This is a High Voltage and High Current Circuit.

Step 1 : Selection of $R_1$ & $R_2$

$$V_O = V_{REF}(1 + \frac{R_1}{R_2})$$ Assume $R_2$ = 10KΩ and $V_{REF}$ = 7.15V $$12 = 7.15 (1 + \frac{R_1}{10KΩ})$$ $$\boxed{R_1 = 6.78KΩ}$$

Step 2 : Selection of $R_3$

$$R_3 = R_1 || R_2$$ $$R_3 = 6.78K || 10K$$ $$\boxed{R_3 = 4.04KΩ}$$

Step 3 : Selection of $R_A$ & $R_B$

$$R_A = (\frac{∝}{1 - ∝})R_B.........(1)$$ $$∝ = \frac{0.7}{Regulated output}(\frac{I_{LMAX}}{I_{SC}} - 1) $$ Assume, $I_{SC}$ = 200mA $$∝ = \frac{0.7}{12}(\frac{1A}{200mA} - 1)$$ $$∝ = 0.233$$ Substitute value of α in equation (1) and Assume $R_B$ = 10KΩ $$R_A = (\frac{0.233}{1 - 0.233}) × 10KΩ$$ $$\boxed{R_A = 3.03KΩ}$$

Step 4 : Selection of RSC

$$R_{SC} = \frac{V_{SENSE}}{I_{SC}(1 - ∝)}$$ Assume $V_{SENSE}$ = 0.5V $$R_{SC} = \frac{0.5}{200m(1 - 0.233)}$$ $$\boxed{R_{SC} = 3.25Ω}$$

Step 5 : Selection of Q3

$$P_{DT3} = V_{CE3} × I_{C3}$$ $$P_{DT3} = (V_{in} - V_O) × I_{C3}$$ Let $V_{in}$ = 2$V_O$ = 2×12=24V $$P_{DT3} = (24 - 12) × 1$$ $$P_{DT3} = 12W$$

$$β = \frac{I_L}{I_B} = \frac{1A}{150mA}$$ Assume $I_B$ = 150mA β = 6.66

Select transistor whose $P_{DT3}$ ≥ 12W and β ≥ 6.66

Step 6 : Selection of $R_L$

$$R_L = \frac{V_O}{I_L}$$
$$R_L = \frac{12}{1}$$
$$\boxed{R_L = 12Ω}$$

Step 7 : Designed Circuit diagram