JPH04108215A - Booster circuit - Google Patents

Abstract

PURPOSE:To increase a boosting speed by providing a MOSFET whose source connects to an output terminal of a boosting circuit and whose drain connects to a power terminal to the boosting circuit and connecting its gate to an output terminal of a differentiating circuit differentiating a boosting signal. CONSTITUTION:When a level of a boosting signal changes from L to H, an input voltage Vb of a differentiating circuit (a) changes from L to H, a capacitor C3 of the differentiating circuit (a) is charged accordingly, the voltage drives a gate of a MOSFET T1, and the MOSFET T1 is turned on untill the discharge of the capacitor C3 is finished, The discharge time is controlled to be less than a TD1(ON), a back Sate of the MOSFET T1 is connected to GND, then an output voltage VG1 of the boosting circuit rises steeply up to VCC-VT1, where VT1 is an ON voltage of the MOSFET T1 and boosted to the voltage VCC-VT1 or over, and the flowing to a power supply is prevented because the MOSFET T1 is turned off. Thus, the saturation time TR1(ON) untill the arrival to a saturation voltage VCP of the boosting circuit output is reduced. Thus, the boosting speed is quickened.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a booster circuit, and more particularly to a circuit that increases the boosting speed of a booster circuit.

Conventional Problem 1 Conventionally, as shown in FIG. 4, this type of booster circuit connects the output of an inverter composed of a diode D8 and a MOS FET T4-Ta to a diode D2. D.
is connected to one end which is the anode of the diode D2 connected in series, the other end which is the cathode of the diode D3 is used as the output terminal of the booster circuit, one end of the capacitor C1 is connected to the anode of the diode D2, and the cathode of the diode D2 and the diode D3 are One end of capacitor C2 is connected to the connection point of the anode, and the other end of capacitor C1 is connected to the first output φ of oscillator 6.
Connect the other end of the capacitor C2 to the second output φ that is in opposite phase to the first output φ of the oscillator, and connect the output terminal of the booster circuit to GND for discharging when the booster circuit turns from ON to OFF. M of
Connect OSFET T3, and connect the connection point between the cathode of diode D3 and the drain of MOSFET T3 via a gate resistor R, to the gate of MOSFET T2 whose drain source is connected between the power supply terminal and the output terminal OUT. The output of the inverter composed of Ta and T7 is connected to the aforementioned MO3FET T4. The circuit is connected to the input of the inverter made up of T5, and operates the boost circuit using the boost signal V.

As shown in FIG. 5, this booster circuit uses a booster signal V
s L=H change t, MO5FETT,,
The inverter MOSFET T, consisting of T7, is ONL, and accordingly the inverter MOSFET T, consisting of MOSFET T4tT5.

is turned on, the output VO3 of the booster circuit is as shown in Fig. 5 (B
), V on the path D□→T4→D2→D3.

After quickly rising to C3VF, the saturation voltage V slowly rises to be higher than the power supply voltage VCC due to the equivalent internal impedance of the oscillation circuit and the time constant of the capacitor C11C2. The operation was such that the voltage was increased to P.

Il　　　　　.

By the way, the above-mentioned conventional booster circuit includes a diode D1, a diode D2 . Since D3 is a series circuit, when the boost signal changes from L to H, the output VO3 of the boost circuit rises quickly up to Vcc 3Vp, but then reaches the saturation voltage V. The time TRQ (aVp, which is the sum of the forward voltages of diodes D and D3,
There was a drawback that the pressure increase rate was slow.

- The booster circuit of the present invention includes a MOSFET T whose source is connected to the output terminal of the booster circuit and whose drain is connected to the power supply terminal.
, and the gate is connected to the output terminal of a differentiating circuit that differentiates the boosted signal.

According to the above configuration, the output voltage of the differentiating circuit changes simultaneously with the change in the boost signal, and the voltage is applied to the MOSFET whose source is connected to the output terminal of the boost circuit and whose drain is connected to the power supply terminal.
'By driving the gate of TI, the output voltage of the booster circuit can be quickly raised to the power supply voltage without being affected by the forward voltage of the diode.

Below, this invention will be explained with reference to the drawings. 1st
The figure is a circuit diagram of an embodiment of the present invention, and FIG. 2 shows waveforms of various parts of the circuit shown in FIG. 1. In the figure, T, , T2.
T3. T5. T7. Ts is N-channel MO8FET1
T4-T6. Ts is P channel MOS FET
lD 0. D2-D3 are diodes, R1 is MO
S F E T T 2 gate resistance, ClIC2 is the capacitor, b is the oscillator, a is the capacitor C3 and resistor R
2, Vl is the boost signal, VIL is the output voltage of the differentiator a, Vb is the input voltage of the differentiator a, V
ar is the output voltage of the booster circuit.

Next, the operation of the above embodiment will be explained.

When the boost signal v1 changes to L-4-H as shown in Fig. 2 (2), the input voltage vb of the differentiating circuit a changes to L-H as shown in Fig. 2 (B), and the differentiating circuit changes accordingly. a capacitor C
3 is charged, the differential circuit output V, changes as shown in FIG. 2(C), and this voltage
MOSFET T.

remains ON until capacitor C3 finishes discharging.

This discharge time is T'nt+. By controlling the time to be less than 1 and connecting the back gate of MOSFET T+ to GND, the output voltage voI of the booster circuit is
If the ON voltage of SFET T is VTI, as shown in Figure 2 (CD), it rises steeply to Voo-Vd, and after being boosted to VCC-VTI or higher, the MOSFET
Since T is turned off, the flow into the power supply can be prevented.

Here, since vT□<3Vp and the boosting speed is constant, the output voltage of the booster circuit is V. 1 is VCC - saturation voltage v. When P, Vcp (Vcc Vt1) (V
cp (V cc 3 V p ), which is the saturation voltage V of the booster circuit output. Saturation time T until reaching p
RI+. N] is much shorter than the conventional TR2+ONI.

Note that in the case of negative logic input, the inverter composed of MOS FET To and T7 provided at the front stage of the differentiating circuit a may not be provided.

Disaster prevention 2 FIG. 3 is a circuit diagram of a second embodiment of the present invention. This embodiment is the same as the first embodiment except that the back gate of MOSFET T is connected to the 7-second input of the differentiating circuit a, so a description thereof will be omitted. In this example,
With the above configuration, the ON voltage V of MOSFET T1
T t becomes lower, and the pressure increase rate can be made even faster.

! Results As explained above, the present invention provides a booster circuit that is controlled by a booster signal and includes a diode, a capacitor, an oscillator, and an inverter, in which the source is connected to the output terminal of the booster circuit and the drain is connected to the power supply terminal. By providing a connected MOSFET and connecting the gate to the output terminal of the differentiating circuit that differentiates the boost signal, the output voltage of the boost circuit can be quickly raised to the power supply voltage without being affected by the forward voltage of the diode. This has the effect of shortening the saturation time of the output voltage of the booster circuit and increasing the boosting speed.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of Embodiment 1 of the present invention, Fig. 2 is a waveform diagram of each part of the circuit of Fig. 1, Fig. 3 is a circuit diagram of Embodiment 2 of this invention, and Fig. 4 is a circuit of the prior art. 5 are waveform diagrams of various parts of FIG. 4. a... Differential circuit, b... Oscillator, T1-T8... MOS F E T1C1-C3...
・Capacitor, D, ~D3...Diode, R□I R2...Resistor, VCC...Power supply voltage, OUT...Output terminal, ■F...Diode forward voltage, VI...Step up Signal, φ, φ...Oscillator output, TDHON)...Turn-on time, vctt Vc21 VO3...Booster circuit output voltage,
Vb...Differentiator circuit input voltage, ■,...Differentiator circuit output voltage, TRI(.N l t T R2F.,...Boost time, vcp...Saturation voltage, V1□...MOSFET T, threshold voltage.

Claims (1)

[Scope of Claims] In a booster circuit including a diode, a capacitor, an oscillator, and an inverter that are controlled by a booster signal, a MOSFET whose source is connected to the output terminal of the booster circuit and whose drain is connected to a power supply terminal is provided, and the booster circuit is controlled by a booster signal. A booster circuit characterized in that a gate is connected to the output terminal of a differentiating circuit that differentiates the voltage.