the pulse width changes as M→O→Q as shown in FIG. Therefore, at the lower limit of the battery voltage at which regulation is no longer possible, the control pulse of the switching transistor can be kept at the "H" level over the entire period, as shown in FIG. 4Q.

As mentioned above, the present invention converts battery voltage into high-frequency pulses through a switching element whose switching is controlled by control pulses from a pulse width modulator, and obtains a DC output voltage through an output filter. At the same time, fluctuations in the DC output voltage are detected by an error amplifier, and the control pulse, which is the output of the pulse width modulator to which the output pulse of the pulse generator is input, is controlled by the output of the error amplifier. In a switching regulator that eliminates fluctuations in output voltage, an OR circuit and an inverter are added, the output pulses of the pulse generator are applied to the OR circuit and the inverter, and the output of the inverter is applied to the pulse width modulator. In addition, by applying the output of the pulse width modulator to the OR circuit and controlling the switching element by the output of the OR circuit, the above-mentioned voltage is controlled over the entire cycle at the lower limit of the battery voltage at which regulation is no longer possible. Since the switching element can be turned on, even if the battery voltage is low, unlike conventional switching regulators, there is no downtime in controlling the switching element of the switching AC converter, so the battery voltage can be close to the voltage that can be output. It is possible to obtain stable output up to 100%, increasing battery usage efficiency.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional switching regulator, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a waveform diagram of Fig. 1, and Fig. 4 is a waveform diagram of Fig. 2. It is a diagram. 1: Battery, 2: Switching AC converter, 3:
Output filter, 4: Output terminal, 5: Pulse generator, 6: Pulse width modulator, 7: Error amplifier, 8:
Inverter, 9: OR circuit.

Claims (1)

[Scope of utility model registration request] The battery voltage is converted into a high-frequency pulse through a switching element whose switching is controlled by a control pulse from a pulse width modulator that generates a pulse according to the rising edge of an input pulse, and a DC output voltage is obtained through an output filter. At the same time, fluctuations in the DC output voltage are detected by an error amplifier, and the control pulse, which is the output of the pulse width modulator to which the output pulse of the pulse generator is input, is controlled by the output of the error amplifier. In the switching regulator that eliminates fluctuations in the DC output voltage, an OR circuit and an inverter are added, the output pulses of the pulse generator are applied to the OR circuit and the inverter, and the output of the inverter is modulated in pulse width. 1. A switching regulator, wherein the output of the pulse width modulator is added to the OR circuit, and the switching element is controlled by the output of the OR circuit.