An isolated power supply circuit based on a self-excited push-pull circuit

Abstract

The present invention provides an isolated power supply circuit based on a self-excited push-pull circuit, which includes a first linear voltage regulator circuit, a second linear voltage regulator circuit and a self-excited push-pull circuit. The first linear voltage regulator circuit includes a resistor R3, a MOS transistor Q1, a diode Z1 and a capacitor C4. The pin 1 of the MOS transistor Q1 is connected to the resistor R3, the pin 3 of the MOS transistor Q1 is connected to the pin 1 of the diode Z1, one end of the capacitor C4 is connected to the resistor R3, and the other end is connected to the pin 2 of the diode Z1. This circuit can stably and continuously provide a stable voltage to ensure that the module remains in a no-output state and does not enter the hiccup mode, avoiding the problem of repeated switching on and off of the subsequent stage of the module, and increasing the safety of the entire system.

Description

Technical Field

[0001] The present invention relates to the field of circuit technologies, and particularly to an isolated power supply circuit based on a self-excited push-pull circuit. Background Art

[0002] At present, the functions of switching power supply products are constantly improving, and the secondary side prohibition function has appeared in the electrical performance requirements of isolated DC / DC converters. The secondary side prohibition function requires the product output terminal to provide an enabling function. When the secondary side prohibition terminal is connected to the output ground, the module is required to enter a low-power state and maintain no output without entering the hiccup mode until the prohibition is restored. In order to ensure that the module always maintains no output, the secondary side feedback operational amplifier circuit requires an independent power supply system. The module power supply is gradually developing towards miniaturization, so a simple and small-sized independent auxiliary power supply is very necessary. Summary of the Invention

[0003] In order to solve the above problems, the present invention proposes an isolated power supply circuit based on a self-excited push-pull circuit.

[0004] The present invention is realized through the following technical solutions:

[0005] The present invention proposes an isolated power supply circuit based on a self-excited push-pull circuit. The isolated power supply circuit based on a self-excited push-pull circuit includes a first linear voltage regulator circuit, a second linear voltage regulator circuit, and a self-excited push-pull circuit. The first linear voltage regulator circuit includes a resistor R3, a MOS transistor Q1, a diode Z1, and a capacitor C4. The pin 1 of the MOS transistor Q1 is connected to the resistor R3. The pin 3 of the MOS transistor Q1 is connected to the pin 1 of the diode Z1. One end of the capacitor C4 is connected to the resistor R3, and the other end is connected to the pin 2 of the diode Z1.

[0006] Further, the second linear voltage regulator circuit includes a resistor R4, a MOS transistor Q3, a diode Z2, a capacitor C6, and a capacitor C7. The pin 1 of the MOS transistor Q3 is connected to the resistor R4. One end of the diode Z2 is connected to the pin 3 of the MOS transistor Q3, and the other end is connected to the capacitor C7. The capacitor C6 is connected to the resistor R4. The pin 2 of the MOS transistor Q3 is connected to the capacitor C7.

[0007] Further, the self-excited push-pull circuit includes a MOS transistor Q2, a MOS transistor Q4, a capacitor C2, a resistor R1, and a resistor R5. The pin 3 of the MOS transistor Q2 is connected to the resistor R1. The pin 3 of the MOS transistor Q4 is connected to the resistor R5. One end of the capacitor C2 is connected to the pin 1 of the MOS transistor Q2, and the other end is connected to the pin 3 of the MOS transistor Q4.

[0008] Further, the self-excited push-pull circuit includes a transformer T1, which includes an Np1 winding, an Np2 winding, an Nb1 winding, an Nb2 winding, an Ns1 winding, and an Ns2 winding. The Np1 winding, the Np2 winding, the Nb1 winding, and the Nb2 winding are arranged on one side, and the Ns1 winding and the Ns2 winding are arranged on one side.

[0009] Further, the self-excited push-pull circuit includes a resistor R2, a diode D1, a diode D2, and a capacitor C3. The pin 1 of the transformer T1 is connected to the pin 1 of the MOS transistor Q2. The pin 2 of the transformer T1 is connected to the resistor R2. The pin 3 of the transformer T1 is connected to the pin 1 of the MOS transistor Q4. The pin 4 of the transformer T1 is connected to the resistor R5. The pin 5 of the transformer is connected to the resistor R2. The pin 6 of the transformer T1 is connected to the resistor R1. The pin 7 of the transformer T1 is connected to the diode D1. The pin 8 of the transformer T1 is connected to the capacitor C3. The pin 9 of the transformer T1 is connected to the diode D2.

[0010] Advantages of the present invention:

[0011] The isolated power supply circuit based on the self-excited push-pull circuit proposed by the present invention obtains a high-precision isolated auxiliary power supply with a certain load-carrying capacity by adding a self-excited push-pull circuit and two linear voltage regulator circuits. When the secondary side of the module is prohibited, the circuit can stably and continuously provide a stable voltage to ensure that the module remains in a no-output state and does not enter hiccupping, avoiding the problem of repeated switching on and off of the subsequent stage of the module, and increasing the safety of the entire system. Description of the Drawings

[0012] Figure 1 It is a circuit diagram of the isolated power supply circuit based on the self-excited push-pull circuit of the present invention. Detailed Embodiments

[0013] In order to more clearly and completely illustrate the technical solution of the present invention, the present invention will be further described below with reference to the drawings.

[0014] Please refer to Figure 1, the present invention provides an isolated power supply circuit based on a self-excited push-pull circuit. The isolated power supply circuit based on the self-excited push-pull circuit includes a first linear voltage regulator circuit, a second linear voltage regulator circuit, and a self-excited push-pull circuit. The first linear voltage regulator circuit includes a resistor R3, a MOS transistor Q1, a diode Z1, and a capacitor C4. The pin 1 of the MOS transistor Q1 is connected to the resistor R3, the pin 3 of the MOS transistor Q1 is connected to the pin 1 of the diode Z1, one end of the capacitor C4 is connected to the resistor R3, and the other end is connected to the pin 2 of the diode Z1. The second linear voltage regulator circuit includes a resistor R4, a MOS transistor Q3, a diode Z2, a capacitor C6, and a capacitor C7. The pin 1 of the MOS transistor Q3 is connected to the resistor R4, one end of the diode Z2 is connected to the pin 3 of the MOS transistor Q3, and the other end is connected to the capacitor C7. The capacitor C6 is connected to the resistor R4, and the pin 2 of the MOS transistor Q3 is connected to the capacitor C7. The self-excited push-pull circuit includes a MOS transistor Q2, a MOS transistor Q4, a capacitor C2, a resistor R1, and a resistor R5. The pin 3 of the MOS transistor Q2 is connected to the resistor R1, the pin 3 of the MOS transistor Q4 is connected to the resistor R5, one end of the capacitor C2 is connected to the pin 1 of the MOS transistor Q2, and the other end is connected to the pin 3 of the MOS transistor Q4. The self-excited push-pull circuit includes a transformer T1. The transformer T1 includes an Np1 winding, an Np2 winding, an Nb1 winding, an Nb2 winding, an Ns1 winding, and an Ns2 winding. The Np1 winding, the Np2 winding, the Nb1 winding, and the Nb2 winding are arranged on one side, and the Ns1 winding and the Ns2 winding are arranged on one side. The self-excited push-pull circuit includes a resistor R2, a diode D1, a diode D2, and a capacitor C3. The pin 1 of the transformer T1 is connected to the pin 1 of the MOS transistor Q2, the pin 2 of the transformer T1 is connected to the resistor R2, the pin 3 of the transformer T1 is connected to the pin 1 of the MOS transistor Q4, the pin 4 of the transformer T1 is connected to the resistor R5, the pin 5 of the transformer is connected to the resistor R2, the pin 6 of the transformer T1 is connected to the resistor R1, the pin 7 of the transformer T1 is connected to the diode D1, the pin 8 of the transformer T1 is connected to the capacitor C3, and the pin 9 of the transformer T1 is connected to the diode D2.

[0015] In this embodiment, a linear voltage regulation is first performed on a wide range of input voltages. The resistor R3, capacitor C4, diode Z1, and MOS transistor Q1 form a first linear voltage regulation circuit. The regulated voltage is applied to the bases of two power switch MOS transistors Q2 and Q4 through two windings Nb1 and Nb2 of the power switch transformer T1 and resistors R1 and R5 respectively. The resistors R1 and R5 are drive resistors. Due to the incomplete symmetry of the circuit, one of the power switch transistors always turns on first. Assuming that the MOS transistor Q2 turns on first, then the primary current flows through Np1 to magnetize the magnetic core, and at the same time, induced electromotive forces are generated in other windings. The base of the MOS transistor Q4 in the Nb1 winding is at a negative potential and is reverse-biased and cut off, while the base of the MOS transistor Q2 in the Nb2 winding is at a positive potential, which increases the collector current of the MOS transistor Q2, and the MOS transistor Q2 enters a deep saturation state. At this time, the secondary diode D2 conducts, and the rectified and filtered DC voltage is obtained according to the turns ratio of the transformer T1. When the magnetic core of the transformer T1 reaches magnetic saturation, the change rate of the magnetic flux becomes smaller and approaches zero. The current flowing through Np1 decreases, and the induced electromotive force on the winding reverses. The power switch transistor MOS transistor Q2 turns off, and the MOS transistor Q4 turns on and enters a deep saturation state. At this time, the secondary diode D1 conducts. Similarly, when the magnetic core gradually approaches saturation, the change rate of the magnetic flux also gradually becomes smaller and approaches zero. The above process repeats, and there is always a stable DC voltage on the secondary side. The above is the working principle of the self-excited push-pull circuit. When high precision is required, an additional linear voltage regulation circuit is added. The second linear voltage regulation circuit consists of a resistor R4, a capacitor C6, a diode Z2, a MOS transistor Q3, and a capacitor C7. This circuit provides a stable DC voltage with independent and isolated characteristics.

[0016] Of course, the present invention may have many other embodiments. Based on this embodiment, other embodiments obtained by those of ordinary skill in the art without any creative work belong to the scope protected by the present invention.

Claims

1. An isolated power supply circuit based on a self-excited push-pull circuit, characterized in that, The isolated power supply circuit based on the self-excited push-pull circuit includes a first linear voltage regulator circuit, a second linear voltage regulator circuit, and a self-excited push-pull circuit. The first linear voltage regulator circuit includes a resistor R3, a MOS transistor Q1, a diode Z1, and a capacitor C4. The pin 1 of the MOS transistor Q1 is connected to the resistor R3. The pin 3 of the MOS transistor Q1 is connected to the pin 1 of the diode Z1. One end of the capacitor C4 is connected to the resistor R3, and the other end is connected to the pin 2 of the diode Z1. The second linear voltage regulator circuit includes a resistor R4, a MOS transistor Q3, a diode Z2, a capacitor C6, and a capacitor C7. The pin 1 of the MOS transistor Q3 is connected to the resistor R4. One end of the diode Z2 is connected to the pin 3 of the MOS transistor Q3, and the other end is connected to the capacitor C7. The capacitor C6 is connected to the resistor R4. The pin 2 of the MOS transistor Q3 is connected to the capacitor C7. The self-excited push-pull circuit includes a MOS transistor Q2, a MOS transistor Q4, a capacitor C2, a resistor R1, and a resistor R5. The pin 3 of the MOS transistor Q2 is connected to the resistor R1. The pin 3 of the MOS transistor Q4 is connected to the resistor R5. One end of the capacitor C2 is connected to the pin 1 of the MOS transistor Q2, and the other end is connected to the pin 3 of the MOS transistor Q4. The self-excited push-pull circuit includes a transformer T1. The transformer T1 includes an Np1 winding, an Np2 winding, an Nb1 winding, an Nb2 winding, an Ns1 winding, and an Ns2 winding. The Np1 winding, the Np2 winding, the Nb1 winding, and the Nb2 winding are arranged on one side, and the Ns1 winding and the Ns2 winding are arranged on one side.

2. The isolated power supply circuit based on a self-excited push-pull circuit according to claim 1, characterized in that, The self-excited push-pull circuit includes a resistor R2, a diode D1, a diode D2, and a capacitor C3. The pin 1 of the transformer T1 is connected to the pin 1 of the MOS transistor Q2. The pin 2 of the transformer T1 is connected to the resistor R2. The pin 3 of the transformer T1 is connected to the pin 1 of the MOS transistor Q4. The pin 4 of the transformer T1 is connected to the resistor R5. The pin 5 of the transformer T1 is connected to the resistor R2. The pin 6 of the transformer T1 is connected to the resistor R1. The pin 7 of the transformer T1 is connected to the diode D1. The pin 8 of the transformer T1 is connected to the capacitor C3. The pin 9 of the transformer T1 is connected to the diode D2.

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