TIDUCF7 May   2022 TPSI3050 , TPSI3050-Q1 , TPSI3052 , TPSI3052-Q1

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 System Design Theory
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
    3. 2.3 Design Considerations
      1. 2.3.1 TPSI3050-Q1
      2. 2.3.2 AMC23C10
      3. 2.3.3 SN74HCS72 and TMUX1219
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
      3. 4.1.3 Altium Project
      4. 4.1.4 Assembly Drawings
        1. 4.1.4.1 Gerber Files
    2. 4.2 Documentation Support
    3. 4.3 Support Resources
    4. 4.4 Trademarks
  10. 5About the Author

1 System Description

Zero cross detection allows a circuit to detect when the load AC waveforms has reached the zero-voltage point. Switching ON when the AC source is at zero volts increases the system efficiency and reliability. If an AC source is switched ON while the source is on its peak voltage, it could result in high frequency switching noises, high inrush current spikes, and dangerous stress to the system. This reference design features a SSR implemented with the TPSI3050-Q1 isolated switch driver and back to back N-Channel MOSFETs. TPSI3050-Q1 generates a 10 V rail to drive the gate of the power FETs and a mid-rail supply of 5 V to power HV side circuitry needed for the zero-cross switching logic. The TPSI3050-Q1 offers 5 kVRMS reinforced isolation and AEC-Q100 qualification for automotive applications while the TPSI3050 offers 3 kVRMS basic isolation for industrial applications.

Figure 1-1 shows the operation of designs with and without zero-cross detection. When zero cross detection is not implemented, the load is immediately connected to the source when an enable signal is received. The load could be turned ON at any voltage level. The worst case scenario is when the source is at the maximum voltage condition and the load is connected. Inrush currents generated can damage sensitive circuits and EMI switching noises can propagate throughout the system. If a mechanical relay is used, switching at peak voltage can cause arcing or welding which could damage the relay as well as the system down stream. These challenges are eliminated using zero-cross switching SSR. This reference design uses the AMC23C10 isolated comparator to detect zero voltage crossing and sends a signal to the low voltage side. The signal changes from high to low at OUT2 output of the comparator. Then the falling edge is detected by SN74HCS72 flip-flop and the signal is latched so that TPSI3050-Q1 remains ON. In addition, the zero-cross switching logic uses a switch and a multiplexer to provide the user the ability to disconnect the load at any time.

Figure 1-1 Zero-Cross Switching