A TTL isolated control circuit
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-27
- Publication Date
- 2026-08-11
AI Technical Summary
在开关电源技术领域中，经常会遇到TTL电平控制开关电源的通断，非隔离的场合使用TTL集成电路是常见的，但是在实际应用中往往有很多逻辑控制需要隔离的，目前逻辑控制组要使用控制芯片来实现，需要配备外围电路，容易受到信号干扰，应用范围小
Smart Images
Figure CN224626643U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of integrated circuit technology, specifically a TTL isolation control circuit. Background Technology
[0002] TTL itself is a type of integrated circuit, containing logic gates, bipolar transistors, resistors, and diodes. It uses bipolar transistors to perform logic functions to provide switching functionality and has a wide range of applications. In the field of switching power supply technology, TTL level control of switching power supplies is frequently encountered. The use of TTL integrated circuits is common in non-isolated applications. However, in practical applications, many logic controls often require isolation. Currently, logic control groups are implemented using control chips, which require external circuitry, are susceptible to signal interference, and have a limited application range. Summary of the Invention
[0003] To solve the above-mentioned technical problems, this utility model provides a TTL isolation control circuit, which has a simple circuit structure, low cost, and strong versatility.
[0004] The technical solution is as follows: A TTL isolation control circuit, characterized in that it includes an optocoupler P1. The light source pin 1 of the optocoupler P1 is connected to one end of resistor R1, one end of capacitor C1, and ground. The other end of resistor R1 is connected to the cathode of diode D1. The anode of diode D1 is connected to the other end of capacitor C1 and serves as a TTL1 level input terminal. The light source pin 2 of the optocoupler P1 is connected to the collector of transistor Q1. The base of transistor Q1 is connected to one end of resistor R3 and one end of capacitor C3. The other end of resistor R3 is connected to one end of resistor R2 and one end of resistor R4. The other end of resistor R2 is connected to the cathode of diode D2. The anode of diode D2 is connected to one end of capacitor C2 and serves as a TTL2 level input terminal. The other ends of capacitor C1, resistor R4, capacitor C3, and the emitter of transistor Q1 are all grounded. The light receiver pin 3 of the optocoupler P1 is grounded, and pin 4 is the control terminal EN.
[0005] By adopting this utility model, the EN state of the control terminal is realized by using TTL1 and TTL2 levels. The optocoupler P1 plays a signal isolation role to prevent the TTL signal from being interfered with and causing the EN control terminal to malfunction. The circuit structure is simple, low in cost, and highly versatile. Attached Figure Description
[0006] Figure 1 This is the circuit schematic diagram of this utility model. Detailed Implementation
[0007] See Figure 1As shown, a TTL isolation control circuit includes an optocoupler P1. The light source pin 1 of the optocoupler P1 is connected to one end of resistor R1, one end of capacitor C1, and ground. The other end of resistor R1 is connected to the cathode of diode D1. The anode of diode D1 is connected to the other end of capacitor C1 and serves as a TTL1 level input. The light source pin 2 of the optocoupler P1 is connected to the collector of transistor Q1. The base of transistor Q1 is connected to one end of resistor R3 and one end of capacitor C3. The other end of resistor R3 is connected to one end of resistor R2 and one end of resistor R4. The other end of resistor R2 is connected to the cathode of diode D2. The anode of diode D2 is connected to one end of capacitor C2 and serves as a TTL2 level input. The other ends of capacitor C1, resistor R4, capacitor C3, and the emitter of transistor Q1 are all grounded. The receiver pin 3 of the optocoupler P1 is grounded, and pin 4 is the control terminal EN.
[0008] Typically, the TTL level is 5V. When TTL1 outputs 5V and TTL2 has no output, transistor Q1 is not conducting, and no current flows through the light source of optocoupler P1, so the control terminal EN remains unchanged. When TTL1 has no output and TTL2 outputs 5V, transistor Q1 conducts, but again, no current flows through the light source of optocoupler P1, and the control terminal EN remains unchanged. When both TTL1 and TTL2 output 5V, transistor Q1 conducts, and current flows through the light source of optocoupler P1. Through electro-optical-electro-electrical conversion, the photodetector of optocoupler P1 conducts, and the control terminal EN is pulled low, thus changing the state of the external controlled unit. Diodes D1 and D2 act as unidirectional conductors, capacitors C1, C2, and C3 act as filters, and optocoupler P1 also acts as a signal isolation device to prevent interference with the TTL signal from causing malfunctions in the control terminal EN.
Claims
1. A TTL isolation control circuit, characterized in that, It includes an optocoupler P1. The light source pin 1 of the optocoupler P1 is connected to one end of resistor R1, one end of capacitor C1, and ground. The other end of resistor R1 is connected to the cathode of diode D1. The anode of diode D1 is connected to the other end of capacitor C1 and serves as a TTL1 level input. The light source pin 2 of the optocoupler P1 is connected to the collector of transistor Q1. The base of transistor Q1 is connected to one end of resistor R3 and one end of capacitor C3. The other end of resistor R3 is connected to one end of resistor R2 and one end of resistor R4. The other end of resistor R2 is connected to the cathode of diode D2. The anode of diode D2 is connected to one end of capacitor C2 and serves as a TTL2 level input. The other ends of capacitor C1, resistor R4, capacitor C3, and the emitter of transistor Q1 are all grounded. The light receiver pin 3 of the optocoupler P1 is grounded, and pin 4 is the control terminal EN.