SLVAEV1 April 2022 TPS61041-Q1

2 Proposed Circuit Principle

Proposed Circuit Principle

Figure 2-1 shows the schematic of a boost converter using the TPS61041-Q1. Because the TPS61041-Q1 recommended input voltage maximum value is 6 V, the device VIN and GND pin cannot be connected to 12-V car battery directly. A level-shift circuit composed of D3, D2, and Q1 pulls up the IC GND pin voltage potential.

Figure 2-1 Proposed Schematic

D3 is a Zener diode that clamps the PNP transistor Q1 base voltage V_A to:

Equation 1.

V_{A} = V_{i n} - V_{Z}

The PNP transistor Q1 turns on, IC_GND voltage follows the calculation in Equation 2:

Equation 2.

V_{I C_G N D} = V_{A} + V_{B E}

In this application, a 6-V Zener diode is selected for D3. So, the TPS61041 VIN pin to GND pin voltage is clamped to below 6 V to protect the IC. Set the TPS61041 output voltage to 10 V higher than V_in as in
Equation 3:

Equation 3.

V_{O U T} = V_{I C_G N D} + V_{r e f} \times (1 + \frac{R_{1}}{R_{2}}) = V_{i n} - V_{Z} + V_{r e f} \times (1 + \frac{R_{1}}{R_{2}})

Where Vref is 1.233 V.

Set R₁ at 1.87 MΩ and R₂ at 167 kΩ. Assume the PNP transistor VBE is 0.3 V, the V_OUT – V_in equals
9.63 V.