import itertools

# 电阻备选值
resistor_values = [100, 220, 470, 1000, 2000, 4700, 5100, 6800, 10000, 12000, 15000, 20000, 22000, 47000, 51000, 100000]

# 计算输出电压Vout
def calculate_vout(vfb, r1, r2):
    return vfb * (1 + r1 / r2)

# 计算误差百分比
def calculate_error(expected_vout, actual_vout):
    return ((actual_vout - expected_vout) / expected_vout) * 100

# 串联电阻可能性（最多2个电阻串联）
def possible_resistors(values):
    return [(r,) for r in values] + [(r1, r2) for r1, r2 in itertools.combinations(values, 2)]

# 将电阻值格式化为字符串
def format_resistor_value(value):
    if value >= 1000:
        return f"{value / 1000:.1f}kΩ"
    return f"{value}Ω"

# 计算电阻组合
def find_best_resistors(vfb, vout, tolerance=1.0, max_results=3):
    best_combinations = []
    
    # 获取所有可能的电阻组合
    r1_combinations = possible_resistors(resistor_values)
    r2_combinations = possible_resistors(resistor_values)

    for r1_combo in r1_combinations:
        for r2_combo in r2_combinations:
            # 计算组合电阻值
            r1_value = sum(r1_combo)
            r2_value = sum(r2_combo)
            
            # 计算实际输出电压
            actual_vout = calculate_vout(vfb, r1_value, r2_value)
            
            # 计算误差
            error = calculate_error(vout, actual_vout)
            
            # 检查误差是否在容差范围内
            if abs(error) <= tolerance:
                best_combinations.append({
                    'R1': r1_combo,
                    'R2': r2_combo,
                    'Actual_Vout': actual_vout,
                    'Error_Percentage': error
                })
    
    # 按误差绝对值排序，并返回最多max_results个组合
    best_combinations = sorted(best_combinations, key=lambda x: abs(x['Error_Percentage']))[:max_results]
    
    return best_combinations

# 命令行交互
def main():
    print("DCDC反馈电压分压电阻计算器")
    
    vfb = float(input("请输入反馈电压 Vfb: "))
    vout = float(input("请输入期望输出电压 Vout: "))
    tolerance = float(input("请输入误差容差百分比 (默认1%): ") or 1.0)
    max_results = int(input("请输入返回的最佳结果数量 (默认3组): ") or 3)

    # 计算最佳电阻值
    best_combinations = find_best_resistors(vfb, vout, tolerance, max_results)

    if not best_combinations:
        print("没有找到符合要求的电阻组合，请尝试增加容差范围。")
    else:
        print(f"{'组合':<5} {'R1':<30} {'R2':<30} {'输出电压 Vout':<20} {'误差':<10}")
        print("=" * 100)
        for i, combo in enumerate(best_combinations):
            r1 = " + ".join([format_resistor_value(r) for r in combo['R1']])
            r2 = " + ".join([format_resistor_value(r) for r in combo['R2']])
            actual_vout = combo['Actual_Vout']
            error = combo['Error_Percentage']
            print(f"{i+1:<5} {r1:<30} {r2:<30} {actual_vout:<20.4f} {error:<10.2f}%")

    input("按Enter键退出...")

if __name__ == "__main__":
    main()