A power supply circuit based on ucc1800 chip

Abstract

The application provides a power supply circuit based on a UCC1800 chip, which comprises a back difference circuit and an under-voltage protection circuit, the back difference circuit is electrically connected with a reference voltage end of the UCC1800 chip, the back difference circuit is electrically connected with the under-voltage protection circuit, an opening voltage input end of the power supply circuit based on the UCC1800 chip is electrically connected on the back difference circuit, and a power supply voltage input end of the power supply circuit based on the UCC1800 chip is electrically connected on the under-voltage protection circuit; the power supply circuit based on the UCC1800 chip enables the UCC1800 chip to have the back difference and under-voltage protection functions, and solves the problem of oscillation at a starting point in a slow power-on and power-off process when the UCC1800 chip is applied to a product.

Description

Technical Field

[0001] The present invention relates to the technical field of chip power supply circuits, and in particular to a power supply circuit based on a UCC1800 chip. Background Art

[0002] The existing UCC1800 chip lacks an undervoltage protection function. Its turn-on threshold is 7.2V, its turn-off threshold is 6.9V, and its own hysteresis is only 0.3V. When the UCC1800 chip is used in a product, the slow power-up and power-down process occurs near the product's startup point. Since product startup increases the input current, the voltage at the product input will decrease due to the line voltage drop. When the amplitude of the decrease is sufficient to shut down the UCC1800 chip, the product will repeatedly switch on and off near the startup point, causing oscillation. Products using the UCC1800 chip will experience the problem of oscillating back and forth at the startup point during the slow power-up and power-down process. Therefore, it is necessary to design a power supply circuit with hysteresis and undervoltage functions to solve this problem. Summary of the Invention

[0003] In order to solve the above problems, the present invention proposes a power supply circuit based on the UCC1800 chip.

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

[0005] The present invention proposes a power supply circuit based on the UCC1800 chip, including a hysteresis circuit and an undervoltage protection circuit. The hysteresis circuit is electrically connected to the reference voltage end of the UCC1800 chip, and the hysteresis circuit is electrically connected to the undervoltage protection circuit. The start-up voltage input end of the power supply circuit based on the UCC1800 chip is electrically connected to the hysteresis circuit, and the power supply voltage input end of the power supply circuit based on the UCC1800 chip is electrically connected to the undervoltage protection circuit.

[0006] Furthermore, the hysteresis circuit includes a resistor R1, a resistor R2, a resistor R3, an NPN transistor Q1, and a PNP transistor Q2, one end of the resistor R1 is electrically connected to the reference voltage end of the UCC1800 chip, the other end of the resistor R1 is electrically connected to the base of the NPN transistor Q1, the collector of the NPN transistor Q1 is electrically connected to the resistor R2, the emitter of the NPN transistor Q1 is electrically connected to the undervoltage protection circuit, the base of the PNP transistor Q2 is electrically connected to the resistor R2, the emitter of the PNP transistor Q2 is electrically connected to the start-up voltage input end of the power supply circuit based on the UCC1800 chip, and the collector of the PNP transistor Q2 is electrically connected to the resistor R3.

[0007] Further, the under-voltage protection circuit comprises a resistor R4, a resistor R5, a stabilizing tube D1, an NPN type triode Q3 and a capacitor C2, one end of the resistor R4 is electrically connected with the resistor R3, the other end of the resistor R4 is electrically connected with the emitter of the NPN type triode Q1, the stabilizing tube D1 and the capacitor C2 are electrically connected and grounded, the emitter of the NPN type triode Q3 is electrically connected with the capacitor C2, the collector of the NPN type triode Q3 is electrically connected with the resistor R5, the resistor R5 is electrically connected with the stabilizing tube D1, and the power supply voltage input end of the power supply circuit based on the UCC1800 chip is electrically connected between the capacitor C2 and the NPN type triode Q3.

[0008] Advantages of the present application:

[0009] The power supply circuit based on the UCC1800 chip has the under-voltage protection function through the simple circuit, and has good application performance. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 The circuit principle diagram of the power supply circuit based on the UCC1800 chip. DETAILED DESCRIPTION

[0011] In order to more clearly and completely illustrate the technical scheme of the present application, the present application will be further described below with reference to the drawings.

[0012] Please refer to Figure 1The application provides a power supply circuit based on a UCC1800 chip, which comprises a back difference circuit and an under-voltage protection circuit, the back difference circuit is electrically connected with a reference voltage end of the UCC1800 chip, the back difference circuit is electrically connected with the under-voltage protection circuit, an opening voltage input end of the power supply circuit based on the UCC1800 chip is electrically connected on the back difference circuit, and a power supply voltage input end of the power supply circuit based on the UCC1800 chip is electrically connected on the under-voltage protection circuit. The back difference circuit comprises a resistor R1, a resistor R2, a resistor R3, an NPN type triode Q1 and a PNP type triode Q2, one end of the resistor R1 is electrically connected with the reference voltage end of the UCC1800 chip, the other end of the resistor R1 is electrically connected with a base electrode of the NPN type triode Q1, a collector electrode of the NPN type triode Q1 is electrically connected with the resistor R2, an emitter electrode of the NPN type triode Q1 is electrically connected with the under-voltage protection circuit, a base electrode of the PNP type triode Q2 is electrically connected with the resistor R2, an emitter electrode of the PNP type triode Q2 is electrically connected with the opening voltage input end of the power supply circuit based on the UCC1800 chip, and a collector electrode of the PNP type triode Q2 is electrically connected with the resistor R3. The under-voltage protection circuit comprises a resistor R4, a resistor R5, a voltage stabilizing tube D1, an NPN type triode Q3 and a capacitor C2, one end of the resistor R4 is electrically connected with the resistor R3, the other end of the resistor R4 is electrically connected with the emitter electrode of the NPN type triode Q1, the voltage stabilizing tube D1 and the capacitor C2 are electrically connected and grounded, an emitter electrode of the NPN type triode Q3 is electrically connected with the capacitor C2, a collector electrode of the NPN type triode Q3 is electrically connected with the resistor R5, the resistor R5 is electrically connected with the voltage stabilizing tube D1, and the power supply voltage input end of the power supply circuit based on the UCC1800 chip is electrically connected between the capacitor C2 and the NPN type triode Q3.

[0013] In this embodiment, the startup voltage of the UCC1800 chip is 7.2V, and the base voltage VB of the NPN transistor Q3 is 7.9V, then the input turn-on voltage (VIN) is: VINon = VB + VB / R4 * R5. After the supply voltage (VCC) of the UCC1800 chip is higher than the startup point, the reference voltage (REF) of the UCC1800 chip will be established first. When the reference voltage (REF) is established, there will be a pulse width. When the supply voltage (VCC) reaches the startup point, the reference voltage (REF) is established, and the NPN transistor Q1 is fully turned on, so that the current passes through the EB junction of the PNP transistor Q2 and flows into the ground through the resistor R2. At this time, the PNP transistor Q2 is fully turned on, so that the resistor R3 is pulled up to VIN. At this time, the resistor R5 is connected in parallel with the resistor R3 to form an upper resistor, and the voltage is divided with the lower resistor R4 to form the B pole voltage of the NPN transistor Q3, that is, the input undervoltage turn-on threshold voltage. Increasing the resistance of resistor R3 can reduce hysteresis, while decreasing the resistance of resistor R3 can increase hysteresis. The NPN transistor Q1 and the PNP transistor Q2 are derating selected based on the input voltage to ensure that transient voltage does not break down the transistors. The resistors R1 and R2 ensure that the NPN transistor Q1 and the PNP transistor Q2 can enter a deep saturation region.

[0014] Of course, the present invention may have many other implementations. Based on this implementation, other implementations obtained by ordinary technicians in this field without any creative work are all within the scope of protection of the present invention.

Claims

1. A power supply circuit based on the UCC1800 chip, characterized in that: The power supply circuit based on the UCC1800 chip includes a hysteresis circuit and an undervoltage protection circuit. The hysteresis circuit is electrically connected to the reference voltage terminal of the UCC1800 chip, and the hysteresis circuit is electrically connected to the undervoltage protection circuit. The start-up voltage input terminal of the power supply circuit based on the UCC1800 chip is electrically connected to the hysteresis circuit, and the supply voltage input terminal of the power supply circuit based on the UCC1800 chip is electrically connected to the undervoltage protection circuit. The hysteresis circuit includes a resistor R1, a resistor R2, a resistor R3, an NPN transistor Q1, and a PNP transistor Q2, one end of the resistor R1 is electrically connected to the reference voltage terminal of the UCC1800 chip, the other end of the resistor R1 is electrically connected to the base of the NPN transistor Q1, the collector of the NPN transistor Q1 is electrically connected to one end of the resistor R2, the emitter of the NPN transistor Q1 is electrically connected to the undervoltage protection circuit, the base of the PNP transistor Q2 is electrically connected to the other end of the resistor R2, the emitter of the PNP transistor Q2 is electrically connected to the start-up voltage input terminal of the power supply circuit based on the UCC1800 chip, and the collector of the PNP transistor Q2 is electrically connected to one end of the resistor R3; The undervoltage protection circuit includes a resistor R4, a resistor R5, a voltage regulator D1, an NPN transistor Q3, and a capacitor C2. One end of the resistor R4 is electrically connected to the other end of the resistor R3, the other end of the resistor R4 is electrically connected to the emitter of the NPN transistor Q1 and is grounded, one end of the voltage regulator D1 and one end of the capacitor C2 are electrically connected and both are grounded, the emitter of the NPN transistor Q3 is electrically connected to the other end of the capacitor C2, the collector of the NPN transistor Q3 is electrically connected to one end of the resistor R5, the base of the NPN transistor Q3 is electrically connected to the other end of R5, the base of the NPN transistor Q3 is also electrically connected to the other end of R3, the other end of the resistor R5 is electrically connected to the other end of the voltage regulator D1, and the power supply voltage input end of the power supply circuit based on the UCC1800 chip is electrically connected between the capacitor C2 and the NPN transistor Q3.

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