RU25231U1 - WIDTH-PULSE MODULATOR - Google Patents

Abstract

A pulse-width modulator containing a power source, a control element, the first output of which is connected to the first output of the power source, and the second output to the second output of the resistor current sensor and the first output of the limiting resistor, the second output of which is connected to the second output of the power source, the current source controlled circuit, the first and second conclusions of which are connected respectively with the first and second terminals of the resistor current sensor, a logic chip based on complementary MOS transistors (CMO microcircuit), containing more than two inverters, the first power output of which is connected to the first output of the power source, and the second power output to the second output of the power source, the output of the first inverter is connected to the input of the second inverter, the output of which is the output of a pulse-width modulator, frequency setting a capacitor connected between the input of the first inverter and the output of the second inverter, a frequency-setting resistor connected between the input and output of the first inverter, a diode whose anode is connected to the input of the first in rotor, and the cathode to the output of the third inverter, characterized in that a second resistor and a diode are inserted into it, the cathode of which is connected to the output of the pulse-width modulator, and the anode is connected to the input of the third inverter and through the second resistor to the first output of the current resistor sensor .

Description

Pulse Width Modulator.

The utility model relates to electrical engineering and can be used in the construction of control devices for switching power supplies.

Known pulse-width modulator (PWM), containing a linearly varying voltage generator, a feedback signal amplifier, a current protection comparator and a pulse-width modulated signal comparator 1, 2. PWM is used in the construction of control devices for switching power supplies to generate power switch control signals.

The disadvantages of this technical solution include its implementation on analog functional units (amplifiers, comparators), which, regardless of the operating mode, continuously consume current. As a result, the entire PWM node consumes a relatively large current (tens of milliamps). This reduces the overall efficiency of the power source using the specified PWM, complicates it, forcing to introduce an additional low-voltage channel specifically for powering the PWM. If, in addition, the modulator operates at a high frequency (hundreds of kilohertz), the above-mentioned functional units are executed on bipolar transistors, which further increases energy consumption. When reducing the load at the output of the power source or idling, the voltage of the power channel of such a PWM decreases to values that impede the normal operation of the power source as a whole. These shortcomings narrow the functionality and scope of the considered technical solutions.

the power supply shown in 3. Its functional diagram is shown in FIG. 1. The pulse-width modulator contains a power source, a control element, the first output of which is connected to the first output of the power source, and the second output to the first output of the limiting resistor, the current source of the controlled circuit, the first and second conclusions of which are connected respectively to the first and second outputs resistor current sensor, a logic microcircuit based on complementary MOS transistors (hereinafter referred to as CMOS microcircuit), containing more than two inverters, the first power output of which is connected to the first output of the source power supply, and the second power output - with the second output of the power source, the output of the first inverter is connected to the input of the second inverter, the output of which is the output of the pulse width modulator, a frequency-setting capacitor connected between the input of the first inverter and the output of the second inverter, a frequency-setting resistor connected between the input and the output of the first inverter, the diode, the anode of which is connected to the input of the first inverter, and the cathode to the output of the third inverter, the input of which is connected to the first output of the resistor sensor eye, the second terminal of which is connected to a first terminal limiting resistor, a second terminal of which is connected to the second terminal of the power source.

Common features of the proposed technical solution and prototype are a power source, a regulating element, the first output of which is connected to the first output of the power source, and the second output to the second output of the resistor current sensor and the first output of the limiting resistor, the second output of which is connected to the second output of the power source , a current source of a controlled circuit, the first and second conclusions of which are connected respectively to the first and second terminals of the resistor current sensor, a CMOS chip containing more than two inverters, the first power output of which is connected to the first output of the power source, and the second output of power - to the second output of the power source, the output of the first inverter is connected to the input of the second

an inverter whose output is the output of a pulse-width modulator, a frequency-setting capacitor connected between the input of the first inverter and the output of the second inverter, a frequency-setting resistor connected between the input and output of the first inverter, a diode whose anode is connected to the input of the first inverter, and the cathode to the output third inverter.

At the first and second inverters, a square-wave driving oscillator was made, the initial pulse duration and pause of which is determined by the values of the frequency-setting resistor and capacitor. The timing diagram of the voltage at the output of the master oscillator, the output of which is the PWM output, is shown in FIG. 2a. The current source of the monitored circuit measures the instantaneous current value in the power switch circuit. The instantaneous voltage value across the resistor current sensor is proportional to the value of the indicated current and is shown in FIG. 26. During a single state at the PWM output, the power switch is open, the current in the controlled circuit increases, during the zero state at the PWM output, the power switch is closed and there is no current in the controlled circuit. The maximum current value in the monitored circuit 1max corresponds to the voltage on the resistor current sensor, which is equal to the threshold voltage of the inverters of the CMOS chip, which is 0.4 .. .0.5 of the supply voltage of the chip.

Since the input resistance of the CMOI inverter is extremely large (10 ... Ohms), the instantaneous voltage value at the input of the inverter FROM is equal to the sum of the voltage drop across the limiting resistor 3 (constant bias) and resistor current sensor 5 (pulse component):

When the resistance of the regulating element 2 changes during PWM operation, the constant displacement Uorp changes. The maximum voltage value at the input of the third inverter FROM UBX is equal to Unop.

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UBX from - Uorp + UpaT. Regulation occurs as follows. When turned on

first, the PWM generates pulses of maximum duration, and the voltage at the input of the third inverter FROM UBX from increases, remaining less than the threshold value Unop (pigv). There is no feedback signal. The resistance of the control element is extremely high. If, during the next working cycle, the Unop value specified above is reached, at the output of the third inverter, and after this and at the PWM output, the zero state will be forcedly set. The power switch will close, which will protect it from overcurrent. When the adjustable PWM parameter, for example, the output voltage of the switching power supply, reaches its nominal value, a feedback signal appears, the resistance of the control element decreases and the current flowing through it creates a constant bias Uorp on the limiting resistor. Since the total value of the voltage at the input of the third inverter during the regulation process does not exceed Unop, the amplitude of the pulse component of the voltage - the voltage drop at the resistor current sensor IRD should decrease. And this, in turn, can be achieved only by reducing the pulse duration at the output of the PWM. Thus, by varying the degree of conductivity of the regulatory element, it is possible to change the duration of the PWM output pulse within wide limits.

The disadvantages of the considered technical solution include an increase in the current consumed from the power source while reducing the duration of the PWM output pulse. This feature of the PWM under consideration is explained by the circuit of the output stage of all elements of the CMOS microcircuits - a complementary pair of field-effect transistors (p- and p-channel) 4. When the input voltage of the third inverter IZ approaches a threshold value, the p-channel transistor of the output stage goes into active mode . The R-channel transistor remains open and the state remains at the output of the third inverter

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logical unit. At the same time, a “through current” flows through them, wasting power on the power source uselessly and heating the microcircuit.

The technical task of the proposed utility model is to reduce the current consumed from the power source and expand the functionality of the PWM.

The stated technical problem is solved by the fact that a pulse-width modulator is proposed comprising a power source, a control element, the first output of which is connected to the first output of the power source, and the second output to the second output of the current resistor sensor and the first output of the limiting resistor, the second output of which is connected to the second terminal of the power source, the current source of the controlled circuit, the first and second terminals of which are connected respectively to the first and second terminals of the resistor current sensor, CMOS a circuit containing more than two inverters, the first power output of which is connected to the first output of the power source, and the second power output to the second output of the power source, the output of the first inverter is connected to the input of the second inverter, the output of which is the output of a pulse-width modulator, frequency-setting capacitor, connected between the input of the first inverter and the output of the second inverter, a frequency-setting resistor connected between the input and output of the first inverter, a diode whose anode is connected to the input of the first inverter ora, and the cathode - to the output of the third inverter, and in it entered the second resistor and the diode, the cathode of which is connected to the output of pulse-width modulator, and an anode connected to the input of the third inverter and through the second resistor - to a first terminal of the current sensor resistor.

The introduction of additional elements and new non-obvious connections into the devices made it possible to eliminate the increase in the PWM current consumed while decreasing the duration of the output pulse, which, in turn, expands its functionality.

The applicant did not find technical solutions that have similar characteristics with signs that distinguish the claimed solution from the prototype, and, therefore, the proposed technical solution has significant differences.

The proposed device is made of standard elements that are commercially available from industry. It is assembled by typical installation operations using standard equipment and does not require adjustment, which is especially important in serial production. Therefore, the proposed device meets the criterion of industrial applicability.

In FIG. 3 shows a functional diagram of the proposed PWM.

The proposed pulse-width modulator contains a power source 1, a regulating element 2, a limiting resistor 3, a current source of a controlled circuit 4, a resistor current sensor 5, a frequency-setting capacitor 6 and a resistor 7, a diode 8, and a CMOS chip 9 containing more than two I1 inverters - Un, second resistor 10 and diode 11.

In the proposed PWM, the first output of the microcircuit 9 is connected to the first terminals of the regulating element 2 and the power source 1, the second output of the microcircuit 9 is connected to the second terminals of the limiting resistor 3 and the power source 1. The second terminal of the regulating element 2 is connected to the first terminal of the limiting resistor 3 and the second terminals of the current source of the controlled circuit 4 and the resistor current sensor 5, the first conclusions of which are connected to the input of the third inverter FROM and the anode of the second diode 11 through the second resistor 10. The cathode is second the first diode 11 is connected to the output of the second inverter I2. The output of the third inverter FROM is connected to the cathode of the diode 8, the anode of which is connected to the input of the first inverter I1, the output of which is connected to the input of the second inverter I2, the output of which is the PWM output. Frequency-setting capacitor 6 is connected between the input of the first inverter I1 and the output

second inverter I2. Frequency-setting resistor 7 is connected between the input and output of the first inverter I1.

As a regulatory element 2, as in the prototype, some element can be used that changes its resistance, for example, a phototransistor or optocoupler photodiode, magnetodod, etc. The current source of the controlled circuit 4 can be, for example, a current transformer, primary whose winding is included in the protected power circuit. Unused PWM circuits, the inverters of the microcircuit can be connected in parallel with the second inverter to power the PWM output (not shown in Fig. 3).

The work of the proposed PWM in the absence of feedback is the same as that of the prototype (Fig. 4). When the PWM is turned on, there is no feedback signal, the regulating element 2 is closed, the voltage at the limiting resistor 3 is almost 0. And the PWM output produces rectangular pulses of maximum duration, as in the prototype (Fig. 4a). A timing diagram of the current of the monitored circuit (or voltage across the resistor current sensor 5) is shown in FIG. The appearance and increase of the feedback signal entails an increase in the constant bias Uorp to values close to Unop (Fig. 4c), and a corresponding decrease in the duration of the PWM output pulse. This process, as well as the prototype, is accompanied by an increase in the current consumed from the power source. However, unlike the prototype, in the proposed PWM during the zero state, a logic zero voltage is applied to the input of the third inverter FROM the second diode 11 through the second diode 11, shifted by the voltage drop across the open diode 11 UOTKP D- This circumstance completely eliminates the "through current the third inverter FROM during the zero state at the PWM output, which reduces the total current consumption of the device. During a single state at the output of the PWM, the second diode 11 is closed and does not affect the operation of the latter. The second resistor 10 limits the maximum current value

2 2 through the regulating element 2. Its nominal value for PWM operation is practically not

affects, because the inverter of the CMOS chip has an extremely high input impedance 4. The remaining parameters of the proposed PWM in comparison with the prototype remain unchanged.

In the manufactured PWM sample, the current consumed from the power source at the minimum duration of the output pulse (about 0.5 microseconds) was half that of the prototype. This circumstance allows us to expand the scope of the proposed PWM in the direction of micropower pulse converters, which expands its functionality.

Sources used when writing an application.

1. Integrated microcircuits: Microcircuits for switching power supplies and their application. - M. DODEKA, 1997, 224 p. - ISSN-587835-0010-6. from. 38.

2. Integrated circuits: Integrated circuits for switching power supplies and their application. - M. DODEKA, 1997, 224 p. - ISSN-587835-0010-6. from. 87.

3.JV221097 certificate for utility model.

4. Zeldin E. A. Digital integrated circuits in information-measuring equipment. - L .: Energoatomizdat. Leningrad Department, 1986.- p. 65.

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Claims (1)

A pulse-width modulator containing a power source, a control element, the first output of which is connected to the first output of the power source, and the second output to the second output of the resistor current sensor and the first output of the limiting resistor, the second output of which is connected to the second output of the power source, the current source controlled circuit, the first and second conclusions of which are connected respectively with the first and second terminals of the resistor current sensor, a logic chip based on complementary MOS transistors (CMO microcircuit), containing more than two inverters, the first power output of which is connected to the first output of the power source, and the second power output to the second output of the power source, the output of the first inverter is connected to the input of the second inverter, the output of which is the output of a pulse-width modulator, frequency setting a capacitor connected between the input of the first inverter and the output of the second inverter, a frequency-setting resistor connected between the input and output of the first inverter, a diode whose anode is connected to the input of the first in rotor, and the cathode to the output of the third inverter, characterized in that a second resistor and a diode are inserted into it, the cathode of which is connected to the output of the pulse-width modulator, and the anode is connected to the input of the third inverter and through the second resistor to the first output of the current resistor sensor .